CI RCUIT

TECHNICAL FIELD

Examples of the present disclosure generally relate to electronic circuits and, in particular, to reconfiguration of single-band transmit and receive paths to multi-band transmit and receive paths in an integrated circuit.

BACKGROUND

Current remote radio head (RRH) architectures typically support single- band transmit and receive paths to each antenna. In order to reduce system cost, there is market pressure to concurrently transmit multiple bands through the same antenna ("multi-band" transmission and reception). Multi-band support is typically implemented using dedicated digital signal processor (DSP) circuitry within a given transmit/receive path. However, there are a myriad of single and multi-band deployment requirements. The use of dedicated DSP circuitry leads to a lack of flexibility and an increase in cost overhead when attempting to support all of the deployment requirements.

SUMMARY

Techniques for reconfiguration of single-band transmit and receive paths to multi-band transmit and receive paths in an integrated circuit (IC) are described. In an example, a transmitter includes first and second circuit stages and interface circuits. The first circuit stage is configured to generate modulated signals from baseband signals, each of the modulated signals comprising a digital signal having respective a carrier frequency of a plurality of carrier frequencies. The second circuit stage is configured to generate radio frequency (RF) energy to be radiated by one or more antennas. The interface circuits are coupled between the first circuit stage and the second circuit stage. The second circuit stage and the interface circuits are configurable to provide a first mode and a second mode. In the first mode, the second circuit stage provides a plurality of transmit paths and the interface circuits couple each of the modulated signals to a respective one of the plurality of transmit paths. In the second mode, the second circuit stage provides a first transmit path and the interface circuits couple a sum of at least two of the modulated signals to the first transmit path.

In another example, a receiver includes a first circuit stage, a second circuit stage, and interface circuits. The first circuit stage is configured to receive radio frequency (RF) energy from one or more antennas. The second circuit stage includes a plurality of demodulation paths each comprising a digital demodulator configured to process a respective frequency of a plurality of frequencies. The interface circuits are coupled between the first circuit stage and the second circuit stage. The first circuit stage and the interface circuits are configurable to provide a first mode and a second mode. In the first mode, the first circuit stage generates a plurality of digital signals from the RF energy and the interface circuits couple each of the plurality of digital signals to a respective one of the plurality of demodulation paths. In the second mode, the first circuit stage generates a first digital signal from the RF energy and the interface circuits couple the first digital signal to at least two of the plurality of demodulation paths.

These and other aspects may be understood with reference to the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features can be understood in detail, a more particular description, briefly summarized above, may be had by reference to example implementations, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical example implementations and are therefore not to be considered limiting of its scope.

Fig.1 is a block diagram depicting a communication system according to an example.

Fig. 2 is a block diagram depicting a transmitter according to an example.

Fig. 3 is a block diagram illustrating a configuration of the transmitter of Fig. 2 according to an example.

Fig. 4 is a block diagram illustrating another configuration of the transmitter of Fig. 2 according to an example. Fig. 5 is a block diagram depicting a receiver according to an example.

Fig. 6 is a block diagram illustrating a configuration of the receiver of Fig. 5 according to an example.

Fig. 7 is a block diagram illustrating another configuration of the receiver of Fig. 5 according to an example.

Fig. 9 is a flow diagram depicting a method of configuring a configurable single-band/multi-band transmitter according to an example.

Fig. 10 is a flow diagram depicting a method 1000 of configuring a configurable single-band/multi-band receiver according to an example.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements of one example may be beneficially

incorporated in other examples. DETAILED DESCRIPTION

Various features are described hereinafter with reference to the figures. It should be noted that the figures may or may not be drawn to scale and that the elements of similar structures or functions are represented by like reference numerals throughout the figures. It should be noted that the figures are only intended to facilitate the description of the features. They are not intended as an exhaustive description of the claimed invention or as a limitation on the scope of the claimed invention. In addition, an illustrated example need not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular example is not necessarily limited to that example and can be practiced in any other examples even if not so illustrated, or if not so explicitly described.

Fig.1 is a block diagram depicting a communication system 100 according to an example. The communication system 100 includes symbol generators 102, data generators 108, a transceiver 101 , and antennas 1 10. The

communication system 100 can also include a controller 1 12 configured to control the transceiver 101 . The symbol generators 102, the data generators 108, the controller 1 12, and the transceiver 101 can be part of an integrated circuit (IC) 150. The antennas 1 10 can be coupled to the IC 150 by external transmission lines (not shown). The transceiver 101 includes a configurable single-band/multi-band transmitter 104 (briefly referred to as "transmitter 104") and a configurable single-band/multi-band receiver 106 (briefly referred to as "receiver 106"). Inputs of the symbol generators 102 receive input data to be transmitted. Outputs of the symbol generators 102 are coupled to inputs of the transmitter 104. Outputs of the transmitter 104 are coupled to the antennas 1 10. Inputs of the receiver 106 are coupled to the antennas 1 10. Outputs of the receiver 106 are coupled to inputs of the data generator 108. Outputs of the data generator 108 provide output data. An output of the controller 1 12 is coupled to control inputs of the transmitter 104 and the receiver 106, respectively.

In operation, the symbol generators 102 generate baseband signals from the input data. The input data comprise data bits. The symbol generators 102 map the data bits of the input data into two-dimensional symbols in a modulation alphabet of a particular digital modulation scheme. Various digital modulation schemes can be employed. For example, a 16-level quadrature amplitude modulation (QAM) scheme includes an alphabet (also referred to as a

constellation) of 16 symbols, where each symbol represents four data bits of the input data. Each two-dimensional symbol is represented by an in-phase (I) coordinate and a quadrature-phase (Q) coordinate. For quadrature modulation schemes, such as QAM, quadrature phase shift keying (QPSK), and the like, the symbol generator 102 generates I and Q components for each symbol. For single-phase modulation schemes, such as amplitude shift keying (ASK), the symbol generator 102 generates I components for each symbol (the Q

components are zero). In general, the symbol generators 102 generate baseband signals, which can include I baseband signals having I symbol components or both I and Q baseband signals having both I and Q symbol components, respectively.

Each baseband signal is a digital signal. As used herein, a digital signal is a sequence of k-bit codes, where k is a positive integer greater than zero. For example, each code represents a value of an I or Q component of a symbol. The number of codes per unit interval is the code-rate (sample rate). A digital signal can also be conceptually viewed as a discrete time, discrete-amplitude signal, where the amplitude of the signal at each discrete time is selected from 2 ^k discrete values. The transmitter 104 generates one or more radio frequency (RF) analog signals in response to the baseband signals output by the symbol generators 102. An analog signal is a continuous-time, continuous-amplitude signal. The transmitter 104 includes a plurality of modulator paths 1 13 and is configurable to include one or more transmit paths 1 14. Each of the transmit paths 1 14 is coupled to an antenna 1 10. In a first mode ("single-band mode"), the transmitter 104 is configured to include a plurality of transmit paths 1 14. The modulator paths 1 13 generate modulated signals from the baseband signals, and each of the transmit paths 1 14 outputs an RF analog signal generated from a modulated signal and having a single RF frequency band. In single-band mode, the transmitter 104 outputs a plurality of RF analog signals each having a different RF frequency band for radiation by the antennas 1 10.

In a second mode ("multi-band mode"), the modulator paths 1 13 generate modulated signals from the baseband signals, and each of one or more transmit paths 1 14 receives a sum of at least two of the modulated signals. In multi-band mode, each transmit path 1 14 outputs an RF analog signal generated by combining multiple frequency bands of multiple modulated signals. The transmitter 104 outputs one or more RF analog signals for radiation by the antennas 1 10. The transmitter 104 can include a plurality of multi-band modes, as discussed further below. The mode of the transmitter 104 is selected by the controller 1 12.

The receiver 106 generates baseband signals from RF energy received by the antennas 1 10. The receiver 106 includes a plurality of demodulator paths 1 16 and is configurable to include one or more receive paths 1 15. Each of the receive paths 1 15 is coupled to an antenna 1 10. Each of the demodulator paths 1 16 demodulates a different carrier frequency. In a first mode ("single-band mode"), the receiver 106 is configured to include a plurality of receive paths 1 15. The receive paths 1 15 generate digital signals from the RF energy received by the antennas 1 10, and each demodulator path 1 16 outputs baseband signals generated from a respective one of the digital signals. In a second mode ("multi- band mode"), the receiver 106 is configured to include one or more receive paths 1 15. Each receive path 1 15 generates a digital signal from the RF energy received by an antenna 1 10. A digital signal generated by one receive path 1 15 is then coupled to at least two of the demodulator paths 1 16. Thus, multiple demodulator paths 1 16 share each receive path 1 15. The receiver 106 can include a plurality of multi-band modes, as discussed further below. The mode of the receiver 106 is selected by the controller 1 12.

The data generators 108 generate output data from baseband signals output by the receiver 106. The data generators 108 map symbols of the baseband signals to bits of the output data based on the modulation alphabet of the particular digital modulation scheme used to transmit the data. The data generators 108 performs the reverse process of the symbol generators 102.

The transmitter 104 enables two or more single-band transmit paths to be dynamically reconfigured to support multi-band transmission. Multi-band transmission is achieved by multiplexing and adding inputs to the transmit paths. The transmitter 104 does not require dedicated multi-band digital signal processor (DSP) circuitry to achieve multi-band support. Likewise, the receiver 106 enables two or more single-band receive paths to be dynamically

reconfigured to support multi-band reception. Multi-band reception is achieved by multiplexing outputs of the receive paths. The receiver 106 does not require dedicated DSP circuitry to achieve multi-band support. Thus, the transceiver 101 provides flexibility to support single-band or multi-band transmission and reception for multiple radio architectures with low overhead.

Fig. 2 is a block diagram depicting the transmitter 104 according to an example. The transmitter 104 includes a first circuit stage 250, interface circuits 206, and a second circuit stage 252. Inputs of the first circuit stage 250 receive baseband signals to be transmitted. Outputs of the first circuit stage 250 are coupled to inputs of the interface circuits 206. The outputs of the first circuit stage 250 provide modulated signals. In general, the modulated signals include digital carrier signals modulated by the baseband signals. Outputs of the interface circuits 206 are coupled to inputs of the second circuit stage 252. The interface circuits 206 selectively couple the modulated signals to the transmit paths 1 14 implemented by the second circuit stage 252. Outputs of the second circuit stage 252 are coupled to antennas 1 10. In operation, output(s) of the second circuit stage 252 provide RF analog signal(s) to be radiated by antenna(s) 1 10.

In an example, the first circuit stage 250 includes a plurality of

interpolators 203, digital modulators 202, and numerically controlled oscillators (NCOs) 204. Inputs of the interpolators 203 receive the baseband signals. Outputs of the interpolators 203 are coupled to inputs of the digital modulators 202. Local oscillator (LO) inputs of the digital modulators 202 are coupled to outputs of the NCOs 204. Outputs of the digital modulators 202 are coupled to inputs of the interface circuits 206. Each of the modulator paths 1 13 comprises one of the digital modulators 202. In the example of Fig. 2, the first circuit stage 250 includes N digital modulators 202i through 202N, where N is an integer greater than one. Thus, the transmitter 104 includes N modulator paths 1 13. The interpolators 203 include in-phase interpolators 203 through 203IN and quadrature interpolators 203Qi through 203QN. The interpolators 203 and 203Qi are coupled to the digital modulator 2021 and the interpolators 203I N and 203Q _N are coupled to the digital modulator 203 _N . The NCOs 204 include NCOs 204i through 204 _N . Each of the NCOs 204i through 204 _N is coupled to a respective one of the digital modulators 202i through 202N.

In operation, the interpolators 203 receive the baseband signals having a particular sample rate. The interpolators 203 interpolate the baseband signals to increase the sample rate for processing by the digital modulators 202. The digital modulators 202 mix the baseband signals with digital carrier signals generated by the NCOs 204. Interpolators 203 increase the sample rate of the baseband signals to match the sample rate of the digital carrier signals generated by the NCOs 204. In the example, the in-phase interpolators 203I interpolate the I baseband signals and the quadrature phase interpolators 203Q interpolate the Q baseband signals. Each NCO 204 generates a pair of digital carrier signals each comprising a discrete time, discrete-amplitude sinusoid having a particular carrier frequency. In various configurations, the carrier frequency can be an intermediate frequency (IF) frequency or an RF frequency. The pair of digital carrier signals are in quadrature with each other (e.g., 90 degrees out of phase).

The digital modulators 202 generate modulated signals from the baseband signals output by the interpolators 203 and the digital carrier signals output by the NCOs 204. In general, the digital modulators 202 modulate the digital carrier signals with the baseband signals to generate the modulated signals. The modulated signals each include a carrier frequency shifted from a baseband frequency (sample rate of the baseband signals). In one configuration, the carrier frequency of each of the modulated signals is an RF frequency. This supports a direct-RF transmitter architecture where the baseband signals directly modulate RF carriers. In such a configuration, the NCOs 204 output digital carrier signals having selected RF frequencies.

In another configuration, the carrier frequency of each of the modulated signals is an IF frequency. This supports IF to RF transmitter architectures where the baseband signals modulate I F carriers, and then the IF carriers are upconverted to RF carriers. In such a configuration, the NCOs 204 output digital carrier signals having selected I F frequencies.

In one configuration, each of the digital modulators 202 outputs one modulated signal via a single output. The modulated signal is a sum of an in- phase digital carrier signal modulated by an I baseband signal and a quadrature- phase digital carrier modulated by a Q baseband signal. In such case, both the amplitude and phase of the modulated signal are modulated by the pair of I and Q baseband signals. Of course, if the Q baseband signal is always zero (e.g., an in-phase modulation scheme, such as ASK, is employed), then the modulated signal is the in-phase digital carrier modulated by the I baseband signal. The carrier frequency can be either an IF frequency or an RF frequency.

In another configuration, each of the digital modulators 202 outputs two modulated signals via two outputs. That is, each of the digital modulators 202 includes I and Q outputs providing I and Q modulated signals. The I modulated signal comprises an I digital carrier signal modulated by an I baseband signal, and the Q modulated signal comprises a Q digital carrier signal modulate by a Q baseband signal. The carrier frequency is an IF frequency. In another configuration, the digital modulators 202 may be bypassed, allowing the interpolated I and Q baseband signals to be passed directly to the interface circuits 206. Thus, the transmitter 104 supports both real IF/RF and complex IF transmitter architectures. The configuration of the first circuit stage 250 can be controlled by the controller 1 12.

The second circuit stage 252 includes digital-to-analog converters (DACs)

208, filters 209, and power amplifiers (PAs) 214. In the present example, the second circuit stage 252 includes N DACs 208i through 208 _N , N filters 209i through 209 _N , and N PAs 214i through 214 _N . Inputs of the DACs 208 are coupled to outputs of the interface circuits 206. Outputs of the DACs 208 are coupled to inputs of the filters 209. Outputs of the filters 209 are coupled to inputs of the PAs 214. Outputs of the PAs 214 are coupled to the antennas 1 10. In some examples, the second circuit stage 252 also includes analog

modulator(s) 210, filter(s) 212, and PA(s) 216. Inputs of the analog modulator(s) 210 are coupled to outputs of filters 209. Output(s) of the analog modulator(s) 210 are coupled to inputs of the filter(s) 212. Output(s) of the filters 212 are coupled to input(s) of the PA(s) 216. Output(s) of the PAs 216 are coupled to antennas 1 10.

The second circuit stage 252 implements the transmit path(s) 1 14. In various configurations, some transmit paths 1 14A each include a DAC 208, a filter 209, and a PA 214. For example, the second circuit stage 252 can be configured to include N transmit paths 1 14A. Other output paths 1 14B each include a DAC 208, a filter 209, an analog modulator 210, a filter 212, and a PA 216. The second circuit stage 252 can be configured to include N or less output paths 1 14B. For example, second circuit stage 252 can be configured to include N/2 output paths 1 14B. The analog modulator(s) 210, the PAs 214, and the PA(s) 216 can be selectively enabled through control signals output by the controller 1 12. Thus, second circuit stage 252 can include different

configurations of transmit paths 1 14 depending on the mode of the transmitter 104.

The interface circuits 206 couple the modulated signals output by the first circuit stage 250 to one or more transmit paths 1 14 implemented in the second circuit stage 252 depending on a mode selected by the controller 1 12. As shown in examples below, interface circuits 206 can include adders and multiplexers that are configurable to route the modulated signals among the transmit path(s) 1 14 based on a selected mode. In one mode ("single-band mode"), the interface circuits 206 are configured to couple N modulated signals generated by the first circuit stage to a respective N transmit paths 1 14 implemented in second circuit stage 252. For example, if the modulated signals include RF carrier frequencies, the interface circuits 206 are configured to couple N modulated signals to N transmit paths 1 14A (e.g., a single-band direct-RF architecture). If the signals include IF carrier frequencies, the interface circuits 206 are configured to couple N modulated signals to N transmit paths 1 14B (e.g. a single-band real-IF architecture). In such an example, the analog modulators 210 function to upconvert the IF signals to RF signals for radiation by antennas 1 10. Only a single input of each analog modulator 210 is used.

In another mode ("multi-band mode"), the interface circuits 206 are configured to combine modulated signals and couple the combined modulated signals to transmit path(s) 1 14 implemented by the second circuit stage 252. That is, in a multi-band mode, the interface circuits 206 are configured to couple a sum(s) of at least two of the modulated signals output by the first circuit stage 250 to respective transmit path(s) 1 14, where the at least two modulated signals forming each sum have different carrier frequencies. Example multi-band modes for the transmitter 104 are described below. The configuration of interface circuits 206 is set by controller 1 12 based on the selected mode of the transmitter 104.

Fig. 3 is a block diagram illustrating a configuration 300 of the transmitter 104 according to an example. In the present example, the interface circuits 206 include adders 302i through 3023 (collectively "adders 302"), multiplexers 304i through 3043 (collectively "multiplexers 304"), and multiplexers 306i through 306 ₃ (collectively "multiplexers 306"). Each of the multiplexers 304 and 306 include two inputs and one output. Each of the adders 302 includes two inputs and one output.

In the present example, the interface circuits 206 receive outputs from four digital modulators 202i through 202 ₄ and provide output to four DACs 208i through 208 ₄ (e.g., N = 4 in Fig. 2). First inputs of the multiplexers 304 and 306 are each coupled to a reference voltage (e.g., electrical ground). First inputs of the adders 302i through 3023 are configured to receive modulated signals from the digital modulators 202i through 2023, respectively (designated channels (Ch) 1-3). An output of the adder 302i is coupled to an input of the DAC 208i, while outputs of the adders 3022 and 3023 are coupled to second inputs of the multiplexers 306i and 3062, respectively. Second inputs of the adders 302i through 3023 are coupled to outputs of the multiplexers 304i through 3043, respectively. Second inputs of the multiplexers 304i and 3042 are coupled to outputs of the adders 3022 and 3023, respectively. A second input of the multiplexer 3Ο63 is coupled to an output of a digital modulator 202 ₄ (designated Ch. 4). A second input of the multiplexer 3043 is also coupled to the output of the digital modulator 202 ₄ . Control inputs of the multiplexers 304i through 3043, and the multiplexers 306i through 3Ο63, receive enable signals EN1 through EN3, respectively, from the controller 1 12. The control inputs of the multiplexers 306i through 306 ₃ invert the enable signals EN1 through EN3.

The second circuit stage 252 includes transmit paths 1 14Ai through 1 14A ₄ . Each of the transmit paths 1 14A includes a DAC 208, a filter 209, and a PA 214. For each transmit path 1 14A, the DAC 208 converts a digital modulated signal to an analog signal. The filter 209 removes image(s) from the analog signal (e.g., a DAC image). The PA 214 increases the power of the analog signal for radiation by an antenna 1 10. The transmit paths 1 14Ai through 1 14A ₄ output RF analog signals RF1 through RF4.

In operation, each of the channels 1-4 is a modulated signal having a particular carrier frequency shifted from baseband frequency. The modulated signals on channels 1-4 can include carrier frequencies F1-F4. In the present example, the carrier frequencies F1-F4 comprise different RF frequencies. Each of the enable signals EN1 through EN3 is a two-state signal indicating either logic "1" or logic "0". When the control inputs of the multiplexers 304 and 306 receive a logic "0", the multiplexers 304 and 306 select the first inputs. When the control inputs of the multiplexers 304 and 306 receive a logic "1", the

multiplexers 304 and 306 select the second inputs.

In a first mode (single-band mode), the enable signals EN1 through EN3 are logic "0". Thus, in the single-band mode, the multiplexers 304i through 3043 select the first inputs (e.g., the reference voltage) and the channels 1 through 3 pass through the adders 302i through 3023. In the single-band mode, the multiplexers 306i through 3Ο63 select the second inputs, which are the outputs of the adders 302 ₂ through 303 ₃ . As such, the DACs 208i through 208 ₄ receive as input the channels 1 through 4, respectively. The signals RF1 through RF4 include carrier frequencies F1 through F4, respectively.

In another mode (a multi-band mode), the enable signals EN1 through EN3 are logic "1 ". In such a multi-band mode, the multiplexers 304i through 3043 select the second inputs (e.g., the outputs of the adders 3022 through 3023 and Ch4, respectively). As such, Ch4 is added to Ch3, the sum of Ch3 and Ch4 is added to Ch2, and the sum of Ch2-Ch4 is added to Ch1. The output of the adder 302i provides the sum of all of Ch1 through Ch4 to the input of the DAC 208i . In this multi-band mode, the signal RF1 includes four frequency bands having the carrier frequencies F1 through F4.

Other multi-band modes are possible. For example, if EN1 and EN3 are logic " and EN 2 is logic "0", then Ch1 and Ch2 are summed and Ch3 and Ch4 are summed. The signal RF1 includes two frequency bands with carrier frequencies of F1 and F2, and the signal RF2 includes two frequency bands with carrier frequencies of F3 and F4. In another example, the enable signals EN1 and EN2 are logic "1 " and EN3 is logic "0". In such an example, the signal RF1 includes three frequency bands with carrier frequencies of F1 -F3, and the signal RF4 includes a single frequency band with a carrier frequency of F4. The interface circuits 206 can support more or less than four channels.

Fig. 4 is a block diagram illustrating another configuration 400 of the transmitter 104 according to another example. In the present example, the interface circuits 206 include adders 402i through 402 ₄ (collectively adders 402) and multiplexers 404i through 404 ₄ (collectively multiplexers 404). Each of the multiplexers 404 include two inputs and one output. Each of the adders 402 includes two inputs and one output.

A first input of the adder 402i is coupled to in-phase output of the digital modulator 2021 (designated Ch1_l) and a second input of the adder 4021 is coupled to an output of the multiplexer 404i . A first input of the adder 4022 is coupled to a quadrature-phase output of the digital modulator 2021 (designated Ch2_Q) and a second input of the adder 4022 is coupled to an output of the multiplexer 4042. First inputs of the multiplexers 404i and 4042 are coupled to a reference voltage (e.g., electrical ground). A second input of the multiplexer 404i is coupled to in-phase output of the digital modulator 2022 (designated Ch2_l). A second input of the multiplexer 4042 is coupled to quadrature-phase output of the digital modulator 2021 (designated Ch1_Q). Control inputs of the multiplexers 404i and 4042 are coupled to a control signal EN1 provided by the controller 1 12. Outputs of the adders 402i and 4022 are coupled to the inputs of DACs 208i and 208 ₂ , respectively.

A first input of the adder 4023 is coupled to in-phase output of the digital modulator 2023 (designated Ch3_l) and a second input of the adder 4023 is coupled to an output of the multiplexer 4043. A first input of the adder 402 ₄ is coupled to a quadrature-phase output of the digital modulator 202 ₄ (designated Ch4_Q) and a second input of the adder 402 ₄ is coupled to an output of the multiplexer 404 ₄ . First inputs of the multiplexers 4043 and 404 ₄ are coupled to a reference voltage (e.g., electrical ground). A second input of the multiplexer 4043 is coupled to in-phase output of the digital modulator 202 ₄ (designated Ch4_l). A second input of the multiplexer 404 ₄ is coupled to quadrature-phase output of the digital modulator 2023 (designated Ch3_Q). Control inputs of the multiplexers 4043 and 404 ₄ is coupled to a control signal EN2 provided by the controller 1 12. Outputs of the adders 4023 and 402 ₄ are coupled to the inputs of DACs 208s and 208 ₄ , respectively.

In the present example, outputs of the DACs 208i and 2Ο82 are coupled to in-phase and quadrature-phase inputs of the analog modulator 210i, respectively. Outputs of the DACs 2Ο83 and 208 ₄ are coupled to in-phase and quadrature-phase inputs of the analog modulator 2 I O2, respectively. Filters 209 and 212 are omitted for clarity, but are disposed between DACs 208 and PAs 214 and between analog modulators 210 and PAs 216, as shown in Fig. 2.

Each of the enable signals EN1 and EN2 is a two-state signal indicating either logic "1" or logic "0". When the control inputs of the multiplexers 404 receive a logic "0", the multiplexers 404 select the first inputs. When the control inputs of the multiplexers 404 receive a logic "1 ", the multiplexers 404 select the second inputs. In a first mode (single-band mode), the enable signals EN1 and EN2 are logic "0". In the single-band mode, each adder 402 passes its input signal to a respective DAC 208. The signals at the first inputs of the adders 402 (i.e., Ch1_l, Ch2_Q, Ch3_l, and Ch4_Q) can be modulated signals each comprising a different RF frequency band. The outputs of the PAs 214i through 214 ₄ provide RF signals Direct RF1 through Direct RF4, respectively. The signals Direct RF1 through Direct RF4 include frequency bands having carrier frequencies F1 through F4, respectively. Thus, in the single-band mode, the transmitter 104 includes four single-band direct-RF output paths 1 14Ai through 1 14A ₄ . In the single-band mode, the controller 1 12 can disable the analog modulators 210 and the PAs 216.

In another mode (a multi-band mode), the enable signals EN1 and EN2 are logic "1". In such a multi-band mode, the multiplexers 404 select the second inputs. As such, the output of the adder 402i is the sum of Ch1_l and Ch2_l; the output of the adder 4022 is the sum of Ch1_Q and Ch2_Q; the output of the adder 4023 is the sum of Ch3_l and Ch4_l; and the output of the adder 402 ₄ is the sum of Ch3_Q and Ch4_Q. Each of the signals Ch1_l through Ch4_l and Ch1_Q through Ch4_Q4 can be a modulated signal comprising an IF carrier frequency (e.g., IF1 through I F4 for channels 1 through 4). The in-phase channels Ch1_l through Ch4_l include in-phase modulated signals, and the quadrature-phase channels Ch1_Q through Ch4_Q include quadrature-phase modulated signals. The DAC 208i outputs a multi-band in-phase analog signal to the in-phase input of the analog modulator 21 Oi (having IF carrier frequencies IF1 and IF2), and the DAC 2Ο82 outputs a multi-band quadrature-phase analog signal to the quadrature-phase input of the analog modulator 21 Oi (having IF frequencies I F1 and IF2). The analog modulator 21 Oi upconverts and sums the multi-band in-phase and quadrature-phase analog signals and the PA 2161 outputs an RF analog signal (Complex RF1 ). The Complex RF1 signal includes a single RF carrier frequency modulated by in-phase and quadrature-phase signals each having multiple IF carrier frequencies.

The DAC 2Ο83 outputs a multi-band in-phase analog signal to the in- phase input of the analog modulator 2103 (having IF frequencies IF3 and IF4), and the DAC 208 ₄ outputs a multi-band quadrature-phase analog signal to the quadrature-phase input of the analog modulator 210 ₄ (having IF frequencies IF3 and IF4). The analog modulator 2102 upconverts and sums the multi-band in- phase and quadrature-phase analog signals and the PA 2162 outputs an RF analog signal (Complex RF2). The Complex RF2 analog signal includes a single RF carrier frequency modulated by in-phase and quadrature-phase signals each having multiple IF carrier frequencies. Thus, in this multi-band mode, the transmitter 104 includes two transmit paths 1 14Bi and 1 14B2. In the multi-band mode, the controller 1 12 can disable the PAs 214i through 214 ₄ .

The example of Fig. 4 illustrates 2 independent 2-band IQ transmitters. In another example, with another level of multiplexing and associated adders, the same circuit block can be configured as a single 4-band IQ transmitter.

Referring to Fig. 2, each of the first circuit stage 250 and the second circuit stage 252 can have a fixed structure as shown. The interface circuits 206 can have a fixed structure, such as the structure shown in Fig. 3 or the structure shown in Fig. 4. In another example, the structure of interface circuits 206 can be configurable. The controller 1 12 can configure the interface circuits 206 to have either the structure shown in Fig. 3 or the structure shown in Fig. 4.

Fig. 5 is a block diagram depicting the receiver 106 according to an example. The receiver 106 includes a first circuit stage 552, interface circuits 506, and a second circuit stage 550. Inputs of the first circuit stage 552 receive RF energy from antennas 1 10. Outputs of the first circuit stage 552 are coupled to inputs of the interface circuits 506. The outputs of the first circuit stage 552 provide digital signals generated from the received RF energy. Outputs of the interface circuits 506 are coupled to inputs of the second circuit stage 550. The interface circuits 506 selectively couple the digital signals to the demodulator paths 1 16 implemented by the second circuit stage 550. Outputs of the second circuit stage 550 provide baseband signals.

The first stage circuit 552 includes analog-to-digital converters (ADCs) 508 and low-noise amplifiers (LNAs) 514. In the present example, the first circuit stage 552 includes N ADCs 508i through 508 _N , and N LNAs 514i through 514 _N . Inputs of the LNAs 514 are coupled to the antennas 1 10. Outputs of the LNAs 514 are coupled to inputs of the ADCs 508. Outputs of the ADCs 508 are coupled to inputs of the interface circuits 506. In some examples, the first circuit stage 552 also includes analog demodulator(s) 510 and LNA(s) 516. Input(s) of the LNA(s) 516 are coupled to the antenna(s) 1 10. Output(s) of the LNA(s) 516 are coupled to input(s) of the analog demodulator(s) 510. Outputs of each of the analog demodulator(s) 510 are coupled to inputs of ADCs 508.

The first stage circuit 552 implements the plurality of receive paths 1 15. In operation, some receive paths 1 15A include an ADC 508 and an LNA 514 coupled to an antenna 1 10. The bandwidth of a receive path 1 15A includes at least one RF frequency band being received. For example, the first stage circuit 552 can include N receive paths 1 15A. Other receive paths 1 15B include an LNA 514, an analog demodulator 510, and an ADC 508. The bandwidth of a receive path 1 15B includes at least one RF frequency band being received. The first stage circuit 552 can include N or less receive paths 1 15B. For example, the first circuit stage 552 can include N/2 receive paths 1 15B. The analog demodulators 510, the LNAs 514/516, and the ADCs 508 can be selectively enabled through control signals output by the controller 1 12. Thus, the first circuit stage 552 can include different configurations of the receive paths 1 15 depending on the mode of the receiver 106.

The interface circuits 506 couple the digital signals output by the first circuit stage 552 to one or more demodulator paths 1 16 implemented in the second circuit stage 550 depending on a mode selected by the controller 1 12. As shown in examples below, interface circuits 506 can include multiplexers that are configurable to route the digital signals among the demodulator path(s) 1 16 based on a selected mode. In one mode ("single-band mode"), the interface circuits 506 are configured to couple N digital signals generated by the first circuit stage 552 to a respective N demodulator paths 1 16 implemented in second circuit stage 550. For example, each of the N receive paths 1 15 can include a bandwidth having a respective one of N RF frequency bands. Thus, each digital signal has a different RF frequency band. Each of the N

demodulator paths 1 16 can process a different RF carrier frequency to recover the baseband signals (e.g., a single-band direct-RF architecture).

In another mode ("multi-band mode"), the interface circuits 506 are configured to couple each of one or more digital signals to multiple demodulator paths 1 16 implemented by the second circuit stage 550 each processing a different carrier frequency. That is, in a multi-band mode, the interface circuits 506 are configured to couple a given digital signal to at least two of the demodulator paths 1 16, where the at least two demodulator paths 1 16 process different carrier frequencies. Example multi-band modes for the receiver 106 are described below. The configuration of interface circuits 506 is set by controller 1 12 based on the selected mode of the receiver 106.

In an example, the second circuit stage 550 includes a plurality of digital demodulators 502, a plurality of decimators 503, and a plurality of NCOs 504. Inputs of the digital demodulators 502 are coupled to outputs of the interface circuits 506. Outputs of the digital demodulators 502 are coupled to inputs of the decimators 503. LO inputs of the digital demodulators 502 are coupled to outputs of the NCOs 504. Outputs of the decimators 503 provide baseband signals. In the example of Fig. 5, the second circuit stage 550 includes N digital demodulators 502i through 502N, where N is an integer greater than one. Each of the demodulator paths 1 16 includes a respective one of the demodulators 502 (e.g., N demodulator paths 1 16). The decimators 503 include in-phase decimators 503 through 503IN and quadrature-phase decimators 503Qi through 503QN. The decimators 503 and 503Qi are coupled to the digital demodulator 503i and the decimators 503IN and 503QN are coupled to the digital demodulator 503 _N . The NCOs 504 include NCOs 504i through 504 _N . Each of the NCOs 504i through 504N is coupled to a respective one of the digital demodulators 502i through 502N.

In operation, the receive paths 1 15 generate digital signals from the received RF energy. Each of the digital demodulators 502 demodulates a different carrier frequency. The digital demodulators 502 can perform in-phase or quadrature demodulation depending on the particular digital modulation scheme employed. The NCOs 204 generate LO signals each having a selected carrier frequency. The selected carrier frequency can be an RF frequency or IF frequency depending on the receiver configuration. The decimators 503 reduce the sample rate of the baseband signals output by the digital demodulators 502. The receiver 106 supports both real IF/RF and complex IF receiver architectures. The configuration of the first circuit stage 552 can be controlled by the controller 1 12.

Fig. 6 is a block diagram illustrating a configuration 600 of the receiver 106 according to an example. In the example, the interface circuits 506 include multiplexers 602i through 6023 (collectively multiplexers 602). Receive paths 115Ai through 1 15A ₄ include LNAs 514i through 514 ₄ and ADCs 508i through 508 ₄ (e.g., N = 4). First inputs of the multiplexers 602i through 6023 are coupled to outputs of the ADCs 5082 through 508 ₄ , respectively. Second inputs of the multiplexers 602 are coupled to the output of ADC 508i. Control inputs of the multiplexers 602i through 6023 receive enable signals EN1 through EN3, which are provided by the controller 1 12. An output of the ADC 508i provides a digital signal for a first demodulator (demodl ). Outputs of the multiplexers 602i through 6023 provide digital signals for second, third, and fourth demodulators (demod2, demod3, and demod4).

In operation, when EN1 through EN3 are at logic "0", the multiplexers 602 select the first inputs. The enable signals EN1 through EN3 are set to logic "0" in the single-band mode. In the single-band mode, a digital signal is provided to the first demodulator for processing the carrier frequency of RF1 , a digital signal is provided to the second demodulator for processing the carrier frequency of RF2, a digital signal is provided to the third demodulator for processing the carrier frequency of RF3, and a digital signal is provided to the fourth

demodulator for processing the carrier frequency RF4. Each of the receive paths 1 15A has a bandwidth that includes a respective one of the RF frequency bands of RF1 -RF4.

When EN1 through EN3 are set to logic "1", the multiplexers 602 select the second inputs (e.g., the output of the ADC 508i). The enable signals EN1 through EN3 are set to logic " in the multi-band mode. In the multi-band mode, the digital signal output by the receive path 1 15Ai is coupled to each of the first through fourth demodulators, each of which processes a different carrier RF frequency of RF1 through RF4. The receive path 1 15Ai has a bandwidth that includes each of the RF frequency bands of RF1 through RF4. Other multi-band modes are possible (e.g., only EN1 is ", EN1 and EN1 are Ί " and EN 3 is "0"). Further, more complete multiplexing options can be provided. For example, multiplexing can be provided for two independent 2-band receivers, where demodi and demod2 are driven by ADC 508i , while demod3 and demod4 are driven by ADC 508-3. In another example, a full cross-bar multiplexer can be used to provide full flexibility in what combination of source ADC receivers can drive the demodulator paths.

Fig. 7 is a block diagram illustrating a configuration 700 of the receiver

106 according to an example. In the example, the interface circuits 506 include multiplexers 702i through 702 ₄ (collectively multiplexers 702). The first circuit stage 552 includes ADCs 508i through 508 ₄ , LNAs 514i through 514 ₄ , analog demodulators 510i and 510 ₂ , and LNAs 5161 and 516 ₂ . An output of the ADC 508i provides a digital signal to an in-phase input of a first demodulator

(demodlj). An output of the ADC 5082 provides a digital signal to a quadrature- phase input of a second demodulator (demod2_Q). A first input of the multiplexer 702i is coupled to the output of the ADC 508i , and a second input of the multiplexer 702i is coupled to the output of the ADC 5Ο82. A first input of the multiplexer 7022 is coupled to the output of the ADC 5Ο82, and a second input of the multiplexer 7022 is coupled to the output of the ADC 508i. An output of the multiplexer 702i is coupled to a quadrature-phase input of the first demodulator (demod1_Q). An output of the multiplexer 7022 is coupled to an in-phase input of the second demodulator (demod2_l). Control inputs of the multiplexers 702i and 7022 are coupled to receive an enable signal EN1 from the controller 1 12. As described in the examples above, in another example, a full cross-bar multiplexer allows for more combinations of ADC-to-demodulator couplings.

An output of the ADC 5083 provides a digital signal to an in-phase input of a third demodulator (demod3_l). An output of the ADC 508 ₄ provides a digital signal to a quadrature-phase input of a fourth demodulator (demod4_Q). A first input of the multiplexer 7023 is coupled to the output of the ADC 5Ο83, and a second input of the multiplexer 7023 is coupled to the output of the ADC 508 ₄ . A first input of the multiplexer 702 ₄ is coupled to the output of the ADC 508 ₄ , and a second input of the multiplexer 702 ₄ is coupled to the output of the ADC 5Ο83. An output of the multiplexer 7023 is coupled to a quadrature-phase input of the third demodulator (demod3_Q). An output of the multiplexer 702 ₄ is coupled to an in-phase input of the fourth demodulator (demod4_l). Control inputs of the multiplexers 7023 and 702 ₄ are coupled to receive an enable signal EN2 from the controller 1 12.

In a first mode (single-band mode), the first circuit stage 552 is configured to provide receive paths 1 15Ai through 1 15A ₄ . Each receive path 1 15A includes an LNA 514 and an ADC 508. In the single-band mode, the enable signals EN1 and EN2 are logic "0" and select the first inputs of the multiplexers 702. In such case, a digital signal output by each receive path 1 15A is coupled to both the I and Q inputs of a respective demodulator. Each receive path 1 15A has a bandwidth that includes a respective one of RF frequency bands RF1 -RF4. Each of the demodulators demodulates a respective RF carrier frequency of RF frequency bands RF1 -RF4. In the single-band mode, the controller 1 12 can disable the LNAs 516 and the analog demodulators 510.

In a second mode (multi-band mode), the first circuit stage 552 is configured to provide receive paths 1 15Bi through 1 15B ₄ . Each receive path 1 15B includes an LNA 516, an analog demodulator 510, and an ADC 508. In the multi-band mode, the enable signals EN1 and EN2 are logic "1 " and select the second inputs of the multiplexers 702. In such case, a digital signal output by each receive path 1 15B is coupled to inputs of two of the demodulators. In particular, the digital signal output by the receive path 1 15Bi is coupled to the in- phase inputs of the first and second demodulators (demodlj and demod2_l). The digital signal output by the receive path 1 1 5B2 is coupled to the quadrature- phase inputs of the first and second demodulators (demod1_Q and demod2_Q). Likewise, the digital signal output by the receive path 1 15B3 is coupled to the in- phase inputs of the third and fourth demodulators (demod3_l and demod4_l), and the digital signal output by the receive path 1 15B ₄ is coupled to the quadrature-phase inputs of the third and fourth demodulators (demod3_Q and demod4_Q). The digital signal output by the receive path 1 15Bi includes an in- phase digital carrier signal (IF_ ,2) having first and second IF frequency bands (e.g., IF carrier frequencies I F1 and I F2). The digital signal output by the receive path 1 15B2 includes a quadrature-phase carrier signal (IF_Qi,2) having the first and second IF frequency bands. Likewise, the digital signal output by the receive path 1 15B3 includes an in-phase digital carrier signal (I F 13,4) having third and fourth IF frequency bands (e.g., IF carrier frequencies I F3 and IF ₄ ). The digital signal output by the receive path 1 15B ₄ includes a quadrature-phase carrier signal (IF_Ch, ₄ ) having the third and fourth I F frequency bands. The analog demodulator 5101 generates the digital signal IF_ ,2 by demodulating an in-phase RF carrier signal having an RF carrier frequency RF_multi1 . The analog demodulator 5101 generates the digital signal IF_Qi,2 by demodulating a quadrature-phase RF carrier signal having the RF carrier frequency RF_multi1 . Likewise, the analog demodulator 5102 generates the digital signal IF_ , ₄ by demodulating an in-phase RF carrier signal having an RF carrier frequency

RF_multi2. The analog demodulator 5102 generates the digital signal IF_Ch, ₄ by demodulating a quadrature-phase RF carrier signal having the RF carrier frequency RF_multi2. In the multi-band mode, the LNAs 514 can be disabled.

The transceiver 101 described herein can be used in an IC, such as a field programmable gate array (FPGA) or other type of programmable IC or in an application specific integrated circuit (ASIC). Although an FPGA is shown by way of example, it is to be understood that the transceiver 101 can be implemented in other types of ICs or applications. Fig. 8 illustrates an architecture of an FPGA 800 that includes a large number of different programmable tiles including multi-gigabit transceivers ("MGTs") 1 , configurable logic blocks ("CLBs") 2, random access memory blocks ("BRAMs") 3, input/output blocks ("lOBs") 4, configuration and clocking logic

("CONFIG/CLOCKS") 5, digital signal processing blocks ("DSPs") 6, specialized input/output blocks ("I/O") 7 (e.g., configuration ports and clock ports), and other programmable logic 8 such as digital clock managers, analog-to-digital converters, system monitoring logic, and so forth. Some FPGAs also include dedicated processor blocks ("PROC") 10.

In some FPGAs, each programmable tile can include at least one programmable interconnect element ("INT") 1 1 having connections to input and output terminals 20 of a programmable logic element within the same tile, as shown by examples included at the top of Fig. 8. Each programmable interconnect element 1 1 can also include connections to interconnect segments 22 of adjacent programmable interconnect element(s) in the same tile or other tile(s). Each programmable interconnect element 1 1 can also include connections to interconnect segments 24 of general routing resources between logic blocks (not shown). The general routing resources can include routing channels between logic blocks (not shown) comprising tracks of interconnect segments (e.g., interconnect segments 24) and switch blocks (not shown) for connecting interconnect segments. The interconnect segments of the general routing resources (e.g., interconnect segments 24) can span one or more logic blocks. The programmable interconnect elements 1 1 taken together with the general routing resources implement a programmable interconnect structure ("programmable interconnect") for the illustrated FPGA.

In an example implementation, a CLB 2 can include a configurable logic element ("CLE") 12 that can be programmed to implement user logic plus a single programmable interconnect element ("INT") 1 1 . A BRAM 3 can include a BRAM logic element ("BRL") 13 in addition to one or more programmable interconnect elements. Typically, the number of interconnect elements included in a tile depends on the height of the tile. In the pictured example, a BRAM tile has the same height as five CLBs, but other numbers (e.g. , four) can also be used. A DSP tile 6 can include a DSP logic element ("DSPL") 14 in addition to an appropriate number of programmable interconnect elements. An IOB 4 can include, for example, two instances of an input/output logic element ("IOL") 15 in addition to one instance of the programmable interconnect element 1 1 . As will be clear to those of skill in the art, the actual I/O pads connected, for example, to the I/O logic element 15 typically are not confined to the area of the input/output logic element 15. In the pictured example, a horizontal area near the center of the die (shown in Fig. 8) is used for configuration, clock, and other control logic. Vertical columns 9 extending from this horizontal area or column are used to distribute the clocks and configuration signals across the breadth of the FPGA.

Some FPGAs utilizing the architecture illustrated in Fig. 8 include additional logic blocks that disrupt the regular columnar structure making up a large part of the FPGA. The additional logic blocks can be programmable blocks and/or dedicated logic. For example, processor block 10 spans several columns of CLBs and BRAMs. The processor block 10 can various components ranging from a single microprocessor to a complete programmable processing system of microprocessor(s), memory controllers, peripherals, and the like.

Note that Fig. 8 is intended to illustrate only an exemplary FPGA architecture. For example, the numbers of logic blocks in a row, the relative width of the rows, the number and order of rows, the types of logic blocks included in the rows, the relative sizes of the logic blocks, and the

interconnect/logic implementations included at the top of Fig. 8 are purely exemplary. For example, in an actual FPGA more than one adjacent row of CLBs is typically included wherever the CLBs appear, to facilitate the efficient implementation of user logic, but the number of adjacent CLB rows varies with the overall size of the FPGA.

Fig. 9 is a flow diagram depicting a method 900 of configuring a configurable single-band/multi-band transmitter according to an example. The method 900 can be performed by the communication system 100 to configure the transmitter 104. The method 900 begins at step 902, where the controller 1 12 configures the modulator paths 1 13 of the first circuit stage 250 of the transmitter 104. For example, at step 904, the controller 1 12 can set the carrier frequencies of the NCOs 204 in each modulator path 1 13. At step 906, the controller 1 12 can configure the digital modulators 202 to perform a particular digital modulation scheme (e.g., any type of quadrature modulation scheme or single-phase modulation scheme).

At step 908, the controller 1 12 selects a mode of the transmitter 104. The mode can be a single-band mode or one of a plurality of multi-band modes. At step 910, the controller 1 12 configures the interface circuits 206 and the second circuit stage 252 based on the selected mode. For example, at step 912, the controller 1 12 configures the second circuit stage 252 to have one or more transmit paths 1 14. The controller 1 12 can enable/disable components of the second circuit stage 252 to implement the transmit path(s) 1 14. For example, in single-band mode, the controller 1 12 can configure the second circuit stage 252 to have a plurality of transmit paths 1 14A each having a DAC 208, a filter 209, and a PA 214. In a multi-band mode, the controller 1 12 can configure the second circuit stage 252 to have one or more transmit paths 1 14B each having a DAC 208, a filter 209, an analog modulator 210, a filter 212, and a PA 216.

At step 914, the controller 1 12 configures the interface circuits 206 to couple the modulated signals output by the first circuit stage 250 to the configured transmit path(s) 1 14. For example, in single-band mode, the controller 1 12 can configure the interface circuits 206 to couple each modulated signal to a respective one of the plurality of transmit paths 1 14A. In a multi-band mode, the controller 1 12 can configure the interface circuits 206 to generate sum(s) of the modulated signal and to couple each sum to a respective one of the transmit path(s) 1 14B.

Fig. 10 is a flow diagram depicting a method 1000 of configuring a configurable single-band/multi-band receiver according to an example. The method 1000 can be performed by the communication system 100 to configure the receiver 106. The method 1000 begins at step 1002, where the controller 1 12 configures the demodulator paths 1 16 in the second stage circuit 550 of the receiver 106. For example, at step 1004, the controller 1 12 can set the carrier frequencies of the NCOs 504 in each demodulator path 1 16. At step 1006, the controller 1 12 can configure the digital demodulators 502 to perform a particular digital demodulation scheme (e.g., any type of quadrature demodulation scheme or single-phase demodulation scheme).

At step 1008, the controller 1 12 selects a mode of the receiver 106. The mode can be a single-band mode or one of a plurality of multi-band modes. At step 1010, the controller 1 12 configures the interface circuits 506 and the first circuit stage 552 based on the selected mode. For example, at step 1012, the controller 1 12 configures the first circuit stage 552 to have one or more receive paths 1 15. The controller 1 12 can enable/disable components of the first circuit stage 552 to implement the receive path(s) 1 15. For example, in single-band mode, the controller 1 12 can configure the first circuit stage 552 to have a plurality of receive paths 1 15A each having an LNA 514 and an ADC 508. In a multi-band mode, the controller 1 12 can configure the first circuit stage 552 to have one or more receive paths 1 15B each having an LNA 516, an analog demodulator 510, and an ADC 508.

At step 1014, the controller 1 12 configures the interface circuits 506 to couple the digital signals output by configured receive path(s) 1 15 of the first circuit stage 552 to the demodulator paths 1 16. For example, in single-band mode, the controller 1 12 can configure the interface circuits 506 to couple each digital signal from a plurality of receive paths 1 15A to a respective one of the plurality of demodulator paths 1 16. In a multi-band mode, the controller 1 12 can configure the interface circuits 506 to couple each digital signal from a plurality of receive paths 1 15B to at least two of the plurality of demodulator paths 1 16.

In some examples below, techniques for reconfiguration of single-band transmit and receive paths to multi-band transmit and receive paths in an integrated circuit (IC) are described.

In an example, a transmitter is provided. Such a transmitter may include: a first circuit stage configured to generate modulated signals from baseband signals, each of the modulated signals comprising a digital signal having respective a carrier frequency of a plurality of carrier frequencies; a second circuit stage configured to generate radio frequency (RF) energy to be radiated by one or more antennas; and interface circuits coupled between the first circuit stage and the second circuit stage; wherein the second circuit stage and the interface circuits are configurable to provide a first mode and a second mode; wherein, in the first mode, the second circuit stage provides a plurality of transmit paths and the interface circuits couple each of the modulated signals to a respective one of the plurality of transmit paths; and wherein, in the second mode, the second circuit stage provides a first transmit path and the interface circuits couple a sum of at least two of the modulated signals to the first transmit path.

In such a transmitter, in the second mode, the second circuit stage may provide a second transmit path and the interface circuits couple another sum of another at least two of the modulated signals to the second transmit path. In such a transmitter, in the first mode, each of the plurality of carrier frequencies may include an RF frequency and each of the plurality of transmit paths includes a digital-to-analog converter (DAC) and a power amplifier (PA).

In such a transmitter, in the second mode, the carrier frequencies of the at least two modulated signals may include RF frequencies and the first transmit path includes a digital-to-analog converter (DAC) and a power amplifier (PA).

In such a transmitter, in the second mode, the carrier frequencies of the at least two modulated signals may include intermediate frequency (IF) frequencies and the first transmit path includes a digital-to-analog converter (DAC), an analog modulator, and a power amplifier (PA).

In such a transmitter, in the second mode: the at least two modulated signals may include a first in-phase modulated signal having a first intermediate frequency (IF) and a second in-phase modulated signal having a second IF frequency; and the second circuit stage provides a second transmit path and the interface circuits couple a sum of a first quadrature modulated signal and a second quadrature modulated signal to the second transmit path, the first quadrature modulated signal having the first IF frequency and the second quadrature modulated signal having the second IF frequency.

In such a transmitter, the first transmit path may include a first digital-to- analog converter (DAC), an analog modulator, and a power amplifier (PA), and the second transmit path may include a second DAC, the analog modulator, and the PA.

In such a transmitter, the first circuit stage may include: interpolators configured increase the sampling-rate of the baseband signals; and digital modulators, coupled to the interpolators, configured to generate the modulated signals from the baseband signals.

In such a transmitter, the first circuit stage further may include:

numerically controlled oscillators (NCOs), coupled to the digital modulators, configured to provide digital carrier signals for modulation by the baseband signals to generate the modulated signals.

In such a transmitter, the baseband signals may include in-phase baseband signals and quadrature baseband signals, and wherein each of the modulated signals is a sum of an in-phase digital carrier signal modulated by one of the in-phase baseband signals and a quadrature digital carrier signal modulated by one of the quadrature baseband signals.

In another example, a receiver is provided. Such a receive may include: a first circuit stage configured to receive radio frequency (RF) energy from one or more antennas; a second circuit stage having a plurality of demodulation paths each comprising a digital demodulator configured to process a respective frequency of a plurality of frequencies; and interface circuits coupled between the first circuit stage and the second circuit stage; wherein the first circuit stage and the interface circuits may be configurable to provide a first mode and a second mode; wherein, in the first mode, the first circuit stage generates a plurality of digital signals from the RF energy and the interface circuits couple each of the plurality of digital signals to a respective one of the plurality of demodulation paths; and wherein, in the second mode, the first circuit stage generates a first digital signal from the RF energy and the interface circuits couple the first digital signal to at least two of the plurality of demodulation paths.

In such a receiver, in the second mode, the first circuit stage generates a second digital signal from the RF energy and the interface circuits couple the second digital signal to at least two other of the plurality of demodulation paths.

In such a receiver, in the second mode, the first circuit stage generates a second digital signal from the RF energy and the interface circuits couple the second digital signal to the at least two demodulation paths receiving the first digital signal.

In such a receiver, in the second mode: the at least two demodulation paths may include a first demodulation path having a first digital demodulator and a second demodulation path having a second digital demodulator; the first digital demodulator processes a first frequency of the plurality of frequencies and the second digital demodulator processes a second frequency of the plurality of frequencies; and each of the first and second digital demodulators include in- phase (I) and quadrature (Q) inputs configured to receive the first digital signal and the second digital signal, respectively.

In such a receiver, the first frequency is a first intermediate frequency (IF) frequency and the second frequency is a second IF frequency and wherein, in the second mode, the first circuit stage provides: a first receive path configured to generate an in-phase IF signal from the RF energy and the first digital signal from the in-phase IF signal; and a second receive path configured to generate a quadrature IF signal from the RF energy and the second digital signal from the quadrature IF signal.

In such a receiver, the first receive path may include a low-noise amplifier (LNA), an analog demodulator, and a first analog-to-digital converter (ADC), and wherein the second receive path includes the LNA, the analog demodulator, and a second ADC.

In such a receiver, in the first mode: the plurality of demodulation paths may include a first demodulation path having a first digital demodulator; the first digital demodulator processes a first frequency of the plurality of frequencies; the first digital demodulator includes in-phase (I) and quadrature (Q) inputs; and in the first mode, the interface circuits couple one of the plurality of digital signals to both of the I and Q inputs of the first digital demodulator.

In such a receiver, the first frequency is a first RF frequency and wherein, in the first mode, the first circuit stage provides a first receive path configured to generate the one of the plurality of digital signals from the RF energy.

In such a receiver, the first receive path includes a low-noise amplifier (LNA) and an analog-to-digital converter (ADC).

In such a receiver, in the second mode: the first circuit stage provides a first receive path configured to generate the first digital signal; the first receive path includes a low-noise amplifier (LNA) and an analog-to-digital converter

(ADC).

While the foregoing is directed to specific examples, other and further examples may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.