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Title:
CONTROLLING AN ANTENNA ARRAY
Document Type and Number:
WIPO Patent Application WO/2019/174757
Kind Code:
A1
Abstract:
A method of controlling an antenna array (101) comprising a plurality of antennas (102:1, 102:2, 102:N) is provided, where each antenna in the array comprises an individual transmit path (103:1, 103:2, 103:N) for transmitting signals via the antenna. The method comprises measuring, for at least two of the antennas (102:1, 102:2) of the antenna array (101), a temperature value of the transmit path (103:1, 103:2) for each of the at least two antennas, acquiring at least one of a first delay and phase-shift value corresponding to the measured temperature value of a first (103:1) of the at least two transmit paths, acquiring at least one of a second delay and phase-shift value corresponding to the measured temperature value of a second (103:2) of the at least two transmit paths, and applying delay and/or phase-shift to signals of at least one of the at least two transmit paths (103:1, 103:2) according to the acquired first and second delay and/or phase-shift values in order to align the signals of the first transmit path (103:1) with the signals of the second transmit path (103:2) in terms of delay and/or phase-shift.

Inventors:
YU XIAODONG (CN)
YANG JINSONG (CN)
HUANG MING (CN)
YU JING (CN)
Application Number:
PCT/EP2018/064585
Publication Date:
September 19, 2019
Filing Date:
June 04, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ERICSSON TELEFON AB L M (SE)
International Classes:
H04B17/12
Foreign References:
US6172642B12001-01-09
US20170070247A12017-03-09
US5680141A1997-10-21
Other References:
None
Attorney, Agent or Firm:
ERICSSON (SE)
Download PDF:
Claims:
CLAIMS

1. A method of controlling an antenna array (101) comprising a plurality of antennas (102:1, 102:2, 102:N), where each antenna in the array comprises an individual transmit path (103:1, 103:2, 103:N) for transmitting signals via the antenna, comprising:

measuring (S101), for at least two of the antennas (102:1, 102:2) of the antenna array (101), a temperature value of the transmit path (103:1, 103:2) for each of the at least two antennas;

acquiring (S102) at least one of a first delay and phase-shift value corresponding to the measured temperature value of a first (103:1) of the at least two transmit paths;

acquiring (S103) at least one of a second delay and phase-shift value corresponding to the measured temperature value of a second (103:2) of the at least two transmit paths; and

applying (S104) delay and/or phase-shift to signals of at least one of the at least two transmit paths (103:1, 103:2) according to the acquired first and second delay and/or phase-shift values in order to align the signals of the first transmit path (103:1) with the signals of the second transmit path (103:2) in terms of delay and/or phase-shift.

2. The method of claim 1, the acquiring (S102, S103) of the first and second delay/and or phase shift value further comprising:

acquiring the first and second delay/and or phase shift value from a look-up table storing, for each of a plurality of temperature values, a corresponding delay and/or phase-shift value indicating to which extent signals transmitted in the at least two transmit paths (103:1, 103:2) are delayed and phase-shifted.

3. The method of claim 1, the acquiring (S102, S103) of the first and second delay/and or phase shift value further comprising:

acquiring the first and second delay/and or phase shift value from a stored mathematical relationship between temperature and delay and/or phase-shift value indicating to which extent signals transmitted in the at least two transmit paths are delayed and/or phase-shifted for a given temperature value.

4. The method of claim 1, the acquiring (S102, S103) of the first and second delay/and or phase shift value further comprising:

injecting, in each transmit path, an antenna calibration, AC, signal; measuring, in each transmit path, relative delay and/or phase-shift that the AC signal is subjected to with respect to the AC signal of a selected reference transmit path after having traversed said each transmit path; and extrapolating, based on the measured relative delay and/or phase-shift, a corresponding delay and/or phase-shift value indicating to which extent signals transmitted in the at least two transmit paths (103:1, 103:2) are delayed and phase-shifted.

5. The method of claim 4, wherein the measuring of the delay and/or phase-shift that the AC signal is subjected to in each transmit path is performed by comparing the AC signal having traversed said each transmit path with the injected AC signal.

6. The method of claims 4 or 5, the AC signal being a baseband signal. 7.

The method of any one of the preceding claims, wherein the

temperature of each transmit path is measured at a radio frequency, RF, mixer arranged in said each transmit path.

8. A computer program (109) comprising computer-executable

instructions for causing an antenna array control device (110) to perform steps recited in any one of claims 1-7 when the computer-executable instructions are executed on a processing unit (106) included in the antenna array control device (110).

9. A computer program product comprising a computer readable medium (108), the computer readable medium having the computer program (109) according to claim 8 embodied thereon.

10. An antenna array control device (no) configured to control an antenna array (101) comprising a plurality of antennas (102:1, 102:2, 102:N), where each antenna in the array comprises an individual transmit path (103:1, 103:2, 103 :N) for transmitting signals via the antenna, the antenna array control device (101) comprising:

temperature sensors (105:1, 105:2) configured to measure, for at least two of the antennas (102:1, 102:2) of the antenna array (101), a temperature value of the transmit path (103:1, 103:2) for each of the at least two antennas; and

a processing unit (106) and a memory (108), said memory containing instructions (109) executable by said processing unit, whereby the antenna array control device is operative to:

acquire at least one of a first delay and phase-shift value corresponding to the measured temperature value of a first (103:1) of the at least two transmit paths;

acquire at least one of a second delay and phase-shift value

corresponding to the measured temperature value of a second (103:2) of the at least two transmit paths; and to

apply delay and/or phase-shift to signals of at least one of the at least two transmit paths (103:1, 103:2) according to the acquired first and second delay and/or phase-shift values in order to align the signals of the first transmit path (103:1) with the signals of the second transmit path (103:2) in terms of delay and/or phase-shift.

11. The antenna array control device of claim 10, further being operative to, when acquiring the first and second delay/and or phase shift value:

acquire the first and second delay/and or phase shift value from a look up table storing, for each of a plurality of temperature values, a

corresponding delay and/or phase-shift value indicating to which extent signals transmitted in the at least two transmit paths (103:1, 103:2) are delayed and phase-shifted.

12. The antenna array control device of claim 10, further being operative to, when acquiring the first and second delay/and or phase shift value: acquire the first and second delay/and or phase shift value from a stored mathematical relationship between temperature and delay and/or phase-shift value indicating to which extent signals transmitted in the at least two transmit paths are delayed and/or phase-shifted for a given temperature value.

13. The antenna array control device of claim 10, further being operative to, when acquiring the first and second delay/and or phase shift value:

inject, in each of the at least two transmit paths (103:1, 103:2), an antenna calibration, AC, signal;

measure, in at least one of the at least two transmit paths, relative delay and/or phase-shift that the AC signal is subjected to with respect to the AC signal of a selected reference transmit path of the at least two transmit paths after having traversed each transmit path; and to

extrapolate, based on the measured relative delay and/or phase-shift, a corresponding delay and/or phase-shift value indicating to which extent signals transmitted in the at least two transmit paths (103:1, 103:2) are delayed and phase-shifted.

14. The antenna array control device of claim 13, further being operative to, when measuring the delay and/or phase-shift that the AC signal is subjected to in each transmit path:

compare the AC signal having traversed each transmit path with the injected AC signal.

15. The antenna array control device of claims 13 or 14, the AC signal being a baseband signal.

16. The antenna array control device of any one of claims 10-15, wherein the temperature of each transmit path is measured at a radio frequency, RF, mixer arranged in said each transmit path.

Description:
CONTROLLING AN ANTENNA ARRAY TECHNICAL FIELD

The invention relates to a method of controlling an antenna array, an antenna array control device, a corresponding computer program, and a

corresponding computer program product.

BACKGROUND

An antenna array comprises a set of antennas acting as a single antenna for transmitting and receiving radio signals. Each antenna comprises a transmit (Tx) path for transmitting signals via the antenna, and a receive (Rx) path for receiving signals via the antenna. Each antenna array thus comprises a plurality of Tx paths and a plurality of Rx paths carrying radio signals for transmission and reception, respectively.

Antenna arrays add value to communication systems for many reasons.

Firstly, an antenna array can achieve a narrower beam for

transmitted/received radio signals and thus higher Tx and Rx gain, which increases coverage area without increasing Tx and Rx power. This kind of beam forming is particularly beneficial for mobile terminals which have relatively strict limitations on battery power supply. Secondly, antenna arrays can be also used in multiple-input multiple-output (MIMO) transmissions by utilizing radio propagation path diversity to increase communication throughput.

Antenna array have been already widely used in wireless communication systems. In 4G/5G cellular communication systems, antenna-array based technologies such as beamforming and MIMO significantly increase cell throughput, capacity, and coverage.

In general, the higher the number of antennas in the array, the higher the beamforming gain, and the higher the throughput for the MIMO system. In practice, the number of antennas can be 2, 4, 8, 16, 32, 64, 128 or 256 in a 4G/5G communication system for a base station. In order to attain a high beamforming performance, the number of antennas should generally be higher than 32.

In order to attain high performance in an antenna array system, radio signals travelling in the multiple Tx paths should be subjected to the same path delay and phase shift, such that the radio signals of the multiple Tx paths are aligned in terms of delay and phase shift upon reaching the respective antenna of the array for transmission. Correspondingly, the radio signals travelling in the Rx paths should be aligned in terms of delay and phase shift upon exiting the antenna array for transport to a recipient, being for instance a base station at which the antenna array system is arranged.

However, in the Tx/Rx paths, the radio signals will traverse radio frequency (RF) components such as mixers, analog filters, power amplifiers, digital-to- analog converters (DACs), analog-to-digital converters (ADC) and printed circuit board (PCB) signal traces, etc. Because the components in different Tx/Rx phase are not completely identical in characteristic, and the different Tx/Rx paths may be subject to different temperatures due to variation in power dissipation and cooling, the signal passing through the components is subjected to different delay and phase shift. Further, the delay and phase shift are time-varying, mainly due to varying temperature of the components.

For example, the electrical characteristic of the PCB traces varies with temperature. For a PCB trace transporting a clock signal, this will give rise to a change of clock phase, which in turn induces phase shifts in Tx/Rx paths.

The separation between two adjacent Tx/Rx paths on a PCB is typically around 5-10 cm, meaning that a first path may be subjected to a first temperature while a second path is subjected to a second temperature. In practice, a difference in temperature between two paths of io°C may result in a change in phase of up to 15 degrees for two identical radio signals travelling in the first and second paths, depending on parameters such as operating frequency and specific components that are being used. Hence, there is a risk that temperature differences between different Tx/Rx paths in an antenna array cause misalignment of the radio signals in the Tx/Rx paths, thereby affecting the performance of the antenna array.

SUMMARY

An objective of the invention is thus to solve, or at least mitigate, the problems in the art and thus to provide a method of controlling an antenna array such that any misalignment in delay and/or phase of radio signals travelling in individual antenna paths of the antenna array is reduced or even eliminated.

This object is attained in a first aspect of the invention by a method of controlling an antenna array comprising a plurality of antennas, where each antenna in the array comprises an individual transmit path for transmitting signals via the antenna. The method comprises measuring, for at least two of the antennas of the antenna array, a temperature value of the transmit path for each of the at least two antennas, acquiring at least one of a first delay and phase-shift value corresponding to the measured temperature value of a first of the at least two transmit paths, acquiring at least one of a second delay and phase-shift value corresponding to the measured temperature value of a second of the at least two transmit paths, and applying delay and/or phase- shift to signals of at least one of the at least two transmit paths according to the acquired first and second delay and/or phase-shift values in order to align the signals of the first transmit path with the signals of the second transmit path in terms of delay and/or phase-shift.

This object is attained in a second aspect of the invention by an antenna array control device configured to control an antenna array comprising a plurality of antennas, where each antenna in the array comprises an individual transmit path for transmitting signals via the antenna. The antenna array control device comprises temperature sensors configured to measure, for at least two of the antennas of the antenna array, a temperature value of the transmit path for each of the at least two antennas. The antenna array control device further comprises a processing unit and a memory, which memory contains instructions executable by the processing unit, whereby the antenna array control device is operative to acquire at least one of a first delay and phase-shift value corresponding to the measured temperature value of a first of the at least two transmit paths, acquire at least one of a second delay and phase-shift value corresponding to the measured temperature value of a second of the at least two transmit paths, and to apply delay and/or phase- shift to signals of at least one of the at least two transmit paths according to the acquired first and second delay and/or phase-shift values in order to align the signals of the first transmit path with the signals of the second transmit path in terms of delay and/or phase-shift.

In order to compensate for undesired differences in delay and/or phase shift of signals transferred via transmit (Tx) paths of an antenna array system caused by temperature differences in the Tx paths, an antenna array control device is provided.

The antenna array control device comprises temperature sensors for measuring the temperature at an appropriate location of each Tx path, such as at a radio frequency (RF) mixer. Alternatively, the antenna array control device may comprise interface circuitry for receiving measured temperature values from the antenna array, the measured temperature values

representing the respective temperature at an appropriate location of each Tx path. Typically, the relationship between the measured temperature and the delay and/or phase shift that a Tx path signal is subjected to is linear, at least within a temperature range to which an antenna array is subjected to under typical operating conditions.

Thus, for each measured temperature in each Tx path, the antenna array control device acquires a delay and/or phase-shift value indicating to which extent signals transmitted in each path are delayed and phase-shifted the measured temperature value.

Advantageously, the acquired delay and/or phase-shift values are used to adjust delay and/or phase-shift of one or more of the Tx paths such that the phase and/or delay of the radio signals of the Tx paths are aligned upon reaching the antenna array for transmission over the air interface.

In an embodiment, the delay/and or phase shift values are acquired from a look-up table storing, for each of a plurality of temperature values, a corresponding delay and/or phase-shift value indicating to which extent signals transmitted in the at least two transmit paths are delayed and phase- shifted, which corresponding delay and/or phase-shift values thereafter are applied to the Tx paths to align the signals.

In another embodiment, the delay/and or phase shift values are acquired from a stored mathematical relationship between temperature and delay and/or phase-shift value indicating to which extent signals transmitted in the at least two transmit paths are delayed and/or phase-shifted for a given temperature value which corresponding delay and/or phase-shift values thereafter are applied to the Tx paths to align the signals. For instance, such mathematical relationship may be expressed as:

Delay = a x Temp + b.

Hence, for each measured temperature Temp, a corresponding delay can be computed (based on parameters a and b which have been determined during calibration/manufacturing). In yet another embodiment, the delay/and or phase shift values for each measured temperature are extrapolated. In such an embodiment, an antenna calibration (AC) signal is injected in each Tx path, and a relative delay and/or phase-shift that the AC signal is subjected to with respect to the AC signal of a selected reference Tx path after having traversed said each transmit path is measured for each Tx path. Thereafter, based on the measured relative delay and/or phase-shift, a corresponding delay and/or phase-shift value is extrapolated indicating to which extent signals transmitted in the at least two transmit paths are delayed and phase-shifted. In a third aspect of the invention, a computer program is provided

comprising computer-executable instructions for causing an antenna array control device to perform steps recited in the method of the first aspect when the computer-executable instructions are executed on a processing unit included in the antenna array control device.

In a fourth aspect of the invention, a computer program product is provided comprising a computer readable medium, the computer readable medium having the computer program of the third aspect embodied thereon.

Further embodiments will be discussed in the following.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described, by way of example, with reference to the accompanying drawings, in which:

Figure l schematically illustrates an antenna array system in which

embodiments of the invention may be implemented;

Figure 2 illustrates a relationship between phase shift and temperature in an antenna array system at a particular frequency;

Figure 3 illustrates an antenna array control device implemented in an antenna array system, according to an embodiment;

Figure 4 shows a flowchart illustrating a method of controlling an antenna array according to an embodiment; Figure 5 illustrates an antenna array control device implemented in an antenna array system according to another embodiment; and

Figure 6 illustrates an antenna array control device according to an

embodiment.

DETAILED DESCRIPTION

The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

Figure l schematically illustrates an antenna array system too in which embodiments of the invention may be implemented. As has been discussed, the antenna array system too comprises an antenna array tot formed by a set of antennas 102:1, 102:2, ..., 102:N, where N in practice preferably amounts to 32 or more.

Figure 1 illustrates a transmit section of the antenna array system 100 via which radio signals are transported and transmitted via the array 101, from a device 104 such as e.g. a radio base station, e.g., a NodeB or an eNodeB, and correspondingly the system comprises a receive section (not shown in Figure 1), via which radio signals are transported to the radio base station 104, after having been received via the array 101.

Each antenna 102:1, 102:2, ..., 102:N thus comprises a Tx path 103:1, 103:2,

..., 103:N for transmitting radio signals via the antenna array 101. In each Tx path, the radio signals will traverse numerous components such as mixers, analog filters, PCB signal traces, etc. This is also the case for the Rx paths. For these components, illustrated functionally by components Txi, Tx2,

TxN, the delay and/or phase shift that the radio signals travelling in each path 103:1, 103:2, ..., 103:N are subjected to may vary with temperature.

Figure 2 exemplifies a relationship between phase shift and temperature in an antenna array system 100 at a particular frequency, which relationship may be exploited in an embodiment to reduced or even eliminate

misalignment in delay and/or phase of radio signals travelling in individual antenna paths of the antenna array. As can be seen, the relationship is approximately linear, and a change in temperature of around io°C results in a change in phase of the radio signal of about 13 degrees.

Hence, as previously has been discussed, the distance between two adjacent Tx/Rx paths on a PCB is typically around 5-10 cm, meaning that components of a first path may be subjected to a first temperature while components of a second path are subjected to a second temperature. As a consequence, two signals which are identical upon being transmitted over the Tx paths may due to temperature differences in the components be misaligned in phase when reaching the antenna array 101. The difference in temperature between two given paths may be caused for instance by distance to a heat source such as a power amplifier or a power supply, or different cooling/ventilation conditions for different paths. Hence, the physical location of a component will affect its electrical characteristics.

Figure 3 illustrates the antenna array system too with an antenna array control device implemented according to an embodiment. As can be seen, the antenna array control device comprises temperature sensors used for measuring a temperature of each Tx path. In this particular example, one temperature sensor 105:1, 105:2, ..., ios:N is implemented for each Tx path 103:1, 103:2, ..., 103:N. Further, if two or more paths are located close to each other on the PCB of the antenna array system 100, it may be envisaged that one temperature sensor is used for measuring the temperature of all said two or more paths. The temperature may also be measured at one or more components in each path. For instance, a temperature sensor may be arranged close to the power amplifier or an RF mixer in each path.

The antenna array control device further comprises a controller 106, such as a microprocessor (mR), configured to collect the measured temperature values and determines if the phase and/or delay of one or more of the Tx paths are to be adjusted, as well as a magnitude of such adjustment.

The controller 106 applies phase-shift and/or delay to radio signals of the 103:1, 103:2, ..., i03:N by controlling a delay/phase-shift element (DP) of each path. For instance, a delay buffer can be used to adjust the delay, while an equalizer can be used to adjust phase-shift.

Hence, the controller 106 adjusts the phase-shift and/or delay applied to the radio signals transported via the Tx paths 103:1, 103:2, ..., 103:N by controlling the corresponding delay/phase-shift element 107:1, 107:2,... , 107:N included in the antenna array control device such that the phase and/or delay of the radio signals are aligned upon reaching the antenna array 101 for transmission over the air interface.

Figure 4 shows a flowchart illustrating a method of controlling an antenna array according to an embodiment.

For brevity, it is assumed in this exemplifying embodiment that the antenna array 101 comprises a first and a second antenna 102:1, 102:2.

In a first step S101, the first temperature sensor 105:1 measures the temperature of the first Tx path 103:1, while the second temperature sensor 105:2 measures the temperature of the second Tx path 103:2.

In one embodiment, the controller 106 stores a look-up table comprising, for each of a plurality of temperature values, a corresponding delay and/or phase-shift value indicating to which extent radio signals transmitted in the Tx paths are delayed and/or phase-shifted for each temperature value in the look-up table as compared to a reference temperature value. For instance, with reference to the exemplifying graph of Figure 2, the look-up table could have the appearance of:

Tablei. Look-up table stored at the controller.

The look-up table may in practice have a higher resolution comprising a greater number of values with a granularity of 5°C or less. However, it is also possible to use a look-up table such as that shown in Table 1, where interpolation is performed for creating data points other than those included in the table. Further, it may be envisaged that a separate look-up table is stored for the delay values, or that a combined delay and phase-shift value is listed for each temperature value.

In another embodiment, it is envisaged that the controller 106 stores a mathematical relationship between the measured temperature and the corresponding delay and/or phase-shift value.

Generally, the relationship is linear and may thus be mathematically expressed as:

Phase-shift = a x Temp + b.

Again with reference to the graph of Figure 2, showing actually measured values for an antenna array the phase-shift-temperature relationship may in a practical example be mathematically expressed as: Phase-shift = - 1.35 x Temp + 79.2 (1)

A corresponding linear relationship can be derived for delay versus temperature. It should be noted the equation (1) is exemplifying only, and each individual antenna array system is likely to present its own individual phase-shift/delay-temperature relationship.

With the controller 106 storing such a mathematical relationship, any measured temperature value can advantageously be expressed as a

corresponding delay and/or phase-shift value.

The look-up table(s) and/or the mathematical relationship(s) may be compiled during manufacturing of the antenna array system 100, during a separate calibration procedure, or during normal operation, as is described further below.

Now, after the temperature of each Tx path 103:1, 103:2 has been measured in step S101, the controller 106 acquires in step S102 at least one of a first stored delay and phase-shift value corresponding to the measured

temperature value of the first Tx path 103:1. In this particular exemplifying embodiment, the controller 106 acquires a phase-shift value.

Assuming that the measured temperature value of the first Tx path 103:1 is 20°C, then the phase-shift is 52 degrees using the example of Table 1.

Further, the controller 106 acquires a stored phase-shift value in step S103 corresponding to the measured temperature value of the second Tx path 103:2. If the measured temperature is, say, 24°C, the phase-shift is 45 degrees using the example relationship of equation (1).

The controller 106 thus concludes that the phase of the radio signals travelling in the second Tx path 103:2, having a phase-shift of 45 degrees, should be phase-shifted another 7 degrees for alignment with the radio signals travelling in the first Tx path 103:1 having a phase-shift of 52 degrees. Accordingly, the controller 106 controls the second delay/phase-shift element 107:2 in step S104 to apply a 7-degree phase-shift to the radio signals travelling in the second Tx path 103:2. Advantageously, the phase of the radio signals carried in the second Tx path 103:2 is aligned with the phase of the radio signals carried in the first Tx path 103:1 - i.e. both signals now have a phase-shift of 52 degrees - when the radio signals reaches the antenna array 101 for transmission over the air interface.

It should be noted that both the signals travelling in the first Tx path 103:1 and the signals travelling in the second Tx path 103:2 may be phase-shifted such that the 7-degree difference is eliminated. For instance, the first Tx path may be shifted 3 degrees, while the second Tx path is shifted 10 degrees, if such control of the delay/phase-shift elements would be more appropriate.

Further noted is that the example flowchart of Figure 4 illustrates

measurement of temperature in two Tx paths, while in a practical case the antenna array system 100 may comprise 32 or more paths. Hence, in such a scenario, the temperatures in 32 different Tx paths are measured, and as a consequence the delay and/or phase shift of all of these paths (or at least almost all of the paths) may be adjusted for aligning all 32 radio signals transmitted. Generally, one reference path is selected, for instance the path having the greatest delay or the smallest delay, and then the remaining paths are adjusted in delay such that they all attain this greatest/smallest delay and thus are aligned relatively to each other. It may be envisaged that the signals of a selected set of Tx paths are adjusted in terms of delay/phase-shift in order to be aligned.

Advantageously, by continuously measuring the temperature of the Tx paths, and adjusting the delay and phase-shift of the signals in the TX paths according to the previously discussed look-up tables or stored mathematical relationships, it is possible for the controller 106 to maintain the radio signals in alignment with respect to delay and/or phase, even with (rapid) changes in temperature. Figure 5 illustrates in more detail components comprised in an antenna array system 200 with an antenna array control device implemented according to a further embodiment.

As can be concluded from the embodiment described hereinbelow with reference to Figure 5, as an alternative to using a look-up table as was discussed with reference to Table 1, or a mathematical relationship as was discussed with reference to equation (1), the antenna array control device may utilize extrapolation in order to derive delay and/or phase-shift values for a given temperature to be applied for aligning the signals in the Tx paths.

As can be seen, the illustrated antenna array system 100 comprises four Tx paths. As can be seen in the schematic representation of the antenna array system 200, each Tx path comprises a delay element 201 for adjusting the delay of each path, an equalizer 202 for adjusting the phase-shift of each path, a digital up converter 203 (DUC) for increasing the sampling rate of the signals transported on each path, and DACs 204 for converting the digital signals into analog form.

Further, as a part of the antenna array control device according to an embodiment, temperature sensors 205 are arranged in each Tx path for measuring temperature values collected by the controller 206.

Moreover, an RF coupler 207 is arranged in each path for obtaining a sample of the signals transported in each Tx path, which sample is collected by the controller 206.

In order to establish, or update, the relationship between temperature and delay and/or phase shift during operation of the antenna array, a so called antenna calibration (AC) signal is injected in each Tx path, in this particular example at the DUCs 203, as is illustrated in Figure 5. The AC signal is typically at baseband. The AC signal is also fed to the controller 206

The injected AC signal transverses each Tx path and is coupled by the RF coupler 207 at the and of each Tx path to the controller 206, where the delay and/or phase-shift of the AC signal in each Tx path is measured by

comparing the AC signal having traversed each Tx path with the

corresponding AC signal injected at the DUCs 207.

The controller 206 is in Figure 5 illustrated to comprise functional blocks AC Rx 208, AC algo 209 and Extrapolator 210.

The AC Rx block 208 down converts the RF coupled AC signal and digitizes the AC signals with an ADC for further transmission to the AC algo block 209, which also receives the originally injected AC signal.

The AC algo block 209 compares the RF coupled AC signal with the originally injected AC signal and computes the delay and/or phase-shift that the signals of each Tx path are subjected to.

For each Tx path, the AC algo block 209 thus measures relative delay/phase- shift Dt/Df with respect to a selected reference Tx path using the AC signal and forwards the measured relative delay/phase-shift to the Extrapolator 210. For instance, the Tx path having the greatest phase-shift is used as reference Tx path for the remaining Tx paths.

Assuming for instance that the phase-shift of a target Tx path is measured to be 5 degrees after having compared the injected AC signal to the coupled AC signal for the target Tx path, and that the phase-shift of the selected reference Tx path is measured to be 9 degrees; the relative phase-shift is then 9-5 = 4 degrees. Hence, the phase of the signals transported in the target Tx path will have to be shifted another 4 degrees in order to be aligned with the signals transported in the selected TX path.

The Extrapolator 210 further collects the measured temperature values T k of each Tx path from the temperature sensors 205 and associates a measured temperature value T k of each Tx path with the corresponding relative delay/phase-shift Dt Df ί and extrapolates (assuming a linear relationship based on a set of measured values as previously discussed) the delay and/or phase-shift Df k to be applied to the signals transported on each Tx path for a given temperature. As is understood, assuming that the Tx path having the greatest delay is used as reference Tx path for the remaining Tx paths, that particular Tx path will not be adjusted in terms of delay, while the delay of the three remaining Tx paths will be adjusted.

Hence, controller 206 controls the delay element 201 to apply the

appropriate delay to the signals of each path at stipulated by the extrapolated delay value Dti , and/or controls the equalizer 202 to apply the appropriate phase-shift to the signals of each path at stipulated by the extrapolated phase-shift value D (¾, in order to align the signals with respect to delay and phase-shift of the Tx paths upon reaching a respective antenna of the antenna array 200.

As can be concluded from the embodiment described hereinabove with reference to Figure 5, as an alternative to using a look-up table as was discussed with reference to Table 1, or a mathematical relationship as was discussed with reference to equation (1), the antenna array control device may utilize extrapolation in order to derive delay and/or phase-shift values for a given temperature to be applied for aligning the signals in the Tx paths.

In the following, the extrapolation will be discussed in more detail. In the Extrapolator 210, the processes of calculating and D (¾ are the same. For brevity, only the extrapolation of the relative phase-shift D (¾ is described in the following.

First a baseline function representing phase-shift Df versus temperature t is created (assuming four Tx paths):

Hence, the phase-shift D is measured for all four Tx paths at the same temperature t r , typically during manufacturing of the array. At time k+i, the Extrapolator 210 already has access to historical data, i.e. the relative phase-shift Aq>(t rk , t tk ) between a target Tx path and a reference Tx path, where t rk and t tk are temperatures of the reference Tx path and the target Tx path, respectively, measured at time k. During operation of the antenna array, the temperatures in different Tx paths may deviate from each other due to variance in fan and heat radiation conditions. The measured temperature difference among Tx paths is in the range of 0-20 °C, during power-up of the antenna array.

In the following, extrapolation of the deviation of the phase-shift from the baseline Df (t based on historical data will be discussed.

At time k+i, the Extrapolator 210 receives temperature measurements trk+i, ttk+i. Further, if the Extrapolator 210 receives new updates from the AC algo block 209, the updates are registered as Acp(t, k+ i , ttk+i) and control signals are sent to the equalizers 203 such that the signals of the Tx paths are aligned based on the updated relative phase-shift D<|¾ +i .

If no updates are available at the AC algo block 209, the Extrapolator 210 performs extrapolation by computing an estimate A<p(t rkf l , t mf l ) of the relative phase-shift as follows:

1) Calculate 2) Calculate

3) Calculate ,¾ (t rk+ 1 , t tfc + 1 ) = Aq>(t rk , t tk ) + d 1 + d 2 .

Similar to the flowchart shown in Figure 4, after the Extrapolator 210 has acquired the appropriate phase-shift values to apply to one or more the Tx paths (cf. steps S102 and S103) by performing extrapolation, the

Extrapolator 201 sends control signals to the equalizers 203 such that the signals of the Tx paths are aligned based on the estimated relative phase- shift Ac( k+i to be applied to the TX paths (cf. step S104) as stipulated by the computed estimate A^(t Tk tlr £tfe†1 ).

Figure 6 illustrates an antenna array control device 110 according to an embodiment. Some of steps of the method performed by the antenna array control device 110 configured to control an antenna array comprising a plurality of antennas, where each antenna in the array comprises an individual transmit path for transmitting signals via the antenna are in practice performed by a processing unit 106 embodied in the form of one or more microprocessors arranged to execute a computer program 109 downloaded to a suitable storage volatile medium 108 associated with the microprocessor, such as a Random Access Memory (RAM), or a non-volatile storage medium such as a Flash memory or a hard disk drive. The processing unit 106 is arranged to cause the antenna array control device 110 to carry out the method according to embodiments when the

appropriate computer program 109 comprising computer-executable instructions is downloaded to the storage medium 108 and executed by the processing unit 106. The storage medium 108 may also be a computer program product comprising the computer program 109. Alternatively, the computer program 109 may be transferred to the storage medium 108 by means of a suitable computer program product, such as a Digital Versatile Disc (DVD) or a memory stick. As a further alternative, the computer program 109 may be downloaded to the storage medium 108 over a network. The processing unit 106 may alternatively be embodied in the form of a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), etc.

The antenna array control device 110 comprises measuring module 120, for instance in the form of temperature sensors 105, configured to measure, for at least two of the antennas of the antenna array, a temperature value of the transmit path for each of the at least two antennas, a first acquiring module 130 adapted to acquire at least one of a first delay and phase-shift value i8 corresponding to the measured temperature value of a first of the at least two transmit paths, a second acquiring module 140 adapted to acquire at least one of a second delay and phase-shift value corresponding to the measured temperature value of a second of the at least two transmit paths, and applying module 150 adapted to apply delay and/or phase-shift to signals of at least one of the at least two transmit paths according to the acquired first and second delay and/or phase-shift values in order to align the signals of the first transmit path with the signals of the second transmit path (103:2) in terms of delay and/or phase-shift. It is noted that the first acquiring module 130 and the second acquiring module 140 may be implemented by means of a single acquiring module.

The modules 130, 140 and 150 may comprise communication interface(s) for receiving and providing information, and further a local storage for storing data, and may (in analogy with that previously discussed) be implemented by a processor 106 embodied in the form of one or more microprocessors arranged to execute a computer program 109 downloaded to a suitable storage medium 108 associated with the microprocessor, such as a RAM, a Flash memory or a hard disk drive.

In a first embodiment, the memory 108 may comprise the look-up table illustrated with reference to Table 1.

In a second embodiment, the memory 108 may comprise the mathematical relationship of equation (1).

In a third embodiment, the memory 108 may comprise any data used in the extrapolation process described with reference to Figure 5.

The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.