FIELD OF THE INVENTION

[0001] This invention relates to the technical field of telecommunications and in particular to an array for receiving and processing electromagnetic radio-frequency signals .

STATE OF THE ART

[0002] The state of the art knows of array antennas that comprise one or more arrays for receiving and processing electromagnetic radio-frequency signals.

[0003] For example, radar systems are known that include four active planar phased array antennas, each installed on a face of a ship's mast substantially shaped like a truncated pyramid with a quadrangular base.

[0004] Thanks to their ability to quickly change the direction of the beam in a controlled manner, active radars of the phased-array type allow a vehicle such as a military vessel to use a single radar system for the detection and monitoring of surfaces (for example to locate vessels), monitoring the airspace (to locate aircraft and missiles), guiding missiles and controlling artillery devices.

[0005] The active planar phased array radars of the state of the art so far installed in vehicles such as military vessels are typically monostatic radars, since each array antenna is composed of a plurality of modules, both receiving and transmitting (TX/RX modules), each of which it is switched sequentially in time between the two operating modes, respectively transmitting and receiving. For this reason, the aforesaid phased array radar systems of the prior art are particularly expensive. It is also noted that, in the configuration that provides for four active planar phased array antennas, each installed on one face of a ship's mast substantially shaped like a truncated pyramid with a quadrangular base, such radar systems do not exhibit uniform performance over the entire azimuthal plane, as such performance is degraded particularly in the directions located in front of the edges of the truncated pyramid. In other words the aforesaid radars of the prior art present scan losses in the horizontal plane .

[0006] Moreover, the radars of the prior art each constitute a standalone product designed entirely or almost entirely from scratch and it is not possible to reuse significant portions developed for one product to make a different product.

[0007] The purpose of this description is to make available an array for receiving electromagnetic radio- frequency signals that allows realising receiving antennas or receiving systems, for example but not exclusively of bistatic radar systems that, having a modular architecture, can be designed at lower cost than the antennas and systems of the prior art.

[0008] This purpose is achieved through an array for receiving and processing electromagnetic radio-frequency signals as defined in general in claim 1. Preferred and advantageous embodiments of the array for receiving and processing electromagnetic radio-frequency signals are defined in the appended dependent claims.

[0009] The invention will be better understood from the following detailed description of a particular embodiment, provided by way of example and, therefore, in no way limiting, in relation to the accompanying drawings, which are briefly described in the next paragraph .

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 shows a schematic view of an exemplary embodiment of a receiving system comprising an array for receiving and processing electromagnetic radio-frequency signals and an external control unit of the array operatively to the array.

[0011] Figure 2 shows a block diagram of a part of the receiving and processing array of Figure 1. [0012] Figure 3 shows a perspective view of an enlarged part of the receiving and processing array of Figure 1.

[0013] Figure 4 shows a first embodiment of an antenna comprising a plurality of receiving and processing arrays of Figure 1.

[0014] Figure 5 shows a second embodiment of an antenna comprising a plurality of receiving and processing arrays of Figure 1.

[0015] Figure 6 shows an embodiment of a bistatic radar comprising a transmitting antenna and comprising a system for receiving and processing radar echo signals comprising a plurality of receiving and processing arrays of Figure 1.

DETAILED DESCRIPTION

[0016] Figure 1 shows a schematic view of an exemplary embodiment of a system for receiving and processing electromagnetic radio-frequency signals comprising an array for receiving and processing 1 electromagnetic radio-frequency signals, and an external control unit 40 of the receiving and processing array 1 operatively connected to the array 1. In the particular example shown in figure 1, the receiving and processing array 1 is operatively connected to the external control unit 40 by means of an electric supply line LI through which the external control unit 40 is such as to provide the receiving and processing array 1 a supply signal of the receiving and processing array 1 itself. In this example, the receiving and processing array 1 is operatively connected to the external control unit 40 by means of a reception channel C2 and a transmission channel C3, respectively provided to allow the receiving and processing array 1 to receive a control signal from the external control unit 40 and to transmit a data signal to the external control unit 40. The reception channel C2 and transmission channel C3 could be two channels of a same bidirectional transmission medium, such as for example an optical fibre or, alternatively, could be separate channels of different transmission means, such as for example a first optical fibre and a second distinct optical fibre or a first bundle of optical fibres and a second bundle of optical fibres. As will be clarified below, the reception channel C2 and transmission channel C3 may also be wireless channels, for example, two channels on carrier frequencies different from each other or two channels on a same carrier with a system for sharing the available band implemented by means of time-division or code division multiplexing, etc.

[0017] According to an embodiment, the external control unit 40 is connected to a plurality of receiving and processing arrays 1 of the type described above, which together constitute, along with the external control unit 40, a modular system for receiving and processing electromagnetic radio-frequency signals, for example the receiving and processing system of a bistatic radar and, thus, a system adapted and configured to receive and process radar echo signals. In said modular receiving and processing system, the individual receiving and processing arrays 1 are the modules.

[0018] The array 1 for receiving and processing electromagnetic radio-frequency signals comprises a plurality of antenna elements 10 adapted to receive electromagnetic radio-frequency signals and convert them into corresponding analog electrical signals. According to an embodiment, the antenna elements 10 are waveguide antenna elements, for example in open or loaded waveguide, and each of them presents a resonant cavity defined inside a common support body 2,12 and a ramp or step impedance matching element inserted inside the resonant cavity to protrude inside of this.

[0019] Preferably, the support body of 2,12 is made of an electrically conductive metallic material, for example aluminium or an aluminium alloy, and comprises a front part 2', inside of which the antenna elements 10 are defined, and a rear part 2'', which is a chassis that has inside it one or more seats for housing electronic circuits and components of the receiving and processing array 1.

[0020] With reference to Figure 2, the receiving and processing array 1 comprises a plurality of frequency- conversion modules 21 adapted to convert respective analog electrical signals into respective intermediate- frequency or base-band analog electrical signals. Each of the frequency-conversion modules 21 has a first input operatively coupled to a respective antenna element 10 and a second input adapted to receive a frequency- reference signal. In the example shown in Figure 2, the frequency conversion modules 21 are analog mixers each having the first input connected to the output of a low- noise amplifier 20 connected in series between the output of the antenna element 10 and the first input of the conversion module 21.

[0021] According to an embodiment, the electromagnetic radio-frequency signals received by the antenna elements 10 are for example signals having a carrier frequency equal, or approximately equal, to 10 GHz and the frequency conversion modules 21 are such as to convert such analog electrical signals into analog signals having a carrier frequency equal, or approximately equal, to 1 GHz. In this case, the frequency-reference signal is a stable oscillator signal having a frequency equal, or approximately equal to, 1 GHz. In an alternative embodiment, the radio-frequency conversion modules 21 are such as to produce base-band analog electrical signals in output. From now on, without thereby introducing any limitation, reference will be made to the specific example in which the frequency conversion modules 21 are such as to produce intermediate-frequency analog electrical signals in output .

[0022] In addition, the receiving array 1 comprises a plurality of analog to digital conversion modules 22 adapted to receive a synchronisation signal and a control signal and to convert the analog electrical intermediate-frequency or base-band signals (from now on called intermediate-frequency) produced in output from the frequency conversion modules 21 into digital samples .

[0023] For example, each of the aforesaid analog-digital conversion modules 22 has an input connected to the output of the frequency conversion modules 22 and comprises an analog-digital converter and the synchronisation signal is a clock signal for the analog- digital converter while the control signal is a signal that for example controls the analog-digital conversion process, for example that controls the start and the end of the analog-digital conversion process for the acquisition of a vector of digital samples.

[0024] The receiving and processing array 1 also comprises a fibre-optic or radio transmission interface 23 for the transmission to the external control unit 40 of the digital samples produced in output from the analog-digital conversion modules 22 or of digital data obtained from a processing of said digital samples. As was therefore already explained with reference to Figure 1, by means of the transmission interface 23 and transmission channel C3, the receiving and processing array 1 is such as to send to the external control unit 40 a data signal that contains therefore said digital samples or contains the digital data obtained from a digital processing of the aforesaid digital samples.

[0025] The receiving and processing array 1 also comprises a fibre-optic or radio reception interface 24 through which the receiving and processing array 1 is adapted to receive the control signal from the external control unit 40, in the example by means of the reception channel C2.

[0026] According to a possible embodiment, the transmission interfaces 23 and reception interfaces 24 are radio interfaces and are part of a Wi-Fi modem. [ 0027 ] According to an alternative embodiment to that described above, the transmission interfaces 23 and reception interfaces 24 are fibre optic interfaces. In this embodiment, the transmission interface 23 comprises an LED or a laser diode and the reception interface 24 comprises a photodetector .

[ 0028 ] In the particular example shown, the receiving and processing array 1 also comprises a power supply module 35 operatively connected to the power supply line LI. This power supply module 35 is responsible for providing the electrical power supply to the receiving and processing array 1 and in particular to electronic and/or optoelectronic components of this that require a supply voltage for their operation.

[ 0029] The receiving and processing array 1 comprises a synthesis unit 25 adapted to process the control signal received by means of the reception interface 24 to synthesise, from the latter, the frequency-reference signal for the frequency conversion modules 21, the synchronisation signal and the control signal for the analog-digital conversion modules 22.

[ 0030 ] The receiving array 1 comprises a distribution network 26,27 adapted to supply the frequency-reference signal to the plurality of frequency-conversion modules 21. For example, the distribution network 26,27 comprises a power divider 26 operatively connected to the synthesis unit 25 and a plurality of electrical connection lines 27 each connected between the power divider 6 and a respective frequency conversion module 21.

[0031] The receiving and processing array 1 also comprises electrical connection elements 28,29 adapted to provide the synchronisation signal and the control signal to the plurality of analog-digital conversion modules 22.

[0032] In the particular example shown in Figure 2, in addition to the analog-digital conversion modules 22, each provided at the output of a respective frequency conversion module 21, the receiving and processing array 1 comprises common digital processing modules 31 adapted to receive in input the digital samples provided in output from a plurality of analog-digital conversion modules 22 and adapted and configured to carry out in parallel several operations on said digital samples, such as for example digital filtering or decimation operations of digital samples or base-band conversion operations in the case in which the frequency conversion modules 22 are such as to produce in output intermediate-frequency electrical analog signals. In addition, in the particular example shown in Figure 2, the synchronisation and control signals are sent to the analog-digital conversion modules 22 by means of the common processing modules of 31, for example by means of a connection bus 28 operatively connected between the synthesis unit 25 and each of the common processing modules 31 and by means of a bidirectional connection bus 29 connected between each of the common processing modules 31 and the respective analog-digital conversion modules 22. On such bidirectional connection buses, the signals carrying the digital samples from the modules 22 to the respective common modules 31 travel in one direction and the aforesaid synchronisation and control signals travel in the opposite direction.

[0033] According to a possible embodiment, each receiving and processing array 1 comprises sixty-four antenna elements 10, sixty-four frequency conversion modules 21, sixty-four analog-digital conversion modules 22 and eight common digital processing modules 31, each of which it is operatively connected to four respective analog-digital conversion modules 22.

[0034] According to an embodiment, the receiving and processing array 1 comprises a full digital beam-forming processing module 30 adapted to receive in input the digital samples supplied at output from the analog- digital conversion modules 22, or from the common processing modules 31, and to process them numerically to calculate weighted linear combinations among digital samples produced in output from different analog-digital conversion modules 22 for the digital synthesis of one or more reception beams. In the particular example shown in Figure 2, the full digital beam-forming processing module 30 is such as to receive in input signals supplied in output from the common processing modules 31, it being understood that said processing module 30, in an alternative embodiment, could receive directly in input signals supplied in output from the analog-digital conversion modules 22.

[0035] According to an advantageous embodiment, the full digital beam-forming processing module 30 is adapted and configured to receive in input of weighting coefficients for the calculation of the aforesaid linear combinations. Preferably, the aforesaid mentioned weighting coefficients are obtained from the synthesis unit of 25 by processing the control signal received from the reception interface 24 to synthesise, starting from this, a control signal of the full digital beam- forming processing module 30.

[0036] Advantageously, the full digital beam-forming processing module 30 has an output operatively connected to the transmission interface 23 to transmit to the external control unit 40 the data received from the receiving and processing array 1 subjected to beam- forming processing performed directly on-board the receiving and processing array 1.

[0037] With reference to Figure 3, according to a possible embodiment, it is also possible to provide that the support body 2,12 comprises a first 2 and at least a second 12 body coupled together. The first body 2 comprises for each antenna element 10 a recess in the shape of a cut that passes completely through the first body 2 extending between two opposite faces 10 of the first body 2 so that the aforesaid recess is open on two opposite sides of the first body 2 along a direction perpendicular to a direction of extension of the array. In this embodiment, the second body 12 is coupled to the first body 2 to close said opposite sides for a plurality of first recesses of respective antenna elements 10, for example for all the radiating elements 10 of the linear array 1. The aforesaid cut is made for example by milling or directly in the casting of the first body 2. For example the first body 2 has the general shape of a plate with parallel faces and the second body comprises two strips 12 (or generally two closing walls) fixed to two opposite faces of the support body 2 to laterally close the recesses. The two strips 12 may be two separate pieces, or the second body is a frame and the strips 12 represent two opposite sides of the frame and a portion of the first body 2 in which are defined the recesses is engaged within the aforesaid frame between the strips 12.

[0038] Note that, starting from a receiving and processing array 1 of the type described above, which is preferably of linear type, it is also possible to make two or three-dimensional arrays comprising a plurality of receiving and processing arrays 1.

[0039] For example, Figure 4 shows a three-dimensional array 100, having the shape of a portion of surface of a truncated cone. With reference to Figure 4, the aforesaid three-dimensional array 100 can be obtained by placing alongside each other several receiving and processing arrays 1 of the type shown in Figures 1 and 3, providing in each of said arrays strips 12, or in general side closing walls, that have the two main faces not parallel to each other. With reference to Figure 5, if instead the strips 12 have their main faces parallel with each other, it is possible to make a two- dimensional planar array 200 for receiving and processing electromagnetic radio-frequency signals.

[0040] With the aforesaid planar 100 or three-dimensional 200 arrays, one can make receiving and processing systems, for example, radar receiving and processing systems. According to an embodiment, a planar array 100 or a three-dimensional array 200 of the type described above is part of a processing and receiving system of a bistatic radar wherein the beam pointing in reception takes place by processing, with full digital beam- forming techniques, radar radio-frequency echo signals picked up by the antenna elements 10. For example, in the above receiving and processing systems, the external control unit 40 is a scheduling block of radar activities. A bistatic radar of the type described above is for example shown in Figure 6 and indicated with 300 and includes, for example, a transmitting antenna 301, for example, an active phased array antenna 300, and a receiving system comprising a plurality 301 of receiving and processing arrays 1 of the type described above arranged so as to form an assembly having an outer truncated-conical surface.

According to an alternative embodiment, it is possible to make a receiving and processing system of a bistatic radar comprising a plurality of receiving and processing arrays 1 of the type described above wherein the receiving and processing arrays 1 are fixed to a surface of a building or of a means of transport, such as for example a ship, to form a conformal receiving and processing system. According to an embodiment, in this case it is possible to provide that the arrays form groups of arrays spaced apart from each other. In this way, it is for example possible to provide a military vessel comprising a bistatic radar comprising a conformal receiving and processing system of radar echo signals, wherein the receiving arrays 1 are fixed to an outer surface of the vessel, for example to a mast, to a portion of the hull, etc., to form a receiving antenna that follows the shape of a portion of said outer surface. Also in this case, it is possible to provide that the receiving and processing arrays form groups of arrays of groups spaced apart from each other.

[0041] From the above description it is clear that the array for receiving and processing electromagnetic radio-frequency signals described above allows fully achieving the intended purposes in terms of overcoming the drawbacks of the known art.

[0042] Without prejudice to the principle of the invention, the forms of implementation and construction details may be varied widely with respect to what has been described and illustrated purely by way of non- limiting example, without thereby departing from the invention as defined in the appended claims.