Enhanced network antenna for transmit and / or receive calibration; Transmit and / or receive calibration kits.

Abstract

Improved array antenna for transmit and / or receive calibration; Transmit and / or receive calibration assemblies. The present invention relates to an array antenna comprising a plurality of channels, each channel (i) comprising a transmit chain (20_i) associated with a radiating element (11_i), characterized in that, to enable transmit calibration, the array antenna further comprises: a generator (61) for generating a calibration signal (SP); an input component (28) for simultaneously replicating the calibration signal at the input of the transmit chain of each channel of the plurality of channels; along the transmit chain of each channel of the plurality of channels, a marking module (23_i) for marking the calibration signal by means of a transmit marking code (CE_i) specific to said channel to obtain an individual marked transmit signal (SEcal_i). Figure for the abstract: Figure 1

Description

Title of the invention: Improved network antenna for calibration in transmission and / or reception; Calibration assemblies in transmission and / or reception.

[0001] The present invention relates to the field of methods and means for calibrating network antennas, in particular active network antennas - AESA (“Active Electronically Scanned Array” in English).

[0002] A network antenna comprises a plurality of paths, each path associating a radiating element and a transmit / receive module, or TR module (“Transmit-Receive module”) in what follows.

[0003] A TR module generally comprises a transmission chain and a reception chain, both of which are coupled to the radiating element through a duplexer, such as a circulator.

[0004] Each TR module integrates programmable components allowing the amplitude and / or phase of the signal (either the transmit signal for the transmitting chain, or the receive signal for the receiving chain) to be modified in order to form a particular antenna pattern and / or modify the pointing direction of the network antenna beam.

[0005] However, for proper operation of the network antenna, each TR module must be calibrated in amplitude and / or phase.

[0006] More specifically, the calibration of a network antenna consists of measuring the relative phase, relative amplitude and relative group time of a signal taking two different paths within the network antenna and compensating for the biases thus measured using the programmable components along one and / or the other path.

[0007] To date, the calibration procedure generally used for transmission involves placing a sensor in front of the array antenna, at a certain distance from the radiating elements. Then, for complete calibration of the array antenna, the channels of the array antenna are successively activated in transmission mode. For the channel active at the current time, the phase and amplitude of the signal emitted by the transmission chain of the active channel and received by the sensor are measured using an analyzer.

[0008] In reception, the calibration procedure generally used consists of emitting a signal using a transmitter placed in front of the radiating elements of the array antenna. Then, for complete calibration of the array antenna, the array channels are successively activated in receive mode. For the channel active at the current time, the amplitude and phase of the received signal at the output of the active channel's receiving chain are measured using an analyzer.

[0009] For example, an analyzer is a vector network analyzer (VNA) that performs a frequency sweep and takes measurements at a number of points within the frequency range of interest, i.e., the operating frequency range of the array antenna. Such an analyzer requires a certain integration time to achieve the desired accuracy. The phase and amplitude are measured for each point. The propagation time is calculated for each point in the frequency range, and the group time is deduced from it. The propagation time is defined by: Aq> / 2irAF, that is, the phase difference Aq> between two consecutive points in the frequency range divided by the frequency difference AF between these two points.

[0010] The set of measurements makes it possible to know the phase difference and / or the amplitude difference between two TR modules and to control the programmable components of the network antenna in order to cancel, or at least reduce, these biases.

[0011] This prior art calibration method has many disadvantages:

[0012] - it requires positioning a sensor (or transmitter) in front of each element The calibration of the corresponding channel is performed using a sensor (or transmitter) radiating from the antenna. This can be done either with a single mobile sensor (or transmitter) that can be positioned opposite the radiating element of the channel to be activated, or with a set of sensors (or transmitters), each pre-positioned opposite a specific radiating element to allow calibration of the corresponding channel when it is activated. The sensor (or transmitter) can be placed near the antenna (near-field calibration) or at a distance from the antenna (far-field calibration). This calibration is generally carried out in dedicated anechoic chambers. These calibration methods are therefore expensive and complex to implement. They are external to the network antenna being calibrated.

[0013] - calibration is not implemented under operational conditions. In In particular, the network antenna channels are activated independently of each other. However, in normal operation, several channels are activated simultaneously, and coupling effects can occur between channels addressing neighboring radiating elements. These couplings introduce amplitude and phase biases that should ideally be calibrated;

[0014] - since there is successive activation of the different pathways, this is a process of calibration which requires a significant amount of implementation time, especially when, for each channel, calibration is performed on several points in frequency over a frequency range;

[0015] - since this calibration takes place over a long period of time, this can lead to drift phase or amplitude of the analyzer degrades the accuracy of the measurement of the phase or amplitude difference evaluated between two channels.

[0016] It would therefore be desirable to have a calibration method allowing simultaneous calibration of a set of active channels of the network antenna, without profoundly modifying the architecture of this antenna.

[0017] The aim of the invention is therefore to propose a calibration method to meet this need.

[0018] To this end, the invention relates to a first network antenna comprising a plurality of channels, each channel comprising a transmission chain associated with a radiating element, characterized in that, to allow calibration in transmission, the network antenna further comprises: a generator to generate a calibration signal; an input component to replicate the calibration signal simultaneously into the input of the transmission chain of each channel of the plurality of channels; along the transmission chain of each channel of the plurality of channels, a marking module to mark the calibration signal by means of a specific transmission marking code of said channel to obtain an individual marked transmission signal.

[0019] According to other advantageous aspects of the invention, the first antenna comprises one or more of the following features, taken individually or in all technically possible combinations:

[0020] - each channel comprises a receiving chain associated with the radiating element, the with the receiving chain and the transmitting chain being connected to the radiating element via a duplexer, the individual transmitting signal marked for a channel is applied, by the duplexer, to the input of the receiving chain of said channel, the antenna further comprising: an output component to produce an overall transmitting signal resulting from the combination of the individual transmitting signals marked at the output of the receiving chains of the channels of the plurality of channels; an analysis device to process the overall transmitting signal, by replaying, for each channel, the specific transmitting marking code of said channel, so as to isolate the individual transmitting signal marked for said channel, and to determine a transmitting calibration bias affecting said channel.

[0021] - the individual emission signal marked with a channel being emitted by the element In addition to the radiating antenna, the antenna further comprises: a sensor to acquire an overall transmission signal resulting from the combination in air of the individual marked transmission signals emitted by the channels of the plurality of channels of the array antenna and reflected by a calibration reflector; and an analysis device to process the overall transmission signal, by replaying, for each channel, the marking code. specific emission of said channel, so as to isolate the individual marked emission signal of said channel, and then determine an emission calibration bias affecting said channel.

[0022] - each channel comprises a receiving chain associated with the radiating element, The sensor consists of the receiving chains and the radiating elements of a set of active receiving channels.

[0023] The invention also relates to a transmission calibration assembly for the first preceding array antenna, characterized in that, the individual emission signal marked for a channel being emitted by the associated radiating element, the transmission calibration assembly comprises, in addition to the array antenna itself, a transmission calibration system comprising: a sensor for acquiring an overall transmission signal resulting from the combination in the air of the individual marked transmission signals emitted by the channels of the plurality of channels of the array antenna; and an analysis device for processing the overall transmission signal obtained at the output of the sensor, by replaying, for each channel, the specific transmission marking code of said channel, so as to isolate the individual marked transmission signal of said channel, and then determine a transmission calibration bias affecting said channel.

[0024] The invention also relates to a second network antenna comprising a plurality of channels, each channel comprising a receiving chain associated with a radiating element, characterized in that, for a receiving calibration, the network antenna comprises: along the receiving chain of each channel of the plurality of channels, a receiving marking module to mark a receiving calibration signal applied at the input of said receiving chain, by means of a receiving marking code specific to said channel and to obtain an individual marked receiving signal; an output component to produce an overall receiving signal resulting from the combination of the individual marked receiving signals at the output of the receiving chains of the channels of the plurality of channels;an analysis device for processing the overall received signal, by replaying, for a particular channel out of the plurality of channels, the specific received marking code of said particular channel, so as to isolate the individual received marked signal of said particular channel, and then determine a received calibration bias affecting said particular channel.

[0025] According to other advantageous aspects of the invention, the second antenna comprises one or more of the following features, taken individually or in all technically possible combinations:

[0026] - each channel comprises an emission chain associated with the radiating element, the With the receiving and transmitting chains connected to the radiating element via a duplexer, the network antenna includes: a generator to generate a signal calibration; an input component to replicate the calibration signal simultaneously at the input of each transmitting channel of the plurality of channels, for each channel of the plurality of channels, the duplexer of said channel applying the signal at the output of the transmitting channel of said channel, at the input of the receiving channel of said channel as a calibration signal in reception.

[0027] - the antenna further comprises: a generator for generating a calibration signal; an emitter to emit the calibration signal, for each channel of the plurality of channels, the calibration signal in reception applied at the input of the receiving chain of a channel being the calibration signal emitted into the air by the emitter, reflected by a calibration reflector, and received by the radiating element of said channel.

[0028] - each channel comprising an emission chain associated with the radiating element, The transmitter consists of the transmission chains and radiating elements of a set of active transmission channels.

[0029] The invention also relates to a receiving calibration assembly for the second preceding network antenna, characterized in that the receiving calibration assembly comprises, in addition to the network antenna, a receiving calibration system comprising: a generator for generating a calibration signal; a transmitter for transmitting the calibration signal, for each channel of the plurality of channels, the calibration signal applied at the input of the receiving chain of said channel being the calibration signal transmitted by the transmitter.

[0030] Preferably, a calibration bias in transmission and / or reception is a phase, an amplitude and / or a group propagation time.

[0031] Preferably, a calibration signal being a carrier signal, a channel marking module modulates the carrier signal taking into account the specific marking code of said channel, and an analysis device demodulates the overall signal taking into account the specific marking code of said channel.

[0032] Preferably, the marking code for a lane is a pseudo-random code.

[0033] The invention also relates to an array antenna conforming to the first previous antenna and the second previous antenna.

[0034] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0035] [Fig-1] the [Fig.1] representation of an embodiment of an assembly according to the invention combining a network antenna 16 and a calibration system 15 for the implementation of a calibration method in transmission or a calibration method in reception;

[0036] [Fig.2] [Fig.2] is a representation of the marking of a carrier signal;

[0037] [Fig.3] [Fig.3] is a representation of one embodiment of a device analysis of the entire [Fig. 1]; and,

[0038] [Fig.4] [Fig.4] is a representation of one embodiment of a module of correlation of the analysis device of the [Fig.3].

[0039] In general, the present invention is based on marking, by each active channel, the signal it emits (or receives) using a specific code. This then allows the analysis means to separate the contribution of each active channel to the overall signal emitted (or received) during the calibration of the network antenna. It is this ability to distinguish the contribution of each channel that enables the simultaneous calibration of several channels.

[0040] Fig. 1 represents an embodiment of an assembly 17 according to the invention, which combines a network antenna 16 and a calibration system 15 for the implementation of a calibration method in transmission or the implementation of a calibration method in reception.

[0041] In a manner known per se, the network antenna 16 comprises a plurality of N channels. In [Fig.1], each channel is referenced by its rank i, an integer between 1 and N.

[0042] The number N of channels can vary from a few dozen to a few hundred channels for an array antenna of a radar system or a radio communication system. In what follows, channel i is described as a generic channel.

[0043] Each channel i associates a radiating element 1 l_i and a transmit / receive module, or TR module, 12_i. The TR module is electrically connected to the associated radiating element.

[0044] Thus, the first channel 1 comprises a radiating element 11_1 and a TR module 12_1; the second channel 2 comprises a radiating element 11_2 and a TR module 12_2; ... and, the Nth channel N comprises a radiating element 11_N and a TR module 12_N.

[0045] A radiating element 1 l_i is, for example, a patch antenna, electrically connected to the associated TR module 12_i by at least one feed line. During transmission, the TR module excites the radiating element by means of a transmit electrical signal so that it emits an electromagnetic wave in front of the plane of the array antenna. During reception, an incident electromagnetic wave excites the radiating element, which applies a receive electrical signal to the TR module.

[0046] Each TR module 12_i comprises a transmission chain 20_i and a reception chain 30_i in parallel with each other. They are connected, via a switching means, such as a circulator 40_i, to the supply line of the corresponding radiating element 1 l_i.

[0047] Thus, the TR module 12_1 comprises a first transmission chain 20_l and a first reception chain 30_l connected, via a first circulator 40_l, to the first radiant element 11_1; the TR module 12_2 comprises a second chain transmission 20_2 and a second receiving chain 30_2 connected, via a second circulator 40_2, to the second radiating element 11_2; ... and, the TR module 12_N comprises a transmission chain 20_N and a receiving chain 30_N connected, via a circulator 40_N, to the radiating element 11_N.

[0048] In addition, the network antenna 16 includes an input component 28 for receiving, from a transmission electronics (not shown in the figures), a transmission signal SE to be transmitted, and for repeating this transmission signal on the input of each of the transmission chains of the different TR modules of the antenna 16.

[0049] The network antenna 16 includes an output component 29 for combining the individual reception signals delivered at the output of each of the reception chains of the different TR modules of the antenna 16, so as to transmit a reception signal SS to a processing electronic (not shown in the figures).

[0050] In a conventional manner, a transmission chain 20_i comprises, in series, a phase shifter 21_i and one or more amplifier(s) 22_i.

[0051] In the case of a passive antenna, the phase shifter is programmable and the amplifier is a power amplifier.

[0052] In the case of an active antenna, at least one amplifier is programmable. For example, in addition to the power amplifier, the transmission chain includes a programmable amplifier, such as an attenuation amplifier.

[0053] In a conventional manner, each receiving chain 30_i comprises, in series, one or more amplifier(s) 32_i and a phase shifter 3 l_i.

[0054] In the case of a passive antenna, the phase shifter is programmable and the amplifier is a low noise amplifier.

[0055] In the case of an active antenna, at least one amplifier is programmable. For example, in addition to a low-noise amplifier, the receiving chain includes a programmable amplifier, such as an attenuation amplifier.

[0056] A programmable component participates in the formation of the antenna beam.

[0057] According to the invention, for calibration in transmission, the array antenna 16 is adapted to include a carrier generator 61 and a switch 65.

[0058] The carrier signal SP delivered by the generator 61 is preferably a sinusoidal signal of frequency Fo.

[0059] The switch 65 allows the input of module 28 to be applied either the SE transmission signal to be emitted during an operational phase of the antenna 16, or the SP carrier signal during a calibration phase in transmission of the antenna 16. In this way, an identical signal is distributed at the input of each of the antenna channels.

[0060] Furthermore, for calibration during transmission, each transmission channel 20_i of the antenna 16 incorporates a marking module 23_i whose function is to mark the signal traveling through the 20_i transmission chain, according to a specific CE_i marking code of said 20_i transmission chain.

[0061] Thus, the first transmission chain 20_l has a marking module 23_1 using a CE_1 code; the second transmission chain 20_2 has a marking module 23_2 using a CE_2 code; ... and, the Nth transmission chain 20_N has a marking module 23_N using a CE_N code.

[0062] In a preferred embodiment, a marking module 23_i is a 0 / ir phase shifter controlled by a microcontroller storing the CE_i marking code, which is specific to channel i. The 0 / ir phase shifter is, for example, in the case of a transmission chain operating in differential mode, a transistor-based Gilbert mixer.

[0063] The CE_i marking code is a binary code, consisting of a series of L bits. For example, L is equal to 1000 bits.

[0064] Preferably, marking codes with orthogonality properties between them, called pseudo-orthogonal codes, are used.

[0065] Preferably, the marking code is a pseudo-random code - PRN ("Pseudo Random Noise"). This is a binary code obtained by random selection according to a Gaussian distribution so as to correspond to white noise.

[0066] Alternatively, this is a Gold code.

[0067] The marking code is previously generated and associated with a particular 20_i transmission chain of the antenna, for example by storing it in the microcontroller controlling the 0 / ir phase shifter.

[0068] As shown in [Fig.2], the carrier signal SP is a sinusoidal signal with a characteristic frequency Fo.

[0069] The phase shifter 0 / ir introduces into the phase of the carrier signal SP a phase shift of 0° for a period Te when the corresponding bit of the marking code CE_i is 1 and a phase shift of ir for the period Te when the corresponding bit of the marking code CE_i is 0.

[0070] The period Te is predetermined.

[0071] The carrier signal thus marked constitutes the individual SEcal_i emission signal by the channel i considered during the emission calibration.

[0072] When attempting to calibrate the transmission of all N channels of antenna 16, there is therefore simultaneous emission of N individual transmission signals SEcal_i, which combine in such a way as to constitute an overall transmission signal SEcal.

[0073] For the emission calibration process, the calibration system 15 includes a receiver 55. It is adapted to capture the overall SEcal emission signal produced by the active channels of the array antenna 16 to be calibrated in emission.

[0074] The calibration system 15 includes, connected to the output of the receiver 55, an analysis device 50. A possible structure of the analysis device will be presented in relation to [Fig. 3]. The analysis device is capable of replaying the CE_i marking code of each channel i to isolate the individual contribution SEcal_i of that channel i in the overall SEcal emission signal. From the individual contributions, SEcal_i, the analysis device 50 determines the emission calibration biases affecting each of the channels i.

[0075] According to the invention, for a calibration in reception of the antenna 16, the calibration system 15 comprises a carrier generator 71 and a transmitter 75, which is connected at the output of the generator 71 so as to emit an electromagnetic wave corresponding to the carrier signal delivered by the generator 71.

[0076] The carrier signal SP generated by the generator 71 is preferably a sinusoidal signal, for example of frequency Fo. Alternatively, the carrier frequency for transmission calibration is different from that used for reception calibration.

[0077] For the calibration process in reception, the network antenna 16 is adapted so that each of the reception chains 30_i of the different channels i of the antenna 16 is equipped with a marking module 33_i.

[0078] This marking module allows the signal traveling along channel i, operating in receive mode, to be marked using a CR_i marking code specific to channel i. This signal, or individual receive signal SScal_i, corresponds to the fraction of the carrier signal SP captured by the corresponding radiating element l_i.

[0079] Thus, the first receiving chain 30_l has a marking module 33_1 using a first receiving marking code CR_1; the second receiving chain 30_2 has a marking module 33_1 using a second receiving marking code CR_2; ... and, the Nth receiving chain 30_N has a marking module 33_N using an Nth marking code CR_N.

[0080] For example, the structure of a receiving marking module is similar to that of a transmitting marking module. It is adapted to modulate the individual received signal with a marking code that is specific to the receiving chain under consideration.

[0081] The receiving marking code CR_i of channel i is advantageously different from the transmitting marking code CE_i of the same channel.

[0082] Each receiving channel delivers an individual receive signal marked SScal_i.

[0083] Module 29 aggregates the individual marked receive signals into an overall SSCal receive signal.

[0084] Finally, also for receive calibration, the array antenna 16 includes, at the output of module 29, a switch 85 which, during the receive calibration phase, allows the transmission of the overall SSCal receive signal to an analysis device 80. A possible structure of the analysis device will be presented by reference as shown in [Fig. 3]. The analysis device 80 is capable of replaying the CR_i marking code of each channel i to isolate the individual contribution SScal_i of that channel in the overall received signal SScal. From the individual contributions, SScal_i, the analysis device 80 determines the received calibration biases affecting each of the channels i activated during received calibration.

[0085] As schematically represented in [Fig.3], an analysis device 100, such as device 50 or device 80, includes a processing module 101 allowing, for example, the extraction of the I and Q components of the global Seal signal (corresponding to SScal in reception and SEcal in transmission).

[0086] The analysis device 100 comprises, downstream of the processing module 101, a plurality of correlation modules, arranged in parallel with each other. Each of them takes as input the overall signal I / Qcal processed by the module 101.

[0087] To simplify the description, the number of correlation modules is chosen to be equal to the number N of channels of the array antenna 16 to be calibrated.

[0088] Thus, the analysis device 100 comprises a first correlation module 110_l, a second correlation module 110_2, ... an ith correlation module 110_i; ... and an Nth correlation module 110_N.

[0089] Each correlation module 110_i is associated with a single channel i of the antenna 16. It is configured with the specific C_i marking code for this channel (the CE_i marking code of the transmission chain for device 50 and the CR_i marking code of the reception chain for device 80).

[0090] Each correlation device 110_i is then adapted to isolate the individual contribution Scal_i (SEcal-i in transmission and SScal_i in reception) of the channel i to which it is associated in the global signal I / Qcal processed by the module 101.

[0091] More specifically, as shown in [Fig.4], a correlation module 110_i comprises, for example:

[0092] - a carrier generator 201, adapted to generate an identical carrier signal to the carrier signal than that generated by module 61 for device 50, or by module 71 for device 80;

[0093] - A 202 modulator, such as a 0 / ir phase shifter controlled by a microcontroller, configured with the marking code C_i (CE_i in transmission and CR_i in reception) of the associated channel i, in order to modulate the carrier signal SP with the specific marking code of channel i and obtain a reference signal Sref_i for that channel;

[0094] - A 203 incremental phase shift module of the processed global signal I / Qcal for generate a global signal delayed by a number k of periods Te, Scal(k);

[0095] - First, second and third correlators, 211, 212, 213, suitable for performing a correlation between the Scal(k) signal and a replica of the reference signal Sref_i that is phase-advanced relative to the Sref_i signal for the first correlator 211, a replica of the reference signal Sref_i synchronized with the signal Sref_i for the second correlator 212, and a replica of the reference signal Sref_i in phase lag with respect to the signal Sref_i for the third correlator 213. The first and third correlators are offset from the second correlator by a fraction of the period Te.

[0096] A correlator performs the product of the global delayed signal by the replica of the reference signal.

[0097] When the two input signals of a correlator are marked with the same marking code and are perfectly synchronized, the correlation is maximal. It should be noted that applying a PRN code twice successively to the same signal allows the original signal to be recovered.

[0098] On the other hand, as soon as there is a loss of synchronization between the two input signals, even if they are marked by the same marking code, the correlation decreases rapidly and is essentially equal to zero.

[0099] When the two input signals are marked with different marking codes, the correlation is zero, regardless of any synchronization. Because of this property, the marking codes are said to be orthogonal to each other.

[0100] The overall processed signal is delayed by module 203 before being applied to the input of the three correlators. By means of a feedback loop, this delay is progressively modified by increments equal to the period Te to seek a maximum correlation on the second correlator 212.

[0101] Once the maximum correlation was identified, synchronization on the carrier phase was obtained, as well as synchronization on the marking code.

[0102] The second correlator then transmits the signal resulting from the product of the global delayed signal Scal(k) multiplied by the reference signal Sref_i to an analyzer 220.

[0103] This resulting signal is none other than the Scal_i contribution of channel i to the global Seal signal.

[0104] The analyzer 220 is advantageously a vector analyzer conforming to the prior art.

[0105] It evaluates the amplitude A_i of the Scal_i signal of channel i.

[0106] It can query the delay module 203 to find out the number k of periods used to delay the overall signal. This information corresponds to the phase <p_i du signal Scal_i de la voie i.

[0107] The analyzer 220 can perform measurements for different points of a frequency interval around the frequency Fo in order to determine the group propagation time r_i of the Scal_i signal of channel i.

[0108] The outputs of the different analyzers of the correlation modules 110_i are associated by a calculation module 120 ([Fig.3]) of the analysis device 100.

[0109] Module 120 is particularly suitable for calculating phase deviations Aq>, amplitude AA and / or group propagation time Ar between two channels, in transmission or reception, which are the calibration biases sought.

[0110] Calibration operations can then be carried out based on this information, using the programmable elements (phase shifter / attenuator) available on each channel i.

[0111] It should be noted that [Fig. 1], 3 and 4 have been described in a structural form, each component of the system performing a particular function. However, these figures could just as easily be described in a procedural form, each step corresponding to the implementation of a function, that is to say, to the use of the corresponding functional component.

[0112] In a second embodiment, instead of using a calibration system 15, a reflector is placed in front of the antenna 16. The properties, in particular its position and radar cross-section, of the reflector are known. Alternatively, a dedicated "radome box" can be used.

[0113] For an implementation of the calibration process in transmission, the antenna operating in receiving mode analyzes the SEcal signal emitted and reflected by the reflector back to the antenna. The analysis device 80 is then configured with the CE_i marking codes of the different transmission chains to extract their respective contributions.

[0114] For implementation of the calibration process in reception, it is the antenna operating in transmit mode that emits the SScal signal. The analysis device 80 is then configured with the CR_i marking codes of the different reception chains to extract their respective contributions.

[0115] Alternatively, the array antenna is only capable of transmitting, each of its different channels then comprising only one transmit chain. Only the transmit calibration process then needs to be implemented. It is implemented by calibration means incorporating the functions of blocks 55 and 50 of the embodiment of [Fig. 1]. These means can be external to the array antenna, as in the embodiment of [Fig. 1], or integrated into the array antenna and using a reflector to reflect the transmitted calibration signal back to the array antenna.

[0116] Alternatively, the array antenna is only capable of receiving, each of its different channels comprising only one receiving chain. Only the receiving calibration process then needs to be implemented. This is implemented by calibration means incorporating the functions of components 71 and 75 of the embodiment shown in [Fig. 1]. These means can be external to the array antenna, as in the embodiment shown in [Fig. 1], or integrated into the array antenna and using a reflector to reflect the receiving calibration signal back to the array antenna.

[0117] The present invention is not limited to calibration in radiated mode but can also be applied to calibration in ducted mode. That is to say, the signal emitted by the transmission chain of a channel is not applied by the circulator of that channel to the associated radiating element, but reinjected by the circulator directly into the input of the receiving chain of said channel. This makes it possible to calibrate not the entire channel, transmission chain and radiating element in transmission mode and / or radiating element and receiving chain in reception mode, but simply the transmission chain and / or the receiving chain. The calibration methods are simplified insofar as it is no longer necessary, in transmission mode, to capture a signal emitted into the air and / or in reception mode, to emit a signal into the air.

[0118] The calibration according to the invention can be simplified by refraining from servo control on the carrier and by restricting the search domain in phase, knowing the distance between the antenna plane and the calibration system or the reflector.

[0119] The present invention is compatible with either a continuous (continuous wave - CW) or a pulsed mode. Indeed, in the latter case, the coding rate is adapted to the pulse width and its recurrence frequency.

[0120] The marking code is either modified at each recurrence and the processing is carried out in the same way as the continuous mode, or distributed by sample over the pulse width and concatenated at reception before demodulation.

[0121] The present invention has many advantages:

[0122] The proposed solution adds little complexity to the physical architecture of the antennas since it relies on the use of resources already available or easily integrated into the architecture of a network antenna without disrupting the transmission or reception chain. It can be disabled for the normal operational functioning of the network antenna. The calibration functionality is then completely transparent.

[0123] It allows for global measurement using a single sensor (or transmitter). The proposed solution does not require complex external testing equipment. There is no need for a sensor opposite each radiating element. On the contrary, it is reduced to a single transmitting antenna to calibrate an AESA in reception, or a receiving antenna to calibrate the transmitting AESA. Thus, calibration can be performed in the near or far field, as required.

[0124] In the reflector embodiment, the array antenna can even perform self-test or self-calibration operations. The array antenna can be calibrated using only its own resources, i.e., without the need for any external specific devices. This is therefore a particularly simple calibration solution to implement.

[0125] With the invention, calibration is no longer sensitive to coupling between channels, since it is advantageously implemented while neighboring channels are active, thus taking into account the electromagnetic coupling between these channels. This solution therefore makes it possible to calibrate an antenna under operational conditions while considering the interactions between channels.

[0126] The implementation of the present invention makes it possible to considerably reduce the validation time of a network antenna due to the simultaneous calibration of a large number of channels, or even all of the channels.

[0127] This solution makes it possible to perform the calibration of an antenna under operational conditions, i.e. taking into account the thermal heating of all the channels.

[0128] In addition to calibration, signal marking, particularly in reception, could allow for specific processing.

[0129] The calibration process according to the invention results in an increase in accuracy:

[0130] - the group propagation time is measured in a single measurement operation.

[0131] - the simultaneous measurement of the phase and amplitude differences of each TR module for different levels of transmission power of the TR modules.

[0132] - the simultaneous measurement of the phase and amplitude differences of each TR module while all TR modules are in operation.

[0133] Furthermore, the phase drift created by signal compression in the amplifiers of the transmitting or receiving chain can be measured. This information makes it possible to calibrate the channels to a desired compression level.

[0134] Compared to a measurement at VNA, this technique allows obtaining the group time in a single measurement on the spread strip of the code used.

[0135] This solution can be used over the entire operating frequency range of the system.

[0136] This solution can be used over a large signal power dynamic range, the level of accuracy depending on the signal-to-noise ratio related to the length of the code used, the data rate and the number of channels processed simultaneously.

Claims

Demands

1. Array antenna comprising a plurality of channels, each channel (i) comprising a transmission chain (20_i) associated with a radiating element (1 l_i), characterized in that, to allow a calibration in transmission, i.e. a measurement of a calibration bias in transmission, the calibration bias in transmission being a phase, an amplitude and / or a group propagation time, the array antenna further comprises: - a generator (61) for generating a calibration signal in transmission (SP); - an input component (28) for replicating the calibration signal in transmission simultaneously at the input of the transmission chain of each channel of the plurality of channels;- along the transmission chain of each channel of the plurality of channels, a transmission marking module (23_i) to mark the calibration signal in transmission by means of a transmission marking code (CE_i) specific to said channel to obtain an individual marked transmission signal (SEcal_i), the transmission marking code of a channel being a pseudo-random code, the calibration signal in transmission being a carrier signal, the transmission marking module of a channel being adapted to modulate the carrier signal taking into account the specific transmission marking code of said channel, the transmission marking module being a 0 / ;r phase shifter controlled by a microcontroller storing the specific transmission marking code of said channel.;

2. Antenna according to claim 1, wherein, each channel (i) comprising a receiving chain (30_i) associated with the radiating element (1 l_i), the receiving chain (30_i) and the transmitting chain (20_i) being connected to the radiating element (1 l_i) via a duplexer (40_i), the individual marked transmitting signal (SEcal_i) of a channel is applied, by the duplexer, to the input of the receiving chain of said channel, the antenna further comprising: - an output component (29) to produce an overall transmitting signal resulting from the combination of the individual marked transmitting signals at the output of the receiving chains of the channels of the plurality of channels; - an analysis device adapted to demodulate the global transmission signal, by replaying, for each channel (i), the specific transmission marking code (CE_i) of said channel, so as to isolate the individual marked transmission signal (SEcal_i) of said channel, and determine a transmission calibration bias affecting said channel.

3. An antenna according to claim 1, wherein the individual marked emission signal (SEcal_i) of a channel is emitted by the associated radiating element (ll_i), the antenna further comprises: - a sensor for acquiring an overall emission signal (SEcal) resulting from the combination in air of the individual marked emission signals emitted by the channels of the plurality of channels of the array antenna and reflected by a calibration reflector; and, - an analysis device adapted to demodulate the overall emission signal, by replaying, for each channel (i), the specific emission marking code (CE_i) of said channel, so as to isolate the individual marked emission signal (SEcal_i) of said channel, and then determine an emission calibration bias affecting said channel.

4. Antenna according to claim 3, wherein, each channel (i) comprising a receiving chain (30_i) associated with the radiating element (1 l_i), the sensor is constituted by the receiving chains and the radiating elements of a set of channels active in receiving.

5. An antenna transmission calibration assembly according to claim 1, characterized in that, the individual marked transmission signal (SEcal_i) of a channel being emitted by the associated radiating element (l_i), the transmission calibration assembly comprises, in addition to the array antenna itself, a transmission calibration system comprising: - a sensor (55) for acquiring an overall transmission signal (SEcal) resulting from the combination in the air of the individual marked transmission signals emitted by the channels of the plurality of channels of the array antenna; and, - an analysis device (50) adapted to demodulate the overall transmission signal obtained at the output of the sensor, by replaying, for each channel (i), the specific transmission marking code (CE_i) of said channel, so as to isolate the individual marked transmission signal (SEcal_i) of said channel, and then determine a transmission calibration bias affecting said channel.

6. An array antenna comprising a plurality of channels, each channel (i) comprising a receiving chain (30_i) associated with a radiating element (1 l_i), characterized in that, for a receive calibration, i.e. a measurement of a receive calibration bias, the receive calibration bias being a phase, an amplitude and / or a group propagation time, the array antenna comprises: - along the receiving chain (30_i) of each channel (i) of the plurality of channels, a receive marking module (33_i) for marking a receive calibration signal applied to the input of said receiving chain, by means of a receive marking code (CR_i) specific to said channel and obtaining an individual marked receive signal (SScal_i), the receive marking code of a channel being a pseudo-random code, the receive calibration signal being a carrier signal,- a channel receiving marking module adapted to modulate the carrier signal taking into account the specific receiving marking code of said channel, the receiving marking module being a 0 / r phase shifter controlled by a microcontroller storing the specific receiving marking code of said channel; - an output component (29) to produce an overall received signal (SScal) resulting from the combination of the individual marked received signals at the output of the receiving chains of the channels of the plurality of channels; - an analysis device (80) adapted to demodulate the overall received signal, by replaying, for a particular channel (i) of the plurality of channels, the specific receiving marking code (CR_i) of said particular channel, so as to isolate the individual marked received signal (SScal_i) of said particular channel, and then determine a received calibration bias affecting said particular channel.

7. Antenna according to claim 6, wherein, each channel (i) comprising a transmitting chain (20_i) associated with the radiating element (1 l_i), the receiving chain (30_i) and the transmitting chain (20_i) being connected to the radiating element (1 l_i) via a duplexer (40_i), the array antenna comprises: - a generator for generating a calibration signal (SP); - an input component (28) to replicate the calibration signal simultaneously at the input of each transmission chain of the channels of the plurality of channels, for each channel of the plurality of channels, the duplexer of said channel applying the signal at the output of the transmission chain of said channel, at the input of the reception chain of said channel as a calibration signal in reception.

8. Antenna according to claim 6, further comprising: - a generator for generating a calibration signal (SP); - a transmitter for transmitting the calibration signal, for each channel of the plurality of channels, the calibration signal in receive applied at the input of the receiving chain of a channel (i) being the calibration signal emitted into the air by the transmitter, reflected by a calibration reflector, and received by the radiating element (1 l_i) of said channel.

9. Antenna according to claim 8, wherein, each channel (i) comprising a transmission chain (20_i) associated with the radiating element (1 l_i), the transmitter is constituted by the transmission chains and the radiating elements of a set of active transmitting channels.

10. A receiving calibration assembly for a network antenna according to claim 6, characterized in that the receiving calibration assembly comprises, in addition to the network antenna, a receiving calibration system comprising: - a generator (71) for generating a calibration signal (SP); - a transmitter (75) for transmitting the calibration signal, for each channel of the plurality of channels, the calibration signal applied at the input of the receiving chain (30_i) of said channel (i) being the calibration signal emitted by the transmitter.

11. Network antenna according to any one of claims 1 to 4 and, in combination, according to any one of claims 6 to 9.

Images