Improved array antenna for transmit and / or receive calibration; Transmit and / or receive calibration sets.

Abstract

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

Description

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

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

[0002] An array antenna comprises a plurality of channels, each channel associating a radiating element and a transmission / reception module, or TR module (“Transmit-Receive module”) in the following.

[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 making it possible to modify the amplitude and / or the phase of the signal (either of the transmission signal for the transmission chain, or of the reception signal for the reception chain), so as to form a particular antenna pattern and / or modify the pointing direction of the beam of the network antenna.

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

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

[0007] Until now, in transmission, the calibration method generally implemented consists of placing a sensor in front of the network antenna, at a certain distance from the radiating elements. Then, for a complete calibration of the network antenna, the channels of the network antenna are successively activated in transmission. For the active channel at the current time, the phase and the 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 method generally implemented consists of transmitting a signal using a transmitter placed in front of the radiating elements of the network antenna. Then, for a complete calibration of the network antenna, the channels of the network antenna are successively activated in reception. For the active channel at the current time, the amplitude and phase of the reception signal at the output of the reception chain of the active channel are measured using an analyzer.

[0009] For example, an analyzer is a vector type analyzer - VNA ("Vector Network Analyzer") which performs a frequency sweep and makes measurements at a certain number of points in the frequency interval of interest, i.e. the operating frequency interval of the network 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 interval and the group time is deduced therefrom, the propagation time being defined by: Aq> / 2irAF, i.e. the phase difference Aq> between two consecutive points in the frequency interval divided by the frequency difference AF between these two points.

[0010] All of the measurements make 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 so as to cancel, or at least reduce, these biases.

[0011] This state-of-the-art calibration method has many disadvantages:

[0012] - it requires positioning a sensor (or transmitter) in front of each element radiating from the antenna to calibrate the corresponding channel: either it is a single mobile sensor (or transmitter) so that it can be placed opposite the radiating element of the channel that is going to be activated, or it is a set of sensors (or transmitters), each sensor (or transmitter) being pre-positioned opposite a particular radiating element to allow the calibration of the corresponding channel when it is activated. The sensor (or transmitter) can be placed close to 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 are therefore expensive calibration methods, the installation of which is complex. They are external to the network antenna to be calibrated;

[0013] - calibration is not implemented under operational conditions. In In particular, the channels of the network antenna are activated independently of each other. However, in normal operation, several channels are activated simultaneously and there may be coupling effects between channels addressing neighboring radiating elements. These couplings introduce amplitude and phase biases that it would be desirable to be able to calibrate;

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

[0015] - since this calibration is carried out over a long period of time, this can lead to a drift in phase or amplitude of the analyzer which degrades the precision on the measurement of the phase or amplitude difference evaluated between two channels.

[0016] It would therefore be desirable to have a calibration method making it possible to carry out 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 then to propose a calibration method making it possible to meet this need.

[0018] For this purpose, 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 for generating a calibration signal; an input component for replicating the calibration signal 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 marking module for marking the calibration signal by means of a marking code in transmission specific to 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 characteristics, taken in isolation or in all technically possible combinations:

[0020] - each channel comprises a reception chain associated with the radiating element, the receiving chain and the transmitting chain being connected to the radiating element via a duplexer, the individual marked transmitting signal 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 for producing a global 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 for processing the global transmitting signal, by replaying, for each channel, the specific transmitting marking code of said channel, so as to isolate the individual marked transmitting signal of said channel, and determine a transmitting calibration bias affecting said channel.

[0021] - the individual emission signal marked with a channel being emitted by the element associated radiating antenna, the antenna further comprises: a sensor for acquiring a global 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 network antenna and reflected by a calibration reflector; and an analysis device for processing the global transmission signal, by replaying, for each channel, the marking code in specific emission of said channel, so as to isolate the individual marked emission signal of said channel, then determine an emission calibration bias affecting said channel.

[0022] - each channel comprises a reception chain associated with the radiating element, the sensor is made up of the reception chains and the radiating elements of a set of active reception channels.

[0023] The invention also relates to a transmission calibration assembly for the first preceding array antenna, characterized in that, the individual marked transmission signal of 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 a global 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 global 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, 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 reception chain associated with a radiating element, characterized in that, for reception calibration, the network antenna comprises: along the reception chain of each channel of the plurality of channels, a reception marking module for marking a reception calibration signal applied at the input of said reception chain, by means of a reception marking code specific to said channel and obtaining a marked individual reception signal; an output component for producing a global reception signal resulting from the combination of the marked individual reception signals at the output of the reception chains of the channels of the plurality of channels;an analysis device for processing the overall reception signal, by replaying, for a particular channel of the plurality of channels, the specific reception marking code of said particular channel, so as to isolate the individual marked reception signal of said particular channel, then determine a reception 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 characteristics, taken in isolation or in all technically possible combinations:

[0026] - each channel comprises a transmission chain associated with the radiating element, the receiving chain and the transmitting chain being connected to the radiating element via a duplexer, the network antenna comprises: a generator to generate a signal calibration; an input component for replicating 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 on reception.

[0027] - the antenna further comprises: 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 on reception applied at the input of the reception chain of a channel being the calibration signal transmitted into the air by the transmitter, reflected by a calibration reflector, and received by the radiating element of said channel.

[0028] - each channel comprising a transmission chain associated with the radiating element, the transmitter is made up of the transmission chains and the radiating elements of a set of active transmission channels.

[0029] The invention also relates to a reception calibration assembly for the second preceding network antenna, characterized in that the reception calibration assembly comprises, in addition to the network antenna, a reception 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 to the input of the reception 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 global signal taking into account the specific marking code of said channel.

[0032] Preferably, the marking code of a channel is a pseudo-random code.

[0033] The invention also relates to a network antenna conforming to the first preceding antenna and to the second preceding antenna.

[0034] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the drawings in which:

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

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

[0037] [Fig.3] [Fig.3] is a representation of an embodiment of a device analysis of the whole [Fig.l]; and,

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

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

[0040] Fig. 1 shows an embodiment of an assembly 17 according to the invention, which associates a network antenna 16 and a calibration system 15 for implementing a transmission calibration process or for implementing a reception calibration process.

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

[0042] The number N of channels can vary from a few tens to a few hundred channels for an array antenna of a radar system or a radiocommunication system. In the following, channel i is described as a generic channel.

[0043] Each channel i associates a radiating element 1 l_i and a transmission / reception 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. In transmission, the TR module excites the radiating element by means of an electrical transmission signal so that it emits an electromagnetic wave in front of the plane of the array antenna. In reception, an incident electromagnetic wave excites the radiating element, which applies an electrical reception 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, through a switching means, such as a circulator 40_i, to the power 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 radiating element 11_1; the TR module 12_2 comprises a second chain resignation 20_2 and a second reception 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 reception chain 30_N connected, via a circulator 40_N, to the radiating element 11_N.

[0048] Furthermore, the network antenna 16 comprises an input component 28 making it possible to receive, from a transmission electronics (not shown in the figures), a transmission signal SE to be transmitted, and to repeat 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 comprises an output component 29 making it possible to combine 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 processing electronics (not shown in the figures).

[0050] Conventionally, 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 comprises a programmable amplifier, such as an attenuation amplifier.

[0053] Conventionally, each reception 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 reception chain comprises 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 a calibration in transmission, the network antenna 16 is adapted so as to comprise 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 makes it possible to apply, to the input of the module 28, either the transmission signal SE to be transmitted during an operational operating phase of the antenna 16, or the carrier signal SP during a transmission calibration phase of the antenna 16. In this way, an identical signal is distributed at the input of each of the channels of the antenna.

[0060] In addition, for a calibration in transmission, each transmission chain 20_i of the antenna 16 integrates a marking module 23_i having the function of marking the signal traveling through the transmission chain 20_i, according to a CE_i marking code specific to said transmission chain 20_i.

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

[0062] In a preferred embodiment, a marking module 23_i is a 0 / ir phase shifter controlled by a microcontroller storing the marking code CE_i, 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 having 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° during a period Te when the corresponding bit of the marking code CE_i is equal to 1 and a phase shift of ir during the period Te when the corresponding bit of the marking code CE_i is equal to 0.

[0070] The period Te is predetermined.

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

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

[0073] For the transmission calibration method, the calibration system 15 comprises a receiver 55. It is adapted to capture the global transmission signal SEcal produced by the active channels of the network antenna 16 to be calibrated in transmission.

[0074] The calibration system 15 comprises, 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 this channel i in the overall emission signal SEcal. 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 to 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 the transmission calibration is different from that used for the reception calibration.

[0077] For the reception calibration method, 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 makes it possible to mark, by means of a marking code CR_i, specific to the channel i, the signal traveling along this channel operating in reception. This signal, or individual reception signal SScal_i, corresponds to the fraction of the carrier signal SP picked up by the corresponding radiating element 1 l_i.

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

[0080] For example, the structure of a reception marking module is similar to that of a transmission marking module. It is adapted to modulate the individual reception signal with a marking code which is specific to the reception chain considered.

[0081] The reception marking code CR_i of channel i is advantageously different from the transmission marking code CE_i of this same channel.

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

[0083] Module 29 aggregates the individual marked reception signals into a global reception signal SSCal.

[0084] Finally, still for reception calibration, the network antenna 16 comprises, at the output of the module 29, a switch 85 allowing, during the reception calibration phase, the transmission of the global reception signal SSCal to an analysis device 80. A possible structure of the analysis device will be presented in reference in [Fig.3]. The analysis device 80 is capable of replaying the marking code CR_i of each channel i to isolate the individual contribution SScal_i of this channel in the overall reception signal SScal. From the individual contributions, SScal_i, the analysis device 80 determines the reception calibration biases affecting each of the channels i activated during the reception calibration.

[0085] As shown schematically in [Fig.3], an analysis device 100, such as the device 50 or the device 80, comprises a processing module 101 making it possible, for example, to extract the I and Q components of the global signal Seal (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. They each take as input the global signal I / Qcal processed by the module 101.

[0087] To simplify the description, the number of correlation modules is chosen equal to the number N of channels of the network 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 C_i marking code specific to 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 that of 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 with which it is associated in the global signal I / Qcal processed by the module 101.

[0091] More precisely, 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 as that generated by module 61 for device 50, or by module 71 for device 80;

[0093] - A modulator 202, like 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 this channel;

[0094] - A module 203 for incremental phase shifting 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 carrying out a correlation between the signal Scal(k) and a replica of the reference signal Sref_i in phase advance with respect to the signal Sref_i 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 delay 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 delayed global signal by the replica of the reference signal.

[0097] When the two signals at the input of a correlator are marked by the same marking code and when they are perfectly synchronized, the correlation is maximum. It should be noted that applying a PRN code twice successively to the same signal makes it possible to find the initial signal.

[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 substantially equal to zero.

[0099] When the two input signals are marked by 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 processed global signal is delayed by the module 203 before being applied to the input of the three correlators. By means of a control loop, this delay is progressively modified by increments equal to the period Te to search for 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 delayed global signal Scal(k) multiplied by the reference signal Sref_i to an analyzer 220.

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

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

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

[0106] It can query the delay module 203 to know 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 signal Scal_i of the 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] The 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 desired calibration biases.

[0110] The 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 well be described in a procedural form, each step corresponding to the implementation of a function, i.e. 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 the position and equivalent radar surface of the reflector are known. Alternatively, a dedicated “box radome” can be used.

[0113] For an implementation of the calibration method in transmission, it is the antenna operating in reception which analyzes the signal SEcal emitted and reflected by the reflector towards 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 an implementation of the calibration method in reception, it is the antenna operating in transmission which emits the SScal signal. The analysis device 80 is then configured with the marking codes CR_i of the different reception chains to extract their respective contributions.

[0115] Alternatively, the network antenna is only capable of operating in transmission, each of its different channels then comprising only one transmission chain. Only the transmission calibration method is then to be implemented. It is implemented by calibration means taking over the functions of blocks 55 and 50 of the embodiment of [Fig.l]. These means can be external to the network antenna, as in the embodiment of [Fig.l], or integrated into the network antenna and using a reflector to reflect the transmission calibration signal towards the network antenna.

[0116] Alternatively, the network antenna is only capable of operating in reception, each of its different channels comprising only one reception chain. Only the reception calibration method is then to be implemented. It is implemented by calibration means taking over the functions of the components 71 and 75 of the embodiment of [Fig.l]. These means can be external to the network antenna, as in the embodiment of [Fig.l], or integrated into the network antenna and using a reflector to reflect the reception calibration signal towards the network antenna.

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

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

[0119] The present invention is compatible with a continuous mode (continuous waves - CW) or a pulsed mode. Indeed, in the latter case, the coding rhythm is adapted to the width of the pulse 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 width of the pulse and concatenated on reception before demodulation.

[0121] The present invention has numerous 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 an array antenna without disturbing the transmission or reception chain. It can be disengaged for normal operational operation of the array antenna. The calibration functionality is then completely transparent.

[0123] It allows a global measurement using a single sensor (or transmitter). The proposed solution does not require complex external test means. No need for a sensor opposite each radiating element. On the contrary, it is reduced to a single antenna in transmission to calibrate an AESA in reception or in reception to calibrate the AESA in transmission. Thus, the calibration can be carried out in the near or far field depending on the need.

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

[0125] With the invention, the calibration is no longer sensitive to couplings between channels, since it is advantageously implemented while the neighboring channels are active so that the electromagnetic couplings between these channels are taken into account. This solution therefore makes it possible to carry out the calibration of an antenna in operational conditions while taking into account the interactions between channels.

[0126] The implementation of the present invention makes it possible to considerably reduce the validation time of an array 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 carry out the calibration of an antenna in operational conditions, i.e. taking into account the thermal heating of all the channels.

[0128] In addition to calibration, the marking of signals, particularly on reception, could allow specific processing to be carried out.

[0129] The calibration method according to the invention results in an increase in precision:

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

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

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

[0133] In addition, the phase drift created by signal compression in the amplifiers of the transmission or reception chain can be measured. This information makes it possible to set the channels to a desired compression level.

[0134] Compared to a VNA measurement, this technique makes it possible to obtain the group time in a single measurement on the spread band of the code used.

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

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

Claims

Claims

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 calibration in transmission, the array antenna further comprises: - a generator (61) for generating a calibration signal (SP); - an input component (28) for replicating the calibration signal 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 marking module (23_i) for marking the calibration signal by means of a transmission marking code (CE_i) specific to said channel to obtain an individual marked transmission signal (SEcal_i).

2. Antenna according to claim 1, in which, each channel (i) comprising a reception chain (30_i) associated with the radiating element (1 l_i), the reception chain (30_i) and the transmission chain (20_i) being connected to the radiating element (1 l_i) via a duplexer (40_i), the individual marked transmission signal (SEcal_i) of a channel is applied, by the duplexer, at the input of the reception chain of said channel, the antenna further comprising: - an output component (29) for producing a global transmission signal resulting from the combination of the individual marked transmission signals at the output of the reception chains of the channels of the plurality of channels;- an analysis device for processing the overall transmission signal, by replaying, for each channel (i), the transmission marking code (CE_i) specific to 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. Antenna according to claim 1, in which the individual marked transmission signal (SEcal_i) of a channel being emitted by the associated radiating element (ll_i), the antenna further comprises: - a sensor for acquiring a global 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 network antenna and reflected by a calibration reflector; and, - An analysis device for processing 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 determining an emission calibration bias affecting said channel.

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

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

6. Array antenna comprising a plurality of channels, each channel (i) comprising a reception chain (30_i) associated with a radiating element (1 l_i), characterized in that, for reception calibration, the array antenna comprises: - along the reception chain (30_i) of each channel (i) of the plurality of channels, a reception marking module (33_i) for marking a reception calibration signal applied at the input of said reception chain, by means of a reception marking code (CR_i) specific to said channel and obtaining a marked individual reception signal (SScal_i); - an output component (29) for producing a global reception signal (SScal) resulting from the combination of the individual signals of reception marked at the output of the reception chains of the channels of the plurality of channels; - an analysis device (80) for processing the overall reception signal, by replaying, for a particular channel (i) of the plurality of channels, the reception marking code (CR_i) specific to said particular channel, so as to isolate the individual marked reception signal (SScal_i) of said particular channel, then determine a reception calibration bias affecting said particular channel.

7. Antenna according to claim 6, wherein, each channel (i) comprising a transmission chain (20_i) associated with the radiating element (1 l_i), the reception chain (30_i) and the transmission chain (20_i) being connected to the radiating element (1 l_i) via a duplexer (40_i), the network antenna comprises: - a generator for generating a calibration signal (SP); - an input component (28) for replicating 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 on 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 on reception applied at the input of the reception chain of a channel (i) being the calibration signal transmitted 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, in which, 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 channels active in transmission.

10. Reception calibration assembly for a network antenna according to claim 6, characterized in that the reception calibration assembly comprises, in addition to the network antenna, a reception 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 reception chain (30_i) of said channel (i) being the calibration signal transmitted by the transmitter.

11. Antenna according to any one of claims 1 to 4 or 6 to 9, in which a calibration bias, in transmission and / or in reception, is a phase, an amplitude and / or a group propagation time.

12. Antenna according to claim 11, in which, 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 global signal taking into account the specific marking code of said channel.

13. An antenna according to any one of claims 11 to 12, wherein the channel marking code is a pseudorandom code.

14. An array antenna according to any one of claims 1 to 4 and, in combination, according to any one of claims 6 to 9.

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