Photonic device and method for transmitting and / or converting radio frequency signals from a telecommunications satellite

Abstract

A photonic device (10) is proposed for transmitting radio frequency signals (SEn) from at least one RF source. The device comprises: - an optical signal generator (110) for generating N optical signals (S1n), - N optical phase modulators (120-n), each capable of phase-modulating an optical signal (S1n) from an RF signal (SEn), and adapted to deliver a phase-modulated optical signal (S2n), - a demodulator (140) adapted to generate at least one phase-demodulated optical signal (S4, S4n) from at least one optical signal (S2n), and - at least one converter (150) adapted to convert each demodulated optical signal (S4, S4n) into an output signal (S5, S5n) defined in the RF domain, transmitted to at least one receiving unit, and carrying useful information from at least one of the RF signals (SEn). Figure for the abridged version: [Fig.1]

Description

Title of the invention: Photonic device and method for transmitting and / or converting radio frequency signals from a telecommunications satellite technical field

[0001] The present invention relates generally to the space field, and in particular to a photonic device and a method for transmitting and / or converting radio frequency (RF) signals into frequency.

[0002] In telecommunications satellites, the number of receiving elements for the antennas of new payloads and the RF input / output signal frequencies are constantly increasing.

[0003] The receiving elements of such antennas, such as active network antennas, provide radio frequency signals which must be transmitted and converted into frequency.

[0004] However, in embedded applications, frequency conversion and transmission of radio frequency signals from the receiving elements of an active receiving array antenna to a digital processor of the payload can be complex.

[0005] Furthermore, for payload testing operations during procedures called AIT (acronym for the Anglo-Saxon expression Assembly Integration and Testing) carried out on the ground, the transmission and / or conversion of radio frequency signals from the payload in a harsh environment (for example in a thermal vacuum chamber) to measuring equipment placed at ambient temperature may also present implementation difficulties.

[0006] Photonic devices for transmitting and / or converting radio frequency (RF) signals in antenna systems have been proposed, as described, for example, in patent application FR2864385A1. However, such devices have the drawback of using electro-optical amplitude modulators that rely on electronic boards or bias control circuits to function correctly. Consequently, these solutions are incompatible with or very restrictive for embedded or AIT applications. In particular, bias control boards / circuits have thermal vacuum resistance problems, making the implementation of these solutions very expensive relative to the number of electrical connections required. This results in complex implementation, high power consumption and weight, as well as insufficient compactness and reliability.

[0007] There is therefore a need for an improved photonic device enabling transmit and / or convert radio frequency signals efficiently, particularly suited to space-based applications (i.e., applications embedded in the space domain) or to AIT-type applications carried out on the ground. Summary of the invention

[0008] To this end, a photonic device for transmitting radio frequency signals is proposed, comprising a plurality of N inputs and at least one output, each input being capable of receiving one of N input radio frequency signals, the N input radio frequency signals originating from at least one radio frequency signal source. The photonic device comprises: - an optical signal generator configured to generate N optical signals, - a set of N optical phase modulators, each optical modulator being capable of phase-modulating one of the optical signals generated from one of the received input radio frequency signals, each optical phase modulator being adapted to deliver a phase-modulated optical signal at the output, - a demodulator adapted to generate at least one phase-demodulated optical signal from at least one of the modulated optical signals delivered at the output of the N phase-demodulating optical modulators, and - at least one suitable converter to convert at least one phase-demodulated optical signal into at least one output signal defined in the radio frequency domain, the at least one output signal being transmitted to at least one receiving unit, and carrying useful information from at least one of the N input radio frequency signals.

[0009] In embodiments, the demodulator may include one or more optical interleavers with periodic, symmetric or asymmetric responses.

[0010] According to some embodiments, the demodulator may include a wavelength shift switch.

[0011] The demodulator may include at least one sideband rejection filter.

[0012] Advantageously, the photonic device may include a correction loop implemented between the demodulator and the optical signal generator, to adjust the generation of at least one phase-demodulated optical signal.

[0013] The optical signal generator may include at least one laser source, and the laser source may be a continuous wave laser source, a wavelength tunable laser source and / or a laser source pre-modulated by a radio frequency LO signal.

[0014] In some embodiments, the photonic device may further comprise an optical signal processing module adapted to generate an optical signal at starting from the N modulated optical signals delivered at the output of the N phase optical modulators, and the demodulator can be adapted to generate the phase-demodulated optical signal(s) from the optical signal generated by the optical signal processing module.

[0015] The embodiments of the invention further provide a satellite telecommunications system comprising a radio frequency signal source, a receiving unit and a photonic device, the radio frequency signal source being an active array antenna comprising a plurality of receiving elements adapted to generate a plurality N of input radio frequency signals feeding a plurality N of inputs of the photonic device, the receiving unit being a processor capable of being fed by at least one radio frequency signal delivered at output by the photonic device.

[0016] The present invention further proposes a test system for a payload of a telecommunications satellite, the test system comprising a thermal vacuum chamber, a test device comprising a receiving unit, the test system further comprising a photonic device arranged between the thermal vacuum chamber and the test device, the thermal vacuum chamber comprising a radio frequency signal source constituting the payload and being adapted to generate a plurality N of input radio frequency signals feeding N inputs of the photonic device, the optical signal generator being arranged in the test device, or between the thermal vacuum chamber and the test device, the N optical phase modulators being arranged in the thermal vacuum chamber, the demodulator and the converter(s) being arranged in the test device.

[0017] A method for transmitting radio frequency signals is further proposed in response to the reception of a plurality of N input radio frequency signals, the N input radio frequency signals originating from at least one radio frequency signal source. The method comprises at least the following steps: - generate N optical signals; - to phase modulate each optical signal generated from one of the received input radio frequency signals, which provides N modulated optical signals; - demodulate in phase at least one of the modulated optical signals, which provides at least one phase-demodulated optical signal; - convert at least one phase-demodulated optical signal into at least one output signal defined in the radio frequency domain, by applying an optical-electrical / radio frequency conversion, the at least one output signal carrying useful information from at least one of the N input radio frequency signals.

[0018] The device according to the embodiments of the invention allows one or more RF signals to be transmitted and / or converted into frequency simultaneously.

[0019] Such a device is particularly suited to RF bandwidths compatible with telecommunication antenna systems and AIT type applications, but is not limited to them.

[0020] Such a photonic device also makes it possible to obtain a low-power, low-weight solution with improved compactness and reliability, which is particularly advantageous in the space sector. Furthermore, this device benefits from the advantages of optical technologies and links, notably their transparency at RF frequencies, their low distance dependence, their electromagnetic compatibility, and their immunity to electromagnetic interference. (Description of figures)

[0021] Other features, details and advantages of the invention will become apparent from the description made with reference to the accompanying drawings given by way of example.

[0022] [Fig. 1] The [Fig. 1] is a diagram representing a photonic device for transmitting and / or converting radio frequency signals, according to embodiments of the invention.

[0023] [Fig.2] The [Fig.2] is a diagram representing an antenna system in reception, according to embodiments of the invention.

[0024] [Fig.3] The [Fig.3] is a diagram representing a test system, according to embodiments of the invention.

[0025] [Fig.4] Figures 4(a), 4(b) and 4(c) are diagrams representing a module for generating and distributing a plurality of optical signals, according to embodiments of the invention.

[0026] [Fig.5] Figures 5(a) and 5(b) are diagrams representing a phase demodulation module, according to embodiments of the invention.

[0027] [Fig.6] The [Fig.6] is a graphical representation of spectral profiles of different types of phase demodulation module, according to embodiments of the invention.

[0028] [Fig.7] The [Fig.7] is a flowchart representing the method of transmitting and / or converting radio frequency signals, according to embodiments of the invention.

[0029] Identical reference numerals are used in the figures to designate identical or analogous elements. For clarity, the elements shown are not to scale. Detailed description

[0030] Figure 1 schematically represents a photonic device for transmitting and / or converting radio frequency (RF) signals 10 comprising a photonic architecture configured to transmit RF signals, according to embodiments of the invention.

[0031] As used herein, a radio frequency signal transmission via a photonic device refers to a transfer (i.e., a transmission or conversion) of useful information carried by one or more input radio frequency signals from the photonic device 10 to one or more output signals from the photonic device 10, from a plurality of optical, photonic and / or electro-optical elements configured to control, transmit and / or convert radio frequency, photonic and / or electronic signals.

[0032] The photonic device for transmitting and / or converting RF signals 10 (also referred to more simply as 'photonic device' in the rest of the description) can be used in particular in a space domain.

[0033] In particular, the photonic device 10 can be used in a receiving antenna system 2 as shown in [Fig. 2]. For example, and without limitation, in a space-based application of the invention, the antenna system 2 can be implemented as an active antenna integrated into a payload and mounted on board a satellite intended to provide services such as telecommunications services. The satellite can be, for example, a high-throughput or very high-throughput satellite, a so-called flexible satellite equipped with an onboard processor, and / or a satellite equipped with multibeam antennas. The photonic device 10 can then be configured to transmit and / or convert RF signals from a large number of receiving elements of an active array antenna to a processor in the payload. Such a processor can be, for example, a digital processor or an analog processor.

[0034] Furthermore, in an example of an application of the invention to the space domain, the photonic device 10 can be used in a test system 3 as shown in [Fig. 3]. For example, and without limitation, the test system 3 can be used during an AIT procedure performed on the ground. The photonic device 10 can then be configured to transmit and / or convert RF signals from a satellite payload to be tested, placed in a thermal vacuum chamber, to a measurement device located in an EGSE (Electrical Ground Support Equipment) device, placed at ambient temperature and relatively far away.

[0035] Referring again to [Fig. 1], the photonic device 10 comprises a plurality N of inputs (El, ..., EN) and at least one output X. Each input En is capable of receiving an input radio frequency signal, denoted SEn, where 'n' is the index corresponding to the nth input En. The index 'n' is an integer between 1 and N, and the value of N is an integer greater than or equal to 2.

[0036] The N input radio frequency signals SEn can originate from a single source of A radio frequency signal or multiple radio frequency signal sources. A radio frequency signal source can, for example, be configured to emit an RF signal in specific radio frequency bands. A frequency band to be transmitted and / or converted is not limited by the bandwidth of the photonic device 10, so all current "Telecom" RF frequency bands can be covered, i.e., from the "L-band" to the "V-band" (i.e., the current bands from 1 GHz to 50 GHz). A frequency band to be transmitted and / or converted can also correspond to an RF frequency band above 50 GHz, depending on the various electro-optical components of the photonic device 10. For example, the electro-optical components chosen to implement the photonic device 10 may have wider bandwidths, extending, for example, without limitation up to 110 GHz.

[0037] In some embodiments, a radio frequency signal source may comprise one or more receiving elements of an active array antenna 22, as shown in [Fig. 2]. Alternatively, a radio frequency signal source may correspond to one or more access points of a satellite payload 26 placed in a thermal vacuum chamber 32, as shown in [Fig. 3].

[0038] The output X of the photonic device 10 is capable of delivering at least one output signal denoted S5 to at least one receiving unit adapted to process the output signal(s).

[0039] In certain embodiments, the output X of the photonic device 10 may be capable of delivering N output signals S5n to the receiving unit, as shown in [Fig. 2]. The receiving unit may be, for example, a processor 24 (digital or analog) included in the payload of an antenna system 2.

[0040] Alternatively, the output X of the photonic device 10 may be capable of delivering a single output signal S5 to the receiving unit, as shown in [Fig. 3]. The receiving unit may, for example, be a measuring instrument 342 arranged in an EGSE 34 placed at room temperature in a test system 3.

[0041] The photonic device 10 further includes an optical signal generation and distribution module 110, a set of N phase optical modulators 120-n (or 120-1, ..., 120-N), a phase demodulation module 140, and at least one optical-electric / RF conversion module 150.

[0042] Figures 4(a), 4(b) and 4(c) are diagrams representing a module 110 for generating and distributing a plurality of optical signals (also called 'optical signal generator' or more simply 'module 110' in the rest of the description), according to embodiments of the invention.

[0043] Module 110 is configured to generate and distribute a plurality N of optical signals to be distributed, denoted Sin. Each optical signal to be distributed, Sin, is generated from one or more optical electromagnetic wave sources (also called 'optical sources'). An electromagnetic wave of an optical signal can further be characterized by a given wavelength λ, a given phase λ, a given amplitude, and a given polarization. An optical source can, for example, be configured to emit an optical signal in specific optical frequency bands (i.e., specific wavelengths). An optical frequency band can correspond to an ITU (International Telecommunication Union) telecommunication band with a wavelength λ, typically between 1530 nm and 1565 nm.

[0044] In some embodiments, the optical signal generator 110 may comprise a plurality N of laser sources (112-1, ..., 112-N), as illustrated in Figures 4(a) or 4(b). Each laser source 112-n may be configured to generate an initial optical signal SiOn, with initial phase and initial wavelength Xn, the initial wavelengths Xn of the initial optical signals SiOn being distinct from one another. For example, and without limitation, a laser source 112-n may be a continuous-wave laser source.

[0045] In embodiments, the initial optical signals SiOn can correspond directly to the optical signals to be distributed Sin by the module 110, of initial phase On and initial wavelength Xn as illustrated in [Fig.4](a).

[0046] In some embodiments, module 110 may further comprise a unit The module 110 may also include a wavelength division multiplexing (WDM) unit 116 adapted to generate a single intermediate optical signal, denoted SH, from the plurality of initial optical signals SiOn delivered at the output of the plurality N of laser sources 112-n, as illustrated in Figure 4(b). The module 110 may also include a wavelength division multiplexing (WDM) unit 116 adapted to reconstruct the plurality of initial optical signals Sin from the intermediate optical signal SH. In this case, each reconstructed initial optical signal SiOn can correspond to an optical signal Sin to be distributed by the module 110, with initial phase and initial wavelength Xn.

[0047] According to some embodiments, the module 110 may comprise a single optical source, as illustrated in Figure 4(c). Such a single optical source is configured to generate a primary optical signal denoted Sioo having a primary wavelength Åo, a primary phase and a primary power Po.

[0048] In embodiments, the single optical source of the optical signal generator 110 can be a continuous wave laser source 112.

[0049] Alternatively, the single optical source of the module 110 can be a laser source 112' pre-modulated in amplitude and / or phase by a radio frequency signal known as a "local oscillator" and commonly denoted LO. In this case, the pre-modulated optical source The 112' modulated channel of module 110 can be configured to control (i.e. apply and / or modify) an OL modulation of the primary optical signal Sioo in response to a control signal generated by module 110.

[0050] Advantageously, the single optical source 112 or 112' can be a variable wavelength laser source. In this case, the single optical source 112 or 112' can be configured to control (e.g., modify) the primary wavelength Xo of the primary optical signal Sioo in response to a wavelength control signal generated by the module 110.

[0051] In embodiments where the module 110 comprises a single laser source 112 or 112', the module 110 may include a power optical divider 118, as illustrated in Figure 4(c). Such an optical divider 118 can be adapted to generate the plurality of N optical signals Sin, distributed over N distinct optical channels, from the primary optical signal Sioo-. The optical signals Sin to be distributed by the module 110 are then characterized by an output power Pn and a single wavelength X identical for each of the optical signals Sin. In particular, each output power Pn can be defined as a function of the primary power Po of the primary optical signal Sioo-.

[0052] For example, and without limitation, the power delivered Pn for each optical channel can be expressed according to the following equation (01):

[0053] pn = £w(01)

[0054] A delivered power Pn of an optical signal Sin to be distributed can also be equal to the primary power Po, while the other (Nl) optical signals to be distributed have a delivered power equal to zero.

[0055] Advantageously, the optical signals Sin to be distributed by the optical signal generator 110, which includes a single laser source 112 or 112', and a power optical divider 118, can then be characterized by a single identical wavelength X for each of the optical signals Sin.

[0056] In embodiments where the single optical source 112 or 112' is a variable wavelength laser source, the module 110 may include a wavelength demultiplexing unit 116 as illustrated in Figure 4(c). This unit 116 may be adapted to select at least one optical signal, distributed over a separate optical channel, from the primary optical signal Sioo and as a function of the wavelength Xo, to form at least one of the N optical signals to be distributed Sin by the module 110, the wavelengths Xn of the initial optical signals Sin being distinct from each other (the selection may consist, for example, of directing, switching or routing the optical signal).

[0057] Module 110 can be configured to control the demultiplexing unit by wavelength 116 or the optical power divider 118, in response to a first optical channel control signal generated by the photonic device 10 and / or by the optical signal generator 110.

[0058] Advantageously, the module 110 can include one or more transmission means (112-i, 114-i) adapted for transmitting an optical signal. For example, and without limitation, a transmission means (112-i, 114-i) can be a polarization-maintaining fiber (PMF). A PMF fiber can be implemented in the photonic device 10 to: - distribute the initial optical signal SiOn from each continuous wave laser source 112-n to the N optical phase modulators 120-n of the photonic device 10; - transmit the intermediate optical signal Sn from the multiplexing unit 114 to the demultiplexing unit 116; - transmit the primary optical signal Sioo from a single optical source 112 or 112' to the demultiplexing unit 116 or the power optical divider 118.

[0059] The use of PMF optical fibers has the advantage of reducing implementation complexity, increasing mechanical flexibility and minimizing the total mass of the photonic device 10.

[0060] In embodiments where the photonic device 10 is used in a test system 3, the plurality N of continuous wave laser sources 112-n, the wavelength multiplexing unit 114, and / or the single laser source 112 or 112' can be arranged in the EGSE 34 at room temperature. In such embodiments, the wavelength multiplexing unit 116 or the optical power divider 118 can be placed in the thermal vacuum chamber 32, substantially near the output of a payload 26 of a satellite to be tested.

[0061] In embodiments where the photonic device 10 is used in an antenna system 2, the demultiplexing unit 116 or the power optical divider 118 can be arranged substantially close to the output of the receiving elements of the active array antenna 22.

[0062] Furthermore, each phase-modulated optical modulator 120-n of the photonic device 10 is capable of being supplied on the one hand by one of the N input radio frequency signals SEn and on the other hand by one of the N optical signals S[n distributed by the module 110, and of delivering at the output a phase-modulated optical signal S2n.

[0063] In particular, each 120-n phase optical modulator is configured to modulate or convert the phase (initial<I)On ou primaire d> 0, modulated or not) of the optical signal Sin distributed from the applied input radio frequency signal SEn (i.e., the useful information carried by the signal SEn) in such a way as to generate another optical signal having a modulated phase. The phase-modulated optical signal S2n, resulting from the signal The distributed optical signal Sin can thus be characterized by a wavelength (Xo or Xn), a modulated phase 4>2n, and a power Pin. The modulated phase is defined as a function of the phase of the distributed optical signal Sin and the input radio frequency signal SEn.

[0064] Advantageously, in the embodiment where the module 110 comprises one or more continuous wave laser sources (112 or 112-n), the phase optical modulators 120-n can be photonic elements acting as electro-optical converters, and enabling the transfer (i.e., the generation of a transfer function) of RF signals on an optical carrier.

[0065] Alternatively, in the embodiment where the module 110 includes a laser source 112' previously modulated by a radio frequency signal OL, the phase optical modulators 120-n can be photonic elements acting as a photonic mixer and / or RF frequency photonic converter, and enabling the generation of a photonic frequency conversion transfer function of the RF signals.

[0066] In embodiments where the photonic device 10 is used in a test system 3, each optical phase modulator 120-n can be placed in the thermal vacuum chamber 32, substantially close to the output of the payload 26 of a satellite to be tested.

[0067] Furthermore, in the case of a photonic device 10 used in a test system 3 and / or in an antenna system 2, the use of the set of N phase optical modulators 120-na has the advantage of not requiring the use of bias control electronic boards / circuits to ensure the performance of the complete signal link in the system (3 and / or 2).

[0068] In the case where the photonic device 10 is used in an antenna system 2, the use of the set of N optical phase modulators 120-n eliminates the need for bias voltage control electronic boards / circuits required when a solution based on electro-optical amplitude modulators is introduced. Consequently, mechanical integration at the front-ends of an antenna system, for example, is simplified, resulting in a reduced footprint and mass reduction.

[0069] As shown in Figures 1, 2 and 3, the photonic device 10 may also include an optical signal processing module 130, according to embodiments of the invention.

[0070] The optical signal processing module 130 of the photonic device 10 can be adapted to generate a defined optical signal S3 from the N phase-modulated optical signals S2n delivered at the output of the N phase-modulated optical modulators 120-n. The optical signal processing module 130 (i.e., the signal multiplexing or selection module, corresponding to a signal combination module, The signal arrangement, or signal concentration, and also referred to as the 'module 130' hereafter, can comprise a plurality N of inputs and one output. Each output of a 120-n phase optical modulator can be connected to one of the N inputs of the module 130.

[0071] According to some embodiments, a module 130 can be a wavelength multiplexing unit capable of generating an optical signal S3 from the plurality of phase-modulated optical signals S2n at the output of the plurality of N phase-modulated optical modulators 120-n.

[0072] According to other embodiments, a module 130 can be a photonic unit capable of selecting at least one optical signal from among the plurality of phase-modulated optical signals S 2n (the selection can be carried out for example by directing, switching or switching the optical signal).

[0073] Thus, the module 130 can be configured to control the wavelength multiplexing unit or the photonic selection unit, in response to a second optical channel control signal generated by the photonic device 10 and / or by the optical signal processing module 130. In such embodiments, the second optical channel control signal can be defined as a function of the first optical channel control signal generated by the photonic device 10 and / or the optical signal generator 110.

[0074] Thus, depending on the embodiment of the optical signal processing module 130, the optical signal S3 output from module 130 may include: - a single phase-modulated optical signal S2n, or - a plurality of phase-modulated optical signals S2n, of distinct wavelengths An.

[0075] In embodiments where the photonic device 10 is used in a test system 3, the optical signal processing module 130 can be placed in the thermal vacuum chamber 32, substantially close to the output of the payload 26 of a satellite to be tested.

[0076] Advantageously, the photonic device 10 may include a transmission means 130-i adapted for transmitting an optical signal S3 from the output of the optical signal processing module 130 to the demodulator 140. For example, and without limitation, this transmission means 130-i may be a single-mode optical fiber or SMF (acronym for Single Mode Optical Fiber). The use of an SMF fiber has the advantage of reducing the implementation complexity and minimizing the total mass of the photonic device 10.

[0077] In some embodiments, the 130-i transmission means may be a ribbon comprising a plurality of SMF optical fibers (or SMF ribbon) configured to independently carry the plurality of S2n optical signals by means of a unique optical equipment. In this case, the optical signal processing module 130 can be a photonic unit capable of grouping one or more signals from the plurality of optical signals S2n modulated on the transmission means 130-i (i.e. corresponding to an equivalent optical signal S3).

[0078] Figures 5(a) and 5(b) are diagrams representing a phase demodulation module 140 (also called 'phase / amplitude demodulation module', 'phase / amplitude demodulation filter', or more simply 'demodulator1' or 'module 140' hereafter), according to embodiments of the invention.

[0079] The demodulator 140 is adapted to generate at least one phase-demodulated optical signal (denoted S4 or S4n) from the plurality of phase-modulated optical signals S2n originating from the N phase-modulated optical modulators 120-n. The demodulator 140 can therefore comprise a plurality N of inputs, each input being connected to the output of one of the N phase-modulated optical modulators 120-n.

[0080] Thus, in embodiments where the photonic device 10 includes an optical signal processing module 130, the demodulator 140 can be adapted to generate at least one optical signal (denoted S4 or S4n) demodulated in phase from the optical signal S3 from the optical signal processing module 130. The demodulator 140 can in this case include a single input connected to the output of the optical signal processing module 130.

[0081] The demodulator 140 further comprises at least one output. The output(s) of the demodulator 140 are connected to the optical-electrical / RF conversion module(s) 150 or 150-n.

[0082] It should be noted that an optical spectrum of the optical signal S2n at the output of a 120-n phase optical modulator comprises an optical carrier S20n, surrounded by a first modulation sideband S2[n (also called the 'lower modulation sideband') and a second modulation sideband S22n (also called the 'upper modulation sideband'). The two sidebands S2[n and S22n have equal amplitudes and are in opposite phase.

[0083] In particular, the demodulator 140 can be adapted to significantly attenuate the amplitude of one of the two sidebands S2n or S22n of an optical signal S2n to be processed.

[0084] As used here, the expression "significantly attenuate" refers to a notable decrease in the amplitude of one of the two modulation sidebands S2n (or S22n) relative to the other modulation sideband S22n (or S2in) so as to avoid, at the output of the 120-n phase optical modulator, the cancellation of heterodyne beats when the phase-modulated optical signal S2n, which has two amplitude modulation sidebands S2in and S22n, is detected by an optical receiver.

[0085] In the absence of such a demodulator 140, the phase opposition induced, in effect, on a optical detector (or optical receiver, for example a photodiode) of heterodyne beats, due to the quadratic nature of the detector, on the one hand between the optical carrier S2on and the lower modulation sideband S2in, and on the other hand between the optical carrier S2on and the upper modulation sideband S22n which cancel each other out, so that no RF signal can be observed (or determined or evaluated).

[0086] In certain embodiments, the photonic device 10 may further include an optical amplifier (not shown in the figures). For example, and without limitation, the optical amplifier may be implemented between the optical signal processing module 130 and the phase / amplitude demodulator 140 so as to compensate for any optical losses that may be generated in the transmission means 130-i. The optical amplifier may also be implemented so as to compensate for any optical losses generated by connection and disconnection operations at the output of the thermal vacuum chamber 32 in the test system 3. Such an optical amplifier makes it possible, in particular, to maintain a constant received optical power on the optical-to-electrical / RF conversion module(s) 150 or 150-n.

[0087] In embodiments where the photonic device 10 is used in a test system 3, the optical amplifier can for example be located at the input of the EGSE 34, placed at room temperature.

[0088] In certain embodiments where the module 110 is configured to generate optical signals to be distributed S[n] of distinct wavelengths Xn, the demodulator 140 may comprise, or be implemented by, one or more (for example, N) optical interleavers (also called 'optical interleaving elements' or 'in-interleavers'). An interleaver (also called a bandpass filter, and specifically denoted 140b in Figure 5(a)) may be defined according to periodic, symmetrical, or asymmetrical responses. Furthermore, a periodic bandpass filter may be characterized by a center frequency fn or f, used to filter a phase-modulated optical signal S2n from one of the N phase-modulated optical modulators 120-n or the optical signal S3 from the module 130.

[0089] For example, in embodiments where the photonic device 10 includes an optical signal processing module 130, the demodulator 140 may include a single optical interleaver. Alternatively, the demodulator 140 may include a plurality N of optical interleavers, each arranged on a defined optical path for one of the N phase-modulated optical signals S2n delivered by a phase-modulated optical modulator 120-n.

[0090] Advantageously, in certain embodiments where the photonic device 10 includes an optical signal processing module 130, the phase / amplitude demodulator 140 may further include a length-division multiplexing unit wave (noted 142 in figure 5(a)) configured to generate an optical signal S4 or S4n from an optical signal S3 filtered by an optical interleaver. Such a wavelength demultiplexing unit 142 can thus be arranged, for example, at the output of a periodic bandpass filter 140b and be adapted to select (e.g. direct, switch or route) at least one optical signal and distribute it onto a separate optical channel, depending on the wavelength Xn, to form at least one of the N phase-demodulated optical signals S4n, as illustrated in [Fig.5](a).

[0091] In other embodiments where the module 110 is also configured to generate optical signals to be distributed Sin of distinct wavelengths Xn, the phase / amplitude demodulator 140 can be implemented by a WDM switch having a wavelength shift adapted to generate a phase-demodulated optical signal S4 or S4n after optical detection. A WDM switch may, in particular, include a wavelength-shifted demultiplexing unit that is adapted to significantly attenuate the amplitude of one of the two sidebands S2in or S22n of the optical signals S2n to be processed (this unit is designated by reference numeral 142b in Figure 5(b)). Advantageously, such an optical switch may further include a wavelength-selective unit 144, as shown in Figure 5(b).The wavelength selection unit 144 can be arranged at the output of the wavelength shift demultiplexing unit 142b and adapted to select (e.g. direct, switch or route) at least one optical signal, from a separate optical channel, as a function of the wavelength Xn, to form a phase-demodulated optical signal S4, as illustrated in [Fig.5](b).

[0092] In embodiments where the module 110 is configured to generate distributable optical signals Sin characterized by a single identical wavelength X, the demodulator 140 may include one or more sideband rejection filters 148 or 148-n, each processing one optical signal from among the N phase-modulated optical signals S2n originating from one of the N phase-modulated optical modulators 120-n. For example, and without limitation, such a rejection filter may be an FBG (Fiber Bragg Grating) filter or a filter called "Add / Drop WDM". A sideband rejection filter 148 or 148-n may be characterized by a center frequency fn used to filter the phase-modulated optical signal S2n.

[0093] Advantageously, in embodiments where the photonic device 10 includes an optical signal processing module 130, the demodulator 140 may also include an optical signal selection unit 146 configured to switch the optical signal S3 (comprising one or more signals from among the N phase-modulated optical signals S2n) from the optical signal processing module 130 to a separate optical channel on which an optical signal propagates intermediate Si4 n (the switching of the S3 signal can be carried out for example by directing, selecting or piping it). The sideband rejection filter(s) 148 or 148-n can then be located on a separate optical channel at the output of the selection unit 146, for example, as shown in [Fig.5](c).

[0094] In embodiments, the module 140 can be configured to control the optical interlacer(s) 140b, the wavelength demultiplexing unit 142, the wavelength demultiplexing unit 142b with wavelength shift, and / or the wavelength selection unit 144 of optical signals as a function of the wavelength Xn of the phase-modulated optical signals S2n. The module 140 can also be configured to control these optical elements in response to a third optical channel control signal generated by the photonic device 10 and / or by the module 140. Alternatively, the module 140 can be configured to control the optical signal selection unit 146, and / or the sideband rejection filter(s) 148 or 148-n in response to a third optical channel control signal generated by the photonic device 10 and / or by the module 140.

[0095] Advantageously, the third optical channel control signal used in the demodulator 140 can be defined according to the first and / or second optical channel control signal generated by the photonic device 10 and / or by the module 140 and / by the module 110.

[0096] Advantageously, the photonic device 10 may include a correction (or feedback) loop implemented between the demodulator 140 and the optical signal generator 110, as shown in Figures 2 and 3. The correction loop may be implemented so as to adjust the generation of the demodulated optical signal(s) (S4, S4n) in phase. In particular, such a correction loop may be implemented so as to maintain (i.e., adjust) a good match between the wavelengths Δn of the optical signals S[n] distributed by the module 110 and the center frequency fn of the filter (i.e., bandpass filter or sideband rejection filter as defined in the various embodiments).For example and without limitation, the center frequency fn of a filter of the demodulator 140 can be defined as a function of the wavelength control signal e4 generated by the module 110 to control the wavelength of the primary optical signal Sioo- This correction loop makes it possible in particular to compensate for temperature variations or to avoid aging of the optical elements of the photonic device 10. .

[0097] Advantageously, in embodiments where the photonic device 10 is used in a test system 3, the demodulator 140 can be arranged in the EGSE 34 at room temperature.

[0098] In some embodiments, the optical-electrical / RF conversion module(s) 150 or 150-n (also referred to for simplicity as 'converter' or The 'module 150' (hereafter) of the photonic device 10 are adapted to generate at least one output signal (denoted S5 or S5n) from the phase-demodulated optical signal(s) S4 or S4n. A module 150 comprises an input connected to the output of a demodulator 140 and an output. The output of a converter 150 is connected to the receiving unit (24 or 342).

[0099] Advantageously, a converter 150 can be a suitable optical receiver configured to apply a translation function from a phase-demodulated optical signal S4 or S4n to the RF domain. The output signal (denoted S5 or S5n) can be, for example, an electrical signal carrying the useful information, such as the information carried by one or more input radio frequency signals.

[0100] Fig. 6 illustrates examples of graphical representations of spectral profiles of different types of demodulator 140 considered for a photonic device 10 used in an antenna system 2 or in a test system 3.

[0101] Graph (a) in [Fig. 6] shows a spectral profile of a 140 demodulator comprising a symmetric optical interleaver phase / amplitude demodulator operating at 37.5 / 75 GHz. Graph (b) in [Fig. 6] shows a spectral profile of a 140 demodulator comprising a symmetric optical interleaver phase / amplitude demodulator operating at 50 / 100 GHz. Graph (c) in [Fig. 6] shows a spectral profile of a 140 demodulator comprising an asymmetric optical interleaver phase / amplitude demodulator. Graph (d) in [Fig. 6] shows a spectral profile of a 140 demodulator comprising a switching and wavelength-shifting phase / amplitude demodulator.

[0102] It should be noted that a symmetrical optical interleaver phase / amplitude demodulator at 37.5 / 75 GHz can be compatible with optical RF signal processing in the Ka-band at 20 GHz, for example, with a tolerance of 8 GHz. In this case, the optical amplitude of the first sideband is rejected by 15 dB relative to the second sideband (graph (a) of [Fig. 6]), which leads to a minimum rejection of 30 dB in the RF domain. A symmetrical optical interleaver phase / amplitude demodulator at 50 / 100 GHz can be compatible with optical RF signal processing for frequency conversion of V-band radio frequency signals to the C-band and for the transmission of radio frequency signals in the Ka-band, for example (Ka-band Rx at 30 GHz, with a tolerance of 10 GHz).

[0103] Embodiments of the invention thus make it possible to adjust the optical spectrum so that the spectral lines, which participate in the heterodyne beat enabling the generation of the output radio frequency signal of interest, are selected within the bandwidth of the filter (i.e., bandpass filter or sideband rejection filter as defined previously in the various embodiments of module 140), and that the other spectral components should be rejected as far away as possible.

[0104] A phase / amplitude demodulator by switching and wavelength shifting can be compatible with frequency conversions of RF signals from the V band to the C band and from the Ka band to the C band.

[0105] The [Fig.7] is a flowchart representing the method of transmission and / or conversion of N input radio frequency signals SEn implemented by the photonic device 10, according to embodiments of the invention.

[0106] At step 700, a plurality of N optical signals to be distributed Sin is generated by module 110.

[0107] At step 720, each optical signal to be distributed Sin is phase-modulated from an input radio frequency signal SEn so as to generate N modulated optical signals S2n by each of the N modules 120-n.

[0108] At step 760, at least one phase-demodulated optical signal S4 (or S4n) is generated by module 140 from the N modulated optical signals S2n.

[0109] At step 780, at least one output signal S5 (or S5n) defined in the RF domain is generated by optical-electrical / RF conversion via the converter(s) 150 or 150-n from each demodulated optical signal S4 (or S4n).

[0110] The transmission method may also include a step 740 consisting of generating (or selecting) an optical signal S3 by the module 130 from the N modulated optical signals S2n. In this case, in step 760, at least one phase-demodulated optical signal S4 (or S4n) is generated by the module 140 from the optical signal S3.

[0111] Those skilled in the art will understand that the photonic device 10, according to embodiments of the invention, can be implemented in various ways by hardware, or a combination of hardware and software, in particular in the form of program code that can be distributed as a program product in various forms. The program code can be distributed using computer-readable media, which may include computer-readable storage media and communication media. The methods described herein can, in particular, be implemented in the form of computer program instructions executable by one or more processors in a computer system. These computer program instructions can also be stored in computer-readable media.

[0112] The invention is not limited to the embodiments described above by way of non-limiting example. It encompasses all embodiment variations that can be envisaged by a person skilled in the art. In particular, a person skilled in the art will understand that the invention is not limited to the various modules and units of the photonic device described by way of non-limiting example.

Claims

Claims

1. Photonic device (10) for transmitting radiofrequency signals comprising a plurality of N inputs (En) and at least one output (X), each input (En) being capable of receiving an input radiofrequency signal (SEn) from among N input radiofrequency signals (SEn), the N input radiofrequency signals coming from at least one radiofrequency signal source, characterized in that said photonic device (10) comprises: - an optical signal generator (110) configured to generate N optical signals (Sin), - a set of N optical phase modulators (120-n), each optical modulator (120-n) being capable of phase modulating (720) one of said generated optical signals (Sin) from one of said received input radiofrequency signals (SEn), each optical phase modulator (120-n) being adapted to output an optical signal (S2n) phase modulated, - a demodulator (140) adapted to generate at least one optical signal (S4,S4n) phase-demodulated from at least one of said modulated optical signals (S2n) delivered at the output of the N optical phase modulators (120-n), and - at least one converter (150) adapted to convert said at least one phase-demodulated optical signal (S4, S4n) into at least one output signal (S5, S5n) defined in the radiofrequency domain, said at least one output signal (S5, S5n) being transmitted to at least one reception unit, and carrying useful information from at least one of said N input radiofrequency signals (SEn).,

2. A photonic device (10) according to claim 1, wherein said demodulator (140) comprises one or more optical interleavers with periodic, symmetrical or asymmetrical responses.

3. A photonic device (10) according to any preceding claim, wherein said demodulator (140) comprises a wavelength shift switch.

4. A photonic device, according to claim 1, wherein said demodulator (140) comprises at least one sideband rejection filter (148 or 148-n).

5. Photonic device, according to one of the preceding claims, in which the photonic device (10) comprises a correction loop implemented between said demodulator (140) and said optical signal generator (110), to adjust the generation of said at least one phase-demodulated optical signal (S4, S4n).

6. Photonic device, according to one of the preceding claims, wherein said optical signal generator (110) comprises at least one laser source (112, 112' or 112-n), and wherein said at least one laser source (112, 112' or 112-n) is a continuous wave laser source, a wavelength tunable laser source and / or a laser source previously modulated by a radiofrequency signal OL.

7. Photonic device, according to one of the preceding claims, wherein said photonic device (10) further comprises an optical signal processing module (130) adapted to generate an optical signal (S3) from the N modulated optical signals (S2n) delivered at the output of the N optical phase modulators (120-n), and wherein said demodulator (140) is adapted to generate said at least one phase-demodulated optical signal (S4, S4n) from said optical signal (S3) generated by the optical signal processing module (130).

8. Satellite telecommunications system (2) comprising a radiofrequency signal source, a reception unit and a photonic device (10) according to one of claims 1 to 7, said radiofrequency signal source being an active array antenna (22) comprising a plurality of receiving elements adapted to generate a plurality N of input radiofrequency signals feeding a plurality N of inputs (En) of said photonic device (10), said reception unit being a processor (24) capable of being fed by at least one radiofrequency signal (S5, S5n) output by said photonic device (10).

9. Test system (3) of a payload (26) of a telecommunications satellite, said test system (3) comprising a thermal vacuum chamber (32), a test device (34) comprising a receiving unit (342), said test system (3) further comprising a photonic device (10) according to one of claims 1 to 7, arranged between the thermal vacuum chamber (32) and the test device (34), said thermal vacuum chamber (32) comprising a radiofrequency signal source constituting said payload (26) and being adapted to generate a plurality N of input radiofrequency signals feeding N inputs (En) of said photonic device (10), the optical signal generator (110) being arranged in the test device (34), or between the thermal vacuum chamber (32) and the test device (34), the N mo- optical phase dimmers (120-n) being arranged in said thermal vacuum chamber (32), said demodulator (140) and said at least one converter (150) being arranged in said test device (34).

10. A method of transmitting radiofrequency transmission signals in response to receiving a plurality of N input radiofrequency signals (SEn), the N input radiofrequency signals originating from at least one radiofrequency signal source, characterized in that the method comprises at least the following steps: - generating (700) N optical signals (Sin); - phase modulating (720) each generated optical signal (Sin) from one of said received input radiofrequency signals (SEn), which provides N modulated optical signals (S2n); - phase demodulating (760) at least one of said modulated optical signals (S2n), which provides at least one phase demodulated optical signal (S4, S4n); - converting (780) said at least one phase-demodulated optical signal (S4, S4n) into at least one output signal (S5, S5n) defined in the radiofrequency domain, by applying an optical-electrical / radiofrequency conversion (780), said at least one output signal (S5, S5n) carrying useful information from at least one of said N input radiofrequency signals (SEn).