A transmit-receive shared beamforming network based on a wavelength selective switch

Abstract

The present invention discloses a transmit-receive shared beamforming network based on a wavelength selective switch, comprising: a multi-wavelength laser, a plurality of optical switches, a plurality of electro-optic intensity modulators, an erbium-doped fiber amplifier, a 1×n optical splitter, a plurality of optical circulators, a plurality of optical collimating couplers, a diffraction grating, a liquid crystal on silicon device, a plurality of dispersion fibers, a wavelength division multiplexer, and a plurality of photodetectors. The transmit-receive shared beamforming network based on a wavelength selective switch provided by the present invention can achieve multi-channel arbitrary reconfigurable delay and amplitude regulation characteristics for transmit-receive sharing, and realize a microwave photonic beamforming network.

Description

Technical Field

[0001] The present invention belongs to the field of phased array antennas, and particularly relates to a transmit-receive shared beamforming network based on a wavelength selective switch. Background Art

[0002] In traditional analog beam synthesis methods, the electrical phase shifter has frequency-dependent characteristics, resulting in beam squint under broadband; while the broadband true time delay performance of the electrical delay line is limited, and there will be large losses at high frequencies; therefore, the traditional electrical domain analog beam synthesis method cannot meet the beam synthesis requirements of broadband wide-angle scanning. The digital beam synthesis method makes full use of the advantages of digital processing and provides great flexibility for beam synthesis. However, limited by the limited processing bandwidth of the analog-to-digital conversion technology and the limited information processing ability in the digital domain, it still seems inadequate when dealing with the above requirements. Compared with the above two schemes, the optical beamforming network based on microwave photon time delay technology has the characteristics of large instantaneous bandwidth, anti-electromagnetic interference, and compatibility with fiber optic networks, and has great application value in phased array radars and multi-functional integrated electronic countermeasure systems.

[0003] There are mainly three types of schemes for realizing beamforming networks with photon true time delay, including free space optics, integrated optics, and fiber optics, mainly including: using chirped fiber Bragg gratings to form dispersion time delay, cascading multiple optical switches and delay fibers, on-chip integrated optical waveguide schemes, dispersion-enhanced photonic crystal fibers, and high-order mode dispersion multimode fibers, etc. Although the above-mentioned schemes can realize efficient optical beamforming networks, they usually require separate delay devices for each delay channel, and cannot achieve multi-channel parallel optical time delay through a single device, nor can they synchronously and flexibly adjust the amplitude and time delay of a single channel. Summary of the Invention

[0004] To solve the above problems, the present invention proposes a transceiver shared beamforming network based on a wavelength selective switch, which includes a multi-wavelength laser 1. The output end of the multi-wavelength laser 1 is connected to the input end of a first optical switch 2. The output end of the first optical switch 2 is respectively connected to the input end of a first electro-optic intensity modulator 3 and the second input end of a second optical switch 4. The output end of the first electro-optic intensity modulator 3 is connected to the first input end of the second optical switch 4. The output end of the second optical switch 4 is connected to the input end of a 1×n optical splitter 6 through an erbium-doped fiber amplifier 5. The first to the nth output ends of the 1×n optical splitter 6 are respectively connected to the input ends of the 3rd to the (n + 2)th optical switches 7-1 to 7-n. The first output ends of the 3rd to the (n + 2)th optical switches 7-1 to 7-n are respectively connected to the input ends of the 2nd to the (n + 1)th electro-optic intensity modulators 8-1 to 8-n. The output ends of the 2nd to the (n + 1)th electro-optic intensity modulators 8-1 to 8-n are connected to the first input ends of the (n + 3)th to the (2n + 2)th optical switches 9-1 to 9-n; the second output ends of the 3rd to the (n + 2)th optical switches 7-1 to 7-n are respectively connected to the second input ends of the (n + 3)th to the (2n + 2)th optical switches 9-1 to 9-n correspondingly;

[0005] The output ends of the (n + 3)th to the (2n + 2)th optical switches 9-1 to 9-n are connected to the first ports of the first to the nth optical circulators 10-1 to 10-n. The second ports of the first to the nth optical circulators 10-1 to 10-n are respectively connected to the input ends of the (2n + 3)th to the (3n + 2)th optical switches 15-1 to 15-n correspondingly through the first to the nth dispersion fibers 14-1 to 14-n. The first output ends of the (2n + 3)th to the (3n + 2)th optical switches 15-1 to 15-n are respectively connected to the radio frequency input ports of the first to the nth radio frequency circulators 17-1 to 17-n through the first to the nth photodetectors 16-1 to 16-n. The first to the nth dispersion fibers 14-1 to 14-n are connected to a wavelength division multiplexer 19 at the second output ends of the (2n + 3)th to the (3n + 2)th optical switches 15-1 to 15-n. The wavelength division multiplexer 19 is connected to a photodetector 20; the radio frequency output ports of the first to the nth radio frequency circulators 17-1 to 17-n are respectively connected to the radio frequency input ports of the 2nd to the (n + 1)th electro-optic intensity modulators 8-1 to 8-n correspondingly. The fiber ports of the first to the nth radio frequency circulators 17-1 to 17-n are respectively connected to the first to the nth antennas 18-1 to 18-n;

[0006] The third ports of the first to the nth optical circulators 10-1 to 10-n are respectively connected to the input ends of the first to the nth optical collimating couplers 11-1 to 11-n correspondingly. The output ends of the first to the nth optical collimating couplers 11-1 to 11-n are connected to a liquid crystal on silicon device 13 through a diffraction grating 12;

[0007] All the optical switches are 1×2 optical switches, and n is a positive integer greater than or equal to 2.

[0008] Furthermore, the multi-wavelength laser 1 has m output wavelengths, which are λ 1 ~λ m , and adjacent wavelengths maintain the same wavelength interval Δλ.

[0009] Furthermore, the first electro-optic intensity modulator 3 is used to load the radio frequency transmission signal, and the 2nd to the (n + 1)th electro-optic intensity modulators 8-1~8-n are used to load the radio frequency echo signals received from each antenna.

[0010] Furthermore, the diffraction grating 12 has a phase gradient distribution with a fixed period in the long direction, that is where is the phase of the diffraction grating 12, l is the long side of the diffraction grating 12, and Λ is the grating period.

[0011] Furthermore, the liquid crystal on silicon device 13 has a number of liquid crystal pixels in the long and wide directions, and precise phase regulation on each pixel is achieved through pixelated metal electrodes driven and controlled by the underlying silicon-based CMOS; since the light spots of each channel and each wavelength will cover a certain area of the liquid crystal pixel region, if a certain wavelength component λ i returns along the original path, the phase distribution in the area where its light spot is located should satisfy: where is the required phase distribution of the liquid crystal on silicon device in this area, θ i is the incident angle of λ i incident on the liquid crystal on silicon device.

[0012] Furthermore, the liquid crystal on silicon device 13 generates a specific phase gradient distribution in the x direction to cause the returned light to have a spot offset in the x direction relative to the i-th optical collimating coupler 11-i, so that part of it is coupled into the optical fiber to form an optical intensity modulation effect; the optical intensity modulation in the optical link will affect the intensity of the output radio frequency signal, and the relationship is: for every 1 dB increase in the optical loss, the output radio frequency loss increases by 2 dB; where, i = 1, 2,..., n.

[0013] Furthermore, the lengths and dispersion coefficients of the multiple dispersion optical fibers are all kept consistent, and the delay difference generated by the light with wavelengths of λ i and λ j transmitting in the dispersion optical fiber with a length of L is Δτ = DL(λ j -λ i ), where D is the dispersion coefficient, and by changing the maximum wavelength λ m and the minimum wavelength λ 1The wavelength difference and the length of the dispersion fiber change the maximum delay, and the minimum delay accuracy is determined by the wavelength interval Δλ of the multi-wavelength laser 1; if the transmitting / receiving beam direction is ψ, the delay difference between adjacent channels satisfies Δτ = dsinψ / c, where d is the antenna spacing between adjacent channels and c is the speed of light in vacuum.

[0014] Further, when the transmit-receive shared beamforming network operates in the transmit mode, the multi-wavelength laser 1 outputs continuous-wave lasers with wavelengths of λ 1 、λ 2 、…、λ m , with an adjacent wavelength interval of Δλ. The first optical switch 2 and the second optical switch 4 are controlled to select the upper branch. The radio frequency transmit signal is modulated onto the optical carrier by the first electro-optic intensity modulator 3, amplified in gain by the erbium-doped fiber amplifier 5, and equally divided into n paths by the 1×n optical splitter 6. Each path contains equal-power wavelength components of λ 1 ~λ m . The 3rd to the (n + 2)th optical switches 7-1~7-n and the (n + 3)th to the (2n + 2)th optical switches 9-1~9-n are controlled to select the lower branch, and after being collimated by the first to the nth optical circulators 10-1~10-n and the first to the nth optical collimating couplers 11-1~11-n, they are output to free space.

[0015] Further, when the transmit-receive shared beamforming network operates in the receive mode, the multi-wavelength laser 1 outputs continuous-wave lasers with wavelengths of λ 1 、λ 2 、…、λ m , with an adjacent wavelength interval of Δλ. The first optical switch 2 and the second optical switch 4 are controlled to select the lower branch. The optical signal is amplified in gain by the erbium-doped fiber amplifier 5 and equally divided into n paths by the 1×n optical splitter 6. Each path contains equal-power wavelength components of λ 1 ~λ m . The 3rd to the (n + 2)th optical switches 7-1~7-n and the (n + 3)th to the (2n + 2)th optical switches 9-1~9-n are controlled to select the upper branch. The radio frequency echo signals received from the first to the nth antennas 18-1~18-n are modulated onto the optical carrier by the 2nd to the (n + 1)th electro-optic intensity modulators 8-1~8-n after passing through the first to the nth radio frequency circulators 17-1~17-n, and after being collimated by the first to the nth optical circulators 10-1~10-n and the first to the nth optical collimating couplers 11-1~11-n, they are output to free space.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] This beamforming network adopts a transceiver-sharing architecture. Multiple optical switches are used to achieve rapid switching between the receiving branch and the transmitting branch, enabling optical active devices such as multi-wavelength lasers, erbium-doped fiber amplifiers, free-space wavelength selection modules, and photodetectors, as well as optical passive devices such as optical power splitters, optical circulators, optical coupling collimators, and dispersion fibers, to be shared for both transmission and reception. This greatly simplifies the system structure and improves the integration level. The wavelength selection switch composed of a diffraction grating and an LCOS can perform parallel wavelength selection on multiple optical signals, and in combination with dispersion fibers, it can achieve multi-channel optical delay. Compared with the optical delay scheme based on optical switch switching that requires independent delay control devices for each channel, it greatly simplifies the amount of optical delay equipment. Additionally, another significant advantage of this technical solution is its high reconfigurability. Any one or several wavelengths in any transmitting / receiving path can achieve wavelength selection by dynamically loading a specifically designed phase hologram for the LCOS, realizing any set or several sets of different array delays, thereby achieving arbitrary multi-beamforming. At the same time, since the delay and amplitude of the RF signal can be regulated simultaneously, low sidelobe beamforming can also be achieved. Description of the Drawings

[0018] Figure 1 It is a schematic block diagram of a transceiver-sharing beamforming network with n channels according to an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the principle of the free-space optical path module according to an embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram of the two-dimensional planar spot distribution of a liquid crystal on silicon (LCOS) according to an embodiment of the present invention.

[0021] The meanings represented by the reference numerals in the figure are as follows:

[0022] Multi-wavelength laser 1, first optical switch 2, second optical switch 4, 3rd to (n + 2)th optical switches 7 - 1 to 7 - n, (n + 3)th to (2n + 2)th optical switches 9 - 1 to 9 - n, (2n + 3)th to (3n + 2)th optical switches 15 - 1 to 15 - n, first electro-optic intensity modulator 3, 2nd to (n + 1)th electro-optic intensity modulators 8 - 1 to 8 - n, erbium-doped fiber amplifier 5, 1×n optical splitter 6, first to nth optical circulators 10 - 1 to 10 - n, first to nth optical collimating couplers 11 - 1 to 11 - n, diffraction grating 12, liquid crystal on silicon device 13, first to nth dispersion fibers 14 - 1 to 14 - n, first to nth photodetectors 16 - 1 to 16 - n, first to nth RF circulators 17 - 1 to 17 - n, first to nth antennas 18 - 1 to 18 - n, wavelength division multiplexer 19, photodetector 20. Detailed Embodiment

[0023] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant accompanying drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0025] It can be understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. Spatial relationship terms such as "under", "below", "beneath", "underneath", "above", "over", etc. can be used herein to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relationship terms also include different orientations of the device during use and operation. For example, if the device in the drawing is flipped, an element or feature described as "under other elements" or "beneath it" or "under it" will be oriented "above" the other elements or features. Therefore, the exemplary terms "under" and "below" can include both the upper and lower orientations. In addition, the device may also include other orientations (such as rotating 90 degrees or other orientations), and the spatial descriptions used herein are accordingly interpreted.

[0026] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or connected to the other element through an intermediate element. In addition, "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if there is transmission of electrical signals or data between the connected objects. When used herein, the singular forms of "a", "an" and "the" may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "comprise / include" or "have" etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the related listed items.

[0027] The present invention provides a transceiver shared beamforming network based on a wavelength selective switch, specifically including: a multi-wavelength laser for generating optical carriers of multiple wavelengths; multiple optical switches for selecting receiving or transmitting branches; multiple electro-optic intensity modulators for modulating radio frequency (RF) transmission signals and RF echo signals received from each antenna onto the optical carriers; an erbium-doped fiber amplifier for amplifying optical signals; a 1×n optical splitter for equally power-dividing the multi-wavelength optical signals into n paths; multiple optical circulators for transmitting optical signals of each path along a specified path; multiple optical collimating couplers for collimating the output of optical signals from fiber to free space and coupling from free space to fiber; a diffraction grating for reflecting different wavelength components in each path of optical signals to different angles and modulating them by a phase-programmable liquid crystal on silicon (LCOS) device; an LCOS device for programming to control the phase of each liquid crystal pixel, for wavelength selection and amplitude selection of optical signals of each path, and the selected wavelength optical signals will be coupled into the fiber through the original optical path, while other unselected wavelengths will not be coupled into the fiber; multiple dispersion fibers for delaying optical signals of each path; multiple electrical circulators for isolating the receiving branch and the transmitting branch; a wavelength division multiplexer for optical upper beam synthesis; and multiple photodetectors for demodulating the optical carrier RF signals into RF signals.

[0028] For the general principle block diagram of this beamforming network, please refer to the appendix Figure 1 , assuming that this network includes n receive / transmit channels, then this network includes:

[0029] A multi-wavelength laser 1 for generating optical carriers. The multi-wavelength laser has m output wavelengths, which are λ 1 ~λ m , and the adjacent wavelengths maintain the same wavelength interval Δλ.

[0030] The first optical switch 2, the second optical switch 4, the 3rd to the (n + 2)th optical switches 7-1 to 7-n, the (n + 3)th to the (2n + 2)th optical switches 9-1 to 9-n, the (2n + 3)th to the (3n + 2)th optical switches 15-1 to 15-n, for selecting receiving or transmitting branches. All the optical switches in the present invention are 1×2 optical switches.

[0031] The first electro-optic intensity modulator 3, the 2nd to the (n + 1)th electro-optic intensity modulators 8-1 to 8-n, for modulating RF signals onto the optical carriers. Among them, the first electro-optic intensity modulator 3 is used for loading the RF transmission signal, and the 2nd to the (n + 1)th electro-optic intensity modulators 8-1 to 8-n are used for loading the RF echo signals received from each antenna.

[0032] An erbium-doped fiber amplifier 5 for gain amplification of optical signals.

[0033] A 1×n optical splitter 6 for dividing λ 1~λ m The multi-wavelength optical signal is equally divided into n paths with equal power.

[0034] The first to nth optical circulators 10-1 to 10-n are used for transmitting optical signals of each path along the specified path.

[0035] The first to nth optical collimating couplers 11-1 to 11-n are used for collimating the output of optical signals of each path from fiber to free space and coupling from free space to fiber.

[0036] The diffraction grating 12 is used to reflect different wavelength components in the optical signals of each path to different angles and is modulated by the phase-programmable liquid crystal on silicon device 13.

[0037] The liquid crystal on silicon device 13 (LCOS) controls the phase of each liquid crystal pixel through programming, and is used for wavelength selection and amplitude selection of the optical signals of each path. The selected wavelength optical signal will be coupled into the fiber through the original optical path, and other unselected wavelengths will not be coupled into the fiber.

[0038] The first to nth dispersion fibers 14-1 to 14-n are used for delaying the optical signals of each path. Parameters such as the length and dispersion coefficient of each dispersion fiber are kept consistent.

[0039] The first to nth photodetectors 16-1 to 16-n are used to demodulate the optical carrier radio frequency signal of the transmitting path and send the radio frequency signal to the antenna for transmission.

[0040] The first to nth radio frequency circulators 17-1 to 17-n are used to select the transmitting path or the receiving path.

[0041] The first to nth antennas 18-1 to 18-n are used for transmitting radio frequency signals or receiving echo signals.

[0042] The wavelength division multiplexer 19 is used for optical upper beam synthesis of the receiving path.

[0043] The photodetector 20 is used to demodulate the optical carrier radio frequency signal of the receiving path and send it to the subsequent processing unit.

[0044] Specifically, as Figure 1The output end of the multi-wavelength laser 1 shown is connected to the input end of the first optical switch 2. The output end of the first optical switch 2 is respectively connected to the input end of the first electro-optic intensity modulator 3 and the second input end of the second optical switch 4. The output end of the first electro-optic intensity modulator 3 is connected to the first input end of the second optical switch 4. The output end of the second optical switch 4 is connected to the input end of the 1×n optical splitter 6 through the erbium-doped fiber amplifier 5. The first to the nth output ends of the 1×n optical splitter 6 are respectively connected to the input ends of the 3rd to the (n + 2)th optical switches 7-1 to 7-n. The first output ends of the 3rd to the (n + 2)th optical switches 7-1 to 7-n are respectively connected to the input ends of the 2nd to the (n + 1)th electro-optic intensity modulators 8-1 to 8-n. The output ends of the 2nd to the (n + 1)th electro-optic intensity modulators 8-1 to 8-n are connected to the first input ends of the (n + 3)th to the (2n + 2)th optical switches 9-1 to 9-n; the second output ends of the 3rd to the (n + 2)th optical switches 7-1 to 7-n are respectively connected to the second input ends of the (n + 3)th to the (2n + 2)th optical switches 9-1 to 9-n in correspondence;

[0045] The output ends of the (n + 3)th to the (2n + 2)th optical switches 9-1 to 9-n are connected to the first ports of the first to the nth optical circulators 10-1 to 10-n. The second ports of the first to the nth optical circulators 10-1 to 10-n are respectively connected to the input ends of the (2n + 3)th to the (3n + 2)th optical switches 15-1 to 15-n through the first to the nth dispersion optical fibers 14-1 to 14-n in correspondence. The first output ends of the (2n + 3)th to the (3n + 2)th optical switches 15-1 to 15-n are respectively connected to the radio frequency input ports of the first to the nth radio frequency circulators 17-1 to 17-n through the first to the nth photodetectors 16-1 to 16-n in correspondence. The first to the nth dispersion optical fibers 14-1 to 14-n are connected to the wave division multiplexer 19 at the second output ends of the (2n + 3)th to the (3n + 2)th optical switches 15-1 to 15-n. The wave division multiplexer 19 is connected to the photodetector 20; the radio frequency output ports of the first to the nth radio frequency circulators 17-1 to 17-n are respectively connected to the radio frequency input ports of the 2nd to the (n + 1)th electro-optic intensity modulators 8-1 to 8-n in correspondence. The optical fiber ports of the first to the nth radio frequency circulators 17-1 to 17-n are respectively connected to the first to the nth antennas 18-1 to 18-n;

[0046] The third ports of the first to the nth optical circulators 10-1 to 10-n are respectively connected to the input ends of the first to the nth optical collimating couplers 11-1 to 11-n in correspondence. The output ends of the first to the nth optical collimating couplers 11-1 to 11-n are connected to the silicon-based liquid crystal device 13 through the diffraction grating 12;

[0047] All the optical switches are 1×2 optical switches, and n is a positive integer greater than or equal to 2.

[0048] Figure 1Among the components, the fiber optic optical path is connected by solid lines, the free space optical path is connected by dashed lines, and the RF path is connected by dotted lines.

[0049] This beamforming network has a typical microwave photonic link architecture. The transmitted / received signal is modulated by an electro-optic intensity modulator and then loaded onto an optical carrier. Then, optical delay is achieved through a wavelength selective switch composed of a diffraction grating and a liquid crystal on silicon device and a dispersion fiber. Finally, the RF signal is demodulated by a photodetector. The principles of the system operating in the transmit mode and the receive mode are described below using Application Examples 1 and 2 respectively.

[0050] Application Example 1: Beamforming network operating in the transmit mode.

[0051] The multi-wavelength laser 1 outputs continuous wave lasers with wavelengths of λ 1 , λ 2 , …, λ m , with an adjacent wavelength interval of Δλ. The first optical switch 2 and the second optical switch 4 are controlled to select Figure 1 the upper branch in the figure above. The RF transmit signal is modulated onto the optical carrier by the first electro-optic intensity modulator 3, amplified by an erbium-doped fiber amplifier 5, and equally divided into n paths by a 1×n optical splitter 6. Each path contains equal power wavelength components of λ 1 ~λ m . The 3rd to the (n + 2)th optical switches 7-1~7-n and the (n + 3)th to the (2n + 2)th optical switches 9-1~9-n are controlled to select Figure 1 the middle and lower branches in the figure above. After being collimated by the first to the nth optical circulators 10-1~10-n and the first to the nth optical collimating couplers 11-1~11-n, the light is output to free space.

[0052] The schematic diagram of the light signal transmission in free space is as shown in Figure 2 . The dashed lines represent the light transmission paths. The n collimated light beams arranged along the x direction all transmit along the y direction and are respectively irradiated to different x-direction positions of the diffraction grating 12, and are reflected by the diffraction grating 12 to the liquid crystal on silicon device 13 below. For the light signal containing wavelength components of λ 1 , λ 2 , …, λ m output from any optical collimating coupler 11-i (i = 1, 2, …, n), the diffraction grating 12 will reflect these wavelength components to different angles. The principle is: according to the generalized Snell's law, when light is reflected on a surface with a certain phase gradient , the relationship between the incident angle θ i and the reflection angle θ r can be expressed as:

[0053]

[0054] where n i is the refractive index of the medium (n = 1 in free space), λ is the wavelength of the incident light, and the diffraction grating 12 has a phase gradient distribution along the l direction i For the wavelength components of λ, λ, …, λ incident at the same incident angle θ, considering that the wavelengths gradually increase from λ to λ, the relationship between the corresponding reflection angles θ, θ, …, θ is that they gradually increase from θ to θ. For the wavelength components of λ, λ, …, λ incident at the same incident angle θ i incident λ 1 、λ 2 、…、λ m Considering λ 1 to λ m gradually increasing in wavelength, the reflection angles θ r1 、θ r2 、…、θ rm corresponding to these wavelength components are such that the relationship is that they gradually increase from θ r1 to θ rm gradually increases.

[0055] Therefore, different wavelength components in the same output channel will be reflected by the diffraction grating 12 to different y-direction positions of the underlying liquid crystal on silicon device 13. The output spots of the first to nth optical collimator couplers 11-1 to 11-n in the channel are arranged in sequence along the x direction on the liquid crystal on silicon device 13. The spot distributions of each channel and each wavelength on the liquid crystal on silicon device 13 are as Figure 3 shown.

[0056] The function of the liquid crystal on silicon device 13 is to couple a specific wavelength or several wavelengths in each channel back to the optical fiber along the original path, obtain the required time delay through subsequent dispersion optical fiber transmission, and can produce an amplitude modulation effect on the light coupled into the optical fiber. The principle is as follows:

[0057] The liquid crystal on silicon device 13 mainly consists of an upper glass cover plate, a quarter-wave plate, an ITO transparent electrode layer, a liquid crystal alignment layer, a middle liquid crystal layer, and a lower liquid crystal alignment layer and a pixelated metal electrode layer controlled by a silicon-based CMOS driver. The upper and lower liquid crystal alignment layers are used to pre-align the alignment direction of liquid crystal molecules. The ITO transparent electrode layer and the pixelated metal electrode layer are used to apply voltage to the liquid crystal layer. Under the drive of the electric field, the alignment direction of liquid crystal molecules will deflect, the equivalent refractive index will change, and a phase modulation effect on the incident light will be generated. The quarter-wave plate ensures the polarization-independent characteristic of this phase modulation effect. By programming the drive voltage at different pixel positions, an arbitrarily designed two-dimensional phase modulation distribution can be generated. In this embodiment, the spots of each channel and each wavelength will cover a certain area of the liquid crystal pixel region ( Figure 3 ). If the wavelength component of λ is selected in channel 1 and returns along the original path, the relationship between its reflection angle and incident angle is θ i =-θ r , and from formula (1), it is obtained that in channel 1, λ i , from the formula (1), the λ in channel 1 is obtainedi Phase distribution of the liquid crystal pixel region where the light spot is located It is necessary to satisfy:

[0058]

[0059] Since the phase distribution of the liquid crystal pixel region where the light spots of each channel and each wavelength are located can be independently controlled, any one wavelength or several wavelengths in each channel can be coupled back into the optical fiber along the original path, thereby achieving the wavelength selection effect.

[0060] In addition to wavelength selection, generating a specific phase gradient distribution in the x direction can cause the returned light to have a certain x-direction light spot offset relative to the optical collimator coupler 11-i, so that part of it is coupled into the optical fiber, forming an optical intensity modulation effect. The optical intensity modulation in the optical link will affect the intensity of the output radio frequency signal, and the relationship is: for every 1 dB loss of light, the output radio frequency loss is 2 dB.

[0061] The selected wavelengths in each channel enter the first to nth dispersion optical fibers 14-1 to 14-n through the first to nth optical circulators 10-1 to 10-n. When the parameters such as the length and dispersion coefficient of the dispersion optical fiber 14-i (i = 1, 2,..., n) are the same, the delay of light transmission in it is linearly related to the optical wavelength, so that a specific delay required for each channel can be obtained. The optical switches 15-1, 15-2,..., 15-n are switched to the left branch. After the optical carrier radio frequency signal is demodulated by the first to nth photodetectors 16-1 to 16-n to obtain the radio frequency signal, it is transmitted through the first to nth radio frequency circulators 17-1 to 17-n and the first to nth antennas 18-1 to 18-n.

[0062] Application Example 2: Beamforming network operating in the receiving mode.

[0063] The multi-wavelength laser 1 outputs continuous wave lasers with wavelengths of λ 1 , λ 2 , …, λ m , with an adjacent wavelength interval of Δλ. Control the first optical switch 2 and the second optical switch 4 to select Figure 1 the lower branch in, perform gain amplification through the erbium-doped fiber amplifier 5, and equally divide the optical signal into n paths through the 1×n optical splitter 6. Each path contains equal-power λ 1 ~λ m wavelength components, and control the 3rd to n+2nd optical switches 7-1 to 7-n and the n+3rd to 2n+2nd optical switches 9-1 to 9-n to select Figure 1The upper middle branch: The radio frequency echo signals received from the first to the nth antennas 18-1 to 18-n are modulated onto the optical carrier by the 2nd to the (n + 1)th electro-optic intensity modulators 8-1 to 8-n after passing through the first to the nth radio frequency circulators 17-1 to 17-n, and are collimated and output to free space after passing through the first to the nth optical circulators 10-1 to 10-n and the first to the nth optical collimating couplers 11-1 to 11-n.

[0064] The schematic diagram of the optical signal transmission in free space is as shown in Figure 2 Figure [not shown in the provided text, but assumed to be a reference figure]. The dotted lines represent the optical transmission paths. The n collimated light beams arranged along the x direction all propagate along the y direction, and are respectively irradiated onto different x-direction positions of the diffraction grating 12, and are reflected by the diffraction grating 12 to the liquid crystal on silicon device 13 below. After programmable phase modulation by the liquid crystal on silicon device 13, the selected wavelength returns along the original path and is coupled into the optical fiber, and enters the first to the nth dispersion optical fibers 14-1 to 14-n through the first to the nth optical circulators 10-1 to 10-n. The delay amount transmitted in the dispersion optical fibers of the same length has a linear relationship with the wavelength, so as to obtain the specific delay amount required for each channel. The optical switches 15-1, 15-2,..., 15-n are switched to the right branch. The optical carrier radio frequency signals of each channel are multiplexed by the wavelength division multiplexer 19 and then enter the photodetector 20 to demodulate the radio frequency signal, which is sent to the subsequent receiving and processing unit.

[0065] If the transmitting / receiving beam direction is ψ, the difference in delay amounts between adjacent channels should satisfy Δτ = dsinψ / c, where d is the antenna spacing between adjacent channels and c is the speed of light in vacuum. The wavelengths are λ i and λ j The delay difference generated by the light with wavelengths of λ j -λ i transmitting in the dispersion optical fiber with a length of L is Δτ = DL(λ m -λ 1 ), where D is the dispersion coefficient. By changing the wavelength difference between the maximum wavelength λ m and the minimum wavelength λ 1 of the multi-wavelength laser and the length of the dispersion optical fiber, the maximum delay amount can be changed, and the minimum delay accuracy is determined by the wavelength interval Δλ of the multi-wavelength laser.

[0066] The above two application examples illustrate the multi-channel arbitrary reconfigurable delay and amplitude modulation characteristics of this beamforming network in the receive / transmit state, which can be used in microwave photon phased arrays. Its advantages are mainly reflected in the following aspects:

[0067] (1)Advantages of the transceiver-sharing architecture over the transceiver-separated architecture: This beamforming network adopts a transceiver-sharing architecture and uses multiple optical switches to achieve fast switching between the receiving branch and the transmitting branch, enabling optical active devices such as multi-wavelength lasers, erbium-doped fiber amplifiers, free-space wavelength selection modules, and photodetectors, as well as optical passive devices such as optical power splitters, optical circulators, optical coupling collimators, and dispersion fibers to be shared for both transmission and reception. This greatly simplifies the system structure and improves the integration level.

[0068] (2)Advantages of the wavelength selection switch for optical delay: The wavelength selection switch composed of a diffraction grating and an LCOS can perform parallel wavelength selection on multiple optical signals and, in combination with dispersion fibers, achieve multi-channel optical delay. Compared with the optical delay scheme based on optical switch switching that requires independent delay control devices for each channel, it greatly simplifies the amount of optical delay equipment. Additionally, another significant advantage of this technical solution is its high reconfigurability. Any one or several wavelengths in any transmit / receive path can achieve wavelength selection by dynamically uploading a phase hologram with a specific design for the LCOS, realizing any set or several sets of different array delays, thereby achieving arbitrary multi-beamforming. At the same time, since the delay and amplitude of the radio frequency signal can be regulated simultaneously, low sidelobe beamforming can also be achieved.

[0069] In summary, the present invention provides a transceiver-sharing beamforming network based on a wavelength selection switch, which can achieve multi-channel arbitrary reconfigurable delay and amplitude regulation characteristics for transceiver sharing, realizing a microwave photonic beamforming network. In terms of architecture, it adopts a transceiver-sharing architecture, greatly simplifies the system structure, and improves the integration level. It uses a wavelength selection switch composed of a diffraction grating and an LCOS to perform parallel wavelength selection on multiple optical signals and, in combination with dispersion fibers, achieve multi-channel optical delay, significantly simplifying the optical delay system and breaking through the technical bottleneck of the existing optical true delay system with a large amount of equipment and the inability to achieve multi-channel parallel optical delay through a single device. It provides a highly reconfigurable optical delay scheme to realize any set or several sets of different array delays, thereby achieving arbitrary multi-beamforming. At the same time, since the delay and amplitude of the radio frequency signal can be regulated simultaneously, low sidelobe beamforming can also be achieved.

[0070] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A transmit-receive shared beamforming network based on a wavelength selective switch, characterized in that, it includes a multi-wavelength laser (1), the output end of the multi-wavelength laser (1) is connected to the input end of a first optical switch (2), the output end of the first optical switch (2) is respectively connected to the input end of a first electro-optic intensity modulator (3) and the second input end of a second optical switch (4), the output end of the first electro-optic intensity modulator (3) is connected to the first input end of the second optical switch (4), the output end of the second optical switch (4) is connected to the input end of a 1×n optical splitter (6) through an erbium-doped fiber amplifier (5), the first to the nth output ends of the 1×n optical splitter (6) are respectively connected to the input ends of the 3rd to the (n + 2)th optical switches (7-1 to 7-n), the first output ends of the 3rd to the (n + 2)th optical switches (7-1 to 7-n) are respectively connected to the input ends of the 2nd to the (n + 1)th electro-optic intensity modulators (8-1 to 8-n), and the output ends of the 2nd to the (n + 1)th electro-optic intensity modulators (8-1 to 8-n) are connected to the first input ends of the (n + 3)th to the (2n + 2)th optical switches (9-1 to 9-n); the second output ends of the 3rd to the (n + 2)th optical switches (7-1 to 7-n) are respectively and correspondingly connected to the second input ends of the (n + 3)th to the (2n + 2)th optical switches (9-1 to 9-n); the output ends of the (n + 3)th to the (2n + 2)th optical switches (9-1 to 9-n) are connected to the first ports of the first to the nth optical circulators (10-1 to 10-n), the second ports of the first to the nth optical circulators (10-1 to 10-n) are respectively and correspondingly connected to the input ends of the (2n + 3)th to the (3n + 2)th optical switches (15-1 to 15-n) through the first to the nth dispersion fibers (14-1 to 14-n), the first output ends of the (2n + 3)th to the (3n + 2)th optical switches (15-1 to 15-n) are respectively and correspondingly connected to the radio frequency input ports of the first to the nth radio frequency circulators (17-1 to 17-n) through the first to the nth photodetectors (16-1 to 16-n), the second output ends of the first to the nth dispersion fibers (14-1 to 14-n) and the (2n + 3)th to the (3n + 2)th optical switches (15-1 to 15-n) are connected to a wavelength division multiplexer (19), and the wavelength division multiplexer (19) is connected to a photodetector (20); the radio frequency output ports of the first to the nth radio frequency circulators (17-1 to 17-n) are respectively and correspondingly connected to the radio frequency input ports of the 2nd to the (n + 1)th electro-optic intensity modulators (8-1 to 8-n), and the fiber ports of the first to the nth radio frequency circulators (17-1 to 17-n) are respectively connected to the first to the nth antennas (18-1 to 18-n); the third ports of the first to the nth optical circulators (10-1 to 10-n) are respectively and correspondingly connected to the input ends of the first to the nth optical collimating couplers (11-1 to 11-n), and the output ends of the first to the nth optical collimating couplers (11-1 to 11-n) are connected to a silicon-based liquid crystal device (13) through a diffraction grating (12); all the optical switches are 1×2 optical switches, and n is a positive integer greater than or equal to 2.

2. The transmit-receive shared beamforming network based on a wavelength selective switch according to claim 1, wherein, The multi-wavelength laser (1) has m output wavelengths, which are λ 1 ~λ m , and adjacent wavelengths maintain the same wavelength interval Δλ.

3. The transmit-receive shared beamforming network based on a wavelength selective switch according to claim 2, wherein, the first electro-optic intensity modulator (3) is used to load a radio frequency transmission signal, and the 2nd to the (n + 1)th electro-optic intensity modulators (8-1 to 8-n) are used to load radio frequency echo signals received from each antenna.

4. The transmit-receive shared beamforming network based on a wavelength selective switch according to claim 3, wherein, The diffraction grating (12) has a phase gradient distribution with a fixed period in the long direction, that is where is the phase of the diffraction grating (12), l is the long side of the diffraction grating (12), and Λ is the grating period.

5. The transmit-receive shared beamforming network based on a wavelength selective switch according to claim 4, wherein, The liquid crystal on silicon device (13) has a number of liquid crystal pixels in the length and width directions, and precise phase regulation on each pixel is achieved through pixelated metal electrodes controlled by the underlying silicon-based CMOS drive. Since the light spots of each channel and each wavelength will cover a certain area of the liquid crystal pixel region, if a wavelength component λ in a certain channel is selected i to return along the original path, the phase distribution in the area where its light spot is located should satisfy: where is the required phase distribution of the liquid crystal on silicon device in this area, and θ i is the incident angle of λ i incident on the liquid crystal on silicon device.

6. The transmit-receive shared beamforming network based on a wavelength selective switch according to claim 5, wherein, the silicon-based liquid crystal device (13) generates a specific phase gradient distribution in the x direction, causing the returned light to have a spot offset in the x direction relative to the ith optical collimator 11-i, such that part of it is coupled into the optical fiber, forming an optical intensity modulation effect; the optical intensity modulation in the optical link affects the intensity of the output radio frequency signal, and the relationship is: for every 1 dB increase in optical loss, the output radio frequency loss increases by 2 dB; where i = 1, 2,..., n.

7. A transmit-receive shared beamforming network based on a wavelength selective switch according to claim 6, wherein, The lengths and dispersion coefficients of the multiple dispersion optical fibers are kept consistent, and the wavelength is λ i and λ j The delay difference generated by the optical light with wavelengths of λ j -λ i propagating in the dispersion optical fiber with a length of L is Δτ = DL(λ m -λ 1 ), where D is the dispersion coefficient. By changing the wavelength difference between the maximum wavelength λ m and the minimum wavelength λ 1 of the multi-wavelength laser (1) and the length of the dispersion optical fiber, the maximum delay amount is changed, and the minimum delay accuracy is determined by the wavelength interval Δλ of the multi-wavelength laser (1); if the transmitting / receiving beam direction is ψ, the delay amount difference between adjacent channels satisfies Δτ = dsinψ / c, where d is the antenna spacing between adjacent channels and c is the speed of light in vacuum.

8. A transmit-receive shared beamforming network based on a wavelength selective switch according to claim 2, wherein, When the transmit-receive shared beamforming network operates in the transmit mode, the multi-wavelength laser (1) outputs continuous-wave lasers with wavelengths of λ 1 , λ 2 , …, λ m , with an adjacent wavelength interval of Δλ. The first optical switch (2) and the second optical switch (4) are controlled to select the upper branch. The radio frequency transmit signal is modulated onto the optical carrier by the first electro-optic intensity modulator (3), amplified in gain by the erbium-doped fiber amplifier (5), and equally divided into n paths by the 1×n optical splitter (6). Each path contains equal-power wavelength components of λ 1 to λ m . The 3rd to (n + 2)th optical switches (7-1 to 7-n) and the (n + 3)th to (2n + 2)th optical switches (9-1 to 9-n) are controlled to select the lower branch, and are collimated and output to free space after passing through the first to nth optical circulators (10-1 to 10-n) and the first to nth optical collimating couplers (11-1 to 11-n).

9. A transmit-receive shared beamforming network based on a wavelength selective switch according to claim 2, wherein, When the transmit-receive common beamforming network operates in the receive mode, the multi-wavelength laser (1) outputs continuous-wave lasers with wavelengths of λ 1 , λ 2 , …, λ m , where the adjacent wavelength intervals are Δλ. The first optical switch (2) and the second optical switch (4) are controlled to select the lower branch, and the signal is amplified by the erbium-doped fiber amplifier (5). The optical signal is equally divided into n paths by the 1×n optical splitter (6), and each path contains equal-power wavelength components of λ 1 to λ m . The 3rd to (n + 2)th optical switches (7-1 to 7-n) and the (n + 3)th to (2n + 2)th optical switches (9-1 to 9-n) are controlled to select the upper branch. The radio frequency echo signals received from the first to nth antennas (18-1 to 18-n) are modulated onto the optical carrier by the 2nd to (n + 1)th electro-optic intensity modulators (8-1 to 8-n) after passing through the first to nth radio frequency circulators (17-1 to 17-n), and are collimated and output to free space after passing through the first to nth optical circulators (10-1 to 10-n) and the first to nth optical collimating couplers (11-1 to 11-n).

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