CN114879166B - Directional multi-beam radar signal receiving device and method - Google Patents
Directional multi-beam radar signal receiving device and method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
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- G01S7/4802—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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Abstract
The embodiment of the disclosure discloses a directional multi-beam radar signal receiving device and a method, wherein the device comprises: the system comprises a multi-wavelength light source array unit, a radio frequency echo signal receiving and modulating unit, a multi-beam forming network unit, a signal frequency conversion and sampling processing unit and a control unit; the multi-wavelength light source array unit is used for simultaneously generating N paths of continuous optical carrier signals with different central wavelengths; n is a natural number greater than 1; the radio frequency echo signal receiving and modulating unit is used for modulating N paths of radar echo signals received by N receiving antennas on the N paths of optical carrier signals with different center wavelengths respectively, and sending the N paths of modulated optical signals to the optical multi-beam forming network unit; the multi-beam forming network unit is used for respectively carrying out amplitude adjustment and delay amount matching on the received N paths of modulated optical signals, and realizing synthesis of M beam directions while completing photoelectric conversion in M photoelectric detectors; m is a natural number greater than 1; the signal frequency conversion and sampling processing unit performs frequency conversion and analog-to-digital conversion processing on the echo signals after beam synthesis.
Description
Technical Field
The disclosure relates to the technical field of radar and imaging, in particular to a directional multi-beam radar signal receiving device and method.
Background
With the rapid development of the spaceborne high-resolution wide-width synthetic aperture radar, the important trend is to further improve the mapping breadth and imaging precision and speed of the synthetic aperture radar. Most of the traditional spaceborne synthetic aperture radars still have single-beam or split-antenna subarray multi-beam schemes, and have the problems of wide antenna beam angle, small antenna gain, long mapping scanning and the like, so that the traditional spaceborne synthetic aperture radars are more limited in the future more complex application environments. The spaceborne synthetic aperture radar with rapid mapping, high resolution and large-breadth imaging capability becomes a big research hotspot.
The existing satellite-borne synthetic aperture radar mainly comprises a single-beam scanning mode or a mode that a plurality of sub-antenna arrays are respectively controlled to form a beam, wherein the single-beam scanning mode has the defects of low antenna gain, low mapping scanning speed and the like, and the mode that multi-beam scanning is realized by dividing the single-beam scanning mode into a plurality of sub-antenna arrays loses the advantages of a large antenna array, so that parameters such as antenna beam gain, beam width and the like are limited. At present, for the scheme of a receiver for realizing multi-beam formation by utilizing a microwave photon technology, most of the schemes are still based on multi-beam matrix architectures of a traditional electronic radar system, such as Butler matrix, nolen matrix, blast matrix and the like, and a phase shifter of light is combined, so that the problems of high matrix network loss and the like inherent to the matrix architecture of the traditional electronic radar system are overcome. But the use of phase shifting schemes limits the bandwidth of the overall receiving system, typically on the order of hundred megahertz.
In summary, the existing radar beam forming architecture has the problems that single beam ranging and imaging scanning speed is low, the advantage of a large antenna array is difficult to develop due to the fact that multiple beams are formed by a molecular array, bandwidth limitation of the multiple beam forming network architecture in a traditional electronic system is difficult to achieve, and the like.
Disclosure of Invention
The embodiment of the disclosure provides a directional multi-beam radar signal receiving device and a method.
In a first aspect, an embodiment of the present disclosure provides a directional multi-beam radar signal receiving apparatus, including: the system comprises a multi-wavelength light source array unit, a radio frequency echo signal receiving and modulating unit, a multi-beam forming network unit, a signal frequency conversion and sampling processing unit and a control unit; wherein,
The multi-wavelength light source array unit is used for simultaneously generating N paths of continuous optical carrier signals with different central wavelengths; n is a natural number greater than 1;
The radio frequency echo signal receiving and modulating unit is used for modulating N paths of radar echo signals received by N receiving antennas on the N paths of optical carrier signals with different center wavelengths respectively, and sending the N paths of modulated optical signals to the optical multi-beam forming network unit;
the multi-beam forming network unit is used for respectively carrying out amplitude adjustment and delay amount matching on the received N paths of modulated optical signals, so that M different delay gradients are formed between two adjacent paths of modulated optical signals according to preset M different beam directions, and the modulated optical signals with the same delay gradient are sent to the same photoelectric detector for photoelectric conversion after being combined to obtain echo signals after beam synthesis; m is a natural number greater than 1;
the signal frequency conversion and sampling processing unit performs frequency conversion and analog-to-digital conversion processing on the echo signals after beam synthesis;
The control unit is used for controlling the pumping current and wavelength tuning of the laser generating N paths of optical carrier signals with different central wavelengths and controlling the selection of the power and delay amount of each path of modulated optical signals output by the multi-beam forming network unit.
Further, the multi-wavelength light source array unit includes:
n wavelength tunable lasers for generating N incoherent optical carrier signals having a predetermined wavelength interval; and/or the number of the groups of groups,
The radio frequency echo signal receiving and modulating unit comprises:
N receiving antennas for receiving radar echo signals;
the N low-noise amplifiers are used for amplifying the radar echo signals and controlling noise coefficients of the radar echo signals;
n electrical filters for removing out-of-band spurious emissions of the radar echo signal after being transmitted through the low noise amplifier;
n electro-optical modulators for modulating the radar echo signals processed by the electrical filters on optical carrier signals of different wavelengths; and/or the number of the groups of groups,
The multi-beam forming network element comprises:
The M multiplied by N optical path splitting nodes are used for tuning the power ratio of each path of modulated optical signals in the beam pointing synthesis, and combining the modulated optical signals corresponding to different receiving antennas pointed by the same beam;
m groups of optical delay modules are used for delaying the modulated optical signals;
The M photoelectric detectors are used for performing photoelectric conversion on the delayed modulated optical signals after beam combination and outputting echo signals after beam combination; and/or the number of the groups of groups,
The signal frequency conversion and sampling processing unit comprises:
M electric mixers for down-converting the echo signals after beam synthesis to intermediate frequency to obtain intermediate frequency signals;
and the analog-to-digital conversion and signal processing module is used for digitally sampling the intermediate frequency signal output by the electric mixer.
Further, the control unit includes:
The laser pumping current and wavelength control module is used for controlling the optical power and the wavelength of the optical carrier signal output by the laser;
and the multi-beam forming network optical path splitting node control module is used for controlling the power ratio of the modulated optical signals received by the multi-beam forming network unit to the directions of all the beams.
Further, the optical path splitting node includes:
A tunable optical coupler for tuning the power duty cycle of the modulated optical signal in each beam pointing composition;
and the beam combiner is used for combining modulated optical signals corresponding to different receiving antennas pointed by the same beam.
Further, the tunable optical coupler includes a1×2 optical coupler, an optical phase shifter, and a2×2 optical coupler; a first modulated optical signal enters the tunable optical coupler from a first input port of the optical path splitting node; the tunable optical coupler divides the first modulated optical signal into a first beam of optical signal and a second beam of optical signal, the first beam of optical signal is output from a first output port of the optical path splitting node, and the second beam of optical signal is combined with a second modulated optical signal input from a second input port of the optical path splitting node at the optical combiner and is output from a second output port of the optical path splitting node.
Further, the tunable optical coupler is realized by adopting a combination mode of a Mach-Zehnder interferometer and an optical phase shifter, and a carrier control mode is adopted for the phase shift amount control mode of the optical phase shifter.
In a second aspect, an embodiment of the present disclosure provides a directional multi-beam radar signal receiving method, including:
The multi-wavelength light source array unit simultaneously generates N paths of continuous optical carrier signals with different central wavelengths, and sends the optical carrier signals into the radio frequency echo signal receiving and modulating unit;
The radio frequency echo signal receiving and modulating unit receives N paths of radar echo signals by using N receiving antennas, modulates the N paths of radar echo signals on N paths of optical carrier signals with different center wavelengths respectively, and sends the obtained N paths of modulated optical signals to an optical multi-beam forming network unit;
The multi-beam forming network unit is used for respectively carrying out amplitude adjustment and delay amount matching on the received N paths of modulated optical signals, so that M different delay gradients are formed between two adjacent paths of modulated optical signals according to preset M different beam directions, the modulated optical signals with the same delay gradient are sent to the same photoelectric detector for photoelectric conversion after being combined, and the obtained echo signals after beam synthesis are sent to the signal frequency conversion and sampling processing unit;
the signal frequency conversion and sampling processing unit performs frequency conversion and analog-to-digital conversion processing on the echo signals after beam synthesis.
Further, the modulated optical signal entering the first input port of the multi-beam forming network unit is tuned by the tunable optical coupler of the multi-beam forming network unit, then enters the first layer delay module corresponding to the i-th beam direction, and is combined with the i-th beam combiner of the modulated optical signal of the second input port on the second layer input path, then enters the second layer delay module corresponding to the i-th beam direction together, the steps are repeated until the modulated optical signal entering the last input port is combined with the i-th beam combiner of the modulated optical signal of the last input port on the N-th layer input path, and then is sent to the i-th photoelectric detector for photoelectric conversion, and the echo signal after beam combination is output, and then sent to the signal frequency conversion and sampling processing unit by the i-th output port of the multi-beam forming network unit.
The technical scheme provided by the embodiment of the disclosure can comprise the following beneficial effects:
(1) By utilizing the structural advantages of the multi-beam network matrix, the radar echo signals pointed by a plurality of beams can be received simultaneously, the number of the beams and the number of the antennas can be arbitrarily expanded, and the synthesis reception of narrow beams at any angle can be realized within a large radiation angle range, so that the gain of the received beams can be greatly improved, and the performance of a receiver can be improved;
(2) The multi-beam receiving method can simultaneously perform multi-beam receiving, is favorable for rapidly ranging and imaging targets, can relieve the limitation of maximum non-fuzzy distance in a wide-range scene, and has wide application value and potential in the application scene of the spaceborne high-resolution wide-range synthetic aperture radar.
(3) The device has compact structure, is beneficial to realizing the integration of the system on chip and is also beneficial to realizing the expansion of the large-scale integrated beam forming network.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
Other features, objects and advantages of the present disclosure will become more apparent from the following detailed description of non-limiting embodiments, taken in conjunction with the accompanying drawings. In the drawings:
Fig. 1 illustrates a schematic structure of a directional multi-beam radar signal receiving apparatus based on a true delay network according to an embodiment of the present disclosure;
Fig. 2 is a schematic diagram illustrating an implementation structure of an optical path splitting node in a multi-beam forming network unit according to an embodiment of the present disclosure;
fig. 3 shows a flow chart of a directional multi-beam radar signal receiving method according to an embodiment of the present disclosure.
Detailed Description
Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement them. In addition, for the sake of clarity, portions irrelevant to description of the exemplary embodiments are omitted in the drawings.
In this disclosure, it should be understood that terms such as "comprises" or "comprising," etc., are intended to indicate the presence of features, numbers, steps, acts, components, portions, or combinations thereof disclosed in this specification, and do not preclude the presence or addition of one or more other features, numbers, steps, acts, components, portions, or combinations thereof.
In addition, it should be noted that, without conflict, the embodiments of the present disclosure and features of the embodiments may be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
In order to overcome the defects of the existing spaceborne synthetic aperture radar in ranging and imaging, the invention provides a directional multi-beam radar receiving device and method based on a true delay network, which are oriented to the requirements of the spaceborne high-resolution and large-breadth synthetic aperture radar.
Fig. 1 illustrates a schematic structure of a directional multi-beam radar signal receiving apparatus based on a true delay network according to an embodiment of the present disclosure. As shown in fig. 1, the directional multi-beam radar signal receiving apparatus includes: the system comprises a multi-wavelength light source array unit, a radio frequency echo signal receiving and modulating unit, a multi-beam forming network unit, a signal frequency conversion and sampling processing unit and a control unit; wherein:
A multi-wavelength optical source array unit, as shown in part i of fig. 1, is configured to simultaneously generate N consecutive optical carrier signals OS1, OS2, …, OSN having different center wavelengths. The number of the light sources is the same as that of the antenna radiating subunits in the one-dimensional antenna array, and the number of the light sources is N; m and N are natural numbers greater than 1.
The radio frequency echo signal receiving and modulating unit, as shown in part ii in fig. 1, modulates N echo signals received by the N receiving antenna radiating subunits on N optical carrier signals with different wavelengths output by the multi-wavelength light source array unit one by using N mach-zehnder modulators, and sends the N modulated optical signals into a subsequent optical multi-beam forming network unit.
The multi-beam forming network unit, as shown in part iii in fig. 1, is configured to perform amplitude adjustment and delay amount matching on N paths of modulated optical signals, so that M groups of delay modules with different delay waveguide lengths are constructed between two adjacent paths of input modulated optical signals according to the required M different beam orientations, and the modulated optical signals passing through the delay modules with the same delay waveguide length are sent to the same photodetector to perform photoelectric conversion, thereby equivalently implementing different delay ladder amounts corresponding to the different beam orientations required to be formed between any two adjacent receiving antennas, and finally completing the synthesis of M beams with different orientations.
The signal frequency conversion and sampling processing unit is shown as part IV in FIG. 1 and is used for carrying out subsequent down-conversion, analog-to-digital conversion and subsequent signal processing on the echo signals after beam synthesis.
The control unit is shown in a V part in fig. 1 and is used for controlling pumping current and wavelength tuning of lasers for generating N paths of continuous optical carrier signals with different center wavelengths, so that cross mixing between optical signals passing through different delay waveguide lengths during photoelectric conversion is avoided; and the device is also used for controlling the selection of the power and the delay waveguide length of each path of the optical signal output in the multi-beam forming network unit so as to realize the power required by the corresponding beam pointing and the delay gradient between adjacent antenna subunits, thereby realizing the simultaneous operation of a plurality of different beam pointing.
The multi-wavelength light source array unit includes:
n wavelength tunable lasers for generating N incoherent optical carrier signals having a wavelength interval;
The radio frequency echo signal receiving and modulating unit comprises:
N receiving antennas for receiving radar echo signals;
the N low-noise amplifiers are used for amplifying radar echo signals received by the receiving antennas and controlling noise coefficients of the whole radar receiving system;
n electrical filters for filtering out-of-band spurious emissions in the received radar echo signals;
N electro-optical modulators (Mach-Zehnder modulators) for modulating the received radar echo signals on optical carrier signals with different wavelengths to obtain adjusted optical signals with different wavelengths;
The multi-beam forming network element comprising:
And the M multiplied by N optical path splitting nodes are used for tuning the power duty ratio of each path of modulated optical signals in the beam pointing synthesis, and combining the modulated optical signals corresponding to different receiving antennas pointed by the same beam. The optical path splitting node is shown as a black origin in fig. 1. For example, in fig. 1, after a first path of modulated optical signal correspondingly input from the electro-optical modulator 1 is delayed by a first delay module delay τ 1,1 of the first group of delay modules τ 1,1,τ1,2,…,τ1,N-1, the first path of modulated optical signal and a second path of modulated optical signal correspondingly input from the electro-optical modulator 2 are combined at corresponding optical path splitting nodes.
M groups of optical delay modules, each group of optical delay modules comprises (N-1) optical delay lines with equal delay amount, namely, each column of optical delay modules in FIG. 1 is a group, for example, the first group of optical delay modules is tau 1,1,τ1,2,…,τ1,N-1. The optical delay line lengths of the different groups of optical delay modules are different and correspond to the preset antenna beam directions one by one. The M groups of optical delay modules are used for delaying the modulated optical signals, and delay gradients corresponding to the beam directions are constructed among different paths of modulated optical signals.
The M photoelectric detectors are used for performing photoelectric conversion on each path of modulated optical signals after delay beam combination, and each photoelectric detector outputs an echo signal after beam combination;
The mxn optical path splitting nodes include:
M×n tunable optical couplers, each of the tunable optical couplers including a1×2 optical coupler, an optical phase shifter, and a2×2 optical coupler, for tuning a power ratio of each of the modulated optical signals in each of the beam-pointing combinations;
m x N beam combiners, which are used for combining the modulated optical signals corresponding to different receiving antennas pointed by the same beam;
The signal frequency conversion and sampling processing unit comprises:
M electric mixers for down-converting the echo signals after beam synthesis to intermediate frequency, which can reduce the requirement of sampling rate of analog-to-digital converter, and facilitate the subsequent digital sampling and signal processing.
And the analog-to-digital conversion and signal processing module is used for digitally sampling the intermediate frequency signal output by the electric mixer, converting the signal into a digital domain, and processing and analyzing the signal after beam synthesis by combining a subsequent radar signal processing algorithm.
The control unit includes:
The laser pumping current and wavelength control module is used for controlling the optical power of the optical carrier signal output by the multi-wavelength laser array and tuning the wavelength of the laser array;
The multi-beam forming network optical path splitting node control module is used for controlling the power percentage of each modulated optical signal received by the multi-beam forming network unit to be directed at each beam so as to realize the multi-beam directing function;
Fig. 2 illustrates a schematic diagram of an implementation structure of an optical path splitting node in a multi-beam forming network element according to an embodiment of the present disclosure. As shown in fig. 2, each optical path splitting node includes a tunable optical coupler and an optical combiner, wherein the tunable optical coupler includes a1 x 2 optical coupler, an optical phase shifter, and a 2 x 2 optical coupler. The optical path splitting node comprises two optical input ports and two optical output ports, and the two input ports respectively correspond to different input signals. The signal 1 directly enters the tunable optical coupler from the first input port, the tunable optical coupler divides the signal 1 into two parts, the signal 1 output from the a end is output from the first output port 1, the signal 1 output from the b end and the signal 2 input from the second input port are combined at the beam combiner, and then the signal 1 is output from the second output port. The splitting node may change the percentage of the optical signal output from both ends a, b of signal 1 by tuning the optical phase shifter in the tunable coupler.
In some embodiments, the tunable optical coupler is implemented using a combination of a Mach-Zehnder interferometer (MZI) and an optical phase shifter, the amount of phase shift of which is controlled by a selected carrier control. The phase shift control scheme of the optical phase shifter can be divided into three types of temperature control, carrier control and stress control, the tuning speed of the temperature control is slower, thermal crosstalk is easy to cause, and heat insulation treatment is needed additionally; the piezoelectric ceramic material is needed for stress control, and the tuning speed of the scheme is high, but the piezoelectric ceramic material is high in price and is more fragile in an actual working environment; in comparison, the tuning speed and cost of carrier control are more suitable.
Fig. 3 shows a flow chart of a directional multi-beam radar signal receiving method according to an embodiment of the present disclosure. As shown in fig. 3, the directional multi-beam radar signal receiving method includes the steps of:
In step S301, the multi-wavelength light source array unit simultaneously generates N paths of continuous optical carrier signals with different center wavelengths, and sends the optical carrier signals to the radio frequency echo signal receiving and modulating unit. In the multi-wavelength light source array unit, N laser sources simultaneously generate N paths of mutually incoherent continuous optical carrier signals with different central wavelengths and certain intervals through a laser pumping current and wavelength control module in a control unit, and the N paths of continuous optical carrier signals are sent to a subsequent radio frequency echo signal receiving and modulating unit;
in step S302, the rf echo signal receiving and modulating unit receives N paths of radar echo signals by using N receiving antennas, modulates the N paths of radar echo signals on the N paths of optical carrier signals with different center wavelengths, and sends the obtained N paths of modulated optical signals to an optical multi-beam forming network unit. In a radio frequency echo signal receiving and modulating unit, after the radar echo signals directly received by N receiving antennas are amplified and filtered by a low noise amplifier and an electric filter, respectively modulating the radar echo signals on the N paths of optical carrier signals with different central wavelengths by N Mach-Zehnder modulators, and sending the modulated optical signals to a subsequent multi-beam forming network unit, wherein the Mach-Zehnder modulators work at orthogonal offset points;
In step S303, the multi-beam forming network unit is configured to perform amplitude adjustment and delay amount matching on the received N paths of modulated optical signals, so that two adjacent paths of modulated optical signals are formed into different delay waveguide lengths according to preset M different beam directions, the modulated optical signals with the same delay waveguide length are sent to the same photodetector to perform photoelectric conversion after being combined, and the obtained echo signals after beam synthesis are sent to the signal frequency conversion and sampling processing unit. In a multi-beam forming network element there are N input ports and M output ports. The N input ports are in one-to-one correspondence with N output ports of the radio frequency echo signal receiving and modulating unit, and the M output ports are corresponding to M wave beam directions. Taking the i-th beam direction as an example, a first input port of the multi-beam forming network unit (i.e. the uppermost input port in the multi-beam forming network unit in fig. 1) enters the network, through tuning the first i-stage tunable optical coupler on the path, the modulated optical signals input by the port all enter the delay module corresponding to the i-th beam direction, then the i-th optical coupler on the second layer path and the signals of the second input port are combined, and pass through the second layer delay module together, and so on, the optical signals of the N input ports are sent to the i-th photoelectric detector for photoelectric conversion by taking the fixed delay module corresponding to the i-th beam direction as a delay gradient, the echo signals after beam synthesis are finally sent to the subsequent signal frequency conversion and sampling processing unit by the i-th output port. The above is a process of single beam synthesis, if multi-beam synthesis is to be performed simultaneously, only the splitting ratio of each tunable coupler needs to be changed, so as to control the power contribution of the optical signal of each input port to each beam, thereby completing multi-beam simultaneous synthesis. And then, the signals synthesized by the M paths of wave beam forming networks are respectively sent to M photoelectric detectors. Carrying out coherent superposition on each echo signal with different delay amounts while completing the conversion from light to electricity to form a radar echo signal with specific beam pointing;
In step S304, the signal frequency conversion and sampling processing unit performs frequency conversion and analog-to-digital conversion processing on the echo signal after beam synthesis. In the signal frequency conversion and sampling processing unit, the M paths of wave beam-oriented synthesized radar echo signals are respectively sent into M electric mixers to carry out down-conversion operation, so that the echo signals are converted from radio frequency to intermediate frequency, and the requirement on the sampling rate of a subsequent analog-to-digital converter is reduced. And then sending the intermediate frequency signal into an analog-to-digital conversion and signal processing module for sampling processing, converting the signal into a digital domain, and processing and analyzing the radar echo signal after beam synthesis by combining a corresponding radar signal processing algorithm.
As shown in fig. 1, in an embodiment of the present disclosure, a directional multi-beam radar signal receiving apparatus may include: the device comprises N tunable laser sources, laser source control modules, N radio frequency receiving antennas, N low-noise amplifiers, N electric filters, N electro-optic modulators, M multiplied by N tunable optical couplers, M multiplied by N optical combiners, M groups of optical delay modules (each group comprises N-1 optical delay lines with equal length), M photoelectric detectors and M frequency mixing and analog-to-digital conversion modules.
Since the signal phase of each antenna sub-unit determines the final beam pointing during multi-beam forming, the influence of the signal amplitude is small, and the amplitude is ignored in the following derivation. In the multi-wavelength light source array unit, N optical carrier signals OS1, OS2, OS3 … OSN with different frequencies and a frequency interval Δω are respectively output by controlling the laser pump and the N lasers of the wavelength control module, and the frequencies thereof are ω 1,ω2,ω3,...,ωN respectively. Assuming that the radar echo signal received by the radar receiving system is a linear frequency modulation signal, for facilitating the subsequent formula derivation, the radio frequency echo signal is represented by a sine signal form, namelyWherein ω RF is the start frequency of the rf echo signal, γ is the frequency modulation of the rf echo signal, and t is the time variable … …. The following describes the beam forming process in detail using the ith beam forming as an example:
First, the relationship between the phase difference Δψ between adjacent receiving antenna subunits and the beam pointing is as follows:
where d represents the spacing between adjacent antenna subunits, θ is the deflection angle of the antenna beam, i.e. the angle between the beam direction and the array surface normal, and λ represents the wavelength of the echo signal. As can be seen from equation (1), the phase difference between adjacent antenna subunits required for beam synthesis is related to the wavelength of the received echo signal, so for wideband radar signals, it is difficult to implement accurate beam pointing control by the phase shifting method. Therefore, the device in the present disclosure adopts a true delay scheme, and can avoid the problem of beam tilt introduced by the conventional phase shifting scheme.
In the embodiment of the present disclosure, the kth optical carrier OSk signal (i.e., at the a point in fig. 1) generated by the multi-wavelength optical source array unit may be expressed as:
Ek＝exp(-jωkt) (2)
where k=1, 2,3, …, N, ω k is the frequency of the kth optical carrier.
In the radio frequency echo signal receiving modulation unit, the low noise amplifier and the filter basically only work on the amplitude of the echo signal received by the radio frequency receiving antenna, so that the influence of the two modules on the subsequent beam forming can be ignored. Thus, an optical signal of an optical carrier modulated by a radio frequency echo signal at an electro-optic modulator can be expressed as:
Wherein J n represents the n-order second class bessel function, the electro-optic modulator works at the orthogonal bias point, and the high-order sideband signals of 2 nd order and above can be ignored due to the small signal model. The signals output by each optical carrier and sideband signal after the ith row of beams are combined (i.e. at point b in fig. 1) through the beam forming network unit can be expressed as:
Wherein τ i is the delay amount corresponding to the ith column of optical delay module, and is also the delay gradient value corresponding to the ith beam pointing, and the delay amount can be expressed as:
where n is the refractive index in the optical medium, L is the length of the optical waveguide, and c is the speed of light in vacuum.
In the signal frequency conversion and sampling processing unit, each path of signal after delay and beam combination enters the ith photoelectric detector to perform photoelectric conversion, and a photocurrent signal (i.e. point c in fig. 1) generated by the photoelectric detector can be expressed as:
Where d.c. represents the direct current component generated by the photodetector, which has no effect on subsequent signal processing and can be filtered out by an electrical filter, so that the direct current component can be ignored here.
The electric signal output by the photoelectric detector is superposition of radio frequency signals of different stages of delay modules, and the wave beam direction corresponding to the delay gradient tau i can be equivalently synthesized on the space level.
The process is a single beam pointing synthesis process, and the beam pointing synthesis with different delay gradients can be realized simultaneously by changing the splitting ratio of the tunable coupler in the multi-beam forming network.
The embodiment of the disclosure realizes the following beneficial effects by using the directional multi-beam radar receiving device based on the true delay network:
(1) By utilizing the structural advantages of the multi-beam network matrix, the radar echo signals pointed by a plurality of beams can be received simultaneously, the number of the beams and the number of the antennas can be arbitrarily expanded, and the synthesis receiving of narrow beams at any angle can be realized within a large radiation angle range, so that the gain of the received beams is greatly improved, and the performance of a receiver is improved.
(2) The multi-beam receiving method can simultaneously perform multi-beam receiving, is favorable for rapidly ranging and imaging targets, can relieve the limitation of maximum non-fuzzy distance in a wide-range scene, and has wide application value and potential in the application scene of the spaceborne high-resolution wide-range synthetic aperture radar.
(3) The device has compact structure, is beneficial to realizing the integration of the system on chip and is also beneficial to realizing the expansion of the large-scale integrated beam forming network.
The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The units or modules described in the embodiments of the present disclosure may be implemented by software, or may be implemented by hardware. The units or modules described may also be provided in a processor, the names of which in some cases do not constitute a limitation of the unit or module itself.
As another aspect, the present disclosure also provides a computer-readable storage medium, which may be a computer-readable storage medium included in the apparatus described in the above embodiment; or may be a computer-readable storage medium, alone, that is not assembled into a device. The computer-readable storage medium stores one or more programs for use by one or more processors in performing the methods described in the present disclosure.
The foregoing description is only of the preferred embodiments of the present disclosure and description of the principles of the technology being employed. It will be appreciated by those skilled in the art that the scope of the invention referred to in this disclosure is not limited to the specific combination of features described above, but encompasses other embodiments in which any combination of features described above or their equivalents is contemplated without departing from the inventive concepts described. Such as those described above, are mutually substituted with the technical features having similar functions disclosed in the present disclosure (but not limited thereto).
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| CN107086892A (en) * | 2017-03-29 | 2017-08-22 | 中国科学院半导体研究所 | A system for forming photonic beams of microwave photons |
| CN110703250A (en) * | 2019-11-05 | 2020-01-17 | 中国科学院电子学研究所 | Echo signal separation method and device of pitching space-time coding synthetic aperture radar |
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| CN113608228B (en) * | 2021-08-02 | 2023-05-26 | 中国科学院空天信息创新研究院 | Quick scanning device and method for two-dimensional multi-beam laser radar based on blast matrix |
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| CN110703250A (en) * | 2019-11-05 | 2020-01-17 | 中国科学院电子学研究所 | Echo signal separation method and device of pitching space-time coding synthetic aperture radar |
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