A multi-band radar signal generating device

Abstract

The present invention provides a multi-band radar signal generating device, which comprises: a continuous laser, an electro-optic intensity modulator, an optical fiber amplifier, and a photodetector connected in sequence, wherein the electro-optic intensity modulator is also connected to an intermediate frequency-radio frequency signal generator. The solution uses the electro-optic intensity modulator as a core component, only needs to adjust a DC bias voltage, is simple to operate, and has good system reliability.

Description

Technical Field

[0001] The invention belongs to the field of radar technology, and in particular relates to a multi-band radar signal generating device. Background Art

[0002] Radar systems are widely used in military and civilian applications, and higher accuracy is the goal pursued by radar systems. Modern radar systems usually use pulse compression technology to improve distance resolution. In order to achieve pulse compression, the most commonly used radar signal is a linear frequency modulation signal. Traditional linear frequency modulation signals can be generated by means such as voltage-controlled oscillators or surface acoustic wave dispersion delay lines. In addition, they can also be generated by electronic devices such as local oscillators and direct digital synthesizers. Generally speaking, the intermediate frequency radar signal is first generated by a direct digital synthesizer, and then the intermediate frequency signal is converted to a higher frequency by using a mixer and a local oscillator through multi-stage mixing. Although the traditional linear frequency modulation signal has good pulse compression performance, the sidelobe component of the compressed pulse is very high. The nonlinear frequency modulation signal can greatly reduce the sidelobe level after compression through special frequency design. Generally speaking, nonlinear frequency modulation signals can also be generated by direct digital synthesizers and local oscillators. The generation process is similar to that of linear frequency modulation signals, except that the intermediate frequency signal generated by the direct digital synthesizer is a specially designed nonlinear frequency modulation signal.

[0003] Compared with traditional radars, multi-band radars have higher accuracy and stronger anti-stealth capabilities. Traditional multi-band radar signals based on electrical domain technology require the use of multiple independent single-band signal generation devices. In addition to the multi-band radar signal generation technology based on the traditional electrical domain, some scholars have proposed a solution to generate multi-band radar signals through microwave photonics technology. For example, a dual-polarization Mach-Zehnder modulator is used, in which a radio frequency signal is modulated on one sub-Mach-Zehnder modulator, and a linear frequency modulation signal of an intermediate frequency is modulated on the other sub-Mach-Zehnder modulator. By changing the bias point of the modulator and the power of the driving signal, a multi-band linear frequency modulation signal can be generated. There is also a multi-band linear frequency modulation signal generation scheme based on a dual parallel Mach-Zehnder modulator, in which two intermediate frequency linear frequency modulation signals with different chirp rates generated by an arbitrary waveform generator are divided into two paths through a 90-degree mixer coupler, and then the two sub-Mach-Zehnder modulators of the dual parallel Mach-Zehnder modulator are driven respectively, and the three bias voltages of the dual parallel Mach-Zehnder modulator and the amplitude of the intermediate frequency signal are adjusted to obtain a multi-band linear frequency modulation signal. At present, some scholars have proposed a scheme to generate nonlinear frequency modulation signals based on microwave photonics. Nonlinear frequency modulation signals can be generated by controlling the driving current of semiconductor lasers. There are also schemes that use light injection into semiconductor lasers to control the intensity of the injected light to achieve the generation of nonlinear frequency modulation signals.

[0004] Radar signals generated by traditional electrical domain means usually face problems such as low carrier frequency, narrow bandwidth, and small time-bandwidth product, which fundamentally limits the improvement of modern radar system performance. Radar signal generation technology based on microwave photonics can solve the problems of low carrier frequency and narrow bandwidth in traditional electrical domain radar signal generation technology, and provide a good solution for the next generation of high-precision radar. There are currently a variety of single-band linear frequency modulation signal generation technologies based on microwave photonic technology. Although they can generate high-frequency and broadband linear frequency modulation signals and are more flexible in adjustability, they cannot meet the needs of multi-band radars. Multi-band radar signal generation based on electrical domain technology requires the use of multiple independent single-band signal generation devices, which not only makes the entire system very complicated, but also makes it difficult to ensure the coherence of multi-band signals. Microwave photon generation technology for multi-band linear frequency modulation signals has also appeared, but it requires the use of complex electro-optical modulators, and multiple DC bias points need to be controlled simultaneously to meet special working conditions. In addition, the modulation coefficient and other parameters of the modulator also have certain requirements, which makes it difficult to promote existing technologies in practical applications. In addition, the current nonlinear frequency modulation signal generated by microwave photonics is oriented to single-band radar systems, which makes the existing nonlinear frequency modulation signal generation technology based on microwave photonics unable to support multi-band radars. The existing nonlinear frequency modulation signal generation based on microwave photonics needs to be achieved through swept lasers or light injection semiconductor lasers. Due to the influence of the inherent spontaneous radiation noise of the laser, the quality of the generated radar signal is not very good. Summary of the invention

[0005] The purpose of the embodiments of this specification is to provide a multi-band radar signal generating device.

[0006] To solve the above technical problems, the embodiments of the present application are implemented in the following ways:

[0007] In a first aspect, the present application provides a multi-band radar signal generating device, the device comprising:

[0008] A continuous laser, an electro-optic intensity modulator, an optical fiber amplifier and a photoelectric detector are connected in sequence. The electro-optic intensity modulator is also connected to an intermediate frequency-radio frequency signal generator.

[0009] In one of the embodiments, the polarization direction of the optical signal emitted by the continuous laser is the same as the main axis direction of the electro-optical intensity modulator, so as to maximize the modulation efficiency of the electro-optical intensity modulator.

[0010] In one of the embodiments, the device further comprises: a polarization controller, the polarization controller being connected to the continuous laser and the electro-optical intensity modulator respectively;

[0011] The polarization controller is used to adjust the polarization direction of the optical signal emitted by the continuous laser so that the polarization direction of the optical signal is the same as the main axis direction of the electro-optical intensity modulator, so as to maximize the modulation efficiency of the electro-optical intensity modulator.

[0012] In one of the embodiments, the IF-RF signal generator includes: a broadband first arbitrary waveform generator, the first arbitrary waveform generator being connected to the electro-optical intensity modulator;

[0013] A broadband first arbitrary waveform generator generates an intermediate frequency signal and a radio frequency signal simultaneously;

[0014] The angular frequency of the RF signal is twice the carrier angular frequency of the IF signal.

[0015] In one of the embodiments, the IF-RF signal generator includes: a second arbitrary waveform generator, a microwave source, and an electrical coupler;

[0016] The second arbitrary waveform generator and the microwave source are both connected to the electric coupler; the electric coupler is connected to the electro-optical intensity modulator;

[0017] The second arbitrary waveform generator generates an intermediate frequency signal;

[0018] A microwave source generates a radio frequency signal;

[0019] The electric coupler couples the radio frequency signal and the intermediate frequency signal;

[0020] The angular frequency of the RF signal is twice the carrier angular frequency of the IF signal.

[0021] In one of the embodiments, the IF-RF signal generator further includes a microwave amplifier;

[0022] The microwave amplifier is connected to the microwave source and the electric coupler respectively.

[0023] In one embodiment, the electro-optical intensity modulator operates at a minimum operating point.

[0024] In one embodiment, the continuous laser is a C-band linearly polarized output laser.

[0025] In one of the embodiments, the electro-optical intensity modulator is a single-drive electro-optical intensity modulator.

[0026] In one embodiment, the optical fiber amplifier is an erbium-doped optical fiber amplifier.

[0027] It can be seen from the technical solution provided in the above embodiments of this specification that the solution: uses an electro-optic intensity modulator as a core component, only needs to adjust a DC bias voltage, is simple to operate, and has good system reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 A schematic diagram of the structure of the multi-band radar signal generating device provided in this application Figure 1 ;

[0030] Figure 2 A schematic diagram of the structure of the multi-band radar signal generating device provided in this application Figure 2 ;

[0031] Figure 3 A schematic diagram of the structure of the multi-band radar signal generating device provided in this application Figure 3 . DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this specification.

[0033] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present application description without departing from the scope or spirit of the present application. Other embodiments derived from the present application description will be apparent to those skilled in the art. The present application description and examples are merely exemplary.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] Unless otherwise specified, "parts" in this application are all calculated by mass.

[0037] In the related art, microwave photon generation technology for multi-band linear frequency modulation signals requires the use of complex electro-optic modulators and the simultaneous control of multiple DC bias points to meet special working conditions.

[0038] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0039] Reference Figure 1-3 , which shows a schematic diagram of the structure of a multi-band radar signal generating device applicable to the embodiment of the present application. It can be understood that the radar signal in the embodiment of the present application mainly refers to two commonly used radar signals, namely, linear frequency modulation signal and nonlinear frequency modulation signal. Among them, the linear frequency modulation signal is a signal whose frequency changes linearly with time, and its autocorrelation function has a higher side lobe; the nonlinear frequency modulation signal is a signal whose frequency changes with time to meet a certain frequency modulation function, and its autocorrelation function has a lower side lobe.

[0040] like Figure 1 As shown, the multi-band radar signal generating device may include: a continuous laser 1, an electro-optical intensity modulator 3, an optical fiber amplifier 4, and a photodetector 5 connected in sequence, and the electro-optical intensity modulator 3 is also connected to an intermediate frequency-radio frequency signal generator 6.

[0041] Specifically, the continuous laser 1 is used to provide an optical signal. Exemplarily, the continuous laser 1 can be a commercial C-band linearly polarized output laser.

[0042] The electro-optic intensity modulator 3 is used to modulate the optical signal output by the continuous laser 1. For example, the electro-optic intensity modulator may be a commercial single-drive lithium niobate Mach-Zehnder electro-optic modulator.

[0043] It can be understood that in order to maximize the modulation efficiency of the electro-optical intensity modulator 3 , the polarization direction of the optical signal entering the electro-optical intensity modulator 3 can be set to be the same as the main axis direction of the electro-optical intensity modulator 3 .

[0044] The polarization direction of the optical signal output by the continuous laser 1 can also be adjusted by the polarization controller 2 .

[0045] Continue to refer to Figure 1 , Optionally, a multi-band radar signal generating device may further include: a polarization controller 2, the polarization controller 2 is respectively connected to the continuous laser 1 and the electro-optical intensity modulator 3;

[0046] The polarization controller 2 is used to adjust the polarization direction of the optical signal emitted by the continuous laser 1 so that the polarization direction of the optical signal is the same as the main axis direction of the electro-optical intensity modulator 3, so as to maximize the modulation efficiency of the electro-optical intensity modulator 3.

[0047] The polarization controller 2 may be a three-ring polarization controller.

[0048] It is understandable that the bias voltage input port of the electro-optic intensity modulator can be powered by a commercial DC power supply to adjust the operating point. Optionally, the operating state of the electro-optic intensity modulator 3 can be adjusted to a minimum operating point.

[0049] The optical fiber amplifier 4 is used to amplify the optical signal output by the electro-optical intensity modulator 3, so as to increase the power of the generated signal. For example, the optical fiber amplifier 4 can be a commercial erbium-doped optical fiber amplifier.

[0050] The photodetector 5 is used to convert the optical signal amplified by the optical fiber amplifier 4 into an electrical signal. The photodetector 5 can be a commercial device, and the detection bandwidth of the photodetector needs to be greater than the bandwidth of the generated multi-band signal.

[0051] The IF-RF signal generator 6 is used to generate an IF signal and a RF signal, and drive the electro-optical intensity modulator 3 .

[0052] In one embodiment, Figure 2 As shown, the intermediate frequency-radio frequency signal generator 6 includes: a broadband first arbitrary waveform generator 6-1, and the first arbitrary waveform generator 6-1 is connected to the electro-optical intensity modulator 3;

[0053] A broadband first arbitrary waveform generator 6-1 generates an intermediate frequency signal and a radio frequency signal simultaneously;

[0054] The angular frequency of the RF signal is twice the carrier angular frequency of the IF signal.

[0055] In one embodiment, Figure 3 As shown, the intermediate frequency-radio frequency signal generator 6 includes: a second arbitrary waveform generator 6-2, a microwave source 6-3, and an electric coupler 6-4;

[0056] The second arbitrary waveform generator 6-2 and the microwave source 6-3 are both connected to the electric coupler 6-4; the electric coupler 6-4 is connected to the electro-optical intensity modulator 3;

[0057] The second arbitrary waveform generator 6-2 generates an intermediate frequency signal;

[0058] The microwave source 6-3 generates a radio frequency signal;

[0059] The electric coupler 6-4 couples the radio frequency signal and the intermediate frequency signal;

[0060] The angular frequency of the RF signal is twice the carrier angular frequency of the IF signal.

[0061] Continue to refer to Figure 3 , Optionally, the IF-RF signal generator 6 also includes a microwave amplifier 6-5;

[0062] The microwave amplifier 6-5 is connected to the microwave source 6-3 and the electrical coupler 6-4 respectively.

[0063] Specifically, the radio frequency signal generated by the microwave source 6-3 and the intermediate frequency signal generated by the second arbitrary waveform generator 6-2 are coupled by the electric coupler 6-4 to generate a signal that drives the electro-optical intensity modulator 3. The microwave amplifier 6-5 is used to amplify the radio frequency signal generated by the microwave source 6-3.

[0064] The microwave amplifier 6-5 and the electric coupler 6-4 can both be commercial devices, wherein the bandwidth of the microwave amplifier 6-5 needs to cover the frequency range of the signal generated by the microwave source 6-3, and the bandwidth of the electric coupler 6-4 needs to cover the frequency range of the signal generated by the microwave source 6-3 and the second arbitrary waveform generator 6-2.

[0065] The first arbitrary waveform generator 6-1, the second arbitrary waveform generator 6-2, and the microwave source 6-3 can all be commercial devices.

[0066] The radio frequency signal generated by the microwave source 6-3 can be expressed as V1 cos(ω LO t), where V1 is the amplitude of the RF signal, ω LO is the angular frequency of the radio frequency signal, and the intermediate frequency signal generated by the second arbitrary waveform generator 6-2 can be expressed as Among them, V2 is the amplitude of the intermediate frequency signal, ω IF is the carrier angular frequency of the intermediate frequency signal, is the phase. The angular frequency of the RF signal is twice the carrier angular frequency of the intermediate frequency signal, that is: ω LO =2ω IF .

[0067] The electric field intensity E(t) of the optical signal output by the electro-optical intensity modulator 3 can be expressed as:

[0068]

[0069] Where, m1=πV1 / V π is the modulation coefficient corresponding to the RF signal, m2=πV2 / V π is the modulation coefficient corresponding to the intermediate frequency signal, Φ DC =πV DC / V π is the phase shift caused by DC bias, V π is the half-wave voltage of the electro-optical intensity modulator 3, V DC is the applied DC voltage, E0 is the amplitude of the electric field intensity of the optical signal emitted by the continuous laser 1; ω o is the angular frequency of the optical signal emitted by the continuous laser 1.

[0070] The optical signal output by the electro-optical intensity modulator 3 is amplified by the optical fiber amplifier 4 and then enters the photodetector 5. The photodetector 5 is used to convert the modulated optical signal into an electrical signal. The signal after the photoelectric conversion can be expanded by the Jacobi formula. By controlling the transmission power of the intermediate frequency generated by the second arbitrary waveform generator 6-2, the high-order sidebands of the modulated signal are small enough to be ignored, so that only the first-order sidebands are considered. The microwave source 6-3 is controlled to generate RF signal power, and the first 5 order sidebands are considered after Jacobi expansion. Without considering the DC term, the signal output by the photodetector 5 can be expressed as:

[0071]

[0072] Among them, J n (.) is the nth-order Bessel function of the first kind.

[0073] It can be seen from the above formula that the signal output by the photoelectric detector 5 includes a single-frequency signal in addition to the radar signal. The single-frequency signal can be filtered out by a filter, so the single-frequency signal is no longer considered in the subsequent analysis.

[0074] By adjusting the power of the RF signal, the modulation coefficient m1 corresponding to the RF signal will also change accordingly. When m1 is small (for example, m1<1), J3(2m1) and J5(2m1) are both relatively small and can be ignored. At this time, the signal output by the photodetector 5 is a two-band signal, which can be expressed as:

[0075]

[0076] When m1 = 1.53, the values ​​of J1(2m1) and J3(2m1) are close, and J5(2m1) is relatively small and can be ignored. Therefore, the signal output by the photodetector 5 is a four-band radar signal, which can be expressed as:

[0077]

[0078] When m1 = 2.65, the values ​​of J1(2m1), J3(2m1) and J5(2m1) are close. Therefore, the signal output by the photodetector 5 is a six-band radar signal, which can be expressed as:

[0079]

[0080] By changing the intermediate frequency signal generated by the second arbitrary waveform generator 6-2, a multi-band linear frequency modulation and nonlinear frequency modulation signal with adjustable frequency bands can be generated. The phase term in When , the generated signal is a multi-band linear frequency modulation signal. When is a specially designed function, a multi-band nonlinear frequency modulation signal can be generated. There are many design schemes for nonlinear frequency modulation signals, one of which is a tangent-based frequency modulation-time function that can be expressed as:

[0081]

[0082] β=tan -1 α,0≤α≤∞

[0083] in, f IF =ω IF / (2π), B is the frequency sweep bandwidth, T is the pulse width, and α is the time sidelobe level control factor.

[0084] When the intermediate frequency-radio frequency signal generator 6 includes a broadband first arbitrary waveform generator 6-1, the working principle is consistent with that when the intermediate frequency-radio frequency signal generator 6 includes a combination device of a second arbitrary waveform generator 6-2, a microwave source 6-3, and an electric coupler 6-4, and will not be repeated here.

[0085] In the embodiment of the present application, a single-drive electro-optic intensity modulator is used as the core device, and only a DC bias voltage needs to be adjusted, which is simple to operate and has good system reliability.

[0086] In the embodiment of the present application, the angular frequency of the radio frequency signal output by the microwave source is twice the carrier angular frequency of the intermediate frequency signal output by the second arbitrary waveform generator, and the modulation coefficient corresponding to the intermediate frequency signal output by the second arbitrary waveform generator should be small, and only the first-order sideband is considered in the signal output by the photodetector. When the modulation coefficient corresponding to the radio frequency signal generated by the microwave source meets different conditions, a flat 2-band, 4-band, 6-band linear frequency modulation signal or a nonlinear frequency modulation signal can be generated, that is, the number of frequency bands of the multi-band radar signal can be controlled by changing the output power of the microwave source, and 2-band, 4-band and 6-band radar signals can be generated, which has good flexibility.

[0087] In an embodiment of the present application, different types of multi-band radar signals can be generated by switching the type of intermediate frequency signal generated by the second arbitrary waveform generator. When the signal output by the second arbitrary waveform generator is a single-band intermediate frequency linear frequency modulation signal, the corresponding multi-band signal generated is a multi-band linear frequency modulation signal. When the signal output by the second arbitrary waveform generator is a single-band intermediate frequency nonlinear frequency modulation signal, the corresponding multi-band signal generated is a multi-band nonlinear frequency modulation signal. That is, by changing the type of the intermediate frequency signal of the second arbitrary waveform generator, the switching between multi-band linear frequency modulation and nonlinear frequency modulation signals can be achieved, which can meet the needs of multi-function radars in different scenarios.

[0088] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0089] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

Claims

1. A multi-band radar signal generating device, characterized in that: The device comprises: A continuous laser (1), an electro-optical intensity modulator (3), an optical fiber amplifier (4), and a photodetector (5) connected in sequence, wherein the electro-optical intensity modulator (3) is also connected to an intermediate frequency-radio frequency signal generator (6); The intermediate frequency-radio frequency signal generator (6) comprises: a second arbitrary waveform generator (6-2), a microwave source (6-3), and an electric coupler (6-4); The second arbitrary waveform generator (6-2) and the microwave source (6-3) are both connected to the electric coupler (6-4); the electric coupler (6-4) is connected to the electro-optical intensity modulator (3); The second arbitrary waveform generator (6-2) generates an intermediate frequency signal, and the switching between multi-band linear frequency modulation and nonlinear frequency modulation signals can be realized by changing the type of the intermediate frequency signal of the second arbitrary waveform generator (6-2); The microwave source (6-3) generates a radio frequency signal, and the number of frequency bands of the multi-band radar signal is controlled by changing the output power of the microwave source (6-3); The electric coupler (6-4) couples the radio frequency signal and the intermediate frequency signal; The angular frequency of the radio frequency signal is twice the carrier angular frequency of the intermediate frequency signal.

2. The device according to claim 1, characterized in that The polarization direction of the optical signal emitted by the continuous laser (1) is the same as the main axis direction of the electro-optical intensity modulator (3), so that the modulation efficiency of the electro-optical intensity modulator (3) is maximized.

3. The device according to claim 1, characterized in that The device further comprises: a polarization controller (2), wherein the polarization controller (2) is connected to the continuous laser (1) and the electro-optical intensity modulator (3) respectively; The polarization controller (2) is used to adjust the polarization direction of the optical signal emitted by the continuous laser (1) so that the polarization direction of the optical signal is the same as the main axis direction of the electro-optical intensity modulator (3), so as to maximize the modulation efficiency of the electro-optical intensity modulator (3).

4. The device according to any one of claims 1 to 3, characterized in that: The intermediate frequency-radio frequency signal generator (6) comprises: a broadband first arbitrary waveform generator (6-1), wherein the first arbitrary waveform generator (6-1) is connected to the electro-optical intensity modulator (3); The broadband first arbitrary waveform generator (6-1) generates an intermediate frequency signal and a radio frequency signal simultaneously; The angular frequency of the radio frequency signal is twice the carrier angular frequency of the intermediate frequency signal.

5. The device according to any one of claims 1 to 3, characterized in that: The intermediate frequency-radio frequency signal generator (6) further comprises a microwave amplifier (6-5); The microwave amplifier (6-5) is connected to the microwave source (6-3) and the electric coupler (6-4) respectively.

6. The device according to any one of claims 1 to 3, characterized in that: The electro-optic intensity modulator (3) operates at a minimum operating point.

7. The device according to any one of claims 1 to 3, characterized in that: The continuous laser (1) adopts a C-band linearly polarized output laser.

8. The device according to any one of claims 1 to 3, characterized in that: The optical fiber amplifier (4) is an erbium-doped optical fiber amplifier.

Images