Microwave photon ultra-wideband tunable linear frequency modulation signal generator

Abstract

The invention specifically relates to a microwave photon ultra-wideband tunable linear frequency modulation signal generator, and belongs to the technical field of microwave photonics. The device is composed of a first laser, a polarization controller, a double-parallel Mach-Zehnder modulator, an optical filter, an optical coupler, a photoelectric detector, a radio frequency amplifier, a second laser, a baseband signal source, a direct-current voltage source and a 90-degree coupler. By adjusting the bias voltage of the dual-parallel Mach-Zehnder modulator, double frequency multiplication and triple frequency multiplication of a linear frequency modulation signal are realized, so that a single microwave photon frequency multiplication system can simultaneously realize double frequency multiplication and triple frequency multiplication functions. Frequency multiplication and frequency conversion of baseband signals are completed in one-time electro-optical-photoelectric conversion through a method of reserving a single high-order sideband and beat frequency of a tunable laser, and multiple times of photoelectric conversion are not needed. And meanwhile, the use of a tunable optical filter is avoided, and the complexity and the cost of the system are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of microwave photonics, and in particular to a broadband tunable linear frequency modulation signal generator based on microwave photon frequency doubling and microwave photon frequency conversion. Background Art

[0002] Linear frequency modulation signal is an important radar waveform in radar system, which is of great significance in the detection of distance and speed. In microwave imaging radar, the bandwidth of linear frequency modulation signal directly affects the imaging resolution. In addition, due to the diversity of radar types and complex working environment, the tunability of the working frequency band is becoming more and more critical to enable radar to adapt to more usage scenarios. Therefore, as a radar waveform generator, ultra-wideband tunable linear frequency modulation signal generator is of great significance in radar systems, especially imaging radar.

[0003] At present, linear frequency modulation signals are usually generated by direct digital synthesis (DDS) or high-speed digital-to-analog converters, and then frequency tuning is achieved through a mixing network. For linear frequency modulation signals with a bandwidth exceeding 4GHz, it is usually necessary to generate them through multi-channel splicing or high-order frequency multiplication. These methods will bring problems such as phase discontinuity and low flatness. In addition, the frequency of the linear frequency modulation signal is frequency tuned through mixing. A complex mixing network and local oscillator source are required for large-range frequency tuning, and the system is relatively complex. At present, broadband linear frequency modulation signals can be generated through microwave photon frequency multiplication technology, but most of the methods use the positive and negative sideband beat frequency method. The frequency multiplication signals generated by this method are mostly even-order frequency multiplication, and it is difficult to achieve odd-order frequency multiplication. In addition, the frequency multiplication method using positive and negative sideband beat frequency requires secondary electro-optical conversion to achieve frequency conversion of broadband linear frequency modulation signals, and the system is relatively cumbersome.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] The present invention provides a microwave photon ultra-wideband tunable linear frequency modulation signal generator, which can realize that a single microwave photon frequency doubling system can simultaneously realize the double frequency and triple frequency functions, thereby effectively overcoming the defects existing in the prior art to a certain extent.

[0006] Other features and advantages of the present invention will become apparent from the following detailed description, or may be learned in part by practice of the present invention.

[0007] According to a first aspect of the present invention, there is provided a microwave photon ultra-wideband tunable linear frequency modulation signal generator, comprising: a first laser, a polarization controller, a dual parallel Mach-Zehnder modulator, an optical filter, an optical coupler, a photodetector, a second laser, a baseband signal source, a 90° coupler and a bias adjustment module;

[0008] The first laser outputs an optical signal to the bias voltage adjustment module as a DC voltage source;

[0009] The DC voltage source is connected to the first branch Mach-Zehnder modulator, the second branch Mach-Zehnder modulator and the optical phase shifter respectively; by outputting three different DC bias voltages to the first branch Mach-Zehnder modulator, the second branch Mach-Zehnder modulator and the optical phase shifter, the linear frequency modulation signal is realized in a double frequency mode or a triple frequency mode.

[0010] An optical polarization controller, which polarizes the optical signal and then inputs it into a dual parallel Mach-Zehnder modulator;

[0011] The baseband signal generated by the baseband signal source is divided into two signals with a 90° phase difference by a 90° coupler and input into a dual parallel Mach-Zehnder modulator as a modulation signal;

[0012] The bias voltage adjustment module is connected to the dual parallel Mach-Zehnder modulator and is used to adjust the bias voltage of the dual parallel Mach-Zehnder modulator to realize the doubling and tripling of the linear frequency modulation signal;

[0013] The output of the dual parallel Mach-Zehnder modulator is connected to an optical filter, and the output of the optical filter is connected to an optical coupler;

[0014] The second laser outputs an optical signal to an optical coupler, and the optical coupler is connected to a photodetector.

[0015] In some exemplary embodiments, a radio frequency amplifier is further included, wherein the radio frequency amplifier is connected to the output end of the photodetector and is used to amplify the linear frequency modulation signal output by the photodetector.

[0016] In some exemplary embodiments, the dual parallel Mach-Zehnder modulator includes a first-branch Mach-Zehnder modulator, a second-branch Mach-Zehnder modulator, and an optical phase shifter connected to the second-branch Mach-Zehnder modulator.

[0017] In some exemplary embodiments, the bias voltage regulation module is a DC voltage source;

[0018] The DC voltage source is connected to the first branch Mach-Zehnder modulator, the second branch Mach-Zehnder modulator and the optical phase shifter respectively; by outputting three different DC bias voltages to the first branch Mach-Zehnder modulator, the second branch Mach-Zehnder modulator and the optical phase shifter, the linear frequency modulation signal is realized in a double frequency mode or a triple frequency mode.

[0019] In some exemplary embodiments, the method of adjusting the linear frequency modulation signal to a double frequency mode by outputting three different DC bias voltages to a first branch Mach-Zehnder modulator, a second branch Mach-Zehnder modulator, and an optical phase shifter includes:

[0020] When the DC bias voltages of the first branch Mach-Zehnder modulator and the second branch Mach-Zehnder modulator are both 0V, the DC bias voltage of the optical phase shifter is half of the half-wave voltage of the main modulator of the dual parallel Mach-Zehnder modulator, and the linear frequency modulation signal is in double frequency mode.

[0021] In some exemplary embodiments, the step of adjusting the linear frequency modulation signal to a triple frequency mode by outputting three different DC bias voltages to a first branch Mach-Zehnder modulator, a second branch Mach-Zehnder modulator, and an optical phase shifter includes:

[0022] When the DC bias voltage of the first branch Mach-Zehnder modulator is the half-wave voltage of the first Mach-Zehnder modulator, the DC bias voltage of the second branch Mach-Zehnder modulator is the half-wave voltage of the second Mach-Zehnder modulator, and the DC bias voltage of the optical phase shifter is half of the half-wave voltage of the main modulator of the dual parallel Mach-Zehnder modulator, the linear frequency modulation signal is in a triple frequency mode.

[0023] In some exemplary embodiments, the baseband signal generated by the baseband signal source is divided by a 90° coupler into two signals with a 90° phase difference as modulation signals and input into a dual parallel Mach-Zehnder modulator, specifically:

[0024] The baseband signal generated by the baseband signal source is divided into a 0° phase-shifted baseband signal and a 90° phase-shifted baseband signal by a 90° coupler; wherein the 90° phase-shifted baseband signal is injected into the first Mach-Zehnder modulator as a modulation signal, and the 0° phase-shifted baseband signal is injected into the second Mach-Zehnder modulator as a modulation signal. The output signal of the second Mach-Zehnder modulator will be optically phase-shifted on the main modulation arm optical phase shifter of the dual parallel Mach-Zehnder modulator. The optical signal after phase shifting and the optical signal of the first Mach-Zehnder modulator are combined into one light in the waveguide of the dual parallel Mach-Zehnder modulator and enter the optical filter.

[0025] In some exemplary embodiments, the second laser is a tunable laser, and the frequency of the output signal is changed by adjusting the output frequency of the second laser.

[0026] In some exemplary embodiments, the optical filter is a bandpass filter, and its bandwidth is greater than or equal to the working bandwidth of the baseband signal source.

[0027] The microwave photon ultra-wideband tunable linear frequency modulation signal generator provided by the embodiment of the present invention realizes the doubling and tripling of the linear frequency modulation signal by adjusting the bias voltage of the dual parallel Mach-Zehnder modulator, so that a single microwave photon frequency doubling system can realize the doubling and tripling functions at the same time; by retaining a single high-order sideband and a tunable laser beat frequency, the frequency doubling and frequency conversion of the baseband signal are completed in one electro-optical-photoelectric conversion, without the need for multiple photoelectric conversions; the extraction of relatively pure second-order sidebands and third-order sidebands is realized through a broadband optical filter with a fixed passband, which can meet the filtering requirements of output signals with different frequency doubling coefficients and output frequencies, and there is no need to use a tunable narrowband filter matching the output frequency for targeted filtering, thereby avoiding the use of a tunable optical filter and reducing the complexity and cost of the system.

[0028] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings herein are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present invention, and together with the specification are used to explain the principles of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0030] Figure 1 This is a schematic diagram of the structure of a microwave photon ultra-wideband tunable linear frequency modulation signal generator;

[0031] Figure 2 This is a schematic diagram of the principle of a linear frequency modulation signal generator;

[0032] Figure 3 It is the spectrum diagram of double frequency linear frequency modulation signal;

[0033] Figure 4 It is the spectrum diagram of triple frequency linear frequency modulation signal;

[0034] Figure 5 This is the spectrum diagram of the triple frequency linear frequency modulation signal after frequency conversion. DETAILED DESCRIPTION

[0035] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0036] In addition, the accompanying drawings are only schematic illustrations of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0037] The structure of the ultra-wideband tunable linear frequency modulation signal generator based on microwave photon frequency doubling and microwave photon frequency conversion in this exemplary implementation will be described in more detail below in conjunction with the accompanying drawings and embodiments.

[0038] refer to Figure 1 The structure of the microwave photon ultra-wideband tunable linear frequency modulation signal generator shown in the figure includes: a first laser, a polarization controller, a dual parallel Mach-Zehnder modulator, an optical filter, an optical coupler, a photodetector, a radio frequency amplifier, a second laser, a baseband signal source, a DC voltage source and a 90° coupler. The dual parallel Mach-Zehnder modulator is an integrated device, which contains a first branch Mach-Zehnder modulator, a second branch Mach-Zehnder modulator and an optical phase shifter, as well as an optical waveguide for beam splitting, beam combining and optical transmission.

[0039] The connection relationship of the above components is as follows: the output of the first laser is connected to the polarization controller, the output of the polarization controller is connected to the first branch Mach-Zehnder modulator and the second branch Mach-Zehnder modulator, the output of the second branch Mach-Zehnder modulator is connected to the optical phase shifter, the output of the first branch Mach-Zehnder modulator and the output of the optical phase shifter are connected to the optical filter, the output of the optical filter and the second laser are connected to the optical coupler, and the optical coupler is connected to the photodetector and the radio frequency amplifier in sequence; the output of the baseband signal source is connected to the 90° coupler, and the output of the 90° coupler is connected to the first branch Mach-Zehnder modulator and the second branch Mach-Zehnder modulator; the output of the DC voltage source is connected to the first branch Mach-Zehnder modulator, the second branch Mach-Zehnder modulator and the optical phase shifter.

[0040] The first laser output frequency is f c1The optical signal is used as the optical carrier signal of the link, and the optical polarization controller is used to adjust the polarization state of the optical carrier signal so that the laser polarization state is aligned with the main optical axis of the modulator to achieve the best modulation effect.

[0041] The optical carrier after polarization adjustment enters the dual parallel Mach-Zehnder modulator. The optical waveguide in the dual parallel Mach-Zehnder modulator distributes the optical carrier to two branches, and the optical carrier powers of the two branches are equal. The optical signal of one branch enters the first Mach-Zehnder modulator, which is recorded as branch 101; the optical signal of the other branch enters the second Mach-Zehnder modulator, which is recorded as branch 102. The Mach-Zehnder modulators of branches 101 and 102 are modulated by the baseband linear frequency modulation signal generated by the baseband signal generator.

[0042] The baseband signal generated by the baseband signal source is divided into two signals with a 90° phase difference by a 90° coupler, the 0° branch is recorded as branch 201, and the 90° branch is recorded as branch 202. The 90° phase-shifted baseband signal of branch 202 is injected into the first Mach-Zehnder modulator of branch 101 as a modulation signal, and the 0° phase-shifted baseband signal of branch 201 is injected into the second Mach-Zehnder modulator of branch 102 as a modulation signal. The output signal of the second Mach-Zehnder modulator will be optically phase-shifted on the main modulation arm optical phase shifter of the dual parallel Mach-Zehnder modulator. After phase shifting, the optical signal of branch 102 and the optical signal of branch 101 are combined into one light in the waveguide of the dual parallel Mach-Zehnder modulator and enter the optical filter.

[0043] The DC voltage source provides three bias voltages for the dual parallel Mach-Zehnder modulators, which are injected into the first Mach-Zehnder modulator, the second Mach-Zehnder modulator and the main modulation arm optical phase shifter respectively. The selection of DC bias voltage varies depending on the required frequency multiplication factor.

[0044] When the system works in the double frequency mode, the DC bias voltages provided by branches 301 and 302 are both 0V. The DC bias voltage provided by branch 303 is half of the half-wave voltage of the main modulator of the dual parallel Mach-Zehnder modulator. The optical carrier is recorded as the frequency origin, f m is the input modulation signal frequency, and the output spectrum of the dual parallel Mach-Zehnder modulator is as follows: Figure 2 (1) As shown in the figure, the odd-order sidebands in the output signal are suppressed, while the even-order sidebands and the optical carrier are retained. Since the power of the high-order sidebands is too low, it can be considered that only the optical carrier and ±2-order sidebands are retained.

[0045] When the system works in the triple frequency mode, the DC bias voltage provided by branch 301 is equal to the half-wave voltage of the first Mach-Zehnder modulator of branch 101, and the DC bias voltage provided by branch 302 is equal to the half-wave voltage of the second Mach-Zehnder modulator of branch 102. The DC bias voltage provided by branch 303 is half of the half-wave voltage of the main modulator of the dual parallel Mach-Zehnder modulator. The optical carrier is recorded as the frequency origin, f m is the input modulation signal frequency, and the output spectrum of the dual parallel Mach-Zehnder modulator is as follows: Figure 2 (2) As shown in Figure 2, the even-order sidebands in the output signal are suppressed, while the +1-order sideband and -3-order sideband are retained.

[0046] The optical filter is used to filter out the stray sidebands in the modulator. The optical filter is a bandpass filter, and its bandwidth is greater than or equal to the working bandwidth of the signal source. The optical filter is used to filter out the optical carrier and all negative-order sidebands, and retain all positive-order sidebands. Since the optical sidebands required for the system to work are located on the same side of the optical carrier in different frequency doubling modes, only a broadband optical filter with a fixed passband is needed in the system to complete the filtering, and there is no need to reconfigure the passband of the optical filter when the output frequency is tuned or the frequency doubling factor is changed. The functions of the optical filter in the double frequency mode and triple frequency mode are as follows: Figure 2 (3) Figure 2 (4) The output signal of the optical filter is injected into the optical coupler through branch 401.

[0047] The second laser is a tunable laser, and its output optical signal frequency is denoted as f c2 , injected into the optical coupler through branch 402, combined with the optical signal of branch 401, to complete the frequency conversion of the RF output signal. Figure 2 (5) Figure 2 (6) shows the schematic diagram of the output spectrum in double frequency and triple frequency modes. After the beat frequency of the photodetector, ignoring the suppressed sideband power, the frequency of the output RF signal can be expressed as:

[0048]

[0049] By tuning the output frequency of the second laser, f c2 The frequency of the output RF signal can be changed. c1 <f c2 When f c1 >f c2When the input baseband signal is a linear frequency modulation signal, the output signal is also a corresponding frequency-doubled linear frequency modulation signal. According to the principle of frequency doubling, when the system works in the double frequency mode, the bandwidth of the output signal is twice that of the input signal; when the system works in the triple frequency mode, the bandwidth of the output signal is three times that of the input signal. The frequency of the output signal can be tuned to achieve the output frequency f of the second laser. c2 Wideband tuning is achieved, thereby completing the generation of ultra-wideband tunable linear frequency modulation signals. The RF amplifier is used to amplify the output signal.

[0050] Exemplarily, the first laser is Santec's TSL-510 tunable laser, and the output light frequency is fixed at 193.4145THz. The second laser is Santec's TSL-550 tunable laser, and the laser frequency is 193.4145THz when the system only multiplies the baseband signal; the dual parallel Mach-Zehnder modulator is iXblue's MXIQER-LN-30, with a bandwidth of 40GHz and a half-wave voltage of 6.5V; the 90° bridge is Suzhou Taylor Microwave Technology Co., Ltd.'s TBG-10180-3S-90 bridge, with a frequency range of 1GHz-18 GHz. The photodetector is Beijing Kangguan's KG-PD-50G-A-FC, with a bandwidth of 50GHz and a conversion rate of 0.55A / W; the RF amplifier is the AV80212 amplifier module of Dianco Instrument, with a frequency range of DC-26.5GHz and a gain greater than 20dB. The baseband linear frequency modulation signal is an arbitrary waveform generator M8196A from Keysight with a bandwidth of 25GHz. The optical filter is an XTM-50 optical filter from EXFO with a bandwidth tuning range of 50pm-950pm and an out-of-band rejection ratio of 45dB. The DC regulated power supply voltage can be tuned from 0 to 30V. The optical coupler coupling ratio is 50:50. The output signal test equipment is the MSOV254A oscilloscope and 9010A spectrum analyzer from Keysight.

[0051] according to Figure 1 Connect the corresponding test equipment, set the wavelength of the first laser and the second laser to 1550nm, that is, the frequency f c =193.4145 THz, the output power of the first laser is 10 mW, and the output power of the second laser is 0 mW; the passband of the optical filter is set to 193.4155 THz~193.5155 THz.

[0052] In the double frequency operation mode, the DC bias voltage of the first branch Mach-Zehnder modulator and the second branch Mach-Zehnder modulator is 0V, and the DC bias voltage of the optical phase shifter on the main modulator is 6.5V. The baseband linear frequency modulation signal frequency generated by the arbitrary waveform generator is set to 5GHz-7GHz, the power injected into the 90° coupler is 16dBm, and the period is 4μs. The generated signal spectrum is as follows Figure 3 The spectrum coverage of the output signal is 10–14 GHz, achieving a double frequency function and double spread spectrum for the baseband signal.

[0053] In the triple frequency working mode, the DC bias voltage of the first branch Mach-Zehnder modulator and the second branch Mach-Zehnder modulator is 6.5V, and the DC bias voltage of the optical phase shifter on the main modulator is 6.5V. In order to verify that the system can convert the frequency of the signal of any frequency within the bandwidth of the 90° coupler, the frequency of the baseband linear frequency modulation signal generated by the arbitrary waveform generator is set to 2GHz-6GHz, the power injected into the 90° coupler is 16dBm, and the period is 4μs. The generated signal spectrum is as follows Figure 4 As shown, the spectrum coverage of the output signal is 6–18 GHz, achieving a frequency tripling function and a three-fold spread spectrum for the baseband signal.

[0054] Adjusting the frequency of the second laser can achieve frequency conversion of the output signal. Taking the above frequency conversion as an example, the setting and generation of DC bias and baseband signal Figure 4 The settings of the results are the same. Keep the frequency of the first laser unchanged and set the frequency of the second laser to 193.4085THz. The signal obtained is as follows Figure 5 As shown, the frequency of the output signal changes to 12-24 GHz. The signal is up-converted to 6 GHz, and the frequency shift is equal to the frequency difference between the first laser and the second laser, which is consistent with the theoretical value.

[0055] Other embodiments of the invention will readily occur to those skilled in the art after considering the specification and practicing the invention herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0056] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A microwave photon ultra-wideband tunable linear frequency modulation signal generator, characterized in that: include: A first laser, a polarization controller, a dual parallel Mach-Zehnder modulator, an optical filter, an optical coupler, a photodetector, a second laser, a baseband signal source, a 90° coupler, and a bias adjustment module; The first laser outputs an optical signal to an optical polarization controller, and the optical polarization controller polarizes the optical signal and then inputs it into a dual parallel Mach-Zehnder modulator; The baseband signal generated by the baseband signal source is divided into two signals with a 90° phase difference by a 90° coupler and input into a dual parallel Mach-Zehnder modulator as a modulation signal; The bias voltage adjustment module is connected to the dual parallel Mach-Zehnder modulator and is used to adjust the bias voltage of the dual parallel Mach-Zehnder modulator to realize the doubling and tripling of the linear frequency modulation signal; The output of the dual parallel Mach-Zehnder modulator is connected to an optical filter, and the output of the optical filter is connected to an optical coupler; The second laser outputs an optical signal to an optical coupler, and the optical coupler is connected to a photodetector.

2. The microwave photon ultra-wideband tunable linear frequency modulation signal generator according to claim 1, characterized in that: It also includes a radio frequency amplifier, which is connected to the output end of the photodetector and is used to amplify the linear frequency modulation signal output by the photodetector.

3. The microwave photon ultra-wideband tunable linear frequency modulation signal generator according to claim 1 or 2, characterized in that: The dual parallel Mach-Zehnder modulator comprises a first branch Mach-Zehnder modulator, a second branch Mach-Zehnder modulator and an optical phase shifter connected to the second branch Mach-Zehnder modulator.

4. The microwave photon ultra-wideband tunable linear frequency modulation signal generator according to claim 3, characterized in that: The bias voltage regulation module is a DC voltage source; The DC voltage source is connected to the first branch Mach-Zehnder modulator, the second branch Mach-Zehnder modulator and the optical phase shifter respectively; by outputting three different DC bias voltages to the first branch Mach-Zehnder modulator, the second branch Mach-Zehnder modulator and the optical phase shifter, the linear frequency modulation signal is realized in a double frequency mode or a triple frequency mode.

5. The microwave photon ultra-wideband tunable linear frequency modulation signal generator according to claim 4, characterized in that: The method of adjusting the linear frequency modulation signal to a double frequency mode by outputting three different DC bias voltages to a first branch Mach-Zehnder modulator, a second branch Mach-Zehnder modulator and an optical phase shifter includes: When the DC bias voltages of the first branch Mach-Zehnder modulator and the second branch Mach-Zehnder modulator are both 0V, the DC bias voltage of the optical phase shifter is half of the half-wave voltage of the main modulator of the dual parallel Mach-Zehnder modulator, and the linear frequency modulation signal is in double frequency mode.

6. The microwave photon ultra-wideband tunable linear frequency modulation signal generator according to claim 4, characterized in that: The method of adjusting the linear frequency modulation signal to a triple frequency mode by outputting three different DC bias voltages to the first branch Mach-Zehnder modulator, the second branch Mach-Zehnder modulator and the optical phase shifter includes: When the DC bias voltage of the first branch Mach-Zehnder modulator is the half-wave voltage of the first Mach-Zehnder modulator, the DC bias voltage of the second branch Mach-Zehnder modulator is the half-wave voltage of the second Mach-Zehnder modulator, and the DC bias voltage of the optical phase shifter is half of the half-wave voltage of the main modulator of the dual parallel Mach-Zehnder modulator, the linear frequency modulation signal is in a triple frequency mode.

7. The microwave photon ultra-wideband tunable linear frequency modulation signal generator according to claim 3, characterized in that: The baseband signal generated by the baseband signal source is divided by a 90° coupler into two signals with a 90° phase difference as modulation signals input into a dual parallel Mach-Zehnder modulator, specifically: The baseband signal generated by the baseband signal source is divided into a 0° phase-shifted baseband signal and a 90° phase-shifted baseband signal by a 90° coupler; wherein the 90° phase-shifted baseband signal is injected into the first Mach-Zehnder modulator as a modulation signal, and the 0° phase-shifted baseband signal is injected into the second Mach-Zehnder modulator as a modulation signal. The output signal of the second Mach-Zehnder modulator will be optically phase-shifted on the main modulation arm optical phase shifter of the dual parallel Mach-Zehnder modulator. The optical signal after phase shifting and the optical signal of the first Mach-Zehnder modulator are combined into one light in the waveguide of the dual parallel Mach-Zehnder modulator and enter the optical filter.

8. The microwave photon ultra-wideband tunable linear frequency modulation signal generator according to claim 1, characterized in that: The second laser is a tunable laser, and the frequency of the output signal can be changed by adjusting the output frequency of the second laser.

9. The microwave photon ultra-wideband tunable linear frequency modulation signal generator according to claim 1, characterized in that: The optical filter is a bandpass filter, and its bandwidth is greater than or equal to the working bandwidth of the baseband signal source.

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