High-amplitude consistency microwave photon receiving module

Abstract

The invention provides a microwave photon receiving module with high amplitude consistency, and aims to solve the technical problems of large amplitude difference between channels, poor optical path matching maintenance interchangeability and high complexity of a feedback compensation regulation and control system in a multi-channel radio frequency transmission distribution network based on microwave photons at present. According to the invention, a radio frequency saturation amplification chain is introduced after photoelectric conversion, and the gain of each stage of amplifier is regulated and controlled, so that the final radio frequency amplification works in a saturation state, and in a certain saturation depth range, the optical power difference entering photoelectric conversion and the photoelectric conversion device difference do not cause obvious influence on the amplitude of the final radio frequency output; and the purpose of high-amplitude consistent radio frequency output regulation and control is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of light-borne radio frequency, and in particular relates to a high-amplitude consistency microwave photon receiving module. Background Art

[0002] For low-frequency active phased array radars, a single aperture can no longer cope with their growing application needs. In the future, ultra-large apertures will be achieved based on the coherent synthesis of multiple distributed apertures to obtain sufficient antenna gain and compensate for the substantial reduction in the platform's power supply capacity, thereby achieving high-resolution multi-angle detection and improving system maneuverability and target detection performance. In order to meet the needs of large apertures and distribution, it is necessary to complete the long-distance transmission and distribution of various RF signals such as clocks and local oscillators required by phased array radars; at the same time, in order to meet the system's low load and weak power supply requirements, it is necessary to build a lightweight, low-density transmission and distribution network. Replacing electricity with light, supplemented by a wealth of time-space frequency-energy multiplexing technology, is the key to achieving the transmission and distribution of reference and analog signals between the above-mentioned distributed antenna units and the central node.

[0003] Phased arrays have high requirements for amplitude and phase consistency between channels, but the reference and analog signal transmission and distribution networks built on traditional microwave photonic transmission links often have difficulty meeting the requirements in terms of amplitude consistency. On the one hand, the performance differences of the active devices that complete electro-optical modulation and optoelectronic conversion will lead to inconsistent amplitudes of the final output RF signals; on the other hand, the key unit in the optical transmission and distribution network, the optical splitter, cannot evenly divide the power of the input optical carrier, and the amplitude difference caused by uneven optical distribution will worsen as the number of network nodes increases.

[0004] In order to eliminate this amplitude difference, existing practices have been carried out to regulate the optical path and circuit respectively. Optical path regulation is divided into two types: optical fiber allocation optimization and optical power automatic feedback compensation. The specific solution for optical fiber allocation optimization is to reduce the inconsistency of insertion loss and connection loss by optimizing the internal structure of the connector, and at the same time screen the optical splitter core parts, and remove those with large loss deviations from the statistical mean. Finally, according to the insertion loss values ​​of each component, the optical path matching order is adjusted during the debugging of the entire product, so as to achieve the purpose of optimizing the overall link amplitude difference. However, this approach has a low yield rate and poor maintenance and interchangeability. The specific solution for optical power automatic feedback compensation is to introduce a multi-channel variable optical attenuator (VOA) to improve the consistency of the optical splitter. The optical splitter chip can be integrated with the multi-channel VOA chip through photonic integration, and a closed loop can be constructed. The driving voltage of the multi-channel VOA is controlled by monitoring the output optical power feedback of each node, thereby changing the loss value of each channel VOA, and finally obtaining a design optimization with high amplitude consistency of each node. It should be noted that due to the difference in loss of the connecting optical cable, the entire closed-loop control needs to be carried out after the integrated connecting transmission optical cable forms a complete closed-loop circuit, and the monitoring of optical power needs to be completed at the input end of the microwave photon receiving module. The advantage of this approach is that it can perform real-time regulation based on the impact of the external environment on each node of the optical transmission distribution network, but since closed-loop feedback control is introduced at each array node, the complexity of the system is greatly increased, and since the optical power is monitored at the input end of the microwave photon receiving module, the output microwave amplitude difference caused by the inconsistency of the microwave photon receiving module cannot be eliminated. The traditional circuit control approach is similar to the idea of ​​automatic feedback compensation of optical power. By designing an electrically adjustable attenuator with sufficient attenuation range in the microwave photon receiving component, combined with closed-loop monitoring of the amplitude of the output microwave signal, and then feedback controlling the attenuation of the electrically adjustable attenuator, the purpose of optimizing the amplitude difference of each node is achieved. Compared with the closed-loop feedback control of the optical path, this method can effectively eliminate the amplitude difference caused by the difference in the devices of the optoelectronic conversion module, but the increase in system complexity caused by power monitoring and closed-loop feedback control of each node is still inevitable. At the same time, since an electrically adjustable attenuator is added before the final microwave output, the microwave power output in certain application scenarios may be difficult to meet the use requirements.

[0005] In summary, RF fiber optic transmission technology has become an effective means to complete the transmission and distribution of benchmark and analog signals in the "distributed, large-diameter, low-load, and weak power supply" scenarios, but there is an urgent need to seek new means to achieve high-amplitude consistency optimization of each node while not losing the system's maintainability and interchangeability, and not excessively increasing the system's complexity. Summary of the invention

[0006] In order to address the deficiencies in the prior art, the present invention proposes a method and device for achieving high amplitude consistency of each node in a multi-node microwave photonic transmission and distribution network of a reference / analog signal, aiming to solve the technical problems of large amplitude differences between channels, poor optical path matching, maintenance and interchangeability, and high complexity of the feedback compensation control system in the current multi-channel RF transmission and distribution network based on microwave photons.

[0007] A high amplitude consistency microwave photon receiving module of the present invention comprises a photodetector, a first low phase noise amplifier, a radio frequency attenuator, a second low phase noise amplifier, a low-pass filter, etc. Among them, the radio frequency output end of the photodetector is connected to the input end of the first low phase noise amplifier, the output end of the first low phase noise amplifier is connected to the input end of the radio frequency attenuator, the output end of the radio frequency attenuator is connected to the input end of the second low phase noise amplifier, and the output end of the second low phase noise amplifier is connected to the input end of the low-pass filter. The photodetector is used to convert the input light-carrying RF signal into an RF signal. The first low phase noise amplifier is used to drive and amplify the RF signal output by the photodetector. The RF attenuator is used to adjust the RF power of the driving amplifier output to avoid oversaturation of the next stage of RF amplification, and at the same time play the role of RF isolation between the two stages of amplification to avoid link instability caused by excessive gain of a single stage. The second low phase noise amplifier is used to saturate the RF signal and ensure the stability of the amplitude of the output RF signal when the amplitude of the input RF signal fluctuates through appropriate RF power compression. The low-pass filter is used to suppress the higher harmonics of the transmitted RF signal. The single-mode optical fiber is used for the input RF cable of the light-carrying microwave signal and is used for the RF connection between the chips / devices inside the module while maintaining low loss.

[0008] The photodetector realizes photoelectric conversion, converting the input light-carrying RF signal into RF signal output; the first low phase noise amplifier works in a linear amplification state, and plays the role of driving and amplifying the RF signal output by the photoelectric conversion; the RF attenuator is placed between the two low phase noise amplifiers, and plays the purpose of RF isolation between the two stages of amplification and regulating the RF power distribution of the link. Its attenuation needs to be determined according to the link gain distribution. The principle to follow is to let the second stage low phase noise amplifier work in a saturated state and avoid too deep saturation depth; the second low phase noise amplifier works in a saturated amplification state, and through appropriate RF power compression, it ensures that the output RF signal amplitude is stable when the input RF signal amplitude fluctuates; the role of the low-pass filter is to allow the transmitted fundamental signal to pass and suppress its higher harmonics. It should be supplemented that the first and second amplifiers are both low phase noise amplifiers. The purpose is to obtain sufficient RF gain without deteriorating the phase noise of the transmitted reference signal or analog signal.

[0009] The present invention introduces a radio frequency saturation amplification chain after the photoelectric conversion, and regulates the gain of each stage of amplifiers so that the final radio frequency amplification works in a saturated state, so that within a certain saturation depth range, the difference in optical power entering the photoelectric conversion and the difference in the photoelectric conversion device will not have a significant impact on the amplitude of the final radio frequency output, thereby achieving the purpose of high amplitude consistency radio frequency output regulation. The present invention adopts a multi-stage amplification final stage saturation scheme, the purpose of which is to avoid link instability caused by excessive single-stage amplification gain. By adding radio frequency attenuation between multiple stages of amplification, the gain distribution of the amplification chain can be flexibly regulated, further improving the stability and reliability of the link. In addition, a low-pass filter is connected in series at the output end of the final stage of the amplifier, which can play a certain inhibitory role in the deterioration of harmonic performance caused by radio frequency saturation amplification. It should be noted that the final stage saturation depth of the link of the present invention should not be too large, and phase deviation caused by the strong nonlinear effect under deep saturation should be avoided.

[0010] The photodetector is a PIN type photodetector; preferably, the 1dB saturation point of its input optical power should be no less than 10dBm, and the responsivity should be no less than 0.8A / W.

[0011] The first low phase noise amplifier operates in a linear power amplification mode. In a specific implementation, when the amplifier is in the maximum gain state, different RF power values ​​output by the photodetector will not cause the amplifier to saturate. That is, the output 1dB compression point P of the amplifier 1-out1dB Should satisfy P 1-out1dB ≥P out-PD(max) +G 1 +1(dB), where P out-PD(max) Represents the maximum RF power output by the photodetector, G 1 Represents the gain of the amplifier.

[0012] The attenuation of the RF attenuator is a fixed value, and the selection of its attenuation L should follow the following formula:

[0013] L=(P out-PD ( max )+G 1 )-(P 2-sat +D max -G 2 )(dB); where P 2-sat represents the saturated output power of the second lowest phase noise amplifier, D max represents the maximum saturation depth of the second lowest phase noise amplifier, G 2 represents the gain of the second low phase noise amplifier.

[0014] The second low phase noise amplifier operates in a saturated power amplification mode. In a specific implementation, when the amplifier is in the maximum gain state, different RF power values ​​output by the photodetector will cause the amplifier to saturate. That is, the output power saturation point P of the amplifier 2-sat The following relationship should be satisfied:

[0015] P 2-sat ≥(P out-PD(min) +G 1 )-L+G 2 -D min (dB); where P out-PD(min) Denotes the minimum RF power output by the photodetector, D min Indicates the minimum saturation depth of the second lowest phase noise amplifier.

[0016] The cutoff frequency f of the low pass filter c The typical value of f should meet: c ≤1.2f 0 Where, f 0 Indicates the frequency of the transmitted signal, and its stopband attenuation should meet ≥20@2f 0 (dB) in order to achieve better high-order harmonic suppression effect.

[0017] The first low phase noise amplifier and the second low phase noise amplifier should both have low additional phase noise, and will not significantly deteriorate the phase noise of the transmitted RF signal during the process of amplifying the RF signal. The additional phase noise level should meet (f 0 =100MHz): ≤-145dBc / Hz@100Hz, ≤-160dBc / Hz@1kHz, ≤-165dBc / Hz@10kHz, ≤-170dBc / Hz@100kHz and beyond. Preferably, such amplifiers should adopt HBT technology with lower additive phase noise.

[0018] The maximum saturation depth D of the second low phase noise amplifier max The value of should not be greater than 10dB, so as to avoid the amplifier working in a deep saturation state and causing phase distortion; preferably, D max The value should not be greater than 6dB.

[0019] The minimum saturation depth D of the second lowest phase noise amplifier min The value of should be no less than 1dB to ensure that the amplifier works in saturation for different detector power outputs. min The value should not be less than 2dB.

[0020] The beneficial effects of the present invention are

[0021] By introducing the RF saturation amplification mechanism at the output end of the photoelectric conversion, the problem of large differences in the amplitude of the microwave photon receiving module output signal caused by inconsistent input optical power at the photoelectric conversion end and inconsistent losses of photoelectric passive components can be effectively solved. The use of complex electrical / optical power monitoring feedback compensation control units is avoided, which greatly reduces the system complexity and module cost. The solution has good manufacturability, high module yield and good reliability.

[0022] The present invention can be widely used in fields where UAV-mounted, boat-mounted and other flying platforms have higher demands on phased array radar payloads, and is the key to achieving the transmission and distribution of reference and analog signals under "distributed, large aperture, lightweight, and weak power supply". BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a block diagram of the present invention.

[0024] Figure 2 The figure is a schematic diagram of link gain allocation in an embodiment. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides a microwave photon receiving module for realizing the distributed multi-node transmission distribution of reference signals or analog signals, and having good output microwave signal amplitude consistency. Figure 1 ,include:

[0027] 1—Photodetector, used to convert the input light-carrying RF signal into RF signal.

[0028] 2-1—The first low phase noise amplifier is used to drive and amplify the radio frequency signal output by the photodetector. The amplifier has low additional phase noise and works in a linear amplification mode. While amplifying the radio frequency signal output by the photodetector, the phase noise of the radio frequency signal will not be significantly deteriorated.

[0029] 2-2—The second low phase noise amplifier is used to saturate the RF signal and to ensure the stability of the output RF signal amplitude when the input RF signal amplitude fluctuates through appropriate RF power compression. The amplifier works in saturation amplification mode, but its saturation depth does not exceed 6dB to avoid phase distortion caused by excessive nonlinear effects under deep saturation. At the same time, the amplifier is also a low additional phase noise amplifier to avoid significant deterioration of the phase noise of the transmitted RF signal during the amplification process.

[0030] 3—RF attenuator, used for RF isolation between two-stage amplification to improve link stability. At the same time, by optimizing the attenuation of the RF attenuator, the RF power entering the second low phase noise amplifier is regulated so that it can work at saturation while avoiding deep saturation.

[0031] 4—Low-pass filter, which filters the RF signal output by the second low phase noise amplifier. It has low loss on the fundamental signal and suppresses high-order harmonics, so that the harmonic indicators of the output RF signal meet the requirements and avoid the problem of harmonic indicators exceeding the tolerance due to RF saturation amplification.

[0032] 5—Single-mode optical fiber, used to connect the module to the external optical path, such as Figure 1 Shown by the solid black line.

[0033] 6—RF connection cable, used for transmission of RF signals, such as Figure 1 Indicated by the black dashed line.

[0034] The following is an introduction to a microwave photon receiving module with a 100MHz clock reference. This embodiment realizes the microwave photon transmission distribution of a signal with a power of 12dBm generated by a 100MHz crystal oscillator. When the optical power entering the detector differs by ±1dB, the output RF power can be stabilized at 17dBm. In this embodiment, the main parameters of each device are as follows:

[0035] The operating wavelength of the photodetector is 1550nm, the typical operating voltage is +5V, the saturated input optical power at 1dB compression point is 13dBm; the average input optical power is 9.5±1dBm, the responsivity is 0.9A / W@100MHz; and the 3dB bandwidth is ≥3GHz.

[0036] The operating frequency range of the low phase noise amplifier is 0.01 to 2 GHz, the RF gain is 19 dB, and the 1 dB compression point output RF power is 13 dBm.

[0037] The operating frequency range of the low phase noise amplifier is 0.01~2GHz, the RF gain is 19dB, and the saturated output RF power is 19dBm.

[0038] The attenuation value of the RF attenuator is 7dB@100MHz.

[0039] The insertion loss of the RF filter is 2dB@100MHz, the cut-off frequency is typically 120MHz, and the stop-band attenuation is ≥20dB@0.2GHz.

[0040] like Figure 2 The power distribution of each level of this embodiment is shown. The calculation of the gain G of the intrinsic radio frequency optical transmission link composed of the direct-modulated laser, the optical fiber jumper and the photodetector satisfies the following formula:

[0041] G=20lg(S l ·R d / 2)-2×L opt

[0042] =20×lg(0.25×0.45)-2×1.5

[0043] ≈-22dB

[0044] In the formula, S ld represents the slope efficiency of the direct-modulated laser, in W / A (in this embodiment, the slope efficiency of the laser is 0.25 W / A); R d Indicates the responsivity of the photodetector, in A / W; L opt represents the link optical insertion loss (in this embodiment, the link optical loss is 1.5±1dB).

[0045] from Figure 2 It can be seen that, without considering the differences in optoelectronic active / passive chips / devices, the power difference of the detector output is ±2dB due to the difference in the input optical power of the photodetector. Through the method of pushing saturation at the end of the two-stage amplification and combining low-pass filtering, the final output RF power is stabilized at 17dBm. In the entire link, the saturation depth of the second-stage RF amplification is set within the range of 2 to 6dB, avoiding deep saturation and causing no phase distortion.

[0046] So far, the “a microwave photon receiving module with high amplitude consistency” of the present invention has been described in detail in conjunction with the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the “a microwave photon receiving module with high amplitude consistency” of the present invention.

[0047] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0048] In summary, the present invention "a microwave photon receiving module with high amplitude consistency" introduces a radio frequency saturation amplification mechanism at the output end of the photoelectric conversion, and through appropriate radio frequency power compression in the final stage of saturation amplification, ensures that the amplitude of the module output radio frequency signal is stable when the amplitude of the input optical power of the microwave photon receiving module fluctuates and there are differences in the loss of the photoelectric active / passive chips or devices in the module. The module does not need to use a complex electrical / optical power monitoring feedback compensation control unit, has a simple structure, low cost, high yield rate, and good reliability.

Claims

1. A microwave photon receiving module with high amplitude consistency, characterized by: include: A photodetector, a first low phase noise amplifier, a radio frequency attenuator, a second low phase noise amplifier, and a low pass filter; The radio frequency output end of the photodetector is connected to the input end of the first low phase noise amplifier, the output end of the first low phase noise amplifier is connected to the input end of the radio frequency attenuator, the output end of the radio frequency attenuator is connected to the input end of the second low phase noise amplifier, and the output end of the second low phase noise amplifier is connected to the input end of the low pass filter; The photoelectric detector is used to convert the input light-carrying radio frequency signal into a radio frequency signal; The first low phase noise amplifier is used to drive and amplify the radio frequency signal output by the photodetector; The RF attenuator is used to adjust the RF power of the driving amplifier output to avoid oversaturation of the next stage of RF amplification, and at the same time plays a role in RF isolation between the two stages of amplification to avoid excessive single-stage gain causing link instability; The second low phase noise amplifier is used to perform saturation amplification on the radio frequency signal, and ensure the stability of the amplitude of the output radio frequency signal when the amplitude of the input radio frequency signal fluctuates through appropriate radio frequency power compression; The low-pass filter is used to suppress higher harmonics of the transmitted radio frequency signal; The single-mode optical fiber is used for inputting optically carried microwave signals; The radio frequency cable is used for radio frequency connection between chips / devices inside the module while maintaining low loss.

2. The high amplitude consistency microwave photon receiving module according to claim 1, characterized in that: The photodetector is a PIN type photodetector; the 1dB saturation point of its input optical power is not less than 10dBm, and the responsivity should be not less than 0.8A / W.

3. The high amplitude consistency microwave photon receiving module according to claim 1, characterized in that: The first low phase noise amplifier operates in a linear power amplification mode. In the maximum gain state, different radio frequency power values ​​output by the photodetector will not cause the first low phase noise amplifier to saturate.

4. The high amplitude consistency microwave photon receiving module according to claim 1, characterized in that: The attenuation of the radio frequency attenuator is a fixed value.

5. The high amplitude consistency microwave photon receiving module according to claim 1, characterized in that: The second low phase noise amplifier operates in a saturated power amplification mode. In the maximum gain state, different radio frequency power values ​​output by the photodetector will cause the second low phase noise amplifier to saturate.

6. The high amplitude consistency microwave photon receiving module according to claim 1, characterized in that: The cut-off frequency f of the low-pass filter c The typical value of f should meet: c ≤1.2f0; where f0 represents the frequency of the transmitted signal, and its stop-band attenuation should satisfy ≥20@2f0.

7. The high amplitude consistency microwave photon receiving module according to claim 1, characterized in that: The first low phase noise amplifier and the second low phase noise amplifier both have relatively low additional phase noise.

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