CN113965272A - Microwave photon channelized receiver linearization method - Google Patents
Microwave photon channelized receiver linearization method Download PDFInfo
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- CN113965272A CN113965272A CN202111195506.9A CN202111195506A CN113965272A CN 113965272 A CN113965272 A CN 113965272A CN 202111195506 A CN202111195506 A CN 202111195506A CN 113965272 A CN113965272 A CN 113965272A
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
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- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6163—Compensation of non-linear effects in the fiber optic link, e.g. self-phase modulation [SPM], cross-phase modulation [XPM], four wave mixing [FWM]
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Abstract
The invention discloses a linearization method of a microwave photon channelized receiver, belonging to the technical field of communication. The method comprises the following steps: modulating a radio frequency signal to an optical frequency comb through a Mach-Zehnder modulator, converting the radio frequency signal into an electric signal through a balance detector through channel division and down-conversion, and converting the electric signal through an ADC (analog-to-digital converter) to obtain a nonlinear distorted digital signal; and (3) performing band-pass filtering processing on the digital signal, and then performing digital signal processing by adopting an iterative algorithm to obtain a linearized signal. The method is simple and easy to implement, and can solve the problem of nonlinear distortion of a channelized receiver channel.
Description
Technical Field
The invention belongs to the technical field of communication and signal processing, and particularly relates to a linearization method of a microwave photon channelized receiver.
Background
The microwave photon technology is to introduce electric/optical/electric conversion in microwave communication, and the process is to output optical carrier wave by a laser, modulate radio frequency signal to optical signal by an electro-optical modulator, perform frequency, phase, filtering and other processing on optical domain, and finally obtain transmitted and processed radio frequency signal by a photoelectric detector. The microwave photon technology has the advantages of large bandwidth, small loss, electromagnetic interference resistance and the like, and is widely applied to radio over fiber communication, channelized reception, light-operated phased array radar and the like.
The final measure for measuring the performance of the microwave photonic link is the dynamic range of the link, which is defined as the ratio of the maximum signal power to the minimum signal power that can be detected, and when the power of the input radio frequency signal increases, the signal will be affected by the non-linearity of mixing, frequency doubling, intermodulation, etc. to cause the distortion of the signal, wherein the non-linear distortion with the largest effect is the third-order intermodulation in the third-order non-linear distortion. The third-order intermodulation distortion is often generated by a nonlinear cosine function of a transfer function of the Mach-Zehnder modulator, and is different from a third-order harmonic component, and the third-order intermodulation distortion is difficult to eliminate due to the fact that the frequency difference between the third-order intermodulation distortion and a frequency of a fundamental frequency signal is very close to each other on a frequency spectrum, so that the third-order intermodulation distortion is a main factor for limiting the dynamic range of a microwave optical sub-channelized receiver.
At present, microwave photon linear optimization technology can be divided into linear optimization technology based on third-order intermodulation distortion self-cancellation, linear optimization technology based on partial suppression of third-order intermodulation distortion and linear optimization technology based on digital domain processing. The basic principle of the self-cancellation linear optimization technology is to cancel and suppress the third-order intermodulation distortion from different sources, and the method can achieve maximum suppression of the third-order intermodulation distortion theoretically, but the method requires different modulators to work at special working points, and achieves self-cancellation through modes of filtering, attenuation, phase inversion and the like, while the existing bias control circuit board can only lock the modulators at the conventional working points and cannot meet the requirements of schemes. Yet another approach is to suppress part of the sources of third-order intermodulation distortion, such as suppressing third-order intermodulation with minimum offset, but only suppressing one source of third-order intermodulation. In addition to the above compensation of nonlinear distortion in the analog domain, there is also a method of compensation directly in the digital domain, and the specific idea is to perform analog-to-digital conversion and sampling on the obtained signal at the receiving end and then perform digital signal processing, and to construct a nonlinear system in the digital domain to counteract the original nonlinear distortion. The microwave optical sub-channelized receiving system is difficult to perform nonlinear compensation in an analog domain, and how to suppress and compensate third-order intermodulation distortion in a digital domain in a simple and effective manner is a problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a linearization method of a microwave optical-wave channelized receiver, which aims to solve the problem of nonlinear distortion of signals modulated by a Mach-Zehnder modulator in the prior art.
In order to achieve the purpose, the invention adopts the technical scheme that:
a microwave photon channelized receiver linearization method includes the following steps:
1) obtaining digital nonlinear distortion signals of any channel in the channelized receiver after analog-to-digital conversion, and measuring input third-order intercept point IIP3 of a link and half-wave voltage V of a Mach-Zehnder modulatorπ,rfAnd calculating a linearization parameter a:
wherein Z is the impedance of a detector in the channelized receiver;
2) performing band-pass filtering on the digital nonlinear distortion signal in a digital domain to obtain a processed signal y;
3) performing iterative operation by taking the signal y as an initial input signal; in each iteration, firstly, an input signal y' of the current iteration is squared and then low-pass filtering processing is carried out, and the processed signal is input into the following formula to obtain a correction coefficient T of the current iteration:
in the formula, m is an accumulated variable and is a non-negative integer;
then the iteration isDividing the input signal y' by the correction coefficient T of the iteration to obtain the output signal y of the iteration0：
y0＝y′/T；
The input signal of the next iteration is the output signal of the previous iteration;
4) and finishing iteration when the output signal is converged to obtain a linearized result.
Further, the digital nonlinear distortion signal in step 1) is an intermediate frequency or baseband signal obtained by down-converting a signal optical comb and a local oscillator optical comb in the channelized receiver.
The invention has the beneficial effects that:
1. the invention does not need to determine a complex compensation function by measuring a plurality of link parameters in the digital domain linearization process.
2. The method is simple to realize and fast in iterative convergence.
Drawings
FIG. 1 is a schematic diagram of microwave-optical channelized reception according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a linearization iteration algorithm in the embodiment of the invention.
Fig. 3 is a diagram illustrating unprocessed link nonlinearities actually measured in an embodiment of the invention.
Fig. 4 is a schematic diagram of the actually measured nonlinear link after the linearization process in the embodiment of the invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, the following detailed description of the invention is provided in conjunction with the accompanying drawings and the detailed description of the invention.
Referring to fig. 1, the microwave optical sub-channelized reception is composed of a broadband radio frequency signal dividing module and a coherent detection signal processing module. The system inputs a radio frequency signal to be detected, the radio frequency signal is divided into a plurality of channels through a broadband radio frequency signal dividing module, and different channels are subjected to down-conversion, analog-to-digital conversion and linear signal processing in a coherent detection signal processing module. The Mach-Zehnder modulator MZM is used for modulating an input broadband radio frequency signal to each comb tooth of a signal optical frequency comb, different comb teeth and corresponding local oscillation optical comb teeth are received coherently after wavelength division and demultiplexing, the broadband radio frequency signal is divided into a plurality of narrow-band signals by a channel and is converted into an electrical signal through a balanced optical detector BPD, the electrical signal is converted through an analog-to-digital converter ADC, and the obtained digital signal is processed through a DSP algorithm, so that nonlinear distortion can be counteracted to a certain degree, and a high-fidelity signal is obtained.
Referring to fig. 2, in the method for linearizing a microwave optical sub-channelized receiver, a down-converted signal received by a detector is converted into y after analog-to-digital conversion, conversion from a distorted signal to an ideal signal is realized through iterative processing, and a parameter a in the processing is obtained through testing. The method specifically comprises the following steps:
1) obtaining digital nonlinear distortion signals of any channel in the channelized receiver after analog-to-digital conversion, and measuring input third-order intercept point IIP3 of a link and half-wave voltage V of a Mach-Zehnder modulatorπ,rfAnd calculating a linearization parameter a:
wherein Z is the impedance of a detector in the channelized receiver;
2) performing band-pass filtering on the digital nonlinear distortion signal in a digital domain to obtain a processed signal y;
3) performing iterative operation by taking the signal y as an initial input signal; in each iteration, firstly, an input signal y' of the current iteration is squared and then low-pass filtering processing is carried out, and the processed signal is input into the following formula to obtain a correction coefficient T of the current iteration:
in the formula, m is an accumulated variable and is a non-negative integer;
then dividing the input signal y' of the iteration with the correction coefficient T of the iteration to obtain the output signal y of the iteration0：
y0＝y′/T；
The input signal of the next iteration is the output signal of the previous iteration;
4) and finishing iteration when the output signal is converged to obtain a linearized result.
The digital nonlinear distortion signal in step 1) is an intermediate frequency or baseband signal obtained by down-conversion of a signal optical comb and a local oscillator optical comb in the channelized receiver.
In this example, the output signal ripple is within 2dBm after three iterations.
As can be seen from FIGS. 3 and 4, the third-order intermodulation suppression ratio of the link after the iteration processing is 59.04dBm, which is improved by 27dB compared with the 31.44dBm without the linearization processing.
In conclusion, the invention realizes a linearization method of a microwave photon channelized receiver, and realizes the third-order intermodulation suppression of the down-conversion signal of the channelized receiver through a simple and easily realized algorithm.
The above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (2)
1. A method for linearizing a microwave optical channelized receiver, comprising the steps of:
1) obtaining digital nonlinear distortion signals of any channel in the channelized receiver after analog-to-digital conversion, and measuring input third-order intercept point IIP3 of a link and half-wave voltage V of a Mach-Zehnder modulatorπ,rfAnd calculating a linearization parameter a:
wherein Z is the impedance of a detector in the channelized receiver;
2) performing band-pass filtering on the digital nonlinear distortion signal in a digital domain to obtain a processed signal y;
3) performing iterative operation by taking the signal y as an initial input signal; in each iteration, firstly, an input signal y' of the current iteration is squared and then low-pass filtering processing is carried out, and the processed signal is input into the following formula to obtain a correction coefficient T of the current iteration:
in the formula, m is an accumulated variable and is a non-negative integer;
then dividing the input signal y' of the iteration with the correction coefficient T of the iteration to obtain the output signal y of the iteration0：
y0＝y′/T；
The input signal of the next iteration is the output signal of the previous iteration;
4) and finishing iteration when the output signal is converged to obtain a linearized result.
2. The linearization method of a microwave optical sub-channelized receiver as claimed in claim 1, wherein the digital nonlinear distortion signal in step 1) is an intermediate frequency or baseband signal obtained by down-converting a signal optical comb and a local oscillator optical comb in the channelized receiver.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115514423A (en) * | 2022-08-22 | 2022-12-23 | 中国电子科技集团公司第十四研究所 | Method for improving microwave photon channelized dynamic range |
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| CN104618023A (en) * | 2014-12-30 | 2015-05-13 | 北京邮电大学 | Optical link linearization method |
| CN105099971A (en) * | 2015-07-30 | 2015-11-25 | 北京邮电大学 | Processing method and system of nonlinear distortion signals |
| US20190319634A1 (en) * | 2018-04-14 | 2019-10-17 | Shanghai Jiao Tong University | High-speed and high-precision photonic analog-to-digital conversion device and method for realizing intelligent signal processing using the same |
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| CN104618023A (en) * | 2014-12-30 | 2015-05-13 | 北京邮电大学 | Optical link linearization method |
| CN105099971A (en) * | 2015-07-30 | 2015-11-25 | 北京邮电大学 | Processing method and system of nonlinear distortion signals |
| US20190319634A1 (en) * | 2018-04-14 | 2019-10-17 | Shanghai Jiao Tong University | High-speed and high-precision photonic analog-to-digital conversion device and method for realizing intelligent signal processing using the same |
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| 刘潇: "大动态微波光子链路及非线性失真分析", 《中国优秀硕士学位论文全文数据库 信息科技辑》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115514423A (en) * | 2022-08-22 | 2022-12-23 | 中国电子科技集团公司第十四研究所 | Method for improving microwave photon channelized dynamic range |
| CN115514423B (en) * | 2022-08-22 | 2024-02-27 | 中国电子科技集团公司第十四研究所 | Method for improving microwave photon channelized dynamic range |
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