Phase noise measuring device and measuring method based on laser frequency discrimination and cross-correlation processing
阅读说明：本技术 基于激光鉴频和互相关处理的相位噪声测量装置和测量方法 (Phase noise measuring device and measuring method based on laser frequency discrimination and cross-correlation processing ) 是由 邹卫文 李成功 于磊 钱娜 陈建平 于 2019-10-22 设计创作，主要内容包括：基于激光鉴频和互相关处理的相位噪声测量装置和测量方法。一种激光锁相互相关处理相位噪声测量,包含两条相同的独立测量链路,每一条都包括激光源模块、延迟线模块、光电混频模块、光电转换模块,另外待测信号模块和数据采集及互相关算法处理模块是两条链路共有的。本发明可以降低测量链路的底噪,提高噪声灵敏度,提高链路测量精度。(A phase noise measuring device and a measuring method based on laser frequency discrimination and cross-correlation processing are provided. The utility model provides a laser lock looks cross correlation handles phase noise measurement, contains two the same independent measurement links, and each includes laser source module, delay line module, photoelectricity mixing module, photoelectric conversion module, and signal module to be measured and data acquisition and cross correlation algorithm processing module are two links sharing in addition. The invention can reduce the bottom noise of the measuring link, improve the noise sensitivity and improve the link measuring precision.)
1. A phase noise measurement device based on laser frequency discrimination and cross-correlation processing, comprising: the signal module (1) that awaits measuring, first laser source (2), second laser source (3), first delay line module (4), second delay line module (5), first photoelectricity frequency mixing module (6), second photoelectricity frequency mixing module (7), first photoelectric detection module (8), second photoelectric detection module (9), data acquisition and cross-correlation algorithm processing module (10), the relation of connection is as follows:
the output end one of the signal source (1) to be tested is divided into four parts: respectively connected to the first input terminal of the first opto-electric frequency mixing module (6), the first input terminal of the opto-electric frequency mixing source module (7), the input terminal of the first laser source (2) and the input terminal of the second laser source (3), the output terminal of the first laser source (2) is connected to the input terminal of the first delay line module (4), the output terminal of the second laser source (3) is connected to the input terminal of the second delay line module (5), the output terminal of the first delay line module (4) is connected to the second input terminal of the first opto-electric frequency mixing module (6), the output terminal of the second delay line module (5) is connected to the second input terminal of the second opto-electric frequency mixing module (7), the output terminal of the first opto-electric frequency mixing module (6) is connected to the input terminal of the first opto-electric detection module (8), the output end of the second photoelectric frequency mixing module (7) is connected with the input end of the second photoelectric detection module (9), the output end of the first photoelectric detection module (8) is connected with the first input end of the data acquisition and cross-correlation algorithm processing module (10), the output end of the second photoelectric detection module (9) is connected with the second input end of the data acquisition and cross-correlation algorithm processing module (10), the data acquisition and cross-correlation algorithm processing module (10) is a computer with labview and MATLAB data processing software, and the reference clock end of the data acquisition and cross-correlation algorithm processing module (10) is connected with the reference clock end of the signal source module (1) to be detected.
2. The phase noise measurement device based on laser frequency discrimination and cross-correlation processing as claimed in claim 1, wherein the signal module (1) to be measured is a voltage controlled oscillator or a frequency synthesizer.
3. The phase noise measurement device based on laser frequency discrimination and cross-correlation process as claimed in claim 1, wherein the first laser source module (2) and the second laser source module (3) are active mode-locked lasers or modulation frequency combs.
4. The phase noise measurement device based on laser frequency discrimination and cross-correlation processing as claimed in claim 1, wherein the first delay line module (4) and the second delay line module (5) are single mode fiber, polarization maintaining fiber or dispersion flat fiber.
5. The phase noise measurement device based on laser frequency discrimination and cross-correlation processing as claimed in claim 1, wherein the first and second electro-optical mixing modules (6, 7) are lithium niobate electro-optical modulator, polymer electro-optical modulator, silicon-based integrated electro-optical modulator or spatial light modulator.
6. The phase noise measurement device based on laser frequency discrimination and cross-correlation processing as claimed in claim 1, wherein the first photo-detection module (8) and the second photo-detection module (9) are PIN tubes or APD tubes.
7. A method of measuring phase noise based on laser frequency discrimination and cross-correlation as claimed in any one of claims 1 to 4, the method comprising the steps of:
1) the output end of a signal module to be tested (1) is respectively connected with the input ends of the first laser source module (2), the second laser source module (3), the first photoelectric frequency mixing module (6) and the second photoelectric frequency mixing module (7);
2) optical domain signals output by the first laser source module (2) and the second laser source module (3) introduce time delay through the first delay line module (4) and the second delay line module (5), and optical domain signals obtained after time delay are input into the first photoelectric mixing module (6) and the second photoelectric mixing module (7) respectively;
3) the delayed optical domain signal and the signal to be detected complete frequency mixing treatment in the first photoelectric frequency mixing module (6) and the second photoelectric frequency mixing module (7);
4) the mixed signals enter a first photoelectric detection module (8) and a second photoelectric detection module (9), high-frequency signals can be filtered by selecting the first photoelectric detection module (8) and the second photoelectric detection module (9) with low bandwidth, noise signals are obtained, and conversion from optical domain signals to electric signals is completed;
4) acquiring the electric signals output by the first photoelectric detection module (8) and the second photoelectric detection module (9) by respectively setting the acquisition bandwidths of the data acquisition and cross-correlation algorithm processing modules (10) to be 200Hz, 2000Hz, 20KHz, 200KHz and 2MHz in sequence, and correspondingly acquiring noise signals in frequency deviation ranges of 10-100 Hz, 100-1000 Hz, 1000 Hz-10 KHz, 10 KHz-100 KHz and 100 KHz-1 MHz respectively;
5) and the computer performs cross-correlation processing on the noise signal by using the existing labview and MATLAB data processing software to obtain phase noise.
Technical Field
The invention relates to an optical information processing technology, in particular to a phase noise measuring device and a phase noise measuring method based on laser frequency discrimination and cross-correlation processing, which realize high-precision phase noise measurement of high-frequency signals in a large measurement bandwidth.
Background
The phase noise plays more and more important influence on the current radio frequency microwave processing, radar detection system and communication system, influences various indexes of the system, and has important guiding significance in the research and development design of the system structure, so that the accurate phase noise measurement can effectively improve the performance of the system. The phase noise measurement method mainly includes a phase discrimination method, a frequency discrimination method and a direct spectrum measurement method, wherein the phase discrimination method extracts a noise signal by mixing a reference signal and a signal to be measured and filtering a high-frequency component by using a filter. Generally, the phase noise of a reference signal can be accurately measured only when the phase noise is 20dBm lower than that of a signal to be measured, and meanwhile, the relative jitter between the reference signal and the signal to be measured has important influence on the measurement result when frequency mixing is carried out, so a phase-locked loop link is usually built to reduce the jitter and improve the measurement performance; in the frequency discrimination method, the signal to be measured and the signal after the signal to be measured is delayed for a period of time need to be mixed to complete the measurement, and the method can obtain better measurement performance by improving the length of the delay line.
With the demand of radar detection resolution increasing and the data rate of information processing systems becoming higher and higher, it becomes more and more important to measure large-frequency bandwidth phase noise on high-frequency-band signals. This puts higher demands on the circuitry, and requires that the electronic device can measure signals in a high frequency band, and the current rf-based device can obtain an accurate measurement result in the phase noise measurement of low frequency signals, and can maintain a high noise sensitivity. However, as the frequency increases, the bandwidth of the rf device is difficult to satisfy the measurement condition, and the phase noise increases at high frequency, which introduces higher extra noise, whether as a reference source in noise measurement or as an active device in a subsequent measurement chain. For frequency discrimination, the tunable range of the rf-based delay line is low, which means that the frequency offset range is also low. Therefore, the measurement of the radio frequency device in the high frequency band signal can not meet the measurement requirement due to the limited bandwidth and noise performance
The phase noise measurement based on the frequency discrimination method needs to extract phase noise from a frequency mixer, a signal required by frequency mixing consists of a signal to be measured and a delay signal of the signal to be measured, the delay signal can be replaced by a signal generated by a photon technology, the required delay can be introduced by an optical delay line, the loss of the optical delay line is low, the link delay can be improved, and the measurement precision is improved. The narrow pulse generated by the photon technology can enable the signal to reach a high frequency band, and the measurement accuracy of the system can be improved due to the characteristic of low noise of the optical signal. With the gradual maturity of microwave photon technology, the bandwidth of a device for processing microwave signals is larger and larger, so that a very high measurement frequency band and an adjustable range can be achieved, and the range of offset frequency is improved. Therefore, the microwave photonic link has the advantages of large bandwidth and low jitter, and can perform phase noise measurement on high-frequency band signals.
In the data processing part at the back end, because any measurement link brings extra noise due to the existence of active devices, the noise sensitivity of the measurement scheme is limited, the noise of the part can be suppressed through a cross-correlation algorithm, the more the number of cross-correlations is adopted, the more obvious the extra noise can be suppressed, and the more accurate the measurement result is.
Disclosure of Invention
The invention aims to provide a phase noise measuring method aiming at the defects of the prior art. The method is based on the principle of photoelectric mixing, utilizes a laser to generate a low-phase noise optical signal, and utilizes the photoelectric mixer to extract phase noise. Through two independent measuring links, the additional noise of the links is suppressed by adopting a cross-correlation algorithm in a back-end data processing part, so that the noise sensitivity of the measuring links is improved.
The technical solution of the invention is as follows:
the utility model provides a laser lock looks cross correlation handles phase noise measurement, contains two the same independent measurement links, and each includes laser source module, delay line module, photoelectricity mixing module, photoelectric conversion module, and signal module and data acquisition and cross correlation algorithm processing module to be measured share in addition, and specific connection is as follows:
the output end of the signal module to be detected is divided into four, wherein two paths of the output ends are connected with the first input end of the photoelectric frequency mixing module in the two measuring links, the other two paths of the output ends are connected with the input end of the laser source module in the two measuring links, the output end of the laser source module is connected with the input end of the delay line module, the output end of the delay line module is connected with the second input end of the photoelectric frequency mixing module, the input end of the photoelectric frequency mixing module is connected with the input end of the photoelectric conversion module, the output end of the photoelectric conversion module is connected with the first input end of the data acquisition and cross-correlation algorithm processing module, and the reference clock end of the data acquisition and cross-correlation algorithm processing module is respectively connected with the reference clock end of the signal source module to be detected. .
The laser source is a modulation frequency comb or a master mode-locked laser.
The delay line module is a single mode fiber, a polarization maintaining fiber or a dispersion flat fiber.
The signal source to be tested is a voltage-controlled oscillator and a frequency synthesis source.
The photoelectric frequency mixing module is a lithium niobate electrooptical modulator, a polymer electrooptical modulator, a silicon-based integrated electrooptical modulator and a spatial light modulator.
The photoelectric detection module is a PIN tube or an APD tube.
Based on the technical characteristics, the invention has the following advantages:
1. the laser can be used for generating optical signals with low phase noise, the bottom noise of a measuring link can be reduced, and the noise sensitivity is improved.
2. The optical delay line can introduce large delay while keeping low loss of a link, and improves measurement accuracy.
3. In the photoelectric mixing process, the optical reference source signal pulse is narrow, the bandwidth is large, the adjustable range is large, and the offset frequency range of the measurement link is improved.
4. The two irrelevant measurement links are used, extra noise introduced in the two links is irrelevant due to the independence of the measurement process, the extra noise is suppressed by the data processing part by adopting a cross-correlation method, and the link measurement precision is improved.
Drawings
FIG. 1 is a block diagram of an embodiment of the present invention for measuring noise by laser phase-locked cross-correlation
FIG. 2 is a diagram of the time delay process and the optical-electrical mixing process of the optical domain signal of the present invention
Detailed Description
The present invention will be described in detail below with reference to the drawings and examples, but the scope of the present invention is not limited to the examples described below.
In this embodiment, as shown in fig. 1, the phase noise measurement device based on laser frequency discrimination and cross-correlation processing includes a
the output end of the
In the process, the laser source provides optical signals with low noise, phase noise introduced during photoelectric mixing is reduced, meanwhile, two identical but independent measuring links are adopted in the method, the phase noise of the signals to be measured comes from the same signal, and extra noise introduced on the two measuring links is irrelevant, so that the processing of a cross-correlation algorithm is applied at the rear end of data processing, the extra noise is suppressed, and the measuring sensitivity is improved.
Fig. 2 shows a delay process of the optical domain signal, and a process of mixing the delayed optical domain signal and the signal to be measured in the optical-electrical mixing module, where a dotted line is the optical domain signal before delay, and a solid line is the delayed optical domain signal.