CN101977086A - Photon type digital microwave frequency measuring method and device adopting phase-shift comb filtering array - Google Patents

Abstract

The invention discloses photon type digital microwave frequency measuring method and device adopting a phase-shift comb filtering array, which is characterized in that a microwave signal to be measured is loaded to a continuous laser source to generate a single optical side band and then input into the phase-shift comb filtering array under the modulation of a carrier wave restrain type single side band; the filtering array comprises N parallel comb filtering responses; free frequency spectrum regions are FSR (Feedback Shift Register), and the relative phase shift amount of the adjacent comb filtering responses is Pi/N; and the N comb filtering responses and the output optical power of a reference arm are detected, compared and judged to obtain the frequency measuring result of N-bit digital coding, and the frequency measuring range and the resolution ratio are respectively FSR and FSR/(2N). Meanwhile, the invention provides a specific device for establishing the phase-shift comb filtering array by utilizing a single high-birefringence component. The method and the device have the advantages of a photon type technology and can be easily fused and be compatible with various digital receiving processing equipment, and the application prospects are extremely wide.

Description

Adopt the photon type digital microwave frequency measuring method and the device of phase shift comb filtering array

Technical field

The present invention relates to Microwave Measurement, microwave photon, light filtering field, especially photon technology type digital Frequency Measuring technology.

Background technology

In microwave engineering and application, measuring technique at microwave signal or system is most important, relate to a plurality of parameters such as frequency, phase place, amplitude, modulation classification, arrival direction, its medium frequency is subjected to extensive concern as the parameter of reflected signal time-varying characteristics with standing in the breach.At present, the technology path of microwave frequency measurement mainly contains two kinds of electron type technology and photon type technology.The electron type technology has advantage through long-term development on resolution and stability; Yet the photon type technology of learning based on microwave photon is having remarkable advantages aspect the instantaneous performance in broadband, low-loss, the anti-electromagnetic interference, especially current microwave frequency band more and more higher (up to hundreds of GHz) to be measured.

Thereby, photon type microwave frequency measurement scheme becomes the research focus, with luminous power type of detection scheme (its significant advantage is the photodetector that only needs low speed) is representative, such as the scheme that adopts the optical channel device, adopt optical comb filter scheme, adopt fiber grating scheme, adopt the scheme of light territory mixing etc.: 1).F.A.Volkening, " Photonic channelized RF receiver employing dense wavelength division multiplexing, " USA Patent 7245833B1, Jul.2007; 2).H.Chi, X.Zou, and J.Yao, " An approach to the measurement of microwave frequency based on optical power monitoring; " IEEE Photonics Technology Letters, vol.20, no.14, pp.1249-1251,2008; 3).Z.Li, B.Yang, H.Chi, X.Zhang, S.Zheng, and X.Jin, " Photonic instantaneous measurement of microwave frequency using fiber Bragg grating, " Optics Communications, vol.283, no.3, pp.396-399.2010. 4) .L.A.Bui, M.D.Pelusi, T.D.Vo, N.Sarkhosh, H.Emami, B.J.Eggleton, and A.Mitchell, " Instantaneous frequency measurement system using optical mixing in highly nonlinear fiber; " Optics Express, vol.17, no.25, pp.22983-22991, Dec.2009.These schemes have demonstrated fully the advantage of photon type technology on the instantaneous frequency measurement bandwidth.

It is to be noted: the frequency measurement output result of above-mentioned all multi-schemes is an analog signal, just simulated microwave frequency measurement.And current digitlization frequency measurement output or digitlization receiver have become a kind of main flow trend: people are acquired information from the digitalized data of frequency measurement output directly, need not extra high-speed AD converter; Be easy to and more prevalent Digital Signal Processing/analysis software and module compatibility, be convenient to further analyze and handle; In addition, digitlization frequency measurement dateout is convenient to longer-term storage.Although existing photon type scheme has been reported digital Frequency Measuring output (such as Peng Yue, Zhang Hongming, Yao Minyu, the design and analysis of wideband digital frequency measuring method " light pulse owe to sample " photoelectric project, vol.35, no.3, pp.68-72,2008.); But it need introduce extra analog to digital converter and Multiple Signal Classification algorithm could obtain numeral output, rather than directly obtains digital coding output, process slightly complicated.

For realizing simple and easy photon type and digitlization microwave frequency measurement approach simultaneously, directly obtain digitally coded frequency measurement output, the present invention has announced a kind of frequency measuring method and device of novelty.

Summary of the invention

In view of the existing program of above statement in the deficiency aspect the Direct Digital frequency measurement, the present invention aims to provide a kind of photon type digital microwave frequency measuring method, thereby makes the compatibility and the advantage of flexibility of its advantage such as the instantaneous performance in broadband that have both the photon type technology, digitlization output.

The present invention also aims to provides core apparatus for the enforcement of above method.

Purpose of the present invention realizes by following means.

Adopt the photon type digital microwave frequency measuring method of phase shift comb filtering array, comprise the checkout equipment of forming by continuous light source, carrier suppressed type single-side band modulation module, phase shift comb filtering array, reference arm, optical detection module, contrast and judging module; Described phase shift comb filtering array is made of N comb filtering response, and each comb filtering response shape unanimity and free spectrum region all are FSR, and the relative phase difference of adjacent two comb filterings response is π/N, and N is a positive integer; Microwave signal to be measured generates single single order optical sideband through carrier suppressed type single-side band modulation module loading to continuous light source, be input to again and carry out the parallel filtering processing in phase shift comb filtering array and the reference arm, obtain digitlization frequency measurement result through optical detection module, contrast and judging module then: the output result is the digital coding of N bit, and frequency measurement scope and frequency measurement resolution are respectively FSR and FSR/ (2N).

Practical implementation is: microwave signal to be measured is carried out external modulation through carrier suppressed type single-side band modulation module to the output light signal of LASER Light Source, generates single single order optical sideband; This optical sideband be coupled into simultaneously in the phase shift comb filtering array in a plurality of parallel comb filterings responses and reference arm in.The core of the inventive method is to adopt phase shift comb filtering array, and it is made of N parallel comb filtering response, i (1≤i≤N) individual filter response is expressed as follows:

$F_i\left(f\right)=\frac{1}{2}[1+\sin (\frac{2\mathrm{\πf}}{\mathrm{FSR}}+{\mathrm{\θ}}_i)]$

Or $F_i\left(f\right)=\frac{1}{2}[1+\cos (\frac{2\mathrm{\πf}}{\mathrm{FSR}}+{\mathrm{\θ}}_i)],1\≤i\≤N---\left(1\right)$

Wherein f is light frequency (unit is Hz).Here, all comb filtering responses have identical free spectrum region FSR (unit is Hz), but each comb filtering response has a different initial phase-shift value θ simultaneously _i=(i-1) π/N (is to have a relative phase shift amount π/N) between adjacent two comb filterings response, thereby constitutes phase shift comb filtering array.

After the filtering of phase shift comb filtering response array, the microwave frequency information translation becomes luminous power information; In the optical detection module, adopt photo-detector in parallel to detect the Output optical power of reference arm and the response of each comb filtering, in contrast and judging module, compare then, obtain (the luminous power ratio function R that the individual comb filtering of 1≤i≤N) responds corresponding to i _i(f _m):

$R_i\left(f_m\right)=\frac{1}{2}[1+\sin (\frac{2\mathrm{\π}{f}_m}{\mathrm{FSR}}+{\mathrm{\θ}}_i)]$

Or $R_i\left(f_m\right)=\frac{1}{2}[1+\cos (\frac{2\mathrm{\π}{f}_m}{\mathrm{FSR}}+{\mathrm{\θ}}_i)],1\≤i\≤N---\left(2\right)$

F wherein _mBe microwave frequency to be measured (unit is Hz).In contrast and judging module, N luminous power adjudicated than value function, thereby obtain digitally coded frequency measurement result equally: frequency measurement is output as N digital bit coding, and the frequency measurement scope is whole FSR, and frequency measurement resolution is FSR/ (2N).

For realizing the foregoing invention method, core is phase shift comb filtering array, and the present invention has proposed a kind of concrete device for carrying out said for it: phase shift comb filtering array connects constituting of a plurality of parallel connection type Polarization Controllers and analyzer by single high-double refraction element.High-double refraction element provides identical free spectrum region for a plurality of comb filtering responses; And Polarization Controller in the combination in parallel and analyzer are a plurality of comb filtering response introducing relative phase shift amounts.

Through after the above-mentioned design, the present invention has following advantage: adopt phase shift comb filtering array, both realized not having fuzzy frequency measurement in whole FSR zone with the photon type technology, have characteristics such as big instant bandwidth and strong anti-interference ability; Simultaneously, realize digitally coded frequency measurement result output again, need not extra analog-digital conversion process, can be directly and Digital Signal Processing software and module compatibility, and be convenient to longer-term storage.

Description of drawings:

Fig. 1. the system block diagram of the inventive method.

Fig. 2. the comb filtering response and the light carrier position view of phase shift comb filtering array.

Fig. 3. the digital coding principle of microwave frequency measurement in the inventive method.

Fig. 4. adopt a high-double refraction element to make up phase shift comb filtering array in the device for carrying out said.

Embodiment

Below in conjunction with accompanying drawing enforcement of the present invention is further described.

As shown in Figure 1, the device of realizing the inventive method is by continuous laser source 10, carrier suppressed type single-side band modulation module 20, and optical coupler 30, phase shift comb filtering array 40, reference arm 50, optical detection module 60, contrast and judging module 70 constitute.

From LASER Light Source 10, its output light incoming carrier inhibition type single-side band modulation module 20, this module is linked in sequence by an electrooptic modulator (intensity modulator or phase-modulator) and a band pass filter and forms; (frequency is f to microwave signal to be measured _m) in electrooptic modulator, the output light signal is carried out external modulation, behind band pass filter, only obtain single single order optical sideband then.This single optical sideband is injected in phase shift comb filtering array 40 and the reference arm 50 simultaneously through coupler 30.

Phase shift comb filtering response array 40 constitutes by the individual comb filtering response of N (N is a positive integer) is in parallel, i (1≤i≤N) individual filter response can be expressed as on mathematics:

$F_i\left(f\right)=\frac{1}{2}[1+\sin (\frac{2\mathrm{\πf}}{\mathrm{FSR}}+{\mathrm{\θ}}_i)]$

Or $F_i\left(f\right)=\frac{1}{2}[1+\cos (\frac{2\mathrm{\πf}}{\mathrm{FSR}}+{\mathrm{\θ}}_i)],1\≤i\≤N---\left(3\right)$

Wherein f (unit is Hz) is a light frequency, and FSR (unit is Hz) is the free spectrum region of comb filtering response, θ _iInitial phase-shift phase for each comb filtering response.Here, all comb filtering responses have on all four FSR, and they carry a different initial phase-shift phase θ separately simultaneously _i=(i-1) π/N, as described in Figure 2.Be not difficult to find out that by formula (3) and Fig. 1,2 the relative phase shift amount between adjacent two comb filterings response is π/N, so constitute phase shift comb filtering array.

Output frequency f when LASER Light Source 10 ₀(see figure 2) when aiming at the zero phase of first comb filtering response, after phase shift comb filtering array 40 Filtering Processing and optical detection module 60 (forming) detection by a series of low speed photo-detectors, i (1≤i≤N) luminous power function individual filter response correspondence and frequency dependence is:

$P_i\left(f_m\right)=\frac{1}{2}{P}_0[1+\sin (\frac{2\mathrm{\π}{f}_m}{\mathrm{FSR}}+{\mathrm{\θ}}_i)]$

Or $P_i\left(f_m\right)=\frac{1}{2}{P}_0[1+\cos (\frac{2\mathrm{\π}{f}_m}{\mathrm{FSR}}+{\mathrm{\θ}}_i)],1\≤i\≤N---\left(4\right)$

F wherein _mBe microwave frequency to be measured (unit is Hz), P ₀Be reference arm light power.In contrast and judging module 70, utilize divider that the Output optical power of each comb filtering response and the luminous power of reference arm are contrasted, the i of acquisition (the individual luminous power ratio function R of 1≤i≤N) _i(f _m) as follows:

$R_i\left(f_m\right)=\frac{1}{2}[1+\sin (\frac{2\mathrm{\π}{f}_m}{\mathrm{FSR}}+{\mathrm{\θ}}_i)]$

Or $R_i\left(f_m\right)=\frac{1}{2}[1+\cos (\frac{2\mathrm{\π}{f}_m}{\mathrm{FSR}}+{\mathrm{\θ}}_i)],1\≤i\≤N---\left(5\right)$

These luminous powers can be eliminated the negative effect of the microwave power of reception to microwave frequency measurement result than value function.The luminous power of describing based on formula (5) utilizes decision device (is decision threshold with 0.5) to carry out digital coding than value function in contrast and judging module 70.Its process is as follows: obtain a series of luminous powers of describing by formula (5) than value function after, adjudicate based on threshold value; Luminous power ratio is digital " 0 " less than 0.5 judgement, and luminous power ratio is numeral " 1 " greater than 0.5 judgement, thereby obtains the frequency measurement output of N digital bit coding, and whole free spectrum region FSR is divided into 2N zone simultaneously.Thereby the frequency measurement scope is whole FSR, and frequency measurement resolution is FSR/ (2N); Adjust the FSR and the number N in parallel of comb filtering response, corresponding frequency measurement scope FSR and frequency-measurement accuracy FSR/ (2N) can adjust flexibly; When the N value was big, the inventive method can obtain very high frequency measurement resolution.

Being example with N=5 is illustrated the principle of the digitlization frequency measurement process of the inventive method.As described in Figure 3: whole FSR is divided into 10 intervals, frequency measurement resolution is FSR/10, and frequency measurement is output as 5 digital bits codings (digital coding in 10 intervals is respectively " 11111,11110,11100,11000,10000,0000,00001,00011,00111,01111 ").

In addition, the core of the inventive method is to adopt phase shift comb filtering array 40, has provided a kind of concrete device of implementing phase shift comb filtering array 40 here.As described in Figure 4, this concrete device is by a Polarization Controller 401, high-double refraction element 402, a coupler 403 and a plurality of by Polarization Controller 404 _iWith analyzer 405 _i(1≤i≤N) constitutes.Single optical sideband by coupler 30 outputs is polarized controller 401 adjustment, to incide in the high-double refraction element with the polarization direction at the fast axle of high-double refraction element (or slow axis) angle at 45, introduces relative time delay (inverse in relative time delay is FSR).Be divided into the N road from the light signal of high-double refraction element 402 outgoing through coupler 403, be injected into simultaneously by Polarization Controller 404 _iThe i that forms with analyzer 405i is (in the individual parallel branch of 1≤i≤N); In each parallel branch, respectively by Polarization Controller 404 _iWith analyzer 405 _iAdjust the polarization state direction and the initial phase that inject light signal, thereby obtain a plurality of parallel phase shift comb filtering responses: free spectrum region is FSR, initial phase-shift phase is (i-1) π/N, wherein 1≤i≤N.This core apparatus can be used for implementing the digital microwave frequency measurement of the inventive method.

Comprehensive above statement, the present invention has following feature.1). adopt the frequency measurement of phase shift comb filtering array implement microwave, on the basis of realizing the frequency measurement of photon technology type, the digital coding output that the frequency measurement result directly is need not extra analog-to-digital conversion and coding device; 2). frequency measurement scope and frequency measurement resolution are respectively FSR, FSR/ (2N), and FSR that can be by adjusting the comb filtering array and filter response number N are in addition tuning flexibly to them.

Above what state only is preferred implementation of the present invention, should be pointed out that under the prerequisite that does not break away from the inventive method and core apparatus essence, can make some changes and polishing also should be included in protection scope of the present invention in reality is implemented.

Claims (2)

1. adopt the photon type digital microwave frequency measuring method of phase shift comb filtering array, it is characterized in that, comprise the checkout equipment of forming by continuous light source, carrier suppressed type single-side band modulation module, phase shift comb filtering array, reference arm, optical detection module, contrast and judging module; Described phase shift comb filtering array is made of N comb filtering response, and each comb filtering response shape unanimity and free spectrum region all are FSR, and the relative phase difference of adjacent two comb filterings response is π/N, and N is a positive integer; Microwave signal to be measured generates single single order optical sideband through carrier suppressed type single-side band modulation module loading to continuous light source, be input to again and carry out the parallel filtering processing in phase shift comb filtering array and the reference arm, obtain digitlization frequency measurement result through optical detection module, contrast and judging module then: the output result is the digital coding of N bit, and frequency measurement scope and frequency measurement resolution are respectively FSR and FSR/ (2N).

2. realize the photon type digital microwave frequency measuring device of the described method of claim 1, it is characterized in that, form successively by continuous light source, carrier suppressed type single-side band modulation module, phase shift comb filtering array, reference arm, optical detection module, contrast and judging module; Described phase shift comb filtering array apparatus connects constituting of a plurality of parallel connection type Polarization Controllers and analyzer by single high-double refraction element.

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