CN103516435B - Based on chirp microwave pulse signal generation method and the device of electro-optic external modulation nonlinear effect - Google Patents

Abstract

The invention discloses a kind of chirp microwave pulse signal generation method based on electro-optic external modulation nonlinear effect and device.Under signal modulation pattern, Single wavelength light carrier, in electrooptic modulator, completes the phase-modulation that has larger modulation depth; Phase modulated signal introduces relative phase shift or dislocation through tunable optical time delay module, through time domain switch realize non-linear frequency and warble after region chooses, be input to beat frequency in optical-electrical converter and obtain the adjustable microwave pulse signal of pulse rate, pulsewidth and center carrier frequence.The present invention had both covered the photonic propulsion advantage such as high frequency, large instant bandwidth, and have again generation signal parameter precision high, be easy to tuning, the advantages such as structure is relatively simple, application prospect is very extensive.

Description

Based on chirp microwave pulse signal generation method and the device of electro-optic external modulation nonlinear effect

Technical field

The present invention relates to Microwave photonics, electrooptic modulation technology, especially photon technology type microwave signal produces technology.

Background technology

In modern radar system, the microwave pulse signal of warbling of wide when having larger-bandwidth product is often used to the range accuracy and the range resolution that improve radar.At present, conventional microwave pulse signal of warbling generally produces based on electronic device or device.But along with the development of technology, the microwave pulse signal of warbling utilizing conventional electronics method to produce, due to the restriction of its bandwidth, frequency range, cannot meet the practical application request of people.Therefore, seek the generation scheme of the microwave pulse signal of warbling that can realize more high carrier frequency, more large bandwidth, become study hotspot.

Based on the photoproduction microwave pulse technology of Microwave photonics, because it has the advantage such as large bandwidth, high-quality by extensive concern.At present; utilizing light spectrum reshaping technology and wavelength-time map principle to produce microwave pulse signal of warbling is a kind of novelty, conventional photon type chirp microwave pulse signal generation method: 1) .HaoChiandJianpingYao; " All-fiberchirpedmicrowavepulsegenerationbasedonspectrals hapingandwavelength-to-timeconversion; " IEEETrans.Microw.TheoryTech.; vol.55; no.9,1958-1963,2007; 2) .C.WangandJ.P.Yao, " Chirpedmicrowavepulsegenerationbasedonopticalspectralsha pingandwavelength-to-timemappingusingaSagnac-loopmirrori ncorporatingachirpedfiberBragggrating; " J.Lightw.Technol., vol.27, no.16, these schemes of pp.3336 – 3341, Aug.2009. have fully demonstrated microwave photon technology and have produced the advantage of warbling in microwave pulse signal bandwidth.

It is to be noted: technique scheme has some limitations.First, wavelength-time domain mapping processing accuracy not high, will directly cause generating the parameter of signal not precisely (center carrier frequence e.g., generating signal will reach hundred MHz magnitude control accuracies or deviation all exists larger difficulty) like this; Secondly, the independent, tuning accurately and fast of pulse signal multi-Dimensional parameters is also a major challenge (the operation major part such as free spectrum region, dispersion values size of change filter pass band shape, frequency-domain shaping relies on physical action to complete, and response speed relatively lags behind).Again, above scheme adopts short-pulse light source, frequency comb etc. mostly, and these light source prices are high, volume is large, tuning complexity, are not easy to miniaturization, flexibility.

Summary of the invention

In view of the deficiency of above statement prior art scheme, the present invention aims to provide a kind of photon type of novelty and to warble the generation scheme of (referring to frequency chirp here) microwave pulse signal, under guarantee large bandwidth prerequisite, make it the above deficiency overcoming prior art.

Object of the present invention is realized by following means.

Based on a chirp microwave pulse signal generation method for electro-optic external modulation nonlinear effect, produced the microwave pulse signal of warbling of specific pulse speed, pulsewidth and center carrier frequence by following process:

Under signal modulation pattern, the output light implementing phase of continuous light source is modulated in electro-optic phase modulator by microwave-driven signal; Modulated optical signal constructs the two-way phase modulated signal with relative phase shift through tunable optical time delay module; During using degree modulation type, domain switch builds one-period time domain switching pulse, realizes warbling choosing of region to the non-linear frequency of two-way phase modulated signal; The microwave pulse signal of warbling of specific pulse speed, pulsewidth and center carrier frequence is produced through optical-electrical converter beat frequency.

By adjusting the modulation depth of electro-optic phase modulator, the center carrier frequence of microwave pulse signal of warbling is regulated; The modulation depth of common adjustment electro-optic phase modulator and the relative time delay of tunable optical time delay module between two-way phase modulated signal, the chirping characteristics of microwave pulse signal of warbling is changed; The speed of the recurrent pulse envelope of domain switch and duty ratio during adjustment, pulse rate and the pulsewidth of microwave pulse signal of warbling are able to tuning.

Another object of the present invention provides the microwave pulse signal generation device of warbling implementing said method: by Single wavelength continuous light source, electro-optic phase modulator, tunable optical time delay module, domain switch during intensity modulation type, and optical-electrical converter forms.

Produce a branch of Single wavelength light wave by continuous wave laser source, implement, after signal modulation, to export the phase modulated signal that has larger modulation depth through electro-optic phase modulator.Modulated optical signal is input to tunable optical time delay module, time domain realizes two phase-modulated light signals with relative phase shift.Wherein, tunable optical time delay module is made up of two three-dB couplers, one section of tunable optical delay line and a segment length matched fiber.Then, during using degree modulation type, domain switch builds a switching mode recurrent pulse envelope, and the non-linear frequency being used for choosing two-way modulated optical signal is warbled region, and then produces chirped optical pulse signal.Wherein, intensity modulation type time domain switching function is realized by a Mach-Zehnder modulator.Finally, by optical-electrical converter (photo-detector, photodetector can be referred to as again), chirped optical pulse signal is converted into microwave pulse signal of warbling.Because the center carrier frequence generating signal is determined by the modulation depth under signal modulation to a great extent; Microwave frequency chirping characteristics (frequency modulation type or chirp rate etc.) is determined jointly by the relative phase delay of phase modulation depth and two-way phase-modulated signal; Pulse rate, pulsewidth respectively by time the speed of recurrent pulse envelope of domain switch and duty ratio determine.Based on this, by changing the phase modulation depth of electrooptic modulation module, the relative phase delay of tunable optical time delay module, time the speed of domain switch and duty ratio, accurately can control the pulse rate of generation signal, pulsewidth and center carrier frequence, and then the photonic propulsion realizing the tunable microwave pulse signal of warbling of multi-Dimensional parameters produces.

After above-mentioned design, tool of the present invention has the following advantages: program system configuration is simple, is easy to obtain stable performance; The parameter of pulse signal is substantially decided by electric drive signal and regulates and controls, and thus the precision of pulse signal parameter is high; Do not changing on the basis of system configuration, the tuning fast of microwave pulse signal multi-Dimensional parameters of warbling can realized, and tuning flexible, controlled.

Accompanying drawing illustrates:

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

Fig. 2. microwave pulse signal generating principle of warbling in the inventive method.

Fig. 3. during intensity modulation type, domain switch realizes principle.

Fig. 4. domain switch during cascade connection type.A () speed is the time domain switch of 0.8GHz; B () speed is the time domain switch of 1.6GHz; Domain switch when () speed is the intensity modulator cascade connection type of 0.8GHz c.

Fig. 5. be 0.8GHz at the drive singal of phase-modulator, modulation depth is 24.492, when the relative time delay of tunable optical time delay module is 0.9ns: (a) two-way has the phase place change of the phase-modulated signal of relative phase shift; B frequency modulated light signal that () tunable optical time delay module exports; Domain switch during (c) intensity modulator cascade connection type; What d () beat frequency obtained warble microwave pulse signal.

Embodiment

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

As shown in Figure 1, realize the device of the inventive method by Single wavelength type continuous light source 10, electro-optic phase modulator 20, tunable optical time delay module 30, domain switch 40 during intensity modulation type, optical-electrical converter 50 is formed.Fig. 2 gives the general principle that this device produces microwave signal of warbling.

It is f that Single wavelength type continuous light source 10 produces a branch of frequency _ccontinuous light wave, its light field can be described as:

E ₁(t)＝E ₀exp(j2πf _ct)(1)

Wherein, E ₀represent light field amplitude.Light signal is input to electro-optic phase modulator 20.In phase-modulator, (its frequency is f to the additional drive singal one having a relatively high power by ₁) signal modulation is implemented to light signal, the phase modulation-type light signal obtained is:

E ₂(t)＝E ₀exp[j2πf _ct+jβcos(2πf ₁t)](2)

Wherein, β represents modulation depth.

Then, tunable optical time delay module 30(is utilized to be made up of two three-dB couplers, one section of tunable optical delay line and a segment length matched fiber), time domain constructs the two paths of signals (phase-modulated light signal and self delay signal) with relative phase shift, and the light field after superposition can be described as by mathematic(al) representation:

$\begin{array}{c}{E}_3\left(t\right)=\frac{1}{2}{E}_0\left\{\exp \right[j2\mathrm{\π}{f}_{c}t+\mathrm{j\β}\cos \left(2\mathrm{\π}{f}_{1}t\right)]\\ +\exp [j2\mathrm{\π}{f}_c(t+\mathrm{\τ})+\mathrm{j\β}\cos \left(2\mathrm{\π}{f}_1(t+\mathrm{\τ})\right)]\}\end{array}---\left(3\right)$

Wherein, τ is the delay inequality that tunable optical delay line 30 is introduced between two ways of optical signals.Therefore, the relative phase shift amount between phase-modulated light signal and self delay signal can be controlled by the delay inequality of tuning two paths of signals.

Then, when the modulation signal that tunable optical time delay module 30 exports being input to intensity modulation type in domain switch 40, (its frequency is f to apply drive singal two ₂) in time domain, realize non-linear frequency to warble choosing of region.Here, drive singal one and drive singal two are phase association (phase-correlated) or homology.During intensity modulation type, the function of domain switch 40 has been come by a Mach-Zehnder modulator (MZM), and it realizes principle as shown in Figure 3.A 3V is applied at MZM _π/ 2(wherein, V _πhalf-wave voltage for MZM) bias voltage; Simultaneously at the prevention at radio-frequency port of MZM, inputting a maximum amplitude is V _π/ 2 microwave signals, can obtain the switching pulse that a speed is identical with added drive singal two, and its power delivery function can be expressed as:

$H\left(t\right)=\frac{1}{2}\cos [\frac{\mathrm{\π}}{2}\cos (2\mathrm{\π}{f}_{2}t+\mathrm{\θ})+\frac{3\mathrm{\π}}{2}]+\frac{1}{2}---\left(4\right)$

Wherein, θ is the initial phase of drive singal two.From formula (4): when can be adjusted by the initial phase changing additional drive singal, domain switch chooses interval.Meanwhile, as shown in Figure 4, by the multiple MZM modulator of cascade, and the drive singal of different frequency is applied, the control of the different duty of domain switch when can realize.

Finally, by optical-electrical converter 50, complete the conversion of light signal to the signal of telecommunication, produce microwave pulse signal of warbling:

Wherein, for the response coefficient (Responsibility) of optical-electrical converter.

Description based on formula (5) can be found out: modulation depth β and tunable optical time delay τ determines the modulation characteristics of signal jointly, and generates the pulse rate of microwave pulse signal, pulsewidth and periodically time domain switching pulse is consistent.So, by regulating the modulation depth β of electro-optic phase modulator, can realize generating the tuning of microwave pulse signal center carrier frequency of warbling; The modulation depth of common adjustment electric light phase modulation module and the relative time delay of tunable optical time delay module two-way, the chirping characteristics of microwave pulse signal of warbling can be changed; The speed of regulating cycle time domain switching pulse and duty ratio, can realize the warble pulse rate of microwave pulse signal and the tuning of pulsewidth.

Fig. 5 gives the implementation procedure producing microwave pulse signal of warbling based on the inventive method and device.The frequency of the drive singal one of setting phase-modulator is 0.8GHz, and modulation depth is 24.492; The relative time delay that tunable optical time delay module is introduced is 0.9ns; During two intensity modulated sexual types of cascade, the driving signal frequency of domain switch (MZM) is respectively 0.8GHz and 1.6GHz.Fig. 5 (a) gives phase-modulated signal after tunable optical time delay module 30 time delay, two paths of signals relative phase variation relation; After tunable optical time delay module 30 output port staggered superposition, the change of light signal relative amplitude is as shown in Fig. 5 (b); During using degree modulation type, domain switch 40 [its transfer function is as Suo Shi Fig. 5 (c)] is chosen non-linear frequency and is warbled behind region, modulation signal is input in optical-electrical converter, finally creating center carrier frequence is 28GHz, pulse rate is 0.8GHz, pulsewidth is the microwave pulse signal of warbling of 0.5ns, as shown in Fig. 5 (d).

Comprehensive above statement, the present invention has following feature.1). adopt electro-optic external modulation nonlinear effect to produce microwave pulse signal of warbling, without the need to frequency spectrum shaping and wavelength-time map, generate signal parameter precision high; 2). by jointly controlling modulation depth outside phase-modulator, the relative time delay of tunable optical time delay module and the speed of switch function and duty ratio, can realize generating the tuning flexibly of the pulse rate of microwave pulse signal, pulsewidth and center carrier frequence of warbling.

Above stated be only the preferred embodiment of the present invention, it should be pointed out that under the prerequisite not departing from the inventive method and core apparatus essence, can make within some changes and polishing also should be included in protection scope of the present invention in reality is implemented.

Claims (2)

1., based on a chirp microwave pulse signal generation method for electro-optic external modulation nonlinear effect, produced the microwave pulse signal of warbling of specific pulse speed, pulsewidth and center carrier frequence by following process:

Under signal modulation pattern, the output light implementing phase of continuous light source is modulated in electro-optic phase modulator by microwave-driven signal; Modulated optical signal constructs the two-way phase modulated signal with relative phase shift through tunable optical time delay module; During using degree modulation type, domain switch builds one-period time domain switching pulse, realizes warbling choosing of region to the non-linear frequency of two-way phase modulated signal; The microwave pulse signal of warbling of specific pulse speed, pulsewidth and center carrier frequence is produced through optical-electrical converter beat frequency; The modulation depth of adjustment electro-optic phase modulator, the center carrier frequence of microwave pulse signal of warbling is changed; In the relative time delay that the modulation depth of common adjustment electro-optic phase modulator and tunable optical time delay module are introduced between two-way phase modulated signal, the chirping characteristics of microwave pulse signal of warbling is changed; The speed of the recurrent pulse envelope of domain switch and duty ratio during adjustment, pulse rate and the pulsewidth of microwave pulse signal of warbling are able to tuning.

2. realize the microwave pulse signal generation device of warbling of claim 1 method, it is characterized in that, by Single wavelength continuous light source, electro-optic phase modulator, tunable optical time delay module, domain switch during intensity modulation type, optical-electrical converter forms.