CN110212987A - RF linear FM signal generation method and device based on frequency spectrum splicing - Google Patents
RF linear FM signal generation method and device based on frequency spectrum splicing Download PDFInfo
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- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
- H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
- H04B10/25137—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion using pulse shaping at the transmitter, e.g. pre-chirping or dispersion supported transmission [DST]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- 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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Abstract
The invention discloses a kind of RF linear FM signal generation methods based on frequency spectrum splicing.Light carrier is converted to frequency in periodically variable by the present inventionNThe multi-carrier optical signal that a light pulse is continuously spliced, then carrier-suppressed SSB modulation is carried out to the multi-carrier optical signal with original radio frequency linear FM signal, actinic FM signal is obtained, finally carries out beat frequency with the frequency-shift signaling of light linear FM signal and light carrier bandwidth can be obtained to expand asNRF linear FM signal again.The invention also discloses a kind of RF linear FM signal generating means based on frequency spectrum splicing.Compared with prior art, the present invention produces the linear FM signal or double chirp linear FM signals that bandwidth greatly improves.
Description
Technical field
The present invention relates to a kind of linear FM signal generation methods more particularly to a kind of based on the linear of microwave photon technology
FM signal generation method and device.
Background technique
Linear FM signal important role in radar detection, it increases arteries and veins while extending radar spectral range
Width is rushed, average emitted power is improved and increases communication distance, traditional pulse radar time width is breached and is mutually restricted with bandwidth
Relationship.The time-bandwidth product (TBWP) of linear FM signal is one of the important parameter of radar detection signal, and big bandwidth can be with
The distance resolution of radar is improved, the velocity resolution of radar can be improved in big time width.Therefore, research is generated with big TBWP
Linear FM signal is of great significance.If generating linear FM signal in the electrical domain, due to the presence of electronic bottleneck, letter is generated
Number center in frequency it is low, instant bandwidth is small, and system structure is also very complicated.With the development of microwave photon technology, electric light is utilized
Modulation technique generates microwave signal because its noise is small, is studied extensively with roomy.Currently, can be divided into according to working principle
Reflection method, microwave photon frequency multiplication method and microwave photon phase modulation method when frequency spectrum shaping-frequency, frequency spectrum splice four kinds of method.Frequency spectrum shaping-frequency
When reflection method, principle is to carry out shaping according to the time domain waveform of desired signal to the spectrum of wide range signal, when then passing through frequency
The shape map of frequency domain to time domain is obtained required waveform by mapping.Microwave photon frequency multiplication method, basic ideas are produced using electrical domain
Raw drive waveform electrooptic modulator inspires different harmonic wave sidebands by electrooptic nonlinear effect, chooses wherein different sidebands
Broadband, high-frequency chirp signal can be obtained in beat frequency, to increase the centre frequency and bandwidth of waveform.Zhang Fangzheng et al. exists
“Photonics-based real-time ultra-high-range-resolution radar with broadband
signal generation and processing”(Zhang,Fangzheng,Qingshui Guo,and Shilong
Pan."Photonics-based real-time ultra-high-range-resolution radar with
broadband signal generation and processing."Scientificreports 7.1(2017):
13848.) linear FM signal is modulated to double parallel Mach in increase on Dare modulator (DPMZM), adjusts bias voltage, only
Retain even-order sideband, be sent into photodetector (PD) beat frequency, obtains the linear FM signal that bandwidth expands 4 times.Microwave photon
Phase modulation method is introduced the phase change of secondary parabola type to microwave signal by using optical instrument, obtains required linear tune
Frequency signal.By carrying out quadratic phase modulation to light carrier, linear FM signal is obtained with light carrier beat frequency again later, but this
Kind method is limited to phase modulation depth, the TBWP of promotion signal, needs to improve modulation depth, when being π for modulation depth,
The time-bandwidth product of the signal of generation is 16.Based on this principle Zhang Yamei et al. in " Photonic generation
oflinear frequency-modulated waveform with improved time-bandwidth product”
(Zhang,Yamei,Xingwei Ye,and Shilong Pan."Photonic generation of linear
frequency-modulated waveform with improved time-bandwidth product."2015
International Topical Meeting on Microwave Photonics (MWP) .IEEE, 2015.) it is proposed in
Quadratic phase modulation is carried out with discrete method, the parabola segmentation that will be modulated, being then amplified to electrooptic modulator can bear
And introduce phase shift be 2 π integral multiples power, using the characteristic of the foldable winding of phase, it is equivalent increase phase-modulation modulation
Depth, so that the time-bandwidth product of generated signal is improved 45 times.Hereafter they are again in " Photonic
generation of linear-frequency-modulated waveforms with improved time-
bandwidth product based on polarization modulation”(Zhang,Yamei,et al."
Photonic generation of linear-frequency-modulated waveforms with improved
time-bandwidth product based on polarization modulation."Journal of Lightwave
Technology 35.10 (2017): 1821-1829.) the sectional parabola modulation method based on light polarization modulator is proposed in, it will
The time-bandwidth product of signal improves 500 times.Frequency spectrum splices method, is that a certain band frequency range is divided into several segments, each small
Online property FM signal is modulated in section, is then stitched together, the bigger linear FM signal of composition bandwidth.Chen Wenjuan et al. exists
“Photonics-based reconfigurable multi-band linearly frequency-modulated
signal generation”(Chen,Wenjuan,et al."Photonics-based reconfigurable multi-
band linearly frequency-modulated signal generation."Optics express 26.25
(2018): 32491-32499. the double frequency combs being misaligned using comb teeth are proposed in), and online property frequency modulation letter is modulated on one group
Number and another group of beat frequency, splicing, generate the linear FM signal of big bandwidth.
The above method is more effective when parabola segments is less, and when segments increase to a certain extent when,
On the one hand very high requirement, signal caused by another aspect are proposed to bandwidth, the sample rate of electric baseband waveform generator
Quality dramatic decrease, time-bandwidth product is difficult to further increase.The signal for how further obtaining big time-bandwidth product becomes
Urgent problem to be solved.
Summary of the invention
The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and to provide a kind of penetrating based on frequency spectrum splicing
Frequency linear FM signal generation method, can greatly improve the bandwidth range of linear FM signal.
The present invention specifically uses following technical scheme to solve above-mentioned technical problem:
Frequency is f by a kind of RF linear FM signal generation method based on frequency spectrum splicingcOptical signal be divided into two
Road；Reference optical signal is obtained after carrying out shift frequency to first via optical signal；Second road optical signal is converted into frequency in the period first
Property variation multi-carrier optical signal, the multi-carrier optical signal in each cycle T is identical by pulsewidth and frequency by frequency difference Δ f is in
N number of light pulse of equal difference progressive relationship is continuously spliced, then with original radio frequency linear FM signal to the multi-carrier light
Signal carries out carrier-suppressed SSB modulation, obtains actinic FM signal, the period of the original radio frequency linear FM signal
Equal to the pulsewidth τ and slope of the light pulseN is the integer greater than 1；Finally use light linear FM signal and reference light
Signal carries out beat frequency, obtains bandwidth and is the RF linear FM signal of N times of original radio frequency linear FM signal bandwidth, and described penetrates
The original frequency of frequency linear FM signal can be adjusted by changing the shift frequency amount of first via optical signal.
Preferably, the second road optical signal is converted into the multi-carrier optical signal using following methods: by the second Lu Guangxin
Number periodic light pulse signal is converted to by photoswitch, is then following for Δ f by light pulse signal input single shift frequency amount
Ring shift frequency module, and the following conditions is enabled to be met:OrWherein T, τ are respectively the smooth arteries and veins
Rush period, the pulsewidth of signal, TLThe time required to taking a round in the loop of the circulating frequency shift module for light, then from circulating frequency shift
Module exports the multi-carrier optical signal.
It is further preferred that the circulating frequency shift module includes:
Optical combiner, for the light pulse signal and the optical signal from optical splitter to be combined；
Double parallel MZ Mach-Zehnder is used by remaining parameter is identical but the radio frequency signals drive of phase by pi/2
In to institute's input optical signal carry out shift frequency, shift frequency amount be the radiofrequency signal frequency, the direction of shift frequency by double parallel Mach once
The bias state of Dare modulator determines；
Optical splitter, for the output signal of double parallel MZ Mach-Zehnder to be divided into two-way, all the way as described
The optical combiner is sent into the output of circulating frequency shift module all the way；
Optical filter is serially connected between optical combiner and optical splitter or connects the output in the circulating frequency shift module
End, for frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencyc+ (N+1) × Δ f and frequencies above
Optical signal be band resistance；
Image intensifer is serially connected between optical combiner and optical splitter.
Following technical scheme can also be obtained based on identical invention thinking:
Frequency is f by a kind of RF linear FM signal generation method based on frequency spectrum splicingcOptical signal be divided into two
Road；First via optical signal is converted into multicarrier of the frequency in periodically variable multi-carrier optical signal, in each period first
Optical signal is identical by pulsewidth and frequency is continuously spliced by frequency difference Δ f in N number of light pulse of equal difference progressive relationship, then
Carrier-suppressed SSB modulation is carried out to the multi-carrier optical signal with original radio frequency linear FM signal, obtains actinic frequency modulation
Signal, the period of the original radio frequency linear FM signal are equal to the pulsewidth τ and slope of the light pulseN be greater than
1 integer；It is f with frequencymRadiofrequency signal to the second road optical signal carry out single sideband modulation, obtain reference optical signal, fm>
N·Δf+f0+ k τ, f0For the original frequency of original radio frequency linear FM signal；Finally believed with light linear FM signal and reference light
Number carry out beat frequency, obtain bandwidth be N times of original radio frequency linear FM signal bandwidth double chirp RF linear FM signals.
Preferably, first via optical signal is converted into the multi-carrier optical signal using following methods: first via light is believed
Number periodic light pulse signal is converted to by photoswitch, is then following for Δ f by light pulse signal input single shift frequency amount
Ring shift frequency module, and the following conditions is enabled to be met:OrWherein T, τ are respectively the light
The period of pulse signal, pulsewidth, TLThe time required to taking a round in the loop of the circulating frequency shift module for light, then moved from circulation
Frequency module exports the multi-carrier optical signal.
It is further preferred that the circulating frequency shift module includes:
Optical combiner, for the light pulse signal and the optical signal from optical splitter to be combined；
Double parallel MZ Mach-Zehnder is used by remaining parameter is identical but the radio frequency signals drive of phase by pi/2
In to institute's input optical signal carry out shift frequency, shift frequency amount be the radiofrequency signal frequency, the direction of shift frequency by double parallel Mach once
The bias state of Dare modulator determines；
Optical splitter, for the output signal of double parallel MZ Mach-Zehnder to be divided into two-way, all the way as described
The optical combiner is sent into the output of circulating frequency shift module all the way；
Optical filter is serially connected between optical combiner and optical splitter or connects the output in the circulating frequency shift module
End, for frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencyc+ (N+1) × Δ f and frequencies above
Optical signal be band resistance；
Image intensifer is serially connected between optical combiner and optical splitter.
A kind of RF linear FM signal generating means based on frequency spectrum splicing, comprising:
Light source is f for generating frequencycOptical signal；
Photo-coupler, for the optical signal of light source output to be divided into two-way；
Light shift frequency module obtains reference optical signal after carrying out shift frequency for the first via optical signal to light source output；
Multicarrier generation module is believed for the second road optical signal to be converted to frequency in periodically variable multi-carrier light
Number, the multi-carrier optical signal in each cycle T is identical by pulsewidth and frequency presses frequency difference Δ f in the N number of of equal difference progressive relationship
Light pulse is continuously spliced；
Carrier-suppressed SSB modulation module, for original radio frequency linear FM signal to the multi-carrier optical signal into
The modulation of row carrier-suppressed SSB obtains actinic FM signal, and the period of the original radio frequency linear FM signal is equal to institute
State the pulsewidth τ and slope of light pulseN is the integer greater than 1；
Photodetector, for carrying out beat frequency to actinic FM signal and reference optical signal, obtaining bandwidth is N times original
The RF linear FM signal of RF linear FM signal bandwidth, and the original frequency of the RF linear FM signal can pass through
The shift frequency amount for changing first via optical signal is adjusted.
Preferably, the multicarrier generation module includes:
Photoswitch, for the second road optical signal to be converted to periodic light pulse signal；
Circulating frequency shift module, the light pulse signal for exporting to photoswitch carry out the circulation that single shift frequency amount is Δ f and move
Frequently, and the multi-carrier optical signal is exported,OrWherein T, τ are respectively the light pulse signal
Period, pulsewidth, TLThe time required to taking a round in the loop of the circulating frequency shift module for light.
It is further preferred that the circulating frequency shift module includes:
Optical combiner, for the light pulse signal and the optical signal from optical splitter to be combined；
Double parallel MZ Mach-Zehnder is used by remaining parameter is identical but the radio frequency signals drive of phase by pi/2
In to institute's input optical signal carry out shift frequency, shift frequency amount be the radiofrequency signal frequency, the direction of shift frequency by double parallel Mach once
The bias state of Dare modulator determines；
Optical splitter, for the output signal of double parallel MZ Mach-Zehnder to be divided into two-way, all the way as described
The optical combiner is sent into the output of circulating frequency shift module all the way；
Optical filter is serially connected between optical combiner and optical splitter or connects the output in the circulating frequency shift module
End, for frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencyc+ (N+1) × Δ f and frequencies above
Optical signal be band resistance；
Image intensifer is serially connected between optical combiner and optical splitter.
It is a kind of based on frequency spectrum splicing RF linear FM signal generating means include:
Light source is f for generating frequencycOptical signal；
Photo-coupler, for the optical signal of light source output to be divided into two-way；
Multicarrier generation module is believed for first via optical signal to be converted to frequency in periodically variable multi-carrier light
Number, the multi-carrier optical signal in each cycle T is identical by pulsewidth and frequency presses frequency difference Δ f in the N number of of equal difference progressive relationship
Light pulse is continuously spliced；
Carrier-suppressed SSB modulation module, for original radio frequency linear FM signal to the multi-carrier optical signal into
The modulation of row carrier-suppressed SSB obtains actinic FM signal, and the period of the original radio frequency linear FM signal is equal to institute
State the pulsewidth τ and slope of light pulseN is the integer greater than 1；
Single sideband modulation module, for being f with frequencymRadiofrequency signal to the second road optical signal carry out single sideband modulation,
Obtain reference optical signal, fm> N Δ f+f0+ k τ, f0For the original frequency of original radio frequency linear FM signal；
Photodetector, for carrying out beat frequency to actinic FM signal and reference optical signal, obtaining bandwidth is N times original
Double chirp RF linear FM signals of RF linear FM signal bandwidth.
Preferably, the multicarrier generation module includes:
Photoswitch, for first via optical signal to be converted to periodic light pulse signal；
Circulating frequency shift module, the light pulse signal for exporting to photoswitch carry out the circulation that single shift frequency amount is Δ f and move
Frequently, and the multi-carrier optical signal is exported,OrWherein T, τ are respectively the light pulse letter
Number period, pulsewidth, TLThe time required to taking a round in the loop of the circulating frequency shift module for light.
It is further preferred that the circulating frequency shift module includes:
Optical combiner, for the light pulse signal and the optical signal from optical splitter to be combined；
Double parallel MZ Mach-Zehnder is used by remaining parameter is identical but the radio frequency signals drive of phase by pi/2
In to institute's input optical signal carry out shift frequency, shift frequency amount be the radiofrequency signal frequency, the direction of shift frequency by double parallel Mach once
The bias state of Dare modulator determines；
Optical splitter, for the output signal of double parallel MZ Mach-Zehnder to be divided into two-way, all the way as described
The optical combiner is sent into the output of circulating frequency shift module all the way；
Optical filter is serially connected between optical combiner and optical splitter or connects the output in the circulating frequency shift module
End, for frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencyc+ (N+1) × Δ f and frequencies above
Optical signal be band resistance；
Image intensifer is serially connected between optical combiner and optical splitter.
Compared with prior art, technical solution of the present invention has the advantages that
One, the present invention breaches conventional method and limits the bandwidth of the signal of generation, and generated radio frequency letter can be improved
Number bandwidth, signal bandwidth is promoted to wide N times of loaded radio frequency signal bands.
Two, the conversion of linear FM signal and double chirp linear FM signals may be implemented in the present apparatus.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of a specific embodiment of RF linear FM signal generating means of the present invention；
Fig. 2 is the multicarrier generation module structural schematic diagram based on circulating frequency shift structure；
Fig. 3 is the multicarrier generation module structural schematic diagram based on outer Semiconductor Lasers structure；
Fig. 4 is generated multi-carrier signal schematic diagram, and τ is the duration of any frequency light carrier, and T is total period；
Fig. 5 is generated linear FM signal；
Frequency relation schematic diagram of the Fig. 6 between actinic FM signal and single sideband modulated signal；
Fig. 7 is the double chirp linear FM signals generated.
Specific embodiment
The bandwidth of RF linear FM signal in order to greatly increase, resolving ideas of the invention are to be converted to light carrier
Frequency is in the multi-carrier optical signal that periodically variable N number of light pulse is continuously spliced, and then uses original radio frequency linear frequency modulation
Signal carries out carrier-suppressed SSB modulation to the multi-carrier optical signal, actinic FM signal is obtained, finally with actinic
The frequency-shift signaling of FM signal and light carrier, which carries out beat frequency, can be obtained the RF linear FM signal that bandwidth expands as N times.
Specifically, being f by frequency the present invention is based on the RF linear FM signal generation method of frequency spectrum splicingcLight
Signal is divided into two-way；Reference optical signal is obtained after carrying out shift frequency to first via optical signal；Second road optical signal is converted to first
Frequency is in periodically variable multi-carrier optical signal, and the multi-carrier optical signal in each cycle T is identical by pulsewidth and frequency is pressed
Frequency difference Δ f is continuously spliced in N number of light pulse of equal difference progressive relationship, then with original radio frequency linear FM signal to institute
It states multi-carrier optical signal and carries out carrier-suppressed SSB modulation, obtain actinic FM signal, the original radio frequency linear frequency modulation
The period of signal is equal to the pulsewidth τ and slope of the light pulseN is the integer greater than 1；Finally believed with light linear frequency modulation
Number and reference optical signal carry out beat frequency, obtain the RF linear frequency modulation letter that bandwidth is N times of original radio frequency linear FM signal bandwidth
Number, and the original frequency of the RF linear FM signal can be adjusted by changing the shift frequency amount of first via optical signal.
For the ease of public understanding, to carry out technical solution of the present invention below by specific embodiment and in conjunction with attached drawing
It is described in detail:
Fig. 1 shows the basic structure of a specific embodiment of RF linear FM signal generating means of the present invention.Such as
Shown in Fig. 1, which includes that laser source, two photo-couplers, light shift frequency module, multicarrier generation module, suppressed carrier are unilateral
Band modulation module, photodetector.The light of laser source output is divided into two-way by first photo-coupler, and light shift frequency module is to upper road
Optical signal obtains reference optical signal after carrying out shift frequency, and lower road optical signal is converted to frequency in periodically change by multicarrier generation module
The multi-carrier optical signal of change, the multi-carrier optical signal in each cycle T is identical by pulsewidth and frequency by frequency difference Δ f is in equal difference
N number of light pulse of progressive relationship is continuously spliced, then carrier-suppressed SSB modulation module original radio frequency linear frequency modulation
Signal carries out carrier-suppressed SSB modulation to the multi-carrier optical signal, obtains actinic FM signal, the original radio frequency
The period of linear FM signal is equal to the pulsewidth τ and slope of the light pulseN is the integer greater than 1；Second optocoupler
Actinic FM signal and reference optical signal are combined into and are converted to electric signal through photodetector afterwards all the way by clutch, that is, realize two
The beat frequency of person obtains the RF linear FM signal that bandwidth is N times of original radio frequency linear FM signal bandwidth, and the radio frequency line
Property FM signal original frequency can by change first via optical signal shift frequency amount be adjusted.
Various structures realization can be used in multicarrier generation module therein, such as based on circulating frequency shift structure or is based on outer note
Enter semiconductor laser structure.Acousto-optic modulator can be used in light shift frequency module or double parallel Mach increases Dare modulator (DPMZM)
Deng realize, in order to improve shift frequency amount, it is preferred to use the mode of DPMZM, the shift frequency range of acousto-optic modulator in MHz magnitude, and
The shift frequency range of DPMZM method is in GHz.
Multicarrier generation module multicarrier generation module based on circulating frequency shift structure includes cascade photoswitch and circulation
Shift frequency module, photoswitch are used to lower road optical signal being converted to periodic light pulse signal；Circulating frequency shift module is used for light
The light pulse signal of switch output carries out single shift frequency amount and is the circulating frequency shift of Δ f, and exports the multi-carrier optical signal,OrWherein T, τ are respectively the period of the light pulse signal, pulsewidth, TLIt is followed for light described
The time required to taking a round in the loop of ring shift frequency module.
The circulating frequency shift module is based on a loop constructed by light shift frequency module, and smooth shift frequency module therein can adopt
With existing various technologies, present invention preferably employs the circulating frequency shift modules realized based on DPMZM, specifically include:
Optical combiner, for the light pulse signal and the optical signal from optical splitter to be combined；
Double parallel MZ Mach-Zehnder is used by remaining parameter is identical but the radio frequency signals drive of phase by pi/2
In to institute's input optical signal carry out shift frequency, shift frequency amount be the radiofrequency signal frequency, the direction of shift frequency by double parallel Mach once
The bias state of Dare modulator determines；
Optical splitter, for the output signal of double parallel MZ Mach-Zehnder to be divided into two-way, all the way as described
The optical combiner is sent into the output of circulating frequency shift module all the way；
Optical filter is serially connected between optical combiner and optical splitter or connects the output in the circulating frequency shift module
End, for frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencyc+ (N+1) × Δ f and frequencies above
Optical signal be band resistance；
Image intensifer is serially connected between optical combiner and optical splitter.
Fig. 2 shows a preferred implementation scheme of multicarrier generation module, and the photoswitch in the present embodiment is by MZM structure
At when MZM only has direct current biasing, output is EMZM=cos φ Ein, control clock signal, make φ 0 withTwo points are handed over
For variation, switching function can be realized, certainly, other existing photoswitches can also be used.After opening photoswitch, frequency fcLight
Signal enters in loop that (input light is), control the Dc bias of DPMZM and two radio frequencies letter of load
Number phase can to light carry out carrier-suppressed SSB (CS-SSB) modulation.The radio frequency letter of the two prevention at radio-frequency port load of DPMZM
Number frequency is identical, and 90 ° of phase phase difference, if road load thereon is cosine signal, lower road load is sinusoidal signal, and the road Ze Shang is defeated
Out are as follows:
Road Dc bias in adjusting, so thatAccording to small signal approximation, get back:
Similarly, the output signal on lower road is obtained:
Third direct current biasing is adjusted again, makes two-way difference phase shift up and downWithThe output of entire DPMZM are as follows:
CS-SSB is thereby realized, is equivalent to and carries out shift frequency processing.
If light is in the loop τ around the time of a circle, in order not to allow light front and the tail portion of light interfere, need
The opening time for controlling photoswitch is also τ.Then after by the n τ time, light fieldIt include a light in loop to guarantee that the power for generating signal is certain
Amplifier (such as erbium-doped fiber amplifier (EDFA) or semiconductor optical amplifier (SOA)) carries out the light loss of every revolution
Compensation.It sets optical filter to for frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencyc+(N+
1) × Δ f and the optical signal of frequencies above are band resistance.The circular time is T=N τ in the loop.After time T, in optical path
Photoswitch will be opened at this time, original optical signal is made to be again introduced into loop there is no signal, it can be seen that the switch of photoswitch
Period is T.Finally obtained multi-carrier optical signal is as shown in Figure 4.
Fig. 3 shows the multicarrier generation module based on outer Semiconductor Lasers structure, the detail of the structure
Existed " Flexible frequency-hopping microwave generation by dynamic by Zhou Pei et al.
control of optically injected semiconductor laser"(Zhou,Pei,et al."Flexible
frequency-hopping microwave generation by dynamic control of optically
Injected semiconductor laser. " IEEE Photonics Journal 8.6 (2016): 1-9.) it is provided in, this
Place repeats no more.
Modulating upper a cycle to multi-carrier optical signal shown in Fig. 4 by carrier-suppressed SSB modulation module is τ's
Linear FM signal, if the signal isBeam is closed with reference optical signal again later, is sent
Enter PD, then obtain output signal:
Wherein, ψ is constant.In order to smoothly splice, k needs specific value:
f0+ Δ f+k the Δ of τ=2 f+f0
In this way, the linear FM signal that we have just obtained the opposite load of bandwidth expands N times of linear FM signal, such as scheme
Shown in 5.
In addition, if light shift frequency module is substituted for single sideband modulation module by us, in the light modulation issued to laser source
One frequency is fm, and fm> N Δ f+f0The radiofrequency signal of+k τ so that the instantaneous frequency of actinic FM signal all fall within it is sharp
Between light source frequency and the frequency of single order sideband, as shown in fig. 6, then with obtained single sideband modulated signal and actinic tune
Frequency signal beat frequency can obtain the radiofrequency signal of two frequencies, i.e., double chirp linear frequency modulations as shown in Figure 7 in synchronization
Signal.
Claims (12)
1. it is a kind of based on frequency spectrum splicing RF linear FM signal generation method, which is characterized in that by frequency be fcOptical signal
It is divided into two-way；Reference optical signal is obtained after carrying out shift frequency to first via optical signal；Second road optical signal is converted into frequency first
In periodically variable multi-carrier optical signal, the multi-carrier optical signal in each cycle T is identical by pulsewidth and frequency presses frequency
Poor Δ f is continuously spliced in N number of light pulse of equal difference progressive relationship, then with original radio frequency linear FM signal to described more
Carrier wave optical signal carries out carrier-suppressed SSB modulation, obtains actinic FM signal, the original radio frequency linear FM signal
Period be equal to the light pulse pulsewidth τ and slopeN is the integer greater than 1；Finally with light linear FM signal and
Reference optical signal carries out beat frequency, obtains the RF linear FM signal that bandwidth is N times of original radio frequency linear FM signal bandwidth, and
The original frequency of the RF linear FM signal can be adjusted by changing the shift frequency amount of first via optical signal.
2. RF linear FM signal generation method as described in claim 1, which is characterized in that use following methods by the second tunnel
Optical signal is converted to the multi-carrier optical signal: the second road optical signal being converted to periodic light pulse by photoswitch and is believed
Number, then light pulse signal input single shift frequency amount is the circulating frequency shift module of Δ f, and the following conditions is enabled to be met:OrWherein T, τ are respectively the period of the light pulse signal, pulsewidth, TLIt is followed for light described
The time required to taking a round in the loop of ring shift frequency module, then the multi-carrier optical signal is exported from circulating frequency shift module.
3. RF linear FM signal generation method as claimed in claim 2, which is characterized in that the circulating frequency shift module packet
It includes:
Optical combiner, for the light pulse signal and the optical signal from optical splitter to be combined；
Double parallel MZ Mach-Zehnder, by remaining parameter is identical but the radio frequency signals drive of phase by pi/2, for pair
Institute's input optical signal carries out shift frequency, and shift frequency amount is the frequency of the radiofrequency signal, and the direction of shift frequency is by double parallel mach zhender
The bias state of modulator determines；
Optical splitter is used as the circulation for the output signal of double parallel MZ Mach-Zehnder to be divided into two-way all the way
The optical combiner is sent into the output of shift frequency module all the way；
Optical filter is serially connected between optical combiner and optical splitter or connects the output end in the circulating frequency shift module,
For frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencycThe light of+(N+1) × Δ f and frequencies above
Signal is band resistance；
Image intensifer is serially connected between optical combiner and optical splitter.
4. it is a kind of based on frequency spectrum splicing RF linear FM signal generation method, which is characterized in that by frequency be fcOptical signal
It is divided into two-way；First via optical signal is converted into frequency in periodically variable multi-carrier optical signal, in each period first
Multi-carrier optical signal is identical by pulsewidth and frequency is continuously spliced by frequency difference Δ f in N number of light pulse of equal difference progressive relationship and
At then carrying out carrier-suppressed SSB modulation to the multi-carrier optical signal with original radio frequency linear FM signal, obtain light
Linear FM signal, the period of the original radio frequency linear FM signal are equal to the pulsewidth τ and slope of the light pulse
N is the integer greater than 1；It is f with frequencymRadiofrequency signal to the second road optical signal carry out single sideband modulation, obtain reference light letter
Number, fm> N Δ f+f0+ k τ, f0For the original frequency of original radio frequency linear FM signal；Finally with light linear FM signal and
Reference optical signal carries out beat frequency, obtains double chirp RF linear frequency modulation that bandwidth is N times of original radio frequency linear FM signal bandwidth
Signal.
5. RF linear FM signal generation method as claimed in claim 4, which is characterized in that use following methods by the first via
Optical signal is converted to the multi-carrier optical signal: first via optical signal being converted to periodic light pulse by photoswitch and is believed
Number, then light pulse signal input single shift frequency amount is the circulating frequency shift module of Δ f, and the following conditions is enabled to be met:OrWherein T, τ are respectively the period of the light pulse signal, pulsewidth, TLIt is light described
The time required to taking a round in the loop of circulating frequency shift module, then the multi-carrier optical signal is exported from circulating frequency shift module.
6. RF linear FM signal generation method as claimed in claim 5, which is characterized in that the circulating frequency shift module packet
It includes:
Optical combiner, for the light pulse signal and the optical signal from optical splitter to be combined；
Double parallel MZ Mach-Zehnder, by remaining parameter is identical but the radio frequency signals drive of phase by pi/2, for pair
Institute's input optical signal carries out shift frequency, and shift frequency amount is the frequency of the radiofrequency signal, and the direction of shift frequency is by double parallel mach zhender
The bias state of modulator determines；
Optical splitter is used as the circulation for the output signal of double parallel MZ Mach-Zehnder to be divided into two-way all the way
The optical combiner is sent into the output of shift frequency module all the way；
Optical filter is serially connected between optical combiner and optical splitter or connects the output end in the circulating frequency shift module,
For frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencycThe light of+(N+1) × Δ f and frequencies above
Signal is band resistance；
Image intensifer is serially connected between optical combiner and optical splitter.
7. a kind of RF linear FM signal generating means based on frequency spectrum splicing characterized by comprising
Light source is f for generating frequencycOptical signal；
Photo-coupler, for the optical signal of light source output to be divided into two-way；
Light shift frequency module obtains reference optical signal after carrying out shift frequency for the first via optical signal to light source output；
Multicarrier generation module, for the second road optical signal to be converted to frequency in periodically variable multi-carrier optical signal, often
Multi-carrier optical signal in one cycle T is identical by pulsewidth and frequency presses N number of light pulse that frequency difference Δ f is in equal difference progressive relationship
Continuously it is spliced；
Carrier-suppressed SSB modulation module, for being carried with original radio frequency linear FM signal to the multi-carrier optical signal
Wave inhibits single sideband modulation, obtains actinic FM signal, and the period of the original radio frequency linear FM signal is equal to the light
The pulsewidth τ and slope of pulseN is the integer greater than 1；
Photodetector, for carrying out beat frequency to actinic FM signal and reference optical signal, obtaining bandwidth is N times of original radio frequency
The RF linear FM signal of linear FM signal bandwidth, and the original frequency of the RF linear FM signal can pass through change
The shift frequency amount of first via optical signal is adjusted.
8. RF linear FM signal generating means as claimed in claim 7, which is characterized in that the multicarrier generation module packet
It includes:
Photoswitch, for the second road optical signal to be converted to periodic light pulse signal；
Circulating frequency shift module, the light pulse signal for exporting to photoswitch carry out the circulating frequency shift that single shift frequency amount is Δ f, and
The multi-carrier optical signal is exported,OrWherein T, τ are respectively the week of the light pulse signal
Phase, pulsewidth, TLThe time required to taking a round in the loop of the circulating frequency shift module for light.
9. RF linear FM signal generating means as claimed in claim 8, which is characterized in that the circulating frequency shift module packet
It includes:
Optical combiner, for the light pulse signal and the optical signal from optical splitter to be combined；
Double parallel MZ Mach-Zehnder, by remaining parameter is identical but the radio frequency signals drive of phase by pi/2, for pair
Institute's input optical signal carries out shift frequency, and shift frequency amount is the frequency of the radiofrequency signal, and the direction of shift frequency is by double parallel mach zhender
The bias state of modulator determines；
Optical splitter is used as the circulation for the output signal of double parallel MZ Mach-Zehnder to be divided into two-way all the way
The optical combiner is sent into the output of shift frequency module all the way；
Optical filter is serially connected between optical combiner and optical splitter or connects the output end in the circulating frequency shift module,
For frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencycThe light of+(N+1) × Δ f and frequencies above
Signal is band resistance；
Image intensifer is serially connected between optical combiner and optical splitter.
10. a kind of RF linear FM signal generating means based on frequency spectrum splicing characterized by comprising
Light source is f for generating frequencycOptical signal；
Photo-coupler, for the optical signal of light source output to be divided into two-way；
Multicarrier generation module, for first via optical signal to be converted to frequency in periodically variable multi-carrier optical signal, often
Multi-carrier optical signal in one cycle T is identical by pulsewidth and frequency presses N number of light pulse that frequency difference Δ f is in equal difference progressive relationship
Continuously it is spliced；
Carrier-suppressed SSB modulation module, for being carried with original radio frequency linear FM signal to the multi-carrier optical signal
Wave inhibits single sideband modulation, obtains actinic FM signal, and the period of the original radio frequency linear FM signal is equal to the light
The pulsewidth τ and slope of pulseN is the integer greater than 1；
Single sideband modulation module, for being f with frequencymRadiofrequency signal to the second road optical signal carry out single sideband modulation, joined
Examine optical signal, fm> N Δ f+f0+ k τ, f0For the original frequency of original radio frequency linear FM signal；
Photodetector, for carrying out beat frequency to actinic FM signal and reference optical signal, obtaining bandwidth is N times of original radio frequency
Double chirp RF linear FM signals of linear FM signal bandwidth.
11. RF linear FM signal generating means as claimed in claim 10, which is characterized in that the multicarrier generation module
Include:
Photoswitch, for first via optical signal to be converted to periodic light pulse signal；
Circulating frequency shift module, the light pulse signal for exporting to photoswitch carry out the circulating frequency shift that single shift frequency amount is Δ f, and
The multi-carrier optical signal is exported,OrWherein T, τ are respectively the week of the light pulse signal
Phase, pulsewidth, TLThe time required to taking a round in the loop of the circulating frequency shift module for light.
12. RF linear FM signal generating means as claimed in claim 11, which is characterized in that the circulating frequency shift module packet
It includes:
Optical combiner, for the light pulse signal and the optical signal from optical splitter to be combined；
Double parallel MZ Mach-Zehnder, by remaining parameter is identical but the radio frequency signals drive of phase by pi/2, for pair
Institute's input optical signal carries out shift frequency, and shift frequency amount is the frequency of the radiofrequency signal, and the direction of shift frequency is by double parallel mach zhender
The bias state of modulator determines；
Optical splitter is used as the circulation for the output signal of double parallel MZ Mach-Zehnder to be divided into two-way all the way
The optical combiner is sent into the output of shift frequency module all the way；
Optical filter is serially connected between optical combiner and optical splitter or connects the output end in the circulating frequency shift module,
For frequency in fc+ Δ f~fc+ N × Δ f optical signal is band logical, is f for frequencycThe light of+(N+1) × Δ f and frequencies above
Signal is band resistance；
Image intensifer is serially connected between optical combiner and optical splitter.
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