CN104079269B - Microwave VCO directly modulation High Linear FM signal generation circuit - Google Patents

Abstract

A kind of microwave VCO directly modulation High Linear FM signal generation circuit that the present invention proposes, it is desirable to provide a kind of there is second order above sweep linearity precision, sweep rate is unrestricted, the mixing that can suppress to intersect causes the Microwave Linear FM signal generation circuit of frequency modulated continuous wave radar intermediate frequency spurious signal.The present invention is achieved through the following technical solutions: the periodic pulse signal being used for triggering swept-frequency signal of input is shaped as pulsewidth equal to the pulse signal of frequency sweep time in the cycle by monostable pulses shaping circuit, non-linear oblique decline sawtooth voltage signal, the DC offset voltage V being superimposed upon is produced through C-R peaker₀On, forming the frequency sweep control voltage signal that the non-linear VT-frequency characteristic with microwave VCO (4) mutually compensates for, the frequency of oscillation controlling microwave VCO changes linearly over time.The pulse signal that shaping produces controls microwave switch and gates microwave VCO output, the interference that radar is worked by the suppression intermediate frequency spurious signal that closely strong echo produces.

Description

Microwave VCO directly modulation High Linear FM signal generation circuit

Technical field

The present invention relates to one and be mainly used in the microwave voltage controlled oscillator (VCO) of Continuous Wave with frequency modulation (FMCW) radar directly Modulation High Linear FM signal generation circuit, the microwave signal frequency of output periodicity linear frequency sweep over time, in each week In the frequency sweep time of phase, frequency-time characteristic curve has the above linear precision of second order.

Background technology

Linear frequency modulation (LFM) signal is to obtain big Timed automata by linear frequency modulation, and also commonly referred to as Chirp believes Number, it is to study the earliest and most widely used a kind of pulse compression signal, radar generally uses wide bandwidth when having big take advantage of Long-pending LFM signal increases detection range while ensureing high-resolution.FMCW(Frequency Modulated Continuous Wave) Continuous Wave with frequency modulation radar has it for a long time, and its major advantage has that radiant power is little, ranging and range rate is smart Degree is high, equipment is relatively easy, be easily achieved solid state design, have good low probability of intercept (LPI) performance etc..FMCW system Radar be mainly used in range finding and test the speed, such as continuous wave altimeter, range radar, automobile collision avoidance radar etc..Continuous Wave with frequency modulation (FMCW) radar emission linear frequency modulation continuous wave signal, and target echo is carried out mixing generation intermediate-freuqncy signal with launching signal. Due to the space delay of echo-signal, IF signal frequency will be proportional to echo delay time, i.e. the electromagnetic wave round trip propagation time, Thus by IF signal processing is obtained IF-FRE, it is achieved to object ranging.

In order to reach high range accuracy, launch signal and must possess high sweep linearity.Linear chirp master at present Frequency synthesizer to be passed through produces or microwave voltage controlled oscillator (VCO) directly modulation produces, and the former can realize good linear Degree, but attainable sweep rate is relatively low, and swept bandwidth is the narrowest, and circuit is complicated, and cost is high.Microwave VCO directly modulation does not has Having sweep rate to limit, swept bandwidth is also limited only in the maximum tuning bandwidth of VCO, low cost, but sweep linearity is poor, and one As be unsatisfactory for requirement, it is necessary to use linear compensation measure improve the linearity.Conventional linear compensation measure includes that open loop is mended Repaying and closed loop compensation, the open-loop compensation linearity can reach about 5%, it is impossible to meets precision distance measurement requirement.Closed loop compensation circuit Higher line degree can be realized, but circuit realiration is complicated, it is generally required to use Digital Signal Processing, relatively costly, also it is difficult to simultaneously The high sweep rate realized and the bandwidth that exposes thoroughly.

Summary of the invention

It is an object of the invention to the weak point existed for prior art, it is provided that a kind of circuit is simple and reliable, low cost Honest and clean, debugging amount is few, sweep rate is unrestricted, with roomy, there is higher line precision and can suppress to intersect what mixing caused The Microwave Linear FM signal generation circuit of fmcw radar intermediate frequency spurious signal.

For reaching object above, the present invention proposes a kind of microwave VCO directly modulation High Linear FM signal generation circuit, bag Containing monostable pulses shaping circuit 1, C-R peaker 2, biasing resistor 3, microwave voltage controlled oscillator VCO4 and microwave switch 5, its It is characterised by: monostable pulses shaping circuit 1 will input periodic pulse signal, is shaped as pulsewidth and sweeps equal to an intraperiod line Frequently the pulse signal of time, this pulse signal is divided into two-way, and a road produces non-linear oblique decline sawtooth waveforms through C-R peaker 2 Voltage signal, this voltage signal is superimposed upon from external dc voltage source via biasing resistor R₃It is incorporated into C-R peaker 2 to export The DC offset voltage V of end₀On, form frequency sweep and control voltage signal, act on the tuning tip of microwave VCO directly to microwave VCO Carrying out frequency modulation(PFM), frequency sweep control voltage signal mutually compensates for the non-linear VT-frequency characteristic of microwave VCO 4, controls The frequency of oscillation of microwave VCO changes linearly over time, produces linear FM signal output, and is fed to microwave switch input, Microwave Linear FM signal is exported after microwave switch gates；Another road is added to microwave switch and controls end, controls microwave switch Break-make, the Microwave Linear FM signal of gating linear frequency sweep phase, and turn off the microwave signal of frequency sweep resting stage, with suppression closely The interference that radar is worked by the intermediate frequency spurious signal that strong echo produces.

The present invention has the advantages that compared to prior art

The present invention uses simple analog circuit to produce non-linear oblique decline zig-zag, and microwave VCO is carried out directly modulation, Second order above sweep linearity precision can be realized.The present invention uses shaping pulse and peaker to realize non-linear oblique decline sawtooth waveforms Scanning voltage waveform, is directly modulated microwave VCO producing linear FM signal output, by non-linear oblique decline sawtooth waveforms Scanning voltage waveform VT non-linear to microwave VCO-frequency characteristic open-loop compensation improves sweep linearity precision.For at present Conventional variod tuning microwave VCO, except to the R in monostable pulses shaping circuit_t、C_tWith electricity in C-R peaker Resistance R₁、R₂、R₃And electric capacity C₁Component value be designed and adjust outside, it is not necessary to the tuning characteristic of microwave VCO is carried out internal benefit Repay design or the outside VT-frequency characteristic of microwave VCO is carried out linear compensation, i.e. can reach second order above frequency sweep line Property degree, thus the non-linear range error brought of frequency sweep can be substantially reduced when fmcw radar is applied.

Sweep rate is unrestricted, scanning strip is roomy.The present invention uses C-R peaker 2 to produce non-linear oblique decline sawtooth Wave voltage signal carries out direct frequency modulated and produces swept-frequency signal, by suitable circuit parameter design, Ke Yi microwave VCO Non-linear oblique decline sawtooth voltage waveform and the non-linear VT-frequency of VCO is realized in the whole tuning bandwidth of microwave VCO Characteristic mutually compensates for, and is therefore different from conventional microwave VCO swept signal generator, and sweep linearity of the present invention does not increases with bandwidth And deteriorate, such that it is able to realize big swept bandwidth (being limited solely by the tuning bandwidth of microwave VCO).Meanwhile, close compared to various Ring feedback compensation or digitized produce the sweep linearity technology such as modulation waveform, and the present invention is to use the direct microwave of open-loop compensation VCO modulates, and modulation waveform produces and do not adjusted time restriction by Digital processing device speed and closed loop, and therefore sweep rate is the most limited In the performance of microwave VCO, therefore, it is possible to realize faster sweep rate.The above advantage of the present invention so that set at fmcw radar The tuning bandwidth that can make full use of microwave VCO on meter improves detection performance and range accuracy.

The present invention use the pulse signal that monostable pulses shaping circuit produces control microwave switch microwave VCO is exported into Row gating, it is achieved frequency sweep closes microwave VCO signal output function during stopping.As self-mixing formula fmcw radar transmitter Time, this function can eliminate closely echo-signal intersection mixing effect, and suppression intersection is mixed the intermediate frequency spurious signal caused, and then The interference that radar is worked by the suppression fmcw radar intermediate frequency spurious signal that closely strong echo produces.Stopped by appropriately designed frequency sweep Only phase time span, can be under snr loss very minor premise, and minimizing closely strong echo-signal intersection is mixed in producing The most spuious interference to target acquisition, is favorably improved radar detection signal interference ratio.

Circuit of the present invention is simple and reliable, with low cost, it is easy to accomplish.The present invention uses monostable pulses shaping circuit 1, C- The minority basic circuit unit such as R peaker 2, biasing resistor 3, microwave voltage controlled oscillator VCO4 and microwave switch 5 can realize Microwave VCO directly modulation High Linear FM signal generation circuit, circuit is simple and reliable, design is convenient, debugging amount less, low cost Honest and clean.

The present invention has the features such as function admirable, circuit be simple and reliable, with low cost, is particularly well-suited to low cost, high-precision Degree, the frequency modulated continuous wave radar of miniaturization and radio proximity fuse.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of the microwave VCO directly modulation High Linear FM signal generation circuit of the present invention.

Fig. 2 is each node voltage waveform diagram in Fig. 1.

Fig. 3 is sweep characteristic curve and frequency-time (f-t) the characteristic curve schematic diagram of VCO output signal of the present invention.

Fig. 4 is time scale window curve and the echo-signal intersection mixing of general saw wave modulator fmcw radar intermediate frequency Effect schematic diagram.

Fig. 5 present invention is for IF-FRE-time (f-t) the characteristic curve schematic diagram of fmcw radar.

In figure: 1 monostable pulses shaping circuit；2C-R peaker；3 biasing resistors；4 microwave VCOs；5 microwave switches.

Detailed description of the invention

In the microwave VCO directly modulation High Linear FM signal generation circuit shown in Fig. 1, simple pulse can be used Shaping and peaker produce periodically non-linear oblique decline sawtooth sweep voltage waveform, are directly modulated microwave VCO Generation linear FM signal exports.This circuit comprises monostable pulses shaping circuit 1, C-R peaker 2, biasing resistor 3, micro- Wave pressure controlled oscillator VCO4 and microwave switch 5.Monostable pulses shaping circuit 1 uses monostable flipflop integrated circuit external fixed Time resistance R_tWith timing capacitor C_tRealize.Peaker 2 is by the resistance R being sequentially connected in series between input and outfan₁, differential Electric capacity C₁, and the earth resistance R being connected in parallel between outfan and ground₂Composition.Pulse signal after shaping is carried out by peaker 2 Differential, produces the frequency sweep control waveform of periodically non-linear oblique decline sawtooth fashion.Biasing resistor R₃It is connected on outside Between the outfan of direct voltage source and peaker 2, by biasing resistor R₃Introduce DC offset voltage and control microwave VCO Mid frequency.Voltage wave is controlled by the frequency sweep of the non-linear oblique decline sawtooth fashion of the periodicity being superimposed upon on DC offset voltage Shape is applied to the tuning tip of microwave VCO, microwave VCO directly carries out frequency modulation(PFM) and produces linear FM signal output.By setting Meter monostable circuit trigger timing element resistance R_t, electric capacity C_tSet the time constant of monostable pulses shaping circuit 1, adjust Resistance R in C-R peaker 2₁、R₂With electric capacity C₁Component value, and the DC offset voltage V provided according to outside_biasValue adjusts partially Put resistance R₃, microwave VCO 4 frequency sweep initial frequency can be controlled, terminate under frequency, and nonlinear ramp harmonic tuning voltage waveform Reduction of speed rate, it is achieved the phase of non-linear oblique decline sawtooth voltage waveform and the non-linear VT-frequency characteristic of microwave VCO 4 Compensate mutually, finally realize second order above linear frequency sweep precision.Microwave VCO 4 uses varactor to carry out frequency tuning, its tuning Between characteristic and control voltage, there is non-linear relation, it is necessary to control could to realize linear frequency modulation in nonlinear voltage waveform defeated Go out.Microwave switch 5 can use various microwave switch device and configure the realization of corresponding driver, uses Transistor-Transistor Logic level signal to carry out Control, during high level, microwave switch is in " opening " state, microwave signal can low-loss transmission, during low level at microwave switch In " shutoff " state, microwave signal transmission loss is very big, and the specific design of microwave switch 5 and realization refer to opening of actual selection Close the design data of device.The linear FM signal of microwave VCO 4 output is input to microwave switch 5, and microwave switch 5 is in monostable Pulse shaper 1 output Pulse Width Control under gate corresponding to the linear frequency sweep time VCO signal export, and turn off corresponding to The VCO signal of frequency sweep resting stage, thus when this circuit is used as self-mixing formula fmcw radar transmitter, closely echo can be eliminated Signal cross mixing effect, suppresses to intersect being mixed the intermediate frequency spurious signal caused, and reduces closely strong echo-signal intersection mixing The spuious interference to target acquisition of intermediate frequency produced.

Input is shaped as arteries and veins for the periodic pulse signal triggering linear FM signal by monostable pulses shaping circuit 1 The wide pulse signal being equal to an intraperiod line frequency sweep time, this pulse signal is divided into two-way, and a road is produced through C-R peaker Raw non-linear oblique decline sawtooth voltage signal, this voltage signal is superimposed upon by external dc voltage source through biasing resistor R₃Introduce DC offset voltage V₀On, form frequency sweep and control voltage signal, act on the tuning tip of microwave VCO 4 directly to microwave VCO 4 Carrying out frequency modulation(PFM), it is non-linear oblique decline zig-zag that frequency sweep controls voltage signal, with the non-linear tuning electricity of microwave VCO 4 Pressure-frequency characteristic mutually compensates for, and controls the generation linear FM signal of microwave VCO 4, and is fed to microwave switch input, warp Cross output linearity FM signal after microwave switch gating；Another road is added to microwave switch and controls end, controls microwave switch break-make, arteries and veins Rushing signal control microwave switch to gate microwave VCO output, gate linear frequency sweep phase microwave signal, output linearity frequency modulation is believed Number, turn off frequency sweep resting stage microwave signal, the interference that radar is worked by the suppression intermediate frequency spurious signal that closely strong echo produces.

The frequency sweep cycle of the microwave VCO directly modulation High Linear FM signal generation circuit output signal shown in Fig. 1 is equal to In the input pulse cycle, a frequency sweep cycle is divided into linear frequency sweep time and frequency sweep stop time, and wherein the linear frequency sweep time is equal to The pulse high level persistent period after monostable pulses shaping circuit 1 shaping；The frequency sweep stop time is equal to monostable pulses shaping The pulses low persistent period after circuit 1 shaping.By adjusting timing capacitor C of monostable pulses shaping circuit 1_tAnd timing Resistance R_tValue or timeconstantτ_c=R_tC_t, frequency sweep resting stage time span can be controlled.When triggering end input in monostable circuit During periodic pulse signal, the frequency tuning end at microwave VCO 4 produces periodically non-linear decline sawtooth voltage waveform, this electricity Corrugating controls lower microwave VCO 4 and produces the output of microwave frequency band linear FM signal, and frequency sweep cycle is equal to input pulse signal week Phase.By selecting the timeconstantτ of monostable pulses shaping circuit 1_c=R_tC_tWith C-R peaker 2, the capacitance-resistance of biasing resistor 3 Component value, it is possible to achieve the swept frequency range of requirement, and there is second order above sweep linearity precision.The ripple that C-R peaker 2 produces Sigmoid curves is divided into upper and lower two parts: upper part curve is corresponding to during pulse high level, and waveform is non-linear oblique decline sawtooth Ripple, lower part curve is corresponding to during pulses low, and waveform is non-linear to ramp up sawtooth waveforms, has electricity between two sections of waveforms Pressure saltus step.Wherein the non-linear oblique decline sawtooth waveform descending slope of upper part can be with VCO VT and the non-thread of frequency Property compensates, it is achieved VCO linear frequency sweep output linearity FM signal；Lower part waveform is in frequency sweep resting stage, now Microwave switch 5 turns off, and no signal exports.

Circuit operation principle is as follows: the circuit input cycle is the pulse signal s of T₁T (), through monostable pulses shaping electricity Road 1 shaping, produces and has pulsewidth equal to the Transistor-Transistor Logic level pulse signal s of frequency sweep time in the cycle₂T (), this signal is micro-through C-R After parallel circuit 2, produce non-linear oblique decline sawtooth voltage signal s as shown in Figure 2₃(t)。

In fig. 2, on waveform voltage signal curve, each point magnitude of voltage is:

$V_1=\frac{V_H-V_C}{R_1+R_2}{R}_2$

$V_2=V_1{e}^{-\frac{t_1}{\mathrm{\τ}}}$

$V_3=V_4{e}^{-\frac{{T-t}_1}{\mathrm{\τ}}}$

$V_4=V_2-\frac{V_H}{R_1+R_2}{R}_2$

Zhu Shizhong, V_HIt is shaping afterpulse voltage amplitude, T, t₁Being pulse period and pulsewidth respectively, τ is the peaker time Constant, V_cIt is electric capacity C₁On average voltage, and work as R₃>>R₂Shi You

τ≈(R₁+R₂)C₁

$V_c=\frac{e^{\frac{t_1}{\mathrm{\τ}}}-1}{e^{\frac{T}{\mathrm{\τ}}}-1}{V}_H$

External dc voltage source is through biasing resistor R₃The DC offset voltage V introduced₀For:

$V_0=\frac{R_2}{R_2+R_3}{V}_{\mathrm{bias}}$

Wherein V_biasIt is external dc voltage.

s₃T () is superimposed upon V₀On, form frequency sweep and control voltage signal s₄(t)。s₄T () puts on the tuning tip of microwave VCO, The frequency of oscillation controlling microwave VCO changes over, and produces swept-frequency signal.Microwave VCO modulation voltage waveform and being derived there Frequency-time (f-t) characteristic of VCO output signal is as shown in Figure 3.s₄(t) signal waveform and microwave VCO output frequency-time (f-t) characteristic curve is divided into two sections, and first paragraph is linear frequency sweep characteristic, and second segment is frequency sweep resting stage sweep characteristic.

S is obtained by circuit analysis₄T the expression formula of () signal waveform is

$s_4\left(t\right)=\left\{\begin{array}{cc}{V}_0+V_1{e}^{-\frac{t}{\mathrm{\&tau;}}}& (0\&le;t\&le;t_1)\\ V_0+V_4{e}^{-\frac{\left({t-t}_1\right)}{\mathrm{\&tau;}}}& (t_1<t\&le;T)\end{array}\right.$

Microwave VCO uses varactor to carry out frequency tuning, and capacitance-voltage (C-V) characteristic of varactor is as follows:

$C_j\left(V\right)=\frac{c_{j0}}{{(1+\frac{V}{\mathrm{\&phi;}})}^{\mathrm{\&gamma;}}}$

C_j0, φ be varactor zero inclined junction capacity, Built-in potential respectively, γ is the constant relevant with p-n junction type, right General abrupt junction varactor γ ≈ 1/2.

The frequency of oscillation of VCO is typically expressed as

$f_r=\frac{1}{2\mathrm{\&pi;}\sqrt{L_0(C_0+C_j\left(V\right))}}=f_0{(1+\frac{C_j\left(V\left(t\right)\right)}{C_0})}^{-\frac{1}{2}}$

$f_0=\frac{1}{2\mathrm{\&pi;}\sqrt{L_0{C}_0}}$

Wherein, V (t) is VCO VT, V₀It it is the DC component of V (t).L₀And C₀It is fixing in VCO resonant tank Inductance and electric capacity.

Frequency-voltage (f-V) characteristic according to VCO, to 0≤t≤t₁Interior output f-t specificity analysis is as follows:

As 0≤t≤t₁, V (t)=V₀+v(t),

If $k=\frac{C_j\left(V_0\right)}{C_0},x=\frac{v\left(t\right)}{V_0+\mathrm{\&phi;}},$ And by function $F\left(x\right)={(1+\frac{C_j\left(V\left(t\right)\right)}{C_0})}^{-\frac{1}{2}}={[1+k{(1+x)}^{-\mathrm{\&gamma;}}]}^{-\frac{1}{2}}$ Enter Row Tailor launches:

F (x)=a₀+a₁x+a₂x²+a₃x³+O(x⁴)

Wherein coefficient is

$a_0={(1+k)}^{-\frac{1}{2}}$

$a_1=\frac{\mathrm{\&gamma;k}}{2}{a_0}^3$

$a_2=\frac{\mathrm{\&gamma;k}}{4}{a}_0^2({3a}_1-\mathrm{\&gamma;}-1)$

$a_3=\frac{\mathrm{\&gamma;k}}{24}{a}_0^2[{6\mathrm{\&gamma;}}^2{k}^2{a}_0^5-({\mathrm{\&gamma;}}^2+\mathrm{\&gamma;})({3a}_0^3+{5a}_0^2)+({2\mathrm{\&gamma;}}^2+6\mathrm{\&gamma;}+4)]$

Order $X=\frac{V_1}{V_0+\mathrm{\&phi;}},$ Then $x^m=X^m{e}^{-\frac{\mathrm{mt}}{\mathrm{\&tau;}}}=X^m\underset{n=0}{\mathrm{\&Sigma;}}\frac{m^n}{n!}{(-\frac{t}{\mathrm{\&tau;}})}^n,$ The expansion substituting into F (x) is write as the power of t/ τ Progression form (F (x) is truncated to 3 rank), obtains

$F\left(x\left(t\right)\right)=a_0+\underset{n=1}{\mathrm{\&Sigma;}}\frac{1}{n!}(a_{1}X+2^n{a}_2{X}^2+3^n{a}_3{X}^3){(-\frac{t}{\mathrm{\&tau;}})}^n$

When meeting

a₁X+2a₂X²+3a₃X³=λ

a₁X+4a₂X²+9a₃X³=0

a₁X+8a₂X²+27a₃X³=0

Time, t in F (x (t)) expansion²、t³Coefficient is zero, and VCO output frequency is approximately (being truncated to 3 power items), i.e. achieves the linear frequency sweep that slope is-λ/τ, and has the 2 above linear precisions in rank.

For meeting above linear frequency sweep condition, when γ ≈ 1/2 parameter should select as follows:

$X\&ap;\frac{2}{3}$

$k\&ap;\frac{4}{19}$

The value of k can be by changing voltage V_biasOr resistance R₃Adjust V₀(thus adjust C_j(V₀)) meet.

Fixing V₀After, the value of k is mainly by changing voltage V_HOr resistance R₁、R₂Adjust V₁Meet.

After above parameter is selected, can be by adjusting electric capacity C₁Design load, and then adjust peaker timeconstantτ Reach required sweep rate-λ/τ.

Analysis shows at frequency sweep resting stage t₁≤ t≤T, microwave VCO output frequency has the characteristic slowly risen in time. Generally resting stage is shorter, it is believed that period frequency of stopping is approximately

$f_r=f_0{(1+\frac{C_j\left(\frac{V_3+V_4}{2}\right)}{C_0})}^{-\frac{1}{2}}$

Pulse signal s₂T () is applied to the control end of microwave switch 5 as control signal, be used for closing frequency sweep resting stage and send out Penetrating signal output, the intermediate frequency that the intersection mixing of self-mixing fmcw radar echo-signal can be suppressed to introduce is spuious.General sawtooth waveforms Fmcw radar is in frequency sweep cycle, and echo-signal produces intermediate frequency spurious signal, intermediate frequency with the mixing of next periodic emission signal cross Signal frequency-time response may refer to the time scale window curve of the intermediate-freuqncy signal of sawtooth waveforms fmcw radar shown in Fig. 4.Fig. 4 In indicated intersection mixing district, intersect mixing produce Wideband Intermediate Frequency spurious signal, be partially into IF passband formed intermediate frequency interference , when there is closely strong echo by the interference radar detection to target in signal.

For using the linear FM signal generation circuit self-mixing fmcw radar as transmitter of present invention proposition, use s₂T () controls microwave switch, gate VCO output, closes frequency sweep resting stage and launches signal output, now in fmcw radar Frequently signal frequency-time response may refer to the linear FM signal generation circuit shown in Fig. 5 fmcw radar IF-FRE-time Between (f-t) characteristic curve, in Fig. 5, dotted portion is that the resting stage echo turned off by microwave switch intersects the intermediate frequency of mixed frequency signal (f-t) characteristic curve of spurious signal.By appropriately designed frequency sweep resting stage time span, can be at the least bar of snr loss Under part, the interference that radar is worked by the suppression intermediate frequency spurious signal that closely strong echo produces.

Circuit design of the present invention can use following steps:

1) according to system application requirement, select appropriate frequency and the microwave VCO of tuning bandwidth, determine transmission center frequency values f₀, frequency sweep initial frequency f₁With termination frequency f₂, and the VT u of correspondence₀、u₁、u₂.According to circuit proposed by the invention Characteristic, should have f₁≥f₀≥f₂And u₁≥u₀≥u₂；

2) according to system application requirement, suitable frequency sweep cycle T and frequency sweep time t is selected₁, then frequency sweep resting stage t₂=T- t₁.General T >=10t₂, t₂Should be slightly bigger than the closely strong reflector echo-signal round trip transmission time；

3) monostable circuit model is selected, according to step 2) parameter that selects, designs the suitable monostable circuit time normal Number τ_cSo that monostable circuit is when the pulse signal that the input cycle is T, and output waveform high level time and low level time divide Wei t₁And t₂。τ_cDesign value and physical circuit realize referring to selected monostable circuit design data, τ_c=R_tC_tCan lead to Cross selection R_t、C_tComponent value is controlled；

4) according to formulaDetermine peaker timeconstantτ；

5) according to formulaCalculate V_c, V in formula_HIt it is the pulse signal of monostable pulses shaping circuit output The amplitude design data of selected monostable flipflop integrated circuit (the concrete numerical value refer to)；

6) according to formula $V_1=\frac{u_1-u_2}{1-e^{-\frac{t_1}{\mathrm{\&tau;}}}}$ Calculate V₁；

7) according to formula V₀=u₁-V₁Calculate V0；

8) according to formula $V_1=\frac{V_H-V_C}{R_1+R_2}{R}_2,V_0=\frac{R_2}{R_2+R_3}{V}_{\mathrm{bias}}$ (V_biasIt is the voltage of external dc voltage source) choosing Take suitable R₁、R₂And R₃Resistance value.Choose resistance value and need to should take R in view of for simplification design₃>>R₂.Meanwhile, R₁、R₂Resistance Choosing of value should make next step C₁The desirable value being easily achieved.

9) according to formulaComputing differential electric capacity C₁Value.

10) design formula of each step more than can be referring to the associated description in the explanation of circuit operation principle.Such as design result Finding that resistance, the value of electric capacity are difficult to, step 8 can be retracted into) step reselects V_biasWith each resistance value, then recalculate electricity Hold C₁Until obtaining desired value.So far, in circuit, all design parameters are equal it has been determined that circuit design completes.

Claims (10)

1. a microwave VCO directly modulation High Linear FM signal generation circuit, comprises monostable pulses shaping circuit (1), C-R Peaker (2), biasing resistor (3), microwave voltage controlled oscillator VCO(4) and microwave switch (5), it is characterised in that: monostable arteries and veins Rush shaping circuit (1) and periodic sweep start pulse signal will be inputted, when being shaped as pulsewidth equal to an intraperiod line frequency sweep Between pulse signal, this pulse signal is divided into two-way, a road through C-R peaker (2) produce nonlinear ramp wave voltage signal, This voltage signal is superimposed upon and is incorporated into the straight of C-R peaker (2) outfan from external dc voltage source via biasing resistor (3) Stream bias voltage V₀On, formed with microwave voltage controlled oscillator VCO(4) non-linear VT-frequency characteristic mutually compensate for Frequency sweep controls voltage signal, and is fed to microwave switch input, output linearity FM signal after microwave switch gates, defeated The frequency sweep cycle going out signal is equal to the input pulse cycle, and a frequency sweep cycle is divided into linear frequency sweep time and frequency sweep stop time, Wherein, the linear frequency sweep time is equal to the pulse high level persistent period after monostable pulses shaping circuit 1 shaping；When frequency sweep is stopped Between equal to the pulses low persistent period after monostable pulses shaping circuit 1 shaping；Another road is added to microwave switch and controls end, Control microwave switch break-make, the microwave signal of gating linear frequency sweep phase, output linearity FM signal, turn off the micro-of frequency sweep resting stage Ripple signal, the interference that radar is worked by the suppression intermediate frequency spurious signal that closely strong echo produces.

Microwave VCO directly modulation High Linear FM signal generation circuit the most according to claim 1, it is characterised in that: institute The monostable pulses shaping circuit (1) stated uses monostable flipflop integrated circuit external timing resistance R_tWith timing capacitor C_tReal Existing.

Microwave VCO directly modulation High Linear FM signal generation circuit the most according to claim 1, it is characterised in that: single Steady-state pulse shaping circuit (1) carries out shaping to the periodic sweep start pulse signal of input, the pulse period etc. after shaping The pulses low persistent period after frequency sweep cycle, shaping is equal to frequency sweep resting stage.

Microwave VCO directly modulation High Linear FM signal generation circuit the most according to claim 1, it is characterised in that: C-R Peaker (2) is by the resistance R being sequentially connected in series between input and outfan₁, differential capacitance C₁Be connected in parallel on outfan with ground Between earth resistance R₂Composition.

Microwave VCO directly modulation High Linear FM signal generation circuit the most according to claim 1, it is characterised in that: C-R Peaker (2) carries out differential to the pulse signal after shaping, produces sweeping of periodic non-linear oblique decline sawtooth fashion Frequency controls the waveform of voltage signal.

Microwave VCO directly modulation High Linear FM signal generation circuit the most according to claim 1, it is characterised in that: institute The biasing resistor R stated₃It is connected between the outfan of external dc voltage source and peaker (2), by biasing resistor R₃Introduce DC offset voltage V₀Control microwave voltage controlled oscillator VCO(4) mid frequency.

Microwave VCO directly modulation High Linear FM signal generation circuit the most according to claim 1, it is characterised in that: folded It is added in DC offset voltage V₀On the non-linear oblique decline sawtooth waveforms of periodicity, be applied to microwave voltage controlled oscillator VCO(4) tune Humorous end, directly to microwave voltage controlled oscillator VCO(4) carry out frequency modulation(PFM) generation linear FM signal output.

Microwave VCO directly modulation High Linear FM signal generation circuit the most according to claim 1, it is characterised in that: logical Cross design monostable circuit trigger timing element resistance R_t, electric capacity C_tThe time setting monostable pulses shaping circuit (1) is normal Number, adjusts resistance R in C-R peaker (2)₁、R₂With electric capacity C₁Component value, and the DC offset voltage V provided according to outside₀ Value adjusts biasing resistor R₃, control microwave voltage controlled oscillator VCO(4) and frequency sweep initial frequency, terminate frequency, and nonlinear ramp Harmonic tuning voltage waveform fall off rate, it is achieved with microwave voltage controlled oscillator VCO(4) non-linear VT-frequency characteristic Mutually compensate for, finally realize second order above linear frequency sweep precision.

Microwave VCO directly modulation High Linear FM signal generation circuit the most according to claim 1, it is characterised in that: micro- Wave pressure controlled oscillator VCO(4) linear FM signal that exports is input to microwave switch (5), and microwave switch (5) is at monostable pulses Shaping circuit (1) output Pulse Width Control under gate corresponding to the linear frequency sweep time microwave signal export, and turn off corresponding to The microwave signal of frequency sweep resting stage.

Microwave VCO directly modulation High Linear FM signal generation circuit the most according to claim 1, it is characterised in that: micro- Ripple switch (5) is by various microwave switch devices and configures the realization of corresponding driver, uses Transistor-Transistor Logic level signal to be controlled, high During level, microwave switch is in " opening " state, and during low level, microwave switch is in " shutoff " state.