CN103457668A - Frequency conversion system and use methods based on two-arm electro-optical external modulation - Google Patents

Abstract

The invention discloses a frequency conversion system and use methods based on two-arm electro-optical external modulation. A bias voltage of a bias voltage control circuit of the frequency conversion system is respectively connected with two-arm electrodes of an electro-optical external modulator. The output ends of the two-arm electrodes are connected with an optical splitter. One output end of the optical splitter is connected with an optical detector. After passing through a frequency-selecting amplification circuit, the output of the optical detector is used as the output of the frequency conversion system. The other output end of the optical splitter is connected into the bias voltage control circuit through a microwave photon filter, and the bias voltage is fed back and controlled to be the optimum value. The frequency conversion system can be in two-electrode connection. One use method comprises the steps that an optical carrier signal is connected into the optical input end of the electro-optical external modulator, two-arm input local oscillators and radio/intermediate-frequency signals are added to be equal to a bias voltage of a two-arm half-wave voltage, and down/up-conversion microwave signals are obtained. The other use method comprises the steps that the optical input end is connected into the local oscillators, two-arm input radio-frequency signals are added to be equal to the bias voltage of the two-arm half-wave voltage, and a frequency-doubled local oscillator signal is obtained. According to the frequency conversion system and the use methods based on the two-arm electro-optical external modulation, microwave signal frequency conversion or local oscillator signal optical frequency doubling is achieved through primary equipment, the power is improved, the cost is low, and the reliability is high.

Description

Frequency conversion system and using method based on both arms electric light external modulation

Technical field

The present invention relates to the microwave photon technical field, be specially a kind of frequency conversion system and using method based on the both arms electrooptic modulation.

Background technology

For a long time, mainly utilize the nonlinear effect of electronic device to carry out the Up/Down Conversion of microwave frequency.Along with the development of microwave technology, microwave operational frequencies improves constantly, and has now reached Ka wave band (electromagnetic wave of wavelength 11.11-7.50mm), millimere-wave band (electromagnetic wave that wavelength is 10～1mm).Utilize traditional method to carry out the frequency conversion of microwave frequency, the problem such as occurred that technical difficulty is large, signal quality is poor and adaptive capacity to environment is weak.

Along with the development of microwave photon technology, for the mixing of microwave frequency provides another kind of selection: i.e. continuous ripe electric light analog-modulated technology.The appearance of the MZ Mach-Zehnder based on lithium niobate (LiNbO3) (MZM) particularly, realized the Up/Down Conversion of the strong and great dynamic range of the high-quality based on microwave photon, the environmental suitability of Ka wave band, millimere-wave band signal (or even terahertz signal).

At present, the microwave photon technology realizes that the microwave signal mixing is mainly to adopt the two-stage modulation method: first local oscillation signal is modulated on light carrier and forms RoF(radio-over-fiber) light carries microwave signal; Then, the microwave signal that needs frequency conversion also is modulated to the RoF signal as modulated subcarrier signal; Subsequently, by photodetector, light signal is converted to the signal of telecommunication that contains various frequency contents; Finally, filtering frequency-selecting and the power amplification by electric territory obtains required Up/Down Conversion signal.And not only contain microwave signal (RF in the microwave spectrum of the existing gained based on the two-stage electrooptic modulation _in), 3 rd harmonic signal of local oscillation signal and local oscillator, but also contain optical carrier, local oscillation signal and microwave signal and the interference signals such as difference frequency signal frequency signal, local oscillation signal and microwave signal.

The existing electronic circuit generation microwave of multistage frequency multiplication, the scheme that millimeter-wave signal carries out mixing utilized realizes complicated, and cost is higher, in addition, in a lot of applications, the generation of microwave and millimeter wave need to be distributed in far-end unit, because the loss of electric transmission line (as coaxial cable etc.) is large, so microwave and millimeter wave produces in the electric territory of far-end and then transmission is returned unrealistic.

Current light territory frequency mixing technique adopts light injecting lock mould, Optical phase-locked loop, light injection phase-locking, realizes based on intensity modulated with based on methods such as phase-modulations, but the problems such as these light territories frequency mixing methods exist that input microwave dynamic ranges are little, the output microwave power is low, microwave receiving sensitivity is low, the stability of a system is poor, reliability is low and noise factor is large, be difficult to apply in practice.

Summary of the invention

The objective of the invention is to disclose a kind of frequency conversion system based on the both arms electrooptic modulation, the both arms photoelectric external modulator is main devices, be equipped with bias voltage control circuit, photodetector and selective frequency amplifier circuit, suitably modulate the bias voltage of both arms photoelectric external modulator, the optical carrier that enters the light source of two arms is transfused to the microwave signal of two arms and microwave local oscillation signal and modulates respectively and form two-way light and carry microwave signal, two-way light carries the light that microwave signal is superposed to both arms photoelectric external modulator output and carries microwave signal, be converted to the signal of telecommunication through photodetector, the frequency-selecting power amplification obtains required Up/Down Conversion signal.

Another object of the present invention is the using method that discloses the above-mentioned frequency conversion system based on the both arms electrooptic modulation, when the input radio frequency microwave signal, but down-conversion obtains the intermediate frequency microwave signal, when input intermediate frequency microwave signal, but up-conversion obtains the frequency microwave signal, can also carry out optical sccond-harmonic generation to local oscillation signal, obtain the local oscillation signal of high frequency.

The frequency conversion system based on the both arms electrooptic modulation of the present invention's design, comprise both arms photoelectric external modulator, bias voltage control circuit, photodetector and selective frequency amplifier circuit; The bias voltage of bias voltage control circuit accesses respectively the electrode of two arms of both arms photoelectric external modulator, the output of both arms photoelectric external modulator connects photo-detector, the signal of telecommunication access selective frequency amplifier circuit of photo-detector output, the output that the output of selective frequency amplifier circuit is this frequency conversion system.

This frequency conversion system also has feedback device, the output of both arms photoelectric external modulator connects optical splitter, an output of optical splitter connects photo-detector, another output access microwave photon filter, the signal of telecommunication access bias voltage control circuit of microwave photon filter output, the bias voltage value of controlling its output as feedback signal remains best operating point.

This frequency conversion system based on the both arms electrooptic modulation can front and back stages connect, the light input end of the frequency conversion system local oscillation signal input both arms photoelectric external modulator of prime based on the both arms electrooptic modulation, and the frequency microwave signal is inputted two arms, the local oscillation signal of output optical sccond-harmonic generation; In the frequency conversion system of rear class based on the both arms electrooptic modulation, the light input end of optical carrier input both arms photoelectric external modulator, the local oscillation signal of the optical sccond-harmonic generation of prime output is inputted an arm, radio frequency or intermediate frequency microwave signal and is inputted another arm, intermediate frequency or the frequency microwave signal of output frequency conversion.

The frequency conversion system using method that the present invention is based on the both arms electrooptic modulation is as follows:

Optical carrier is divided into two-way from the light input end access of both arms photoelectric external modulator, enters two arms of both arms photoelectric external modulator; Wherein one arm is inputted local oscillation signal, another one arm input radio frequency or intermediate frequency microwave signal, local oscillation signal and microwave signal are modulated and are formed two-way light and carry microwave signal the optical carrier that enters two arms, bias voltage control circuit provides suitable bias voltage to two arms, light carrier power is moved on the sideband power of light, suppress to greatest extent light carrier, the microwave signal power output after the lifting frequency conversion.Two-way light carries after microwave signal stack has the light signal of microwave signal for what the both arms photoelectric external modulator was exported through modulation, and light carries microwave signal p (t).Light carries microwave signal and carries out opto-electronic conversion at photo-detector, optical power signals is converted to the intensity signals that contains various frequency contents, through selective frequency amplifier circuit, by filtering frequency-selecting and the power amplification in electric territory, obtain the frequency microwave signal of intermediate frequency microwave signal or the up-conversion of needed down-conversion.

It is as follows that the output light of both arms photoelectric external modulator carries microwave signal p (t) expression formula:

$p\left(t\right)=\frac{1}{2}{a}_{\mathrm{loss}}{P}_c\[\cos (\frac{\mathrm{\π}{V}_{\mathrm{DC}1}}{V_{\mathrm{\π}1}}-\frac{\mathrm{\π}{V}_{\mathrm{Lo}}\cos \left({\mathrm{\ω}}_{\mathrm{Lo}}t\right)}{V_{\mathrm{\π}1}})+\cos (\frac{{\mathrm{\πV}}_{\mathrm{DC}2}}{V_{\mathrm{\π}2}}-\frac{{\mathrm{\πV}}_{\mathrm{RF}}\cos \left({\mathrm{\ω}}_{\mathrm{RF}}t\right)}{V_{\mathrm{\π}2}})\]---\left(1\right)$

(1) in formula: a _lossfor optical link power loss, P _cfor optical carrier, V _{π 1}for the half-wave voltage value of article one arm, V _{π 2}half-wave voltage value for the second arm; V _dC1for the quiescent point magnitude of voltage of article one arm, V _dC2for the quiescent point magnitude of voltage of second arm, V _lOfor the range value of local oscillation signal, V _rFfor the range value of microwave signal, ω _lofor local oscillation signal angular frequency, ω _rFfor the radiofrequency signal angular frequency.

As π V _rF/ V _πwhen very little, the situation of small signal modulation, very little with respect to low order Bessel function value by the known high-order Bessel function of the character of Bessel function value, can ignore.Utilize Bessel function to launch to obtain to formula (1):

$p\left(t\right)\≈{\mathrm{\α}}_{\mathrm{MZM}}{A}_0\{\[\cos \frac{{\mathrm{\πV}}_{\mathrm{DC}1}}{V_{\mathrm{\π}1}}{J}_0\left(\frac{{\mathrm{\πV}}_{\mathrm{Lo}}}{V_{\mathrm{\π}1}}\right)+\cos \frac{{\mathrm{\πV}}_{\mathrm{DC}2}}{V_{\mathrm{\π}2}}{J}_0\left(\frac{{\mathrm{\πV}}_{\mathrm{RF}}}{V_{\mathrm{\π}2}}\right)\]\cos \left({\mathrm{\ω}}_{C}t\right)+\sin \frac{{\mathrm{\πV}}_{\mathrm{DC}1}}{V_{\mathrm{\π}1}}{J}_1\left(\frac{{\mathrm{\πV}}_{\mathrm{Lo}}}{V_{\mathrm{\π}1}}\right)\cos ({\mathrm{\ω}}_c+$

${\mathrm{\ω}}_{\mathrm{Lo}})t+\sin \frac{{\mathrm{\πV}}_{\mathrm{DC}1}}{V_{\mathrm{\π}1}}{J}_1\left(\frac{{\mathrm{\πV}}_{\mathrm{Lo}}}{V_{\mathrm{\π}1}}\right)\cos ({\mathrm{\ω}}_c-{\mathrm{\ω}}_{\mathrm{Lo}})t+\sin \frac{{\mathrm{\πV}}_{\mathrm{DC}2}}{V_{\mathrm{\π}2}}{J}_1\left(\frac{{\mathrm{\πV}}_{\mathrm{RF}}}{V_{\mathrm{\π}2}}\right)\cos ({\mathrm{\ω}}_c+{\mathrm{\ω}}_{\mathrm{RF}})t+$

$\sin \frac{{\mathrm{\πV}}_{\mathrm{DC}2}}{V_{\mathrm{\π}2}}{J}_1\left(\frac{{\mathrm{\πV}}_{\mathrm{RF}}}{V_{\mathrm{\π}2}}\right)\cos ({\mathrm{\ω}}_c-{\mathrm{\ω}}_{\mathrm{RF}})t\}$

(2)

Known according to formula (2): as the quiescent biasing voltage V of both arms photoelectric external modulator _dc1and V _dc2be arranged on best operating point, with

the time, $\cos \frac{{\mathrm{\πV}}_{\mathrm{DC}1}}{V_{\mathrm{\π}1}}{J}_0\left(\frac{{\mathrm{\πV}}_{\mathrm{Lo}}}{V_{\mathrm{\π}1}}\right)+\cos \frac{{\mathrm{\πV}}_{\mathrm{DC}2}}{V_{\mathrm{\π}2}}{J}_0\left(\frac{{\mathrm{\πV}}_{\mathrm{RF}}}{V_{\mathrm{\π}2}}\right)$ Just equal 0.Perhaps dynamically adjust the voltage V of the quiescent point of both arms photoelectric external modulator _dC1and V _dC2also can realize $\cos \frac{{\mathrm{\πV}}_{\mathrm{DC}1}}{V_{\mathrm{\π}1}}{J}_0\left(\frac{{\mathrm{\πV}}_{\mathrm{Lo}}}{V_{\mathrm{\π}1}}\right)+\cos \frac{{\mathrm{\πV}}_{\mathrm{DC}2}}{V_{\mathrm{\π}2}}{J}_0\left(\frac{{\mathrm{\πV}}_{\mathrm{RF}}}{V_{\mathrm{\π}2}}\right)$ Level off to 0.Because of cos (ω _ct) coefficient entry equals 0, just suppresses the electrooptic modulation of light carrier.

The bias voltage that in this frequency conversion system using method based on the both arms electrooptic modulation, bias voltage control circuit offers the both arms electrooptic modulator equals the half-wave voltage value of both arms, with

the signal of telecommunication of microwave photon filter feedback makes bias voltage control circuit keep bias voltage stable.

The input optical power of described photodetector is less than the saturated light power of photodetector.

The frequency conversion system using method of another kind of the present invention based on the both arms electrooptic modulation is as follows: the trimmed book signal that shakes is divided into two-way from the access of the light input end of both arms photoelectric external modulator, enters two arms of both arms photoelectric external modulator; The frequency microwave signal is divided into two-way input both arms photoelectric external modulator two arms, and bias voltage control circuit offers the bias voltage V of both arms _dc1and V _dc2be arranged on the half-wave voltage value that best operating point equals both arms,

with the signal of telecommunication of microwave photon filter feedback makes bias voltage control circuit keep bias voltage stable.The frequency microwave signal of described input two arms is modulated the trimmed book that enters two arms signal that shakes, the light that obtains optical sccond-harmonic generation carries local oscillation signal, photodetector carries the local oscillator optical power signals by the light of frequency multiplication and is converted to the intensity signals that contains various frequency contents, through selective frequency amplifier circuit, by filtering frequency-selecting and the power amplification in electric territory, obtain the local oscillation signal of frequency multiplication.

Local oscillation signal (the P of the frequency multiplication of photodetector output _d) expression formula be shown below:

$P_d=i_d^2{R}_{\mathrm{load}}=r_d^2{P}_{\mathrm{od}}^2{R}_{\mathrm{load}}={\mathrm{\η}}_D^2{r}_D^2{P}_{\mathrm{od}}^2{R}_{\mathrm{load}}---\left(3\right)$

Wherein: i _dfor the electric current after opto-electronic conversion, R _loadfor the impedance of photodetector, P _odfor luminous power, r _dfor the electric current that desirable luminous power all converts to, η _dfor luminous power is converted to the efficiency of electric current.

After formula (1) is launched by Bessel function (only launching second harmonic term) substitution formula (3) can obtain the power output signal of photodetector the Bezier expression formula (leach high-frequency signal,

formula (4) is as follows:

Wherein: V _rF1for the range value of first via microwave signal, V _rF2be the range value of the second tunnel microwave signal, η _dfor the photoelectric conversion efficiency of photodetector, R _loadfor the output impedance of photodetector, phase difference for the two-way frequency microwave signal that is input to the both arms photoelectric external modulator.

The both arms electrooptic modulator is operated in the just bias electrical voltage point

with the time, the frequency-doubled signal of output only comprises 2 frequencys multiplication and 4 frequency-doubled signals, and 1 frequency multiplication and 3 frequency-doubled signals are fully suppressed.The phase difference of the two-way frequency microwave signal of input both arms intensity on output signal has larger impact, and the impact of 4 frequency-doubled signals is greater than to the impact on 2 frequency-doubled signals.

The input optical power of described photodetector is less than the saturated light power of photodetector.

The microwave current operating frequency improves constantly, Ka wave band, millimere-wave band have now been reached, while carrying out the frequency conversion mixing, directly provide high local oscillation signal like this more difficult, this method will be carried out optical sccond-harmonic generation than the local oscillation signal of low frequency, the local oscillation signal of high frequency is provided, can be as the local oscillation signal of the frequency conversion system that the present invention is based on the both arms electrooptic modulation.

Compared with prior art, the present invention is based on the frequency conversion system of both arms electrooptic modulation and the advantage of using method is: 1, the microwave signal of high band (RF) can be down-converted to the microwave signal (RF) that lower intermediate-freuqncy signal (IF) or intermediate-freuqncy signal (IF) that will be lower upconvert to higher frequency band, also can carry out optical sccond-harmonic generation, frequency requirement with the reduction system to the input local oscillation signal to local oscillation signal; Light carries microwave signal (RoF) when short range transmission, effectively promotes light source power, local oscillation power or light source power and local oscillation power long-pending; 2, compare with two-stage modulation system at present commonly used, reduced the use of one-level equipment, the volume of equipment reduces, and the consumption of device reduces, and reduces costs, and has improved the reliability of system simultaneously; 3, only contain microwave signal (RF in the microwave signal spectrum after the frequency conversion of native system gained _in), 3 rd harmonic signal of local oscillation signal and local oscillator, the unwanted signals such as 2 subharmonic of optical carrier, local oscillator and intermodulation signal have all obtained good inhibition; 4, in the situation that keep the photodetector input optical power constant, increase the dynamic range of input microwave signal (RFin), simultaneously, also increased the power output (IFout) of the intermediate-freuqncy signal of photodetector, reduce the noise factor of system, promoted system effectiveness; While 5, not carrying out the optical signal power amplification in optical link, keep communication link unsaturated, avoid the nonlinear effect due to the saturated generation of power of equipment in optical link, prevent that it from causing distorted signals; 6, in photodetector receiving sensitivity scope, effectively increase the transmission range that light carries microwave signal; 7, be applicable in broadband wireless access, sensing network, radar, satellite communication, testing meter and instrument and armament systems, for generation, processing, control and the distribution etc. of Ka band microwave signal, millimeter-wave signal realize high-quality, environmental suitability is strong and the frequency conversion of great dynamic range.

The accompanying drawing explanation

Fig. 1 is this frequency conversion system example structure block diagram based on the both arms electrooptic modulation.

Embodiment

Illustrate this frequency conversion system and using method embodiment based on the both arms electrooptic modulation below in conjunction with accompanying drawing.

This frequency conversion system embodiment based on the both arms electrooptic modulation as shown in Figure 1, solid line indication circuit in figure, dotted line means light path.This example is that prime is connected use with the frequency conversion system of rear class two-stage based on both arms electric light external modulation, the two-stage system structure is identical, includes both arms photoelectric external modulator, bias voltage control circuit, optical splitter, microwave photon filter, photodetector and selective frequency amplifier circuit; The bias voltage of bias voltage control circuit accesses respectively the electrode of two arms of both arms photoelectric external modulator, the output of both arms photoelectric external modulator connects optical splitter, an output of optical splitter connects photo-detector, another output access microwave photon filter, the signal of telecommunication access bias voltage control circuit of microwave photon filter output.

The prime of the using method embodiment of this frequency conversion system based on the both arms electrooptic modulation is for being used the frequency conversion system based on the both arms electrooptic modulation to carry out optical sccond-harmonic generation to local oscillation signal, the trimmed book signal LC that shakes is divided into two-way from the access of the light input end of both arms photoelectric external modulator, enters two arms of both arms photoelectric external modulator; Frequency microwave signal RF (f) is divided into two arms that two-way RF1 and RF2 input respectively the both arms photoelectric external modulator, and bias voltage control circuit offers the bias voltage V of both arms _dc1and V _dc2be arranged on the half-wave voltage value that best operating point equals both arms,

with the signal of telecommunication of microwave photon filter feedback makes bias voltage control circuit keep bias voltage stable.The frequency microwave signal RF1 of described input two arms and RF2 are modulated the trimmed book that enters two arms signal LC that shakes, and the light that obtains optical sccond-harmonic generation carries local oscillation signal, and photodetector carries local oscillation signal by the light of frequency multiplication and is converted to the signal of telecommunication.Through selective frequency amplifier circuit, obtain the local oscillation signal LC (n) of frequency multiplication.

The rear class of the using method embodiment of this frequency conversion system based on the both arms electrooptic modulation is to use the frequency conversion system based on the both arms electrooptic modulation to carry out the photoelectricity frequency conversion, optical carrier P is divided into two-way from the light input end access of both arms photoelectric external modulator, enters two arms of both arms photoelectric external modulator; The local oscillation signal LC (n) of the frequency multiplication of one arm input backing system output wherein, another one arm input radio frequency microwave signal RFin, the bias voltage that bias voltage control circuit offers the both arms electrooptic modulator equals the half-wave voltage value of both arms,

with

the signal of telecommunication of microwave photon filter feedback makes bias voltage control circuit keep bias voltage stable, local oscillation signal and microwave signal are modulated and are formed two-way light and carry microwave signal the optical carrier that enters two arms, two-way light carries the rear modulated light signal that microwave signal is arranged for the output of both arms photoelectric external modulator of microwave signal stack, and light carries microwave signal p (t).Light carries microwave signal and carries out opto-electronic conversion at photo-detector, and optical power signals is converted to intensity signals, through selective frequency amplifier circuit, obtains the intermediate frequency microwave signal IFout of needed down-conversion.

The frequency conversion system of this routine two-stage based on the both arms electrooptic modulation all chosen the both arms photoelectric external modulator of 5GHz, backing system input 1GHz local oscillation signal LC, the radiofrequency signal RF (f) of input is 5GHz, it is unsaturated that the input optical power of photodetector is less than the 5dBm(luminous power), the local oscillation signal of the 4 frequency multiplication 4GHz of output-15.4dBm after conversion, after the power amplification of selective frequency amplifier circuit 30dB, obtain the local oscillation signal LC (n) of frequency multiplication, wherein the signal after 2 frequencys multiplication and 4 frequencys multiplication is respectively 10GHz and 20GHz.The power output of 2 frequency-doubled signals is greater than 0dBm, be greater than-20dBm of the power output of 4 frequency-doubled signals, and 1 frequency multiplication, 3 frequencys multiplication and other mixed frequency signal are fully suppressed, the local oscillation signal LC (n) after frequency multiplication can be used as the local oscillation signal of rear class both arms photoelectric external modulator fully

In rear level system, the local oscillation signal LC (n) of the 4GHz of prime gained and the frequency microwave signal RFin of 5GHz input respectively two arms, obtain the 1GHz intermediate frequency microwave signal IFout of needed down-conversion.

Comparative Examples adopts the two-stage modulation method: first order modulating equipment is modulated to formation light on light carrier by the local oscillation signal of 4GHz and carries microwave signal; Second level modulating equipment also is modulated to the RoF signal as modulated subcarrier signal using the frequency microwave signal of 5GHz; Conversion and selective frequency amplifier circuit by photodetector obtains required down-conversion signal again.

After the present embodiment and Comparative Examples electrooptic modulation, the leading indicator of the intermediate-freuqncy signal of gained is relatively referring to table 1.

Gained signal comparison sheet after table 1 the present embodiment and Comparative Examples electrooptic modulation

From table 1, this routine photodetector input optical power just meets distortionless requirement, the input dynamic range (only consider ground noise impact) of the microwave signal after its conversion is than the large 23dB of Comparative Examples, the high 13dB of the receiving sensitivity of microwave signal, the intermediate-freuqncy signal (IF that finally this example is exported _out) the large 32dB of power ratio Comparative Examples.

Above-described embodiment, be only the specific case that purpose of the present invention, technical scheme and beneficial effect are further described, and the present invention not is defined in this.All any modifications of making, be equal to replacement, improvement etc., within all being included in protection scope of the present invention within scope of disclosure of the present invention.

Claims (7)

1. the frequency conversion system based on the both arms electrooptic modulation, comprise both arms photoelectric external modulator, bias voltage control circuit, photodetector and selective frequency amplifier circuit; The bias voltage of bias voltage control circuit accesses respectively the electrode of two arms of both arms photoelectric external modulator, the output of both arms photoelectric external modulator connects photo-detector, the signal of telecommunication access selective frequency amplifier circuit of photo-detector output, the output that the output of selective frequency amplifier circuit is this frequency conversion system.

2. the frequency conversion system based on the both arms electrooptic modulation according to claim 1 is characterized in that:

Also has feedback device, the output of described both arms photoelectric external modulator connects optical splitter, an output of optical splitter connects photo-detector, another output access microwave photon filter, the signal of telecommunication access bias voltage control circuit of microwave photon filter output.

3. the frequency conversion system based on the both arms electrooptic modulation according to claim 1 and 2 is characterized in that:

The described frequency conversion system front and back stages based on the both arms electrooptic modulation connects, the light input end of the frequency conversion system local oscillation signal input both arms photoelectric external modulator of prime based on the both arms electrooptic modulation, and the frequency microwave signal is inputted two arms, the local oscillation signal of output optical sccond-harmonic generation; In the frequency conversion system of rear class based on the both arms electrooptic modulation, the light input end of optical carrier input both arms photoelectric external modulator, the local oscillation signal of the optical sccond-harmonic generation of prime output is inputted an arm, radio frequency or intermediate frequency microwave signal and is inputted another arm, intermediate frequency or the frequency microwave signal of output frequency conversion.

4. the using method of the frequency conversion system based on the both arms electrooptic modulation according to claim 2 is characterized in that:

Optical carrier is divided into two-way from the light input end access of both arms photoelectric external modulator, enters two arms of both arms photoelectric external modulator; Wherein one arm is inputted local oscillation signal, another one arm input radio frequency or intermediate frequency microwave signal, local oscillation signal and microwave signal are modulated and are formed two-way light and carry microwave signal the optical carrier that enters two arms, bias voltage control circuit provides suitable bias voltage to both arms, and two-way light carries the microwave signal stack and carries microwave signal for both arms photoelectric external modulator output light afterwards; Light carries microwave signal and carries out opto-electronic conversion at photo-detector, and optical power signals is converted to the intensity signals that contains various frequency contents, through selective frequency amplifier circuit, obtains the frequency microwave signal of intermediate frequency microwave signal or the up-conversion of needed down-conversion;

The bias voltage that bias voltage control circuit offers both arms equals the half-wave voltage value of both arms.

5. the using method of the frequency conversion system based on the both arms electrooptic modulation according to claim 4 is characterized in that:

The input optical power of described photodetector is less than the saturated light power of photodetector.

6. the using method of the frequency conversion system based on the both arms electrooptic modulation according to claim 2 is characterized in that:

The trimmed book signal that shakes is divided into two-way from the access of the light input end of both arms photoelectric external modulator, enters two arms of both arms photoelectric external modulator; The frequency microwave signal is divided into two-way input both arms photoelectric external modulator two arms, and bias voltage control circuit offers the bias voltage V of both arms _dc1and V _dc2be arranged on the half-wave voltage value that best operating point equals both arms, the signal of telecommunication of microwave photon filter feedback makes bias voltage control circuit keep bias voltage stable; The frequency microwave signal of described input two arms is modulated the trimmed book that enters two arms signal that shakes, the light that obtains optical sccond-harmonic generation carries local oscillation signal, photodetector carries the local oscillator optical power signals by the light of frequency multiplication and is converted to the intensity signals that contains various frequency contents, through selective frequency amplifier circuit, by filtering frequency-selecting and the power amplification in electric territory, obtain the local oscillation signal of frequency multiplication.

7. the using method of the frequency conversion system based on the both arms electrooptic modulation according to claim 6 is characterized in that:

The input optical power of described photodetector is less than the saturated light power of photodetector.

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