CN102761374A - Radio frequency photon link system - Google Patents

Abstract

The invention relates to the field of a radio frequency photo-electronic technology and discloses a radio frequency photon link system. The radio frequency photon link system comprises a pre-microwave circuit and a radio frequency photon link, wherein the radio frequency photon link comprises a laser device, a polarization controller, a photo-electronic modulator and a detector. The pre-microwave circuit designed on the basis of a JFET (Junction Field-Effect Transistor) integrates a pre-distortion function and a pre-discharge function, so that the gain of the radio frequency photon link can be greatly improved, and the noise coefficient is reduced; and the three-step non-linear distortion component of the whole radio frequency photon link system can be restrained by introducing pre-distortion.

Description

Radio frequency photon chain-circuit system

Technical field

The present invention relates to radio frequency photoelectron technology field, particularly a kind of radio frequency photon chain-circuit system.

Background technology

The radio frequency optoelectronics is the emerging cross discipline that microwave and photon technology combine, and has big bandwidth, many advantages such as volume is little, in light weight, loss is little, anti-electromagnetic interference, low chromatic dispersion, receives and pays close attention to widely and study; Radio frequency photon link is as this technological core; Can receive microwave signal and microwave signal output is provided; In the light territory, radiofrequency signal is directly transmitted control and treatment, be widely applied to fields such as electronic warfare, radar, remote sensing, sensing network, radio communication, cable TV.

The performance parameter of radio frequency photon link mainly comprises gain, noise factor and dynamic range.Traditional radio frequency photon link utilization pre-low-noise amplifier, the gain that can effectively improve chain-circuit system improves the output signal-to-noise ratio of signal, but also will worsen the dynamic range of system simultaneously; And adopt traditional predistortion circuit, though can effectively suppress the third-order non-linear crosstalk of system, the insertion loss of circuit simultaneously also will cause the gain of whole system to reduce, and worsens the noise factor of system.So it is most important how to improve the research of each item performance index of chain-circuit system simultaneously, this is the prerequisite that can radio frequency photon link large-scale application.

Therefore, be necessary to design a kind of simple and easy practicality, have the preposition microwave circuit of putting in advance with predistortion function concurrently, make it can improve gain, noise factor and the dynamic range of chain-circuit system simultaneously.

Summary of the invention

The technical problem that (one) will solve

The technical problem that the present invention will solve is: how to design a kind of preposition microwave circuit, make the gain of conventional radio frequency photon chain-circuit system be improved, noise factor reduces, and the third-order non-linear crosstalk is inhibited.

(2) technical scheme

In order to solve the problems of the technologies described above, the present invention provides a kind of radio frequency photon chain-circuit system, comprises preposition microwave circuit and radio frequency photon link, and said radio frequency photon link comprises laser, Polarization Controller, electrooptic modulator and detector;

Said laser is used to produce light carrier;

Said Polarization Controller is connected between said laser and the electrooptic modulator, is used for being adjusted into the polarization state of the light carrier of laser output consistent with the main shaft of electrooptic modulator;

Said preposition microwave circuit is connected with said electrooptic modulator, is used for the input radio frequency signal that receives is amplified, and increases the modulation depth of said electrooptic modulator, and suppresses the third-order non-linear crosstalk of said radio frequency photon chain-circuit system;

Said electrooptic modulator is used for said input radio frequency signal is modulated to said light carrier;

Said detector is connected with said electrooptic modulator, is used for converting the light signal that obtains after the said electrooptic modulator modulation to the signal of telecommunication, to recover said input radio frequency signal.

Preferably, said preposition microwave circuit comprises the JFET FET, and the transfer characteristic curve of said JFET FET satisfies square law relationship.

Preferably, said preposition microwave circuit comprises: JFET FET, two inductance L 1, L2, two capacitor C 1, C2, two resistance R _S, R _L, wherein, the grid of said JFET FET connects an end of capacitor C 1 and an end of inductance L 1, and drain electrode connects an end of capacitor C 2 and an end of inductance L 2, source ground; The other end of said capacitor C 1 connects the source resistance R _SAn end, resistance R _SThe other end connect signal source V _InAn end, said signal source V _InOther end ground connection; The other end of capacitor C 2 connects load resistance R _LAn end, load resistance R _LOther end ground connection.

Preferably, the other end of said inductance L 1 connects gate bias voltage, and the other end of said inductance L 2 connects the drain electrode direct voltage.

(3) beneficial effect

Technique scheme has following advantage: the preposition microwave circuit that the present invention is based on the design of JFET FET is one with predistortion with preparatory playing function collection; Can improve the gain of chain-circuit system greatly; Noise-reduction coefficient, and through introducing the third-order non-linear distortion component that predistortion can suppress whole system.

Description of drawings

The high-performance radio-frequency photon chain-circuit system frame diagram that Fig. 1 adopts for the present invention based on preposition microwave circuit;

Fig. 2 a is the structure chart of the preposition microwave circuit of the present invention's employing, and Fig. 2 b is I-V working curve and the transfer characteristic curve figure of JFET;

Fig. 3 is a system configuration sketch map of the present invention.

Wherein, 101: radio frequency photon chain-circuit system; 102: preposition microwave circuit; 103: radio frequency photon link; 1: laser; 2: the Mach-Zehnder intensity modulator; 3: Polarization Controller; 4: detector.

Embodiment

Below in conjunction with accompanying drawing and embodiment, specific embodiments of the invention describes in further detail.Following examples are used to explain the present invention, but are not used for limiting scope of the present invention.

The embodiment of the invention adopts the simulated photons link based on the Mach-Zehnder intensity modulator to describe as example; But not restriction scope of the present invention; No matter lithium niobate modulator or electroabsorption modulator; No matter directly be in harmonious proportion and transfer to other localities, as long as exist the modulated process of third-order non-linear distortion all can contain.

System's 101 structures of the embodiment of the invention are as shown in Figure 1, comprise preposition microwave circuit 102 and 103 two modules of radio frequency photon link, and wherein the output signal of preposition microwave circuit will be as the input signal of photon link.Said radio frequency photon link 103 comprises laser 1, Polarization Controller 3, Mach-Zehnder intensity modulator 2 and detector 4; Said laser 1 is used to produce light carrier; Said Polarization Controller 3 is connected between said laser 1 and the Mach-Zehnder intensity modulator 2, is used for being adjusted into the polarization state of the light carrier of laser 1 output consistent with the main shaft of Mach-Zehnder intensity modulator 2; Said preposition microwave circuit 102; Be connected with said Mach-Zehnder intensity modulator 2; Be used for the input radio frequency signal that receives is amplified, increase the modulation depth of said Mach-Zehnder intensity modulator 2, and suppress the third-order non-linear crosstalk of photon chain-circuit system; Said Mach-Zehnder intensity modulator 2 is used for said input radio frequency signal is modulated to said light carrier; Said detector 4 is connected with said Mach-Zehnder intensity modulator 2, is used for converting the light signal that obtains after said Mach-Zehnder intensity modulator 2 modulation to the signal of telecommunication, to recover said input radio frequency signal.

The structure chart of preposition microwave circuit comprises shown in Fig. 2 a: JFET FET, two inductance L 1, L2, two capacitor C 1, C2, two resistance R _S, R _L, wherein, the grid G of said JFET FET connects an end of capacitor C 1 and an end of inductance L 1, and drain D connects an end of capacitor C 2 and an end of inductance L 2, source S ground connection; The other end of said capacitor C 1 connects the source resistance R _SAn end, the source resistance R _SThe other end connect signal source V _InAn end, the other end ground connection of said signal source; The other end of capacitor C 2 connects load resistance R _LAn end, load resistance R _LOther end ground connection.The other end of said inductance L 1 connects gate bias voltage V _Bias, the other end of said inductance L 2 connects drain electrode direct voltage V _DcThe nucleus module of this preposition microwave circuit is the JFET FET, comprises grid, drain electrode and source electrode, and the I-V working curve of JFET FET and transmission characteristic curve are shown in Fig. 2 b, and this curve will be done detailed explanation in the back.Through control grid bias voltage V _BiasAnd input signal source V _InSize, can be so that the JFET FET works in Class A mode of operation (Class A), load resistance R _LSize then according to the drain electrode direct voltage V of JFET FET characteristic and drain electrode _DcConfirm.In addition, two capacitor C 1, C2 are used for the isolated DC signal in the preposition microwave circuit, and two inductance L 1, L2 are used to isolate AC signal.

The similar microwave amplifier of groundwork principle of this preposition microwave circuit has utilized the non-linear transfer characteristic of JFET FET simultaneously, makes that this preposition microwave amplifiercation circuit has predistortion function.

Preposition microwave circuit can improve gain, noise factor and the third-order non-linear distortion performance of conventional radio frequency photon chain-circuit system simultaneously, will launch explanation respectively from this three aspect below.

One, gain

As shown in Figure 1, the gain that the preposition microwave circuit of the first order provides is G ₁, the gain of partial radio frequency photon link is G ₂, the satisfied G=G that concerns of the gain G of the radio frequency photon chain-circuit system of the two composition ₁G ₂, because the gain of JFET FET is higher, so this preposition microwave circuit can greatly improve the gain index of whole radio frequency photon chain-circuit system.

Two, noise factor

Because the noise factor of the preposition microwave circuit of the first order is NF ₁, the noise factor of partial radio frequency photon link is NF ₂So the noise factor NF of whole radio frequency photon chain-circuit system satisfies:

$\mathrm{NF}={\mathrm{<figure-callout\; id="1"\; label="NF"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">NF</figure-callout>}}_1+\frac{{\mathrm{NF}}_2}{G_1}---\left(1\right)$

Because the noise factor of JFET FET is very low; And it is higher to gain; So the noise factor of whole radio frequency photon chain-circuit system will be a little more than the preposition microwave circuit of the first order; And be far smaller than partial radio frequency photon link, therefore this preposition microwave circuit can greatly improve the noise factor of traditional analog photon link.

Three, third-order non-linear crosstalk

This preposition microwave circuit has also utilized the non-linear transmission characteristic of JFET FET except preparatory playing function, have predistortion function.

The predistortion function of this preposition microwave circuit mainly realizes through the non-linear transmission characteristic of JFET FET, can offset non-linear in the electrooptic modulation process, thereby reach the effect that suppresses the third-order non-linear intermodulation.

The transfer curve relation of JFET FET can be expressed as shown in Fig. 2 b:

$\begin{array}{cc}{i}_D=I_{\mathrm{DSS}}{(1-\frac{v_{\mathrm{GS}}}{V_P})}^2& (V_P\&le;v_{\mathrm{GS}}\&le;0)\end{array}---\left(2\right)$

I wherein _DCurrent drain current for the JFET FET; I _DSSBe saturated drain current; v _GSBeing gate source voltage, also is the applied signal voltage of whole system; V _PBe grid source pinch-off voltage.

If the JFET FET works in Class A mode of operation (Class A) pattern, then have the transfer function of preposition microwave circuit to satisfy:

$v_o=[I_{\mathrm{DC}}-I_{\mathrm{DSS}}{(1-\frac{v_{\mathrm{GS}}}{V_P})}^2]R_L$

$=I_{\mathrm{DC}}{R}_L-I_{\mathrm{DSS}}{R}_L+\frac{2I_{\mathrm{DSS}}{R}_L{v}_{\mathrm{GS}}}{V_P}-\frac{I_{\mathrm{DSS}}{R}_L{v}_{\mathrm{<figure-callout\; id="2V"\; label="GS"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">GS</figure-callout>}}^2}{V_P}---\left(3\right)$

V wherein _oBe the output voltage of preposition microwave circuit, I _DCBe the drain electrode direct voltage of JFET FET, R _LBe load resistance.With output voltage v _oAfter straight, obtain v _m, and:

$v_m=\frac{2I_{\mathrm{DSS}}{R}_L{v}_{\mathrm{GS}}}{V_P}-\frac{I_{\mathrm{DSS}}{R}_L{v}_{\mathrm{<figure-callout\; id="2V"\; label="GS"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">GS</figure-callout>}}^2}{V_P}=b_1{v}_{\mathrm{GS}}+b_2{v}_{\mathrm{GS}}^2---\left(4\right)$

Wherein ${\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_1=\frac{2I_{\mathrm{DSS}}{R}_L}{V_P},$ ${\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2=\frac{I_{\mathrm{DSS}}{R}_L}{V_P}.$

Radio frequency photon chain-circuit system of the present invention comprises laser, electrooptic modulator and detector; Suppose that the electrooptic modulator that the present invention adopts is the Mach-Zehnder intensity modulator; Detector is a direct detection, and the chain-circuit system structure is as shown in Figure 3, and the electrooptic modulator among Fig. 3 has rf input port and direct current biasing end; The radio frequency input is a signal input port, and direct current biasing is used for loading direct voltage.The transfer function of radio frequency photon link can be expressed as:

$I_{\mathrm{out}}=\mathrm{\&gamma;}{P}_{\mathrm{in}}[1+\cos \left(\frac{\mathrm{\&pi;}}{V_{\mathrm{\&pi;}}}(V_M+v_m)\right)]$

$=\mathrm{\&gamma;}{P}_{\mathrm{in}}[1-\frac{\mathrm{\&pi;}}{V_{\mathrm{\&pi;}}}\sin \left(\frac{\mathrm{\&pi;}}{V_{\mathrm{\&pi;}}}{V}_M\right)v_m-\frac{{\mathrm{\&pi;}}^2}{2V_{\mathrm{\&pi;}}^2}\cos \left(\frac{\mathrm{\&pi;}}{V_{\mathrm{\&pi;}}}{V}_M\right)v_{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">m</figure-callout>}}^2+\frac{{\mathrm{\&pi;}}^3}{6V_{\mathrm{\&pi;}}^3}\sin \left(\frac{\mathrm{\&pi;}}{V_{\mathrm{\&pi;}}}{V}_M\right)v_m^3]---\left(5\right)$

$=a_0+a_1{v}_m+a_2{v}_{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">m</figure-callout>}}^2+a_3{v}_m^3$

Wherein, I _OutBe the link output current, γ is the conversion efficiency of detector, P _InBe laser output power, V _πBe the half-wave voltage of electrooptic modulator, V _MBe the dc offset voltage of electrooptic modulator, v _mRadiofrequency signal voltage for input.In addition, a ₀=γ P _In, $a_1=\frac{\mathrm{\&pi;\; \&gamma;}{P}_{\mathrm{In}}}{V_{\mathrm{\&pi;}}}\mathrm{Sin}\left(\frac{\mathrm{\&pi;}}{V_{\mathrm{\&pi;}}}{V}_M\right),$ $a_2=-\frac{{\mathrm{\&pi;}}^2\mathrm{\&gamma;}{P}_{\mathrm{In}}}{2V_{\mathrm{\&pi;}}^2}\mathrm{Cos}\left(\frac{\mathrm{\&pi;}}{V_{\mathrm{\&pi;}}}{V}_M\right),$ $a_3=-\frac{{\mathrm{\&pi;}}^3\mathrm{\&gamma;}{P}_{\mathrm{In}}}{6V_{\mathrm{\&pi;}}^3}\mathrm{Cos}\left(\frac{\mathrm{\&pi;}}{V_{\mathrm{\&pi;}}}{V}_M\right).$ So total link transmission function satisfies:

$I_{\mathrm{out}}=a_0+a_1{v}_m+a_2{v}_{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">m</figure-callout>}}^2+a_3{v}_m^3$

$={\mathrm{<figure-callout\; id="0"\; label="a"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">a</figure-callout>}}_0+a_1(b_1{v}_{\mathrm{GS}}+b_2{v}_{\mathrm{GS}}^2)+a_2{(b_1{v}_{\mathrm{GS}}+b_2{v}_{\mathrm{GS}}^2)}^2+a_3{(b_1{v}_{\mathrm{GS}}+b_2{v}_{\mathrm{GS}}^2)}^3$ （6）

$={\mathrm{<figure-callout\; id="0"\; label="a"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">a</figure-callout>}}_0+a_1{b}_1{v}_{\mathrm{GS}}+(a_1{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2+a_2{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^2)v_{\mathrm{<figure-callout\; id="2"\; label="GS"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">GS</figure-callout>}}^2+({2a}_2{b}_1{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2+a_3{b}_1)v_{\mathrm{GS}}^3$

$+(a_2{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2^2+3a_1{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^2{b}_2)v_{\mathrm{<figure-callout\; id="4"\; label="GS"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">GS</figure-callout>}}^4+3a_3{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2^2{b}_1{v}_{\mathrm{<figure-callout\; id="5"\; label="GS"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">GS</figure-callout>}}^5+a_3{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2^3{v}_{\mathrm{<figure-callout\; id="6"\; label="GS"\; filenames="HDA00001799180800021.png"\; state="\{\{state\}\}">GS</figure-callout>}}^6$

Can find out from formula (6); Can eliminate the third order distortion item as long as satisfy relational expression

, promptly

$\tan \left(\frac{\mathrm{\&pi;}}{V_{\mathrm{\&pi;}}}{V}_M\right)=-\frac{3V_{\mathrm{\&pi;}}{I}_{\mathrm{DSS}}{R}_L}{\mathrm{\&pi;}{V}_P}$

Can reach a conclusion through above-mentioned analysis, preposition microwave circuit proposed by the invention can improve simultaneously gain, noise factor and the third-order non-linear crosstalk of radio frequency photon chain-circuit system effectively.

Can find out by above embodiment; The preposition microwave circuit that the present invention is based on the design of JFET FET is one with predistortion with preparatory playing function collection; Can improve the gain of chain-circuit system greatly; Noise-reduction coefficient, and through introducing the third-order non-linear distortion component that predistortion can suppress whole system.

The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from know-why of the present invention; Can also make some improvement and replacement, these improvement and replacement also should be regarded as protection scope of the present invention.

Claims (4)

1. a radio frequency photon chain-circuit system is characterized in that, comprises preposition microwave circuit and radio frequency photon link, and said radio frequency photon link comprises laser, Polarization Controller, electrooptic modulator and detector;

Said laser is used to produce light carrier;

Said Polarization Controller is connected between said laser and the electrooptic modulator, is used for being adjusted into the polarization state of the light carrier of laser output consistent with the main shaft of electrooptic modulator;

Said preposition microwave circuit is connected with said electrooptic modulator, is used for the input radio frequency signal that receives is amplified, and increases the modulation depth of said electrooptic modulator, and suppresses the third-order non-linear crosstalk of said radio frequency photon chain-circuit system;

Said electrooptic modulator is used for said input radio frequency signal is modulated to said light carrier;

Said detector is connected with said electrooptic modulator, is used for converting the light signal that obtains after the said electrooptic modulator modulation to the signal of telecommunication, to recover said input radio frequency signal.

2. the system of claim 1 is characterized in that, said preposition microwave circuit comprises the JFET FET, and the transfer characteristic curve of said JFET FET satisfies square law relationship.

3. system as claimed in claim 2 is characterized in that, said preposition microwave circuit also comprises: two inductance L 1, L2, two capacitor C 1, C2, two resistance R _S, R _L, wherein, the grid of said JFET FET connects an end of capacitor C 1 and an end of inductance L 1, and drain electrode connects an end of capacitor C 2 and an end of inductance L 2, source ground; The other end of said capacitor C 1 connects the source resistance R _SAn end, the source resistance R _SThe other end connect signal source V _InAn end, the other end ground connection of said signal source; The other end of capacitor C 2 connects load resistance R _LAn end, load resistance R _LOther end ground connection.

4. system as claimed in claim 3 is characterized in that, the other end of said inductance L 1 connects gate bias voltage V _Bias, the other end of said inductance L 2 connects drain electrode direct voltage V _Dc

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