CN104158610A - Modeling method for output response of receiver frequency mixer - Google Patents

Abstract

The invention discloses a modeling method for the output response of a receiver frequency mixer. The method comprises the following steps: (1) acquiring a local oscillation end signal, a radiofrequency end signal, a signal leaking from a local oscillation end to a medium-frequency end and a signal leaking from a radiofrequency end to the medium-frequency end of the frequency mixer; and (2) summing the product of the local oscillation end signal and the radiofrequency end signal, the signal leaking from the local oscillation end to the medium-frequency end and the signal leaking from the radiofrequency end to the medium-frequency end to obtain the output response of the receiver frequency mixer. Through adoption of the modeling method, the three nonlinear effect factors of the radiofrequency end negative gain transmission effect, a local oscillation end switching effect and a port-to-port coupling effect of the frequency mixer are considered comprehensively, the output response of the frequency mixer is obtained according to known quantities such as the performance parameter of the frequency mixer and an input signal, the nonlinear modeling accuracy of the frequency mixer is ensured, and the nonlinear output response characteristic of the receiver frequency mixer under an interference environment is predicted and computed accurately.

Description

Receiver mixer output response modeling method

Technical field

The invention belongs to electromagnetic interference prediction simulation technical field, be specifically related to a kind of receiver mixer output response modeling method, for calculating the output response characteristic of receiver mixer under interference environment.

Background technology

When the electronic equipment such as radar, communication is worked under interference environment, the frequency mixer of receiver, often in nonlinear response state, can produce more interfering frequency composition, affects the performance of late-class circuit.At present not yet there is clear and definite receiver mixer nonlinear response model, cannot accurately calculate the output response of frequency mixer under interference environment.For Accurate Prediction with calculate the non-linear response characteristic of receiver mixer under interference environment, need to set up can accurate description receiver mixer non-linear response characteristic computation model.Three kinds of build-in attributes that nonlinear effect factor is frequency mixer such as negative gain transmission, switching effect and port coupling effect, in the measured data of frequency mixer output response, there is embodiment, therefore, for assurance frequency mixer Nonlinear Modeling precision need be considered above-mentioned three kinds of nonlinear effect factors.

Summary of the invention

The technical problem to be solved in the present invention is, for existing receiver mixer response model above shortcomings, a kind of modeling method of receiver mixer output response is provided, this modeling method has considered three kinds of nonlinear effect factors such as the negative gain of frequency mixer transmission, switching effect and port coupling effect, can be used for calculating the output response of receiver mixer under interference environment.

The present invention solves the problems of the technologies described above adopted technical scheme to be:

The modeling method of receiver mixer output response, comprises the steps:

1) signal, the radio-frequency head that local oscillator end signal, radio-frequency head signal, the local oscillator end that obtains frequency mixer leaks into intermediate frequency end leaks into the signal of intermediate frequency end;

2) signal, the radio-frequency head that the product of local oscillator end signal and radio-frequency head signal, local oscillator end is leaked into intermediate frequency end leaks into the signal three summation of intermediate frequency end, obtains the output response of receiver mixer:

S _IF(t)＝S _LO(t)·S _RF(t)+S _LO-IF(t)+S _RF-IF(t) (1)

Wherein, S _iF(t) be the output response of receiver mixer, S _lO(t) be local oscillator end signal, S _rF(t) be radio-frequency head signal, S _lO-IF(t) for local oscillator end, leak into the signal of intermediate frequency end, S _rF-IF(t) for radio-frequency head, leak into the signal of intermediate frequency end.

Press such scheme, described local oscillator end shows as switching characteristic, local oscillator end signal S _lO(t) adopt odd harmonic multinomial model and get after 5 subharmonic block and be expressed as

$S_{\mathrm{LO}}\left(t\right)=A\·(\cos (2\mathrm{\π}\·f_{\mathrm{LO}}\·t)+\frac{1}{3}\·\cos (2\mathrm{\π}\·3f_{\mathrm{LO}}\·t)+\frac{1}{5}\·\cos (2\mathrm{\π}\·{5f}_{\mathrm{LO}}\·t))---\left(2\right)$

Wherein, f _lOfor local oscillator end signal frequency (f _lOas frequency mixer running parameter, by frequency mixer, device unit provides, known quantity), A is fundamental voltage amplitude, the relation table between fundamental voltage amplitude A and local oscillator end signal power is shown

$A=\sqrt{{2R}_L\·{10}^{{0.1P}_{\mathrm{dBm}}-3}}---\left(3\right)$

Wherein, P _dBmfor the local oscillator end signal power (P that adopts dBm form to represent _dBmknown quantity is provided by frequency mixer device unit as frequency mixer performance parameter), R _lfor load resistance.

Press such scheme, described radio-frequency head signal S _rF(t) for radio-frequency head negative gain output signal and local oscillator end, leak into the signal sum of radio-frequency head:

S _RF(t)＝y(t)+S _LO-RF(t) (4)

Wherein, y (t) is the negative gain of radio-frequency head output signal, S _lO-RF(t) for local oscillator end, leak into the signal of radio-frequency head;

(i) described radio-frequency head negative gain output signal y (t) adopts three rank multinomial models to calculate, and by the even-order component in three rank multinomial models through the filtering of rear class filter circuit, the expression formula that obtains three rank multinomial models is as follows:

y(t)≈a ₁x(t)+a ₃x ³(t) (5)

Wherein, x (t) is input signal, and a1 is the linear term coefficient of output signal y (t), and a1 is expressed as

a ₁＝10 ^G/20 (6)

Wherein, the negative gain of frequency mixer (G is provided by frequency mixer device unit as frequency mixer performance parameter, known quantity) that G represents for adopting dB form;

A ₃for the three rank item coefficients of output signal y (t), a ₃be expressed as

$a_3=-\frac{{{2a}_1}^3}{{3R}_L\·{10}^{{0.1P}_{I3}-3}}---\left(7\right)$

Wherein, P _i3for the third order intermodulation point (P that adopts dBm form to represent _i3as frequency mixer performance parameter, by frequency mixer device unit, provided known quantity);

(ii) described local oscillator end leaks into the signal S of radio-frequency head _lO-RF(t) be expressed as

$S_{\mathrm{LO}-\mathrm{RF}}\left(t\right)=S_{\mathrm{LO}}\left(t\right)/{10}^{{\mathrm{dB}}_{\mathrm{LO}-\mathrm{RF}}/20}---\left(8\right)$

DB wherein _lO-RFfor adopting local oscillator end that dB form represents to the degree of coupling (dB of radio-frequency head _lO-RFas frequency mixer performance parameter, by frequency mixer device unit, provided known quantity).

Press such scheme, described local oscillator end leaks into the signal S of intermediate frequency end _lO-IF(t) be expressed as

$S_{\mathrm{LO}-\mathrm{IF}}\left(t\right)=S_{\mathrm{LO}}\left(t\right)/{10}^{{\mathrm{dB}}_{\mathrm{LO}-\mathrm{IF}}/20}---\left(9\right)$

Wherein, dB _lO-IFfor adopting local oscillator end that dB form represents to the degree of coupling (dB of intermediate frequency end _lO-IFas frequency mixer performance parameter, by frequency mixer device unit, provided known quantity).

Press such scheme, described radio-frequency head leaks into the signal S of intermediate frequency end _rF-IF(t) be expressed as

$S_{\mathrm{RF}-\mathrm{IF}}\left(t\right)=S_{\mathrm{RF}}\left(t\right)/{10}^{{\mathrm{dB}}_{\mathrm{RF}-\mathrm{IF}}/20}---\left(10\right)$

DB wherein _rF-IFfor adopting radio-frequency head that dB form represents to the degree of coupling (dB of intermediate frequency end _rF-IFas frequency mixer performance parameter, by frequency mixer device unit, provided known quantity).

Operation principle of the present invention: according to above process, consider the nonlinear effects such as the negative gain of radio-frequency head transmission effects, local oscillator end switch effect and port effects of coupling between, by known quantities such as frequency mixer performance parameter, input signals, calculate frequency mixer output response.

Beneficial effect of the present invention is: this receiver mixer output response modeling method synthesis has been considered three kinds of nonlinear effect factors such as the negative gain of frequency mixer transmission, switching effect and port coupling effect, guarantee frequency mixer Nonlinear Modeling precision, Accurate Prediction and the non-linear output response characteristic of calculating receiver mixer under interference environment, improve late-class circuit performance.

Embodiment

Below in conjunction with embodiment, the present invention is described in detail.

Take certain receiver mixer as example, its important technological parameters: the negative gain G of frequency mixer is-6dB, third order intermodulation point P _i3for 30dBm, the local oscillator end degree of coupling dB to intermediate frequency end _lO-IFfor 20dB, the radio-frequency head degree of coupling dB to intermediate frequency end _rF-IFfor 20dB, the local oscillator end degree of coupling dB to radio-frequency head _lO-RFfor 30dB.Main input parameter: local oscillator end signal power P _dBmfor 30dBm, local oscillator end signal frequency f _lOfor 800MHz, load resistance R _lbe 50 Ω.

According to load resistance R _l, local oscillator end signal power P _dBmand formula (3) obtains fundamental voltage amplitude A=10;

According to fundamental voltage amplitude A, local oscillator end signal frequency f _lOand formula (2) obtains local oscillator end signal S _lO(t) be

$S_{\mathrm{LO}}\left(t\right)=10\·(\cos (2\mathrm{\π}\·800\·{10}^6\·t)+\frac{1}{3}\·\cos (2\mathrm{\π}\·3\·800\·{10}^6\·t)+\frac{1}{5}\·\cos (2\mathrm{\π}\·5\·800\·{10}^6\·t))---\left(11\right)$

According to the negative gain G of frequency mixer, load resistance R _l, third order intermodulation point P _i3and formula (4)～formula (7), obtain radio-frequency head signal S _rF(t) be

$S_{\mathrm{RF}}\left(t\right)={10}^{-0.3}\·x\left(t\right)-\frac{{2\·10}^{-0.9}}{150}\·x^3\left(t\right)+S_{\mathrm{LO}-\mathrm{RF}}\left(t\right)---\left(12\right)$

Degree of coupling dB according to local oscillator end to radio-frequency head _lO-RFand formula (8), obtain the signal S that local oscillator end leaks into radio-frequency head _lO-RF(t) be

S _LO-RF(t)＝S _LO(t)/10 ^-0.3 (13)

Degree of coupling dB according to local oscillator end to intermediate frequency end _lO-IFand formula (9), obtain the signal S that local oscillator end leaks into intermediate frequency end _lO-IF(t) be

S _LO-IF(t)＝S _LO(t)/10 (14)

Degree of coupling dB according to radio-frequency head to intermediate frequency end _rF-IFand formula (10), obtain the signal S that radio-frequency head leaks into intermediate frequency end _rF-IF(t) be

S _RF-IF(t)＝S _RF(t)/10 (15)

By equation (12)～equation (15) substitution equation (1), obtain the output response S of receiver mixer _iF(t) (be need in mixer response model solve intermediate frequency end signal) is

$S_{\mathrm{IF}}\left(t\right)=[S_{\mathrm{LO}}\left(t\right)+0.1]\·[{10}^{-0.3}\·x\left(t\right)-\frac{{2\·10}^{-0.9}}{150}\·x^3\left(t\right)+S_{\mathrm{LO}}\left(t\right)/{10}^{-0.3}]+S_{\mathrm{LO}}\left(t\right)/10---\left(16\right)$

Local oscillator end signal S _lO(t) be all known quantity with input signal x (t), can solve thus the output response S in formula (17) _iF(t).

For example, for input signal x (t), be as shown in the formula described typical linear FM signal:

$x\left(t\right)=\cos (2\mathrm{\πft}+\mathrm{\π}\frac{B}{\mathrm{\τ}}{t}^2)---\left(17\right)$

Wherein, the carrier frequency that f is input signal, the bandwidth that B is input signal, the pulse duration that τ is input signal;

According to equation (16), solve the output response S that obtains receiver mixer _iF(t).

Above-described is only preferred embodiment of the present invention, certainly can not limit with this interest field of the present invention, and the equivalence of therefore doing according to the present patent application the scope of the claims changes, and still belongs to protection scope of the present invention.

Claims (5)

1. the modeling method of receiver mixer output response, is characterized in that, comprises the steps:

1) signal, the radio-frequency head that local oscillator end signal, radio-frequency head signal, the local oscillator end that obtains frequency mixer leaks into intermediate frequency end leaks into the signal of intermediate frequency end;

2) signal, the radio-frequency head that the product of local oscillator end signal and radio-frequency head signal, local oscillator end is leaked into intermediate frequency end leaks into the signal three summation of intermediate frequency end, obtains the output response of receiver mixer:

S _IF(t)＝S _LO(t)·S _RF(t)+S _LO-IF(t)+S _RF-IF(t) (1)

Wherein, S _iF(t) be the output response of receiver mixer, S _lO(t) be local oscillator end signal, S _rF(t) be radio-frequency head signal, S _lO-IF(t) for local oscillator end, leak into the signal of intermediate frequency end, S _rF-IF(t) for radio-frequency head, leak into the signal of intermediate frequency end.

2. the modeling method of receiver mixer output response according to claim 1, is characterized in that described local oscillator end signal S _lO(t) adopt odd harmonic multinomial model and get after 5 subharmonic block and be expressed as

$S_{\mathrm{LO}}\left(t\right)=A\·(\cos (2\mathrm{\π}\·f_{\mathrm{LO}}\·t)+\frac{1}{3}\·\cos (2\mathrm{\π}\·3f_{\mathrm{LO}}\·t)+\frac{1}{5}\·\cos (2\mathrm{\π}\·{5f}_{\mathrm{LO}}\·t))---\left(2\right)$

Wherein, f _lOfor local oscillator end signal frequency, A is fundamental voltage amplitude, and the relation table between fundamental voltage amplitude A and local oscillator end signal power is shown

$A=\sqrt{{2R}_L\·{10}^{{0.1P}_{\mathrm{dBm}}-3}}---\left(3\right)$

Wherein, P _dBmfor the local oscillator end signal power that adopts dBm form to represent, R _lfor load resistance.

3. the modeling method of receiver mixer output response according to claim 1, is characterized in that described radio-frequency head signal S _rF(t) for radio-frequency head negative gain output signal and local oscillator end, leak into the signal sum of radio-frequency head:

S _RF(t)＝y(t)+S _LO-RF(t) (4)

Wherein, y (t) is the negative gain of radio-frequency head output signal, S _lO-RF(t) for local oscillator end, leak into the signal of radio-frequency head;

(i) described radio-frequency head negative gain output signal y (t) adopts three rank multinomial models to calculate, and by the even-order component in three rank multinomial models through the filtering of rear class filter circuit, the expression formula that obtains three rank multinomial models is as follows:

y(t)≈a ₁x(t)+a ₃x ³(t) (5)

Wherein, x (t) is input signal, a ₁for the linear term coefficient of output signal y (t), a ₁be expressed as

a ₁＝10 ^G/20 (6)

Wherein, the negative gain of frequency mixer that G represents for adopting dB form;

A ₃for the three rank item coefficients of output signal y (t), a ₃be expressed as

$a_3=-\frac{{{2a}_1}^3}{{3R}_L\·{10}^{{0.1P}_{I3}-3}}---\left(7\right)$

Wherein, P _i3for the third order intermodulation point that adopts dBm form to represent;

(ii) described local oscillator end leaks into the signal S of radio-frequency head _lO-RF(t) be expressed as

$S_{\mathrm{LO}-\mathrm{RF}}\left(t\right)=S_{\mathrm{LO}}\left(t\right)/{10}^{{\mathrm{dB}}_{\mathrm{LO}-\mathrm{RF}}/20}---\left(8\right)$

DB wherein _lO-RFfor adopting local oscillator end that dB form represents to the degree of coupling of radio-frequency head.

4. the modeling method of receiver mixer output response according to claim 1, is characterized in that, described local oscillator end leaks into the signal S of intermediate frequency end _lO-IF(t) be expressed as

$S_{\mathrm{LO}-\mathrm{IF}}\left(t\right)=S_{\mathrm{LO}}\left(t\right)/{10}^{{\mathrm{dB}}_{\mathrm{LO}-\mathrm{IF}}/20}---\left(9\right)$

Wherein, dB _lO-IFfor adopting local oscillator end that dB form represents to the degree of coupling of intermediate frequency end.

5. the modeling method of receiver mixer output response according to claim 1, is characterized in that, described radio-frequency head leaks into the signal S of intermediate frequency end _rF-IF(t) be expressed as

$S_{\mathrm{RF}-\mathrm{IF}}\left(t\right)=S_{\mathrm{RF}}\left(t\right)/{10}^{{\mathrm{dB}}_{\mathrm{RF}-\mathrm{IF}}/20}---\left(10\right)$

DB wherein _rF-IFfor adopting radio-frequency head that dB form represents to the degree of coupling of intermediate frequency end.