CN104883195A - Harmonic feedback based terahertz radar signal transmitter and transmitting method - Google Patents

Abstract

The invention discloses a harmonic feedback based terahertz radar signal transmitter and a transmitting method. The transmitter comprises a radar signal generation module, a clock control module, a digital pre-distortion module, a digital up-conversion module, a digital-to-analog conversion module, a frequency mixing module, a terahertz frequency multiplication and power amplification module, a harmonic feedback module and a radar antenna. The transmitting method disclosed by the invention comprises the steps of generating signals, initializing a nonlinear compensation weight coefficient, acquiring nonlinear compensation signals, acquiring digital radar intermediate frequency signals, acquiring radio frequency signals, carrying out frequency multiplication and amplification, acquiring the harmonic signal power, updating the nonlinear compensation weight coefficient and transmitting terahertz signals after power amplification. According to the invention, nonlinear compensation is carried out on base band digital linear frequency-modulated signals by adopting the harmonic feedback module and the digital pre-distortion module, and the performance of the terahertz radar signal transmitter is improved. A digital pre-distortion technology in harmonic feedback is realized by adopting a high-speed field programmable gate array.

Description

Based on Terahertz radar signal machine and the launching technique of feedback of harmonic

Technical field

The invention belongs to Terahertz Radar Technology field, further relate to a kind of Terahertz radar signal machine based on feedback of harmonic in Terahertz Radar Technology field and launching technique.The present invention adopts high-speed field programmable gate array (FieldProgrammable Gate Array, FPGA) digital pre-distortion technology of feedback of harmonic is realized, nonlinear distortion compensation is carried out to Terahertz radar emission signal, to solve the affined problem of Linear Amplifer scope of Terahertz radar signal machine intermediate power amplifier, and improve the performance of Terahertz radar signal machine.

Background technology

In Terahertz radar communications system, due to enough operating distance will be obtained, need the transmitting power increasing transmitter, thus cause the working point of power amplifier close to saturation region, this creates nonlinear distortion with regard to making the output signal of power amplifier, can cause composing expansion outside Terahertz radar signal inband distortion and band, reduce the performance of transmitter.

Power amplifier in Terahertz radar signal machine generally adopts Gunn diode, and the power output of Gunn diode can reach 50 milliwatts, but its delivery efficiency can only reach about 15%.The transmitting power of existing Terahertz radar signal machine is at least 10 milliwatts, the transmitting power reaching transmitter is difficult to after amplifying through multistage frequency multiplication, and the linear FM signal easily making transmitter produce produces nonlinear distortion, impact is to a certain degree brought on follow-up signal transacting.In this context, the research of the nonlinear compensation technology of Terahertz radar signal machine intermediate power amplifier is also received much concern, has become one of key technology of Terahertz radar signal machine.

A kind of device for compensation of distortion and power amplifier apparatus is disclosed in the patent " device for compensation of distortion and power amplifier apparatus " (number of patent application 200910002658.5, publication number CN101499781A) of Fujitsu Ltd.'s application.The main device of this patent application has: adaptive distortion compensation unit, adaptive equalizer, memory and control unit, and this device utilizes adaptive algorithm to carry out nonlinear compensation to nonlinear distortion circuit signal.The deficiency that equipment disclosed in this patent application and method exist is, the scope of signal being carried out to nonlinear compensation is less, its adaptive equalizer is realized by digital filter, and Terahertz radar signal is the signal of high-frequency large bandwidth, ordinary numbers filter is difficult to reach requirement, causes the digital pre-distortion system based on ordinary numbers circuit to be difficult to extensive use in the occasion of this high-frequency of Terahertz radar, large bandwidth signal transacting thus.

A kind of digital pre-distortion method based on feedback loop and device is disclosed in patent " a kind of pre-distortion method and apparatus " (number of patent application 201110075953.0, the publication number CN102271106A) of University of Electronic Science and Technology's application.The device of this patent application comprises pretreatment unit, main pre-distortion unit, Corticofugal Modulation of Somatosensory link, power amplifier, feedback loop, also comprise main pre-distortion unit diverter switch, power amplifier diverter switch, control unit, main pre-distortion unit diverter switch and the parallel connection of main pre-distortion unit, power amplifier diverter switch is in parallel with power amplifier, and feedback loop is in series by uplink demodulation link and secondary pre-distortion unit.The method of this patent application, by adding pre-distortion in the feedback loop, makes feedback signal be compensated, and eliminates the distortion that feedback loop causes.The deficiency that equipment disclosed in this patent application and method exist is, the hardware circuit that is connected with power amplifier realizes relatively complicated, the transmitting power requirement of Terahertz radar signal machine can not be reached, treatable signal bandwidth is large not, and radar linear frequency-modulated signal is carried out to the DeGrain of nonlinear compensation, nonlinear distortion caused in Terahertz radar signal machine is still obvious to follow-up signal transacting.

Summary of the invention

For above-mentioned the deficiencies in the prior art, the object of the invention is to propose the Terahertz radar signal machine based on feedback of harmonic and launching technique, the present invention adopts high-speed field programmable gate array (Field Programmable Gate Array, FPGA) realize the digital pre-distortion technology of feedback of harmonic, the nonlinear compensation to Terahertz radar signal machine intermediate power amplifier can be realized.

For reaching above-mentioned technical purpose, the present invention adopts following technical scheme to be achieved.

Technical scheme one:

A kind of Terahertz radar signal machine based on feedback of harmonic, it is characterized in that, comprising: radar signal generation module, clock control module, digital pre-distortion block, Digital Up Convert module, D/A converter module, frequency mixing module, Terahertz double frequency power amplification module, feedback of harmonic module and radar antenna; Connected by bus between each module; Wherein,

Described radar signal generation module, for generation of base-band digital linear FM signal, carries out data low-pass filtering to it; And produce local oscillation signal;

Described clock control module, for generation of the fixing clock cycle, controls the input and output of base-band digital linear FM signal;

Described digital pre-distortion block, for carrying out nonlinear compensation to the base-band digital linear FM signal after low-pass filtering, obtains nonlinear compensation signal;

Described Digital Up Convert module, for the signal by the frequency of nonlinear compensation signal being transferred to high one-level frequency range, obtains digital radar intermediate-freuqncy signal;

Described D/A converter module, for converting digital radar intermediate-freuqncy signal to analog linearity FM signal;

Described frequency mixing module, for modulating the centre frequency of analog linearity FM signal, obtains radiofrequency signal;

Described Terahertz double frequency power amplification module, for radiofrequency signal is carried out multistage frequency multiplication and power amplification, obtains the Terahertz radar signal after power amplification;

Described feedback of harmonic module, for extracting the harmonic signal in the Terahertz radar signal after power amplification, and feeds back to digital pre-distortion block by harmonic signal power;

Described radar antenna, the Terahertz radar signal after amplifying for transmitting power.

Technical scheme two:

Based on a Terahertz radar signal method for feedback of harmonic, based on the above-mentioned Terahertz radar signal machine based on feedback of harmonic, it is characterized in that, comprise the following steps:

(1) signal is produced:

1a) the base-band digital linear FM signal that radar signal generation module generates is carried out digital low-pass filtering, obtain the base-band digital linear FM signal after low-pass filtering;

1b) under the control of clock control module, digital pre-distortion block receives the base-band digital linear FM signal after low-pass filtering, to the baseband frequency spectrum data of the base-band digital linear FM signal after low-pass filtering, i.e. base band quadrature digital signal, carry out twice extraction, obtain the solid part signal of base band quadrature digital signal and the imaginary signals of base band quadrature digital signal respectively.

(2) initialization nonlinear compensation weight coefficient:

2a) calculate initialized nonlinear compensation weight coefficient, sent into weight coefficient update module;

2b) initialized nonlinear compensation weight coefficient is transferred to digital pre-distortion computing module by weight coefficient update module.

(3) nonlinear compensation signal is obtained:

3a) data predistortion computing module is using the data of the imaginary signals of the solid part signal and base band quadrature digital signal that receive base band quadrature digital signal as first passage;

3b) under the control of clock control module, the data of first passage are obtained the data of second passage through a clock cycle time delay, the data of second passage obtain the data of the 3rd passage through a clock cycle time delay, the data of the 3rd passage obtain the data of the 4th passage through a clock cycle time delay, the data of the 4th passage obtain the data of the 5th passage through a clock cycle time delay;

3c) under the control of clock control module, according to the following formula, the data of 5 passage precompensations are obtained:

$x_m\left(n\right)=\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{\left|x(n-m+1)\right|}^{2(k-1)}{w}_{\mathrm{mk}}$

Wherein, x _mn () represents the data of m passage precompensation in five passages, n represents the sampling number of the base-band digital linear FM signal that radar signal generation module generates, x (n-m+1) represents the data of m passage in five passages, K represents the total degree compensated m channel data, K be more than or equal to 3 positive integer, w _mkrepresent and carry out the secondary weight coefficient compensated of kth to m passage in five passages, k span is the positive integer between 1 ~ K, || represent and modulo operation is asked to data;

3d) under the control of clock control module, according to the following formula, the offset data of 5 passages is obtained:

y _m(n)＝x(n-m+1)x _m(n)

Wherein, y _mn () represents the offset data of m passage in five passages, n represents the sampling number of the base-band digital linear FM signal that radar signal generation module generates, and x (n-m+1) represents the data of m passage in five passages, x _mn () represents the data of m passage precompensation in five passages;

3e) under the control of clock control module, according to the following formula, nonlinear compensation signal is obtained:

$y\left(n\right)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{y}_m\left(n\right)$

Wherein, y (n) represents nonlinear compensation signal, and n represents the sampling number of the base-band digital linear FM signal that radar signal generation module generates, and M represents the total number of passage.

(4) digital radar intermediate-freuqncy signal is obtained:

4a) under the control of clock control module, nonlinear compensation signal is delivered to multiphase filtering module by digital pre-distortion block; Multiphase filtering module, to the nonlinear compensation signal received, carries out multiphase filtering operation, obtains two-forty signal; Again twice extraction is carried out to two-forty signal, obtain imaginary signals and the solid part signal of two-forty signal;

4b) under the control of clock control module, half-phase filtration module receives the imaginary signals of two-forty signal, carries out low-pass filtering, obtain the imaginary signals of filtered two-forty signal to it;

4c) under the control of clock control module, shift module receives the solid part signal of two-forty signal, and carried out right shift, the figure place of displacement is the figure place of the imaginary signals of two-forty signal, obtains the solid part signal of the two-forty signal after being shifted;

4d) under the control of clock control module, by the solid part signal of the two-forty signal after the imaginary signals of filtered two-forty signal and displacement, be transferred to the digital quadrature transformation inverse process module; The solid part signal of the two-forty signal after displacement is multiplied by-1 by the digital quadrature transformation inverse process module, is added, obtains the digital radar linear FM signal of two-forty with the imaginary signals of filtered two-forty signal;

4e) under the control of clock control module, the digital radar linear FM signal of two-forty is delivered to binary code modular converter, obtains digital radar intermediate-freuqncy signal.

(5) radiofrequency signal is obtained:

5a) D/A converter module is by digital radar intermediate-freuqncy signal, is converted into analog linearity FM signal through D/A converter;

5b) analog linearity FM signal and local oscillation signal are carried out mixing by frequency mixing module, obtain radiofrequency signal.

(6) frequency multiplication is amplified:

6a) radiofrequency signal is delivered to frequency multiplier module, obtain Terahertz radar signal;

6b) Terahertz radar signal is delivered to the power amplifier module in Terahertz double frequency power amplification module, obtain Terahertz radar signal z (t) after power amplification.

(7) harmonic signal power is obtained:

7a) Terahertz radar signal z (t) after power amplification is delivered to harmonic filter module, obtain harmonic signal;

7b) harmonic signal is delivered to the power amplifier module in feedback of harmonic module, obtain the harmonic signal after power amplification;

7c) harmonic signal after power amplification is delivered to integrator module, obtain harmonic signal power.

(8) nonlinear compensation weight coefficient is upgraded:

8a) harmonic signal power is fed back to weight coefficient update module, calculate the nonlinear compensation weight coefficient upgraded according to harmonic signal power;

8b) the nonlinear compensation weight coefficient of the renewal calculated is delivered to digital pre-distortion computing module by weight coefficient update module.

(9) the Terahertz radar signal after transmitting power amplification:

Terahertz radar signal after the amplification of radar antenna transmitting power.

The present invention compared with prior art has the following advantages:

First, feedback of harmonic module is incorporated in Terahertz radar signal machine by the present invention, improve the nonlinearity compensation precision of digital pre-distortion block to Terahertz radar emission signal, considerably increase the power of the output signal of Terahertz radar signal machine.

3rd, method of the present invention adopts high-speed field programmable gate array to realize the digital pre-distortion technology of feedback of harmonic, nonlinear compensation is carried out to base-band digital linear FM signal, improve the effective bandwidth of base-band digital linear FM signal, overcome in prior art the shortcoming that the bandwidth that exists when processing base-band digital linear FM signal is low.

Accompanying drawing explanation

Illustrate below in conjunction with accompanying drawing and with embodiment, the present invention to be described in further detail.

Fig. 1 is Terahertz radar signal machine frame figure of the present invention;

Fig. 2 is the flow chart of Terahertz radar signal method of the present invention;

Fig. 3 is the schematic diagram of the digital pre-distortion step in Terahertz radar signal method of the present invention;

Fig. 4 is the schematic diagram of the multiphase filtering operating procedure in Terahertz radar signal method of the present invention.

Embodiment

With reference to accompanying drawing 1, Terahertz radar signal machine based on feedback of harmonic of the present invention, comprises radar signal generation module, clock control module, digital pre-distortion block, Digital Up Convert module, D/A converter module, frequency mixing module, Terahertz double frequency power amplification module, feedback of harmonic module and radar antenna; Wherein,

Radar signal generation module, for generating base-band digital linear FM signal by frequency source signal generator, and carrying out digital low-pass filtering by base-band digital linear FM signal, obtaining the base-band digital linear FM signal after low-pass filtering; By base-band digital linear FM signal through digital-to-analogue conversion and process of frequency multiplication, obtain local oscillation signal.In example of the present invention, frequency source signal generator adopts Direct Digital Synthesizer (Direct Digital Synthesizer, DDS); The centre frequency of local oscillation signal is 20GHz.

Clock control module, for designing the clock cycle, controls the input and output of base-band digital linear FM signal.In example of the present invention, clock control module realizes in fpga chip.

Digital pre-distortion block, for carrying out nonlinear compensation to the base-band digital linear FM signal after low-pass filtering; Comprise weight coefficient update module and digital pre-distortion computing module; Weight coefficient update module provides nonlinear compensation weight coefficient to the base-band digital linear FM signal after low-pass filtering, upgrades nonlinear compensation weight coefficient for dynamic realtime; The data that digital pre-distortion computing module produces for receiving, processing base-band digital linear FM signal after low-pass filtering and weight coefficient update module, obtain nonlinear compensation signal, realize the nonlinear compensation of the base-band digital linear FM signal after to low-pass filtering.In example of the present invention, digital pre-distortion block realizes in FRGA chip.

Digital Up Convert module, for the signal by the frequency of nonlinear compensation signal being transferred to high one-level frequency range, obtains digital radar intermediate-freuqncy signal; Comprise multiphase filtering module, half-phase filtration module, shift module, the digital quadrature transformation inverse process module and binary code modular converter; Multiphase filtering module is used for carrying out multiphase filtering operation to nonlinear compensation signal, obtains two-forty signal, and carries out twice extraction to two-forty signal, obtain the solid part signal of two-forty signal and the imaginary signals of two-forty signal; Half-phase filtration module is used for the imaginary signals of two-forty signal to carry out low-pass filtering, obtains the imaginary signals of filtered two-forty signal; Shift module is used for the solid part signal of two-forty signal to move right, and the figure place of movement is the figure place of the imaginary signals of two-forty signal, obtains the solid part signal of the two-forty signal after being shifted; The solid part signal that the digital quadrature transformation inverse process module is used for the two-forty signal after by displacement is multiplied by-1, is added, obtains the digital radar linear FM signal of two-forty with the imaginary signals of filtered two-forty signal; Binary code modular converter is used for the digital radar linear FM signal of two-forty to be converted into data without sign, obtains digital radar intermediate-freuqncy signal.In example of the present invention, binary code modular converter adopts conversion chip 8192 to realize.

D/A converter module, for converting digital radar intermediate-freuqncy signal to analog linearity FM signal, realizes digital-to-analogue conversion.

Frequency mixing module, for modulating the centre frequency of analog linearity FM signal, obtains radiofrequency signal.

Terahertz double frequency power amplification module, for radiofrequency signal is carried out multistage frequency multiplication and power amplification, obtains the Terahertz radar signal after power amplification; Comprise frequency multiplier module and power amplifier module; Frequency multiplier module is used for the frequency of radiofrequency signal to carry out six times of amplifications, obtains Terahertz radar signal; The power amplifier module of Terahertz double frequency power amplification module, for increasing the power of Terahertz radar signal, obtains the Terahertz radar signal after power amplification.

Feedback of harmonic module, for extracting harmonic signal from the Terahertz radar signal after power amplification, and feeds back to digital pre-distortion block by harmonic signal power; Comprise harmonic filter module, power amplifier module sum-product intergrator module; Harmonic filter module is used for extracting harmonic signal from Terahertz radar signal; The power amplifier module of feedback of harmonic module, for increasing the power of harmonic signal, obtains the harmonic signal after power amplification; Integrator module is for obtaining the power of harmonic signal.In example of the present invention, feedback of harmonic module realizes in FRGA chip.

Radar antenna, the Terahertz radar signal after amplifying for transmitting power.

With reference to accompanying drawing 2, the Terahertz radar signal method based on feedback of harmonic of the present invention, its concrete steps are as follows:

Step 1, produces signal.

Radar signal generation module is modulated by frequency source signal generator and is produced base-band digital linear FM signal, and base-band digital linear FM signal is carried out digital low-pass filtering, obtains the base-band digital linear FM signal after low-pass filtering.In example of the present invention, the frequency of base-band digital linear FM signal is 360MHz.

Digital pre-distortion block receives the base-band digital linear FM signal after low-pass filtering, under the control of clock control module, twice extraction is carried out to the baseband frequency spectrum data of the base-band digital linear FM signal after low-pass filtering, obtain the solid part signal of base band quadrature digital signal and the imaginary signals of base band quadrature digital signal respectively.

Step 2, initialization nonlinear compensation weight coefficient.

By optimized method, calculate the initialized nonlinear compensation weight coefficient matched with base band quadrature digital signal, be delivered to weight coefficient update module, the data in initialization weight coefficient update module; Initialized nonlinear compensation weight coefficient is transferred to digital pre-distortion computing module by data/address bus by weight coefficient update module.

Step 3, obtains nonlinear compensation signal.

In reference Fig. 3, Fig. 3 symbol represents that nonlinear compensation weight coefficient is multiplied with channel data, symbol represents that different channel data is added.The concrete steps obtaining nonlinear compensation signal are as follows:

The first step, data predistortion computing module is using the solid part signal of base band quadrature digital signal that received and the imaginary signals of the base band quadrature digital signal data x (n) as first passage.

Second step, under the control of clock control module, the data of first passage are obtained the data x (n-1) of second passage through a clock cycle time delay, the data of second passage obtain the data x (n-2) of the 3rd passage through a clock cycle time delay, the data of the 3rd passage obtain the data x (n-3) of the 4th passage through a clock cycle time delay, the data of the 4th passage obtain the data x (n-4) of the 5th passage through a clock cycle time delay.

3rd step, under the control of clock control module, according to the following formula, obtains the data of 5 passage precompensations:

$x_m\left(n\right)=\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{\left|x(n-m+1)\right|}^{2(k-1)}{w}_{\mathrm{mk}}$

Wherein, x _mn () represents the data of m passage precompensation in five passages, n represents the sampling number of the base-band digital linear FM signal that radar signal generation module generates, and x (n-m+1) represents the data of m passage in five passages; K represents the total degree compensated m channel data, K be more than or equal to 3 positive integer, in example of the present invention, K value is 5; w _mkrepresent and carry out the secondary weight coefficient compensated of kth to m passage in five passages, k span is the positive integer between 1 ~ K, and in example of the present invention, k gets the positive integer between 1 ~ 5; || represent and modulo operation is asked to data.

4th step, under the control of clock control module, according to the following formula, obtains the offset data of 5 passages:

y _m(n)＝x(n-m+1)x _m(n)

Wherein, y _mn () represents the offset data of m passage in five passages, n represents the sampling number of the base-band digital linear FM signal that radar signal generation module generates, and x (n-m+1) represents the data of m passage in five passages, x _mn () represents the data of m passage precompensation in five passages.

Particularly, in example of the present invention, for the data x (n) of first passage, by the weight coefficient w that the data x (n) of first passage compensates for the first time with this channel data ₁₁be multiplied, obtain the data of first unit of first passage; The data delivery of first passage is asked square | x (n) | ², the weight coefficient w compensated with this channel data second time ₁₂be multiplied, obtain the data of second unit of first passage; Biquadratic is asked to obtain the data delivery of first passage | x (n) | ⁴, the weight coefficient w compensated with this channel data third time ₁₃be multiplied, obtain the data of the 3rd unit of first passage; Six powers are asked to obtain the data delivery of first passage | x (n) | ⁶, the weight coefficient w compensated for the 4th time with this channel data ₁₄be multiplied, obtain the data of the 4th unit of first passage; Eight power is asked to obtain the data delivery of first passage | x (n) | ⁸, the weight coefficient w compensated for the 4th time with this channel data ₁₅be multiplied, obtain the data of the 5th unit of first passage; The data of five unit of above-mentioned first passage are sued for peace, obtains the data y of first passage precompensation ₁(n).The data of other four passages are carried out above-mentioned respective operations respectively, obtains the data of other four passage precompensations.

5th step, under the control of clock control module, according to the following formula, obtains nonlinear compensation signal:

$y\left(n\right)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{y}_m\left(n\right)$

Wherein, y (n) represents nonlinear compensation signal, and in example of the present invention, the frequency of y (n) is 360MHz; N represents the sampling number of the base-band digital linear FM signal that radar signal generation module generates, and M represents the total number of passage.

Step 4, obtains digital radar intermediate-freuqncy signal.

Under the control of clock control module, nonlinear compensation signal transmission to multiphase filtering module, is carried out multiphase filtering operation by digital pre-distortion block, obtains two-forty signal.In reference Fig. 4, Fig. 4 symbol table registration is according to addition, ↓ 2 symbols represent and carry out 2 haplotype data extractions to nonlinear compensation signal, ↑ 3 symbols represent and carry out 3 haplotype data interpolations to nonlinear compensation signal, there is limit for length's unit impulse response (Finite Impulse Response, FIR) to represent and low-pass filtering is carried out to nonlinear compensation signal.The concrete steps of described multiphase filtering operation are as follows:

The first step, is evenly divided into six groups of identical subsignals of sampling number by nonlinear compensation signal;

Second step, proceeds as follows under the control of clock control module:

A clock cycle of time delay and z are carried out successively to first group, the 4th group and the 6th group of nonlinear compensation subsignal ^-1, 2 haplotype datas extract, FIR low-pass filtering and 3 haplotype data interpolating operations, obtain the signal of first group, the 4th group and the 6th group two-forty;

2 haplotype data extractions are carried out successively to second group, the 3rd group nonlinear compensation subsignal, FIR low pass filtered involves 3 haplotype data interpolating operations, obtain the signal of second group, the 3rd group two-forty;

2 haplotype data extractions, FIR low-pass filtering, 3 haplotype data interpolations and three clock cycle of time delay and z are carried out successively to the 5th group of nonlinear compensation subsignal ^-3operation, obtain the signal of the 5th group of two-forty.

3rd step, sues for peace the signal of the signal of first group of two-forty and second group of two-forty, by the clock cycle of signal delay after summation and z ^-1, obtain first via high-rate linear FM signal;

4th step, sues for peace the signal of the signal of the 3rd group of two-forty and the 4th group of two-forty, by two clock cycle of signal delay after summation and z ^-2, obtain the second road high-rate linear FM signal;

5th step, sues for peace the signal of the signal of the 5th group of two-forty and the 6th group of two-forty, obtains the 3rd road high-rate linear FM signal;

6th step, by the three road high-rate linear FM signal summations obtained, obtain two-forty signal, in example of the present invention, the frequency of two-forty signal is 540MHz.

Twice extraction is carried out to two-forty signal, obtains the imaginary signals of two-forty signal and the solid part signal of two-forty signal.

Under the control of clock control module, half-phase filtration module receives the imaginary signals of two-forty signal, carries out low-pass filtering, obtain the imaginary signals of filtered two-forty signal to it.Shift module receives the solid part signal of two-forty signal, and carried out right shift, the figure place of displacement is the figure place of the imaginary signals of two-forty signal, obtains the solid part signal of the two-forty signal after being shifted.

Under the control of clock control module, by the solid part signal of the two-forty signal after the imaginary signals of filtered two-forty signal and displacement, be transferred to the digital quadrature transformation inverse process module, the solid part signal of the two-forty signal after this module is just shifted is multiplied by-1, be added with the imaginary signals of filtered two-forty signal, obtain the digital radar linear FM signal of two-forty, in example of the present invention, the frequency of the digital radar linear FM signal of two-forty is 1080MHz; The digital radar linear FM signal of two-forty is converted into data without sign by binary code modular converter, obtains digital radar intermediate-freuqncy signal, and in example of the present invention, binary code modular converter adopts conversion chip 8192 to realize.

Step 5, obtains radiofrequency signal.

Digital radar intermediate-freuqncy signal is converted into analog linearity FM signal through D/A converter by D/A converter module; The local oscillation signal that itself and radar signal generation module produce is carried out mixing by frequency mixing module, obtains radiofrequency signal.

Step 6, frequency multiplication is amplified.

Radiofrequency signal is delivered to successively the honest and just formula diode of the (frequency) tripler module in Terahertz double frequency power amplification module, power amplifier module, obtain if radar signal; If radar signal delivers to the honest and just formula diode of twice frequency multiplier module in Terahertz double frequency power amplification module and power amplifier module successively, the frequency of radio frequency signal carries out six times of amplifications, obtains Terahertz radar signal z (t) after power amplification.

Step 7, obtains harmonic signal power.

Terahertz radar signal z (t) after power amplification is delivered to harmonic filter module, obtains harmonic signal; Because harmonic signal power is more weak, therefore first harmonic signal is delivered to the power amplifier module in feedback of harmonic module, obtain the harmonic signal after power amplification; Again the harmonic signal after power amplification is delivered to integrator module, obtain harmonic signal power.

Step 8, upgrades nonlinear compensation weight coefficient.

Harmonic signal power is fed back to weight coefficient update module, calculate the nonlinear compensation weight coefficient upgraded according to harmonic signal power; The nonlinear compensation weight coefficient of the renewal calculated is delivered to digital pre-distortion computing module by weight coefficient update module.

Wherein, the process calculating the nonlinear compensation weight coefficient upgraded according to harmonic signal power is: according to the desirable input/output signal power curve of the power amplifier in Terahertz double frequency power amplification module, if harmonic signal power is less than rated value, illustrate that Terahertz radar signal z (t) after power amplification exists nonlinear distortion, then carry out operation below:

The first step, obtains Terahertz radar digital signal z (n) by Terahertz radar signal z (t) discretization after power amplification;

Second step, the nonlinear compensation weight coefficient vector W of definition weight coefficient update module and training vector thereof be respectively

W＝[w ₁₁,w ₁₂,…w _1K,w ₂₁,…w _MK]

$\tilde{W}=[{\tilde{w}}_{11},{\tilde{w}}_{12},...{\tilde{w}}_{1K},{\tilde{w}}_{21},...{\tilde{w}}_{\mathrm{MK}}]$

Wherein, M represents the total number of passage, and K represents the total degree compensated m channel data, K be more than or equal to 3 positive integer;

3rd step, the data x (n) of definition first passage and the matrix of time delayed signal composition thereof are X _n, the matrix that definition Terahertz radar digital signal z (n) and time delayed signal thereof form is Z _n,

$X_n=\left(\begin{array}{c}x\left(n\right)\\ x(n-1)\\ \·\\ \·\\ \·\\ x(n-M+1)\\ x\left(n\right)\left|x\left(n\right)\right|\\ \·\\ \·\\ \·\\ x(n-M+1){\left|x(n-M+1)\right|}^{2(K-1)}\end{array}\right)$

$Z_n=\left(\begin{array}{c}z\left(n\right)\\ z(n-1)\\ \·\\ \·\\ \·\\ z(n-M+1)\\ z\left(n\right)\left|z\left(n\right)\right|\\ \·\\ \·\\ \·\\ z(n-M+1){\left|z(n-M+1)\right|}^{2(K-1)}\end{array}\right);$

4th step, definition error signal e (n) is

$e\left(n\right)=y\left(n\right)-\tilde{y}\left(n\right)=W{X}_n-\tilde{W}{Z}_n$

Wherein, nonlinear compensation signal y (n) and training signal thereof be respectively

y(n)＝WX _n

$\tilde{y}\left(n\right)=\tilde{W}{Z}_n;$

5th step, carries out iteration by recurrence least square adaptive algorithm, calculates the training vector of weight coefficient update module the iteration ends when error signal e (n) meets the demands, and will assignment, to W, obtains the nonlinear compensation weight coefficient upgraded;

P (n) is the inverse matrix of data x (n) autocorrelation matrix of first passage, and setting its initial value is P ⁰(n); The training nonlinear weight coefficient vector of setting weight coefficient update module initial value be

Make as l is iterations, will assignment is to W ^l, iterative formula is

$e^l\left(n\right)={\tilde{W}}^l(X_n-Z_n)$

$K^{l+1}\left(n\right)=\frac{P^l\left(n\right)Z_n}{\mathrm{\λ}+Z_n^H{P}^l\left(n\right)Z_n}$

$P^{l+1}\left(n\right)=\frac{P^l\left(n\right)-K^{l+1}\left(n\right)Z_n^H{P}^l\left(n\right)}{\mathrm{\λ}}$

${\tilde{W}}^{l+1}\left(n\right)={\tilde{W}}^l\left(n\right){+K}^{l+1}\left(n\right){\left(e^l\left(n\right)\right)}^{*}$

Wherein, K (n) represents gain vector, () ^hrepresent and ask hermitian matrix, () ^*represent and ask conjugate matrices, constant λ is forgetting factor, and 0 < λ < 1.

Step 9, the terahertz signal after transmitting power amplification.

Terahertz radar signal after the amplification of radar antenna transmitting power.

Terahertz radar signal machine based on feedback of harmonic of the present invention and launching technique, adopt high-speed field programmable gate array (Field Programmable Gate Array, FPGA) realize the digital pre-distortion technology of feedback of harmonic, the nonlinear compensation to Terahertz radar signal machine intermediate power amplifier can be realized.

Claims (8)

1., based on a Terahertz radar signal machine for feedback of harmonic, comprise radar signal generation module, clock control module, digital pre-distortion block, Digital Up Convert module, D/A converter module, frequency mixing module, Terahertz double frequency power amplification module, feedback of harmonic module and radar antenna; Connected by bus between each module;

Described radar signal generation module, for generation of base-band digital linear FM signal, carries out data low-pass filtering to it; And produce local oscillation signal;

Described clock control module, for generation of the fixing clock cycle, controls the input and output of base-band digital linear FM signal;

Described digital pre-distortion block, for carrying out nonlinear compensation to the base-band digital linear FM signal after low-pass filtering, obtains nonlinear compensation signal;

Described Digital Up Convert module, for the signal by the frequency of nonlinear compensation signal being transferred to high one-level frequency range, obtains digital radar intermediate-freuqncy signal;

Described D/A converter module, for converting digital radar intermediate-freuqncy signal to analog linearity FM signal;

Described frequency mixing module, for modulating the centre frequency of analog linearity FM signal, obtains radiofrequency signal;

Described Terahertz double frequency power amplification module, for radiofrequency signal is carried out multistage frequency multiplication and power amplification, obtains the Terahertz radar signal after power amplification;

Described feedback of harmonic module, for extracting the harmonic signal in the Terahertz radar signal after power amplification, and feeds back to digital pre-distortion block by harmonic signal power;

Described radar antenna, the Terahertz radar signal after amplifying for transmitting power.

2. the Terahertz radar signal machine based on feedback of harmonic according to claim 1, it is characterized in that, described digital pre-distortion block comprises weight coefficient update module and digital pre-distortion computing module; Wherein,

Described weight coefficient update module, for receiving the harmonic signal power of feedback of harmonic module feedback, and according to harmonic signal power real-time update nonlinear compensation weight coefficient, for the base-band digital linear FM signal after low-pass filtering provides optimum nonlinear compensation weight coefficient;

Described digital pre-distortion computing module, for receiving, processing the data that base-band digital linear FM signal after low-pass filtering and weight coefficient update module produce, obtains nonlinear compensation signal, realizes the nonlinear compensation to base-band digital linear FM signal.

3. the Terahertz radar signal machine based on feedback of harmonic according to claim 1, it is characterized in that, described Digital Up Convert module comprises multiphase filtering module, half-phase filtration module, shift module, the digital quadrature transformation inverse process module and binary code modular converter; Wherein,

Described multiphase filtering module, for carrying out multiphase filtering operation to nonlinear compensation signal, obtains two-forty signal, and carries out twice extraction to two-forty signal, obtains the solid part signal of two-forty signal and the imaginary signals of two-forty signal;

Described half-phase filtration module, for the imaginary signals of two-forty signal is carried out low-pass filtering, obtains the imaginary signals of filtered two-forty signal;

Described shift module, for being moved right by the solid part signal of two-forty signal, the figure place of movement is the figure place of the imaginary signals of two-forty signal, obtains the solid part signal of the two-forty signal after being shifted;

Described the digital quadrature transformation inverse process module, for the solid part signal of the two-forty signal after displacement is multiplied by-1, is added with the imaginary signals of filtered two-forty signal, obtains the digital radar linear FM signal of two-forty;

Described binary code modular converter, for the digital radar linear FM signal of two-forty is converted into data without sign, obtains digital radar intermediate-freuqncy signal.

4. the Terahertz radar signal machine based on feedback of harmonic according to claim 1, is characterized in that, described Terahertz double frequency power amplification module comprises frequency multiplier module and power amplifier module; Wherein,

Described frequency multiplier module, for the frequency of radiofrequency signal being carried out six times of amplifications, obtains Terahertz radar signal;

Described power amplifier module, for increasing the power of Terahertz radar signal, obtains the Terahertz radar signal after power amplification.

5. the Terahertz radar signal machine based on feedback of harmonic according to claim 1, is characterized in that, described feedback of harmonic module comprises harmonic filter module, power amplifier module sum-product intergrator module; Wherein,

Described harmonic filter module, for extracting harmonic signal from the Terahertz radar signal after power amplification;

Described power amplifier module, for increasing the power of harmonic signal, obtains the harmonic signal after power amplification;

Described integrator module, for obtaining harmonic signal power.

6., based on a Terahertz radar signal method for feedback of harmonic, comprise the steps:

(1) signal is produced:

1a) the base-band digital linear FM signal that radar signal generation module generates is carried out digital low-pass filtering, obtain the base-band digital linear FM signal after low-pass filtering;

1b) under the control of clock control module, digital pre-distortion block receives the base-band digital linear FM signal after low-pass filtering, to the baseband frequency spectrum data of the base-band digital linear FM signal after low-pass filtering, i.e. base band quadrature digital signal, carry out twice extraction, obtain the solid part signal of base band quadrature digital signal and the imaginary signals of base band quadrature digital signal respectively;

(2) initialization nonlinear compensation weight coefficient:

2a) calculate initialized nonlinear compensation weight coefficient, sent into weight coefficient update module;

2b) initialized nonlinear compensation weight coefficient is transferred to digital pre-distortion computing module by weight coefficient update module;

(3) nonlinear compensation signal is obtained:

3a) data predistortion computing module is using the data of the imaginary signals of the solid part signal and base band quadrature digital signal that receive base band quadrature digital signal as first passage;

3b) under the control of clock control module, the data of first passage are obtained the data of second passage through a clock cycle time delay, the data of second passage obtain the data of the 3rd passage through a clock cycle time delay, the data of the 3rd passage obtain the data of the 4th passage through a clock cycle time delay, the data of the 4th passage obtain the data of the 5th passage through a clock cycle time delay;

3c) under the control of clock control module, according to the following formula, the data of 5 passage precompensations are obtained:

$x_m\left(n\right)=\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}{\left|x(n-m+1)\right|}^{2(k-1)}{w}_{\mathrm{mk}}$

Wherein, x _mn () represents the data of m passage precompensation in five passages, n represents the sampling number of the base-band digital linear FM signal that radar signal generation module generates, x (n-m+1) represents the data of m passage in five passages, K represents the total degree compensated m channel data, K be more than or equal to 3 positive integer, w _mkrepresent and carry out the secondary weight coefficient compensated of kth to m passage in five passages, k span is the positive integer between 1 ~ K, || represent and modulo operation is asked to data;

3d) under the control of clock control module, according to the following formula, the offset data of 5 passages is obtained:

y _m(n)＝x(n-m+1)x _m(n)

Wherein, y _mn () represents the offset data of m passage in five passages, n represents the sampling number of the base-band digital linear FM signal that radar signal generation module generates, and x (n-m+1) represents the data of m passage in five passages, x _mn () represents the data of m passage precompensation in five passages;

3e) under the control of clock control module, according to the following formula, nonlinear compensation signal is obtained:

$y\left(n\right)=\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{y}_m\left(n\right)$

Wherein, y (n) represents nonlinear compensation signal, and n represents the sampling number of the base-band digital linear FM signal that radar signal generation module generates, and M represents the total number of passage;

(4) digital radar intermediate-freuqncy signal is obtained:

4a) under the control of clock control module, nonlinear compensation signal is delivered to multiphase filtering module by digital pre-distortion block; Multiphase filtering module, to the nonlinear compensation signal received, carries out multiphase filtering operation, obtains two-forty signal; Again twice extraction is carried out to two-forty signal, obtain imaginary signals and the solid part signal of two-forty signal;

4b) under the control of clock control module, half-phase filtration module receives the imaginary signals of two-forty signal, carries out low-pass filtering, obtain the imaginary signals of filtered two-forty signal to it;

4c) under the control of clock control module, shift module receives the solid part signal of two-forty signal, and carried out right shift, the figure place of displacement is the figure place of the imaginary signals of two-forty signal, obtains the solid part signal of the two-forty signal after being shifted;

4d) under the control of clock control module, by the solid part signal of the two-forty signal after the imaginary signals of filtered two-forty signal and displacement, be transferred to the digital quadrature transformation inverse process module; The solid part signal of the two-forty signal after displacement is multiplied by-1 by the digital quadrature transformation inverse process module, is added, obtains the digital radar linear FM signal of two-forty with the imaginary signals of filtered two-forty signal;

4e) under the control of clock control module, the digital radar linear FM signal of two-forty is delivered to binary code modular converter, obtains digital radar intermediate-freuqncy signal;

(5) radiofrequency signal is obtained:

5a) D/A converter module is by digital radar intermediate-freuqncy signal, is converted into analog linearity FM signal through D/A converter;

5b) analog linearity FM signal and local oscillation signal are carried out mixing by frequency mixing module, obtain radiofrequency signal;

(6) frequency multiplication is amplified:

6a) radiofrequency signal is delivered to frequency multiplier module, obtain Terahertz radar signal;

6b) Terahertz radar signal is delivered to the power amplifier module in Terahertz double frequency power amplification module, obtain Terahertz radar signal z (t) after power amplification;

(7) harmonic signal power is obtained:

7a) Terahertz radar signal z (t) after power amplification is delivered to harmonic filter module, obtain harmonic signal;

7b) harmonic signal is delivered to the power amplifier module in feedback of harmonic module, obtain the harmonic signal after power amplification;

7c) harmonic signal after power amplification is delivered to integrator module, obtain harmonic signal power;

(8) nonlinear compensation weight coefficient is upgraded:

8a) harmonic signal power is fed back to weight coefficient update module, calculate the nonlinear compensation weight coefficient upgraded according to harmonic signal power;

8b) the nonlinear compensation weight coefficient of the renewal calculated is delivered to digital pre-distortion computing module by weight coefficient update module;

(9) the Terahertz radar signal after transmitting power amplification:

Terahertz radar signal after the amplification of radar antenna transmitting power.

7. the Terahertz radar signal method based on feedback of harmonic according to claim 6, is characterized in that, step 4a) described in multiphase filtering operation step as follows:

The first step, is evenly divided into six groups of identical subsignals of sampling number by nonlinear compensation signal;

Second step, proceeds as follows under the control of clock control module:

A clock cycle of time delay and z are carried out successively to first group, the 4th group and the 6th group of nonlinear compensation subsignal ^-1, 2 haplotype datas extract, FIR low-pass filtering and 3 haplotype data interpolating operations, obtain the signal of first group, the 4th group and the 6th group two-forty;

2 haplotype data extractions are carried out successively to second group, the 3rd group nonlinear compensation subsignal, FIR low pass filtered involves 3 haplotype data interpolating operations, obtain the signal of second group, the 3rd group two-forty;

2 haplotype data extractions, FIR low-pass filtering, 3 haplotype data interpolations and three clock cycle of time delay and z are carried out successively to the 5th group of nonlinear compensation subsignal ^-3operation, obtain the signal of the 5th group of two-forty;

3rd step, sues for peace the signal of the signal of first group of two-forty and second group of two-forty, by the clock cycle of signal delay after summation and z ^-1, obtain first via high-rate linear FM signal;

4th step, sues for peace the signal of the signal of the 3rd group of two-forty and the 4th group of two-forty, by two clock cycle of signal delay after summation and z ^-2, obtain the second road high-rate linear FM signal;

5th step, sues for peace the signal of the signal of the 5th group of two-forty and the 6th group of two-forty, obtains the 3rd road high-rate linear FM signal;

6th step, by the three road high-rate linear FM signal summations obtained, obtains two-forty signal z (n).

8. the Terahertz radar signal method based on feedback of harmonic according to claim 6, is characterized in that, step 8a) described according to harmonic signal power calculate upgrade nonlinear compensation weight coefficient, its process is:

The process calculating the nonlinear compensation weight coefficient upgraded according to harmonic signal power is: according to the desirable input/output signal power curve of the power amplifier in Terahertz double frequency power amplification module, if harmonic signal power is less than rated value, illustrate that Terahertz radar signal z (t) after power amplification exists nonlinear distortion, then carry out operation below:

The first step, obtains Terahertz radar digital signal z (n) by Terahertz radar signal z (t) discretization after power amplification;

Second step, the nonlinear compensation weight coefficient vector W of definition weight coefficient update module and training vector thereof be respectively

W＝[w ₁₁,w ₁₂,…w _1K,w ₂₁,…w _MK]

$\tilde{W}=[{\tilde{w}}_{11},{\tilde{w}}_{12},\&CenterDot;\&CenterDot;\&CenterDot;{\tilde{w}}_{1K},{\tilde{w}}_{21},\&CenterDot;\&CenterDot;\&CenterDot;{\tilde{w}}_{\mathrm{MK}}]$

Wherein, M represents the total number of passage, and K represents the total degree compensated m channel data, K be more than or equal to 3 positive integer;

3rd step, the data x (n) of definition first passage and the matrix of time delayed signal composition thereof are X _n, the matrix that definition Terahertz radar digital signal z (n) and time delayed signal thereof form is Z _n,

$X_n=\left(\begin{array}{c}x\left(n\right)\\ x(n-1)\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ x(n-M+1)\\ x\left(n\right)\left|x\left(n\right)\right|\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ x(n-M+1){\left|x(n-M+1)\right|}^{2(K-1)}\end{array}\right)$

$Z_n=\left(\begin{array}{c}z\left(n\right)\\ z(n-1)\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ z(n-M+1)\\ z\left(n\right)\left|z\left(n\right)\right|\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ z(n-M+1){\left|z(n-M+1)\right|}^{2(K-1)}\end{array}\right);$

4th step, definition error signal e (n) is

$e\left(n\right)=y\left(n\right)-\tilde{y}\left(n\right)={\mathrm{WX}}_n-\tilde{W}{Z}_n$

Wherein, nonlinear compensation signal y (n) and training signal thereof be respectively

y(n)＝WX _n

$\tilde{y}\left(n\right)=\tilde{W}{Z}_n;$

5th step, carries out iteration by recurrence least square adaptive algorithm, calculates the training vector of weight coefficient update module the iteration ends when error signal e (n) meets the demands, and will assignment, to W, obtains the nonlinear compensation weight coefficient upgraded;

P (n) is the inverse matrix of data x (n) autocorrelation matrix of first passage, and setting its initial value is P ⁰(n); The training nonlinear weight coefficient vector of setting weight coefficient update module initial value be

Make as l is iterations, will assignment is to W ^l, iterative formula is

$e^l\left(n\right)={\tilde{W}}^l(X_n-Z_n)$

$K^{l+1}\left(n\right)=\frac{P^l\left(n\right)Z_n}{\mathrm{\&lambda;}+Z_h^H{P}^l\left(n\right)Z_n}$

$P^{l+1}\left(n\right)=\frac{P^l\left(n\right)-K^{l+1}\left(n\right)Z_h^H{P}^l\left(n\right)}{\mathrm{\&lambda;}}$

${\tilde{W}}^{l+1}\left(n\right)={\tilde{W}}^l\left(n\right)+K^{l+1}\left(n\right){\left(e^l\left(n\right)\right)}^{*}$

Wherein, K (n) represents gain vector, () ^hrepresent and ask hermitian matrix, () ^*represent and ask conjugate matrices, constant λ is forgetting factor, and 0 < λ < 1.