CN103067329B

CN103067329B - A kind of fast Fourier transform multi-band synthesis of chirp real signal and separation method

Info

Publication number: CN103067329B
Application number: CN201210572742.2A
Authority: CN
Inventors: 刘争红; 郑霖; 樊孝明; 仇洪冰
Original assignee: Guilin University of Electronic Technology
Current assignee: Guilin University of Electronic Technology
Priority date: 2012-12-25
Filing date: 2012-12-25
Publication date: 2015-11-11
Anticipated expiration: 2032-12-25
Also published as: CN103067329A

Abstract

The invention discloses a kind of synthesis of fast Fourier transform multi-band and separation method of Chirp real signal, the multi-band adopting IFFT/FFT conversion to achieve Chirp real signal is synthesized and is separated, each sub-band digital signal samples rate only need reach more than the wide Nyquist sample rate of sub-band (2 sampling rate), relatively conventional method reduces sample rate and memory space, utilize ripe fast Fourier transformation operation unit, reduce computational complexity and calculated load.This programme obtain smooth multi-band Chirp power spectrum, band external leakage little, real signal be applicable to monolateral spectrum send, save bandwidth resources, FFT can be adopted directly to be separated multi-band signal to base band, complexity and operand low, restore information aliasing interference little.

Description

A kind of fast Fourier transform multi-band synthesis of chirp real signal and separation method

Technical field

The present invention relates to radar detection and the communications field, be specifically related to a kind of synthesis of fast Fourier transform multi-band and separation method of chirp real signal.

Background technology

Chirp signal, except as except radar signal, is also a kind of effective signal of communication.Owing to having high anti-interfering performance, constant amplitude and compression pulse characteristic, possess radar detection and communication capacity simultaneously, paid close attention to widely.The generation of traditional C hirp signal adopts the method for analog circuit frequency sweep, adopts phase-locked loop or surface acoustic wave (SAW) device, and detect relevant employing SAW matched filter, but signal and filtered version are fixed, the customized cost of device is high.Current advanced Digital Signal Processing is conducive to the generation of precise signal and improves the detection perform of Received signal strength, and therefore digital Chirp signal generation and detection are development trends.

Chirp signal adopts multi-band form to be conducive to reducing frequency selective fading channels to the impact of input, reduce the complexity of demodulation, affect more much smaller than OFDM by frequency deviation, be conducive to adopting modern signal processing to improve generation and the detection efficiency of signal simultaneously, improve detection and communication performance.If the mode that then each subband signal digital sample sues for peace is synthesized multi-band signal, require that each sub-band sample rate all reaches more than the twice sample rate of total bandwidth, sampling, calculating and storage load are large, the multi-band signal of such synthesis is real signal, namely power spectrum is full symmetric, be modulated on carrier wave and can only get monolateral part, do not affect demodulation.For multi-band digital signal, the existing Fourier transform (FFT) that adopts carries out multi-band synthesis and the application be separated, sub-band sample rate only need more than the twice that sub-band is wide, memory space is few, FFT or IFFT computational load is low, the generation of such as OFDM (OFDM) signal and detection, but the signal produced by fft algorithm is complex signal, namely comprise orthogonal and digital waveform signal that is in-phase component, the power spectrum of this signal is asymmetric spectrum, twice baseband bandwidth is taken after carrier modulation, and be not suitable for detecting the occasion with particular requirement to bandwidth sum.

Summary of the invention

The present invention proposes a kind of synthesis of fast Fourier transform multi-band and separation method of chirp real signal, by N roadbed band Chirp digital signal is carried out specific N point IFFT computing, synthesis exports the multi-band signal for N point phase same rate, there is the real signal base band power spectrum of full symmetric, thus reduction radio frequency bandwidth, receiver, by conventional FFT separate sub-bands, exports N railway digital baseband signal, and will export corresponding with transmitter sub-band signal.

The present invention adopts IFFT/FFT conversion achieve the multi-band synthesis of Chirp real signal and be separated, each sub-band digital signal samples rate only need reach more than the wide Nyquist sample rate of sub-band (2 sampling rate), relatively conventional method reduces sample rate and memory space, utilize ripe fast Fourier transformation operation unit, reduce computational complexity and calculated load.This programme obtain smooth multi-band Chirp power spectrum, band external leakage little, real signal be applicable to monolateral spectrum send, save bandwidth resources, FFT can be adopted directly to be separated multi-band signal to base band, complexity and operand low, restore information aliasing interference little.

Here is that the concrete of the program describes:

For the multi-band composition problem of Chirp real signal, propose a kind ofly to adopt fast Fourier transform method to realize many baseband digital signals to synthesize an algorithm of having a lot of social connections band real signal, adopt inverse transformation decomposition-reduction to be former multichannel baseband digital signal at receiving terminal to this composite signal.

The realization of algorithm make use of the conjugate symmetry matter of discrete Fourier transform, and in the N point discrete Fourier of sequence { x (n) }, leaf contravariant is changed to { X (k) }, then have:

IDFT[X ^*(N-k)] _N＝x ^*(n)

IDFT[X(k)+X ^*(N-k)] _N＝2Re[x(n)]

DFT[2Re(x(n))]＝DFT[x(n)+x ^*(n)]＝X(k)+X ^*(N-k)

Kth way frequency band Chirp signal is adopted the information symbol a that IQ two paths of signals quadrature modulation is identical _ki (), plural form is X _k(t)=a _k(i) e ^{j φ (t)}, wherein: k=0,1 ... N-1; φ (t) represents phase place, frequency ramp Chirp signal, then φ (t)=π ut ²(u > 0); Frequency oblique deascension Chirp signal, then φ (t)=2 π Bt-π ut ²(u > 0).Because IQ two paths of signals modulates identical information symbol a (i), so X _kt () power spectrum signal is approximately monolateral spectrum, and its conjugated signal power spectrum be then approximately monolateral spectrum with zero frequency symmetry.

This N road signal is merged into two vector signal X ^(k)(t _i)=[X ₀(t _i), X ₁(t _i) ..., X _n-1(t _i)] ^tand X ^{* (N-k)}(t _i)=[X ₀(t _i), X _n-1(t _i), X _n-2(t _i) ..., X ₁(t _i)] ^h, wherein conjugation is got in symbol " * " expression, and " T " represents transposition, and " H " represents conjugate transpose; X _k(t _i) Shik road Chirp sub-band X _kthe baseband digital samples signal of (t), k=0,1 ... N-1.

Be loaded into after this two vector addition in IFFT arithmetic element, complete Fourier inversion, be i.e. IFFT [X ^(k)(t _i)+X ^{* (N-k)}(t _i)]=2Re [x _n(t _i)], export as N point real signal vector 2Re [x _n(t _i)], wherein x _n(t _i) be X _k(t _i) IFFT result, k=0,1 ... N-1.

This N point real signal is sent to after parallel-serial conversion, digital-to-analogue conversion, single-side belt filtering, rf modulations and amplification transmitting terminal to launch.

Receiver obtains vector signal 2Re [x after radio-frequency front-end amplification, mixing and digital sample (analog-to-digital conversion) _n(t _i)].

Be loaded into FFT arithmetic element, carried out Fourier transform, the N point vector X of baseband rate can be exported ^(k)(t _i)+X ^{* (N-k)}(t _i), in vector N point element then corresponding N way frequency band digital baseband export.

Subband echo signal is extracted by the multiple matched filtering of Chirp.

This programme obtain smooth multi-band Chirp power spectrum, band external leakage little, real signal be applicable to monolateral spectrum send, save bandwidth resources, FFT can be adopted directly to be separated multi-band signal to base band, complexity and operand low, restore information aliasing interference little.

Accompanying drawing explanation

Fig. 1 is a kind of synthesis of fast Fourier transform multi-band and separation method enforcement structured flowchart of Chirp real signal.

Embodiment

Below in conjunction with drawings and Examples, the present invention is described in further detail.

Only consider the digital baseband part content relevant with the present invention in FIG.Information source N road information symbol a in figure ₀(i), a ₁(i) ..., a _n-1i () represents, modulation module A ₀~ A _n-1adopt Quadrature double path (IQ) with the multiple Chirp modulation of symbol, object obtains monolateral spectrum signal, prevents X ^(k)(t _i) and X ^{* (N-k)}(t _i) signal aliasing, in the convenient extraction of receiving terminal.Modulation module output digit signals merges into two-way N point vector signal X ^(k)(t _i) and X ^{* (N-k)}(t _i), represent with X and Y respectively in Fig. 1, H unit gets conjugation, D unit is adder, F and G unit is IFFT and FFT arithmetic element respectively, and wherein the output of F is the real Chirp signal of multi-band of synthesis, the output of G is the N point vector signal Z of baseband sampling rate, and Z vector is X ^(k)(t _i)+X ^{* (N-k)}(t _i).This signal is imported into coupling correlator M ₀~ M _n-1, or coupling correlator L ₀~ L _n-1, M _kmultiple coupling correlator, L _km _kconjugate impedance match correlator, M _koutput be represent a _kthe compression pulse signal of (i), L _koutput be represent a _n-kthe compression pulse signal of (i), as k=0, a _n(i)=a ₀(i).Unit B is complex signal modulo operation unit.Dotted line represents that vector signal Z was both output to M ₀~ M _n-1module, is also output to L ₀~ L _n-1module, the two Detection results is approximate consistent.

Claims

1. the fast Fourier transform multi-band of a Chirp real signal is synthesized and separation method, it is characterized in that: adopt Fast Fourier Transform Inverse method multichannel baseband digital signal to be synthesized one at transmitting terminal and to have a lot of social connections band real signal, by single side-band transmission, fast Fourier transform decomposition-reduction is adopted to be former multichannel baseband digital signal at receiving terminal to this composite signal; Wherein

Described multi-band synthetic method comprises the following steps:

The Chirp signal way needing synthesis is N, then

(1) kth way frequency band Chirp signal is adopted the information symbol a that IQ two paths of signals quadrature modulation is identical _ki (), plural form is X _k(t)=a _k(i) e ^{j φ (t)}, wherein: k=0,1 ... N-1; φ (t) represents phase place, frequency ramp Chirp signal, then φ (t)=π ut ²(u > 0); Frequency oblique deascension Chirp signal, then φ (t)=2 π Bt-π ut ²(u > 0); Wherein, B is the monolateral bandwidth of subband chirp signal;

(2) this N road signal is merged into two vector signal X ^(k)(t _i)=[X ₀(t _i), X ₁(t _i) ..., X _n-1(t _i)] ^tand X ^{* (N-k)}(t _i)=[X ₀(t _i), X _n-1(t _i), X _n-2(t _i) ..., X ₁(t _i)] ^h, wherein conjugation is got in symbol " * " expression, and " T " represents transposition, and " H " represents conjugate transpose; X _k(t _i) Shik road Chirp sub-band X _kthe baseband digital samples signal of (t), k=0,1 ... N-1;

(3) be loaded into after this two vector addition in IFFT arithmetic element, complete Fourier inversion, be i.e. IFFT [X ^(k)(t _i)+X ^{* (N-k)}(t _i)]=2Re [x _n(t _i)], export as N point real signal vector 2Re [x _n(t _i)], wherein x _n(t _i) be X _k(t _i) IFFT result, k=0,1 ... N-1;

(4) this N point real signal is sent to after parallel-serial conversion, digital-to-analogue conversion, single-side belt filtering, rf modulations and amplification transmitting terminal to launch;

Described separation method comprises the following steps:

(1) receiver obtains vector signal 2Re [x after radio-frequency front-end amplification, mixing and analog-to-digital conversion _n(t _i)];

(2) be loaded into FFT arithmetic element, carried out Fourier transform, the N point vector X of baseband rate can be exported ^(k)(t _i)+X ^{* (N-k)}(t _i), in vector N point element then corresponding N way frequency band digital baseband export;

(3) subband echo signal is extracted by the multiple matched filtering of Chirp.