CN106093942A - A kind of High Resolution Spaceborne SAR impulse compression method considering stravismus impact - Google Patents

Abstract

The present invention provides a kind of High Resolution Spaceborne SAR impulse compression method considering stravismus impact, and technical scheme comprises the following steps: the first step, compensates phase place: echo-signal is carried out phase compensation, obtains phase compensation back echo signal；Second step, generates frequency domain-matched filter: according to frequency modulation rate, generates reference signal, transform to frequency domain and obtain matched filtering device；3rd step, carries out pulse compression: phase compensation back echo signal is transformed to frequency domain, obtains frequency-region signal；The conjugation of frequency-region signal with matched filtering device is multiplied, obtains the frequency-region signal after matched filtering, transform to the signal after time domain obtains pulse compression.The resolution that the present invention can avoid existing impulse compression method to cause reduces, peak sidelobe ratio raises problem, has and realizes advantage simple, fireballing.

Description

A kind of High Resolution Spaceborne SAR impulse compression method considering stravismus impact

Technical field

The invention belongs to the interleaving techniques field of space flight and microwave remote sensing, particularly to a kind of high score considering stravismus impact Resolution satellite-borne SAR (Synthetic Aperture Radar, synthetic aperture radar) impulse compression method.

Background technology

Satellite-borne SAR is a kind of active sensor being operated in microwave band, and having can round-the-clock, all weather operations Feature.It obtains two dimension high-resolution earth surface radar image to pulse compression and orientation to pulse compression by distance, It is modern earth mapping, the important means of imaging investigation.Image resolution ratio is to weigh the important finger of Spaceborne SAR System imaging capability Mark.SAR image resolution includes range resolution ratio and azimuth resolution.Range resolution ratio is limited to radar signal bandwidth, signal Bandwidth the biggest, range resolution ratio is the highest.Azimuth resolution is limited to beam scanning angle, and beam scanning angle is the biggest, azimuth discrimination Rate is the highest.Modem high-resolution satellite-borne SAR makes irradiated site improve single scattering at ground moving by controlling beam position The beam scanning angle of point, thus improve azimuth resolution.This working method result in overwhelming majority time beam position tool Having certain angle of strabismus, angle of strabismus is generally continuously increased to edge from the scene center of imaging.

(concrete grammar sees 45-67 page of document " synthetic aperture imaging ", Ian to existing impulse compression method G.Cumming etc. write, and Electronic Industry Press publishes for 2007) do not consider to look side ways the impact brought, it is usually used in middle low resolution In satellite-borne SAR or carried SAR signal processing.When realizing pulse compression, echo-signal is considered the direct of radar emission signal Time delay, the pulsewidth of echo-signal, frequency modulation rate with launch signal consistent, its pulse compression is to make reference with transmitting signal, by with The convolution of echo obtains high-resolution one-dimensional range profile.But in High Resolution Spaceborne SAR system, beam scanning causes spaceborne Angle of strabismus and the bigger movement velocity of satellite platform existence that SAR beam position is had make satellite platform and ground radar shine Penetrating region and there is certain speed of related movement, this speed of related movement increases along with angle of strabismus and increases.Speed of related movement Radar return model is changed, radar return no longer be launch signal simple time delay, with launch signal make with reference to The pulse compression mode of echo convolution is the most applicable.

Summary of the invention

It is an object of the invention to, propose a kind of High Resolution Spaceborne SAR impulse compression method considering stravismus impact, solve Under the conditions of High Resolution Spaceborne SAR stravismus, pulse compression performance declines problem.

The thinking of technical solution of the present invention is: a kind of High Resolution Spaceborne SAR impulse compression method considering stravismus impact, Echo model under the conditions of looking side ways according to High Resolution Spaceborne SAR, compensates the additive phase brought by speed of related movement, according to Speed of related movement generates pulse compression reference signal and obtains matched filtering device, echo is carried out Fourier transformation and enters at frequency domain Row matched filtering, finally returns back to time domain, thus completes to consider the High Resolution Spaceborne SAR pulse compression of stravismus impact, obtain High-resolution one-dimensional range profile.

The technical scheme is that:

Known High Resolution Spaceborne SAR launches the parameter of signal: mid frequency f_c, pulsewidth is T, bandwidth B, frequency modulation rate K_r, Wavelength X, propagation velocity of electromagnetic wave C.

Assume that the satellite-borne SAR parameter that arbitrary pulse time is corresponding in certain observation process is: defend under body-fixed coordinate system Star speed V_s, wave beam angle of strabismus θ, satellite-borne SAR observed object obtains echo-signal s (t), and wherein t represents sampling time, above-mentioned ginseng Number all may utilize existing method measurement and obtains.

It is characterized in that, comprise the following steps:

The first step, compensates phase place

Echo-signal is carried out phase compensation, obtains phase compensation back echo signal s'(t), existing phase compensating method , it is preferred to use procedure below:

Calculate and compensate phase place h₁(t):

$h_1\left(t\right)=\exp \{j2{\mathrm{\πf}}_c\frac{2V_{s}sin\mathrm{\θ}}{C}\·t\}$

Calculate phase compensation back echo signal s'(t again):

S'(t)=s (t) h₁(t)

Second step, generates frequency domain-matched filter

Calculate frequency modulation rate K_r':

${K_r}^{\′}=K_r{(1-\frac{2V_s}{C}sin\mathrm{\θ})}^2$

Generate reference signal h₂(t):

$h_2\left(t\right)=rect\[\frac{t}{T}\]\·\exp \left\{j2{{\mathrm{\πK}}_r}^{\′}{t}^2\right\}$

Transform to frequency domain and obtain matched filtering device H₂(f):

$H_2\left(f\right)=\underset{-T/2}{\overset{T/2}{\∫}}{h}_2\left(t\right)\exp \{-j2\mathrm{\π}ft\}dt$

3rd step, carries out pulse compression

By phase compensation back echo signal s'(t) transform to frequency domain, obtain frequency-region signal S'(f):

$S^{\′}\left(f\right)=\underset{-T/2}{\overset{T/2}{\∫}}{s}^{\′}\left(t\right)\exp \{-j2\mathrm{\π}ft\}dt$

By frequency-region signal S'(f) and matched filtering device H₂F the conjugation of () is multiplied, obtain the letter of the frequency domain after matched filtering Number S_h' (f):

S_h' (f)=S'(f) H₂ ^*(f)

By S_h' (f) transform to time domain, obtains the signal s after pulse compression_h' (t):

${s_h}^{\′}\left(t\right)=\underset{-B/2}{\overset{B/2}{\∫}}{S_h}^{\′}\left(f\right)\exp \left\{j2\mathrm{\π}ft\right\}df$

The invention has the beneficial effects as follows: the present invention introduces the compensation phase place under stravismus during pulse compression, calculate Consider the frequency modulation rate change that stravismus is brought during matched filtering device, the resolution fall that existing impulse compression method causes can be avoided Low, peak sidelobe ratio raises problem, and wherein time domain can be come with fast Fourier transform to the conversion of frequency domain and frequency domain to time domain Realizing, the method has and realizes advantage simple, fireballing.

Accompanying drawing explanation

Fig. 1 is the operating diagram that the present invention considers the satellite-borne SAR pulse compression of stravismus impact；

Fig. 2 is the satellite-borne SAR parameter set in emulation；

Fig. 3 is conventional pulse compression result；

Fig. 4 is the pulse compression result of this method.

Detailed description of the invention

Below in conjunction with the accompanying drawings the present invention is further detailed.

Fig. 1 is the process chart of the present invention.Whole flow process is divided into three to walk greatly.The first step: phase compensation: compensate due to ripple The additive phase that bundle stravismus is brought；Second step: generate matched filtering device: according to satellite velocities and angle of strabismus, generate and consider stravismus Matched filtering device；3rd step: process of pulse-compression: echo is fourier transformed frequency domain, at frequency domain and matched filtering device Being multiplied, last another mistake is fourier transformed into time domain, completes pulse compression, obtains high-resolution one-dimensional range profile.

Fig. 2～Fig. 4 is the result utilizing the specific embodiment of the invention to carry out emulation experiment.

Fig. 2 is the satellite-borne SAR parameter set in emulation, including satellite altitude, mid frequency, wavelength, pulse width, signal The parameters such as bandwidth, frequency modulation rate, center downwards angle of visibility, angle of strabismus.Satellite-borne SAR is operated in X-band, according to range resolution ratio computing formula Obtaining range resolution ratio nominal value is 0.15 meter, and the peak sidelobe ratio nominal value of pulse compression is-13.26dB.

Fig. 3 is the result using existing method to carry out pulse compression, and existing impulse compression method does not consider that stravismus is brought The impact of radial velocity, it is believed that receiving signal is the simple time delay launching signal, there is not additive phase and adjusts frequency shift. In figure, abscissa is relative distance (being 0 point with pulse compression peak), and vertical coordinate is that (maximum is normalization amplitude 0dB), the range resolution ratio of compression afterpulse is 0.1505 meter, lower 0.0005 meter than nominal value, peak sidelobe ratio is- 12.74dB is higher 0.52dB than nominal value.Illustrating, existing impulse compression method occurs in that the reduction of pulse compression resolution, peak value Secondary lobe ratio raises problem.

Fig. 4 is the result using the inventive method to carry out pulse compression, and in figure, abscissa is that relative distance is (with pulse pressure Contracting peak is 0 point), vertical coordinate is normalization amplitude (maximum is 0dB), and the range resolution ratio of compression afterpulse is 0.1498 meter, higher 0.0002 meter than nominal value, peak sidelobe ratio is-13.26dB, consistent with nominal value.Illustrate, the arteries and veins of the present invention Punching press compression method can obtain preferable pulse compression as a result, it is possible to the resolution avoiding traditional pulse method to bring reduces, peak Value secondary lobe ratio raises problem.

Invention described above embodiment, is not intended that limiting the scope of the present invention, any in the present invention Amendment, equivalent and the improvement etc. made within spirit and principle, should be included in the claims of the present invention Within.

Claims (1)

1. the High Resolution Spaceborne SAR impulse compression method considering stravismus impact, it is known that High Resolution Spaceborne SAR launches letter Number the parameter parameter corresponding with pulse time arbitrary in certain observation process, it is characterised in that comprise the following steps:

The first step, compensation phase place:

Echo-signal is carried out phase compensation, obtains phase compensation back echo signal；

Second step, generation frequency domain-matched filter:

Calculate frequency modulation rate K_r':

${K_r}^{\′}=K_r{(1-\frac{2V_s}{C}sin\mathrm{\θ})}^2$

Generate reference signal h₂(t):

$h_2\left(t\right)=rect\[\frac{t}{T}\]\·\exp \left\{j2{{\mathrm{\πK}}_r}^{\′}{t}^2\right\}$

Reference signal h₂T () transforms to frequency domain and obtains matched filtering device H₂(f):

The parameter that foregoing is directed to includes:

High Resolution Spaceborne SAR launches the parameter of signal: pulsewidth is T, frequency modulation rate K_r, propagation velocity of electromagnetic wave C；

The satellite-borne SAR parameter that arbitrary pulse time is corresponding in certain observation process is: satellite velocities V under body-fixed coordinate system_s, θ, t represent the sampling time in wave beam angle of strabismus；

3rd step, carries out pulse compression:

Phase compensation back echo signal is transformed to frequency domain, obtains frequency-region signal；

By frequency-region signal and matched filtering device H₂F the conjugation of () is multiplied, obtain the frequency-region signal S after matched filtering_h'(f)；

By S_h' (f) transform to time domain, obtains the signal after pulse compression.