CN103955008A - Amplitude calibrating method used for multi-probe near-field scattering imaging - Google Patents

Abstract

The invention provides an amplitude calibrating method used for multi-probe near-field scattering imaging. The method includes the steps of (1) background scattering data are measured through a multi-probe detection system; (2) scattering data of a target to be measured are measured; (3) scattering data of a metal plate are measured; (4) background cancellation is carried out on the target to be measured to obtain scattering data, and imaging processing is carried out on the scattering data to obtain an imaging result; (5) background cancellation is carried out on the calibration metal plate to obtain scattering data, and imaging processing is carried out on the scattering data in an RMA algorithm to obtain an imaging result; (6) the imaging result is calibrated according to a first formula, and the calibrated imaging result of the target to be measured is obtained. According to the technical scheme, microwave / millimeter wave imaging azimuth amplitude calibration can be carried out, the amplitude calibrating method is mainly used for the multi-probe imaging system poor in amplitude precision, the imaging result is directly calibrated through a simple calibration element, and imaging precision is improved.

Description

A kind of amplitude calibration method for the imaging of many probe near-field scatterings

Technical field

The invention belongs to the amplitude calibration technical field of many probe near-field scatterings imaging, in particular a kind of amplitude calibration method for the imaging of many probe near-field scatterings.

Background technology

Many probe near-field scattering imaging techniques have been avoided the long-time data acquisition that in scanning imagery, mechanical motion causes, improve the real-time of microwave and millimeter wave imaging, had a wide range of applications in fields such as safety check, nondestructive examination and target scattering characteristics distribution tests.Range migration algorithm (RMA) is imaging algorithm conventional in Synthetic Aperture Radar Technique, but when RMA algorithm is used for to the imaging of many probe systems, to the target imaging of identical scattering strength, in orientation upwards, the amplitude of imaging region center and marginal position picture differs larger, and imaging results can not correctly reflect that the scattering properties of target distributes.

Target object generally uses RCS (RCS) to carry out quantitative description to electromagnetic scattering power, microwave and millimeter wave imaging technique can represent intuitively with image the distribution situation of RCS scattering center in target area, it is the effective means of carrying out the stealthy test of objective body electromagnetism, particularly Near-Field Radar Imaging, in small area, can carry out system buildup, the imaging analysis in realize target region, in aspect widespread uses such as geography detection, safety inspection, detection through walls, nondestructive examinations.

Because the application such as safety check, detection through walls is higher to the requirement of real-time of imaging, the demand of many probe tests is also along with increase, many probe Near-Field Radar Imagings utilize multiple emitting antennas and multiple receiving antenna exactly, within the extremely short time, complete the electromagnetic scattering DATA REASONING to target area by switching over or waveform modulated, then utilize corresponding algorithm to carry out inverting to obtain the scattering picture of target area, also referred to as multiple-input and multiple-output (MIMO) imaging.Many probe Near-Field Radar Imagings do not need target area to carry out mechanical scanning, have avoided long data acquisition, for the real-time application of microwave and millimeter wave imaging provides solution.

Range migration algorithm (RMA) is the algorithms most in use in synthetic aperture radar (SAR) imaging technique, due to traditional RMA algorithm based on be the image data of internal loopback in conjunction with mechanical scanning, while being applied to MIMO (Multiple-Input Multiple-Out-put) system, need to carry out single site equivalence, or carry out the separation of dual-mode antenna spectral domain, the phase differential that the former need to consider actual dual-mode antenna is different from equivalent single site transmitting-receiving phase place, and latter is without consideration.

RMA algorithm mostly adopts displaced phase center method in the application process of many probe imaging techniques at present, as the people such as Gregory L.Charvat have adopted the array format of equivalent uniform sampling point in " An Ultrawideband (UWB) Switched-Antenna-Array Radar Imaging System ", wherein consider phase alignment, utilize an elongated metallic rod to be positioned over array image-forming region, be equivalent to the scattering point of two-dimensional surface, by contrasting the different phase alignments that carry out of each channel measurement phase place and theoretical single site phase differential.The algorithm that the people such as Xiaodong Zhuge have adopted dual-mode antenna spectral domain to separate in " Three-Dimensional Near-Field MIMO Array Imaging Using Range Migration Techniques ", but its test target is all positioned over imaging region center, do not consider amplitude precision problem.

By analyzing domestic and international list of references and similar techniques, the calibration of the Near-Field Radar Imaging system of popping one's head in only adopts a shaft-like or spherical scatterer to calibrate mostly, or does not consider amplitude precision problem, does not calibrate.Adopt shaft-like or spherical scatterer can only carry out phase alignment, can eliminate the phase differential between actual dual-mode antenna phase differential and equivalent single site, but because calibrating device is equivalent to a scattering point, can not carry out amplitude calibration.

Therefore, there is defect in prior art, needs to improve.

Summary of the invention

Technical matters to be solved by this invention is for the deficiencies in the prior art, and a kind of amplitude calibration method for the imaging of many probe near-field scatterings is provided.

Technical scheme of the present invention is as follows:

For an amplitude calibration method for many probe near-field scatterings imaging, wherein, comprise the following steps:

Step 1: utilize many probe detections systematic survey backscatter data S ₀or setting S ₀=0;

Step 2: measure target scattering data S to be measured;

Step 3: place the sheet metal that is greater than region to be imaged in target range to be measured to same position place, carry out metal plate scatter DATA REASONING S _std;

Step 4: target to be measured is carried out to background and offset and obtain scattering data S-S ₀, utilize RMA algorithm to carry out imaging processing to it and obtain imaging results f (x, y);

Step 5: calibration sheet metal is carried out to background and offset and obtain scattering data S _std-S ₀, utilize RMA algorithm to carry out imaging processing to it and obtain imaging results f _std(x, y);

Step 6: utilize a pair of imaging results of formula to calibrate, obtain the imaging results f of the rear target to be measured of calibration _cali(x, y), formula one:

$f_{\mathrm{cali}}(x,y)=\frac{f(x,y)}{f_{\mathrm{std}}(x,y)}.$

Described amplitude calibration method, wherein, described target to be measured is flat metal plates.

This calibration steps can be used for all kinds of imaging test systems of the each frequency range of microwave/millimeter wave, not being only applicable to many probe imaging systems adopts RMA algorithm to carry out the calibration of imaging, also can be used for the imaging results calibration of all kinds of microwave/millimeter wave imaging systems that adopt other algorithm, the orientation that the present invention can carry out microwave/millimeter wave imaging is to amplitude calibration, be mainly used in the poor many probe imaging systems of amplitude precision, use simple alignment part directly imaging results to be calibrated, improve imaging precision.

Brief description of the drawings

Fig. 1 is many probe Near-Field Radar Imaging schematic diagram in the present invention;

Fig. 2 is the inventive method process flow diagram.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

Embodiment 1

In many probes Near-Field Radar Imaging model as shown in Figure 1,101 is emitting antenna, and 102 for receiving day, x and y direction be orientation to, z direction be distance to, pop one's head in and be positioned at the xy plane of z=0, target is positioned at the front semispace of z>0.

As shown in Figure 2, the present invention is based on the evenly principle of reflection of plane-reflector, carry out amplitude calibration taking sheet metal as calibrating device.Different from phase alignment mode, while using tabular calibrating device, can not obtain its near-field scattering theoretical distribution according to phase delay simply, the present invention will utilize its imaging results to calibrate.Obtaining sheet metal imaging results is f _bo(x, y), the processing of the picture of target to be measured being carried out to following formula one can complete calibration.Formula one:

$f_{\mathrm{cali}}(x,y)=\frac{f(x,y)}{f_{\mathrm{std}}(x,y)}.$

Utilize this method to carry out the concrete implementation step of many probe near-field scatterings imagings as follows:

Step 1: utilize many probe detections systematic survey backscatter data S ₀;

Step 2: measure target scattering data S to be measured;

Step 3: place the sheet metal that is greater than region to be imaged in target range to be measured to same position place, carry out metal plate scatter DATA REASONING S _std;

Step 4: target to be measured is carried out to background and offset and obtain scattering data S-S ₀, utilize RMA algorithm to carry out imaging processing to it and obtain imaging results f (x, y);

Step 5: calibration sheet metal is carried out to background and offset and obtain scattering data S _std-S ₀, utilize RMA algorithm to carry out imaging processing to it and obtain imaging results f _std(x, y);

Step 6: utilize a pair of imaging results of formula to calibrate, obtain the imaging results f of the rear target to be measured of calibration _cali(x, y).

Note: step (1) is to omit step, as omit S ₀=0.

This calibration steps can be used for all kinds of imaging test systems of the each frequency range of microwave/millimeter wave, not being only applicable to many probe imaging systems adopts RMA algorithm to carry out the calibration of imaging, also can be used for the imaging results calibration of all kinds of microwave/millimeter wave imaging systems that adopt other algorithm, the orientation that the present invention can carry out microwave/millimeter wave imaging is to amplitude calibration, be mainly used in the poor many probe imaging systems of amplitude precision, use simple alignment part directly imaging results to be calibrated, improve imaging precision.

Should be understood that, for those of ordinary skills, can be improved according to the above description or convert, and all these improvement and conversion all should belong to the protection domain of claims of the present invention.

Claims (2)

1. for an amplitude calibration method for many probe near-field scatterings imaging, it is characterized in that, comprise the following steps:

Step 1: utilize many probe detections systematic survey backscatter data S ₀or setting S ₀=0;

Step 2: measure target scattering data S to be measured;

Step 3: place the sheet metal that is greater than region to be imaged in target range to be measured to same position place, carry out metal plate scatter DATA REASONING S _std;

Step 4: target to be measured is carried out to background and offset and obtain scattering data S-S ₀, utilize RMA algorithm to carry out imaging processing to it and obtain imaging results f (x, y);

Step 5: calibration sheet metal is carried out to background and offset and obtain scattering data S _std-S ₀, utilize RMA algorithm to carry out imaging processing to it and obtain imaging results f _std(x, y);

Step 6: utilize a pair of imaging results of formula to calibrate, obtain the imaging results f of the rear target to be measured of calibration _cali(x, y), formula one:

$f_{\mathrm{cali}}(x,y)=\frac{f(x,y)}{f_{\mathrm{std}}(x,y)}.$

2. amplitude calibration method as claimed in claim 1, is characterized in that, described target to be measured is flat metal plates.