Volodymyr V. Kudriashov

Coherent imaging in the range-azimuth plane using a bistatic radiometer based on antennas with beam synthesizing

Radiometric monitoring allows us to obtain information about thermal electromagnetic radiation of objects in the chosen frequency band. Imaging of distant targets using their thermal electromagnetic radiation may be implemented with the help of bistatic radiometric systems. These systems are based upon measurement of the time difference of arrival of the radiation received by two or more antennas [1]-[3]. This approach has been developed in long wave radar astronomy to improve angular resolution of telescopes [4], [5].

Precision of target shifts detection using Ka-band ground based noise waveform SAR

There is a growing interest to using of Ground Based SAR for detection of small shifts of various objects. Such equipment can be used for detection of changes in buildings, towers, bridges and natural objects. This can help to predict and prevent possible catastrophes. We have elaborated SAR system capable of detecting such changes using noise radar technology. It uses Ka-band CW noise signals for sounding. The paper is devoted to investigation of differential SAR interferometry technique applied to surface shift detection and estimation using this system. In previous works we gave theoretical consideration of precision dependency on mechanical errors in antenna positioning system and experimentally estimated shift measurement precision for the case of stationary scene using statistical processing of data collected in multiple interferograms. Here we continue investigation of the shifts estimation precision using data collected from the sphere target being shifted. Besides, we investigate influence of the variation of the signal time-bandwidth product onto the shift measurement accuracy. The results agree very well with the previously obtained estimations.

Improvement of Range Estimation with Microphone Array

Abstract This paper presentsanew approach for the three-dimensional (3-D) localization of sound sources. An acoustic camera uses an angular beamforming to measure the Direction of Arrival (Do A) of an incoming signal, to localize the emission source. The acoustic sensor used in this article is the Brüel & Kjaer acoustic camera transformed to operate inabistatic mode. The transformation consists inaplacing of one of the microphones of the acoustic camera outside of its microphone array. This allows simultaneous estimation of the Do Aand the Time Difference of Arrival (TDo A) of the incoming signal(s). Such sensors were not found. The paper proposes emitter localization in range - cross range - elevation coordinates by combining estimates of TDo Aand Do Aand presents the signal processing method for that purpose. The range resolution of 0.2mwas achieved in an experiment. Experimental results were obtained using different emission sources. Adescription of resolution cell limitations is presented. The obtained results show acoustic noise source localization without the pre-metering of the range of the imaging plane, i.e., withoutaneed to use the additional range meter which is notapart of the acoustic camera. The latter is important in tasks of non-destructive testing.

Phase measurement accuracy in noise waveform synthetic aperture radar

Detection of small changes in natural formations and human-made constructions is a promising application of synthetic aperture radar (SAR). This paper deals with a specific radar, which is a ground-based SAR using noise waveform. Being fully coherent, SAR provides both phase and amplitude information for every pixel in the mapped area. This gives rise to the possibility of comparing phases between the images taken from the same position at different times in order to extract information about the changes that have occurred between subsequent radar measurements. Such a technique, called coherent change detection (CCD), allows changes of a subwavelength size to be detected. The use of a noise waveform for sounding ensures high electromagnetic compatibility and interference immunity. Moreover, it enables long integration time in the detection stage. However, the random nature of probing signals used in noise radars leads to randomness of the output signals and the preservation of residual fluctuation in the images generated. This random residual, along with external noise, influences the overall accuracy of the phase measurement in noise radar. In this paper, the theoretical and experimental investigation of this specific influence of noise on the precision of phase measurements is presented. The theoretical part of the paper is focused on the estimation of the Cramer-Rao lower bound for the phase measurements using both statistical theory and geometrical interpretation of complex signals. In the experimental part, these findings are verified with dedicated measurements of a metallic sphere displacement, carried out with the help of a ground-based noise waveform SAR.

Ka-band radiometric imaging using antennas with pattern synthesis

The paper is devoted to experimental investigation of coherent radiometric imaging in azimuth-range plane. The Ka-band radar system suggested is a version of bistatic noise waveform SAR (Synthetic Aperture Radar) using two antennas with pattern synthesis and additional receive channel used as a reference signal. Indoor radiometric imaging has been validated using absorbers as the targets. These experiments enabled to estimate both range and angular resolution capabilities of a new radiometric system that was achieved due to application antennas with pattern synthesis and SAR signal processing. This estimate may be done within the range span limited by bistatic radiometer baseline.

Millimeter-wave noise radar tomography

SAR tomography based upon MIMO concept with channels time-division is described and some results of its experimental validation using Ka-band ground based noise waveform SAR are presented. Two different linear synthetic apertures have been used for both transmit and receive antennas oriented in vertical and horizontal directions, respectively. Range resolution in SAR tomography is determined by power spectrum width of the transmitted signal, while its cross-range resolution is defined by 2D aperture dimensions and working wavelength. The approach suggested is applicable for generation of 2D and 3D coherent SAR images and radio-films provided data acquisition and signal processing in real time.

Fusion of Images Generated by Radiometric and Active Noise SAR

Abstract The work is devoted to fusion of radar and radiometer images. Noise waveform SAR generates radar images of reflective objects of its field of view. A bistatic radiometer with synthetic aperture estimates the thermal radio emissions of the objects along their angular coordinates and even range. The estimated brightness temperatures of rough and smooth surfaces are different, as well as the radar responses from them. Identification of the parameters of objects surfaces may be done using results of joint processing of images generated by both sensors. The optimum and quasi-optimum criteria for fusion of the images were obtained. The latter was experimentally checked. It approves the opportunity to fuse the images for further estimation of some parameters of objects surfaces. The results obtained may be used in environmental and security applications.

Accuracy of phase measurements in noise radar

The paper is devoted to theoretical and experimental investigation of specific influence of the randomness onto the accuracy of phase measurements made with the help of ground based noise waveform synthetic aperture radar. Noise waveform used in this system ensures high electromagnetic compatibility and interference immunity. Random nature of probing signals used in noise radars leads to randomness of the output signals and preserving residual fluctuation in the images generated. These random residuals along with the external noise introduce influence onto the overall accuracy of the phase measurements in Noise Radar. It has been shown a good agreement between theory and experiment.

Radar tomography using MIMO noise radar and antenna with beam synthesis

Conventional SAR generates 2D image using combination of range compression and 1D aperture synthesis. The range resolution of such approach is determined by the signal spectrum width, while cross-range resolution is defined by the synthetic aperture length. 2D aperture synthesis implies movement of antenna along 2D aperture and cross-range compression technique in both dimensions to obtain resolution along two angular coordinates. In combination with pulse compression it gives 3D resolution. We suggest using MIMO principle in combination with SAR approach to generate 3D coherent radar images. For that, two linear synthetic apertures used - one for transmit antenna and another for receive one. Spatial scanning with those antennas is performed in the way which provides data similar to the ones obtained from 2D scanner. The paper describes the approach and presents results of its experimental test using Ka-band noise waveform ground based SAR.