Vladimir Palamarchuk

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.

Radar tomography using MIMO noise radar with signals time-division in transmit/receive channels

We describe MIMO approach to implementation of radar tomography and present preliminary results of its experimental validation using Ka-band noise waveform ground based SAR. The range resolution in radar tomography is determined by power spectrum width of the transmitted signal, while cross-range resolutions are defined by 2D aperture dimensions. We apply MIMO concept with time-division to emulate 2D aperture synthesis combined with range resolution due to wideband random signals which enables generation of 3D coherent radar images. Two linear synthetic apertures have been used for transmit and receive antennas oriented in vertical and horizontal directions, respectively.

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.

Capabilities of noise radar in remote sensing applications

Nowadays noise waveform signals attract attention of radar engineers because they are inexpensive to generate both in analog and digital formats, covert, have good resistance against jamming and interference, are easily obtained using current microwave and RF circuit technology, spectrally very efficient and can share spectral bands without mutual interference, exhibit excellent waveform diversity characteristics. Coherent processing of noise signals enables to use them for phase and Doppler frequency measurements and for SAR imaging. Current work describes several radars showing current capabilities of noise radar technology such as shifts detection using Ka-band and X-band noise SAR, 3D SAR imaging and novel high dynamic range noise radars.

Ka-Band Ground-Based Noise Waveform SAR

We present main results of design and investigations of Ka-band ground based interferometric SAR which uses continuous noise waveform as a probe signal and may operate in both monostatic and bistatic regimes. Synthetic aperture antennas enable to design a portable, light weight, easy to mount device with high speed of operation suitable for SAR imaging in quasi-real time while Ka-band noise waveform signals provide all-weather high resolution, high electromagnetic compatibility and interference immunity. Experiments have shown a rather high stability and repeatability of the measurements due to both the high quality of the equipment and advanced signal processing methods. The SAR system designed is an innovative instrument for solving new tasks of precise remote monitoring of various large objects, such as sealing of big halls, dams, bridges, TV towers, hangars, etc.

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.

Doppler signal detection using stepped frequency noise radar

Current paper deals with radar design obtained by combination of two approaches: stepped frequency radar and noise radar for the purposes of SAR imaging. The idea of operation of such combination is following: instead of single frequency signal a narrowband noise signal is radiated in a stepped frequency radar. The processing is done in the same way as in usual stepped frequency radar. Noise modulation will lead to limitation of area within which the radar is sensitive by the correlation length of the noise signal. Analog filter in the receiver will filter out fluctuations caused by the targets outside the noise signal correlation interval. This gives possibility to make a radar using stepped frequency concept but with limited sensitivity zone. This can be helpful for omitting such drawbacks of stepped frequency approach as presence of range ambiguities, low electromagnetic compatibility, high probability of interception and low interference immunity. Besides, it preserves such desired quality of stepped frequency radar as ability to generate high resolution range profiles using a narrowband receiver. This solves problem of lack of ADCs with both high depth and sampling rate which leads to difficulties in design of high performance noise radars using conventional approach. The aim of the paper is to describe the approach, to present results of experiments aimed on detection of Doppler signal using the approach and limitation of observed ranges via variation of noise modulation bandwidth.