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Online ISSN 1751-8792 Print ISSN 1751-8784

IET Radar, Sonar & Navigation

Volume 2, Issue 4, August 2008

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Volume 2, Issue 4

August 2008

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  • Signal processing in noise radar technology

    • Editorial: Signal processing in noise radar technology
      Ka-band bistatic ground-based noise waveform SAR for short-range applications
      • Author(s): K.A. Lukin ; A.A. Mogyla ; V.P. Palamarchuk ; P.L. Vyplavin ; O.V. Zemlyaniy ; Y.A. Shiyan ; M. Zaets
      • Source: IET Radar, Sonar & Navigation, Volume 2, Issue 4, p. 233 –243
      • DOI:  10.1049/iet-rsn:20080017
      • Type: Article
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      • p. 233 –243 (11)
        The designing and testing of a new Ka-band ground-based noise waveform synthetic aperture radar (GB NW-SAR) are presented. Its design is based upon new synthetic aperture antennas and noise radar technology. The authors present preliminary results of its indoor trials. The GB NW-SAR designed may be reconfigured for operation in mono-, bi- and multistatic (or MIMO) modes in both CW and pulse regimes using single- and dual-frequency modes to enhance range resolution via expanding the frequency bandwidth of the signal. Potential resolution of the GB NW-SAR is 15 cm both in range and azimuth. Results of indoor trials are presented for both SAR imaging and differential interferometry measurements. Designed and tested Ka-band GB NW-SAR is applicable for precise remote monitoring of various manmade or natural objects, such as ceilings and roofs of big halls and hangars, dams, bridges, TV towers etc.
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      Hilbert–Huang transform analysis of human activities using through-wall noise and noise-like radar
      • Author(s): C.-P. Lai ; R.M. Narayanan ; Q. Ruan ; A. Davydov
      • Source: IET Radar, Sonar & Navigation, Volume 2, Issue 4, p. 244 –255
      • DOI:  10.1049/iet-rsn:20070140
      • Type: Article
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      • p. 244 –255 (12)
        Various parts of the human body have different movements when a person is performing different physical activities. There is a need to remotely detect and recognise specific human activities for applications involving anti-terrorism, hostage liberation and search-and-rescue. An ultrawideband noise radar system has been built to detect signatures of human activities. The Hilbert–Huang transform, which is used to extract the human-induced Doppler frequency shift from the received signal, facilitates the identification and recognition of various human activities. A non-stationary Doppler model is developed to describe various aspects of human motion, which compares well with measured data. The theoretical analysis and experimental results are discussed.
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      Adaptive chaotic maps for identification of complex targets
      • Author(s): T.L. Carroll
      • Source: IET Radar, Sonar & Navigation, Volume 2, Issue 4, p. 256 –262
      • DOI:  10.1049/iet-rsn:20070128
      • Type: Article
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      • p. 256 –262 (7)
        Identification of complex targets in radar or sonar is a difficult problem. The author shows how the parameters of a simple chaotic map may be optimised to increase the cross correlation of a transmitted signal with the reflection from one target while decreasing the cross correlation with another target. The targets consist of simple arrays of point scatterers. The author shows that the optimisation process produces a chaotic signal with a power spectrum that maximises the ratio of the cross correlation with one target to the cross correlation with a different target, however the author also shows that the specific time ordering of the chaotic signal is also important in determining the cross correlation. The performance of the chaotic signal is better than a random signal with the same power spectrum. The author also shows an example of applying these methods to targets that are more complex.
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      Quality enhancement of image generated with bistatic ground based noise waveform SAR
      • Author(s): K. Kulpa ; K. Lukin ; J. Misiurewicz ; Z. Gajo ; A. Mogila ; P. Vyplavin
      • Source: IET Radar, Sonar & Navigation, Volume 2, Issue 4, p. 263 –273
      • DOI:  10.1049/iet-rsn:20070165
      • Type: Article
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      • p. 263 –273 (11)
        A new method for quality enhancement in a noise synthetic aperture radar (SAR) image and the first results of its application to the SAR image generated with the use of a bistatic Ka-band ground-based noise waveform SAR (GB NW-SAR) are presented. A SAR image generated with a noise SAR suffers from the masking effect which is tied to residual random fluctuations in noise radar response from bright scatterers in the scene. This is similar to the masking effect present in the deterministic waveform SAR when the signal sidelobes of echoes from bright scatterers may mask the main response from a weaker target. The procedure presented is a variation of the CLEAN algorithm. Knowing precisely the emitted signal and finding positions of the strongest scatterers one may model the echo signal originated from a selected scatterer. Extraction of the modelled signal from the received one reduces the residual fluctuations and makes it possible to clean the image and increase its dynamic range. The final image is constructed from the cleaned signal and the previously removed strongest scatterers. A theoretical background is provided to the proposed procedure and its application to enhance the SAR image using simulated data as well as data generated by the Ka-band bistatic GB NW-SAR is demonstrated. The GB NW-SAR, recently developed and tested in LNDES IRE NASU, may operate in CW and pulse random signal regimes for short range applications.
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      Stretch processing for masking effect removal in noise radar
      • Author(s): J. Misiurewicz  and  K. Kulpa
      • Source: IET Radar, Sonar & Navigation, Volume 2, Issue 4, p. 274 –283
      • DOI:  10.1049/iet-rsn:20070134
      • Type: Article
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      • p. 274 –283 (10)
        A method of removing the masking effect caused by strong target echoes in a noise radar is presented. Signal processing in noise radar is based on the calculation of the correlation between transmitted and received signals. Strong echoes of nearby targets produce relatively high sidelobes in the correlation function, thus masking weak echoes of far targets. The classical method of masking effect removal, taking into consideration only the Doppler shift of target echoes, does not remove the strong target echo completely when targets migrate between range resolution cells in the integration time. The method proposed, based on signal stretch processing and a point target model, shows an improvement over existing methods and allows for the detection of weak targets also in the presence of the fast and strong ones.
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      Robustification of noise radar detection
      • Author(s): K. Kulpa ; Z. Gajo ; M. Malanowski
      • Source: IET Radar, Sonar & Navigation, Volume 2, Issue 4, p. 284 –293
      • DOI:  10.1049/iet-rsn:20070135
      • Type: Article
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      • p. 284 –293 (10)
        A study of robust detection scheme for continuous wave noise radars is presented. The probability density function (PDF) of the noise at the input of the radar is not usually Gaussian and has heavy tails generated by impulse interferences. Although the PDF of interferences at the output of the noise radar correlator is Gaussian, impulse interferences increase the processing floor, and thus decrease the overall radar sensitivity. The proposed robustification applied to the correlator's input signal increases the radar sensitivity in the presence of impulse interferences, and does not introduce any significant losses if the input noise is purely Gaussian.
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      Mutual interference and low probability of interception capabilities of noise radar
      • Author(s): T. Thayaparan ; M. Daković ; L. Stanković
      • Source: IET Radar, Sonar & Navigation, Volume 2, Issue 4, p. 294 –305
      • DOI:  10.1049/iet-rsn:20070146
      • Type: Article
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      • p. 294 –305 (12)
        Recently, there has been considerable interest in noise radar over a wide spectrum of applications, such as through-wall surveillance, tracking, Doppler estimation, polarimetry, interferometry, ground penetrating or subsurface profiling, detection, synthetic aperture radar (SAR) imaging, inverse SAR imaging, foliage penetration imaging etc. Major advantages of using noise in the transmit signal are its inherent immunity from radio frequency and electromagnetic interference, improved spectrum efficiency, and hostile jamming as well as being very difficult to detect. The basic theory of digital signal processing in noise radar design is treated. The theory supports the use of noise waveforms for radar detection and imaging in such applications as covert military surveillance and reconnaissance. It is shown that by using wideband noise waveforms, one can achieve high resolution and reduced range estimation ambiguity. Mutual interference and low probability of interception capabilities of noise radar are also evaluated. The simulation results show the usefulness of the noise radar technology to improve on conventional radars.
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      Time–frequency-based non-stationary interference suppression for noise radar systems
      • Author(s): M. Daković ; T. Thayaparan ; S. Djukanović ; L.J. Stanković
      • Source: IET Radar, Sonar & Navigation, Volume 2, Issue 4, p. 306 –314
      • DOI:  10.1049/iet-rsn:20070137
      • Type: Article
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      • p. 306 –314 (9)
        The problem addressed here is non-stationary interference suppression in noise radar systems. Towards this aim, two linear time–frequency (TF) transforms, short-time Fourier transform and local polynomial Fourier transform are used as a means of signal representation and filtering. The noise radar return signal is a wideband random signal occupying the whole TF plane, whereas the interference signal is well concentrated in the TF plane. This implies that the filtering of the received signal can be performed by using a binary mask to excise only a portion of the TF plane corrupted by the interference. Simulations carried out on the radar return signal corrupted by extremely strong non-stationary interferences confirm the effectiveness of the proposed method.
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      Ultra-wideband radar noise reduction for target classification
      • Author(s): S. Hantscher ; A. Reisenzahn ; C.G. Diskus
      • Source: IET Radar, Sonar & Navigation, Volume 2, Issue 4, p. 315 –322
      • DOI:  10.1049/iet-rsn:20070097
      • Type: Article
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      • p. 315 –322 (8)
        The authors describe a calibration procedure for ultra-wideband (UWB) radar systems in order to measure the frequency-dependent transfer function or radar cross-section, respectively, of objects with a high computational efficiency. The benefit of using UWB pulses is that only one measurement is required for covering several GHz. However, the signal processing steps contain a deconvolution operation producing spike artefacts. They were successfully removed by the calculation of frequency-dependent signal-to-noise ratio and a following Wiener filtering. The proposed method was verified by some elementary targets of which the size of the objects were determined.
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