Parametric properties of the two-sided contrast method during radar signal detection against noise and impulse interference with a priory unknown characteristics

On the example of a fluctuating radar signal acquisition characteristics obtained for a receiver, based on the two-sided contrast method, it is shown that for a threshold contrast values z > 1 two-sided contrast method possesses parametric properties, providing unbiasedness, invariance and similarity, i.e. independence of false alarm probability from a priory unknown power of noise interference. Provided the number of contrast elements m ≥ 10 the receiver has interference immunity approximate to optimal and provides high noise immunity towards the impact of chaotic impulse interference with a priory unknown characteristics.     

Nonlinear algorithms for measuring the noise signal power against the background of interferences

Algorithms for measuring the power of mixture components of the noise signal and interferences by using functional transformations of the input mixture in the section of postdetection processing have been considered. The cases of narrowband and pulse interferences were investigated. The performance analysis of the algorithms was performed at different values of interference-to-signal ratio. The results of numerical experiments made it possible to find out the performance peculiarities of algorithms under different conditions.     

Possibilities of processing of signals with completely defined parameters against a background of interferences (noises) in a signal space with algebraic lattice properties

It is shown, that processing of signals with completely defined parameters against a background of interferences (noises) in a space with algebraic lattice properties, we can achieve better processing parameters, than in linear algebraic space.     

Detection of phase-shift keyed signals with gradual phase change during reception on the background of noise

The detection characteristics of phase-shift keyed radar signal (PSKS) with gradual phase change obeying the Barker law have been considered. Analytical expressions were obtained for the PSKS detection characteristics under conditions of different a priori data regarding the signal parameters on the basis of calculations. It was shown that the gradual phase change lead to insignificant deterioration of the probability of the PSKS correct detection as compared with the stepwise phase change.     

The impact of distortions of phase-shift keyed signals with gradual phase change in the receiver input circuits on the signal detection characteristics during the signal reception against the background of noise

This study examines the impact of an input band-pass filter on the reception of phase-shift keyed signals (PSKS) with gradual phase change against the background of noises. In the case under investigation PSKS are received by a correlation receiver during the radar detection of targets. Analytical expressions of the target detection characteristics were obtained for PSKS with random initial phase and the amplitude containing regular and fluctuating components. This study also examines the relationships of the detection characteristics as a function of the input filter band-pass and the interval duration of gradual phase change.     

A multifrequency adaptive radar for detection and identification of objects: Results on preliminary experiments on aircraft against a sea-clutter background

An experimental model of a simple multifrequency continuous wave (CW) radar system has been developed. Preliminary experiments have been performed in order to illustrate the potential of this radar concept in regard to detection, course ranging, and also identification of low flying aircraft against a sea-clutter background. The radar can be organized so as to measure ocean wave height, wave direction, and wave velocity simultaneously for 15 different ocean wavelengths ranging from 150 m to approximately 6 m. An example of such a directional wave intensity spectrum is given. To illustrate the ranging and the identification potential of the technique in regard to airplanes, two different airplane categories, namely a propeller aircraft (Cessna 172) and a rigid jet aircraft (F-16), were flown through the radar beam. The signatures of these two airplanes are show in two signature domains: spatial distribution of scattering centers and motion pattern. The experimental results confirm theories presented in earlier contributions. It remains to introduce two more domains, namely the space/time coherence properties of the target and its polarization characteristics.     

On the relationship between the GLRT and UMPI tests for the detection of signals with unknown parameters

The generalized likelihood ratio test (GLRT) is widely used in signal processing applications such as image processing, wireless communications, medical imaging, classification, and signal detection. However, the GLRT does not have many known properties, other than that it is invariant, uniformly most powerful invariant (UMPI) for problems that fit the linear model, and asymptotically (N/spl rarr//spl infin/) UMPI in general. Since it is invariant, it belongs to the class of tests for which the UMPI test is optimal. In this paper, we consider a general class of detection problems in which unknown signal parameters imply a problem invariance that can be described analytically by orthogonal subgroups. This invariance is natural for problems with unknown signal parameters and, for example, include those of the matched subspace detectors of Scharf and Friedlander. We derive the GLRT and UMPI detectors for this general signal class for the case of Gaussian noise. An expression is found that relates the two test statistics showing the UMPI statistic to be the sum of two terms, one of which is the GLRT. Using this, we find that the GLRT and UMPI tests are asymptotically equivalent as signal-to-noise ratio (SNR) approaches infinity (or as probability of false alarm approaches zero). These results are illustrated by extending an example given by Nicolls and de Jager to show the analytic relationship between the GLRT and UMPI tests. The results indicate that the performance between the tests becomes close at signal-to-noise ratios (SNRs) associated with operating points of the receiver operating curve that are typically of interest in signal detection applications.     

Constant false-alarm rate energy detection of a signal with unknown amplitude and waveform in the presence of a Gaussian interference with unknown variance

A detector of signals with unknown amplitude and waveform in the presence of a Gaussian noise with unknown variance is analyzed. It is shown that the statistics at the detector output is described by the generalized F-distribution. Numerical calculation of the detector’s performance characteristics is performed.     

A point target model for the synthetic aperture radar detection of ships and ice conditions during a swell

A running swell affects the synthetic aperture radar (SAR) imagery of ships, smaller icebergs, and other floating objects because the targets signal is no longer matched with the azimuth processor. This effect is analyzed analytically and numerically for the case of conventional image processing.