We introduce a new family of binary arrays for use in coded aperture imaging which are predicted to have properties and sensitivity (SNR) equal to that of the uniformly redundant array (URA). The new arrays, called MURAs (modified URAs), have decoding coefficients all of which are unimodular, resulting in a reconstructed image with noise terms completely independent of image-source structure. Although the new arrays are derived from quadratic residues, they do not belong to the cyclic difference set or set of pseudonoise sequences and consequently are constructible in configurations forbidden to those designs, thus providing the user with a wider selection of aperture patterns to match his particular needs. With the addition of MURAs to the family of binary arrays, all prime numbers can now be used for making optimal coded apertures, increasing the number of available square patterns by more than a factor of 3.
We describe a class of pulse compression waveform design suitable for applications requiring low peak power, large duty factors, and large compression ratios. The waveforns are closely related to those derived from pseudowise (PN) sequences, and exhibit m a n y of the same properties. However, they exist in code lellgths for which PN sequences cannot be constructed and, therefore, belong to a new class of pulse compression codes that offer the user greater flexibility in selecting a waveform design to match specffic needs In addition, as with rn-sequences, the new waveform design can be used with an "offset" technique that renders perfect sidelobe cancellation in the periodic cross-correlation function, without any broadening of the mainlobe peak. We show how to generate the new codes, discuss their essential mathematical properties, and derive a general expression for the offset values that produce zero sidelobe levels in the periodic cross-correlation function of the waveform Finally, a mathematical proof is presented in the accompanying appendix where it is shown that the sequences presented here are a special case of a more general set of Legendre-like sequences, for which the cross-correlation properties are derived Low probability of intercept (LPI) radar is an increasingly important element in the electronic warfare environment of today. The primary objective of LPI radar is to minimize, as much as possible, the probability of detection (by the enemy) of one's own radar emissions by transmitting low peak power waveforms. Modern solid-state radar transmitters are limited in their ability to produce high peak power pulses. For these particular applications, ideal waveforms are those with high duty factors and large pulse compression ratios, since these lead to reduction of the peak power of the coded pulse while still maintaining the average power levels required for target detection. In addition to reduced peak power requirements, the ideal waveform should have minimal sidelobe values in the cross-correlation function in order to mitigate out-of-range clutter returns, thereby enhancing target detection and target-tracking sensitivity. A new waveform design that meets these objectives is presented here.The new waveform design belongs to a class of radar signals known as binary phase codes. Binary phase codes are those waveforms produced by modulating, at fixed intervals of time, the phase of a coherent CW carrier, subject to the constraint that the phase angle be either 0 or 7r radians during each time interval (subpulse) [l]. The value of the phase angle during individual subpulses is determined by a binary code (i.e., a binary sequence) selected for the signal encoding process. The radar waveform can be written in complex envelope representation as $(r) = exp[j(uot + e,)], n = 0,1,2,.. . ,L -1(1) where W O is the CW carrier frequency, 8, is the phase value (0 or T ) during the nth subpulse, and L is the number of subpulses constituting the complete wavetrain. In order to establish a correspondence between ...
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