Abstract: A pre-processor and adaptive beamformer processes an echo received by an array of receiving elements from a distant target from a transmitted signal having an arbitrary waveform capable of being represented as a complex modulation of a carrier frequency. Time blocks are formed from each element output represented by a series of time windows extending from an initial time appropriate to the arrival time of the echo to a final time appropriate to the time block. A correlation is performed of each time block with a replica of the transmitted signal. The correlation products are aligned with respect to time difference to within one sample period. The beamformer further aligns the correlation products with respect to time difference to substantially the same phase for each steering direction. Covariance estimates are formed using techniques of spatial averaging to generate adaptive weights optimized to suppress interfering signals without requiring the use of time averaging.

Abstract: A device is provided for processing an echo received by an array of N receiving elements from a target at range R ensonified by an LFM signal of bandwidth B transmitted for a duration T. The device receives each elements output f.sub.n (t) over the elements total receiving time and selects time window element outputs f'.sub.n (t), which are discrete portions of f.sub.n (t), each time window extending from an arbitrary initial time T.sub.0 to time T.sub.f and is spaced from T.sub.0 no more than T and, if there is a target within the window, an echo is received at time T.sub.n. Further the device produces element frequency difference outputs g.sub.n (t) from the frequency difference between a replica of at least a portion of the transmitted LFM signal and the time window element outputs f'.sub.n (t), the outputs g.sub.n (t) being tones with frequencies directly proportional to the time T.sub.n of the target from the time T.sub.0 so that the target range R=(c/2)(T.sub.0 +T.sub.n)+.DELTA.R.sub.

Abstract: An array for receiving wave energy at a pair of widely spaced frequencies has receiving elements arranged to function as a half-wave array for the lower frequency and as a random array for the higher frequency. A plurality of receiving elements are arranged in an array with the receiving elements having nominal positions spaced apart such that spacing between adjacent nominal positions is approximately one half the wavelength .lambda. of the wave having the lower frequency. The receiving elements are randomly distributed about their respective nominal positions with each receiving element being within a distance of .epsilon..lambda..sub.o of its corresponding nominal position where .epsilon. is a randomization parameter and .lambda..sub.o is the wavelength of the higher frequency wave.