Abstract: A technique for near-field tomographic imaging using a multiple-receiver correlating interferometer. A target object or scene to be imaged is located in a near-field or Fresnel region of a receiver system. The target object radiates or reflects a signal that is sensed by a plurality of antennas. The received signals are correlated using conventional correlation algorithms. An image pixel for a focal point is then computed by correcting a differential time delay between a signal emitted at the focal point and received at first and second antennas. The system is focused on the target object by correcting a phase term of the correlation algorithms. The phase term is corrected by multiplying the correlation algorithms by a phase factor. A peak correlated value is developed when the focal point is at the target object location. A series of snapshots is generated from data produced by the focussing process, as the focal point is moved through the scene.

Abstract: An efficient digital beam-forming network (100) utilizing a relatively few small-scale A/D converters is disclosed herein. The inventive beam-forming network (100) is disposed to generate an output beam B in response to a set of N input signals. The set of input signals is provided by an antenna array (110) having N elements, upon which is incident an electromagnetic wavefront of a first carrier frequency. The present invention includes an orthogonal encoder circuit (170) for generating a set of N orthogonal voltage waveforms. A set of biphase modulators (162-168) modulates the phase of each of the input signals in response to one of the orthogonal voltage waveforms, thereby generating a set of N phase modulated input signals. The N phase modulated input signals are combined within an adder (180) to form a composite input signal. The inventive network (100) further includes a downconverting mixer (184) for generating an IF input signal in response to the composite input signal.