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Active imaging arrays are used to image scenes composed of reflectors of transmitted radiation, and in many such applications, line arrays are employed. In this paper, we discuss scanned active line arrays for imaging based on image synthesis. We define the novel concept of array redundancy for active arrays, analogous to the well-known concept of redundancy applied to passive arrays, and we define and give examples of minimum redundancy and reduced redundancy line arrays composed of transmit/receive elements. Such arrays differ from their passive imaging counterparts both in geometry and in element count.

This paper describes the experimental hardware design and implementation for a delay hopped transmitted reference communication system.The hardware is designed to generate the delay hopped transmitted reference signal for a number of experimental conditions. It can be used either in ultra wideband pulse mode, ultra wideband noise mode, or in narrowband mode. We use the experimental hardware setup to conduct link experiments with a delay hopped transmitted reference communication system. Experiments were conducted in an indoor multi-path environment to test the viability of delay hopped transmitted reference for short-range indoor communications. The experimental results presented demonstrate that this modulation format is capable of transmitting data short range indoors with out line of sight transmission path with minimal transmitted RF power.

A general approach to super resolution imaging of point sources using active arrays of transmit/receive elements is presented. The usual techniques of high resolution imaging using single transmitters and passive receive arrays fail in the presence of sets of coherent point sources, which often arise due to coherent multipath. However, data obtained from transmit/receive arrays may be arranged into matrices to which eigenspace direction of arrival estimation may be successfully applied, even int he presence of coherent sources. Each such matrix may be thought of as corresponding to a different transmit/receive array; this may be either the actual transmit/receive array or a virtual transmit/receive array whose effect is synthesized. This approach provides great flexibility, since a large number of different synthetic or virtual arrays may be available for a given transmit/receive array, and each can provide a different tradeoff between the total number of resolvable targets and the largest number of mutually coherent targets which can be resolved.