No abstract

This paper describes the design of an electronicallyswitched active antenna array for near-field microwave imaging of tissue in the range of 6 to 8 GHz. Each antenna element connects directly to a dedicated radio front-end, whose intermediate frequency output is fed to a common port for digital data processing. In this way, the difficulties of designing reproducible microwave switching and feeding networks are avoided. Within each front-end, switched-bias low-noise amplifiers are used to maximize the difference in received power between the on and off states of the imaging sensors, thereby enhancing the dynamic range of the measurement.

An electronically-switched near-field microwave imaging transceiver array is designed for use in the range from 6 to 8 GHz. The array consists of printed antenna elements, each of which is connected to a dedicated radio front-end. By downconverting the received signals at each element to baseband, high-frequency losses are minimized while avoiding complicated microwave switching and feeding networks. Full-wave analysis of the antenna structure is coupled with a mixer's SPICE model, demonstrating the potential dynamic range of such an acquisition system. Experimental results are presented for comparison.Index Terms -Dynamic range, low-noise amplifiers, microstrip antenna arrays, mixers, nonlinear network analysis.