Portable Real-Time Microwave Camera at 24 GHz

This paper presents a microwave camera built upon a two-dimensional array of switchable slot antennas. The camera borrows from modulated scattering techniques to improve isolation among the array elements. The camera was designed to measure vector electric field distribution, be compact, portable, battery operated, possess high dynamic range, and be capable of producing real-time images at video frame-rate. This imaging system utilizes PIN diode-loaded resonant elliptical slot antennas as its array elements integrated in a simple and relatively low-loss waveguide network thus reducing the complexity, cost and size of the array. The sensitivity and dynamic range of this system is improved by utilizing a custom-designed heterodyne receiver and matched filter for demodulation. The performance of the multiplexing scheme, noise-floor and dynamic range of the receivers are presented as well. Sources of errors such as mutual-coupling and array response dispersion are also investigated. Finally, utilizing this imaging system for various applications such as 2-D electric field mapping, and nondestructive testing is demonstrated.