Two-dimensional imaging with a radio camera

In the radio camera, adaptive control techniques self-cohere the antenna elements of a phased array, thereby permitting the system to be distorted and even time varying. By doing so, enormous antenna arrays can be constructed A two-dimensional (range-angle) radio camera imaging experiment is reported. A 39-m X-band (3-cm wavelength) array was formed on a cable strung between two towers, each 10 m high, on a hilltop. A pulsed microwave transmitter on the hilltop illuminated the vicinity of Phoenixville, PA, some 7 km distant. As the receiver was moved along the cable, echoes were recorded at random positions. The time-shared receiving array was highly distorted as well as time-varying, yet the radio camera processing produced nearly diffraction-limited images of three city blocks at a distance of 6.5 km in the town, and details of a power plant at a distance of 8.2 km. The use of two different pilot signals or beamforming sources for the self-synchronization process is demonstrated. One source is a corner reflector located in the town; the other is a target of opportunity located in the vicinity.