Four-element beam-forming antenna

The letter describes the construction of a four-element beam-forming antenna array operating at 10.5 GHz. Each element is connected to a microprocessor-controlled complex-weight circuit that can alter the amplitude and phase of a microwave signal. By proper selection of the complex weights, the antenna mainbeam can be steered in any direction, within limits, and null constraints can be applied. Some experimental results in beam forming are presented.