Microstrip Array for Troposcatter Communications

A high gain, multi-beam microstrip array, and associated multi-channel low noise front end, has been developed for use in experiments relating to advanced troposcatter communication techniques over the 4.4 to 5.0 GHz band. A 10-foot square antenna provides a cluster of orthogonal beams. Two smaller antennas are included. This array permits angle diversity reception, as well as experiments related to Electronic Counter-Countermeasures (ECCM). The radiating elements are wideband dual polarized slots etched in the common ground plane of a pair of microstrip substrates. Each substrate contains the feed circuitry for one polarization. The multi-channel tunable front end exhibits noise figures less than 3.8 dB. It has been designed for extremely low delay distortion, so as to minimize corruption of the signal. A tunable cavity preselector, GaAs FET LNA and thin-film image-reject mixer-preamplifier comprise each channel. The array has proven to be efficient, and capable of wideband performance. The high end performance was impacted by the choice of element spacing. Future arrays will have tighter spacing, to place the grating lobe further away from real space.