The implementation of grating lobe techniques in phased array design

In airborne applications requiring large physical antenna apertures, the use of grating lobe techniques offers significant advantages in simplicity of mechanization, and small physical size. This paper describes the implementation details and experimental data obtained for two linear, -band grating lobe array systems designed for use in a real-time, forward-looking, high-resolution radar, and which are aerodynamically compatible with high-performance aircraft. The antennas are 25 feet long and, with uniform illumination, provide a beamwidth of about 2 milliradians. Both arrays have a thinning factor greater than 90 percent. Grating lobe ambiguities are resolved by pattern product multiplication of separate dissimilar transmit and receive arrays. The alignment between the transmit and receive array patterns is maintained by means of a reference line and phase-locked loop which corrects the alignment on a pulse-to-pulse basis to a tolerance of about milliradians. Those interested in the mathematical details of phased grating-lobe product arrays may refer to a paper presented at the 8th International Convention on Military Electronics.