Multi-Layer Microstrip Array Antenna

The bandwidth behaviour of a pair of stacked rectangular patches is investigated experimentally. The return loss is measured as functions of the size of the upper patch and the separation of the patches. The band-width of the optimized stacked antenna is twice as broad as the bandwidth of the single patch with equal height. At the same time the cross polarisation level is much lower. The stacked microstrip patch is used in an L-band planar array antenna for IFF applications. The aperture consists of two rows of six elements each. A corporate feed network in stripline is mounted as an integrated part behind the antenna aperture. A low density foam is used as a dielectric to obtain a light weight design. Sum and difference radiation patterns are generated. The difference sidelobe level is greater than the sum level to be able to suppress replies outside the sum main beam.