Measured mutual coupling between microstrip antennas

Mutual coupling between -band rectangular, nearly square, and circular microstrip antennas has been investigated experimentally by a series of measurements of the -parameters. The mutual coupling level decreases monotonically with increasing separation between elements with the -plane coupling down 20 dB and the -plane coupling down 25 dB for typical adjacent element spacings. For 1/16 in and 1/8 in substrates at -band the predominant coupling mechanism is via the space wave since the surface wave is shown experimentally to be small.