Flat 4-direction antenna for antenna pattern diversity reception

The author proposes a flat antenna array for the 4-direction antenna. The array, consisting of four sectoral patches and two 3 dB hybrid couplers, was calculated by the magnetic wall model. The optimized array parameter is b/a=0.5, and is also the optimized value for isolation characteristics. The experiments by the model antenna verified the calculated results. To obtain the 4-direction flat antenna, the antenna element should be chosen to realize the ideal magnetic line current array. Another element and its array is shown where the element is the inverted-F antenna (quarter wave microstrip antennas). This array gives the cardioid vertical plane pattern, however, the side lobe appears in the horizontal plane. The side lobe can be reduced by using the small sized element