Enhancement of array gain with stacked parasitic elements

Microstrip antennas with stacked parasitic elements have been demonstrated to have broad bandwidth and high gain. The broad band characteristics of microstrip antennas with stacked parasitic elements have been studied extensively and are now well understood. Contrarily, enhancing the gain of a microstrip antenna with stacked parasitic elements has been attempted only by a few researchers over the years. An increase in gain of 3 dB has been reported for a stacked concentric ring patch antenna array. In practice, using stacked parasitic elements for gain enhancement is both easy and less costly since no increase in array size is required to provide the additional effective isotropic radiated power (EIRP) for completing the communication link. This paper reports an experimental investigation of gain enhancement of a 2/spl times/2 microstrip array at 29.5 GHz using stacked parasitic antenna elements. The EIRP and radiation patterns as a function of the spacings between the parasitic and driven antenna layers were measured. These results are presented and discussed.<>