Microstrip patch antennas on micromachined low-index materials

Microstrip patch antennas have been used extensively in vehicle and communication systems for the past several decades. These antennas provide low profile, low-weight, and low-cost along with easy integration into planar circuit designs and array configurations. The conventional planar microstrip geometry, however, has limited bandwidth and poor efficiency as well as limited power capability when probe fed or microstrip fed. There are several factors which influence these parameters, the patch geometry and medium directly, and feeding structure indirectly. Currently, designs are often implemented on low index materials for high patch efficiency, and wide bandwidth which can be increased further using wideband impedance matching networks and or aperture coupling methods. Herein, an alternative approach is proposed which allows for easy implementation using micromachining. The goal of this approach is to develop an "effective" low index material underneath the antenna while the feeding circuit is kept on the high index one. The design of a conventional patch antenna fed by a microstrip is developed using micromachining techniques to decrease the height of the high index material underneath the patch while the material under the feedline remains unaltered. This approach reduces the value of the effective dielectric constant only in the area under the antenna, since it is comprised of a mixed dielectric medium of high index material and air.