Microstrip Patch Antennas With Enhanced Gain by Partial Substrate Removal

A method to enhance gain of a microstrip patch antenna is investigated by partially removing the substrate surrounding the patch. The partial substrate removal reduces the losses due to surface waves and dielectric substrate. The effects of substrate removal in different configurations on the gain of the antenna are studied numerically and validated experimentally. Compared to a conventional patch antenna, the antennas with partial substrate removal can enhance gain, for example, up to 2.7 dB. Furthermore, it is observed that the enhancement of gain is more due to loss reduction of surface waves and dielectric substrate than increased patch size when the effective dielectric constant of substrate is lowered. Such a technique can be applied in designs operating at higher frequencies whereby surface wave and substrate losses are more significant though the 2.4-GHz design is exemplified here for ease of fabrication and measurement purposes.