COMPACT SELF-PACKAGED ACTIVE FOLDED PATCH ANTENNA WITH OMNI-DIRECTIONAL RADIATION PATTERN
Xiaoyu Cheng, Jun Shi, Jungkwun Kim, Cheolbok Kim, David Senior and Yong-Kyu Yoon
Recently, an omni-directional patch antenna has been demonstrated by folding the patch in a rectangular wave guide shape, and therefore the inside of the folded patch secures a good electromagnetic shielding zone. However, because of the folding architecture, the antenna gain (for transmitting) and sensitivity (for receiving) has been greatly reduced. In this work, the patch antenna is integrated with an active low noise amplifier in the cavity formed by the folded patch, demonstrating an improved gain and sensitivity, which is attributed to the power gain of the integrated amplifier. Since the amplifier has been self-packaged in the cavity shielded by the ground plane of the patch antenna, it does not interfere with the antenna radiation and any other external circuitry. It preserves its omni-directional radiation characteristic, which finds great usage for many biomedical applications and sensor systems such as a biomedical wireless endoscope. Also, since it is folded, its footprint has been reduced compared to its planar counterpart. In addition, the gap between the edges of the folded patch is utilized for impedance matching, not requiring an additional impedance matching circuit between the antenna and the feeding circuit. Integrated with a low noise amplifier circuit consisting of NBB-400 (RFMD, Inc.) and some passives in the cavity area, a self-packaged omnidirectional active antenna operating at 2.4 GHz with a dimension of 19mm ? 18.4mm ? 18.4mm (length ? width ? height) is successfully demonstrated. The footprint has been reduced by more than 50% compared with its counterpart. The structure has been simulated using a high frequency structure simulator (HFSS, Ansys Inc.) and the results show good agreement with measurement results.
Keywords: Antenna arrays, Antenna radiation patterns, Broadband antennas, Cavity resonators, Impedance matching and Patch antennas