Dual-fed patch antenna with distorted patch mode for balanced circuits

A new dual-fed microstrip patch antenna, which provides both radiating and power dividing/combining functions, is proposed. Distorting the normal patch mode (TM01 mode) makes the two feeding port possess very good isolation so that they can be employed as a power divider/combiner as well. A single-layer design with 0.5% impedance bandwidth, more than 22%dB port-to-port isolation and 7%dBi antenna gain at the centre frequency of 5.8%GHz was measured. Its percentage bandwidth is less than that of the conventional patch because of the increased quality factor at the distorted patch mode resonance. To improve the impedance bandwidth of the antenna, a multilayered design achieves broader impedance bandwidth and higher antenna gain than that of single-layer design. A 12.5% impedance bandwidth is achieved and the average antenna gain is measured at about 11.2%dBi. Bandwidth enhancement is achieved by introducing one more resonance near the operating frequency, whereas antenna gain is enhanced because of the increase in effective antenna volume. Within the operating frequency band, more than 23%dB measured port-to-port isolation is achieved.