Design of Multimode Triplex Antenna with High Isolation

A multimode triplex antenna with high isolation operating in the X-band is designed in this paper. The proposed antenna consists of a triangular loop, a coplanar waveguide and two tapered microstrip feedlines. Taking advantages of the triangular loop, high isolation performance is achieved in the proposed antenna. And, three different modes are excited by the coplanar waveguide and two tapered microstrip feedlines. Consequently, a multimode triplex antenna is obtained with high isolation. The optimized and measured results show that the operating frequencies of the proposed antenna are 10, 12.8 and 11.58 GHz, which are corresponding to three modes, respectively. Moreover, the isolations between each port are higher than 20 dB, and the corresponding bandwidths are 20% (8.94 GHz to 10.92 GHz), 20% (12.1 GHz to 14.6 GHz), and 12% (11 GHz to 12.45 GHz), respectively. The radiation gains are measured as 3.8, 3.3 and 3.3 dBi at three working frequencies, and cross-polarizations are 22dB, 18dB, and 16dB, respectively.