Design of Cognitive Radio Antena Based on Excitation Switching Mechanism

Abstract

In this thesis, I propose a four-port coplanar antenna for cognitive radio applications. The proposed antenna consists of a coplanar waveguide (CPW)-fed ultra-wideband (UWB) antenna and three inner rectangular loop antennas. The UWB antenna is used for spectrum sensing, and the loop antennas are used for communications. The UWB antenna and three loop antennas are printed on the same surface of an FR-4 substrate with dimensions of 42 mm ⨯ 50 mm ⨯ 0.8 mm. The entire UWB spectrum of 3.1 GHz - 10.6 GHz is fully covered by the CPW UWB antenna, which is fed by Port # 1. The three loop antennas cover three spectrum bands. In addition, each antenna can cover the UWB frequency band partially for communication purposes. The first loop antenna, connected to Port #2, operates from 2.96 GHz to 5.38 GHz. The second loop antenna, coupled to Port #3, satisfies a -10 dB reflection coefficient from 5.31 GHz to 8.62 GHz. The third loop antenna, fed by Port #4, operates from 8.48 GHz to 11.02 GHz. A high isolation level (greater than 17.3 dB) is realized among the UWB antenna and three loop antennas without applying any additional decoupling structures. The realized gains of the UWB antenna and three loop antennas are greater than 2.7 dBi and 1.38 dBi, respectively.