Application of the Left-Handed half-loop antenna with wideband tuning to a Cognitive Radio terminal

A compact system for future communication terminals (Cognitive Radio) is presented in this paper. This system is based on two antennas printed on the same substrate board. The total dimensions of the board are 60 mm × 60 mm, which means that it can be integrated into a handheld terminal. The first antenna is a printed monopole with an omnidirectional radiation pattern which senses the spectrum. The other antenna is a narrowband half-loop antenna based on metamaterial Left-Handed transmission lines which is used for the communication function. This antenna can be tuned within the operation bandwidth of the complete system by using variable capacitances (varactor diodes). The complete system is designed to operate from 1.5 GHz to 3 GHz (2:1 Bandwidth). The isolation between the antenna ports is always higher than 20 dB.