Increasing the efficiency of electrically small antennas across a large bandwidth using matching networks

We present a tuning strategy for electrically small antennas that have high reactive parts and are suitable for small PDA devices. Our approach is to first bring the small antenna to resonance by minimizing the reactive part of the impedance prior to matching. To verify this concept, a spiral antenna is used for operation in the 800-1200MHz frequency range. The matching network is a reconfigurable double stub tuner whose stubs are loaded by MEMS capacitor banks. Results show significant enhancement in efficiency using our proposed approach.