Improved, low-profile antenna for switched-beam and energy density diversity schemes

Several low-profile diversity antenna designs based on the combination of multiple notch and multi-element monopole antennas have previously been developed for cellular telephone communications. All of these designs suffer from the shortcomings of the notch antenna; narrow bandwidth and poor return loss. Through the use of tuning and impedance matching elements, enhanced performance of the notch antenna can be achieved. The incorporation of these elements directly into the diversity antenna system allows an improved diversity antenna (developed and tested for operation in the ISM band of 2.4 to 2.5 GHz) to be realized without any increase in package size. The improved bandwidth of these antennas makes them suitable and attractive for high-data-rate digital mobile communication systems.