Analysis of some techniques to enhance the bandwidth of handset antennas using metallic strips

Due to the huge increment of the number of bands in cellular devices, techniques to increase the bandwidth of handset antennas are needed. The technique proposed here consists in electrically enlarging the ground plane by using a metallic strip at the opposite edge of the handset antenna location. The proposed metallic strip tunes the ground plane mode to effectively improve the bandwidth at the low frequency region (≈900 MHz) while keeping the same antenna volume. Simulations and measurements demonstrate the metallic strip excites the resonance of the ground plane mode improving the bandwidth. The proposed technique is applied to a dual-band (900-1800 MHz) planar inverted F-antenna providing a measured bandwidth enhancement of around 2 times at the low frequency region while keeping the same performance at the high frequency region (≈1800 MHz).