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This presents a printed antenna using the high-impedance ground plane (HIGP) structure in order to improve its radiation performances. The HIGP is a kind of electromagnetic bandgap (EBG) structure to decrease surface waves and to bring an improvement of side lobe level, and to reduce the mutual coupling between the two antennas. As compared to a printed antenna without HIGP, the measurement results show that a 5 to 10 dB reduction in the back lobes and an antenna gain for about 2 dBi addition. Several properties of the proposed antenna performances such as impedance bandwidth, radiation pattern and measured gain have been confirmed experimentally in detail.

New design of a dipole antenna with rectangular fractal shape radiator element with two operating bands for radio frequency identification (RFID) is presented. By using fractal shape slot and metal meander patch, the proposed antenna has the wide and dual measured return loss bandwidth. Besides, the omnidirectional radiation pattern of the design antenna cover the entire frequency range including ultra high frequency (UHF, 860 MHz~960 MHz) band and microwave (2.45 GHz) band has been obtained. Several properties of the proposed antenna for dual-band operation such as impedance bandwidth, radiation pattern and measured gain have been investigated numerically and experimentally in detail.

A CPW band-stop filter that has a tapered-shaped defected ground structure (DGS) is demonstrated. The proposed band-stop filter includes symmetrical tapered-shaped DGS and a CPW-fed excitation to obtain two resonance frequency nulls and wider -lOdB operating bandwidth. By modifying tapered-shaped DGS structure and centre strip width (w), the operating bandwidth can be easily adjusted. The simulated and measured results show accepted S-parameters. On other designs, the multisections filters using tapered-shaped DGS structure and CPW filter with dual-tapered-shaped DGS are designed and experimented.

A tapered monopole antenna that has a frequency band notch function is proposed. The antenna includes a semicircle shaped patch, two semicircle ground planes and a CPW-fed excitation to cover the ultra- wideband frequency operation (3.1 GHz ~ 10.6 GHz). By modifying the U-shaped slot, the frequency band notch within the operating bandwidth can be easily changed. The measured results show a return loss bandwidth of 12.3 GHz (2.7 GHz ~ 15 GHz), omnidirectional radiation patterns and reasonable gain over the UWB operating bandwidth.

A novel and simple structure for a CPW-fed half-loop antenna is presented. The proposed antenna covers the Ultra-Wideband (UWB) bandwidth (3.1~10.6 GHz) to even higher band (~20 GHz) for VSWR