A differential-fed ultra-wideband patch antenna with triple band-notched characteristics is proposed. The antenna consists of an octagonal slot ground and two quasi-square radiating patches. By employing splitring resonators (SRRs) etched on the radiating patch and complementary SRRs etched on the ground plane, triple-notched bands are obtained to filter the 3.5 GHz WiMAX, 5.5 GHz WLAN and 8 GHz ITU bands. The measured 10 dB impedance bandwidth is from 2.55 to 10.86 GHz, along with triple-notched bands of 3.21-3.86, 4.93-6.13 and 7.87-8.89 GHz. In addition, the proposed antenna achieves relatively low cross-polarisation and stable gain. Good agreement is achieved between the simulated and the measured results. Introduction: Recently, ultra-wideband (UWB) wireless communication technology has attracted much attention due to its wide bandwidth, low power consumption, high data transfer rate and low cost. The UWB antenna, as an important component of wireless communication systems, requires a wide bandwidth of 3.1-10.6 GHz for practical applications. Various UWB antennas designed for single-ended signal operation have been proposed in [1-3]. With the wide application of differential signal operation in radio frequency systems, the conventional single-ended antenna cannot be directly connected to the differential circuits. A balun is needed to transform differential signals into singleended signals between the differential circuits and the conventional antennas, which causes additional losses and decreases the impedance matching bandwidth. Hence, differential-fed antennas excited by two signals with out of phase but equal amplitude are more suitable to be directly integrated with differential circuits. As is well known, some narrow-band communication systems such as WiMAX 3.4-3.69 GHz, WLAN 5.15-5.825 GHz and ITU 8.025-8.4 GHz will cause electromagnetic interference with the UWB system. Therefore, differential UWB antennas with band-notched characteristics are very necessary. So far, many differential UWB antennas have been presented. In the design of [4], a differential-magneto-electric dipole antenna is proposed for UWB applications, but the overall size of the antenna is too large, and the proposed antenna is not a single-layer structure. A differentialfed microstrip antenna is presented in [5]. However, the antenna does not have band-notched characteristics. A differential UWB patch antenna with band-notched characteristics is developed in [6], but the rejected band only covers 5.2-6.0 GHz. In this Letter, a differential-fed UWB patch antenna with triple bandnotched characteristics is proposed. Split-ring resonators (SRRs) and complementary SRRs (CSRRs) are, respectively, embedded in the radiating patches and the ground plane to filter the 3.5 GHz WiMAX, 5.5 GHz WLAN and 8 GHz ITU bands. The simulation and analysis for the proposed antenna were performed using the electromagnetic simulator ANSYS HFSS 13. Details of the antenna design and the measured results are presented and discussed.
