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In this letter, a novel compact quad-band microstrip circular slot antenna using edge-feeding is proposed to support the four wireless communication bands of GPS1.575 (1.525-1.625 GHz), WIMAX3.5 (3.3-3.6 GHz), WLAN2.45 (2.4-2.485 MHz)and WLAN5.2/5.8 (5.15-5.825 GHz). To expand the bandwidth of the GPS band and induce the WIMAX/WLAN band to support quad-band applications without affecting the compactness of the proposed antenna, a good method of implanting two T copper slices at the inner boundary of the two circular slots respectively is adopted. By adjusting the diameter of the two circular slots and the size of the T-shaped patch, resonant frequencies and bandwidth of the antenna are controlled and the multiple operating bands are achieved. In order to further reduce the size of the antenna that an edge-fed technology is used. This antenna has a simpler structure for realizing quad-band characteristics. Then, a prototype of the proposed antenna was successfully implemented, and good radiation performance is observed in all desired bands.

This study shows a high performance of W‐band bandpass filter using a simple structure, which has advantages of low cost and simple process. This filter is composed of four rectangular resonant cavities, which are connected together by series. We designed and optimised the sizes of four cavities and the sizes of coupling holes by Ansoft's High Frequency Structure Simulator 13.0 (HFSS 13.0). The simulation result of the filter shows that it has the centre frequency at 92.62 GHz, 4.07% (3.86 GHz) bandwidth, a 0.4 dB insertion loss in the passband and a 1.51 rectangular coefficient. The measured response of the filter agrees with the simulation result, which has the centre frequency at 92.6 GHz, 4.53% (4.20 GHz) bandwidth, and an average insertion loss less than 0.5 dB in the passband. The rectangular coefficient of test result is 1.61. The simulation result also prove that it is easy to obtain a W‐band bandpass filter which has a centre frequency range from 90 to 100 GHz with a bandwidth ranging from 3 to 9 GHz by slightly adjusting key sizes of the structure, such as chamfer radius and thickness of the iris.

A novel semi-circle-shaped aperture ultrawideband (UWB) antenna with triple band-notched characteristics is proposed, to prevent interference problems due to existing nearby communication systems within the UWB operating frequency. The band-notches are realized by etching one complementary split-ring resonator (SRR) inside a circular exciting stub on the front side, employing a interrogationshaped defected ground structure (DGS) in each side of the ground plane as well as symmetrically adding a pair of open-circuit stubs at the edge of the slot. Tri-band rejected filtering properties in the WiMAX/WLAN are so achieved. Experimental results show that the designed antenna, with compact size of 24×30 mm 2 , has an impedance bandwidth of 2.6-12 GHz for VSWR less than 2, except three frequency stop-bands of 3.3-4, 5.15-5.4 and 5.8-6.1 GHz. Moreover, the antenna has good omnidirectional radiation patterns in the H plane. Besides, time-domain behaviors and the band-notched structures are discussed in detail.

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