This paper presented an ultra-wideband (UWB) bandpass filter using broadside-coupled microstrip-coplanar waveguide structure. The filter consists of a microstrip line coupled to a coplanar waveguide (CPW) that was fabricated on the ground of the microstrip line. The proposed filter has been simulated, fabricated and measured for UWB system. The measured results demonstrated the UWB properties from 3.0GHz to 10.63GHz (-10 dB bandwidth) and the potential to be wider. An three-section filter shown insertion loss at central frequency is about 0.32dB and very flat over the whole band. The group delay, which is important to an impulse radio UWB system, is about 0.42 ns over the most central band, and less than 0.95 ns over the whole band. The filter also exhibited a good performance outside the band, both at low frequency end (to meet FCC limit) and high frequency end higher than 18GHz with insertion loss larger than 30 dB.

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We propose a millimeter-wave antenna to serve as an element antenna for a multi-sector switched-beam antenna, which can be fed by a post-wall waveguide. Several tapered slot antennas are connected to an aperture of an H-plane sectoral post-wall horn antenna whose radiation pattern is narrowed in the H-plane to further narrow the pattern in the E-plane. Moreover, the aperture of each tapered slot antenna is loaded with a dielectric to increase the gain. We designed an antenna whose gain is over 16 dBi in the frequency band of 57-66 GHz. The wideband property is experimentally examined.Index Terms-Millimeter wave, post-wall, horn antenna, tapered slot, wideband

This paper presented a dual-band ultra-wideband (UWB) bandpass filter. The filter is based on a novel UWB bandpass filter structure, proposed by authors recently, which consists of a broadside-coupled microstrip-coplanar waveguide and exhibited its excellent ultra-wideband property. The dual-band operation was implemented by integrating a stub in the broadsidecoupled conductors. The resonance of the stub introduces a narrow rejection band in the UWB passband which then results in a dualband filtering. Such a dual-band UNWB bandpass filter is strongly required in practical systems in order to avoid the interference between the UWB radio system and existing radio systems. The rejection band can be easily designed to some specific frequency band(s) by tuning the length of the stub. Simulation, design, fabrication and measurement of dual-band UWB bandpass filters have been carried out mainly following FCC's spectrum mask. The proposed filters demonstrated both excellent ultra-wide bandwidth (from 2.8 GHlz to 10.2 Gllz) and rejection performance (> 50 dB at rejection frequencies), as well as good out-band performance better than the requirement of FCC's mask.

Abstract-In this paper, we have presented the double-layered coplanar patch antennas of enhanced impedance bandwidth and adjustable conductor-backed coplanar waveguide feed lines. The proposed structure retains the advantage of laying the coplanar patch and coplanar waveguide (CPW) feed line on the same surface, which makes direct integration with other devices easier. In addition, the substrate thickness of the radiating patch can be adjusted to achieve a wider impedance bandwidth while the dimensions of the CPW feed line are kept unchanged. Simulation has been done by using commercial electromagnetic (EM) simulation software. Four testing antennas, which have centre frequency at about 10 GHz, were designed. The four testing antennas had the same total thickness, but different thickness combinations. From the measured return loss, gain, and radiation patterns of the antennas, it was demonstrated that different thickness combinations do not affect the characteristics of the antennas seriously. Therefore, the dimensions of the CPW feed structure of the antennas can be adjusted individually and can be selected for different applications.Index Terms-Broad-band antenna, coplanar waveguides feed line, planar antenna.

Dual-frequency slot antennas with different polarization combinations are studied in this article. The antenna is a single-arm spiral slot fed by a microstrip line. A comparison between the circular polarization (CP) design methods of a shorted ring slot antenna and a spiral slot antenna is first made. By the comparison results, a design for dual-frequency CP spiral slot antennas is then drawn. Moreover, it is found that, by rotating the spiral slot, the polarization senses at the two operating frequencies can be varied among three different combinations, including (left-handed CP, right-handed CP), (right-handed CP, lefthanded CP), and (linear polarization, linear polarization). Simulation and experimental results for the performances of the antenna operating at each polarization combination are shown in detail.

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