Kah-Wee Khoo

Wideband Circularly Polarized Patch Antenna Using Broadband Baluns

A novel 90deg broadband balun comprising a broadband 90deg Schiffman phase shifter is introduced as a means of enhancing the wideband circular polarization performance of dual-fed type microstrip antennas. The proposed 90deg broadband balun delivers good impedance matching, balanced power splitting and consistent 90deg (plusmn5deg) phase shifting, across a wide bandwidth (~57.5%). A circular patch antenna utilizing the proposed 90deg broadband balun is shown to attain measured impedance(S11< -10 dB) and axial ratio (AR < 3 dB) bandwidths of 60.24% and 37.7%, respectively, for the dual L-probe case; and 71.28% and 81.6% respectively, for the quadruple L-probe case.

Wideband Circularly Polarized Dielectric Resonator Antenna

A circularly polarized quadruple strip feed cylindrical dielectric resonator antenna utilizing a pair of 90deg hybrid couplers is investigated experimentally. The antenna is shown to deliver an impedance bandwidth (S11 < -10 dB) of 34.5%, from 1.75 to 2.48 GHz, and an axial-ratio bandwidth (AR < 3 dB) of 25.9%, from 1.65 to 2.14 GHz. The gain and radiation patterns are found to be stable within the passband.

Wideband Dual-Polarized Patch Antenna With Broadband Baluns

A pair of novel 180deg broadband microstrip baluns are used to feed a dual-polarized patch antenna. The 180deg broadband balun delivers equal amplitude power division and consistent 180deg (plusmn5deg) phase shifting over a wide bandwidth (>50%). We demonstrate that for a dual-polarized quadruple L-probe square patch antenna, the use of the proposed 180deg broadband balun pair, in place of a conventional 180deg narrowband balun pair, provides improved input port isolation and reduced H-plane cross-polarization levels over a wider frequency range, while maintaining low E-plane cross-polarization levels and stable E- and H-plane co-polarization patterns throughout the impedance passband

Ultra-wideband circularly-polarized patch antenna

An ultra-wideband circularly-polarized (CP) microstrip antenna is presented with the introduction of one wideband 90deg feed network. The CP patch antenna experimentally offers a 10-dB impedance bandwidth of 71.7%, 3-dB axial-ratio bandwidth of 81.6% and a gain bandwidth of 52.2% with its highest gain of 8.1 dBi at 1.8 GHz.

Pattern Stabilization of a UWB Antenna on PCB

A sleeved stripline-fed pseudo monopole antenna on PCB is presented for wideband pattern stabilization. Using only a simple rectangular radiator, we focus on the feeding structure to optimize the overall impedance and pattern bandwidths of the antenna. Compared to the conventional microstrip-line feed, the sleeved stripline feed is shown to provide reduced peak gain squinting from the boresight gain, at the lower UWB band (3.1-5 GHz). With stabilized radiation patterns, the proposed antenna configuration is suitable for UWB array applications with inherently narrow beamwidths.

Dual L-probe proximity-fed rectangular patch antenna using a broadband balun feeding network

A broadband microstrip balun is used as a novel feeding network for a dual L-probe proximity-fed rectangular microstrip patch antenna. It is found that this implementation achieves an impedance bandwidth of 37.2% (SWR<2) and 33.2% (SWR<1.5). The far-field radiation patterns are stable throughout the passband (1.63 GHz-2.375 GHz), also demonstrating continuous high gain (8 dBi and above) and consistently very low H-plane cross-polarization levels (not exceeding 29.5 dB).

Optimal UWB Waveform Design for Antenna Dispersion Compensation

A new pulse design method for Ultra-wideband (UWB) radios is proposed. By precisely formulating the effective isotropic radiated power, the proposed method can properly pre-compensate the antenna dispersion effects. Compared to the existing waveform design methods, the proposed method can provide much more efficient utilization of the FCC assigned spectrum.

A Compact Wideband Printed Wire Antenna for Wireless Communications

This paper presents a compact dual-band printed-circuit-board wire antenna for wireless communications applications. The proposed wire antenna in F-shape with a shorted parasitic element can offer two separate impedance bandwidth of about 0.8 GHz (2.3 GHz~3.1 GHz) and 2 GHz (4.1 GHz~6.1 GHz) for a return loss less than -10 dB. Moreover, the antenna remains compact in size, making it a good candidate for Bluetooth and wireless local area network (WLAN) operation in the 2.4 GHz band and 5.2/5.8 GHz band. Measured results, including return loss and Smith chart, are presented