DESIGN OF A COMPACT BROADBAND ANTENNA WITH MICROSTRIP-TO-CPS TRANSITION FOR IR-UWB APPLICATIONS

Abstract

Since the era of smart phones starts, wireless communication services, such as W-CDMA, GSM, LTE, GPS, BT, UWB, and WLANs, have attracted people with much more interest. A lot of wireless devices is developed and released into the commercial market for every day. It seems that the advance in technologies is also constantly evolving forward. However, undoubtedly frequency bands are not boundless resource. It costs very high and a use of the frequency is regulated by the law of each country. This is to prevent interference to other technologies in nearby. For this reason, an interest in UWB technologies using short pulses still exists and is still on an increase. This thesis demonstrates a novel ultra-wideband antenna for impulse-radio UWB applications. A compact ultra-wideband (UWB) quasi-Yagi antenna with microstrip-to-coplanar stripline transition balun is presented in this paper. The transition balun using Klopfenstein taper is designed in unbalanced back-to-back. A planar balun with very short length (5.1 mm) has a 3dB back-to-back insertion loss bandwidth from 4.3 GHz to 10.8 GH. The proposed antenna has end-fire pattern, a good front-to-back ratio of 12.9 dB at 7 GHz, and wide bandwidth enough to cover the Korea UWB band regulated by Telecommunications Technology Association. The proposed quasi-Yagi antenna yields end-fire radiation pattern in the frequency range of 6.1 GHz to 10.7 GHz with a measured peak gain of 6.2–7.7 dBi. Predicted and measured results of the antenna show good agreement with return loss of less than -10 dB over the frequency of from 6.1 to 10.7 GHz and with radiation performance.