Single-fed Dual Band UHF-GPS Helical Antenna

INTRODUCTION A GPS antenna would have the right hand circular polarization, an upward pointing radiation pattern, high gain of about 4 dB and axial ratio of 3 dB max. Back lobes are undesired. The operating frequency is 1575 MHz. The expected bandwidth is 10 MHz. Therefore the expected operating range of frequency is from 1570 – 1580 MHz. However, it has also been found that the polarization requirement of RHCP is desired, but may not be a strict requirement due to highly scattered environment. [1] This paper presents a dual band antenna design for a portable handset chassis of 130 mm x 55 mm operating at both UHF(400430 MHz) and the GPS band with linear polarization. The design utilizes the concept of multiple pitch helixes to provide multiple resonant lengths only a single-element structure, thus ensuring both the flexibility and the simplicity of the design.