A wide-band circularly polarized L-probe coupled patch antenna for dual-band operation

This paper presents the design and testing of a dual-band circularly polarized patch antenna. The portion of the antenna for upper band operation consists of two stacked circular patches which are supported by the plastic posts in the air. The patches are excited by four L-probes which are located sequentially under the circumference of the lower patch. The distance between the upper patch and the ground plane is about 0.1 free space wavelength at 2.492 GHz. This upper band portion possesses an impedance bandwidth of 54.9% (SWR/spl les/2) and a 3-dB axial ratio bandwidth of 47.7%. The antenna peak gain is 8 dBi. For dual-band operation, a larger circular patch for lower band operation is added below the upper band patches. The lower band patch is also coupled by four L-probes sequentially. The integrated antenna has an impedance bandwidth of 43.9% (SWR/spl les/2) and a 3-dB axial ratio bandwidth of 33% for the lower band, while an impedance bandwidth of 55.2% (SWR/spl les/2) and a 3-dB axial ratio bandwidth of 44.7% can be obtained for the upper band. Both bands have a peak gain of around 7.8 dBi.

I. Introduction

In RECENT years, there has been enormous growth of telecommunications services in the L-band frequencies such as radar tracking, global positioning satellite (GPS), and mobile communications. The use of circularly polarized (CP) antennas is rife in these areas since they can provide better mobility and weather penetration than the linearly polarized antennas. For GPS, most of the current receivers only operate at the L1 frequency of 1.575 GHz with right-hand circular polarization (RHCP). In order to obtain more accurate information from the transmitter, a differential GPS design is employed at the receiver. Therefore, a CP receiving antenna that can cover both L1 and L2 (1.227 GHz) frequencies is required.