Printed Square Quadrifilar Helix Antenna (QHA) for GPS Receiver
Wang-Ik Son#1, Won-Gyu Lim#2, Moon-Que Lee*3, Sang-Bo Min@4, Jong-Won Yu#5
1 Korea Advanced Institute of Science and Technology (KAIST), Deajeon, Korea email@example.com
The University of Seoul (UOS), Seoul, Korea
Actenna Corporation, Seoul, Korea firstname.lastname@example.org
Abstract— A new printed square quadrifilar helix antenna (QHA) for circular polarization (CP) is proposed and experimentally investigated for the application as a GPS receiving antenna in frequency range of about 1.575 GHz. To increase the input impedance of QHA, we use the folded inverted-F antenna as a helix. Experiment results show that the proposed antenna has a 3-dB beamwidth of more than 120° and a front-to-back ratio of more than 15 dB. Also, the proposed antenna shows the peak gain of -2.5 dBic and the axial ratio under 0.5 dB in wanted frequency band.
Global Positioning System (GPS) is a satellited-based navigation system to provide instantaneous 3D position, velocity and time information almost anywhere on or above the surface of the earth at any time . In GPS system, the design of the antenna is one of the most important aspects for receiving signals from satellites exactly. The antenna is expected to cover as many satellites as possible over the hemisphere, with high rejection of the multipath and cross polarized signals.
Fig. 1 The geometry of the proposed antenna (Prototype: Wa=10mm, Ha=10mm, We=0.7mm, Le=1.5mm, He=2.5mm, =80°)
In this paper, we proposed a compact printed square QHA for GPS application. To increase the input impedance of QHA, we used the folded inverted-F antenna as a helix. Also, the radiation efficiency is increased.
Circularly polarized (CP) patch antennas have been widely
II. DESIGN OF PRINTED SQUARE QHA
good circular polarization. But a CP patch antenna has a high backward radiation as the size of ground plane is reduced . This means that the antenna has lesser forward radiation and receives more noise from the bottom. So, the C/N of the antenna is reduced. The quadrifilar helix antenna (QHA) invented by Gerst ,  consists of four tape helices equally spaced circumferentially on a cylinder and fed with equal amplitude signals with relative phases of 0°, 90°, 180°, and 270°. This antenna is suitable for GPS receiver antenna because of its broad beamwidth and broad circularly polarized beamwidth. Also it has a low backward radiation when the size of ground is reduced. Recently, the size of the QHA for GPS is reduced more and more for using in handheld mobiles , . As the size of QHA gets smaller, the mutual coupling between the helix is increased. So, the input impedance is smaller and the
radiation efficiency is decreased .
Fig. 1 shows the geometry of the proposed compact square printed QHA. The antenna is mounted above a grounded FR4 substrate (thickness 0.6mm, relative permittivity 4.6, and size 11.5×11.5 mm2). In a grounded substrate, the feeding network is implemented to produce four equal amplitude signals with relative phases of 0°, 90°, 180°, and 270° to generate circularly polarized waves. Each inverted-F helix of QHA, printed on a RO4003 substrate (thickness 0.5 mm, relative permittivity 3.38), is wound by oneself. Each helix has a length of 39 mm, width (We) of 0.7 mm and pitch angle ( ) of 80° to resonate in GPS frequency band. Four printed helices are combined into a square QHA using two fixing plates. The width (Wa) of the combined antenna is 10 mm and the height (Ha) is also 10 mm. To increase input impedance, there is a shorted matching line in each helix, which is used as an inverted-F antenna. The distance between a helix and a match-