Antenna Systems & Technology - Winter 2015 - (Page 16)

FEATURE ARTICLE Manufacturing of Zero-Centered Antennas for High Precision Positioning with Global Navigation Satellite Systems By Proton Engineering and Topcon Positioning Systems With today's technology, the accuracy of positioning with the Global Navigation Satellite Systems (GNSS) in real time is about 1 to 2 cm, which opens the opportunities for the broad use of the positioning equipment in various businesses like land survey, agriculture, construction and automated vehicles navigation. Topcon Positioning Systems, a California-based company, has developed a variety of antennas for high-precision applications. As an example, Figure 1 shows Fence antenna. The antenna is a stack of two patch antennas with substrates in the form of metal capacitive frames. The antenna operates in two frequency subbands covering the GNSS band from 1,160 up to 1,608 MHz. The antenna is intended for applications to rovers (moving objects). Another example is TA5 antenna shown in Figure 2. The antenna covers the GNSS band and is employed as an antenna element for the ground GNSS reference stations. The reference station antennas are shown in Figure 3 and 4. In Figure 3, a choke ring ground plane antenna CR-G5 is shown while in Figure 4 a convex impedance ground plane antenna PN-A5. All the antennas operate in the GNSS frequency band mentioned above. Antennas are right-hand circular polarized (RHCP). More details about the antennas design and functionality could be found in References 1-5. All the above-mentioned antennas comprise systems of metal parts like capacitive frames in Figure 1 and an array of convex patches of Figure 2. However, one of the most important requirements to antennas for high precision applications is consistency and repeatability of the phase center location and phase pattern. These figures explicitly affect the precision [6]. Within the satellite geodesy community the first quantity is known as phase center offset (PCO) against an antenna reference point and the second one is designated as phase center variations (PCV). To assure the repeatability of PCO and PCV in manufacturing process, special procedures have been developed. Figure 1. Topcon Fence Antenna Figure 2. Topcon TA5 Antenna. 1 - Radome, 2 - Array of convex patches, 3 - Excitation Unit In manufacturing, it has been defined that one of the most sensitive parameters is the phase center offset against the antenna vertical axis of symmetry. The offset is of special interest. With positioning practice, antennas Figure 3. Topcon CR-G5 Antenna Figure 4. Topcon PN-A5 Antenna with zero phase center offset in horizontal plane do not require special orientation with respect to the local azimuth. Such antennas are often referred to as zero-centered. For antenna to be qualified as zero-centered, the common requirement is that the phase center offset in the horizontal plane does not exceed 1 mm. The procedures employed in manufacturing process to assure zero-centered quality (and by doing so, assure overall consistency and repeatability of PCV and PCO) are discussed next. 16 Antenna Systems & Technology Winter 2015 www.AntennasOnline.com http://www.AntennasOnline.com

Table of Contents for the Digital Edition of Antenna Systems & Technology - Winter 2015

Table of Contents
Editor’s Choice
A New Leap Towards True Software-Defined Radio
SON: The Future of LTE Network Deployments and Operations
Manufacturing of Zero-Centered Antennas for High Precision Positioning with Global Navigation Satellite Systems
Mission-Critical Flight Line Testing
Antennas
Components/Subsystems
Test & Measurement
Industry News
Marketplace
Tighter PIM Requirements for Multiband DAS

Antenna Systems & Technology - Winter 2015