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WSEAS TRANSACTIONS on ELECTRONICS Manuscript received Apr. 25, 2007; revised July 14, 2007

Guo-Shing Huang

Time Syntonization and Frequency Stabilizing Using GPS Carrier Phase with Extension Controller


Department of Electronic Engineering, National Chin-Yi University of Technology 35, Lane 215, Chung-Shan Rd., Sec. 1, Taiping, Taichung, TAIWAN, R. O. C. e-mail: hgs@ncut.edu.tw

Abstract: - This study discusses time syntonization and frequency stability calibration using GPS carrier phase measurements. Thus far most papers on this subject discussed using two GPS receiver measurements, and performing frequency stabilizing and vehicle positioning with the double differences. This paper proposes using a dual frequency GPS receiver and a novel extension controller neural network algorithm that can achieve the frequency stabilizing and coordinate positioning. The oscillation frequency of the rubidium atom clock is selected first as the satellite atom clock oscillation frequency as the criterion for adjusting the GPS receiver oscillators frequency. The receiver’s oscillation frequency is synchronized with the reference atomic clock

oscillation frequency using the designed extension controller and extension neural network. To finish the frequency stabilizing and time syntonization, the time can be calibrated and the position precision on the vehicle improved. The position precision can be improved from about 3.5 meters to about 1.5 meters using the

extension controller. The time error is improved from about 4.85×107 seconds to about 2 .8 5 × 1 0 8 seconds. Using the extension neural network to verify the position precision allows improvement from about 3.5 meters

to about 1.3 meters. The time error is improved from about 4.85×107 seconds to about 2 .8 × 1 0 8 seconds. The system was verified experimentally as satisfying the exactness, feasibility and robustness of the initial concept.

Key-Words: - GPS, Carrier Phase, Extension Controller, Extension Neural Network

1 Introduction

Wireless communication flourishes in high- speed communications, navigation, power systems, data acquisition instrumentation and in numerous other applications. Frequency usage and bandwidth requirements have increased. The extreme accuracy of navigation data is not influenced by time, place, or weather except for shielding the line of sight between the satellites and the navigator. There are global, all-weather, continuous, high accuracy three- dimensional navigation systems with encrypted security. GPS is a high- accuracy navigation system for all vehicles. However, GPS receiver errors reduce the precision of GPS positioning. Transmission errors due to ionospheric and tropospheric activity can cause delay. Because the satellites possess a high-accuracy atom clock and produce the L1 and L2 carrier phase signals, the navigators can access reasonably accurate navigation data through the GPS system in the

world. The internal of each GPS receiver produces a pulse per second when the L1 and L2 carrier phase signals have been received. Thus, the time between the master station and slave station receivers can be adjusted simultaneously to improve the navigator

positioning accuracy. [1][2][3]

Hence, a higher performance



frequency techniques are expected if the GPS carrier phases are considered. The frequency stability of the GPS receiver is the most important factor for positioning. The cycle slip and multipath effects are not critical factors that influence the GPS solution. A new frequency synchronization method is proposed in this paper that uses the GPS carrier phase measurement is proposed in this paper. The idea is realized into a carrier phase frequency synchronization system. [4]

The goal of the system is to steer the receiver clock such that its frequency will follow the

ISSN: 1109-9445

Issue 7, Volume 4, July 2007


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