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WSEAS TRANSACTIONS on ELECTRONICS

Figure 8. The position error using extension neural network.

Figure 9. Time difference between GPS receiver and satellite by using extension neural network.

6 Conclusions

This paper proposed using GPS carrier phase measurements to perform frequency stability and time calibration. Originally, position precision was not high and time error was great. Using an extension controller and extension neural network to adjust GPS receiver oscillation frequency will enhance the position precision and frequency stability.

The advantage of the extension controller is that it produces an extension element model for any required control system. The extension controller

ISSN: 1109-9445

156

Guo-Shing Huang

algorithm estimates

the

oscillation

the relational function

frequency

stability,

among time

syntonization and integer ambiguity, then combines the default value of the relational function. The control targets are controlled one at a time, until satisfactory system control is obtained. The experiment results show that the time error is

improved seconds

from using

4 .8 5 × 1 0 7

seconds to 2 .8 5 × 1 0 8

the

extension

controller.

The

advantage of the proposed approach is the neural network learning mechanism and

combined extension

theory element model. The influences positioning accuracy frequency stability of the GPS

factor that most is the oscillation receiver, the time

syntonization, and extension distance

integer ambiguity. The relational and weighting factor adjustment

are merged to adjust non-ideal interval fast and efficiently.

value into an ideal The entire system

performs to obtain

frequency stability and time syntonization the optimum control result. The time error

is

improved

to

about

3 × 10 8

seconds

after

using

the extension neural network. precision is greatly promoted.

Then

the

position

In the future, we can use the cesium atom clock with higher precision as the foundation for adjusting the receiver oscillation frequency. At the same time, the cesium clock frequency can dispel the multipath effects and estimate the cycle slip error to better improve vehicle position precision. Through wired or wireless transmissions, the proposed method gives all remote stations accurate analysis data. And then the frequency of remote GPS receivers can be syntonized using the extension neural network algorithm. Figure 10 shows an overview of the entire system to achieve frequency stability and time syntonization.

Figure 10. Systematic block diagram of the frequency control process using carrier phase.

Issue 7, Volume 4, July 2007

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