Citation
Abstract
A fast acquisition algorithm for the Galileo suppressed carrier, subcarrier, and data symbol signals under low data rate, low signal-to-noise ratio (SNR) and high carrier phase-noise conditions has been developed. The algorithm employs a two-arm fast Fourier transform (FFT) method utilizing both the in-phase and quadrature-phase channels of the carrier. The use of both channels results in an improved SNR in the FFT acquisition, enabling the use of a shorter FFT period over which the carrier instability is expected to be less significant. The use of a two-arm FFT also enables subcarrier and symbol acquisition before carrier acquisition. With the subcarrier and symbol loops locked first, the carrier can be acquired from an even shorter FFT period. Two-arm tracking loops are employed to lock the subcarrier and symbol loops with the carrier loop open. In addition, a new method is introduced for loop parameter modiffcation to achieve the final (high) loop SNR in the shortest time possible. The fast acquisition algorithm is implemented in the Block V Receiver (BVR). This article describes the complete algorithm design, the extensive computer simulation work done for verification of the design and the analysis, implementation issues in the BVR, and the acquisition times of the algorithm. In the expected case of the Galileo spacecraft at Jupiter orbit insertion, P =N = 14:6 dB-Hz, R = 16 symbols per sec, and the predicted acquisition D o sym time of the algorithm (to attain a 0.2-dB degradation from each loop to the output symbol SNR) is 38 sec.
Details
- Volume
- 42-118
- Published
- August 15, 1994
- Pages
- 83–114
- File Size
- 681.5 KB