Software Solution for Demodulation of a DGPS Receiver using a 32 bit Embedded Microprocessor

• Published in: Eizō Jōhō Media Gakkaishi Vol. 55; no. 8-9; pp. 1178 - 1185
• Main Authors: Asai, Takashi, Sato, Go, Sakamoto, Tadashi, Hase, Tomohiro
• Format: Journal Article
• Language: Japanese
• Published: The Institute of Image Information and Television Engineers 2001
• Subjects: DARC; DGPS; GPS
• ISSN: 1342-6907; 1881-6908
• DOI: 10.3169/itej.55.1178

We describe a software-based method for the demodulation of FM-multiplexed signals in a DGPS receiver by using a 32-bit embedded microprocessor. Demodulation is needed to extract DGPS data from FM-multiplexed signals in DGPS receivers. Currently, dedicated hardware is required for demodulation because it involves many operations. The proposed method based on the use of software, enables demodulation of FM-multiplexed signals by using a 32-bit embedded microprocessor, thus reducing the size and cost of DGPS receivers. Because LMSK demodulation takes up most of the data-processing time in the demodulation of FM-multiplexed signals, the proposed method focuses on mixing, carrier generation, and accumulation of LMSK demodulation. Practical evaluation of this method shows that the processing load for demodulation of FM-multiplexed signals is 12.4 MIPS, while that for GPS receiver using a DGPS receiver is 48.7 MIPS. These results indicate that the proposed method is practical.