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

Abstract

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.