TABLE OF CONTENTS Phillip W. Ward
NAVWARD GPS Consulting
John W. Betz and Christopher J. Hegarty
The MITRE Corporation
In this chapter, we examine the properties of the GPS satellite signals, including frequency assignment, modulation format, navigation data, and the generation of PRN codes. This discussion is accompanied by a description of received signal power levels as well as their associated autocorrelation characteristics. Cross-correlation characteristics are also described. The chapter is organized as follows. First, background information on modulations that are useful for satellite radio-navigation, multiplexing techniques, and general signal characteristics including autocorrelation functions and power spectra are discussed in Section 4.2. Section 4.3 describes the legacy GPS signals, defined here as those signals broadcast by the GPS satellites up through the Block IIR SVs. Section 4.4 presents an overview of the GPS navigation data modulated upon the legacy GPS signals. As discussed in Chapter 3, new civil and military signals will be broadcast by the Block IIR-M and later satellites. These new signals are discussed in Section 4.5. Finally, Section 4.6 summarizes the chapter.
Binary phase shift keying (BPSK) is a simple digital signaling scheme in which an RF carrier is either transmitted as is or with a 180 phase shift over successive intervals in time depending on whether a digital 0 or 1 is being conveyed (e.g., see [1]). A BPSK signal, as illustrated in Figure 4.1, can be thought of as the product of two time waveforms the unmodulated...
