In this chapter we describe operation of a GNSS receiver baseband processor. The place which this chapter occupies in the book is schematically presented in Figure 6.1. It is one of two major components of a GNSS receiver. In the previous chapter we described the other component of the receiver – the RF front end, which takes an RF signal from an antenna, amplifies, down-converts, filters, and digitizes it. A digitized intermediate frequency signal (DIF), also described in the previous chapter, is taken from the output of the front end to the input of the baseband processor. The baseband processor processes the DIF signal and outputs all information carried by the GNSS signal, pseudoranges or code phase observations, carrier phase observations, Doppler, signal to noise ratio, navigation message, and so on.

Do we need all the receiver or just a baseband processor?

If we compare the structure of a generic receiver as it is usually presented, and as illustrated in Figure 6.2, with the flowchart of this book presentation in Figure 6.1, we can see that a navigation processor is omitted from the receiver design. This has been done on purpose. In numerous applications today the navigation processor embedded in the receiver is not actually used, though all conventional receivers have one.