Generic Receiver Description

Receivers
Title	Generic Receiver Description
Author(s)	GMV
Level	Basic
Year of Publication	2011

GNSS receivers are responsible for processing the L-band Signals In Space (SIS) coming from the GNSS satellites. This way, a GNSS receiver can be seen as a radionaviagation user device that aims at tracking the GNSS signals in view, in order to correctly demodulate and extract the measurements and navigation information - one example is to decode the transmitted navigation message and calculate the user's position.

Receiver Overview

Although each receiver architecture is tailored to the different GNSS systems applicable and to the target applications, the basic building blocks of a generic GNSS receiver are as shown in Figure 1:

• Antenna - L-band antenna, responsible for capturing the GNSS signals transmitted (as well as noise and possible interference).
• Front End - The hardware front-end typicaly downconverts, filters, amplifies, and digitizes the incoming signals.
• Baseband signal processing - Several signal processing routines are used to acquire and track the different signals.
• Receiver application - Depending on the envisaged task, the receiver performs different tasks with the resulting GNSS information, and provide meaningful results to the user.

Figure 1: Generic Receiver Architecture

The Signals In Space (SIS) arriving at the antenna are down-converted and digitized in the front end block, and the sampled signal is fed onto the signal processing blocks. At this point, the receiver tracks each signal using dedicated channels running in parallel, where typically each channel tracks one signal (i.e. for single frequency users, each channel tracks one satellite), providing pseudo-range and phase measurements, as well as navigation data and additional signal information (such as C/N0).

In the application processing block, the receiver may use the incoming information for different purposes, from computing its own position and velocity, to performing time transfer, or simply collecting data to be post-processed in the ground stations. For a wider discussion on application specifics see GNSS Applications.

In addition to processing the SIS, GNSS receivers may also use aiding information to enhance their solution performance. There are various architectural solutions to cope with aiding information: in fact, this information can be used potentially at any block of the receiver. As an example, when using Inertial Navigation Systems (INS), the sensor information is usually used in the application processing block (although it could also be used as feedback to the baseband processing block for improved performance).

This section tackles the basic functions of the standalone GNSS Receiver.

Related articles

For a detailed description of a generic receiver, please visit the following links:

• Receiver Types
• Receiver Operations