System Design Details

Receivers
Title	System Design Details
Author(s)	GMV
Level	Medium
Year of Publication	2011

In order to process the L-band signals transmitted from the satellites and compute the navigation solution, a GNSS receiver can be designed to target different applications, markets, and solutions. From single or multi-frequency, single or multi-constellation, to survey or automotive applications, system specification details extend through a broad range of decisions and trade-offs, in order to achieve the best performance desired. The following sections tackle some considerations at a GNSS receiver system design level.

Overview

Most of the current GNSS receiver systems gather (at least) the blocks depicted in Figure 1, although some architecture variations might be present to accommodate different solutions. Besides these blocks, other common receiver components are the power unit (e.g. batteries) or the enclosure (e.g. for ruggedization). All such components and blocks are carefully chosen when a GNSS receiver is designed for a target application, and different considerations are made on the choices and trade-offs involved.

Furthermore, in order for a GNSS receiver to be able to provide the required solution, the specification team should have a clear knowledge of the system as a whole, with special focus on the space segment (satellites, RF signals, modulations and bandwidths) and user segment (hardware, receivers and applications). At system design level, it is the interface between these two segments that is targeted, and a receiver is tailored not only to provide PVT (or other) solutions, but also to take full advantage of the characteristics of the signals received and their respective transmitting satellite constellation(s).

Block diagram

The figure shows the main blocks inside a GNSS receiver system, as they represent most of the dimensioning and engineering work involved in a receiver system specification and design.

Figure 1: Block diagram of a typical GNSS receiver, illustrating the different parallel processing channels.

The different subsets can be categorized in antenna, front end, baseband processing and applications processing:

• Antenna: L-band antenna, responsible for capturing the GNSS signals transmitted (as well as noise and possible interference).

• Front End: The hardware front-end typically down-converts, filters, amplifies, and digitizes the incoming signals.

• Baseband processing: Several signal processing routines are used to acquire and track the different signals.

• Applications Processing: Depending on the envisaged application, the receiver performs different tasks with the resulting GNSS information, and provides meaningful results to the user.

Related articles

• Generic Receiver Description
• Receiver Types
• Antennas
• Front End
• Baseband Processing
• Applications Processing