Quantitative Analysis of RF Signals: Implementation of a Software-Defined Radio signal analyser


Nowadays, communications satellites are widely used to exchange data, broadcast TV and radio, provide internet access or even for military applications. They allow covering a widespread area without having to deploy a series of ground equipment to convey a piece of information over countries or continents. Consequently, placing a satellite into orbit as a “space repeater” is much more profitable than building a worldwide ground network to interconnect each part of the world. Nevertheless, because of the atmosphere and the distance separating satellites and ground stations, signals are strongly attenuated and distorted when they reach the final receiver. The noise that has been added to the signal during its propagation and its reception strongly affects the performance of the link. In order to satisfy customers and ensure quality of service, it is of prime concern to assess the quality of the received signals. Indeed, by carrying out measurements on the received signals, it is possible to retrieve in real time some characteristics about the physical layer of the communication channel – may it be specific properties about the atmosphere, robustness of the type of modulation against the current noise, or power issues due to an amplifier dysfunction on the satellite – and take some measures to cope with any issues that might occur.

Signal analysers are measurement platforms to retrieve some information about the quality of a received signal. It displays some figures of merit of the signal to assess it in a quantitative way. The aim of this project is to create a signal analyser using an existing hardware of the USRP family of products as an RF front end and Labview to compute the measurements. A USRP product can be used as a receiver to demodulate, decode and do some digital processing on the carried information. Thus, the signal analyser to be implemented would be “embedded” on the receiver, hence the added-value of this project.

This report will first address the scope and objectives of the project, then the implementation of the signal analyser using Labview will be issued. Finally, tests and results on the analysis of real signals from satellites will be assessed to define further potential improvements if any.

I - Scope and objectives of the project

1. Proceedings of the project

2. State of the art on signal analysis

3. Lab Setup

4. Signals to be measured

II - Implementation

1. Definition of inputs and ways to compute the outputs - Theory

2. Simulation

3. Moving from simulation to acquisition of real signals

III - Tests and validation

1. Finding a signal to be analysed

2. SDR Signal Analyser – Analog Measurements

2.1. Estimation of the power of the noise

2.2. Measurements regarding the useful signal and approximation of the signal-to-noise ratio

3. SDR Signal Analyser – Digital Measurements

IV - Improvements

1. Synchronisation issues for digital measurements

2. Estimation of the BER