The Test Bench for FPGA-based QPSK and QAM Modulators in Software defined radio

Abstract

In todays fast evolving mobile communications the requirements of higher data rates are continuously increasing, pushing operators to upgrade the back haul to support these speeds. A cost effective way of doing this is by using microwave links between base stations, but as the requirements of data rates increase, the capacity of the microwave links must be increased. The objective of the paper is the developing the next generation high speed microwave links for the E-band. In the research project there was a need for a testing system that was able to generate a series of test signals with selectable QAM modulations and adjustable properties to be able to measure and evaluate hardware within the project. The developed system was designed in a digital domain using an FPGA platform from Altera, and had the ability of selecting several types of modulations and changing the properties of the output signals as requested. By using simulation in several steps and measurements of the complete system the functionality was verified. The developed system can be used to test several different modulators in other projects as well and is easily extended to provide further properties.