Development of a rapid prototyping frontend for mobile radio propagation measurements

Abstract

Meaningful comparison of theory with actual radio transmission experiments often is impractical due to the lack of readily available radio-frequency (RF)-frontends. Usually, research on new wireless communication techniques takes place long time before proper measurement devices or testing environments are commercially available. This is also true for specialized integrated circuits and frequency selective key components which could be used for building these devices. Therefore, tomorrow's scientific measurement instruments often have to be built with today's technologies.<br />The development strategy and the implementation of such a flexible and scalable high-end radio for multiple input multiple output (MIMO) transmissions was the focus of the research work. The system concept and the interfaces of the RF-frontend were designed such that the frontend works optimally with the SmartSim channel emulator of the Austrian Research Centers GmbH. Modulation and demodulation, and also digital-to-analog and analog-to-digital conversion, are performed by the baseband processing unit of the channel emulator. The aim of the RF part is to perform filtering, amplification and frequency conversion maintaining optimal signal quality. The RF transmitters and receivers are based on a low intermediate frequency (IF) to RF concept and on double heterodyne frequency conversion. Signals up to a bandwidth of 50 MHz at the IF of 140 MHz can be processed by the RF-frontend. Each developed synthesizer module is able to provide local oscilator (LO) power for up to eight transmitter or receiver branches. Additionally, the modules are scalable. So it becomes possible to build up MIMO systems with more than eight channels.<br />Several parameters of the transmitters, the receivers and the LO can be controlled or monitored via micro controller units.<br />