Diversity Reception in Microwave Links

Introduction

Diversity receiving is an effective technique of information recovery when multi way signal propagation and its corruption take place. There are several well studied approaches and schemes of this technique realization. In the proposed project attention focuses at one of them – intermediate frequency (IF) signal combiner. This approach has both advantages and drawbacks. The most attractive features of mentioned approach are low cost, good compatibility with standard equipment and good adaptation ability.
The purpose of the project is signal quality criteria development, effective signal processing algorithms proposition, hardware prototype elaboration and its experimental testing.

Environment

The system considered consists of the next blocks. Two or more signal sources (QPSK, QAM and another modulation formats like OFDM technology can be used), channel emulator set, IF signal combiner, spectrum analyzer. Ideally complete demodulator and BER tester have to be included in system. The middle two blocks should be elaborated by the team. IF combiner itself is supposed to be consists of weighted signal summer, signal phase and amplitude difference discriminators, signal distortion analyzer, voltage controlled endless phase shifter and controller.
Proposed research is destined for point-to-point or point-to-multipoint microwave links or base stations and not for mobile units.

Research Directions

1. Distortions of a signals with typical modulation schemes at multi path propagation.
2. Development of the robust distortion criterions and signal combining weights for a different conditions.
3. Practical realization and checking of signal analysis and in phase weighted combining.

Project Stages

1. Literature analysis. Simulation of multi way propagation and channel model choice. Electronic components analysis. Development of combiner structure. Signals sources emulators elaboration.
2. GMSK, QPSK, QAM including OFDM processed signals phase discrimination technique simulation and elaboration. Choice of practical ways. Signal processing algorithms development.
3. Combiner system simulation and its parameters estimation. Electrical schematics of laboratory prototype elaboration. Physical hardware design and PCB tracing including signal source emulators. PCBs fabrication, mounting.
4. Combiner prototype and signal sources tuning, its parameters measuring at laboratory conditions. Laboratory experiment with complete diversity reception setup. Experimental results summarizing and analysis.

Contacts

Team leader: Vladimir Prikhodko