Performance analysis of a homodyne receiver in modulated backscattered system for intelligent transportation

Radio frequency transponders are finding increasing applications in intelligent transportation for automatic transactions. Low system cost is one major concern. Modulated backscattering is one such concept, which is attractive in terms of price and simplicity. This paper looks at the major system level issues in the implementation and possible solutions. Based on our study, the scattering from nearby moving objects and carrier leakage are some of the key parameters limiting the sensitivity of the system. An homodyne system was evaluated using a behavioural model based on the discrete time domain, found in HP EESOF, a commercial CAD. Selection of suitable coding with proper filtering is found to be a possible solution for problems due to scattering from moving object. Our results also show that the front end low noise amplifier does not provide any improvement in system sensitivity in systems where carrier leakage is the dominant mechanism limiting the sensitivity. Possible solutions are also discussed