OFDM Inter-carrier Interference Due to Radio Frequency Synthesizer Phase Noise

This work presents the effects of radio-frequency Local Oscillator non-idealities on OFDM inter-carrier interference. The synthesizer has the main role on modulation and demodulation process of base band IQ signals to radio frequency channels which need to fulfill several requirements imposed by standards specifications. Phase and frequency stability are crucial, since the synchronization of the entire system depends on the accuracy of this circuit. The discussed OFDM system is based on a simulation scenario including radio-frequency channel conversion considering Local Oscillator with configurable phase noise power and bandwidth. This feature allows the study of global system based on Local Oscillator output spectrum. Sub-channel spacing, cyclic redundancy and pulse shaping are configurable. The obtained results indicate that free run oscillator phase noise characterization is not appropriate when the Local Oscillator in the radio-frequency front end is based on synthesizer architecture. System evaluation is based on error vector magnitude. The relation of this metric with the Local Oscillator phase noise allows the performance estimation of the global system