Theoretical Analysis of Performance Degradation Due to Phase Noise and I/Q Imbalance in MQAM-OFDM Systems

Knowledge about the quantitative link between the signal degradation and hardware parameters is essential for a reasonable design of the MQAM-OFDM system. In this paper, we investigate joint effects of phase noise and I/Q imbalance in a demonstrative zero intermediate frequency MQAM-OFDM systems, and propose analytical equations to calculate the signal distortions evaluated by error vector magnitude (EVM). Theoretical analysis is in particular capable to deal with PLL phase noise and frequency-selective I/Q imbalance. Moreover, it indicates that distortions due to PLL phase noise can be calculated from power spectral density (PSD) of oscillators, which simply can be measured by spectrum analyzers. Simulation results show perfect agreement with those obtained by theoretical analysis, which could be used to estimate MQAM-OFDM system degradation and instruct system designs, with no need to run extensive simulations.