Modeling and Measuring of Weak Frequency Selectivity in OFDM Modulator

Weak frequency selectivity in OFDM modulator is usually caused by imperfect D/A conversion and non-ideal filtering. Due to the weakness of this inherent frequency selectivity in OFDM modulator, it is hard to estimate the impact of this frequency selectivity in the output of modulator under the influence of circuit noise, which presents a challenge in performance evaluation of OFDM modulator. In this paper, this inherent weak frequency selectivity on modulator output signal is illustrated and analyzed and an experimental base-band model is proposed to well describe the weak frequency selectivity in OFDM modulator. Finally, this model is applied to evaluate a high performance TDS-OFDM modulator with weak frequency selectivity. After the estimation and equalization of the inherent weak frequency selectivity, the MER measure result could reflect the performance of this modulator much more precisely.