Efficiency Enhancement of SigmaDelta Modulator Based Transmitters Using Multi-Level Quantizers
This paper is concerned with the performance of first- and second- order sigmadelta modulator (??M) based transmitters with an Orthogonal Frequency Division Modulation (OFDM) signal and Code Division Multiplexing Access (CDMA) signal. In particular, the WorldWide Interoperability for Microwave Access (WiMAX) and Interim Standard 95 (IS-95) down link signals have been used for this study as test signals. The simulation and experimental results showed that the performances of the ??M for both signals are improved by increasing the number of quantization levels and the order of the ??M circuit. A ?? modulator based transmitter using a switching mode power amplifier was developed and built for validation purposes. It is found that the increase of the quantization level of the ?? modulator from 2 to 5 leads to a substantial improvement in the measured power efficiency of the transmitter from 5% to 42%. This improvement in efficiency is in good agreement with simulated and measured results obtained using simulink and FPGA board respectively.
cdma wimax is-95 power amplifier fpga performance evaluation sigma delta modulators