A dynamic-range-improved 2.4GHz WLAN class-E PA combining PWPM and cascode modulation

A dynamic-range-improved class-E power amplifier (PA) is achieved via combining cascode modulation and pulse-width pulse-position modulation (PWPM). PWPM can avoid the need of supply modulator yielding better power efficiency than the classical techniques. The key pitfall of PWPM is the fact that a high-frequency narrow pulse can be swallowed by the pulse driver, showing zero output when the signal is of a small amplitude. Such a problem is solved by combining PWPM with the cascode modulation. The PWPM is to serve the master mode when the pulse width is sufficiently wide. When the pulse width is adequately narrow, the PA switches to the slave mode, which utilizes an analog control voltage to drive up the cascode device. Such a combined structure results in a high dynamic range. A 2.4GHz WLAN class-E PA is designed in 65nm CMOS to verify the structure. Together with a digital predistortion scheme for AM-AM and AM-PM compensation, the PA exhibits an EVM of 0.55% with an average output power of 21dBm under an OFDM 64-QAM input. The average power-added efficiency is 27%.