Inductor-less envelope modulated radio frequency power amplifier using stacked amplifiers and envelope shaping

An envelope modulated radio frequency (RF) power amplifier (PA) is presented using a `stacked amplifiers´ modulator. The modulator combines the efficiency of class G with the convenience of a charge pump. Since it is a single band modulator, no large inductors or transformers are required. A two level prototype has been developed and tested with a 7.5 dB peak-to-average power ratio 1.4 MHz bandwidth long term evolution (LTE) signal. Envelope shaping was used to improve linearity. Individually the modulator achieved between 54 and 60% efficiency, dependant on the envelope shaping function. When combined with a suitable class E PA, 40% DC to RF efficiency was achieved at 1.38 W output power with the 1.4 MHz LTE signal.