Envelope Tracked Pulse Gate Modulated GaN HEMT Power Amplifier for Wireless Transmitters

This paper proposes a complete transmitter prototype for wireless applications using envelope tracked pulsed gate modulated power amplifier (PA). The proposed transmitter architecture is developed using two high power 10 W gate modulated PAs combined in a fashion to operate as a switched voltage source for the range of duty cycles of pulses driving the gates of power amplifiers. These PAs are designed and implemented using packaged GaN HEMT transistors from CREE to operate at the carrier frequency of 2.35 GHz. For a 5 MHz bandwidth WiMAX 802.16e down-link signal with the PAPR of 7.9 dB and the oversampling ratio of 100, the average drain efficiency of 46.2% is achieved at the average output power of 35.8 dBm. Using a 5 MHz bandwidth LTE down-link signal with 11 dB PAPR and centered at 2.35 GHz, the power amplifier delivers the average output power of 33.2 dBm with the average drain efficiency of 46%. The adjacent channel leakage ratio (ACLR) measured for this signal is less than -36.85 dBc at 10 MHz offset from the center frequency of 2.35 GHz.