This paper describes the linearization of a base-station L-band 500-W GaN Doherty high power amplifier (HPA) driven by OFDM signals. Pre-pulsing characterization is used to extract the gain dispersion of the carrier and peaking PAs due to trap-induced degradation of GaN-on-SiC transistors. Peak drain voltages reached by PA load-lines mainly set the trap states of the carrier and peaking PAs, while the recovery is longer with a dominant time constant of 100μs for this specific GaN technology. When the peak occurrences are below this dominant time constant of 100μs, such as for symbol periods of 16.7 to 66.7μs (i.e., LTE/5G OFDM), the HPA trap-state remains approximately constant in the time interval between voltage peaks, allowing low-complexity linearization of the HPA. With a 10-MHz OFDM signal with peak-to-peak intervals shorter than 100μs, a memory-less digital pre-distortion (DPD) is shown to improve ACLR by 4dB and NRMSE by 1.6 percentage points, as compared to peak-to-peak intervals longer than 100μs when significant trap recovery takes place.
|Title of host publication||2019 IEEE MTT-S International Microwave Symposium (IMS) Proceedings|
|Publication status||Published - 7 Jun 2019|
|Event||2019 IEEE MTT-S International Microwave Symposium (IMS) - |
Duration: 2 Jun 2019 → 7 Jun 2019
|Conference||2019 IEEE MTT-S International Microwave Symposium (IMS)|
|Period||2/06/19 → 7/06/19|
Bibliographical noteAcceptance date is provisional and based on date of conference/call for papers.
- current collapse
- digital pre distortion (DPD)
- Doherty power amplifier
- double pulse
- Gallium Nitride (GaN)
- pre pulse
- trapping effects