Abstract
Switched mode RF power amplifiers (PAs) under bitstream modulations, such as bandpass or envelope delta-sigma modulations (EDSMs), have received increasing attentions over the past years. Such amplifiers offer high power efficiencies under power back-off conditions with pulse train voltage waveforms yet maintain their linearity in amplification through digital coding and modulations. This paper presented an X-band switched mode PA based on the pulsed load modulation (PLM) technique with multilevel EDSM to realize broadband efficient amplification of nonconstant-envelope signals. The complete theory of power efficiency for PLM under three-level EDSM is presented. The X-band PA is implemented with 0.25- μm discrete GaN transistors from Triquint. Both two-level and three-level EDSM techniques were tested and compared in regard to their quantization noise levels and power efficiencies. Under the three-level EDSM, the PA delivered 34.6-dBm output power for a WCDMA uplink signal with 100-MHz bandwidth and 5.3-dB peak-to-average power ratio at the carrier frequency of 9.2 GHz. The measured drain efficiency and the power-added efficiency with the modulation were 34.6% and 26.5%, respectively. The adjacent channel leakage power ratio at the output was measured to be 32.2/32.3 dBc at the 100-MHz offsets without using digital predistortion.
Original language | English |
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Article number | 7565644 |
Pages (from-to) | 3643-3653 |
Number of pages | 11 |
Journal | IEEE Transactions on Microwave Theory and Techniques |
Volume | 64 |
Issue number | 11 |
DOIs | |
Publication status | Published - Nov 2016 |
Externally published | Yes |
Keywords
- Bitstream modulations
- GaN
- X-band
- envelope delta-sigma modulation (EDSM)
- pulsed load modulation (PLM)
- switched-mode power amplifiers (PAs)