High-Current-High-Speed Dynamic Bias Control System Applied to a 100-W Wideband Push-Pull Amplifier

作者：Bacque Ludovic^*; Bouysse Philippe; Rebernak William; Poumier Christian; Lapierre Luc; Nanfack Nkondem Gregoire; Neveux Guillaume; Barataud Denis; Quere Raymond

来源：IEEE Transactions on Microwave Theory and Techniques, 2008, 56(12): 2798-2807.

DOI：10.1109/TMTT.2008.2007079

• Bias control
• efficiency
• envelope tracking
• error vector magnitude (EVM)
• linearity
• power amplifier
• 16QAM
• smart power

This paper presents a dynamic bias control system applied to a high power wideband amplifier. The amplifier used is based on a push-pull topology with LDMOS transistors and works in the 50-500 MHz frequency bandwidth. It delivers a nominal 100 W output power with 60 % power-added efficiency (PAE) when it is fed with continuous signals. When it is driven by a 16QAM modulated signal, 6 dB input power back-off is necessary to keep an error vector measurement below 5 %. This usual back-off technique results in lower PAE (43% in our case). By implementing the proposed bias control system, both 55% PAE and 5% EVM have been reached for 75 W average output power. The drain bias control circuit handles high currents and high voltages (7 A-28 V). The proposed implementation makes use of a class S modulator driven by a Sigma Delta modulator. Up to 1 Mbit/s envelope bit rate can be efficiently and accurately processed by using here dedicated circuits running at 20 MHz clock frequency.

• 出版日期2008-12