Investigation of Input Nonlinearity in Sequential Load Modulated Balanced Amplifiers

• Main Authors: Chu, Chenhao, Sharma, Tushar, Dhar, Sagar K., Darraji, Ramzi, Zhu, Anding
• Format: Conference Proceeding
• Language: English
• Subjects: Aerospace electronics; Broadband amplifiers; high efficiency; Impedance matching; input nonlinearity; Microwave measurement; Modulation; Power measurement; Power system harmonics; second harmonic source; sequential load modulated balanced amplifier (SLMBA)
• ISSN: 2576-7216
• DOI: 10.1109/IMS37962.2022.9865491

This paper investigates the impact of input nonlinearity in the sequential load modulated balanced amplifier (SLMBA) configuration. Theoretical analysis identifies that the utilization of Class-F- 1 control amplifier (CA) can provide high and flat efficiency performance in low-power region and stable balanced amplifier (BA) load modulation in high-power region under second harmonic source (Z_{2S}) variation. The immunity to input nonlinearity of Class-F- 1 operation provides CA flexible Z_{2S} design space in broadband SLMBA realization. Based on the load-pull experimental results, the optimum design space of \angle\Gamma_{2S} over (-90°, 90°) is chosen as the safe design region for Class-B/J BA and Class-F -1 CA. Following the investigation results, an identical input matching network (IMN) with tuned Z_{2S} terminations was designed for both CA and BA cells for an SLMBA operating from 1.8 to 2.6 GHz leaveraging high efficiency back-off performance from a Class-F- 1 CA. Measured results showed high drain efficiency (DE) of 53.2% to 64.7% at 8-dB back-off and 62.7% to 67.4% at peak power as well.