Abstract
A dual-mode (CDMA/AMPS) power amplifier has been successfully implemented by using a monolithic SiGe/Si heterojunction bipolar transistor (HBT) foundry process for cellular handset (824-849 MHz) applications. The designed two-stage power amplifier satisfies both CDMA and AMPS requirements in output power, linearity, and efficiency. At V/sub cc/=3 V,the power amplifier shows an excellent linearity (first ACPR<-44.1 dBc and second ACPR<-57.1 dBc) up to 28 dBm of output power for CDMA applications. Under the same bias condition, the power amplifier also meets AMPS handset requirements in output power (up to 31 dBm) and linearity (with second and third harmonic to fundamental ratios lower than -37 dBc and -55 dBc, respectively). At the maximum output power level, the worst power-added efficiencies (PAEs) are measured to be 36% for CDMA and 49% for AMPS operations. The power amplifier also tolerates severe output mismatch (VSWR>12:1) up to V/sub cc/=4 V, with spurs measured to be <-22 dBc in CDMA outputs at two specific tuning angles, but with no spur in AMPS outputs at any tuning angle.
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