This paper presents a 1920-1980MHz LTE/WCDMA GaAs HBT/pHEMT-based 3x3mm 2 power amplifier module (PAM) with integrated directional coupler targeted for mobile handset applications. The PA operates in two power modes with a dual-path structure. Each path is optimized individually for each power mode, achieving low DC quiescent current and significant current saving compared to single-mode PAs under power backoff. Bias current and load impedance are specifically optimized for linear operation under high peak-to-average ratio LTE modulation. The PAM achieves a low quiescent current of 8mA. Under LTE modulation, the PAM exhibits 38/24% PAE at 27.5/16dBm Pout at UTRA ACLR1<-39dBc. Under WCDMA modulation, the PAM attains 42/26% PAE at 28.5/17dBm Pout at ACLR1<-40dBc. Further current saving is demonstrated with the use of variable power supply. The integrated 20dB coupler achieves ± ± ± ±0.06dB coupling variation under VSWR 2.5:1 mismatch, corresponding to a directivity of 36dB.
This paper presents a WCDMA power amplifier (PA) module which integrates a GaAs HBT MMIC PA and a Si BiCMOS DC power management IC in a compact 3x5mm 2 package. The all-in-one approach is suitable for handset applications. A closed-loop controlled DC-DC buck converter allows the power management IC to adaptively optimize the PA collector voltage as a function of output power and thereby reduce current consumption under backoff operation. In addition, the IC contains a low dropout voltage regulator (LDO) which supplies an internally regulated voltage for the PA mirror bias with an enable function compatible with future baseband chipset control requirement. The PAM achieves excellent current reduction over a wide range of output power (Pout) up to 27.5dBm, while maintaining ACLR1 below -40dBc. At 16dBm and 24dBm Pout, the current consumptions are reduced from 162mA and 370mA, to 75mA and 257mA, respectively, compared to the PA with constant collector bias.Index Terms -wideband code-division multiple access (WCDMA), efficiency enhancement, heterojunction bipolar transistor (HBT), linear amplifiers, power amplifiers, DC-DC converter.
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