George B. Norris

High efficiency CDMA RF power amplifier using dynamic envelope tracking technique

This work describes a 2-W peak-envelope linear power amplifier based upon the envelope tracking (ET) technique with application to CDMA cellular radio handsets. Both drain voltages of a two stage monolithic GaAs IC are varied with respect to the long term rms value of the modulated signal using a high efficiency Class-S modulator. The modulator is implemented as a single chip silicon IC to supply currents in excess of 1 A. The RF amplifier IC utilizes two AlGaAs/InGaAs heterostructure insulated-gate FET structures which allows single voltage supply operation with state-of-the-art linearity and efficiency performance. When driven by a CDMA O-QPSK signal, the ET amplifier exhibits desired spectral linearity while achieving a remarkable 5/spl times/ improvement in overall efficiency, compared to fixed supply bias, when measured in a reverse link urban based mobile transmitter power profile.

Application of Digital Adaptive Pre-distortion to Mobile Wireless Devices

Low power adaptive pre-distortion (APD) techniques are applied to nonlinear RF power amplifiers for mobile devices. An APD system is demonstrated which reduces spectral regrowth products by 10-20 dB and increases modulation accuracy by 2-6X. The use of APD allows a reduction in 3 G PA supply current by 2X and provides immunity to load mismatches as high as 8:1.

Optimized Closed Loop Polar GSM/GPRS/EDGE Transmitter

An amplitude-only closed-loop EDGE transmitter using a PA with low AM-PM distortion is presented with a comparable size to existing open loop EDGE PA modules and added closed loop current <20mA. The complete PA/controller consumes 700mA at 28dBm and <80mA at 6dBm. RMS EVM is <2.1%, ACPR margins are >5dB, and RX band noise is <-81dBm/100KHz at 20MHz offset. Reflected power amplitude feedback allows the transmitter to meet ORFS/EVM specifications under antenna VSWR as high as 6:1

RF power amplifier modeling for three-port applications using polynomials with IIR bases functions

This paper presents a scheme of modeling radio frequency (RF) power amplifier (PAs) for 3-port applications by including modeling of bias port of PA along with its input and output ports. This scheme uses polynomials with infinite impulse response (IIR) bases functions for modeling non-linear behavior of PA as well as its short and long term memory effects. Power amplifiers designed for third generation (WCDMA) wireless system are investigated for the validation of modeling scheme. Excellent results are obtained, where the error between model prediction and measurements is better than 43 dBc for a wide range of bias voltages, with the amplifier being driven with a WCDMA signal at several power levels.