Design and simulation of a gaas HBT power amplifier for wideband CDMA wireless system

Power amplifiers are important circuit components used in wide-band code-division multiple-access (WCDMA) wireless communication systems. To accommodate more users and maximize the usage of the spectrum in WCDMA systems, power amplifiers (PAs) have to be highly linear and more efficient. In recent years, there has been a high demand for hetero-junction bipolar transistors (HBTs) for design of power amplifiers (PA) used in WCDMA wireless systems due to their better linearity and superior high-frequency performance [1]. The specifications of third-generation (3G) WCDMA PAs are listed in Table 1. Due to lack of availability of a compact model from the foundry, an artificial neural networks (ANNs) based nonlinear GaAs HBT model (given in [3]) has been used to carry out power amplifier design. A full PA simulation in ADS [4] using an ANN model [3] has been carried out and results shows that various third generation (3G) specifications such as gain, power-added efficiency (PAE), and adjacent channel power rejection have been achieved over nominal and extreme temperature conditions.