Power Amplifier Circuits in CMOS Technologies
The wireless market has experienced a remarkable development and growth since the introduction of the first mobile phone systems, with a steady increase in the number of subscribers, new application areas, and higher data rates. As mobile phones and wireless connectivity have become consumer mass markets, a prime goal of the IC manufacturers is to provide low-cost solutions.The power amplifier (PA) is a key building block in all RF transmitters. To lower the costs and allow full integration of a complete radio System-on-Chip (SoC), it is desirable to integrate the entire transceiver and the PA in a single CMOS chip. While digital circuits benefit from the technology scaling, it is becoming significantly harder to meet the stringent requirements on linearity, output power, and power efficiency of PAs at lower supply voltages. This has recently triggered extensive studies to investigate the impact of different circuit techniques, design methodologies, and design trade-offs on functionality of PAs in nanometer CMOS technologies.This thesis addresses the potential of integrating linear and highly efficient PAs and PA architectures in nanometer CMOS technologies at GHz frequencies. In total four PAs have been designed, two linear PAs and two switched PAs. Two PAs have been designed in a 65nm CMOS technology, targeting the 802.11n WLAN standard operating in the 2.4-2.5GHz frequency band with stringent requirements on linearity. The first linear PA is a two-stage amplifier with LC-based input and interstage matching networks, and the second linear PA is a two-stage PA with transformer-based input and interstage matching networks. Both designs were evaluated for a 72.2Mbit/s, 64-QAM 802.11n OFDM signal with a PAPR of 9.1dB. Both PAs fulfilled the toughest EVM requirement of the standard at average output power levels of 9.4dBm and 11.6dBm, respectively. Matching techniques in both PAs are discussed as well.Two Class-E PAs have been designed in 130nm CMOS and operated at low ‘digital’ supply voltages. The first PA is intended for DECT, while the second is intended for Bluetooth. At 1.5V supply voltage and 1.85GHz, the DECT PA delivered +26.4dBm of output power with a drain efficiency (DE) and poweradded efficiency (PAE) of 41% and 30%, respectively. The Bluetooth PA had an output power of +22.7dBm at 1.0V with a DE and PAE of 48% and 36%, respectively, at 2.45GHz. The Class-E amplifier stage is also suitable for employment in different linearization techniques like Polar Modulation and Outphasing, where a highly efficient Class-E PA is crucial for a successful implementation.
Source Type:Master's Thesis
Date of Publication:01/01/2009