UC San Diego
High Power, Linear CMOS Power Amplifier for WLAN Applications /
- Author(s): Afsahi, Ali
- et al.
The advancement of CMOS technology has enabled a high level of integration in modern, low cost, small form- factor and low power wireless devices. While power amplifiers (PAs) are key components in wireless transceivers, their realization and integration in standard CMOS technology has shown several challenges. The modern wireless standards such as WLAN and LTE, utilize higher order modulation schemes in order to increase the data rate and efficiently use the limited available spectrum and also provide a robust link in a fading environment. These modulations possess a very high peak-to -average ratio (PAR) and require a very linear power amplifier to preserve the integrity of the signal. In this dissertation several linearization and power combining techniques have been proposed to address the challenges of designing a high power and linear PA in CMOS for WLAN applications. To demonstrate these techniques in silicon, three chips have been designed and fabricated in 65nm standard CMOS. In the first chip, a fully integrated dual- band power amplifiers with on-chip baluns for 802.11n MIMO WLAN applications are implemented. With a 3.3v supply, the PAs produce a saturated output power of 28.3dBm and 26.7dBm with peak drain efficiency of 35.3% and 25.3% for the 2.4GHz and 5GHz bands, respectively. By utilizing multiple fully self-contained linearization algorithms, an EVM of -25dB is achieved at 22.4dBm for the 2.4GHz band and 20.5dBm for the 5GHz band while transmitting 54Mbs OFDM. In the next two designs, two monolithic power combining schemes for CMOS power amplifiers, distributed- LC and current-mode transformer-based, are compared. Fully integrated 2.4GHz power amplifiers (PAs) using these techniques were fabricated. From a 3.3 V supply, the distributed-LC combined PA produces a saturated power of 31.5dBm with peak PAE of 25%. The current-mode transformer based PA combiner produces 33.5dBm saturated power with 37.6% peak PAE. With gm-linearization and digital pre- distortion, these PAs transmit 25.5dBm and 26.4dBm with - 25dB EVM for a 54Mb/s OFDM signal respectively