CMOS power detector and power amplifier design for WLAN 802.11ax

• Main Author: Li, Chenyang
• Other Authors: Boon Chirn Chye
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/147852
• Institution: Nanyang Technological University

With the trend of increasing data throughput, modern wireless communication standards prefer to utilize high spectral-efficiency modulations, such as 256-Quadrature amplitude modulation (QAM) and 1024-QAM modulations, which leads to large peak-to-average power ratio (PAPR). This requires radio frequency (RF) power amplifiers (PAs) with high linearity and high efficiency performances even when operating in the power back-off (PBO) region. Besides, power control is essential for power amplifier to maintain reliable communications and extend battery life in mobile devices. Power detector (PD) is usually utilized for this purpose in the transmitter systems. With large PAPR, wide dynamic range (DR) is required for PD to work in modern systems. Therefore, the focus of this thesis is to design high linear PAs with reasonable efficiency integrated with wide DR PDs working in multi-band supported modern communication systems. Firstly, a novel PD with wide DR and area efficiency is proposed for wireless local area network (WLAN). The proposed diode PD solves low dynamic range problem by using both the positive and negative cycle of the input signals. Then, a variation of the proposed diode PD is introduced by replacing the diode by self-biased metal–oxide–semiconductor field-effect transistors (MOSFETs). The difference between the diode and MOSFET PD is also analyzed. Finally, a PD with frequency detection circuits to compensate the effect of input frequency variations by changing the load resistances is presented to support multi-band in modern communication systems. The PD employs self-biased P-type and N-type MOSFETs as switches and utilizes a balanced structure to increase the DR of the PD. Secondly, a linear PA with compensated non-linear trans-conductance integrated the proposed PD is introduced. The adaptive body biasing technique is achieved through envelop detectors to obtain the envelope information of the input signal. Based on this information, the body bias is changed accordingly to extend the duty cycle of MOSFET working in saturation region. This way the MOSFET works less in non-linear regions such as cut-off region or triode region in one duty cycle. Therefore, the power amplifier improves the linearity without degrading other performances of PA. The output power of the PA can be monitored by the proposed PD.