Architecture and design of a reconfigurable RF sampling receiver for multistandard applications

The fast development of wireless communication systems requires more flexible and cost effective radio architectures. A long term goal is the software defined radio, where communication standards are chosen by reconfiguration of hardware. Direct analog to digital conversion of the radio frequency (RF) signal is still unrealistic at present time, due to the high requirements imposed on the analog to digital converter. This motivates the need for a highly flexible RF analog front-end that can be fully integrated in low cost digital deep-submicron CMOS processes. Different techniques for shifting the RF and analog circuit design complexity to digitally intensive domain were developed recently. These techniques are based on direct RF sampling and discrete-time analog signal processing and allow for a great flexibility and reduction of cost and power consumption in a reconfigurable design environment. These concepts have been used in this thesis to develop a reconfigurable discrete-time radio receiver front-end. The circuit, which consists mainly of a transconductance low noise amplifier and two discrete-time analog signal processing stages, performs RF sampling, anti-alias filtering, frequency downconversion, decimation and lowpass filtering. To validate the flexibility and reconfigurability of the receiver, GSM and 802.11g communication standards have been addressed and adopted during system level study. The frequency plan and filtering scheme decided for each standard were made different to fully analyze and validate the flexibility of the architecture. The circuit has been designed in 90nm CMOS technology and first measurement results demonstrated the functionality of the receiver. Additionally, a fully passive 2 order discrete-time sinc type anti-alias filter has been described and included in the proposed receiver. Based on capacitive ratios for coefficient weighting, this filter is intended to considerably improve the alias filter rejection, which is one of the major problems reported in present discrete-time receivers. By changing the input sampling rate, the anti-alias filter can be tuned to different RF frequency bands and is hence suitable for true multi-standard operations.