Automatic Gain Control And Power Detector Design, The Rf Receiver

As a basic module of communication system,the performance of RF receivers directly affects consumers.Thus RF receivers in various communication systems have been given widespread concern and in-depth study.This work studies automatic gain control(AGC) in RF receivers.The creative contribution was been made in the theory of AGC.The traditional analog AGC was discussed systematically.The digital AGC was studied in-depth.This work also presents the design of a power detector for RF front-end because the power detection is essential in an AGC.Firstly,signal to noise distortion ratio(SNDR) considering noise and non-linearity simultaneously to weigh the signal quality was proposed.The relationship between cascaded SNDR and SNDR of each module is derived. This dissertation proposed that optimizing SNDR is the principle of gain control. This work derived that optimizing the entire SNDR can be achieved by optimizing SNDR of every module.In addition,steps are given for the design of AGC in a multi-module system.Secondly,three programmable gain control(PGC) algorithms are proposed.As an application example,the PGC algorithm for the DVB-T tuner is proposed.The algorithm ensures the maximum SNDR,the constant settling time and the low circuit requirement.Thirdly,this work presents a new power detector circuit for RF front-end. The circuit with a logarithmic relationship between input and output employs a new wide-band limiting amplifier and a transconductance amplifier.It was fabricated in the CMOS technology and the simulated operating frequency reaches 1GHz.Finally,measured results are presented.The PGC algorithm for the DVB-T tuner is verified.The performance of the power detector integrated into the tuner is also measured.Measured results shows design meets demands of the system.