Patent ID: 7372925
Filing Date: 2008-05-13
Classification: H03G,H04L

Abstract:
1. A wireless receiver having a two-stage automatic gain control (AGC) comprising: a low-noise amplifier (LNA) capable of receiving a wireless signal from an antenna, and further having a controllable amplification; a first mixer connected to an output of said LNA coupled to receive a first local oscillator (LO) signal and output a first baseband signal; a second mixer connected to the output of said LNA, coupled to receive a second LO signal and output a second baseband signal; a first baseband filter (BBF) connected to the output of said first mixer; a second baseband filter (BBF) connected to the output of said second mixer; a radio frequency AGC (RFAGC) circuit receiving as inputs at least an output signal of said first BBF and an output signal of said second BBF, said RFACG having an output coupled in a first closed loop to control the amplification of said LNA; a first baseband amplifier (BBA) coupled to receive the output of said first BBF; a second baseband amplifier (BBA) coupled to receive the output of said second BBF; a baseband AGC (BBAGC) circuit receiving as inputs at least an output signal of said first BBA and an output of said second BBA, said BBAGC being coupled in a second closed loop to control the amplifications of at least said first BBA and said second BBA; wherein said first and second closed loops of said AGC circuits are active during at least part of the preamble period of an orthogonal frequency division multiplexing (OFDM) transmission, said closed loops being opened thereafter, and further comprising AGC signal storage devices to retain the inputs to said AGC circuits after said closed loops are opened.