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Automatic gain control in direct sequence spread spectrum communication system

  • US 6,035,008 A
  • Filed: 10/06/1997
  • Issued: 03/07/2000
  • Est. Priority Date: 10/05/1996
  • Status: Expired due to Term
First Claim
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1. An automatic gain control device of a receiver in a direct sequence spread spectrum communication system, comprising:

  • a reception signal gain controller for causing a radio frequency amplifier to function as an attenuator during a packet reception interval when a received signal has a signal level higher than a predetermined normal operating level, said radio frequency amplifier attenuating said signal level of said received signal to said normal operating level and for varying an output level of a local oscillator signal of an intermediate frequency converter upon receiving said received signal having a signal level equal to or lower than said normal operating level, so as to match an output level of an intermediate frequency signal generated by an intermediate frequency stage with an input level of a base band stage;

    said reception signal gain controller comprising;

    a first reception power controller for cutting off a supply voltage being supplied to said radio frequency amplifier during a packet reception interval when said received signal has a level higher than said normal operating level, thereby causing said radio frequency amplifier to function as an attenuator;

    a second reception power controller for comparing said received signal with a fine adjusting reference voltage when said received signal has a level equal to or lower than said normal operating level and for generating an output voltage in response thereto; and

    a low-pass filter for varying a cut-off frequency thereof according to said output voltage of said second reception power controller, for controlling said output level of said local oscillator signal according to variations of said cut-off frequency.

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