Amplifiers – With control of power supply or bias voltage – With control of input electrode or gain control electrode bias
Patent
1995-04-13
1997-04-01
Mottola, Steven
Amplifiers
With control of power supply or bias voltage
With control of input electrode or gain control electrode bias
4552391, 330141, H03G 320
Patent
active
056170602
ABSTRACT:
An automatic gain control (AGC) and D.C. offset correction method and apparatus for controlling signal power of a received RF signal within a dual mode quadrature receiver is disclosed herein. In a preferred implementation the automatic gain control apparatus may be adjusted to provide a desired control response to various fading characteristics of a received FM, FSK, GMSK, QPSK, or BPSK signal. The AGC apparatus includes an adjustable gain amplifier having an input port for receiving an input signal, a control port for receiving a gain control signal, and an output port for providing an output signal. A quadrature downconverter coupled to the output port serves to translate the frequency of the output signal to a baseband frequency, thereby producing baseband signals. In a preferred implementation the downconverter is operative to map the carrier frequency of the output signal to a baseband frequency offset by a predetermined margin from D.C. Two high gain active lowpass filters provide out-of-band signal rejection for the baseband signals. A D.C. feedthrough suppression loop, disposed to receive said baseband signal, suppresses D.C. offsets produced by the downconverter and lowpass filters, hence providing a compensated baseband signal. The AGC apparatus is further disposed to generate a received power signal based on the power of the output signal. A saturating integrator compares the received power signal to a reference signal and produces the gain control signal by integrating or by refraining from integration based on values of the reference, received power signal, and gain control signals, thereby extending the usable dynamic range of the receiver for FM mode.
REFERENCES:
patent: 4653117 (1987-03-01), Heck
patent: 4944025 (1990-07-01), Gehring et al.
patent: 5107225 (1992-04-01), Wheatley, III et al.
patent: 5452473 (1995-09-01), Weiland et al.
Black Peter J.
Peterzell Paul E.
Wilson Nathaniel B.
Martin Roger W.
Miller Russell B.
Mottola Steven
Qualcomm Incorporated
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