Dual mode automatic gain control

Claim 2

A gain control system for controlling signal levels of a signal received by a receiver, said gain control system comprising: first down-conversion circuitry for converting the signal received by the receiver into a first down-converted signal of an intermediate frequency and of signal level magnitudes representative of signal level magnitudes of the signal received by the receiver; variable amplifier circuitry coupled to receive the first down-converted signal generated by the first down-conversion circuitry, said variable amplifier circuitry for generating an amplified signal of the intermediate frequency at an amplification level corresponding to a gain coefficient of the variable amplifier circuitry; second down-conversion circuitry coupled to receive the amplified signal for converting the amplified signal of the intermediate frequency generated by said variable amplifier circuitry into a baseband signal of signal level magnitudes representative of signal level magnitudes of the signal received by the receiver; first signal detection circuitry, coupled to receive the baseband signal generated by said second down-conversion circuitry, having means for converting the baseband signal upward in frequency to form an upconverted signal, and means, coupled to receive the upconverted signal, for determining values of the signal levels of the signal received by the receiver when said signal is comprised of a constant envelope signal and for generating a first gain control signal responsive to values of the signal levels determined thereat; second signal detection circuitry, coupled to receive the baseband signal generated by said second down-conversion circuitry, for determining values of the signal levels of said signal received by the receiver when the signal is comprised of a non-constant envelope signal, the second signal detection circuitry formed thereby having, as a portion thereof, a digital signal processor, operative during times in which the signal received by the receiver is comprised of the non-constant envelope signal and non-operative during times in which the signal received by the receiver is comprised of the constant envelope signal, and for generating a second gain control signal responsive to values of the signal levels determined thereat; and means for alternately applying either the first gain control signal or the second gain control signal to the variable amplifier circuitry thereby to adjust the gain coefficient of the variable amplifier circuitry.

Claim 3

The gain control system of claim 1 wherein said means for applying comprises means forming a switch for applying either the first gain control signal or the the second gain control signal to the variable amplifier circuitry.

Claim 4

The gain control system of claim 2 wherein said switch formed by the means for applying is actuated by a signal transmitted to the receiver.

Claim 5

The gain control system of claim 2 wherein said switch formed by the means for applying comprises a multiplexer.

Claim 6

The gain control system of claim 1 wherein said constant envelope signal comprises a frequency modulated signal.

Claim 7

The gain control system of claim 1 wherein said non-constant envelope signal comprises a composite modulated signal.

Claim 8

The gain control system of claim 1 wherein said second down-conversion circuitry for converting the amplified signal generated by the variable amplifier circuitry into the baseband signal comprises a zero intermediate frequency down conversion section.

Claim 9

The gain control system of claim 7 wherein said zero intermediate frequency down conversion section generates an analog output signal indicative of the signal received by the receiver.

Claim 10

The gain control system of claim 7 wherein said zero intermediate frequency down conversion section generates a signal corresponding to in phase and quadrature components of the signal received by the receiver.

Claim 11

The gain control system of claim 9 wherein said digital signal processor of the second signal detection circuitry is coupled to receive the in phase and quadrature components, respectively, generated by the zero intermediate frequency down conversion section.

Claim 12

The gain control system of claim 10 wherein the digital signal processor embodies an algorithm for calculating desired levels of the second gain control signal.

Claim 13

The gain control system of claim 10 wherein the digital signal processor further comprises a software equalizer.

Claim 14

The gain control system of claim 1 wherein said variable amplifier circuitry forms a portion of a zero intermediate filter.

Claim 15

The gain control system of claim 13 wherein either said first gain control signal or said second gain control signal is supplied to an input of the zero intermediate filter.

Claim 16

A dual mode transceiver operable to receive both a constant envelope modulated signal and a non-constant envelope modulated signal, said transceiver comprising: first down-conversion circuitry for converting the signal received by the receiver into a first down-converted signal of an intermediate frequency and of signal level magnitudes representative of signal level magnitudes of the signal received by the receiver; variable amplifier circuitry coupled to receive the first down-converted signal generated by the first down-conversion circuitry, said variable amplifier circuitry for generating an amplified signal of the intermediate frequency at an amplification level corresponding to a gain coefficient of the variable amplifier circuitry; second down-conversion circuitry, coupled to receive the amplified signal, for converting the amplified signal of the intermediate frequency generated by said variable amplifier circuitry into a baseband signal of signal level magnitudes representative of signal level magnitudes of the signal received by the receiver; first signal detection circuitry, coupled to receive the baseband signal generated by said second down-conversion circuitry, having means for converting the baseband signal upward in frequency to form an upconverted signal, and means, coupled to receive the upconverted signal, for determining values of the signal levels of the signal received by the receiver when said signal is comprised of the constant envelope signal and for generating a first gain control signal responsive to values of the signal levels determined thereat; second signal detection circuitry, coupled to receive the baseband signal generated by said second down-conversion circuitry, for determining values of the signal levels of said signal received by the receiver when the signal is comprised of the non-constant envelope signal, the second signal detection circuitry formed thereby having, as a portion thereof, a digital signal processor, operative during times in which the signal received by the receiver is comprised of the non-constant envelope signal and non-operative during times in which the signal received by the receiver is comprised of the constant envelope signal, and for generating a second gain control signal responsive to values of the signal levels determined by the second signal detection circuitry; and a switch coupled to receive both the first gain control signal and the second gain control signal, and operative to apply the first gain control signal to the variable amplifier circuitry when the signal received by the receiver is comprised of the constant envelope signal and, alternately, to apply the second gain control signal to the variable amplifier circuitry when the signal received by the receiver is comprised of the non-constant envelope signal.

Claim 17

A dual mode transceiver operable to receive both a constant envelope modulated signal and a non-constant envelope modulated signal, said transceiver comprising: first down-conversion circuitry for converting the signal received by the receiver into a first down-converted signal of an intermediate frequency and of signal level magnitudes representative of signal level magnitudes of the signal received by the receiver; variable amplifier circuitry coupled to receive the first down-converted signal generated by the first down-conversion circuitry, said variable amplifier circuitry for generating an amplified signal of the intermediate frequency at an amplification level corresponding to a gain coefficient of the variable amplifier circuitry; second down-conversion circuitry, coupled to receive the amplified signal, for converting the amplified signal of the intermediate frequency generated by said variable amplifier circuitry into a baseband signal of signal level magnitudes representative of signal level magnitudes of the signal received by the receiver; first signal detection circuitry, coupled to receive the baseband signal generated by said second down-conversion circuitry, having means for converting the baseband signal upward in frequency to form an upconverted signal, and means, coupled to receive the upconverted signal, for determining values of the signal levels of the signal received by the receiver when said signal is comprised of the constant envelope signal and for generating a first gain control signal responsive to values of the signal levels determined thereat; second signal detection circuitry, coupled to receive the baseband signal generated by said second down-conversion circuitry, for determining values of the signal levels of said signal received by the receiver when the signal is comprised of the non-constant envelope signal, the second signal detection circuitry formed thereby having, as a portion thereof, a digital signal processor, operative during times in which the signal received by the receiver is comprised of the non-constant envelope signal and non-operative during times in which the signal received by the receiver is comprised of the constant envelope signal, and for generating a second gain control signal responsive to values of the signal levels determined by the second signal detection circuitry; and a switch coupled to receive both the first gain control signal and the second gain control signal, and operative to apply the first gain control signal to the variable amplifier circuitry when the signal received by the receiver is comprised of the constant envelope signal and, alternately, to apply the second gain control signal to the variable amplifier circuitry when the signal received by the receiver is comprised of the non-constant envelope signal.

Claim 20

The method of claim 16 wherein said constant envelope signal comprises a frequency modulated signal.

Claim 21

The method of claim 16 wherein said non-constant envelope signal comprises a composite modulated signal.