US 4,901,332 AGranted

Noncoherent-coherent A.C. coupled base band AGC receiver

AssigneeUnisys Corporation

InventorsBruce H. Williams, Christopher R. Keate, Jeffrey Mac Thornock

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Abstract

The present invention describes a phase shift key receiver or demodulator having an A.C. couple base band automatic gain control. A pair of detectors for the automatic gain control are A.C. coupled to the output of a pair of linear analog multipliers for the purpose of eliminating DC offset signals and for minimizing thermal noise at the input of the automatic gain control circuit. The outputs of the pair of detectors connected in the data detecting branch and the carrier tracking branch of the PLL are connected to a input of the summing circuit whose output is connected to the automatic gain control loop filter. The output of the filter supplies the scaling signal employed as the scaling input to the linear analog multipliers.

Claims5

Dependent claims

An A.C. coupled base band AGC receiver for receiving phase shifted key(PSK) data signals, said receiver being of the type having a phase lock loop (PLL), comprising:

said phase lock loop having a data detection branch and a carrier tracking branch coupled to a voltage controlled oscillator (VCO),
first and second linear analog multipliers connected respectively in one of said branches of said PLL,
third analog multiplier means coupled to said PLL branches,
first and second means for A.C. coupling said third analog multiplier means to said first and second linear analog multipliers,
first and second detector means coupled to the output of said first and second means for A.C. coupling,
summing means coupled to the output of said first and second detector means,
an automatic gain control loop filter coupled to the output of said summing means, and
the output of said automatic gain control loop filter being coupled as an input to said first and second linear analog multipliers to provide voltage control gain devices in each of said branches of said phase lock loop.

5 more elements

Dependencies are inferred from the claim text.