Robert Earl Rodgers

US Patent:

46098780, Sep 2, 1986

Filed:

Jul 31, 1985

Appl. No.:

6/761656

Inventors:

Robert L. Rodgers - Dallas TX

Assignee:

Circuit Research Labs, Inc. - Tempe AZ

International Classification:

H03G 902

US Classification:

330136

Abstract:

A noise reduction system including a signal path (34) between an input terminal (12) and an output terminal (36), a voltage control amplifier (38) and a control path (40) between the input terminal and the voltage control amplifier is disclosed. A nonlinear element such as a voltage squarer (32) is in the controlled path. In one arrangement, the control path also includes a signal level detector (22), a one-pole high pass filter (16) and a direct current level shifter (26). A precision diode (30) is interposed in the control path between the direct current level shifter and the signal squarer. One form of the noise reduction system includes a voltage-controlled low pass filter (20) interposed in the signal path between the input terminal and the voltage-controlled amplifier. A weighing control path (46) provides the control signal for the voltage-controlled low pass filter. A two-pole high pass filter (18) followed by a level sensor (48) is interposed in the weighting control path.

US Patent:

43981585, Aug 9, 1983

Filed:

Nov 24, 1980

Appl. No.:

6/209695

Inventors:

Robert L. Rodgers - Arlington TX

Assignee:

Micmix Audio Products, Inc. - Dallas TX

International Classification:

H03G 700

US Classification:

330136

Abstract:

A dynamic range expander which substantially limits the amount of positive expansion without affecting the amount of negative expansion is disclosed. In one arrangement, gain reduction in the amplitude of the output signal is increased when the amplitude of the input signal decreases toward or becomes less than the noise level present in the input signal. The dynamic range expander includes a detector (24) for sensing the amplitude of the input signal and providing a variable DC signal related to the amplitude of the input signal, a control signal generator (30) and an amplifier (34) for amplifying the input signal by a gain variable responsively to the output of the control signal generator. The control signal generator includes a time averager (50) and a summer (40) for providing a second variable DC signal related to the sum of the detector output and the time averaged detector output. The control signal generator further includes a precision clamp (56) for clamping the control signal, thereby limiting the amount of positive expansion of the input signal.