Automatic gain control for an electromechanical transducer

Claim 2

An electromechanical transducer apparatus which produces undesired amplitude variations due to changes in the strength of the horizontal component of the earth''s magnetic field having transmitter means and receiver means, an improvement comprising automatic signal conTrol means connected between said transmitter means and said receiver means comprising amplitude detection means connected to said transmitter means for detecting undesired amplitude variations in the output signals of said transmitter means and providing an output control signal at an output terminal which is linearly proportional to said undesired amplitude variations, and variable impedance means connected between said transmitter means and said receiver means, said variable impedance means being coupled to said automatic signal control output terminal and having dynamic impedance characteristics that change in a manner inversely proportional to said output control signal thereby eliminating the effects of said undesired amplitude variations.

Claim 3

An electromechanical transducer apparatus which produces undesired amplitude variations due to changes in the strength of the horizontal component of the earth''s magnetic field having amplifying means connected between transmitter means and receiver means, an improvement comprising: automatic gain control means connected between said transmitter means and said amplifying means comprising amplitude detection means connected to said transmitter means for detecting undesired amplitude variations in the output signals of said transmitter means and providing an output control signal linearly proportional to said undesired amplitude variations, and variable impedance means connected between said transmitter means and said amplifying means, said variable impedance means being coupled to said automatic signal control output terminal and having dynamic impedance characteristics for changing the gain of said amplifying means in a manner inversely proportional to said output control signal thereby eliminating the effects of said undesired amplitude variations.

Claim 4

An electromechanical transducer apparatus which produces undesired amplitude variations due to changes in the strength of the horizontal component of the earth''s magnetic field having amplifying means connected between transmitter means and receiver means, an improvement comprising: automatic gain control means connected between said transmitter means and said amplifying means comprising amplitude detection means connected to said transmitter means for detecting undesired amplitude variations in the output signals of said transmitter means and providing an output control signal linearly proportional to said undesired amplitude variations, and variable impedance means connected between said transmitter means and said amplifying means, said variable impedance means being coupled to said automatic signal control output terminal and having dynamic impedance characteristics for changing the gain of said amplifying means in a manner inversely proportional to said output control signal thereby eliminating the effects of said undesired amplitude variations.

Claim 5

In apparatus of the character recited in claim 2 in which said amplitude detection means includes combining means connected to said transmitter means for combining a plurality of transmitter output signals and generating a signal with amplitude variations linearly related to the amplitude of said undesired amplitude variations, filter means connected between said combining means and peak detector means providing a filtered output signal containing frequencies within a specified bandwidth, said peak detector means detecting the amplitude of said filtered output signal producing a control signal linearly proportional to said undesired amplitude variation, and current source means connected between said peak detector means and said variable impedance means for converting said control signal into a varying current signal.

Claim 6

In apparatus of the character recited in claim 2 in which amplifying means comprises identical first and second parallel paths having substantially identical components in each path.

Claim 7

In apparatus of the character recited in claim 2 in which variable impedance means comprises identical first and second parallel paths having matching dynamic impedance characteristics.

Claim 8

In apparatus of the character recited in claim 5 in which said first and second parallel paths include semiconductor devices.

Claim 9

In apparatus of the character recited in claim 6 in which said semiconductor devices includes matched pairs of diodes.

Claim 10

In apparatus of the character recited in claim 3 in which said current source means includes a transistorized current generator.

Claim 11

In electromechanical transducer apparatus of the character recited in claim 3 in which said transmitter means includes a flux valve having a plurality of output signals that have said undesired amplitude variations resulting from variations in the horizontal component of the earth''s magnetic field, said combining means includes a vectorial combiner producing an output of constant amplitude regardless of the orientation of said flux valve in the earth''s magnetic field and producing an output of variable amplitude linearly proportional to said variations in the Horizontal component of the earth''s magnetic field, said receiver means includes a torque receiver adapted to position a heading card for indicating direction.