Signal synthesizer employing an autotransformer having a tapped coil

Claim 2

A signal synthesizer for producing a stepped voltage having a fundamental sinusoidal frequency component and low harmonic content comprising: an impedance element having at least one group of spaced taps thereon, first switching means connected to said impedance element for coupling a reference voltage of selected polarity and constant value across said group of spaced taps, said taps being positioned on said impedance element to provide a voltage at each tap which is a sinusoidal function of said position with respect to a tap maintained at a fixed potential, and second switching means connected to said impedance element and having an output terminal, said second switching means coupling sequentially the taps on said impedance element to said output terminal between each reversal by said first switching means of the polarity of said reference voltage to provide between each of said polarity reversals a stepped voltage at said output terminal corresponding to a half-cycle of said fundamental sinusoidal component.

Claim 3

A signal synthesizer as defined by claim 1 wherein said impedance element has two groups of spaced taps, and said second switching means has first and second output terminals and is coupled to said first and second group of taps, stepped voltages in phase quadrature with each other being coupled to said first and second output terminals.

Claim 4

A signal synthesizer as defined by claim 1 wherein said impedance element is an autotransformer having a tapped coil.

Claim 5

A signal synthesizer as defined by claim 2 wherein there are eight taps in each of said groups.

Claim 6

Apparatus including an electromagnetic transducer having first and second reference windings, a signal synthesizer for providing stepped voltages to said first and second reference windings, said voltages having fundamental sinusoidal frequency components in phase quadrature with respect to each other and low harmonic content, comprising: an impedance element having first and second ends and having at least first and second groups of spaced taps thereon, first switching means connected to said impedance element for alternately connecting reference voltages of opposite polarity and constant value across said first and second groups of spaced taps, said taps being located on said impedance element to provide a voltage at each tap within a group which is a sinusoidal function of said location with respect to a tap maintained at a fixed potential, second switching means connected to said impedance element and having first and second output terminals, said second switching means coupling sequentiallY and selectively the taps in each of said first and second groups respectively to said first and second output terminals to provide stepped output voltages thereof, said voltages having fundamental sinusoidal components in phase quadrature with each other, and means coupling the first and second output terminals of said second switching means to the first and second input windings of said transducer respectively.

Claim 7

Apparatus including an electromagnetic transducer having first and second reference windings, a signal synthesizer for providing stepped voltages to said first and second reference windings, said voltages having fundamental sinusoidal frequency components in phase quadrature with respect to each other and low harmonic content, comprising: an impedance element having first and second ends and having at least first and second groups of spaced taps thereon, first switching means connected to said impedance element for alternately connecting reference voltages of opposite polarity and constant value across said first and second groups of spaced taps, said taps being located on said impedance element to provide a voltage at each tap within a group which is a sinusoidal function of said location with respect to a tap maintained at a fixed potential, second switching means connected to said impedance element and having first and second output terminals, said second switching means coupling sequentiallY and selectively the taps in each of said first and second groups respectively to said first and second output terminals to provide stepped output voltages thereof, said voltages having fundamental sinusoidal components in phase quadrature with each other, and means coupling the first and second output terminals of said second switching means to the first and second input windings of said transducer respectively.

Claim 8

Apparatus as defined by claim 5 wherein said impedance element is an autotransformer having a tapped coil, said first and second groups of taps being located between said first and second ends of said coil respectively and an intermediate reference point, said first switching means coupling a reference voltage to one polarity between the first end of said coil and said reference point and a voltage of opposite polarity between the second end of said coil and said reference point.

Claim 9

Apparatus as defined by claim 5 wherein said second switching means includes first and second groups of tap switches each having a first terminal, a second terminal and a control terminal, the first terminal of each of the switches in said first and second groups being coupled to a corresponding tap in said first and second groups of spaced taps respectively; and a switching circuit having a first input terminal coupled to the second terminals of said first group of tap switches and a second input terminal coupled to the second terminals of said second group of tap switches.

Claim 10

Apparatus as defined by claim 7 which further comprises: a clock generator for generating pulses, a counter having an input coupled to said clock generator and a first output coupled to said first switching means, said counter resetting after receiving a predetermined number of pulses from said clock generator, and a decoder having an input coupled to a second output of said counter and a plurality of output terminals, each of said output terminals being coupled to the control terminals of a corresponding tap switch in said first and second groups, said decoder energizing sequentially said tap switches in accordance with pulses received by said counter means from said clock generator.

Claim 11

Apparatus as defined by claim 8 wherein said first switching means further comprises an input terminal and first, second, third and fourth output terminals, a first multivibrator having an input coupled to the input terminal of said first switching means and a pair of outputs coupled to said first and second output terminals of said first switching means, said first multivibrator receiving a pulse each time said counter resets and reversing the states of the voltages at its first and second outputs, a second multivibrator having an input coupled to an output of said first multivibrator and a pair of outputs, said second multivibrator reversing the states of the voltages at its outputs for every second pulse received by said first multivibrator, and first and second switching elements each having an input coupled to a corresponding output of said second multivibrator and an output coupled to said third and fourth output terminals of said first switching means and to a corresponding end of said impedance element, said first and second switching elements being driven alternately into conduction each time the output of said second multivibrator changes states.

Claim 12

Apparatus as defined by claim 7 wherein said switching circuit comprises means coupling the voltages at the first and second input terminals of said switching circuit during the first and third quadrants of each cycle of said fundamental sinusoidal frequency component to the first and second output terminals respectively of said second switching means, and means coupling the voltages at the first input terminal of said switching circuit during the second and fourth quadrants of each cycle of said fundamental sinusoidal frequency component to the second output terminal of said second switching means, and means coupling The negative of the voltage at the second input terminal of said second switching circuit during the second and fourth quadrants of each cycle of said fundamental sinusoidal frequency component to the first output terminal of said second switching means.

Claim 13

Apparatus as defined by claim 7 wherein there are eight taps in each of said groups.