Demodulator for angularly related signals

Claim 2

In a system having primary winding means coupled to an energizing signal and a plurality of secondary windings having signals impressed thereon dependent upon the angular position of said primary winding means relative to said secondary windings and undesirably dependent upon a signal phase shift occurring during signal transfer between said primary winding means and said secondary windings, a converter circuit for determining said relative angular position independent of said signal phase shift, comprising: angular channel means coupled to said secondary windings for combining said impressed signals to form a combined signal phase shifted with respect to said energizing signal in direct proportion to said relative angular position and said signal phase shift; reference channel means coupled to at least said secondary windings and responsive at least partly to said impressed signals for generating a corrected reference signal synchronous with said energizing signal and phase offset therefrom by said signal phase shift; and means for comparing said combined signal with said corrected reference signal to generate an output signal dependent solely on said relative angular position.

Claim 3

The converter circuit of claim 1 wherein said reference channel means includes logic means coupled to said secondary windings for determining a zero crossing of a function of said impressed signals, and shifting means responsive to said detected zero crossing for shifting the phase of the corrected reference signal so that it corresponds with the time of occurrence of said detected zero crossing.

Claim 4

The converter circuit of claim 2 wherein said shifting means includes storage means coupled to said primary winding means for storing said energizing signal and triggering means responsive to said detected zero crossing for gating the stored energizing signal to said comparing means, whereby the gated stored energizing signal becomes the said corrected reference signal.

Claim 5

The converter circuit of claim 2 wherein said angular channel means includes first combining means coupled to said secondary windings for developing a first combined signal and second combining means coupled to said secondary windings for developing a second combined signal different from said first combined signal, and said logic means includes means for selecting the zero crossing of solely said first combined signal or second combined signal.

Claim 6

The converter circuit of claim 4 wherein said zero crossing selecting means includes amplitude responsive means for selecting the combined signal having a larger amplitude.

Claim 7

The converter circuit of claim 1 wherein said reference channel means includes storage means for storing said energizing signal and time shift means responsive to said impressed signals for time shifting said stored energizing signal until its phase corresponds with the amount of signal phase shift.

Claim 8

The converter circuit of claim 6 wherein said storing means comprises a flip-flop having a signal input coupled to said energizing signal and a triggering input for gating out a signal from the flip-flop, and means connecting said triggering input to said time shift means.

Claim 9

In a system having primary winding means coupled to an energizing signal and a plurality of secondary windings having signals impressed thereon dependent upon the angular position of said primary winding means relative to said secondary windings, a converter circuit for determining said relative angular position, comprising: first combining means coupled to said secondary windings for developing a first combined signal; second combining means coupled to said secondary windings for developing a second combined signal different than said first combined signal; 90* phase shift means including differential amplifying for producing at output means a signal proportional to the difference between signals coupled to a pair of input means, means coupling said first combining means to the input means of said differential amplifying means, and capacitor feedback means connected between said output means and said input means to cause said first combined signal to be integrated; and means for combining said integrated signal with said second combined signal to form an angular representing signal phase shifted with respect to said energizing signal in direct proportion to said relative angular position.

Claim 10

In a system having primary winding means coupled to an energizing signal and a plurality of secondary windings having signals impressed thereon dependent upon the angular position of said primary winding means relative to said secondary windings, a converter circuit for determining said relative angular position, comprising: first combining means coupled to said secondary windings for developing a first combined signal; second combining means coupled to said secondary windings for developing a second combined signal different than said first combined signal; 90* phase shift means including differential amplifying for producing at output means a signal proportional to the difference between signals coupled to a pair of input means, means coupling said first combining means to the input means of said differential amplifying means, and capacitor feedback means connected between said output means and said input means to cause said first combined signal to be integrated; and means for combining said integrated signal with said second combined signal to form an angular representing signal phase shifted with respect to said energizing signal in direct proportion to said relative angular position.

Claim 11

The converter circuit of claim 8 wherein said 90* phase shift means includes AGC means coupled to said differential amplifying means for maintaining a constant signal magnitude at said output means independent of changes in frequency of said energizing signal.

Claim 12

The converter circuit of claim 8 wherein said 90* phase shift means includes a drift stabilizing amplifier having an input coupled to said output means for sampling the steady state drift of said differential amplifying means and an output connected to said input means for reducing the steady state drift of the differential amplifying means.

Claim 13

The converter circuit of claim 8 in a synchro system having three secondary windings having three signals impressed thereon, wherein one of said combining means includes adder means for summing a pair of said three signals to generate a summation combined signal, and the other of said combining means includes subtractor means for subtracting a pair of said three signals to generate a subtraction combined signal.

Claim 14

The converter circuit of claim 11 wherein said other combining means includes subtractor differential amplifying means having a pair of Subtractor input means, and said subtraction means includes a pair of resistive means coupled between a pair of said secondary windings and said pair of subtractor input means, respectively.