Abstract A phase modulator produces a controlled variable phase shift in the input signal being supplied to a signal conditioning circuit so as to maintain the total phase shift between the original input signal and the output signal of such circuit at a predetermined constant value, even though such circuit itself produces undesirable or spurious and unpredictable varying phase shifts in the signal being modified due to changing circuit conditions such as changes in temperature of components in the circuit, changes in current flow through such components or changes in voltage applied to such components. A phase comparator compares a portion of the output signal of the signal conditioning circuit with a portion of the input signal and supplies a control voltage to the phase modulator. This control voltage causes the phase modulator to vary the phase shift of the input signal in a direction resulting in such constant phase shift. The disclosed signal conditioning circuit is a horizontal deflection circuit for a television monitor. In the phase comparator, a selected portion of blanking pulses at the output of the deflection circuit and a selected portion of alternate cycles of a symmetrical square wave from a horizontal oscillator are employed to set and reset a gating multivibrator to produce an unsymmetrical square wave which gates an integrator. The output of the integrator is a control voltage which varies with any variations in the time interval between such selected portions of the blanking pulse and input signal. The circuit shown may also include a synchronizing circuit for synchronizing the horizontal oscillator with synchronizing pulses derived from a television signal.
A phase control system which compensates for a signal conditioning circuit causing a variable phase shift between an input signal for said circuit and output signal from said circuit in which the improvement comprises: phase modulator means for producing a controlled phase shift in selected portions only of said input signal and delivering the phase shifted portions of the phase modulated input signal to said circuit so that the phase shifted portions are employed to cause said circuit to produce said output signal, said output signal being derived from said input signal; and phase comparator means, including gate means for selecting nonphase shifted portions of the phase modulated input signal, for comparing selected portions of said output signal with said nonphase shifted portions of said phase modulated input signal and producing a control signal which is a function of the total phase shift of said output signal with respect to said input signal of said phase modulator; said phase modulator means including means responsive to said control signal for varying said controlled phase shift to maintain said total phase shift substantially constant.
Claim 2
Dependent Claim
182 words
A phase control system which compensates for a signal conditioning circuit causing a variable phase shift between an input signal for said circuit and output signal from said circuit in which the improvement comprises: phase modulator means for producing a controlled phase shift in selected portions only of said input signal and delivering the phase shifted portions of the phase modulated input signal to said circuit so that the phase shifted portions are employed to cause said circuit to produce said output signal, said output signal being derived from said input signal; and phase comparator means, including gate means for selecting nonphase shifted portions of the phase modulated input signal, for comparing selected portions of said output signal with said nonphase shifted portions of said phase modulated input signal and producing a control signal which is a function of the total phase shift of said output signal with respect to said input signal of said phase modulator; said phase modulator means including means responsive to said control signal for varying said controlled phase shift to maintain said total phase shift substantially constant.
Claim 3
Dependent Claim
104 words
The phase control system of claim 1 in which: said phase modulator includes means for producing successive voltage ramps each starting at a first voltage level and at a time coincident with a selected portion of said input signal and terminating when said ramp reaches a second voltage level and producing a controlled phaSe shift of a portion of said input signal of said phase modulator equal to the time interval between the start and termination of such ramps; and includes means responsive to said control signal to vary the slope of said ramps to vary the time value of said controlled phase shift.
Claim 4
Dependent Claim
134 words
The phase control circuit of claim 1 in which: said phase comparator includes gate means for producing an integrator gating voltage having repetitive cycles of constant time duration and having one voltage level for a time interval which is less than said constant time duration and which is a function of said total phase shift and having a different voltage level for a time interval which is the difference between said constant time duration and said time interval; and integrator means gated by said integrator gating voltages for integrating a voltage of one polarity during one of said time intervals and for integrating a voltage of a different polarity during the other of said time intervals to produce as said control signal a control voltage which is a function of said total phase shift.
Claim 5
Dependent Claim
74 words
The phase control system of claim 3 in which: said gate means for producing said integrator gating voltage is a bistable multivibrator which is reset from a second stable state to a first stable state in response to each of said selected portion of said output signal and is caused to change back to said second stable state in response to the next successive selected portion of said input signal of said phase modulator.
Claim 6
Dependent Claim
51 words
The phase controlled system of claim 4 in which: said signal conditioning circuit is a horizontal deflection circuit of a television monitor and said phase comparator includes means for selecting portions of each of a series of blanking pulses forming an output signal of said deflection circuit to reset said multivibrator.
Claim 7
Dependent Claim
62 words
The phase control system of claim 1 in which: said signal conditioning circuit is a horizontal deflection circuit of a television monitor and said phase comparator means includes means for selecting a portion of each of a series of unblanking pulses forming an output signal of said circuit for comparison with said selected portions of said input signal of said phase modulator.
Claim 8
Dependent Claim
42 words
The phase control system of claim 6 in which: said system also includes synchronizing means responsive to the selected portions of said unblanking pulses and to synchronizing pulses from video circuits of said monitor for synchronizing said system with said synchronizing pulses.