Method of and apparatus for determining the difference in phase between two periodic electrical signals having essentially the same frequency

Claim 3

Apparatus for determining the displacement in phase as between two input periodic signals having essentially the same frequency which comprises: means converting each of said input signals into a corresponding rectangular voltage waveform, means producing from the intervals between homologous edges of said rectangular voltage waveforms a train of duration-modulated rectangular signal pulses corresponding respectively to the difference in phase at a 2 pi transition, an integrate-and-hold circuit in which the signal pulses in said pulse train are integrated over a predetermined period to form and hold a corresponding amplitude modulated voltage signal, a sample-and-hold circuit connected to the output of said integrate-and-hold circuit, means controlled in accordance with the duration of said rectangular signal pulses and operative only when the pulse duration exceeds a predetermined minimum corresponding to a minimum value of the phase displacement between said input periodic signals for effecting transfer to and storage of said amplitude modulated voltage signal from the output of said integrate-and-hold circuit in said sample-and-hold circuit, a transient detector circuit connected to said sample-and-hold circuit for effecting periodic comparison therein between old and new values of said amplitude modulated signals proportional respectively to the last phase difference stored in said sample-and-hold circuit and a new such signal transferred from the output of said integrate-and-hold circuit, said transient detector producing two different series of output signals of opposite sign respectively dependent upon the sense of any difference between the compared values of said amplitude modulated signals and which exceeds a threshold difference value, and a reversible counter into which the output signals of opposite sign from said transient detector are fed and counted.

Claim 4

Apparatus for determining the displacement in phase as between two input periodic signals having essentially the same frequency which comprises: means converting each of said input signals into a corresponding rectangular voltage waveform, means producing from the intervals between homologous edges of said rectangular voltage waveforms a train of duration-modulated rectangular signal pulses corresponding respectively to the difference in phase at a 2 pi transition, an integrate-and-hold circuit in which the signal pulses in said pulse train are integrated over a predetermined period to form and hold a corresponding amplitude modulated voltage signal, a sample-and-hold circuit connected to the output of said integrate-and-hold circuit, means controlled in accordance with the duration of said rectangular signal pulses and operative only when the pulse duration exceeds a predetermined minimum corresponding to a minimum value of the phase displacement between said input periodic signals for effecting transfer to and storage of said amplitude modulated voltage signal from the output of said integrate-and-hold circuit in said sample-and-hold circuit, a transient detector circuit connected to said sample-and-hold circuit for effecting periodic comparison therein between old and new values of said amplitude modulated signals proportional respectively to the last phase difference stored in said sample-and-hold circuit and a new such signal transferred from the output of said integrate-and-hold circuit, said transient detector producing two different series of output signals of opposite sign respectively dependent upon the sense of any difference between the compared values of said amplitude modulated signals and which exceeds a threshold difference value, and a reversible counter into which the output signals of opposite sign from said transient detector are fed and counted.

Claim 5

Apparatus as defined in claim 2 wherein said threshold value of the difference between the values of said amplitude modulated signals which are compared in said transient detector circuit equals one-half the highest amplitudes of said amplitude modulated signals which can arise at the output of said integrate-and-hold circuit or at the output of said sample-and-hold circuit for a specific frequency of said periodic input signals.

Claim 6

Apparatus as defined in claim 2 wherein the two different series of signals of opposite sign produced at the output of said transient detector are logical signals which are then added in said reversible counter to produce a digital output therefrom and which further includes a digital-to-analog converter connected to said counter for converting the digital output therefrom into analog form, and means for combining the analog converted output of said counter with the analog output from said sample-and-hold circuit.

Claim 7

Apparatus as defined in claim 2 and which further includes means forming an additional train of rectangular pulses in which each pulse is initiated by passage of one of said periodic input signals through zero with a delay and terminated by passage of the other periodic input signal through zero, and a sequence control circuit controlled by and operated in accordance with the pulses of said additional pulse train, said sequence control circuit producing a sampling command transmitted to said sample-and-hold circuit, a comparison command transmitted to said transient detector circuit, and a reset command transmitted to said integrate-and-hold circuit.

Claim 8

Apparatus as defined in claim 5 wherein said sampling and comparison commands are applied respectively to said sample-and-hold circuit and to said transient detector circuit through respective gating means each of which is controlled jointly by the corresponding command and a further signal derived from the signal pulses of said pulse train and which further signal is indiCative of a pulse duration exceeding said predetermined minimum corresponding to the minimum value of the phase displacement between said input periodic signals.

Claim 9

Apparatus as defined in claim 2 wherein the signal pulses applied to said integrate-and-hold circuit are constituted by a pulse train in which the pulses are duration modulated in accordance with every other one of the pulses corresponding to the difference in phase of each 2 pi transition.

Claim 10

Apparatus as defined in claim 2 and which further includes means operable when the duration of said rectangular signal pulses is below the said predetermined minimum corresponding to the minimum value of the phase displacement between said input periodic signals for applying a constant voltage to the storage portion of said sample-and-hold circuit, said constant voltage being equal to the highest possible value of said amplitude modulated voltage signal for the case where the latest value of said voltage signal held in the storage portion of said sample-and-hold circuit is greater than the difference voltage threshold value selected for said transient detector circuit, and said constant voltage being equal to the lowest possible value of said amplitude modulated voltage signal for the case where the latest value of the voltage signal held in the storage portion of said sample-and-hold circuit is less than the difference voltage threshold value selected for said transient detector circuit.