US 4,412,299 A · Phase jitter detector

Abstract

A phase jitter detector that is ideally suited for use in combination with tone receivers (e.g., tone-to-pulse converters) to provide a speech immune tone detection system or in a measuring instrument to provide a direct measurement of the signal-to-noise ratio (SNR) of a signal is disclosed. In either application, the phase jitter detector can be implemented in either phase locked loop or digital logic form. Regardless of how implemented, the phase jitter detector determines the phase jitter of an incoming signal by first squaring the signal (by passing the incoming signal through a high gain amplifier that limits the signal, for example). After squaring, the phase jitter of the squared signal is determined by: (1) determining the phase deviation of each cycle of the squared signal with respect to the average frequency of the squared signal over a predetermined number of cycles; and (2) combining the phase deviation and the predetermined number of cycles information to determine phase jitter. In tone detection system applications, the phase jitter information is used to control whether or not a tone receiver is to complete a tone conversiono sequence. In SNR measuring applications, the phase jitter information is converted into SNR form and displayed.

Claims40

Dependent claims

A phase jitter detector for determining the phase jitter of an incoming signal comprising:

(A) squaring means for receiving and squaring the wave shape of said incoming signal;
and,
(B) electronic circuit means coupled to said squaring means for determining the phase jitter of said incoming signal by:
(i) determining the phase difference between each cycle of the squared incoming signal and the average frequency of the squared incoming signal over a predetermined number of preceeding cycles of the incoming signal;
and, (ii) combining said phase difference information and said predetermined number of cycles information to determine the phase jitter of said incoming signal, said electronic circuit means including:
(1) phase determining means coupled to said squaring means for determining the phase difference between each cycle of the squared incoming signal and the average frequency of the preceeding cycles of said squared incoming signal and producing an output signal containing said phase difference information;
(2) cycle counting means incremented at a rate related to the frequency of said incoming signal;
and,
(3) digital integrating means coupled to said phase determining means and to said cycle counting means for integrating the output of said phase determining means containing said phase difference information over a predetermined number of cycles of said incoming signal counted by said counting means, said integrated output signal information defining the phase jitter of said incoming signal over the predetermined number of cycles counted by said cycle counting means.

6 more elements

A phase jitter detector for determining the phase jitter of an incoming signal comprising:

(A) squaring means for receiving and squaring the wave shape of said incoming signal;
and,
(B) electronic circuit means coupled to said squaring means for determining the phase jitter of said incoming signal by:
(i) determining the phase difference between each cycle of the squared incoming signal and the average frequency of the squared incoming signal over a predetermined number of preceeding cycles of the incoming signal;
and, (ii) combining said phase difference information and said predetermined number of cycles information to determine the phase jitter of said incoming signal, said electronic circuit means including digital logic means for:
(1) measuring the time between preselected directional transitions of said squared incoming signal (x.sub.i) over said predetermined number of cycles (n) of said incoming signal;
(2) determining the mean time between said preselected directional transitions of said squared incoming signal (x);
(3) determining the phase difference between each of said measured time between transitions and said mean time between transitions (x.sub.i -x);
and,
(4) determining the phase jitter of said incoming signal based on said phase difference information and said predetermined number of cycles.

7 more elements

A speech immune tone detection system comprising:

(A) a squaring circuit for receiving an incoming signal and squaring the wave shape of said signal;
(B) a tone receiver coupled to the output of said squaring circuit for receiving said squared incoming signal and determining whether or not said squared incoming signal is a valid tone signal, said tone receiver formed so as to perform short and long-term checks of said squared incoming signal to determine whether or not said incoming signal is a valid tone signal, said tone receiver producing a preliminary evaluation output signal when said squared incoming signal passes said short-term check;
(C) electronic circuit means coupled to said squaring circuit and said tone receiver for determining the phase jitter of said incoming signal and inhibiting the operation of said tone receiver when said phase jitter is determined to be above a predetermined level by:
(1) determining the phase difference between each cycle of the squared incoming signal and the average frequency of the squared incoming signal over a predetermined number of preceeding cycles of the incoming signal;
(2) combining said phase difference information and said predetermined number of cycles information to determine the phase jitter of said incoming signal;
and,
(3) inhibiting said tone receiver if said phase jitter lies above a predetermined level.

4 more elements

A signal-to-noise ratio measuring system comprising:

(A) a squaring circuit for receiving and squaring the wave shape of the signal whose signal-to-noise ratio is to be measured;
(B) electronic circuit means coupled to said squaring means for measuring the signal-to-noise ratio of said incoming signal by:
(i) determining the phase difference between each cycle of the squared incoming signal and the average frequency of the squared incoming signal over a predetermined number of preceeding cycles of the incoming signal;
(i) combining said phase difference information and said predetermined number of cycles information to determine the phase jitter of said incoming signal;
and, (iii) converting said phase jitter into signal-to-noise ratio form, said electronic circuit means including:
(1) phase determining means connected to the output of said squaring means for determining the phase difference between each cycle of the signal whose signal-to-noise ratio is to be determined and the average frequency of the preceeding cycles of said signal and producing a related phase difference output signal;
(2) cycle counting means for counting at a rate related to the frequency of said incoming signal;
(3) signal detecting means connected to the output of said squaring means for detecting the presence of the signal whose signal-to-noise ratio is to be determined, said signal detecting means connected to said cycle counting means for inhibiting the operation of said cycle counting means until said signal detecting means detects the presence of the signal whose signal-to-noise ratio is to be measured;
and,
(4) digital integrating means connected to said phase determining means for integrating the phase difference output signal of said phase determining means and to said cycle counting means for being reset when said cycle counting means reaches a predetermined level;
and,
(C) display means connected to the output of said digital integrating means for displaying the output of said digital integrating means just prior to said digital integrating means being reset by said cycle counting means, said display representing the signal-to-noise ratio of the signal whose signal-to-noise ratio is to measured.

9 more elements

The signal-to-signal-to-noise ratio measuring system comprising:

(A) a squaring means for receiving and squaring the wave shape of the signal whose signal-to-noise ratio is to be measured;
(B) electronic circuit means coupled to said squaring means for measuring the phase jitter of said incoming signal by:
(i) determining the phase difference between each cycle of the squared incoming signal and the average frequency of the squared incoming signal over a predetermined number of preceeding cycles of the incoming signal;
(ii) combining said phase difference information and said predetermined number of cycles information to determine the phase jitter of said incoming signal;
and, (iii) converting said phase jitter into signal-to-noise ratio form, said electronic circuit means including a digital logic means for:
(1) measuring the time between preselected directional transitions of said squared incoming signal (x.sub.i) over said predetermined number of cycles (n) of said incoming signal;
(2) determining the mean time between said preselected directional transitions of said squared incoming signal (x);
(3) determining the phase difference between each of said measured time between transitions and said mean time between transitions (x.sub.i -x);
(4) determining the phase jitter of said incoming signal based on said phase difference information and said predetermined number of cycles;
and,
(5) converting said phase jitter data into said signal-to-noise ratio data;
and,
(C) display means coupled to said electronic circuit means for displaying said signal-to-noise ratio data.

10 more elements

Dependencies are inferred from the claim text.

Phase jitter detector

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Phase jitter detector

Life of this patent

Abstract

Claims40