Time domain phase measuring apparatus
First Claim
1. Apparatus for deriving time domain measures of phase and/or period stability of a device being tested comprising means responsive to a test signal applied to the device for deriving a DC signal component having an amplitude indicative of the phase shift introduced by the device, means responsive to the DC signal component for converting the amplitude of the DC signal component into a time interval indication, said converting means including means for combining the amplitude of the DC signal with the amplitude of a ramp waveform.
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Abstract
The phase and/or period stability of a device being tested is determined by connecting the device in one orthogonal arm of a phase detector having a mixer. In the other arm is an adjustable, variable phase shift device, such as a line stretcher. The output of the mixer is fed through an active low pass filter to derive a DC voltage indicative of the phase shift of the tested device. Initially, the variable phase device is adjusted so that the DC voltage is approximately zero to nullify the phase shift of the tested device under normal conditions. The DC voltage level is converted into a time interval indicative of the phase change of the tested device by determining when the level equals the amplitude of a low frequency ramp voltage that functions similar to a beat frequency output of a prior art dual mixer detector. The interval between adjacent equality points for the phase indicating voltage and the ramp voltage can be measured or the period between a reference point on the ramp voltage and the equality between the ramp voltage and the phase indicating voltage can be measured.
21 Citations
16 Claims
- 1. Apparatus for deriving time domain measures of phase and/or period stability of a device being tested comprising means responsive to a test signal applied to the device for deriving a DC signal component having an amplitude indicative of the phase shift introduced by the device, means responsive to the DC signal component for converting the amplitude of the DC signal component into a time interval indication, said converting means including means for combining the amplitude of the DC signal with the amplitude of a ramp waveform.
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8. Apparatus for deriving time domain measures of phase and/or period stability of a device being tested comprising a time reference source;
- a phase detector responsive to the time reference source, said phase detector including;
a pair of orthogonal channels driven by the time reference source, and a mixer responsive to the channels for deriving a DC signal component having an amplitude indicative of the phase difference of outputs of the two channels, one of the channels including the tested device, one of the channels including a variable phase shifter that is initially adjusted so that the DC signal component has approximately zero amplitude;
means responsive to the time reference source for deriving a ramp waveform having a frequency much lower than the frequency of the time reference source, said ramp waveform deriving means including frequency divider means for deriving a pulse type waveform at the much lower frequency, and a passive low pass filter responsive to the pulse type waveform for deriving the ramp waveform; and
means responsive to the ramp waveform and the DC signal component for converting the amplitude of the DC signal into a time interval indication. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
- a phase detector responsive to the time reference source, said phase detector including;
Specification