Group delay measurement apparatus and method
AssigneeHewlett-Packard Company
InventorDavid D. Sharrit
Life of this patent
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Abstract
A network analyzer which compares a reference signal supplied to a device under test with an output signal from the device under test is used to measure the group delay caused by the device under test. The reference signal is produced by a swept frequency signal generator. During the sweep of the signal generator the difference between the instantaneous frequencies of the reference signal and the output signal from the device under test is determined as is the rate of change of the frequency of the reference signal. The instantaneous frequency difference is divided by the rate of change of the reference frequency to produce an instantaneous indication of the group delay produced by the device under test.
Claims11
A method of measuring the group delay of a device under test comprising the steps of:
- generating an a.c. signal that is varied from a first to a second frequency;
- generating a control signal that varies in accordance with the frequency of the a.c. signal;
- supplying the a.c. signal to a device under test;
- receiving an output signal from the device under test;
- determining the instantaneous frequency difference between the a.c. signal and the output signal;
- determining the instantaneous rate of change of the control signal;
- and
- dividing the instantaneous frequency difference by the instantaneous rate of change of the control signal to produce a signal indicative of the group delay of the device under test.
An apparatus for measuring the group delay of a device under test, the apparatus comprising:
- a signal generator for producing an a.c. signal that varies from a first to a second frequency and for producing a control signal that varies in accordance with the frequency of the a.c. signal;
- output connector means for supplying the a.c. signal to a device under test;
- input connector means for receiving an output signal from a device under test;
- frequency measuring means connected to the signal generator and the input connector means for determining the instantaneous frequency difference between the a.c. signal and the output signal and for producing a difference signal indicative of the instantaneous frequency difference;
- differentiator means connected to the signal generator for determining the instantaneous rate of change of the control signal and for producing a slope signal indicative of the instantaneous rate of change of the control signal;
- and
- divider means connected to the frequency measuring means and to the differentiator means for dividing the difference signal by the slope signal to produce a measurement signal indicative of the group delay of a device under test.
Dependencies are inferred from the claim text.