Method and apparatus for fast response and distortion measurement
AssigneeAudio Precision, Inc.
InventorRichard C. Cabot
Life of this patent
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Abstract
A method and apparatus for fast response and distortion measurement of a signal transfer device. A computer processor generates a multitone test signal of predetermined duration and stores it in a memory. The test signal is read out, converted to analog form, if necessary, and applied to the input of a device under test. The output produced by the device under test in response to the test signal is acquired and digitized, if necessary, and a Fast Fourier Transform is performed on the acquired data to determine its spectral characteristics. Frequency response, harmonic distortion, intermodulation distortion, phase distortion, wow and flutter and other signal transfer characteristics are measured by the CPU by analysis of the output signal.
Claims26
A method for measuring signal transfer characteristics of a signal transfer device under test, said device having inputs and at least one output, comprising the steps of:
- (a) simultaneously applying to at least two of the inputs respective pluralities of distinct, substantially sinusoidal test signals selected so that their frequencies are integer multiples of a common frequency whose period is equal in duration to a signal generation time block, the signals applied to at least one said input including one or more selected frequencies not applied to at least one other input;
- (b) acquiring a first signal from a first output of said device under test for a measurement time block equal in duration to an integer number of signal generation time blocks;
- (c) performing a time-to-frequency transform on the acquired signal to determine its spectral characteristics to a frequency resolution which is an integer sub-multiple of said common frequency;
- and
- (d) measuring the amplitude of at least one selected frequency in said first acquired signal to obtain the measure of a signal transfer characteristic of said device under test.
A method for measuring the signal transfer characteristics of a signal transfer device under test, said device having an input and an output, comprising the steps of:
- (a) simultaneously applying to said input of said device under test a plurality of distinct, substantially sinusoidal test signals selected so that their frequencies are integer multiples of a common frequency whose period is equal in duration to a signal generation time block;
- (b) acquiring a signal from said output of said device under test for a measurement time block equal in duration to an integer number of signal generation time blocks;
- (c) performing a time-to-frequency transform on the acquired signal to determine its spectral characteristics to a frequency resolution which is an integer sub-multiple of said common frequency;
- and
- (d) measuring the amplitude at one or more frequencies which are not integer multiples of said common frequency to obtain an indication of noise in the device under test.
An apparatus for measuring signal transfer characteristics of a signal transfer device under test, said device having inputs and at least one output, comprising:
- (a) source means for simultaneously applying to at least two of the inputs respective pluralities of distinct, substantially sinusoidal test signals selected so that their frequencies are integer multiples of a common frequency whose period is equal in duration to a signal generation time block, the signals applied to at least one said input including one or more selected frequencies not applied to at least one other input;
- (b) acquisition means for acquiring a first signal from a first output of said device under test for a measurement time block equal in duration to an integer number of signal generation time blocks;
- (c) transform means for performing a time-to-frequency transform on acquired signal to determine its spectral characteristics to a frequency resolution which is an integer sub-multiple of said common frequency;
- and
- (d) measuring means for measuring the amplitude of at least one selected frequency in said first acquired signal to obtain the measure of a signal transfer characteristic of said device under test.
An apparatus for measuring the signal transfer characteristics of a signal transfer device under test, said device having an input and an output, comprising:
- (a) source means for simultaneously applying to said input of said device under test a plurality of distinct, substantially sinusoidal test signals selected so that their frequencies are integer multiples of a common frequency whose period is equal in duration to a signal generation time block;
- (b) acquisition means for acquiring a signal from said output of said device under test for a measurement time block equal in duration to an integer number of signal generation time blocks;
- (c) transform means for performing a time-to-frequency transform on the acquired signal to determine its spectral characteristics to a frequency resolution which is an integer sub-multiple of said common frequency;
- and
- (d) measuring means for measuring the amplitude at one or more frequencies which are not integer multiples of said common frequency to obtain an indication of noise in the device under test.
Dependencies are inferred from the claim text.