Method and apparatus for communicating auxiliary information in a measurement signal

• US 5,649,304 A
• Filed: 04/07/1995
• Issued: 07/15/1997
• Est. Priority Date: 09/20/1991
• Status: Expired due to Term

• Current Assignee: Hp Holdings Three, Inc.
• Original Assignee: Audio Precision, Inc. (API Holdings LLC)
• Inventors: Cabot, Richard C.
• Primary Examiner(s): Urban, Edward F.
• Application Number:
  US08/419,058
• Time in Patent Office: 830 Days
• Field of Search: 455/67.1, 455/67.2, 455/67.3, 455/67.4, 455/226.3, 455/226.4, 455/229, 455/295, 324/612-615, 324/620, 324/623, 324/624, 324/76.24, 324/76.38, 324/76.58, 324/528, 364/484, 364/485, 364/487, 364/553, 364/570, 379/1, 379/6, 379/22, 379/27, 379/29
• US Class Current: 455/67.14
• CPC Class Codes: G01R 23/20 Measurement of non-linear distortion

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. The multitone test signals a unique combination which is extracted at the output for identifying the source, or location, of the test signals.

Claims

1. A method for communicating auxiliary information, such as the identity of persons, places and things, in conjunction with measuring the signal transfer characteristics of a signal transfer device under test, said device under test having an input and an output, comprising the steps of:

(a) defining a plurality of unique combinations of substantially sinusoidal test signals selected so as to determine the signal transfer characteristics of said device under test and to represent said auxiliary information, wherein said auxiliary information comprises the identity of the source of said test signals;

(b) applying one of said unique combinations of test signals to the input of said device under test;

(c) measuring the spectral characteristics of the output of said device under test to determine the signal transfer characteristics of said device under test; and

(d) extracting said auxiliary information from the output of said device under test by identifying which of said unique combinations of test signals is present at the output of said device under test.

2. The method of claim 1, wherein said auxiliary information is encoded in the phase relationship between a plurality of said sinusoidal components.

3. The method of claim 1, wherein said auxiliary information is encoded in the frequency relationship between a plurality of said sinusoidal components.

4. The method of claim 1, wherein said auxiliary information is encoded in the frequency and phase relationship between a plurality of said sinusoidal components.

5. The method of claim 1, wherein said device under test is a transmission channel, said method further comprising the step of interrupting program material on the transmission channel for a predetermined period of time and inserting said transmitted signal during said predetermined period of time.

6. A system for communicating auxiliary information, such as the identity of persons, places and things, in conjunction with measuring the signal transfer characteristics of a single transfer device under test, said device under test having an input and an output, comprising:

(a) means for defining a plurality of unique combinations of substantially sinusoidal test signals selected so as to determine the signal transfer characteristics of said device under test and to represent said auxiliary information, wherein said auxiliary information comprises the identity of the source of said test signals;

(b) means for applying one of said unique combinations of test signals to the input of said device under test;

(c) means for measuring the spectral characteristics of the output of said device under test to determine the signal transfer characteristics of said device under test; and

(d) means for extracting said auxiliary information from the output of said device under test by identifying which of said unique combinations of test signals is present at the output of said device under test.

7. The system of claim 6, wherein said auxiliary information is encoded in the phase relationship between a plurality of said sinusoidal components.

8. The system of claim 6, wherein said auxiliary information is encoded in the frequency relationship between a plurality of said sinusoidal components.

9. The system of claim 6, wherein said auxiliary information is encoded in the frequency and phase relationship between a plurality of said sinusoidal components.

10. The system of claim 6, wherein said device under test is a transmission channel, said system further comprising interrupting program material on the transmission channel for a predetermined period of time and inserting said transmitted signal during said predetermined period of time.

11. A method for communicating auxiliary information, such as the identity of persons, places and things, in conjunction with measuring the signal transfer characteristics of a signal transfer device under test, said device under test having an input and an output, comprising the steps of:

(a) defining a unique combination of substantially sinusoidal test signals selected so as to represent said auxiliary information, wherein said auxiliary information comprises the identity of the source of said test signals;

(b) applying said unique combination of test signals to the input of said device under test;

(c) measuring the spectral characteristics of the output of said device under test to determine the signal transfer characteristics of the device under test; and

(d) extracting said auxiliary information from the output of said device under test by identifying said unique combination of test signals.

12. A system for communicating auxiliary information, such as the identity of persons, places and things, in conjunction with measuring the signal transfer characteristics of a signal transfer device under test, said device under test having an input and an output, comprising:

(a) means for defining a unique combination of substantially sinusoidal test signals so as to represent said auxiliary information, wherein said auxiliary information comprises the identity of the source of said test signals;

(b) means for applying said unique combination of test signals to the input of said device under test;

(c) means for measuring the spectral characteristics of the output of said device under test to determine the signal transfer characteristics of said device under test; and

(d) means for extracting said auxiliary information from the output of said device under test by identifying said unique combination of test signals.