Combined signal level meter and leakage detector

• US 5,633,582 A
• Filed: 02/14/1996
• Issued: 05/27/1997
• Est. Priority Date: 06/10/1993
• Status: Expired due to Term

• Current Assignee: Trilithic Incorporated (Lumentum Holdings Inc.)
• Original Assignee: Trilithic Incorporated (Lumentum Holdings Inc.)
• Inventors: Orndorff, Dennis L., Staley, Dennis W.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): BOWSER, BARRY
• Application Number:
  US08/601,194
• Time in Patent Office: 468 Days
• Field of Search: 324/96, 324/95
• US Class Current: 324/95
• CPC Class Codes: G01R 29/0871 Complete apparatus or systems; circuits, e.g. receivers or amplifiers G01R29/0878, G01R29/0892 take precedence; dosimeters, warning devices G01R29/0857
• CPC Class Codes: G01R 31/2825 in household appliances or professional audio/video equipment testing LAN's H04L43/50; testing TV systems H04N17/00; testing loudspeakers H04R29/00
• CPC Class Codes: H03D 7/161 all the frequency changers being connected in cascade
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 15/04 the interference being caused by substantially sinusoidal oscillations, e.g. in a receiver or in a tape-recorder
• CPC Class Codes: H04B 2001/1054 by changing bandwidth
• CPC Class Codes: H04B 2215/064 Reduction of clock or synthesizer reference frequency harmonics

Abstract

A combined signal level meter and leakage detector having a built-in antenna for the leakage detector, and dual clock frequency control of the microcontroller along with bandwidth switching for greater sensitivity in leakage detection mode. A data logging function is also provided. Control circuitry is also provided for avoiding receiver spurs by combined switching of multiple local oscillator frequencies, including combinations of high-side and low-side injection and IF shifting.

Claims

1. A combined signal level meter and leakage detector for a cable television system, comprising:

a CATV cable signal level input;

a CATV leakage signal antenna;

a heterodyne receiver circuit connected to said CATV cable signal level input and said CATV leakage signal antenna, said heterodyne receiver circuit having greater sensitivity for CATV leakage measurement than for CATV cable signal level measurement;

a detector having an input connected to said heterodyne receiver circuit;

a processing and control circuit having an input connected to said detector; and

display means for displaying signal level information and leakage information corresponding to signals supplied to said CATV cable signal level input and said CATV leakage signal antenna circuit, respectively.

2. The combined signal level meter and leakage detector claim 1, wherein said receiver circuit includes a tuned preamplifier having an input connected to said CATV leakage signal antenna.

3. The combined signal level meter and leakage detector of claim 2, wherein said receiver circuit includes an IF stage having a relatively wide bandwidth for CATV signal level measurement and a relatively narrow bandwidth for CATV leakage measurement.

4. The combined signal level meter and leakage detector of claim 3, wherein the terminal sensitivity at said CATV cable signal level input is greater than -45 dbmv and the terminal sensitivity at the input of said tuned preamplifier is less than 2 microvolts.

5. The combined signal level meter and leakage detector of claim 4, wherein said CATV leakage signal antenna comprises a built-in antenna.

6. The combined signal level meter and leakage detector claim 5, further comprising switch means between said built-in antenna and said receiver circuit for alternatively connecting to an external antenna.

7. The combined signal level meter and leakage detector claim 6, wherein said processing and control circuit includes a multi-frequency clock circuit having a relatively fast clock frequency for CATV signal level measurement and a relatively slow clock frequency for CATV leakage measurement.

8. The combined signal level meter and leakage detector of claim 7, wherein said receiver circuit includes at least one dedicated mixer for CATV signal level measurement and at least one dedicated mixer for CATV leakage measurement.

9. The combined signal level meter and leakage detector of claim 8, wherein said receiver circuit includes a dual-conversion front end and a single-conversion front end for converting to a common IF frequency.

10. The combined signal level meter and leakage detector of claim 1, wherein said receiver circuit includes an IF stage having a relatively wide bandwidth for CATV signal level measurement and a relatively narrow bandwidth for CATV leakage measurement.

11. The combined signal level meter and leakage detector of claim 1, wherein said receiver circuit has a terminal sensitivity of greater than -45 dbmv for CATV cable signal level measurement and a terminal sensitivity of less than 2 microvolts for CATV leakage measurement.

12. The combined signal level meter and leakage detector of claim 1, wherein said CATV leakage signal antenna comprises a built in antenna.

13. The combined signal level meter and leakage detector of claim 12, further comprising switch means between said built-in antenna and said receiver circuit for alternatively connecting to an external antenna.

14. The combined signal level meter and leakage detector of claim 1, wherein said processing and control circuit includes a multi-frequency clock circuit having a relatively fast clock frequency for CATV signal level measurement and a relatively slow clock frequency for CATV leakage measurement.

15. The combined signal level meter and leakage detector claim 1, wherein said receiver circuit includes at least one dedicated mixer for CATV signal level measurement and at least one dedicated mixer for CATV leakage measurement.

16. The combined signal level meter and leakage detector of claim 1, wherein said receiver circuit includes a dual-conversion front end and a single-conversion front end for converting to a common IF frequency.

17. The combined signal level meter and leakage detector of claim 1, wherein said receiver circuit is connected separately to said CATV cable signal level input and said CATV leakage signal antenna.

18. A combined signal level meter and leakage detector for a cable television system, comprising:

a CATV cable signal level input;

a CATV leakage signal antenna;

an RF section connected to said CATV cable signal level input and said CATV leakage signal antenna;

an IF section having an input connected to said RF section and including a relatively wide bandwidth circuit portion adapted for CATV signal level measurement and a relatively narrow bandwidth circuit portion adapted for CATV leakage measurement;

a detector having an input connected to said IF section;

a processing and control circuit having an input connected to said detector; and

display means for displaying a CATV signal level measurement and a CATV leakage measurement.

19. The combined signal level meter and leakage detector of claim 18, wherein said IF section includes a bandpass filter network having a relatively wide bandwidth for signal level measurement and a relatively narrow bandwidth for leakage measurement.

20. The combined signal level meter and leakage detector of claim 19, wherein said CATV leakage signal antenna comprises a built-in antenna.

21. The combined signal level meter and leakage detector of claim 20, further comprising switch means between said built-in antenna and said RF section for alternatively connecting to an external antenna.

22. The combined signal level meter and leakage detector of claim 21, wherein said processing and control circuit includes a multi-frequency clock circuit having a relatively fast clock frequency for CATV signal level measurement and a relatively slow clock frequency for CATV leakage measurement.

23. The combined signal level meter and leakage detector of claim 18, wherein said CATV leakage signal antenna comprises a built-in antenna.

24. The combined signal level meter and leakage detector of claim 23, further comprising switch means between said built-in antenna and said RF section for alternatively connecting to an external antenna.

25. The combined signal level meter and leakage detector of claim 18, wherein said processing and control circuit includes a multi-frequency clock circuit having a relatively fast clock frequency for CATV signal level measurement and a relatively slow clock frequency for CATV leakage measurement.

26. A method of measuring signal level and leakage in a cable television system, comprising the steps:

obtaining a CATV cable signal from a CATV cable;

obtaining a CATV leakage signal radiated from the CATV cable using an antenna;

supplying said CATV cable signal and said CATV leakage signal to a common heterodyne receiver;

providing greater sensitivity for CATV leakage measurement than for CATV cable signal level measurement;

demodulating the output signal of said heterodyne receiver; and

displaying signal level information and leakage information corresponding to signals obtained from said CATV cable connection and from said antenna, respectively.

27. The method of claim 26, wherein greater sensitivity is provided by preamplifying said CATV leakage signal from said antenna.

28. The method of claim 27, wherein greater sensitivity is further provided by switching the bandwidth of an IF stage from a relatively wide bandwidth for CATV signal level measurement to a relatively narrow bandwidth for CATV leakage measurement.

29. The method of claim 28, wherein a terminal sensitivity of greater than -45 dbmv is provided for CATV cable signal level measurement and a terminal sensitivity of less than 2 microvolts is provided for CATV leakage measurement.

30. The method of claim 29, wherein said CATV leakage signal is obtained with an antenna permanently attached to a case housing said heterodyne receiver and said display.

31. The method of claim 30, further comprising the step of alternatively obtaining said CATV leakage signal with an antenna removably attached to said case.

32. The method of claim 31, further comprising the step of processing said CATV cable signal and said CATV leakage signal in a processor having a relatively fast clock frequency for CATV signal level measurement and a relatively slow clock frequency for CATV leakage measurement.

33. The combined signal level meter and leakage detector of claim 32, wherein said CATV cable signal and said CATV leakage signal are supplied to a common heterodyne receiver having at least one dedicated mixer for CATV signal level measurement and at least one dedicated mixer for CATV leakage measurement.

34. The combined signal level meter and leakage detector of claim 33, further comprising the step of converting said CATV cable signal and said CATV leakage signal to a common IF frequency, said converting step including double frequency conversion of said CATV cable signal and single frequency conversion of said CATV leakage signal.

35. A cable television instrumentation system, comprising:

a source of CATV signals;

a cable distribution system connected to said source and carrying said CATV signals; and

a combined signal level meter and leakage detector coupled to said cable distribution system and comprising

a) a CATV cable connector connected to said cable distribution system;

b) a CATV leakage signal antenna in proximity to said cable distribution system;

c) a receiver connected to said CATV cable connector and said CATV leakage signal antenna, said receiver having greater sensitivity for CATV leakage measurement than for CATV cable signal level measurement; and

d) display means for selectively displaying signal level information and leakage information corresponding to signals obtained from said CATV cable connector and from said CATV leakage signal antenna, respectively.

36. The combined signal level meter and leakage detector claim 35, wherein said receiver includes a tuned preamplifier having an input connected to said CATV leakage signal antenna.

37. The combined signal level meter and leakage detector of claim 36, wherein said receiver includes an IF stage having a relatively wide bandwidth for CATV signal level measurement and a relatively narrow bandwidth for CATV leakage measurement.

38. The combined signal level meter and leakage detector of claim 37, wherein the terminal sensitivity at said CATV cable connector is greater than -45 dbmv and the terminal sensitivity at the input of said tuned preamplifier is less than 2 microvolts.

39. The combined signal level meter and leakage detector of claim 38, wherein said CATV leakage signal antenna comprises a built-in antenna.

40. The combined signal level meter and leakage detector of claim 39, further comprising switch means between said built-in antenna and said receiver for alternatively connecting to an external antenna.

41. The combined signal level meter and leakage detector of claim 40, further comprising a processing and control circuit with a multi-frequency clock circuit having a relatively fast clock frequency for CATV signal level measurement and a relatively slow clock frequency for CATV leakage measurement.

42. The combined signal level meter and leakage detector of claim 41, wherein said receiver includes at least one dedicated mixer for CATV signal level measurement and at least one dedicated mixer for CATV leakage measurement.

43. The combined signal level meter and leakage detector of claim 42, wherein said receiver includes a dual-conversion front end and a single-conversion front end for converting to a common IF frequency.

44. A cable television instrumentation system, comprising:

a source of CATV signals;

a cable distribution system connected to said source and carrying said CATV signals; and

a combined signal level meter and leakage detector coupled to said cable distribution system and comprising

a) an instrument case;

b) a CATV cable connector connected to said cable distribution system;

c) a plurality of CATV leakage signal antennas in proximity to said cable distribution system;

d) a receiver separately connected to said CATV cable connector and one of said CATV leakage signal antennas, said receiver including

1) a tuned preamplifier having an input connected to said one CATV leakage signal antenna;

2) at least one dedicated mixer for CATV signal level measurement;

3 at least one dedicated mixer for CATV leakage measurement;

4) at least one common mixer for CATV signal level measurement and CATV leakage measurement; and

5) an IF stage having a relatively wide bandwidth for CATV signal level measurement and a relatively narrow bandwidth for CATV leakage measurement; and

e) display means for selectively displaying signal level information and leakage information corresponding to signals obtained from said CATV cable connector and from said one CATV leakage signal antenna, respectively.