Method and apparatus for leakage detection using pulsed RF tagging signal

• US 6,118,975 A
• Filed: 12/02/1997
• Issued: 09/12/2000
• Est. Priority Date: 12/02/1997
• Status: Expired due to Term

• Current Assignee: Wavetek Wandel Goltermann LLC
• Original Assignee: Wavetek Wandel Goltermann LLC
• Inventors: Bowyer, Andrew E., Franchville, Douglas J.
• Primary Examiner(s): GRANT, CHRISTOPHER C
• Application Number:
  US08/982,935
• Time in Patent Office: 1,015 Days
• Field of Search: 348/1, 348/2, 348/3, 348/4, 348/5, 348/6, 348/12, 348/13, 348/192, 348/193, 455/3.1, 455/5.1, 455/6.1, 455/4.1, 455/67.3, 455/67.4
• US Class Current: 725/107
• CPC Class Codes: H04N 17/00 Diagnosis, testing or measuring for television systems or their details
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence

Abstract

An exemplary leakage tagging signal generator according to the present invention is intended for use in connection with a leakage tagging signal detector that detects signal leakage in a communication system. In particular, the leakage tagging signal generator is intended for use with a leakage tagging signal detector that identifies leakage tagging signals based on the detection of a characteristic leakage tagging frequency component. The leakage tagging signal generator includes an RF signal source, an output, a switch, and a pulse signal source. The RF signal source is operable to generate an RF carrier signal having a first frequency. The output connects to the communication system. The pulse signal source is a device operable to generate a pulse signal having a first state and a second state, said pulse signal having a pulse period. The pulse period of the pulse signal includes a first portion in which the pulse signal is in the first state and a second portion in which the pulse signal is in the second state. The pulse period futhermore corresponds to the characteristic tagging frequency. The switch is connected to the pulse signal source. The switch is operable to provide a first discrete signal level of the RF carrier signal to the output responsive to the pulse signal being in the first state, and to provide a second discrete level of the RF carrier signal to the output responsive to the pulse signal being in the second state, thereby producing a pulsed RF signal having the pulse period.

Claims

1. A method transmitting a tagging signal in a communication system to a leakage tagging signal detector, said leakage tagging signal detector operable to identify leakage tagging signals based on the detection of a predetermined characteristic tagging frequency component, comprising:

a) generating a pulsed RF signal, the pulsed RF signal having a first discrete signal level, a second discrete signal level which is substantially less than the first discrete signal level, an RF carrier frequency, and a pulse period, wherein said pulse period defines a first harmonic component that corresponds to the characteristic tagging frequency; and

b) providing the pulsed RF signal to the communication system to facilitate a leakage measurement.

2. The method of claim 1 wherein step a) further comprises generating a pulsed RF signal by modulating an RF carrier signal having the RF frequency with a pulse signal having first and second states, and wherein the RF signal has the first discrete signal level when the pulse signal is in the first state and the RF signal has the second discrete signal level when the pulse signal is in the second state.

3. The method of claim 1 wherein step a) further comprises generating the pulsed RF signal such that the pulsed RF signal has a duty cycle that corresponds to a predetermined modulation depth of the first harmonic component with respect to the RF carrier signal.

4. The method of claim 2 wherein step a) further comprises generating a pulse signal comprising a square wave signal.

5. The method of claim 4 wherein step a) further comprises employing a microprocessor to generate the square wave signal.

6. The method of claim 1 wherein step a) further comprises generating the pulsed RF signal wherein the pulsed RF signal has an RF carrier frequency of between approximately 115 MHz and approximately 140 MHz.

7. The method of claim 6 wherein step a) further comprises generating the pulse RF signal wherein the pulsed RF signal has an RF carrier frequency that corresponds to an unused CATV channel frequency.

8. The method of claim 1 wherein step a) further comprises generating the pulse RF signal wherein the pulsed RF signal has an RF carrier frequency that corresponds to an unused CATV channel frequency.

9. The method of claim 1 wherein step a) further comprises generating the pulsed RF signal such that the second discrete signal level is substantially zero.

10. A leakage tagging signal generator for use in connection with a leakage tagging signal detector for detecting signal leakage in a communication system, said leakage tagging signal detector operable to identify leakage tagging signals based on the detection of a characteristic leakage tagging frequency component, the leakage tagging signal generator comprising:

a) an RF signal source operable to generate an RF carrier signal having a first frequency;

b) an output for connecting to the communication system;

c) a pulse signal source operable to generate a pulse signal having a first state and a second state, said pulse signal having a pulse period, the pulse period including a first portion in which the pulse signal is in the first state and a second portion in which the pulse signal is in the second state, the pulse period corresponding to the characteristic tagging frequency; and

d) a means, connected to the pulse signal source, for providing the RF carrier signal to the output responsive to the pulse signal being in the first state and removing the RF carrier signal to the output responsive to the pulse signal being in the second state, thereby producing a pulsed RF signal having the pulse period.

11. The leakage tagging signal generator of claim 10 wherein the pulse signal source is further operable to generate the pulse signal in which the pulse signal is a square wave signal.

12. The leakage tagging signal generator of claim 11 wherein the pulse signal source is further operable to generate the pulse signal wherein the pulse signal has a duty cycle defined by the first portion of the pulse period, the duty cycle corresponding to a predetermined modulation depth of a first harmonic component of the pulsed RF output signal.

13. The leakage tagging signal generator of claim 10 wherein the RF signal source is further operable to generate the RF carrier signal wherein the RF carrier signal has a first frequency that corresponds to an unused CATV channel.

14. The leakage tagging signal generator of claim 13 wherein the RF signal source is further operable to generate the RF carrier signal wherein the RF carrier signal has a first frequency between approximately 115 MHz and approximately 140 MHz.

15. The leakage tagging signal generator of claim 10 wherein the RF signal source is further operable to generate the RF carrier signal wherein the RF carrier signal has a first frequency that corresponds to an unused CATV channel.

16. The leakage tagging signal generator of claim 10 wherein the pulse signal source includes a microprocessor.

17. The leakage tagging signal generator of claim 10 wherein the means for providing comprises an RF switch.

18. The leakage tagging signal generator of claim 10 wherein the means for providing comprises a variable attenuator.