CATV frequency sweep testing remote unit

• US 6,160,991 A
• Filed: 01/21/1999
• Issued: 12/12/2000
• Est. Priority Date: 09/19/1994
• Status: Expired due to Term

• Current Assignee: Wavetek Corp. (Lumentum Holdings Inc.)
• Original Assignee: Wavetek Wandel Goltermann LLC
• Inventors: Voght, Timothy R., Chappell, Daniel K.
• Primary Examiner(s): Grant, Chris
• Application Number:
  US09/234,598
• Time in Patent Office: 691 Days
• Field of Search: 455/3.1, 455/5.1, 455/6.1, 455/6.2, 455/6.3, 348/6, 348/12, 348/13, 348/192, 348/193
• US Class Current: 725/105
• 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
• CPC Class Codes: H04N 7/16 Analogue secrecy systems; Analogue subscription systems

Abstract

A method, system and apparatus for frequency sweeping and frequency sweep testing a CATV system wherein the CATV system has a plurality of channels and is transmitting television signals over at least some of the channels. The system includes a head end test unit coupled to the CATV system at its head end and a remote test unit coupled to the CATV system at a location remote from the head end. The head end test unit sweeps the CATV system by either generating and transmitting test signals at the channel frequencies over the CATV system or, if a television signal is being transmitted on a channel, using the television signal as the test signal. The head end test also measures the signal levels of the test signal and at the end of the sweep, transmits telemetry signals, which include the frequencies to be swept and the measured signal levels, over the CATV system to the remote test unit using the same transmitter that it use to generate and transmit the test signals. The remote test unit receives the information transmitted by the head end test unit and sweeps the same frequencies simultaneously with the head end test unit. During the sweep, the remote test unit measures the signal levels of the test signal and television signal test signals. After receiving the next set of telemetry signals, the remote test unit uses the information regarding the signal levels measured by the head end test unit and the signal levels it measured to determine the frequency response of the CATV system.

Claims

1. An apparatus for frequency sweep testing a CATV system, the CATV system having a plurality of channels, each channel corresponding to at least one of a plurality of channel frequencies, the plurality of channel frequencies including unused channel frequencies and used channel frequencies, the apparatus comprising:

a) an RF receiver circuit configured to receive RF test signals from the CATV system and to receive first and second RF telemetry signals, the first RF telemetry signal including information identifying a list of frequencies to be swept;

the second RF telemetry signal including information identifying transmitter measurement results, the RF receiver circuit operable to obtain RF test signal measurements from the RF test signals;

b) a controller coupled to the RF receiver circuit, the controller operable to;

obtain the list of frequencies to be swept from the first RF telemetry signal received by the RF receiver circuit;

cause the RF receiver circuit to obtain RF test signal measurements from corresponding to the plurality of frequencies to be swept;

obtain the RF test signal measurements from the RF receiver circuit;

obtain the transmitter measurement results from the second RF telemetry signal received by the RF receiver circuit; and

compare the transmitter measurement results to the RF test signal measurements to obtain test results.

2. The apparatus of claim 1 wherein the RF receiver circuit comprises:

a plurality of mixers;

a signal level measurement circuit operably coupled to at least one of the plurality of mixers, the signal level measurement circuit further operably coupled to the controller; and

a digital demodulator circuit operably coupled to at least one of the plurality of mixers, the digital demodulator circuit further operably coupled to the controller.

3. The apparatus of claim 2 wherein the signal level measurement circuit comprises a signal detector and an analog to digital converter.

4. The apparatus of claim 3 wherein the digital demodulator comprises an FSK demodulator and a manchester decoder.

5. The apparatus of claim 2 wherein the digital demodulator comprises an FSK demodulator and a manchester decoder.

6. The apparatus of claim 1 wherein the RF receiver circuit is further operable to receive the first and second RF telemetry signals from the CATV system.

7. The apparatus of claim 1 further comprising a display for displaying information representative of the test results.

8. The apparatus of claim 1 further comprising a memory for storing information representative of the test results.

9. The apparatus of claim 1 wherein the controller is further operable to cause the RF receiver circuit to obtain RF test signal measurements corresponding to the plurality of frequencies to be swept and to obtain the RF test signal measurements by:

a) causing the RF receiver circuit to tune to a first frequency in the list of frequencies to be swept;

b) causing the RF receiver circuit to obtain a first RF test signal measurement corresponding to the first frequency;

c) obtaining the first RF test signal measurement from the RF receiver circuit;

d) causing the RF receiver circuit to tune to a subsequent frequency in the list of frequencies to be swept;

e) causing the RF receiver circuit to obtain a subsequent RF test signal measurement corresponding to the subsequent frequency;

f) obtaining the subsequent RF test signal measurement from the RF receiver circuit;

g) repeating steps d, e, and f for each remaining frequency in the list of frequencies to be swept.

10. The apparatus of claim 1 wherein the first RF telemetry signal further includes information identifying a signal type corresponding to each frequency of the list of frequencies to be swept, and wherein the controller is further operable to obtain the signal type corresponding to each frequency of the list of frequencies to be swept from the first RF telemetry signal received by the RF receiver circuit.

11. In an apparatus including an RF receiver circuit and a controller for use in a CATV system, the CATV system having a plurality of channels, each channel corresponding to at least one of a plurality of channel frequencies, the plurality of channel frequencies including unused channel frequencies and used channel frequencies, a method of sweep testing the CATV system comprising:

a) receiving in the RF receiver circuit, a first RF telemetry signal, the first RF telemetry signal including information identifying a list of frequencies to be swept;

b) storing the list of frequencies to be swept;

c) using the controller to cause the RF receiver circuit to receive RF test signals from the CATV system and obtain RF test signal measurements therefrom;

d) storing the RF test signal measurements;

e) receiving in the RF receiver, a second RF telemetry signal, the second RF telemetry signal including information identifying transmitter measurement results;

f) using the controller to compare the transmitter measurement results to the RF test signal measurements to obtain test results.

12. The method of claim 11 wherein step a further comprises receiving the first RF telemetry signal from the CATV system and step e further comprises receiving the second RF telemetry signal from the CATV system.

13. The method of claim 11 further comprising a step of displaying information representative of the test results.

14. The method of claim 11 further comprising a step of storing information representative of the test results in a memory.

15. The method of claim 11 wherein steps c and d further comprise:

c1) using the controller to cause the RF receiver circuit to tune to a first frequency in the list of frequencies to be swept;

c2) using the controller to cause the RF receiver circuit to receive a first RF test signal corresponding to the first frequency and obtain a first RF test signal measurement therefrom;

d1) storing the first RF test signal measurement;

c3) using the controller to cause the RF receiver circuit to tune to a subsequent frequency in the list of frequencies to be swept;

c4) using the controller to cause the RF receiver circuit to receive a subsequent RF test signal corresponding to the subsequent frequency and obtain a subsequent RF test signal measurement therefrom;

d2) storing the subsequent RF test signal measurement; and

d3) repeating steps c3, c4, and d2 for each remaining frequency in the list of frequencies to be swept.

16. The method of claim 11 wherein the first RF telemetry signal further includes information identifying a signal type corresponding to each frequency of the list of frequencies to be swept, and wherein step b further comprises storing the signal types corresponding to each of the list of frequencies to be swept.

17. An apparatus for performing a frequency sweep testing a CATV system, the CATV system having a plurality of channels, each channel corresponding to at least one of a plurality of channel frequencies, the plurality of channel frequencies including unused channel frequencies and used channel frequencies, the apparatus comprising:

a) an RF receiver circuit configured to receive RF test signals from the CATV system and first and second RF telemetry signals, the first RF telemetry signal including information identifying a list of frequencies to be swept, said list of frequencies to be swept including unused channel frequencies and used channel frequencies the second RF telemetry signal including information identifying transmitter measurement results, the RF receiver circuit operable to obtain RF test signal measurements from the RF test signals;

b) a controller coupled to the receiver circuit, the controller operable to;

obtain the list of frequencies to be swept from the first RF telemetry signal received by the RF receiver circuit;

cause the RF receiver circuit to obtain RF test signal measurements from corresponding to the plurality of frequencies to be swept;

obtain the RF test signal measurements from the RF receiver circuit;

obtain the transmitter measurement results from the second RF telemetry signal received by the RF receiver circuit; and

compare the transmitter measurement results to the RF test signal measurements to obtain test results.

18. The apparatus of claim 17 wherein the RF receiver circuit comprises:

a plurality of mixers;

a signal level measurement circuit operably coupled to at least one of the plurality of mixers, the signal level measurement circuit further operably coupled to the controller; and

a digital demodulator circuit operably coupled to at least one of the plurality of mixers, the digital demodulator circuit further operably coupled to the controller.

19. The apparatus of claim 18 wherein the signal level measurement circuit comprises a signal detector and an analog to digital converter.

20. The apparatus of claim 19 wherein the digital demodulator comprises an FSK demodulator and a manchester decoder.

21. The apparatus of claim 18 wherein the digital demodulator comprises an FSK demodulator and a manchester decoder.

22. The apparatus of claim 17 further comprising a display for displaying information representative of the test results.