CATV frequency sweep testing using RF transmitter to generate test signals

• US 5,867,206 A
• Filed: 08/06/1996
• Issued: 02/02/1999
• Est. Priority Date: 09/19/1994
• Status: Expired due to Term

• Current Assignee: Wavetek Corp. (Lumentum Holdings Inc.)
• Original Assignee: Wavetek Corp. (Lumentum Holdings Inc.)
• Inventors: Chappell, Daniel K., Voght, Timothy R.
• Primary Examiner(s): Grant, Chris
• Application Number:
  US08/693,018
• Time in Patent Office: 910 Days
• Field of Search: 348/6, 348/12, 348/13, 348/192, 348/193, 455/3.1, 455/6.1, 455/6.2, 455/6.3
• 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
• 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 signals 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 used 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 signals 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 sweeping 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 transmitter for generating and transmitting test signals at one or more of the plurality of the channel frequencies over the CATV system;

b) a processor coupled to the RF transmitter, the processor operable to index through a list of a plurality of channels to be swept, and cause the RF transmitter to generate and transmit a test signal at each unused channel frequency, and

c) means for coupling the RF transmitter to the CATV system.

2. The apparatus of claim 1 wherein the RF transmitter further comprises:

a mixer having a local oscillator input and an output;

a voltage controlled oscillator connected to the local oscillator input, said voltage controlled oscillator operable to generate a local oscillator signal; and

wherein the processor, for each test signal to be generated, operably controls the voltage controlled oscillator to cause the voltage controlled oscillator to generate the local oscillator signal at a select frequency corresponding to the channel frequency at which the test signal is to be generated.

3. The apparatus of claim 2 wherein the mixer further includes an IF input and wherein the mixer is operable to mix an IF signal provided at the IF input with the local oscillator signal provided at the local oscillator input in order to produce the test signal at the channel frequency.

4. The apparatus of claim 1 wherein the processor comprises a microprocessor and display unit.

5. The apparatus of claim 1 wherein the processor is further operable to cause the RF transmitter not to transmit a test signal for each used channel frequency.

6. An apparatus for frequency sweeping 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 designed for use in conjunction with a receiving test unit, the apparatus comprising:

a) an RF transmitter for generating and transmitting test signals at one or more of the plurality of the channel frequencies over the CATV system;

b) a processor coupled to the RF transmitter, the processor operable to index through a list of a plurality of channels to be swept, and cause the RF transmitter to generate and transmit a test signal at each unused channel frequency, said test signal transmitted over the CATV system and received by the receiving test unit;

c) means for receiving each test signal generated by the RF transmitter and determining one or more characteristics of the test signal, and for generating data representative of the one or more characteristics to the processor; and

d) means for providing a telemetry signal including the representative data to the receiving test unit in order to allow the receiving test unit to compare the one or more characteristics with the transmitted test signal.

7. The apparatus of claim 6 wherein said means for receiving each test signal and providing data includes

an RF receiver operably coupled to the RF transmitter;

and

a level detector operably connected to the RF receiver, said level detector operable to generate a substantially DC voltage level indicative of a measure of signal strength of the received test signal;

an analog to digital converter connected to said level detector and the processor, the analog to digital converter operable to receive the substantially DC voltage level from the level detector and generate the representative data from the substantially DC voltage level.

8. The apparatus of claim 7 wherein said level detector comprises a peak detector.

9. The apparatus of claim 6 wherein the RF transmitter further includes:

a mixer having a local oscillator input and an output;

a voltage controlled oscillator connected to the local oscillator input, said voltage controlled oscillator operable to generate an a local oscillator signal; and

wherein the processor, for each test signal to be generated, operably controls the voltage controlled oscillator to cause the voltage controlled oscillator to generate the local oscillator signal at a select frequency corresponding to the channel frequency at which the test signal is to be generated.

10. The apparatus of claim 9 wherein the means for receiving each test signal and generating representative data therefrom includes at least a first mixer, the first mixer being operably connected to the voltage controlled oscillator of the RF transmitter.

11. The apparatus of claim 6 wherein the RF transmitter further includes at least one oscillator, the means for receiving each test signal and generating representative data therefrom further includes said at least one oscillator, said at least one oscillator being shared with the RF transmitter.

12. The apparatus of claim 6 wherein the means for providing the telemetry signal to the receiving test unit comprises the RF transmitter and means for modulating the telemetry signal onto an RF signal generated by the RF transmitter.

13. The apparatus of claim 12 wherein the means for modulating includes a Manchester encoder operably connected between the processor and the RF transmitter.

14. The apparatus of claim 6 wherein the processor is further operable to cause the RF transmitter not to transmit a test signal for each used channel frequency.

15. The apparatus of claim 14 wherein the means for receiving each test signal and generating representative data therefrom is further operable to:

receive a television signal on each used channel frequency;

generate data representative of one or more characteristics of the television signal; and

provide the representative data to the processor.

16. A An apparatus for frequency sweeping 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 designed for use in conjunction with a receiving test unit, the apparatus comprising:

a) an RF transmitter for generating and transmitting test signals at one or more of the plurality of the channel frequencies over the CATV system to the receiving test unit, and for transmitting telemetry signals over the CATV system to the receiving test unit;

b) a controller coupled to the RF transmitter, the controller operable to index through a list of a plurality of channels to be swept, cause the RF transmitter to generate and transmit a test signal on a plurality of channel frequencies, said test signal transmitted over the CATV system and received by the receiving test unit, and

cause the RF transmitter to transmit a telemetry signal to the receiving test unit, said telemetry signal including information pertaining to transmitted test signals.

17. The apparatus of claim 16 further comprising:

c) means for receiving each test signal generated by the RF transmitter and determining one or more characteristics of the test signal; and

d) means for generating the telemetry signal using the one or more characteristics of the test signal.

18. The apparatus of claim 16 wherein the processor is further operable to cause the RF transmitter to generate and transmit a test signal only on each unused channel frequency.

19. The apparatus of claim 18 wherein the processor is further operable to cause the RF transmitter not to transmit a test signal at each used channel frequency.

20. The apparatus of claim 19 wherein the processor is further operable to cause the RF transmitter to transmit a telemetry signal to the receiving test unit, the telemetry signal including information pertaining to existing signals on the used channel frequencies.

21. The apparatus of claim 16 wherein the controller comprises a microprocessor.