CATV digital receiver intermodulation susceptibility tester
View Patent ↗A method and apparatus are provided for testing susceptibility of a receiver to intermodulation distortion of a digital channel, the method including selecting a first digital channel from channels in a composite signal, determining a first power measurement from the first digital channel, determining a total power measurement from other channels in the composite signal, and determining susceptibility of the first digital channel to intermodulation distortion by comparing the first power measurement and the total power measurement with intermodulation distortion characteristics of the receiver.
1. A method for testing susceptibility of a receiver to intermodulation distortion of a digital channel, the method comprising:
selecting a first digital channel from a plurality of channels in a composite signal;
determining a first power measurement from said first digital channel;
determining a total power measurement, separate from said first power measurement, from at least one other channel, different from said first digital channel, in said composite signal; and
determining susceptibility of said first digital channel to intermodulation distortion by comparing said first power measurement and said total power measurement, which is separate from said first power measurement, with intermodulation distortion characteristics of said receiver.
2. The method of claim 1 , wherein said receiver comprises a cable television (CATV) receiver.
3. The method of claim 1 , wherein said at least one other channel comprises at least one video channel.
4. The method of claim 1 , wherein at least one of said first power measurement or said total power measurement is determined at an input of said receiver.
5. The method of claim 1 , further comprising determining a level-versus-frequency tilt of said composite signal.
6. The method of claim 5 , wherein said level-versus-frequency tilt of said composite signal is determined at an input of said receiver.
7. The method of claim 5 , further comprising compensating for a differing signal tilt when performing at least one of said first or total power measurements at a location different from a location of said receiver by utilizing said level-versus-frequency tilt.
8. The method of claim 1 , wherein said at least one other channel in said composite signal comprises at least one analog channel.
9. The method of claim 1 , wherein said at least one other channel in said composite signal comprises a plurality of analog channels.
10. The method of claim 1 , further comprising computing a relative power ratio between said first power measurement and said total power measurement.
11. The method of claim 10 , further comprising using said relative power ratio to predict the likelihood that other devices receiving said first digital channel would be impaired by internal intermodulation distortions.
12. The method of claim 1 , further comprising generating a tilt line for a plurality of channels in said composite signal to use as a reference power.
13. The method of claim 12 , further comprising outputting a susceptibility result for said first digital channel in accordance with said reference power so that a same test device will give a same susceptibility result at different points in a network having different tilts.
14. An intermodulation test device for testing susceptibility of a receiver to intermodulation distortion of a digital channel, the device comprising:
a tuner for selecting a first digital channel from a plurality of channels in a composite signal;
a detector in signal communication with the tuner for determining a first power measurement from said first digital channel, and for determining a total power measurement, separate from said first power measurement, from at least one other channel, different from said first digital channel, in said composite signal; and
a controller in signal communication with the detector for determining susceptibility of said first digital channel to intermodulation distortion by comparing said first power measurement and said total power measurement, which is separate from said first power measurement, with intermodulation distortion characteristics of said receiver.
15. The device of claim 14 , further comprising a display in signal communication with the controller for outputting a result indicative of the determined susceptibility of said first digital channel to intermodulation distortion.
16. The device of claim 14 , wherein the controller comprises:
a channel selection unit;
a channel plan unit;
a digital channel measurement unit in signal communication with the channel selection unit and the channel plan unit;
another channel measurement unit in signal communication with the channel plan unit;
an evaluation unit in signal communication with the digital channel measurement unit; and
a results unit in signal communication with the evaluation unit.
17. The device of claim 16 , wherein the evaluation unit is further in signal communication with the other channel measurement unit.
18. The device of claim 16 , further comprising a configurable limit unit in signal communication with the evaluation unit.
19. The device of claim 16 , further comprising a device specification database in signal communication with the evaluation unit.
20. The device of claim 16 , further comprising:
a tilt calculator in signal communication with the other channel measurement unit;
a tilt reference unit in signal communication with the tilt calculator; and
a tilt compensator in signal communication with each of the digital channel measurement unit and the other channel measurement unit,
wherein the evaluation unit is in signal communication with both the digital channel measurement unit and the tilt compensator.