In-service CATV HUM measurement technique
US5394185A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 8, 1993 |
| Grant date | Feb 28, 1995 |
| Priority date | — |
| Expiry date | Jan 8, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N17/00
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An in-service hum and low frequency distortion measurement technique for in-service cable television channels having a video modulated carrier frequency obtains peak samples of the horizontal sync signal to effectively filter out the vertical interval frequency. The data record formed by the peak samples is filtered and input to a fast Fourier transform to obtain magnitude values for the fundamental and first harmonic frequency components corresponding to a powerline. From these magnitude values hum and low frequency distortion is computed as a percentage relative to the amplitude of the carrier frequency. The same procedure may be used with an input CW signal in an out-of-service measurement for hum only, the difference between the in-service and out-of-service measurements determining the low frequency distortion due to the video signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.