| | Method of and device for measuring echo parameters on telephone lines - Patent 6501830 |
 | | A signal having lenticular envelope is used as test signal and is generated preferably starting from a first sinusoid with a first given frequency modulated in amplitude with a second sinusoid having a second given frequency, lower than the aforesaid first given frequency. |
 | | The width of the window must preferably be a multiple of half the period of the sinusoid, and in phase therewith, in order to limit the harmonic content originated by the signal fronts. |
 | | This type of detection can suffer, when sinusoidal signals are used, from inaccuracies stemming from the fact that the difference in amplitude between adjacent peaks in the received signal, even if minimal, can cause a time offset of the determined arrival instant. |
| www.freepatentsonline.com /6501830.html (3536 words) |