Elias J Livaditis

US Patent:

41018370, Jul 18, 1978

Filed:

May 11, 1977

Appl. No.:

5/795991

Inventors:

Lorimer Clayton - Stone Mountain GA
Elias J. Livaditis - Tucker GA

Assignee:

Scientific-Atlanta, Inc. - Atlanta GA

International Classification:

H04B 110
H04N 544
H03D 300

US Classification:

325347

Abstract:

A tunable oscillating limiter threshold extension demodulator capable of demodulating video and other wide band width FM signals is described. A steering signal is generated to tune the oscillating limiter in response to the video output signals from an FM discriminator to which input signals from the oscillating limiter are applied. The steering signal is generated so as to be in proper phase relationship to track the frequency of the FM signal for modulating frequencies within certain critical regions and is reduced in amplitude over another region where proper phase relationship is not achievable because of unavoidable delays in the system. The steering signal generating circuit may be provided by a filter having a phase response characteristic such that the total phase lag of the system is small at the low frequency end of the band width and about 360. degree. at the high frequency end of the band width. The filter presents substantial attenuation (in the form of a notch) in the frequency region of the band width where the phase delay may be about 180. degree.