 |
|
|
|
|
|
 Title: |
US4145711:
SECAM modulator
[ Derwent Title ]
|
| Country: |
US United States of America
|
| |
| Inventor: |
Aschwanden, Felix; Thalwil, Switzerland
|
| Assignee: |
RCA Corporation, New York, NY
other patents from RCA CORPORATION (466175) (approx. 7,929)
News, Profiles, Stocks and More about this company
|
| Published / Filed: |
1979-03-20
/ 1977-11-15
|
| Application Number: |
US1977000851780
|
| IPC Code: |
Advanced:
H04N 9/85;
H04N 11/18;
Core:
H04N 9/82;
H04N 11/06;
IPC-7:
H04N 9/34;
H04N 9/40;
H04N 9/42;
|
| U.S. Class: |
Current:
348/642;
348/E11.019;
386/E09.044;
Original:
358/014;
|
| Field of Search: |
358/014
|
| Priority Number: |
| 1976-11-15 |
GB1976000047549 |
|
| Abstract: |
Apparatus for forming a color TV signal of a SECAM type from a pair of correlated color-difference signals (R-Y; B-Y) includes a pair of transistors disposed in a differential amplifier configuration, with a constant current source coupled to interconnected emitters, and a load impedance coupled to one collector. Pre-emphasized B-Y signal is applied to first transistor base during alternate line scanning intervals; pre-emphasized R-Y signal is applied to second transistor base during intervening line scanning intervals. Electronic switches control bias application to transistor bases so that (a) during horizontal sync intervals bases are equally biased; (b) during alternate line scanning intervals (and preceding "backporch" intervals) base bias of second transistor is elevated relative to the first; and (c) during intervening line scanning intervals (and preceding "backporch" intervals) base bias of first transistor is elevated relative to the second. During alternate line interval segments of terminal portion of vertical blanking interval, base bias of first transistor is initially held at abovementioned elevated level relative to the second and then allowed to gradually rise still higher; during the intervening line interval segments, similar control of base bias of second transistor is effected. VCO responds to changes in voltage drop across load impedance by varying its output frequency. In several illustrative applications, a synchronizing system using single reference is effective, during initial portion of horizontal sync interval, in adjusting VCO output to reference frequency. During terminal portion of horizontal sync interval, VCO output is shifted to a frequency midway between the two SECAM resting frequencies. In PAL-SECAM transcoder use, reference frequency is PAL subcarrier frequency; in video disc player use, reference frequency is subcarrier frequency of transcoded composite signal of NTSC-like form.
|
| Attorney, Agent or Firm: |
Whitacre, Eugene M. ;
Meagher, William H. ;
|
| Primary / Asst. Examiners: |
Richardson, Robert L.;
|
| INPADOC Legal Status: |
Show legal status actions
Family Legal Status Report
|
| Family: |
Show 5 known family members
|
First Claim:
Show all 21 claims |
What is claimed is:
1. Apparatus for forming a color television signal of the SECAM type from correlated signals inclusive of a first color-difference signal and a second color-difference signal, said apparatus including:
- a controlled oscillator providing an output comprising oscillations of a frequency subject to variation in accordance with a voltage applied to a modulating signal input terminal thereof;
- first and second transistors, each having respective base, emitter and collector electrodes;
- a substantially constant current source coupled in common to the emitter electrodes of both of said first and second transistors;
- a load impedance coupled to the collector electrode of said second transistor;
- first switch means for selectively enabling and disabling the application of said first color-difference signal to said base electrode of said first transistor;
- second switch means for selectively enabling and disabling the application of said second color-difference signal to said base electrode of said second transistor;
- third switch means for controlling the magnitude of a bias potential applied to said base electrode of said first transistor;
- fourth switch means for controlling the magnitude of a bias potential applied to said base electrode of said second transistor;
- first switch control means coupled to said first and second switch means for causing the enablement of said first color-difference signal application only during alternate ones of a succession of line scanning intervals, and the enablement of said second-color-difference signal application only during line scanning intervals intervening between said alternate ones;
- second switch control means coupled to said third and fourth switch means for causing the bias potential magnitude applied to the base electrode of one of said first and second transistors to exceed the bias potential magnitude applied to the base electrode of the other of said first and second transistors during said alternate ones of said succession of line scanning intervals, and for causing the bias potential magnitude applied to the base electrode of said other transistor to exceed the bias potential magnitude applied to said one transistor during said intervening ones of said succession of line scanning intervals; and
- means for causing the voltage applied to the modulating signal input terminal of said controlled oscillator to follow variations in the voltage drop across said load impedance.
|
| Background / Summary: |
Show background / summary
|
| Drawing Descriptions: |
Show drawing descriptions
|
| Description: |
Show description
|
| Forward References: |
Show 2 U.S. patent(s) that reference this one
|
Nominate this for the Gallery...
