 Noise reducing apparatus and methods for television receivers |
| The invention is embodied in a principal one of its aspects in a television system including a ... |
|
| Method of forming halftone screen |
| It is a primary object of the present invention to provide a method of forming a halftone screen to ... |
|
| Marking engine and method to optimize tone levels in a digital output system |
| In accordance with the present invention, a halftone cell configuration of a plurality of output ... |
|
| Multi-level error diffusion apparatus and method of using same |
| A multi-level error diffusion system includes a processor that creates an m by n super pixel cell ... |
|
| Image recording apparatus |
| To overcome the abovementioned drawbacks in conventional image-recording apparatus, it is an object ... |
|
| Television receiver that controls display contrast based on the type of videos being displayed |
| It is, therefore, an object of the present invention to provide a television receiver capable of ... |
|
| Architecture with centralized single memory for the transfer of video images |
| The present invention relates to an architecture making it possible to store and transfer still or ... |
|
|
Transmission system comprising receiver with improved timing means
| Details |
Inventors: Bergmans, Johannes W. M.;
Assignee: U.S. Philips Corporation (New York, NY)
Primary Examiner: Chin; Stephen
Assistant Examiner: Bocure; Tesfaldet
Attorney, Agent or Firm: Eason; Leroy
A data transmission system wherein the data symbols to be transmitted are divided into two groups, for example odd and even, and each data symbol in one group is represented by a signal element which differs from the signal element used to represent each data symbol in the other group. An example of such encoding is the quadra-phase code. The transmitted signal is a summation of the signal elements of both groups. At the receiver the received signal is sampled at a first and a second sampling instant for every two successive signal elements, and from the sample values decisions are made as to the symbol values represented thereby. This requires that the sampling instants accurately correspond to the two groups of signal elements. To achieve such timing control the receiver includes a phase detector for deriving an error signal representing deviation between actual and correct sampling instants, and the actual sampling instants are adapted to minimize the error signal. The error signal is based on a correlation between the values of samples at the sampling instants and expected values thereof at such instants. |
|
DETAILED DESCRIPTION It is an object of the invention to provide a system as defined in the opening paragraph in which the clock recovery system produces a clock signal having reduced phase jitter without the tracking rate of the clock recovery system being detrimentally affected.
For this purpose the invention is characterized, in that the timing means comprise means for determining a timing error signal which depends on the correlation between a second sample value and an expected first sample value, the timing means further including adjusting means for adjusting the sampling instants in response to the timing error signal.
As a result of these characteristic features a control loop is created which minimizes the timing error signal, which is a measure of the difference between the sampling instants and the reference instants.
Hereinbelow it will be explained why the timing error signal is really a measure of the difference between the sampling instants and the reference instants.
The input signal of the receiver is assumed to be the same as the Quadra-Phase signal transmitted by the transmitter.
Generally, however, the transmitted Quadra-Phase signal will be a square-wave signal, but as a result of the filtering effected in the channel and equalizing means, if any, the signal at the input of the receiver is an analog signal which is capable of adopting with time any value in a specific interval.
At a specific instant t (2iT.
ltoreq.
t<2iT+2T) the following holds for the first and second signal elements s.
sub.
1, s.
sub.
2 and the resulting quadra-Phase input pulse s.
sub.
c of the receiver: ##EQU1## Herein a.
sub.
2i-1, and a.
sub.
2i are two successive data symbols from a sequence of data symbols, t is time and T is the mean time period between successive data symbols.
It is assumed that Kth data symbol a.
sub.
k in the sequence can adopt any of the values -(M-1), -(M-3), .
.
.
, -1, +1, .
.
.
, +(M-3), +(M-1) if the number M of possible symbol values is even.
If the number M of symbol values is odd, a
|
| Related patents |
|
|
Method and apparatus for context sensitive post processing to select an appropriate modulation pattern for a pixel based upon neighboring pixels
In the system and method in accordance with the preferred embodiment of the present invention, a pixel map sends a multibit representation of the output pixel data for a ...
|
|
|
Apparatus and method for arbitrary binary resolution conversion
OF THE PRESENT INVENTION The following will be a detailed description of the drawings illustrating the present invention. In this description, as well as in the ...
|
|
|
Systems and methods for template matching of multicolored images
Accordingly, when tasks such as resolution conversion, restoration, appearance tuning and descreening are performed on monochrome or color images, a filter is often ...
|
|
|
Compact rendering for processing binary high addressability images
In accordance with the present invention, there is provided a method of processing a high addressability binary image comprises converting the high addressability binary ...
|
|
|
Method of improving a digital image as a function of its dynamic range
Accordingly, it is an object of the present invention to provide a method of improving an image created with digital data for both color and non-color images. Another ...
|
|
|
Video noise reduction system
The present invention has application in the field of film to video tape conversation, but works in conjunction with any video signal from which it is desired to reduce ...
|
|
|
Automatic gain control system for a high definition television signal receiver including an adaptive equalizer
FIG. 1 illustrates a portion of a high definition television (HDTV) receiver for receiving and digitally processing an HDTV signal of the type shown in FIG. 2. This ...
|
|
|
Television scan line doubler including temporal median filter
WITH OBJECTS A general object of the present invention is to provide an improved method and apparatus for television scan line doubling and display which includes a ...
|
|
|
Fifty channel television transmitter
What is claimed is: 1. A device that simultaneously transmits a plurality of television channels, comprising; a local oscillator that generates a predetermined frequency;...
|
|
|
Apparatus for reducing artifacts in error diffused images
What is claimed is: 1. Apparatus for a recursive spatial filter which eliminates visible grain patterns from bilevel digital images, said apparatus comprising: means, ...
|
|
|
Image Analysis 
