US2241919A - Method of segregating synchronization impulses - Google Patents

Description

May 13, 1941. P. NEIDHARDT 2,241,919

METHOD OF SEGREGATING SYNCHRONIZATION IMPULSES Filed Feb. 16, 1939 Patented May 13, 1941 METHOD OF SEGREGATING SYNCHRONIZA- TION IMPULSES Peter Neidhardt, Berlin, Germany, assignor to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof,

Germany Application February 16, 1939, Serial No. 256,749 In Germany February 16, 1938 2 Claims.

This invention relates to methods of and means for segregating synchronization impulses, particularly in a television system for controlling the time base devices thereof.

It is a necessary requirement in the transmission of television image impulses to simultaneously transmit synchronization impulses which in the receiving equipment control the image reproduction in the line scanning direction as Well as in the image scanning direction.

The synchronization impulses thus incoming to a receiving equipment may be segregated in filter devices which select the synchronizing impulse frequency components of the frequency mixture received. It is a well known expedient to employ impulses of shorter duration for synchronizing the line scanning, while longer impulses of lower frequency serve to control the framing oscillations. These impulses of different duration are segregated by means of a filtering device which merely permits the alternating frequency to pass which corresponds to the number of the framing impulses and to the number of line impulses, respectively. However, the use of such filtering devices for segregating the line and frame scanning synchronizing impulses introduces the disadvantage that the wave front of the image change synchronization impulses does not present the desired steepness.

It is the main object of my invention to eliminate the above mentioned drawback. According to the main feature thereof, there is provided an additional circuit element to which the framing frequency impulses are applied and by means of which the wave front steepness is improved so as to obtain the desired shape.

The invention will be more readily understood from the followin description taken in conjunction with the accompanying drawing, in which Fig. 1 diagrammatically shows synchronization impulses of diiferent kind, as employed in television systems, while Fig. 2 schematically shows an arrangement according to my invention.

The upper part a of Fig. 1 diagrammatically shows the different synchronization impulses used in television transmitting systems. The short impulses which effect the line synchronization are shown at A, while a framing frequency impulse of longer duration is shown at B. The flattened wave fronts of this impulse depend upon the fact that the current characteristic of rectangular shape contains a plurality of sinusoidal currents according to the law of Fourier. The currents of higher frequency in this frequency mixture which currents define the frequency steepness do not pass the filter tuned to the line frequency since these frequencies correspond to the frequency components of the line synchronizing impulses of short duration. This flattening of the rectangular wave front considerably affects the exact control of the framing frequency time base circuit.

With reference to the above mentioned conditions it will easily be understood that a steep wave front of the image change synchronization pulses is desired. This requirement is fulfilled according to the main feature of my invention by the provision of a particular transformer having an easily saturable member interposed in its magnetic circuit.

The Fig. 2 of the accompanying drawing shows one embodiment of such a transformer device. The image change synchronizing pulses derived from the filtering device 1 are applied across the winding I of the transformer 2. The secondary winding of this transformer is divided into two parts II and III. The winding II is arranged on the portion of the transformer iron core which is to be saturated. An impulse of the configuration shown at B in Fig. 1 which impulse is applied across the winding I of the said transformer becomes induced in the windings III in substantially it original shape, while pulses shown in the lower part of the Fig. 1 are induced in the winding II of the transformer. The sum of these impulses thus induced in the two secondaries of the transformer involves an impulse of the shape as indicated in the upper part a of Fig. 1 by the dashed line, and this pulse which now has the desired wave front steepness is employed for controlling the framing frequency time base circuit 3.

The above described arrangement is by no means limited to the utilization of the magnetic saturation effect, but is applicable to all arrangements and devices where it is desired to improve the steepness of the wave front of impulses applied thereto.

What is claimed is:

1. A transformer device for improving the wave front steepness of television framing frequency synchronization impulses, comprising a core having an unsaturable portion and a saturable portion, a primary winding for receiving said synchronizing impulses, a first secondary on said unsaturable portion of said core, and a second secondary winding on the saturable portion of said core and connected in series with said first secondary winding said serially connected secondary windings servin as the output of said device.

2. In a television receiving equipment, means receiving image synchronizing impulses of different frequencies, means responsive to the higher of said diITer-ent frequencies for synchronizing the line scanning, means responsive to the lower of said different frequencies for synchronizing the framing frequency oscillations, means to segregate and to apply said synchronization impulses of difierent frequencies to the respective responsive means, and a transformer device to improve the wave front steepness of the framing frequency synchronization impulses, said transformer comprising a primary winding connected across said segregating means, an iron core for said transformer having an unsaturable portion and a saturable portion, a first secondary winding on said unsaturable portion of said iron core and a second secondary winding on the saturable portion of said iron core and connected in series with said first secondary winding, the serially related secondary windings being connected with said lower frequency responsive means.

PETER NEIDHARDT.

Images