DE1243716B - Transmitter amplifier for TV picture channels - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

H04n

German class: 21 al -33/20

Number: 1243 716

File number: S 63695 VIII a / 21 al

Filing date: June 30, 1959

Opened on: July 6, 1967

The invention relates to transmitter amplifiers for television picture transmitters with several power tubes controlled by a common exciter will. The input resistance of amplifier tubes, e.g. B. as a transmitter B amplifier in a grid base circuit, is often dependent on the size of the modulation or the degree of modulation of the modulation amplitudes. This fact affects particularly adversely affect the exciter, its transfer function depending on the degree of modulation fluctuates. Therefore, there are differentials between the carrier frequency before and after the amplifiers Phase differences (phase deviation) occur, especially when transmitting television signals result in a poor intercarrier signal-to-noise ratio between the image transmitter and the sound transmitter.

These problems related to the fluctuating input resistance have been eliminated solved that you attached in a suitable manner attenuations in the grid-cathode circuit, which should reduce these disadvantages. However, these measures require significantly more control power.

The invention is based on the object, without additional damping measures, the shortcomings of the to avoid fluctuating input resistance of a transmitter amplifier with several tubes. According to the invention, this object is achieved in that the driving energy of the control transmitter over two lines differing in length by a quarter of a wavelength and therefore with a phase shift of 90 ° from two groups of the same number as B-amplifiers in a basic grid circuit operated power tubes is branched in such a way that their input resistances conjugate are complex to one another and their input resistance fluctuations compensate one another, and that from the branch point a thereby of the different degrees of modulation in black and White screen independent constant load resistance transformed to the output of the exciter will.

It is in itself an arrangement for coupling the outputs of two transmitter output stages of the same type known with a useful resistor, in which the control voltages of the transmitter output stages by 90 ° are out of phase with each other and their outputs with the two input terminals of a push-pull arrangement are connected via conduction paths, the electrical lengths of which by an odd number Multiples of a quarter wavelength are different from one another. However, this arrangement serves Transmitter amplifier for television picture transmitters

Applicant:

Siemens Aktiengesellschaft,
Berlin and Munich,
Munich 2, Witteisbacherplatz 2

Named as inventor:

Dipl.-Ing. Johannes Holle, Berlin-Friedenau

not to avoid the fluctuating input resistance of the power amplifier; the task is there rather, a reflection-free coupling of the outputs "of two identical transmitter output stages with a useful resistor in such a way that essentially all of the transmitter power

so fed to an antenna or another consumer and the reflected energy is completely consumed in an absorption resistor.

With reference to FIG. 1 and 2 the invention is explained in more detail using an exemplary embodiment.

If you have two groups of the same number of amplifiers in parallel operation with fluctuating input resistances, according to the invention it is possible to transform these two resistances in such a way that that the resulting value of the parallel connection is almost constant.

According to Fig. 1, the two transmitter tubes .Rd ₁ and Ro _{2 are} parallel with their inputs. Your input resistances are for example

a) with strong activation (black screen)

= W _S2 = 45 Ohm = -

_S2

b) with weak control (white screen)

^w w =

= W _w2 = 80 ohms = Z ₀

m.

This means that the following relationship exists between the input resistances W _s and W _w:

W =

The characteristic impedance Z _{0 of} the supply cable is 60 ohms. The line from the control transmitter branches from distributor V into a branch line I ₁ to the tube JRo ₁ and a branch line I ₂ to the tube

λ Ro ₂ . The latter is lengthened by a bypass line U ₁ by - ^ (a quarter wavelength of the carrier frequency) compared to I _1.

709 609/305

Claims (2)

According to Fig. 2 (complex resistance level) the resistors Wsl and Ws2 are transformed over the cable lengths Z1 and Z2 = Z1 + - ^ - that W'sl and W12 are complex conjugate to one another. The length of the lines Z1 and Z2 can be adjusted. The parallel connection of W'sl and Ws% in distributor V delivers Ws' = 30.5 ohms. According to FIG. 2, the resistances Ww t and Wws are transformed in the same way over the cable lengths Z1 and L2 = I1 + - ^, so that Wwl and W''z are again complex conjugate to one another. In the distributor one receives again TF, / = 30.5 ohms. For all intermediate values between "black" and "white" one obtains values that deviate even less from ~ - = 30 ohms. Finally, after a transformation in distributor V with ü2 = 2, one obtains an input resistance of the two stages connected in parallel of w; = -W9 '= 61 ohms. The difference in cable lengths Z1 and Z2 is corrected at the output of the amplifier according to the bridges B used (in-phase or 90 ° different feeds) by a further detour line £ /., = -Y. In the case shown, it is a bridge B with in-phase feed, in which a length compensation corresponding to the -j- = 90 ° corresponding to the difference Z1 - Z2 of phase is made V. If more than two power tubes are to be used in the transmitter output stage, several of the twin systems shown in FIG. 1 can be combined to form four-fold, six-fold, etc. systems. Patent claims: 1. An arrangement for eliminating fluctuations in the input resistance of a transmitter output stage of a television picture transmitter consisting of several interconnected power tubes, characterized in that the driving energy of the control transmitter is via two lines (Z ₁ , L ₂ ) which differ in length by a quarter wavelength and thereby with a Phase shift of 90 ° to two groups of equal number of power tubes (Ro ₁ , Rö. ₂ ) operated as B-amplifiers in a grid-based circuit is branched in such a way that their input resistances are complex conjugate and their input resistance fluctuations compensate each other, and that the branching point (V ) a constant load resistance that is independent of the different degrees of modulation in the black and white image is transformed to the output of the exciter. 2. Arrangement according to claim 1, characterized in that several systems consisting of two power tubes (Ro ₁ , _{Ro 2} ) are interconnected to form four-fold, six-fold, etc. systems. Considered publications:
German Patent No. 930 216;
"Wireless World", May 1956, p. 225. 1 sheet of drawings 709 609/305 6.67 © Bundesdruckerei Berlin