US2195095A - High frequency amplifying arrangement for a very broad frequency band - Google Patents

Description

' H. RlNlA March 26, 1940.

HIGH FREQUENCY AMPLIFYING ARRANGEMENT FOR A VERY BROAD FREQUENCY BAND Filed oct. 28, 1936 INVENTOR HEJRRE RINIA BY l /wv-r/L ATTORNEY say 4000 kilocycles sec; such as are used, inter Patented Mar. 26, 1940 UNITED STATES HIGH FREQUENCY AIWPLIFYING ARRANGE- MENT FOR A BAND VERY BROAD. FREQUENCY HerreRinia, Eindhoven, Netherlands, assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application October 28, 1936, Serial No. 107,931

In Germany November 11, 1935 y 3- Claims.

This invention relates to a high frequency amplifying arrangement which allows the passage of a very broad frequency band having a width of alia, in television. I

When an alternating voltage is set up between the control grid and the cathode of an amplifying tube, whose anode circuit comprises a tuned oscillatory circuit, the voltages occurring through this oscillatory circuit being supplied to a succeeding amplifying stage, then the amplification of such an arrangement greatly depends'on the frequency. A comparatively narrow frequency band is allowed to pass highly amplified, whereas the amplification is low for all of the other frequencies.

As is well-known, a fiat course of the ire.- quency characteristic curve'of such an amplifier can be ensured by connecting a damping resistance in-parallel with the oscillatory circuit.

According as to whether the. circuit is more damped, the frequency band passing through it will" be broader, the amplification decreasing, however, at the same time.

According to the invention, a flat course of the frequency characteristic (uniform amplification for a large frequency spectrum) is ensured in a high frequency amplifying arrangement, in which the anode circuit of one or more amplifying tubes comprises a tuned oscillatory circuit (primary circuit) coupled with a second tuned oscillatory circuit (secondary circuit), by deriving the amplified oscillations from the primary circuit, the primary circuit being slightly and the secondary circuit being strongly damped.

The invention will be more clearly understood by references to the accompanying drawing in which:

. Fig. 1 shows a circuitarrangement of a series connection and a self-inductance, a capacity, and a. dampingre'sistance connected in parallel with a primary circuit;

Fig. 2 represents a circuit arrangement in which the oscillatory circuits are coupled by a V capacitive coupling;

Fig. 3 shows a circuit arrangement in which the two oscillatorycircuits are coupled induc-v tively;

Fig. 4 indicates the damping of the secondary circuit, by means of a resistance connected in parallel to. thev secondary circuit;

Fig. 5 shows a third. tuned osc1llatory circuit connected in parallel with part of the secondary circuit, the third circuit being connected in parallel with a damping resistance; and

6 shows a third tuned. oscillatory circuit Fig. connected in parallel with part of the secondary circuit, the third circuit being connected in parallel with the series connection of a selfinductance and a capacity. I

Fig.1 shows a circuit arrangement in which a series-connection of a self-inductance L2, a capacity C2 and a damping resistance R2 is connected in parallel with the primary circuit Ll, C1, the two circuits L1, C1 and L2, C2, B2, Ci'being very tightly coupled.

Theoperation of this circuit arrangement may be explained as follows. When the reaction of the anode of the amplifying tube may be neglected, the amplification of such a circuit arif the damping of the primary circuit 1 is neglected.

For this equation Supposing thatL1C1 and L202 have been made equal, and

Substituting these values, we findz This means that the amplification at the frequency w amounts to:

whereas for the resonance frequency we get the amplification Vu=SR2.

Thus, we find:

cases for securing the passage of a broader frequency band or a stronger amplification.

Fig. 2 represents a circuit arrangement in which the oscillatory circuits are coupled by a capacitative coupling, the damping of the secondary circuit being brought about by connecting a resistance R2 in series with the self-inductance of this circuit.

Fig. 3 shows a circuit arrangement in which the two oscillatory circuits are coupled inductively, the damping of the secondary circuitbeing brought about with the aid of a series resistance R2 as is also the case in the above-mentioned arrangements.

In the circuit arrangement represented in Fig. 4' damping of the secondary circuit is ensured by means of a resistance R2 connected in parallel with this circuit. If it is found that when such a parallel-connected damping resistance is used the coupling between the two' oscillatory circuits is purely capacitative or purely inductive, an asymmetrical frequency characteristic is obtained. A symmetrical frequency characteristic is achieved by coupling the two oscillatory circuits both capacitatively and inductively, the capacitative coupling being equal to the inductive coupling.

The equations for the circuit arrangements represented in Figs. 2, 3 and 4 are similar to those referred to above for the arrangement shown in Fig. 1.

When an amplifying arrangement according to the invention is used for television purposes, it is desirable that the frequency characteristic should have a flat course and in addition that for any frequency the phase-displacement brought about by the amplifier should be proportional to the difference between this frequency and the frequency of the carrier wave,

since otherwisedeformation of the picture occurs. Consequently, the amplifying V arrangement should satisfy the condition that the ratio 9 /2 is constant throughout the frequency range, where (p represents the phase displacement.

The arrangements according to the invention permit this latter condition to be satisfied over a large range of frequencies.

A further improvement of the course of the frequency characteristic can be obtained by using the arrangements shown in Figs. 5 and 6, in which a third tuned oscillatory circuit is connected in parallel with part of the secondary circuit. In Fig. 5, this third circuit La, C3 is connected in parallel with the damping resistance R2, whereas in Fig. 6, the third circuit is connected in parallel with the series-connection of the self-inductance L2 and the capacity C2. In calculating Viv/V0 for the arrangements represented in Figs. 5 and 6, we find the equation:

'In these arrangements, a fiat course of the frequency characteristic is ensured by at least approximately making a1=az and b1==b2, whereas 02 should be as small as possible.

What is claimed is:

1. A circuit arrangement for amplifying high frequency electrical oscillations comprising a vacuum tube having an anode circuit, said circuit comprising a tuned oscillating circuit, an output circuit connectedthereto, a strongly damped tuned circuit in a mutual inductive relationship with said first tuned circuit and capacitatively coupled thereto, the inductive coupling being equal in magnitude to the capacitative coupling.

2.A circuit arrangement for amplifying high frequency electrical oscillations comprising a vacuum tube having an anode circuit, said circuit comprising a tuned oscillating circuit, an output circuit connected thereto, a strongly damped tuned circuit in' a mutual inductive. relationship with said first tuned circuit and means for capacitatively coupling'said circuits comprising a condenser between said circuits, the inductive coupling being. equal in magnitude to the capacitative coupling.

3. A circuit arrangement for amplifying high frequency electrical oscillations comprising a vacuum tube having an anode circuit, said circuit comprising a tuned oscillating circuit, an

output circuit connected thereto, a second tuned circuittin a mutual inductive relationship with said first circuit and capacitatively coupled thereto, the inductive coupling being equal in magnitude to the capacitative coupling, and means for damping said second tuned circuit comprising a resistance connected across said second tuned circuit.

HERRE RINIA.

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