DE936990C - Circuit arrangement for tube amplifier - Google Patents

Description

It is known that a certain distribution of the damping within a prescribed range for a wave screen To achieve the frequency range that the sieve from differently tuned resonance circuits is built up and the losses of those resonance circuits are artificially increased, the current or Have voltage maximum at the frequency points where the attenuation should be high. The different tuned resonance circuits are all connected in parallel to each other in the known case, see above that in addition to the resonance elements of the individual circles, the elements of different circles with one another can come into resonance. There are also differently tuned circuits in another known circuit Resonance circles all parallel or in series with one another, and therefore there can also be resonances occur between the elements of different circles.

Tube amplifiers are also already known in which there is a resonance circuit between the individual tubes and these circles are tuned to different frequencies distributed over the band to be transmitted are. The invention, which deals with the problem, is based on such tube amplifiers predetermined width of the frequency band to be amplified over the entire band at least approximately constant gain as high as possible - as an independent variable for the To achieve this desired uniform amplification, the resonance frequencies of the various

which circles and their attenuations are available. There was initially the assumption that to achieve the desired straight-line frequency curve the distances between the individual resonance frequencies are the same and the attenuation of the resonance circles also have to choose the same size. At most, it might have been expected that the optimal one would have been Frequency spacing and the optimal attenuation within the band to be amplified from smaller to ίο must steadily increase or decrease towards higher frequencies.

The invention is based on the knowledge that a constant gain is rather obtained can, if you can either change the spacing of each Resonance frequencies and / or their attenuation against the upper and lower limit of the transmitted Frequency band can decrease in a certain way. According to the invention, the distances are determined of the resonance frequencies and the attenuation of the resonance circles according to those derived below Formulas (11) and (12). For avoiding the The resonance between the elements of different circles is the separation of the individual circles important by means of the amplifier tubes lying between them, through which the circles are decoupled from one another will. This decoupling enables the computational determination shown below the resonance distances and the attenuation of the resonance circuits, creating an amplifier is created, which is extremely constant over its entire frequency range Has gain curve. Compared to an amplifier with resistor capacitor coupling between the individual tubes and opposite an amplifier, in which there is between the individual amplifier tubes equally tuned resonance circuits are located, the amplifier according to the invention has the advantage that with a given bandwidth of the frequency band to be transmitted, the gain for each tube stage is constant is, while it is with an amplifier with identically tuned individual circuits with an increasing number of stages decreases. . . '

Fig. 1, obtained by calculation, gives an approximate idea of the most favorable conditions, in which the resonance curve amplitude for the most favorable position of the resonance curves R ₁ to R _{6 of} the individual circles determined in a certain case is drawn over a normal linear scale for the frequency f and the associated attenuations are at the same time indicated at least qualitatively by the height of the individual resonance maxima. The curve V indicates the course of the gain factor in this position of the individual curves. The result obtained is extremely surprising insofar as the moving closer together of the resonance maxima towards the two ends and the simultaneous decrease in attenuation of the corresponding circles were not to be expected.

The technical subject of the invention Rule, the spacing of the resonance frequencies and / or the attenuation of the resonance circuits according to to decrease the two ends of the frequency band to be transmitted, is still intended in the following are illustrated by means of drawings, in which a logarithmic division for the frequency axis is used. Such a logarithmic scale has the advantage that the resonance curves run symmetrically to their resonance frequency and their shape remains the same with the same damping, regardless of the level of the resonance frequency.

The case shown in Fig. 1 appears when using a logarithmic scale for the frequency axis and also a logarithmic scale for the ordinate axis as shown in Fig. 2. The width b of the band to be reinforced is the area at the limits of which the curve, V drops to an amount of 0.7. The associated attenuations d are indicated on the individual curves R ₁ to R, - .

On the basis of Fig. 3 it should first be demonstrated that, with the same attenuation for the individual resonance circles, the spacing of the resonance frequencies towards the ends of the band to be transmitted must be reduced in order to obtain an approximately constant gain factor. It should be noted that the gain factor for a single frequency lying within the band to be transmitted is proportional to the product of the amplitudes which all the individual resonance curves have at this SteEe. If, for example, one compares the product of all resonance curve amplitudes at frequency f ₂ and the corresponding product at frequency f _x , one can see that as f ₂ ■ progresses to f _x, five resonance curves, namely curves R ₂ to R ₆ , decrease, while only the resonance curve R ₁ increases. So that the gain factor at the frequency f _x has approximately the same value as at the frequency f ₂ , the increase in the amplitude of the curve R ₁ must approximately compensate for the decrease in the amplitudes of the curves A ₂ to R _6. If one the other hand, with respect to the amplitude of products at the frequencies f ₃ and f ₂ is the same view hires when f so the product of all the resonance curve amplitudes at the frequencies ₃ and f ₂ compares with each other, it is seen that, between f _a and f _2, only the four Curves R ₃ to R ₆ decrease (compared to the five curves R ₂ to R ₆ between f ₂ and f _a ), while two curves increase, namely R ₁ and R ₂ (compared to the one curve R ₁ between f ₂ and f _x ) . So that the amplitude product at frequency f ₂ again has approximately the same value as at frequency f ₃ , the decrease in the four curves R ₃ to R ₆ (compared to the five curves R ₂ to R ₆ in the former case) must be due to the increase in two curves Ji ₁ and R ₂ (compared to the one curve R ₁ in the former case) are at least approximately compensated. This already shows that the maximum of R ₂ , ie the frequency f ₂ , may be further away from f _s than the frequency f _{x is} from the frequency f ₂ .

A similar way can be illustrated with reference to FIG that one can also by decreasing damping of the individual resonance circuits after the Ends of the band to be transmitted at the same frequency spacing of the resonance circuits an approximately

constant amplitude product, ie can achieve an approximately constant gain factor within the frequency range to be transmitted. Let us consider the frequencies / V to f ₆ at which the maxima of the resonance curves R ₁ to R ₆ may lie. If one forms the product of the resonance curve amplitudes at the frequency f ₂ and compares it with the corresponding product at the frequency / "/, one can see that between f ₂

ίο and fj_ ' the five curves R ₂ ' to i? ₆ 'decrease, while only one curve A ₁ ' increases. So that at frequency / Ί 'the product of the amplitudes of all curves R ₁ ' to R ₆ again has approximately the same value as at frequency f ₂ , the increase in curve R ₁ ' must correspond to the decrease in all other curves R ₂ ' to R Approximately compensate ₆ '. For this purpose, a certain height of the maximum of R ₁ , the position of which is now supposed to be fixed on the frequency scale, is required. If, on the other hand, the amplitude product at frequency f _{3 is} compared with that at frequency f ₂ , one sees that only the four curves R ₃ ' to R ₆ decrease between f ₃ and f ₂ (compared to the five curves R ₂ to R ₆ ' in the former case), while the two curves R ₁ ' and R ₂ increase (compared to only one curve R ₂ in the former case). In order to obtain approximately the same amplitude product at frequency f ₂ as at frequency f ₃ , the maximum of R ₂ need not be as high as the maximum of R ₁ ' in the case discussed first.

Thus it is proven that with the same attenuation of all circles by decreasing distances of the resonance frequencies towards the ends of the band to be transmitted approximately one constant gain factor over the whole frequency band. It is also proven that with the same spacing of the resonance frequencies by decreasing attenuation of the individual circles after the ends of the to be transmitted Band is also able to achieve an approximately constant gain factor over the get whole band.

Particularly favorable conditions, i.e. a hardly noticeable decrease in the gain factor up to the vicinity of the two band limits, are obtained if both the distances between the resonance maxima and the attenuation of the resonance circles in question decrease towards the ends of the band, i.e. the measurement of frequency distances and selects attenuations that have already been mentioned with reference to Figs. 1 and 2. This can be demonstrated arithmetically in the following way: The course of this calculation is broadly based on first determining an expression for curve V in Fig. 2 as a function of the resonance frequencies and the attenuation of the individual circuits and then by setting it to zero a series of differential quotients of the curve V a number of equations for the resonance frequencies and the attenuation of the individual circles can be obtained, which must be met so that the curve V conforms very well to a horizontal tangent.

Since curve V for each frequency has the ordinate of the product of the ordinates of all individual resonance curves at this frequency, the expressions for the resonance curves must be multiplied with one another. The expression for the ^> th resonance curve (p less than n if η is the number of circles), if L _n , C ₅ , and R ₁ mean the inductance, capacitance and resistance of the ^> th circle and if with d _n a so-called parallel damping, which results from the equation

calculated, designated, is

+ V) ²

here χ is the so-called detuning = -,

where a> _{v is} the angular frequency at the maximum of the relevant resonance curve and ω is the current coordinate of the angular frequency. The entire course of curve V is obtained by calculating for each frequency ω the ordinate values that all curves y _{v have} at this frequency, multiplying all these ordinate values together and plotting them over ω as the ordinate of V.

A not yet mentioned intermediate step must now be inserted into the calculation process outlined above, since in order to be able to carry out the differentiation, an analytical expression for V must first be found as a function of a single variable. A direct multiplication of equations (1) with one another would not yet lead to the goal, since a different resonance frequency co _{n is} used in each of the functions y _n and therefore the product cannot yet be easily differentiated. Rather, a single independent variable must first be introduced, according to which the differentiation can then be made. As this variable, the

Tuning χ - selected, where eo _{0 is} the angular frequency in the middle of the resonance curves drawn on a logarithmic scale, in Fig. 2 ω ₀ is therefore 1 MHz. The current coordinate of the angular frequency is again denoted by ω. The common independent variables are introduced by first forming the product of the resonance curves of two circles each, which on a logarithmic scale _{lie equidistant to the right and left of the frequency ω 0} in the middle of the band and may have the same attenuation. Form the equation (1) introducing the logarithmic coordinates

u = In

CO _n

ν = hi y
um, one obtains the product U of two such

symmetrical to co ₀ Hegenden resonance curves with ordinal numbers φ and q

U = In

- In ² * ² [2 <Z ² -, i ² (2 ■ -

where ^ 4 is the distance between the two resonance frequencies.
One obtains from equation (2)

= In

M ^ iL _1n

? x *

O? x

when used as abbreviations

(3)

V = In

L

J «! C ₉

where (JV ₁ ), (JV ₂ ) etc. are the contents of the bracket in the second term on the right-hand side of equation (3)

means. It is noteworthy that only - such

Members JV occur because equation (3) already includes two resonance curves y _{v symmetrical to co 0.}

If you think of the terms for JV, which are as follows

In [x ²ⁿ

_Y in— 2.

in which C ₁ , C ₂ etc. is each erne constant that contains the values A and d for all circles.

Now the differentiation according to χ can take place, which according to what was said earlier, if one sets the differential quotient equal to zero, the conditions for the

Values A ₁ , A ₂ , ... A _n - and d _lt d ₂ , ... d _n yields the

τ τ

one must choose so that the curve V hugs the horizontal very closely. The computational implementation of the differentiation and zeroing of the differential quotients at the point χ = 0 now shows that all coefficients C ₁ to c _n _ ₁ must vanish. One obtains if one first multiplies the expressions for JV to determine the coefficients c in equation (6)

V = In

and after multiplying and setting the differential quotients to zero, one obtains the equations for the coefficients A ₁ to k _n and then from (4) and (5) ^T

A ² = -

[f

4 +

² - b ² (2

d ² =

4 +

4 +

-δ ² (2

! (11)

(12)

ie the distances and the attenuation of the resonance circuits. The same result is obtained for odd n, that is, odd circle numbers, since after all products U are formed from two circles each, the last circle is yes [A ² + i ² ] 2},

= ^ ² + i ² .

(2)

The curve F for all η circles then results as

Product of all equations (n as an even-numbered

²

suspended) for U too

--In (JV ₁ ) (JV ₂ ) ... (N ^;

N ₁ = x ⁴ + al x ² + dj,

(6)

(7)

multiplied with each other and ordered according to powers of χ , the second term on the right-hand side of (6) has the following form

_-1 x ²

C _n ],

(8th)

System of equations from which one can deduce

1 2 3 ¹ H \ Zf /

The size of these values <5 should be arbitrarily set = b for the time being, so that δ = b . The justification for this in itself arbitrary assumption will be demonstrated further below.

The equality of all values δ means, however, that the amplitudes of all circles at the point ω ₀ are the same if they have the same L : C ratio; because for every two circles at the point x = 0 it is the second

Term in (3) = - γ1η <5 ⁴ . If one sets α ² = k- Ψ, one obtains for the curve V now

(10)

already in the form of equation (1) the detuning λ; and can therefore be excluded from the paired combination. The last circle can rather, go directly into the multiplication of the links JV without reshaping.

The proof that, as was initially arbitrarily assumed above, δ = b can be given if one follows from equation (6) using equation (7) and using

C ₁ = C ₂ = C ₃ = ... c _n _ _t = 0 (13)

the detuning xa _reme for an ordinate value of

Curve V at the band limit of - the maximum

, m

amplitude of V determined. The maximum amphtude

V _max can also be determined from equations (6), (7) and from equation (13), and one then finds that the following equation applies to the detuning χ at the band limit:

Frenze = & (m ² l) * ⁿ .

But this means nothing else than that under the introduction of the assumption m = ] fz already made above, the detuning χ at the band limit has the value b , ie that the arbitrary assumption ö = b introduced above was justified. The arrangement of the switching elements for an amplifier according to the invention is that which is usual for carrier frequency amplifiers and is shown in FIG. 5, for example. There 10 and 11 mean two five-pole tubes from a multi-stage amplifier, in whose anode circles the coils 12 and 13 are located. These coils, together with their parallel capacitances, preferably represent the dotted anode-earth capacitances C ₁₀ and C _11, the resonance circuits will. The terminals 16 and 17 are connected to the positive pole of the anode voltage source, while the grid discharge resistors of the control grid are connected to a negative bias voltage by means of the lines 18, 19.

As already mentioned at the outset, the invention also relates, inter alia, to the amplification of speech streams applicable. The application can be done in different ways; some options are listed below.

a) If, for example, there are eight amplifier stations with four tubes each along a telephone line are, then all thirty-two associated resonance circuits can be different within the meaning of the invention tune and dampen.

b) But you can also use the resonance frequencies of the first sixteen circles over the entire band after the distribute the rules given by the invention and the frequencies in the second sixteen circles choose again in the same way as with the first circles.

c) In this sense, the subdivision of the entire amplifier channel can also be taken further, such that four groups each with eight differently tuned and / or damped resonance circles available. Within each group are the frequencies and / or the attenuations according to FIG Invention graded, and each group is formed in the same way as the others.

d) You can also divide the entire amplifier train into eight groups of four differently coordinated and / or subdivide damped resonance circuits. Even then, within each group are the frequencies and / or the attenuations are graded according to the invention.

e) But you can now also within the invention

in a modification of case d, the first four circles of the first four stations in the first repeater station relocate the second four circles of the first four stations to the second amplifier station, etc. Then So the first station contains louder circles that are the same under each other, the second station louder also under each other same circles, but different from the circles of the first station, etc. first four stations of the whole canal then an embodiment of the inventive idea, since in the first four stations there is a circuit arrangement for tube amplifiers, which on different Frequencies tuned resonance circuits with frequency spacings or selected according to the invention Contains circular losses between the amplifier tubes.

Claims (1)

Claim: Circuit arrangement for tube amplifiers, in which there is a resonance circuit between the individual tubes and these circuits are tuned to different frequencies distributed over the band to be transmitted, characterized in that the distances (A) of the resonance frequencies and the attenuations (d) of the resonance circuits are made up determine the following equations: 4- & ² , (For the meaning of the constants, see description.) Referred publications:
German Patent Nos. 352 445, 631174;
U.S. Patent No. 1,955,788. 1 sheet of drawings φ 509 642 2.56