SU51945A1 - Method for compensating the upper bend of the modulation characteristic of a modulated high-frequency oscillator - Google Patents

Description

The purpose of the present invention is a method of increasing the efficiency and increasing the nominal power of the lamps of a modulated high-frequency electric oscillation generator, suitable for radiotelephony both in grid modulation or amplification of modulated oscillations, and in anodic modulation, regardless of the modulator circuit used, as well as for the transmission of still and moving images, for radio telegraphy, both tonal and continuous oscillations, etc.

To achieve this goal, the top bend of the modulation characteristic of the high-frequency generator is compensated for. In FIG. G-8 depict curves characterizing the operation of the transmitter, and FIG. 9-11th scheme.

Grid modulation and amplification of modulated oscillations. As is well known, with the usual methods of grid modulation (as well as amplification of modulated oscillations), the static modulation characteristic representing the dependence of the amplitude of the first harmonic of the anodic current (/ о, „1) on the modulating factor (E displacement or excitation and) has bends in the lower and upper parts, due to the nonlinearity of the static characteristics of the lamp.

Without touching the lower bend, to compensate for which a number of more or less satisfactory schemes have been proposed, we will stop in more detail on the reasons for the appearance of the upper bend.

It is clear that the upper bend of the modulation characteristic can occur either when approaching the saturation current of the lamp or as a result of the generator switching to overvoltage mode. The first of these reasons, due to the well-known (with the use of existing schemes) premature limitation of the use of cathode emission by the limiting (allowable) power of the scattering on the anode (especially with powerful generating lamps) is not very likely, and

The flattened shape of the pulses of the anode current provides for obtaining a larger for the same value of the impulse i „j ,,, and, consequently, a larger value of the oscillatory power in the main generator circuit.

The limitation of the growth of A, due to the overpotential of the mode, as can be seen from the foregoing, largely disappears, but along with the growth of the first harmonic of the anode current, it also increases rapidly and is constant at this current.

Such a growth ratio of 1 and / d 1 with the existing modulation methods would cause a very rapid growth of the scatter on the anode, which limits the possibility of increasing /

The proposed method simultaneously eliminates to a significant extent this limitation by the fact that with it the power lost by the generator does not dissipate completely on the anode, as in conventional schemes, but is distributed between the anode and the auxiliary circuit (tuned to the third harmonic), where it is It is in the form of power of oscillations of a threefold frequency. Such an unloading of the anode of the lamp makes it possible to use the lamp by the emission of a cathode much more fully, increasing its nominal power by 40 and more compared to the commonly used methods of grid modulation.

Thus, the first harmonic of the anode current, forced to stop its growth with sup- port modulation methods due to the limiting scattering on the anode or the formation of deep dips in current pulses - in the overvoltage mode, when applying the proposed method has a much greater possibility of linear growth up to full use of the cathode emission of the lamp.

An exemplary view of the modulation characteristic of the generator, obtained by applying the proposed method with grid modulation by offset, is shown in FIG. 4 (curve /), where, for comparison, the modulation characteristic obtained on the same generator with

the usual modulation method of displacement (curve 2).

The above circumstances, in addition to a significant increase in the linear portion of the modulation characteristic, an increase in the nominal power of the lamps, also determine the increase in the efficiency of the modulated cascade due to a higher anodic voltage utilization rate in both the carrier mode and the maximum mode. power. The efficiency is, as usual, taken as the ratio of the useful vibrational power (in this case, the power released in the main circuit) to the total power consumed by the anode circuit of the generator.

Similar results are offered by the proposed method even with amplification of modulated high-frequency oscillations.

In this case, during operation, the amplification of the most common cut-off angle of 8 90 phenomena occurs in the following order:

The first (lower) part of the modulation, the characteristics (as long as the anode current pulses remain pointed) will remain exactly the same as with conventional amplification schemes, since the third harmonic voltage at 0 90 ° and O is zero (see curve / - fig. 1).

As soon as flattenings of the tops begin to appear in the current pulse (at the approach and during the critical mode — where the usual modulation characteristic begins to show a tendency to bend), the third harmonic of the anode current appears and immediately in antiphase with respect to the first harmonic (Fig. 1), and from this moment its compensating action begins, similar to what it was in the modulated cascade (in the upper part of the modulation characteristic). An exemplary view of the resulting modulation characteristic is shown in FIG. 5 (solid line), where for comparison the bending of the modulation characteristic in the upper part is plotted with a dotted line, the total alternating voltage, the nature of which changes its peak values for the latter case (dotted a and a , j) is represented as curve a, plotted in FIG. 1 fat line.

The proposed method is based on the use of the above-described nature of the behavior of the harmonics in various cases, as well as the well-known nature of changing the type of static characteristics of the lamp at low voltages on the anode, for which, in the anode circuit of the modulated oscillator (or, accordingly, the modulated oscillator) with the main oscillating circuit tuned to the fundamental frequency (to the first harmonic of the anode current), an additional loop is included tuned to the third harmonic of the anode current.

With an appropriate selection of the parameters of the circuits and the modulated oscillator mode, depending on the lamp parameters, given power sources, etc., the generator operation in the process of conventional grid modulation by displacement will proceed in the following order:

1) during the part of the negative half-period of the modulating voltage corresponding to the largest negative biases on the grid of the lamps of the modulated oscillator, the lower cut-off angle of the anodic current increases from 0 to some value (about 40-50). The total voltage at the anode load grows at a speed almost two times greater than with a single circuit, since at small b values of a and a are of the same order, due to which the approach to the critical mode of the generator is significantly accelerated.

The dynamic characteristic of the lamps has, as usual, an upward almost rectilinear part, but with a lower slope in accordance with a more intense drop in the residual voltage on the anode.

Anode current pulses have the form of sinusoidal segments without flattening at the top (pointed pulses), varying in duration and magnitude in accordance with the values of displacement and the shape of the dynamic characteristic.

The modulation characteristic in this part is not much different from that obtained with conventional modulation schemes (goes slightly below normal);

2) during the remainder of the negative and total positive half-period of the modulating voltage, which corresponds to the middle and upper part of the modulation characteristic, the total voltage at the anode load ceases to rise and then decreases due to the compensating third harmonic voltage (see Fig. 1-curve a.). In particular cases, the total voltage may remain constant or slowly increase. This nature of the change in the total voltage on the anode load makes the generator work all the time in restimum, close to critical, not going into overvoltage mode, even when the voltage on the main circuit becomes equal or greater than the voltage of the anode source nutrition (5e 1).

By the time of the onset of the critical mode, the dynamic characteristic receives a bend in the upper part, and during further work in the area of the critical mode, it assumes a position close to horizontal (see Fig. 2 — a bold line).

Due to this type of dynamic characteristic of the lamp in the second (considered) part of the modulation characteristic, the anode current pulses become more and more flattened, the transition in the maximum mode almost to the rectangular form.

From here, too, the pattern of change in a, and a.j, is close to that shown in FIG. 1 dotted lines.

The nature of the change in the shape of the pulses over a half-period of modulating voltage (from E, "." To E ,, J is shown in Fig. 3.

to increase the coefficient of efficiency and the rated power of the generator lamps.

In addition, the proposed method, along with it, gives a more rectilinear modulation characteristic, creates a lighter thermal mode for the generator lamps and makes it possible to reduce the power of the modulator device.

The implementation of the proposed method with anodic modulation, as with grid, is performed by distorting the shape of the variable variable component of the anode voltage in such a way that, despite the continued increase in the amplitude of the alternating voltage of the main frequency (), the residual voltage at the anodes the lamp does not fall below the value corresponding to the critical mode, and at the same time it provides a more energetically favorable form of the pulses of the anode current.

These distortions are produced by adding to the undistorted voltage of the fundamental frequency, creating 1, emus on the anode circuit, voltage of three times the frequency, which has a reverse initial phase relative to the main one, for which the generator is connected to the anode circuit in series with the circuit tuned to the fundamental frequency (directly or via a communication element) an additional (auxiliary) oscillatory context) p tuned to the tripled frequency.

As a consequence, the variable component of the anode voltage will be the sum of two variable anode voltages, and this phase ratio allows, with the same residual voltage on the anode, at the time of greatest voltage on the grid, to obtain an amplitude of the fundamental oscillating voltage that is much larger than usual in critical mode.

The foregoing explains FIG. 7, where thin lines depict the curves of the unsupportable anodic voltage components with amplitudes 7, and

and, superimposed on a constant anode voltage E, and a thick line-curve of the total alternating voltage on the anode.

It is clear that such a distortion of the shape of the variable anode voltage should correspond to a well-defined distortion of the anode current pulses, providing the necessary ratio between the amplitudes and harmonic phases.

As is well known, anodic current pulses, symmetrical about the vertical axis, as a result of being located in the Fourier series, along with other components, contain first and third harmonics, and the third harmonic, compared to the first, can have different ratios in amplitude and coinciding or reverse initial phase, depending on og of the pulse shape. In particular, with a cosine pulse, the third harmonic with respect to the first has a coincident initial phase at cut-off angles from 0 to 90, after which its phase is reversed. When the distortion of pulses in the upper part (cut-offs, hollows, dips, etc.) appears, this reverse phase transition occurs at lower values of the lower cut-off angle.

By selecting the appropriate values of grid bias and excitation, as well as the parameters of the circuits (main and auxiliary), matched with the parameters of the lamps used, constant anode voltage, etc., it is not difficult to implement the nonsupply frequency mode, which provides the necessary ratio between said harlshins, moreover, when the anodic voltage is changed to one side or the other from the working one, the established phase relation does not change, and the amplitude voltage is subject to small changes.

The foregoing indicates the complete possibility of realizing the distortion of the shape of the variable anode voltage in the desired direction.

FIG. 6a, the curves of changes are shown in solid thin lines.

ways to enhance modulated oscillations.

By selecting the lower cut-off angle 6 less or more than 90 °, the third harmonic effect is introduced during the entire modulation period, and variations are possible that allow the modulation to be deepened or weakened, and also partly (or completely) compensated for the lower flexure of the modulation characteristic.

Anodic modulation. As the series of theoretical and practical work shows, deep and linear modulation to the anode is possible under the condition that during the whole modulation characteristic the generator operates in an overstressed mode.

Recently applied anodic modulation in overvoltage mode with a push-modular modulator operating in the second kind of amplification mode (class "B") is known as anodic modulation with a concentrated efficiency. areas of increase to c. at the expense of the modulator, does not make it possible to increase the rated power of the generator lamps and further increase the efficiency without reducing this power.

The fact that the whole modulation process must be carried out in an overstretched mode (otherwise linearity is violated) suggests that the generator, at the highest point of the modulation characteristic, is in an overstretched mode, and therefore, with a relatively small residual voltage. cannot be fully utilized by the emission current | without speaking of operation at the saturation current), i.e. the possibility of increasing the rated power of the lamps remains unused. Accordingly, the energy capabilities in the carrier frequency mode are also not used.

In addition, in the overvoltage mode, it is known that the anode current pulses have a depression or a greater or lesser magnitude depending on the degree of overvoltage of the mode, therefore, the modulation is carried out due to the deformation of the anodic current pulses, which cause a change in the height of the pulses and the depths of the dips or hollows.

FIG. 61} broken lines depict approximate waveforms of anode current, corresponding to five points of the modulation characteristic; in fig. The curve also shows the variation of the anode voltage, respectively, for the same points of the modulation characteristic, but this form of pulses does not give significant advantages, both in terms of the absolute value of their first harmonic decomposition (/), which characterizes the vibrational power, and in terms of the ratio the first harmonic to the constant component

V - / "" JL 4

characterizing the efficiency of the generator. This suggests the possibility of increasing the efficiency due to a further increase in the anodic voltage utilization factor.

 .

with the anodic modulation method used, it cannot be carried out due to the resulting reduction in nominal power.

In addition, the used method of anodic modulation gives a slight bend in the lower part of the modulation characteristic (see Fig. 8 — the modulation characteristic is depicted by a thin flat line).

According to the proposed method, the generator has the ability to work with significantly higher

ami

while increasing as the absolute values of the first harmonic anode TOKci, tat; and its OTFTO solution to the constant component of the same current, which in total leads simultaneously to a significant method both in grid and anodic, modulation or amplification of modulated oscillations, three schemes are provided:

1. Scheme of the one-cycle generator with grid neutralization (Fig. 9).

2. Scheme of a single-ended generator with anodic neutralization (Fig. 10).

3.Le.ma two-stroke (push-pull) generator with neutralization of electrode capacitance (Fig. 11).

In these schemes, x and l denote reactances (shoulders of the bridge), i and g, are the main and additional circuits, s, s, (Tj, are neutrodin capacitors, are

for balancing the neutrodin bridge.

All schemes on the side of the grid circuit of the generator do not require any changes in comparison with the existing devices; for grid bias, the use of both DC voltage sources and gridlic or their combinations is allowed.

It goes without saying that the above schemes do not exhaust all possible forms and embodiments of the device for carrying out the proposed method; in particular, the above, as well as other possible schemes are equally applicable for both parallel and sequential

anode power and allow work on shielded lamps (neutralization is eliminated).

The subject matter of the invention.

1. Method of compensating for the upper bend of the modulation characteristics of the modulated high-frequency oscillator, characterized in that by introducing a variable anodic voltage f; triple frequency oscillations, the generator is forced to work with a grid modulation during the first negative half-period of the modulating voltage in the underdamp mode with pointed anodic current pulses, and for the rest of the period the generator is forced to work in a near-critical mode with flat impulses. lsami anode current.

2. Variations of the method but p. 1 ,. characterized in that by introducing oscillations with triple frequency into alternating anode voltage, the generator is forced to work during anodic modulation — a large part of the modulating voltage period in the near-critical mode, with compensation for dips in anode current pulses, which in the upper part modulation characteristics of the transition to flat form.

the variable component of the anodic voltage of the fundamental frequency, and the solid thick lines show the curves of the variation of the total variable anode voltage for the same (mentioned above) points and conditions that were taken with the commonly used anodic modulation method (dashed curves on same figure). Accordingly, in FIG. 6b, solid lines depict exemplary forms of anode current pulses.

At first glance, de FIG. 6a, clearly, the advantages of the proposed method, both in terms of anode voltage — an increase in the amplitude of the alternating voltage of the fundamental frequency, which leads to an increase in power and efficiency, and in current, giving a greater value of the first harmonic, which leads to an increase power.

A more detailed study of this form of current pulses shows that along with the increase in the first harmonic in absolute value, its ratio to the constant component also increases, which leads to an even greater increase in the coefficient of useful action. Only at the lower portion of the modulation characteristic (pulse I in Fig. 6th) the generator goes into a more overvoltage mode than usual, with a corresponding decrease in the absolute value of the first harmonic, which is just desirable, since it allows the modulation characteristic, usually having a bulge in this area. In the particular case, depending on the required change in the type of modulation characteristic, the mode can be easily changed, a grid shift combined with a grid, etc., is applied.

FIG. 8 solid thick lines show approximate static modulation characteristics of the generator

(.) And (L

resulting from the application of the proposed method; in the same figure, the corresponding characteristics are shown in solid thin lines for the case of using the conventional anodic modulation method.

From consideration of the modulation characteristics of FIG. 8 clearly shows the energy advantages of the proposed method, which, according to approximate calculations, can give an increase in the nominal power of the generator lamps by and more (as compared to the commonly used method) while simultaneously increasing the efficiency factor by 25-35 / ,, (i.e., instead of the usual, 7 get 1 0.9); at the same time, the linearity of the modulation characteristic is improved and conditions are created to reduce the required power of the modulating device (the coefficient of useful action for the proposed method is calculated in the usual way, as the ratio of the useful vibrational power, at the fundamental frequency, to the total input power).

All the noted positive qualities of the proposed method appear simultaneously, but if there is no need to increase some indicators, they can be increased even more differently, for example, if there is no need to increase the generator power compared to the usual method, with the same increase k. the generator generator voltage (25-3.5; o) reduce the working anode voltage and the amplitude of the modulating voltage, i.e., further reduce the required power of the modulator, and thereby increase the coefficient The effect of the entire installation.

In addition to these advantages, the proposed method creates an extremely light thermal condition of the generator lamps due to the fact that a significant part of the already reduced power losses in the anode circuit is released in the form of oscillatory power in the auxiliary circuit.

As examples of individual possible forms of making devices for carrying out a copyright certificate I.N. Fozshcheva

JVo 51945

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