US1987880A - High frequency amplifier - Google Patents

Description

Jan. 15, 1935. VILLEM 1,987,880

HIGH FREQUENCY AMPLIFIER Filed May 5, 1930 6 Sheets-Sheet 1 wit-111+- INVENTOR v RAYMOND VILLEM ATTbRNEY Jan. 15, 1935.

R. VILLEM HIGH FREQUENCY AMPLIFIER Filed May 3, 1930 6 Sheets-Sheet 2 K A, Fwy

5 9 \T E If U V s my 5 m QL I 1 1 i ATTORNEY Jan. 15, 1935. R. v E 1,987,880

HIGH FREQUENCY AMPLIFIER Filed May 3, 1930 6 Sheets-Sheet 5 INVENTOR RAYMOND \IILLEM ATTORNEY Jan. 15, 1935. R. VILLEM 1,987,880

HIGH FREQUENCY AMPLIFIER Filed May 5, 1930 6 Sheets-Sheet 4 L k 5 I 7 INVENTOR RAYMOND VILLEM BY ATTORNEY Filed May 3, 1930 6 Sheets-Sheet 5 i CM INVENTOR RAYMOND VILLEM BY 7W;

ATTORNEY Jan. 15, 1935. R, v L 1,987,880

HIGH FREQUENCY AMPLIFIER Filed May 5, 1930 6 Sheets-Sheet 6 gwfffffffff m Hi xxxwxxxx xmxxxgz INVENTOR RAYMOND VILLEM ATTORNEY Patented Jan. 15, 1935 UNITED STATES PATENT OFFICE 1,987,880 HIGH FREQUENCY AMPLIFIER Application May 3, 1930, Serial No. 449,403

In France May 8, 1929 4 Claims.

The present invention, concerns improvements in amplifiers and more particularly in their application to the amplification of very high frequency (short wave) oscillations, especially in the generating and transmitting devices. It provides the means and the constructive arrangements for obtaining particularly effective apparatus with the aid of these applications. It may, besides, be used in general manner in all amplifiers, for instance in receivers, wherever the advantages gained by it are of interest.

The invention will be better understood by means of the following detailed specification when read in connection with the drawings, in which Figure 1 represents diagrammatically the type of amplifying system to which the invention is applied, the improvements in the circuit arrangements and particularly advantageous embodiments;

Figure 2 illustrates the improvements in the circuit arrangements according to the invention in their application to the transmission or similar problems;

Figures 3A, 3B, and 30 show an embodiment and mounting of the elements built according to the directions of the invention with respect to the same applications;

Figure 4 concerns the establishment of intermediate amplifying stages which may precede the power stage which is the object of the preceding Figures 2 and 3 or which may be employed for the construction of receiving apparatus; and,

Figure 5 is a reference figure showing the arrangement as usual in the prior art and which is provided with improvements according to Figure 4.

The diagram of the principle of the amplifier stage which is the object of the invention is similar to the one indicated in Figure 1 in which, according to the circuit arrangement used by the art, the neutrodyne condensers N, N form an equalized bridge with the grid-plate capacity of the triodes for the purpose of preventing the reactive effects between the input circuits and the output circuits and inversely. According to the invention, particular means are utilized to prevent the losses in the refrigerating conduits of the plates in case the tubes used are provided with water circulation and to insure the equalization of the output currents of the tubes as well asthe measure of the plate :and grid currents for each of the tubes.

In Fig. 2, the circuit arrangement of the system improved according to the invention in an embodiment of an end amplification stage, may be seen in three parts, each thereof outlined by a dot-dash boundary line. Part I relates to the oscillation circuit proper, the self-induction coils L, L each consist of two copper tubes wound jointly (see Fig. 30), one is used as inlet for the water into the refrigerating vessel of the plate and the other acts as the outlet.

These coils are themselves in turn connected with the water distributing system by coils consisting of rubber tubes, s, s which insure the insulation for the direct potential which is applied to the plates of the tubes by means of the selfinductance coils L, L.

This arrangement prevents the high frequency losses in the rubber coils s, s which are connected to the oscillating system at points A, A where the high frequency potential is practically zero, the connecting condenser C1 being dimensioned in such a manner as to offer a feeble reactance to the currents of the oscillating circuit by which it is traversed. This condenser is likewise the means for separating the currents absorbed by each plate and which are measured by means of ammeters A1, A1 connected, after the self-inductions Z1 11 used for preventing the self-excitation of the system, in parallel circuit arrangement.

Shunted with the high potential supply HT are the condensers C3, C3 for the purpose of preventing the return of the high frequency currents towards the source HT.

Finally condensers C4, C4 are shunted in series with the terminal wires E, E of the aerial connected in shunt with the self-inductances L, L in order to prevent the charging of these latter to the potential of the high voltage supply source of the plates.

The part II represents the exciting circuit of the system, the self-inductances L2, L2, coupled to the oscillating circuit L3 of the last stage or the controlling agent, are connected with their adjacent ends to a capacity C2 thereby closing the exciting circuit for the high frequency currents and separating for each tube the grid outputs measured by means of ammeters A2, A2 .coupled after the .self-inductances l2, 12, thereby enabling the resistance R3 to block the system of self-excitation connected in parallel.

The ensemble of the condensers C5, C5 .and the r resistances R1, R2 form the grid-leak of the tubes, the resistances R1, R2 may be different and may be connected separately to the source of polarization of the grids. In this manner the negative grid potential may be adjusted to the value most convenient for the oscillation of the tubes and accordingly, in the case where the characteristics of the latter are slightly different, the power input of the plates may be equalized.

The coupling self-inductances L2, L2 are connected to the grids of the tubes across a voltage step-up transformer represented by part III.

This transformer comprises two tuning condensers C7, C7 shunted by the self-inductances Z3, Z3, offering a very great reactance to the high frequency currents but allowing the passage of the grid direct current, and two self-inductances L4, L4 connected by a blocking condenser C6 of very feeble reactance which closes the circuit for the high frequency currents and separates the grid circuits for the direct potential applied to these latter. This transformer is adjusted in such manner as to suppress the stationary waves in the conductors of the connecting line 3, 3 between the excitation. circuits and the oscillating circuit. This system is obtained when the resistance of the power circuit connected to the end of the line is equal to'the characteristic impedance of this latter, in other words, when the following conditions are satisfied:

Where R denotes'the average resistance of the filament-grid circuit and K the ratio R/Rl of this resistance at the characteristic impedance of the line R1. The self-inductances Z3, Z3 and the condenser C6 interfere very little in this high frequency system due to their dimensioning as indicated previously.

The ensemble of the oscillating elements has been particularly developed for the purpose of its use for the operation with waves of short lengths. To this end they are, in accordance with the invention, disposed in the manner that the ensemble occupies as small a space as possible and grouped in a manner so as to reduce to a minimum the connections of certain elements and to even eliminate the connections by uniting the same in the parts which must be electrically connected with one another. Finally, in order to reduce the capacity effect of the system with respect to the earth the parts which produce the same and which have a small high frequency potential are disposed towards the interior of the space occupied by the ensemble.

It will be shown later that another advantage of this arrangement is concerned with the neutro dyne condensers.

In Figure 3A, I represents the oscillating elements proper and II the transformer acting upon the grids of the triodes.

The oscillating circuit whose embodiment is also indicated inFigures 3B and 3C is carried by insulating bars B which are supported by porcelain pieces P fixed on the base 5. It comprises a condenser C whose fixed plates (1) are arranged symmetrically with respect to the movable plates 2 which latter may be moved by a control device V of any suitable kind.

Due to the oscillation of the system in the symmetric arrangement, the plates (2), insulated by the bar 6 are, with respect to high frequency, at the potential of the earth but they are preferably not directly connected with the latter so that the lamps do not become self-excited separately g It will be seen (Fig., 33) that the movable plates arrangement (2) comprises one plate more than each group of the fixed plates (1), charged with a high frequency potential, in order to surround the central part of the system by elements of this latter which possess a low high frequency potential. This is the reason why, according to the invention, there is provided between the tubes, for a given space requirement (determined by the value of thecondenser and the distance between the plates), a maximum of theratio of the useful capacity to the parasitic capacity, this ratio being defined electrically by that of the number of lines of force passing from a fixed plate to the movable plate to the number of lines of force contained between the fixed plate and the ground.

The mobile blade 2, or what might otherwise be termed the rotor of the condenser, is subject to linear displacements vertically. The support 7 of the mobile blade is mounted upon a screw threaded rod as indicated, constituting a worm, in turn guided and driven by a sleeve having an internal thread. This sleeve is visible at the lower portion of Figure 3a. Also, as indicated, the said sleeve is made integral with a bevel gear wheel in mesh relation with another wheel V in turn driven by a horizontal shaft for the purpose of adjusting the mobile condenser blade or plate.

In Figs. 33 and 3C are indicated in L the self inductances of the oscillating circuit which, as was explained previously, provide at the same time the inlet and outlet for the cooling medium of the plates through the rubber coils shown in Fig. 30 by s, s. I

The neutrodyne condensers represented at N in Figs. 3A, 3B, 30 have each their fixed plates 4 attached to the same cast plate (5) as each group of the fixed armatures of the condenser of the oscillating circuit. The movable plates 6 of the neutrodyne condensers are disposed towards the exterior of the oscillating ensemble, these plates being charged with a low potential with respect to high frequency (grid potential I-IF with respect to the earth) collecting thereby almost all the lines of force which without their presence would have the tendency to pass directly from plates 4 or their supporting plate to the ground; in thisway they insure the shunting of the high frequency currents which are produced towards the grid of the opposite tube, thereby preventing the self-excitation of the system.

The movable plates of each neutrodyne condenser are preferably equal in number to those of the fixed plate so as to encase the latter equally in the front part of the system and to locate the tank of tube T between the rear fixed plate of the neutrodyne condensers and the cast plate (5) so that it does not protrude over the space occupied by the ensemble.

Although the embodiment above described is especially adapted to the final stage of an amplifier for transmitting purposes and while, as indicated previously, it is shunted directly with an aerial it must be understood that it may be used equally well as intermediate stage.

Notably in transmitting arrangements comprising a plurality of elementary antennae, energized in groups, a disposition may be provided in which a stage of the described type is shunted across a line to which are connected in parallel the input ends of several analogous stages, each of whose output ends feeds one of the antenna or one of the antenna groups.

Another object of the invention has the purpose to improve the circuit arrangement according to Fig. 1 in orderto obtain intermediate amplifying stages for transmitting or receiving apparatus.

The tubes used in these applications generally do not have water circulation. In this case the preceding arrangements concerning this element cannot be used.

In Fig. 1 is indicated by L1, L2 the ensemble of the self-inductance L1 of the plate oscillating circuit of the stage here concerned and of the self-inductance by coupling L2 whose ends are connected to the grids of the next following stage.

This coupling, the arrangement of which is shown in detail in Fig. 4 at L, L0 for the element I and the stage preceding it and at L1, L2, L3, L4 between the respective stages I and II, II and III, is advantageously established, according to the invention, by means of two coils wound by hand with two wires, each coil comprising an odd number of turns in order to insure for the total self-inductance an absolutely symmetrical distribution of the potentials with respect to the center points to which are connected the potential sources of the plate S and the sources of polarization (negative) of the grids U.

This arrangement is, besides, particularly interesting from the view point of simplifying the regulation, especially in the case of amplification at the receiving end, for the very high frequencies, for the reason that it is the means for requiring only one tuning condenser C per stage, which condenser is either connected between the plates or between the grids.

In fact it is evident that, due to the above described arrangement, the h. f. potential at the two self-inductances of the ensemble is the same for two diametrically opposed points with the result that the potential at each point of the coupling self-inductance assumes the natural potential existing between turns of the selfinductance of the plate.

In this manner the poor standard arrangement according to Fig. 5 is avoided in which, the adjacent ends of the self-inductances being charged with diiferent potentials, the resulting electrostatic effect (very important in the case of frequencies corresponding to short waves) is counteracting the electromagnetic coupling effect between the windings. In this case it is necessary, in order to reduce the influence of the electrostatic effect, to increase the distance between the self-inductances, resulting not only in a decrease in the electromagnetic coupling but also in the potential obtained between the ends of the coupling self-inductance. In order to bring this potential to the desired value it is then necessary to provide for a second condenser, shown at 0, whose manipulation complicates the adjustments.

I claim:

1. In a symmetric radio frequency arrangement comprising thermionic tubes, an input circuit connected with the control electrodes of the tubes and comprising exciting inductance coils whose ends removed from the grids are united by a capacity, a tuning condenser shunted by an inductance inserted in the connections between the exciting inductance coils and the control electrodes, and a blocking capacity having an im pedance of very low value, in series with two symmetric inductance coils interconnecting the control electrodes.

2. A radio frequency transmitter arrangement comprising at least a pair of power tubes having associated therewith an oscillation circuit comprising a tuning condenser, said tuning condenser having three portions, each portion comprising a plurality of condenser plates, two of said portions being fixed and connected respectively with the plates of said power tubes, the third portion of said condenser being relatively movable and having one condenser plate more than said fixed condenser portions, each of the plates of said fixed condenser portions being located between two plates of said movable condenser portion, the end plates of the entire condenser arrangement being those of the movable portion of the condenser, said movable portion being maintained at ground radio frequency potential.

3. In a radio frequency amplifier, a plurality of cascaded amplification stages, each stage comprising a symmetrical arrangement of electron discharge devices and input and output circuits therefor, means for grounding the mid-points of the input and output circuits for radio frequency potentials, means for coupling the output circuit of one stage to the input circuit of another stage, said last mentioned means comprising transformers, said transformers being wound so that each turn of the primary is placed between two turns of the secondary and vice versa, the midpoints of the windings being fed with unidirectional potentials from unidirectional sources having a point thereof grounded.

4. In a radio frequency amplifier, a plurality of electron discharge device amplifier stages, each of said stages comprising a symmetrical arrangement of tubes and input and output circuits, means for maintaining the mid-points of input and output circuits at radio frequency ground potential, and means for coupling the input circuit of one stage to the output circuit of another stage comprising transformers having their primary and secondary windings wound so that each turn of the primary is between two turns of the secondary and vice versa, the mid-points of the windings being fed from grounded sources of unidirectional potential, and, a single tuning condenser being placed in shunt relation to one of said windings.

RAYMOND VILLEM.

Images