US2239910A - Wave generating means - Google Patents

Description

April 1941- N. H. CLOUGH 2,239,910

WAVE GENERATING MEANS Filed April 5, 1938 2 Sheets-Sheet l VOLTAGE 0 0/005 5' ,II'ZLJ9. 24 T1445 vomas 0NAMO0E18 (AVON-'19 meow/mm?) llw g. 2b

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TIME O V0046; awn/005 29 I I I k I 51 207/ TIME m: m a; DIVANODE 0F VALVE 32 m] g r/m' M17165 0/ AFR/Al. mum CIRCUIT Z17 z nus f iNVENTOR :iSWSOMF H. CLOUGH ATTORNEY N. H. CLOUGH WAVE GENERATING MEANS April 29, 1941.

Filed April 5, 1938 2 Sheets-Sheet 2 m m R v m NM T 1 A Patented Apr. 29, 1941 WAVE GENERATING MEANS Newsome Henry Clough, Brentwood, England, assignor to Radio Corporation of America, a corporation of Delaware Application April 5, 1938, Serial No. 200,134 In Great Britain April 6, 1937 6 Claims.

This, invention relates to thermionic valve apparatus Which will hereinafter be termed alternating current amplifier apparatus, though, as will be seen later, arrangements in accordance 'withthis invention are not, in the strict sense,

amplifiers. This term is used, however, for reasons of simplicity and because there is no short term. which will accurately define circuit arrangements in accordance with this invention.

, The invention is of broad application but prob-- ably its most importantapplication is to amplifiers (herein so called) f oscillations from. a master oscillator for use in a radio or similar transmitter. For the sakeof convenience in description. the invention will be mainly described with reference to such an application.

Fairly early in the development of carrier wave radio transmitters the so-called independent drive type of arrangement began to be used. In this type of arrangement a master oscillator having its own frequency determining tuned circuit was employd and the oscillations from this cillator were communicated directly to the grid of a driven valve or amplified a desired number of times by a desired number of tuned high frequency amplifiers before being transmitted. In order to obtain high anode efficiency the practice began to be adopted of arranging at least the final tuned; thermionic valve amplifier stage in such an arrangement to operate as a so-called Cf class amplifier; that is to say, the final amplifier was arranged in effect to be impulsed only by the positive peaks of the sinusoidal voltage waves set up across the tuned circuit of the preceding amplifier, the output from the final amplifier being nevertheless approximately sinusoidal by reason of the action of the tuned circuit in its anode circuit. In suchan arrangement the grid current pulses in the grid circuit of the final amplifier stage are short peaky impulses spaced apart in time by regular amounts depending upon the frequency, and these pulses are transformed by the final valve into anode current pulses of the same spacing. These pulses of anode current give rise to approximately sinusoidal voltage waves across the closed tuned circuit in the anode circuit by virtue of the flywheel action of the tuned circuit and the corresponding voltage waves across the aerial or other load circuit are rendered even more closely sinusoidal if this circuit is of, a resonant nature and tuned to the same wave length. The present invention enables the use, hitherto found necessary in practically successful circuits, of 1one or more resonantly responsive tuned valve stages between a source of oscillations (such as a master oscillator) and a final stage having its own frequency determining tuned or equivalent circuit, to be dispensed with and in carrying out i the said invention the hitherto provided means,

for tuning the stage or stages between an alternating current source and a stage which has its own tuned flywheel or equivalent circuit and is to be driven by said source, are omitted. In other words, the invention enables a master oscillator or other source of alternating current to be employed to drive a resonant valve stage through one or more impulse responsive or aperiodic stages.

It should be understood that the invention is not limited to transmitters using separate closed and aerial (or other load) circuits, for the invention is applicable to the case Where an aerial is directly coupled to the stage which feeds it, e. g. is tapped upon a coil in the anode circuit of that stage. In such a case the said stage still really has its own tuned. flywheel circuit for the capacity of the aerial to earth may be regarded as constitutingthe condenserof a closed circuit in the anode circuit of said stage.

An arrangement in accordance with this invention is, as will now be appreciated, not in the strict sense of the word a repeater or amplifier, for the intermediate stage or stages between the source and the final driven stage do not repeat the sinusoidal oscillations from the source but merely produce impulses or flicks which are transferred to the driven stage which then oscillates in synchronism (either at the fundamental or at a harmonic frequency, as Will be explained later) and the term impulse and aperiodic? as employed in this specification is used to distinguish from the usual known arrangements in which all the individual stages are tuned so that each stage produces a more or less sinusoidal output voltage wave.

The practical advantages obtained by the present invention are substantial. The use of a series of tuned stages between a master oscillator and a final driven stage involves considerable exoften regarded as preferable to incur the expense of providing a series of pre adjusted tuned circuits or at least pre-adjusted reactances so that the change over from one wave length to another can be made quickly by operating switches. This, of course, means further expense. The present invention enables the dispensing altogether with the hitherto thought necessary tuned circuits in the intermediate stage or stages andavoids these difficulties and items of cost.

According to this invention a magnifier valve, which may be operated as a class C amplifier or as a class B amplifier and having its own "flywheel circuit into which it feeds is driven from a source of oscillations by means including a normally conductive inductive circuit carrying a current and soconnected that the sudden reduction or cessation of said current causes said magnifier to become conductive, means being provided for effecting such reduction or cessation wave from the source and accordingly, the said magnifier may be resonant at twice the source frequency.

The invention is illustrated in and further explained iii-connection with the accompanying drawings.

In the drawings, Fig. 1 illustrates the essential features of my new and improved wave signalling system comprising wave generating, wave forming and wave amplifying means. In Fig. 10., I have illustrated modulating means which may be used in the system of Fig. 1. Figs. 2a to 2 inclusive, are curves used in illustrating the operation of the system of Fig. 1, while Figs. 3 and 4 illustrate modifications of the system of Fig. 1.

Referring to Figure 1 whichshowsdiagrammatically an embodiment wherein the sourcefrequency is doubled at the final driven stage, a source of alternating current sinusoidal oscillations,forex-ample the master oscillator of a radio transmitter, is constituted by a valve I whose anode-cathode circuit includes a parallel tuned circuit 2, 3, as in the usual way, the necessary high potential feed from a source 4 being taken to the anode 5 of the valve I through a choke 6 a resistance 9 and the mid-point I of the coil 2 in said tuned circuit. The junction of the choke 6 with the resistance 9 is earthed through a de-coupling condenser 8, the tuning condenser 3 in said tuned circuit being preferably (as shown) of the centre plate type having its central plate connected to earth through the de-coupling condenser 8. The ends of the tuned circuit are coupled each through a condenser III, II, to the control grids I2, I3, of two valves I4, I5, constituting a frequency doubling impulse stage one end of the said tuned circuit being coupled to the control grid I2 of valve I4 and the other to the control grid I3 of valve I5. The controlgrids of the two valves I4, I5, in this frequency doubling stage are connected to the common cathode point through equal resistances I6, I1, and the two anodes I8, I9, are connected together and through an ohmic resistance 29 and a decoupling choke 2I in series to the high potential source 4. The junction of the ohmic resistance 20 and the decoupling choke 2I is earthed through a decoupling condenser 22. The common point of the two anodes I8, I9, is connected through a condenser 23 in series with a grid resistance 24, which should be as free from reactance (especially inductance) as possible, to the cathode 25 of a further valve 26. The junction point of the resistance 24 with condenser 23 is connected, preferably through a further small ohmic resistance 21 to the control grid 28 of the valve 26. The anode 29 of the valve 26 is connected to the source 4 through an inductance 39 and is also connected directly to the control grid 3| of the final driven valve 32. The cathode 25 of the valve 26 is connected to the cathodes of the two valves It, I5, in the frequency doubling stage. The cathode lead of the driven valve 32 includes a capacity shunted bias resistance combination 33, 34, between the cathode 39v and the positive terminal of source 4 and the anode circuit of said driven valve includes a tuned circuit 35 which is coupled to an aerial or other load circuit (no-t shown). For the case of a telegraph transmitter the control grid 28 of the further valve 26 may be connected through a telegraph key or relay 36 either directly or (as shown) through asmall source 31 of negative grid potential insufficient to cut off the valve, to the cathode 25 of the said valve 26. In the case of a telephone transmitter the grid resistance 24 may be connected as shown in Fig. 1a, not directly to the cathode point, but through a source 38 of modulation potential and a negative grid bias source 37 to the cathode 25.

The operation of this circuit will now be de scribed with reference to Figs. 2a to 2f, inclusive, the action of keying or of modulation being, for the sake of simplicity of description, neglected. When the master oscillator I is oscillating there will be a substantially sinusoidal voltage wave as represented in Figure 2a set up on its anode and the positive peaks of this wave will produce, as shown in Figure 2b sudden negative (peaks or dips orimpulses of voltage on the anode I8 of valve I4 in the frequency doubling stage due to current in the valve I4 (the anode I9 is assumed to be disconnected). The negative peaks of voltage on the master oscillator valve anode will similarly produce, as shown in Figure 20, negative peaksor dips. or impulses on the anode I9 of the valve I5 in the frequency doubling stage (the anode I8 is assumed to be disconnected). The dips o-r negative impulses due to positive peaks of master oscillator anode voltage will occur midway between the clips or negative impulses due to negative peaks of master oscillator anode voltages and therefore there will appear, atthe junction point of the anodes I8, I9, a series of negative impulses at twice the master oscillator frequency. These impulses are transferred to the control grid 28 of the further valve 26 and produce on th anode 29 thereof sudden powerful positive pulses of anode potential as represented in Figure 211 these pulses occurring at twice the master oscillation frequency. These pulses are produced by reason of the fact that the negative pulses on the grid of the further valve 26 suddenly cut off said valve and there is included in the anode cur-' rent circuit of said further valve the inductance 30. Therefore these positive anode pulses on the anode 29 of valve 36 will be powerful and steep sided since they are generated by breaking an inductive current carrying circuit. These positive pulses are applied to the grid 3| of the final driven valve 32 and the tuned circuit 35 in the anode circuit of the said driven valve, which effect converting positive grid excursions from the master oscillator into negative flicks as required by the interrupter valve (the valve 26).

, Figure 3 shows a preferred modification of the circuit of Figure 1. In Figure 3 a phase reversing valve is employed between the master oscillator (not shown in Figure 3) and the valve equivalent to the valve 26 of Figure 1-this valve may be termed an interruptor valve in view of its function-and the interruptor valve is coupled to the final or magnifier valve directly. Figure 3 may be regarded as equivalent to Figure 1 with the valve l5 removed and the circuit 35 tuned to the fundamental instead of to the second harmonic.

Referring to Figure 3, 2, 3 is the anode tuned circuit in the anode circuit of the master oscillator valve (not shown). This tuned circuit feeds into the grid 40 of a phase reversing valve whose anode-cathode circuit includes a coupling resistance 42. 43 is a source of anode potential and 44 is a choke. The anode 45 of valve 4| is directly connected to the grid 28' of the interruptor valve 26' whose anode circuit contains the interruptor choke 3D and a resistance 46 in series and whose anode 29 is directly connected to the grid 3 I of the final valve 32. In Figure 3 separate sources of anode potential (represented conventionally by generators) are provided for the valves and the necessary bias for the valve 32 is obtained by the action of the resistance 46 which is common to both the anode circuit of the interruptor valve 26' and the grid circuit of valve 32. This resistance 46 is on the earthy or dead side of the interruptor choke 30 and will have a standing voltage difference set up across it due to the anode current of the interruptor valve 26'.

Figure 4 is very similar to Figure 3 the main difference being that in Figure 4 the final or magnifier valve, here marked 32' is a pentode. Where the final valve is a pentode modulation is preferably accomplished as indicated by applying modulating potentials to the suppressor grid 41 from any suitable source 38 connected in the suppressor grid circuit in any convenient part thereof, e. g. as shown, the carrier being previously adjusted by means of the tapping on the battery or other potential source part of which is in series with 38.

The invention is not limited to the precise circuits shown. For example modulation or keying may be effected in any of a plurality of different ways which will suggest themselves to those skilled in the art while a variety of different methods of coupling the various stages together is available, Since the interruptor anode circuit is inductive and normally conductive, any of the usual coupling methods-e. g. direct, transformer,

auto-transformer, or capacity-may be employed.

With direct or auto-transformer coupling the interruptor valve cathode must be negative with respect to the final or magnifier valve cathode. Where double wound transformer coupling is employed very tight coupling may be obtained by winding the primary and secondary coils together, i. e. with the wires side by side. In this case, if the end of the secondary next to the anode end of the primary is connected to the magnifier grid correct phase will be preserved and there will be no variation of electrostatic potential between adjacent primary and secondary turns. Figures 3 and 4 the resistance 46 may be incorporated in choke 30' by winding the latter with resistance wire or otherwise incorporating loss therein. Further the phase reverser valve 4| of Figures 3 and 4 or the corresponding valves l4, N5, of Figure 1 could be a pentode or pentodes as also could be the interruptor valves in all the fig ures. The use of a pentode as the reverser valve has the advantage of isolating the master oscillator drive very effectively, while, if desired, telegraph keying may be effected by a relay or key between its screening grid and earth.

Havin now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed I declare that what I claim is:

1. An efficient high-frequency wave generating system comprising in combination, a source of oscillations, an amplifier tube having a control grid electrode and cathode and having output electrodes, a reactive circuit tuned to a frequency related by an integral number to the frequency of said source of oscillations connected to said output electrodes, an inductive circuit coupled with said control grid and cathode, means for causing current to flow in said inductive circuit and for biasing said control grid negative relative to said cathode an amount sufficient to render said amplifier non-conductive when current flows in said inductive circuit, and means operated by oscillations from said source of oscillations for periodically reducing the flow of said current in said inductive circuit at a frequency determined by the frequency of said oscillations to cause said amplifier to become conductive periodically and supply current impulses to said reactive circuit to produce therein oscillatory energy.

2. A wave generating system as recited in claim 1 with means in said reactive circuit for tuning the same to double the frequency of the oscillations of said source of oscillations.

3. In a wave generating system in combination,

an oscillation generator, an amplifier tube havinga control grid and cathode and having output.

electrodes, a reactive circuit tuned toa frequency related by an integral number to the frequency of operation of said oscillation generator connected to said output electrodes, a circuit including an inductance connected with said control grid and cathode, means for causing current to flow in said last circuit and inductance and for biasing said control grid relative to the cathode by a potential such that said amplifier tube is nonconductive when current fiows in said inductance, a phase reversing tube arrangement coupling said oscillation generator to said circuit including an inductance for periodically reducing the flow of current in said first named inductance at a rate determined by the frequency of operation of said Again, in

5. In an efficient wave generating system, a

source of'oscillatory energy, an amplifier tube having a control grid and cathode and having output electrodes, a reactive circuit tuned to a frequency related by an integral number to the frequency of the oscillations of said source coupled to said output electrodes, an additional electron discharge tube having input electrodes and having output electrodes, a circuit including inductance connected to the output electrodes of said last additional tube and coupled to the control grid and cathode of said amplifier tube, means for biasing the input electrodes of said additional tube by a potential such that said additional tube causes current to flow in said circuit including said inductance and said flow of current produces a negative potential on the control grid of said amplifier tube relative to its cathode such that said amplifier tube is non-conductive, means, actuated by oscillations from said source of oscillations, coupled to the input electrodes of said additional tubes to momentarily and periodically impress on said input electrodes a negative bias suihcient to periodically reduce the flow of current in said circuit including said inductance whereby the negative bias on said amplifier tube control grid is periodically overcome and said amplifier tube periodically supplies voltage to said reactive circuit. 7

6. A system as recited in claim 5 wherein said means actuated by oscillations from said source includes a frequencydoubler and said potential on the input electrodes of said additional tube is overcome by said negative bias at a periodicy double the frequency of the oscillations from said source, and wherein said reactive circuit includes means to tune it to twice the frequency of the oscillatory energy of. said source.

NEWSOME HENRY cLloUGH.

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