US2141292A - Radio receiver - Google Patents

Description

A. G. CLAVIER RADIO RECEIVER Dec. 27, 1938.

Filed Feb. 29, 1936 u a Nr z T 5 m W 1 m m ff/ 4 .H v1 m M 7 12 LEMA m/.L 2 68 IWI lr Il Y III r 1 I Nun wm -w ,Nl w1 /0 E cfeviff ,d A T-TOR/VEY Patented Dec. 27, 193s UNITED sTATEs RADIO RECEIVER Andre Gabriel Clavier, Paris, France, assigner to International Standard Electric Corporation,

New York, N. Y.

Application Februaryv29, 1936, Serial No. 66,408 In France April 29, 1935 7 Claims.

The present invention relates to controllable impedance elements which may be used in radiocommunication systems or regulation systems with or without wires, and in which the frequencies employed may be any desired frequencies.

The invention relates in particular to the provision of a device having an impedance for example mainly capacitive whose value may be governed according to the electric fluctuations of .0 control voltages applied to the device. The device functions quite as well for the relatively low frequencies as for very high frequencies.

`It will be seen from th'e following description that such an impedance element is constituted by 5 a system of electrodes with which means are associated for creating between two or more electrodes an electronic cloud and for causing the volumetric density thereof to vary.

The invention will be better understood by means of the following description based on the accompanying drawing, in which Figure l represents an element the impedance of which may be varied as desired, said impedance being mainly of capacitive nature.

Figure 2 is an example of application of such an impedance element to the realization of a system of communication with sustained waves of extremely high frequency, for example of the order of 1500 megacycles per second.

0 Similar elements in Figures l and 2 are designated by the same reference letters.

In Figure 1, a condenser is shown with a cylindrical armature I in the centre of which is a wire 2 for ming a second armature of the condenser;

5 this unit has a certain electrostatic capacity between the points A and B.

If, instead of a simple wire 2, we employ an electron emitting cathode heated by a battery 3, and an additional electrode, for example in the l form of a grid 4, is interposed aroundthis cathode, the capacity between the points A and B is changed but keeps a Well defined and constant static value.

The electrode assembly is enclosed in a bulb 3 inside which a vacuum has been created.

If now we apply to the electrode 4 and the electrode I tensions E0 and Er respectively, and if, moreover, the tension E0 is positive, electrons will be emitted by the cathode 2, and for a suit- 0 able negative value of the tension Er there will be formed inside the cylindrical electrode I, an electronic cloud whose density will be a function of the value of the tensions E0 and Er applied to the electrodes I and 4 and obviously also of the 5 emissive power of the cathode 2.

(Cl. 25o-8) If a variable potential is applied to the electrode 4 or I for a given frequency the capacity between A and B will be modified, as if the dielectric constant of the space comprised between the electrodes I and 2 were assuming a value different from unity, this value varying with the volumetric density of the cloud of electrons and consequently in particular with the value of the tensions applied to the electrodes I and 4.

'This effect arises from the accepted theory that when a certain number of free electrons exist between the armatures of a condenser, the apparent dielectric constant is modified with regard to the alternating electrical phenomena of which the condenser is the seat.

If e is the charge of the electron, m its mass, w a number equal to 2 1r times the frequency, the dielectric constant instead of 1 in the case of the vacuum, becomes 41re2y, mw2 S equation in which N is the total number of electrons, S the surface of each of the armatures of the condenser. This elementary calculation is applied to the case of a plane condenser.

It is quite obvious however, that an effect of the same order is produced in the system described above, which thus constitutes a condenser Whose dielectric constant may be made to vary at any frequency according to the more or less rapid fluctuations of a difference of potential controlling the volumetric density of the electronic cloud.

It will be clear that such arrangements are capable of numerous applications in the electrical art and may be employed Wherever a controllable impedance element is required in a circuit or for the operation of a communication system or regulation system or in similar cases; in particular. in order to obtain a modulation in frequency of a radio-electric oscillation, the arrangement of Figure 1 may be used.

It will be seen that in this figure there has been interposed in the connection 5 over which potential is applied to the electrode I, an oscillating circuit formed by a capacity 6 and an inductance 1 and that the biasing potential source Er has been shunted by a large condenser 8.

In such a system, for suitable values of Eo and Er, the tensions applied to the systems of electrodes I and 4 enclosed in the bulb 9 inside which a vacuum has been created, effect of negative resistance is obtained between the points A and B which permits oscillations to be sustained in the oscillating circuit l, 1. The frequency of these oscillations is determined by the value of the apparent capacity between the points A and B. If this capacity is caused to vary the result is a variation of frequency of said oscillations and it will be found that for suitable values of E0 and Er a condition is obtained in which the frequency obtained is variable without varying the amplitude of the oscillations. Thus a method of modulation in frequency of the oscillations generated in the oscillating circuit is obtained.

'I'he effect of negative resistance between A and B is generally bound up with the presence of oscillations of very high frequency along the oscillating electrode 4. 'I'here is thus produced in the circuit of the electrode I a current Ir which decreases for a certain scale of values when the negative tension applied to this electrode decreases, from which it follows that for these values we obtain the following equation whence the effect of negative resistance to which reference has been made above.

Another application of the invention is illustrated in Figure 2.

This figure represents schematically a receiver for use in a system of telegraphy by ultra-short waves, in which the emitted carrier waves are employed without iany intermediate frequency modulation. The keying of the sustained ultrashort waves atl the transmitter is assumed to be effected by any known means, such as the cutting o and the re-establishment of one of the feed potentials of the transmitting tube.

Figure 2 shows the receiving circuit. In this figure the ultra-short waves of frequency F are received on a doublet I3 connected to the control electrode 4 of the tube 9 whose electrodes I and 2 and the electron lled space therebetween constitute a condenser having a variable dielectric constant as explained in connection with Figure 1.

oscillations of intermediate frequency f are set up in the oscillating circuit 6-1 as previously described. The frequency f of these oscillations depends on the amplitude V,0f the frequency FF of the incident ultra-short waves.

A local oscillator III generates a frequency f1 which is caused to beat with the frequency f for example by coupling the circuit 6-1vand the oscillator I! by means of a transformer I2 with an amplifier detector I4 output of which is applied to a utilization apparatus I5.

If it be arranged that in the absence of incident waves F, the frequency n is equal to the frequency f, when waves of frequency F are incident upon the doublet frequency f is modified. The frequencies f and f1 beat together and a signal is obtained whereby the utilization apparatus I5 may be actuated in well-known manner. Morse signals can thus be received on an audio frequency note. By utilizing different beat frequencies intermediate frequency amplification may be employed and a second detector provided for obtaining signal currents capable of actuating a recording apparatus, for example a teleprinter.

In order to obtain maximum eiilciency in reception it is desirable that for a particularly intermediate frequency the oscillating circuit 6-1 should have a relatively low capacity, and in order to increase the sisnal-to-noise ratio an intermediate frequency f should be chosen which ls as high as possible.

rt is obvious that equality of thefrequency n with the frequency f in the absence of incident waves is not essential and that systems may be conceived in which .simply the change in the beat frequency between the local oscillator l1 and the frequency .f is employed.

It will'be obvious that condensers having controllable dielectric constants such as those described above by way of example, may be given widely different applications. For example, such condensers may be employed wherever it is necessary to couple two oscillating systems with one another.

Moreover the shape of such condensers may be varied according to the desired application. In particular plane electrodes may be employed. The control electrode instead of being constituted by a helix 4 could thus be in the form of zig-zag line. It would also be possible to employ electrode systems having conical symmetry etc., and to provide condensers having more than two armatures. Means such for example, as accelerator electrodes or electrodes for concentrating electrons, may also be employed for modifying the electron clouds.

What ls claimed is:

1. A modulation system for high frequency alternating currents comprising a source of high frequency carrier waves, a frequency determining circuit for said source, a source of signal waves, a highly evacuated electron discharge tube including a thermionic cathode, an oscillatory electrode and a reflecting electrode, said cathode and said oscillatory electrode being adapted to create a purely electronic cloud in the dielectric space between said cathode and said reflecting electrode, a controllable capacity element included in said frequency determining circuit for modulating said high frequency carrier waves and comprising said cathode and said reflecting electrode, together with the dielectric space between them and the electronic cloud in said dielectric space, and means for impressing said signal waves upon said oscillatory electrode for varying the density of said electronic cloud and the apparent dielectric constant of said dielectric space.

2. A carrier wave receiving system, comprising means for collecting energy from incoming waves, a highly evacuated electron discharge device having' a thermionic cathode, an oscillatory electrode and a reflecting electrode, means for biasing said electrodes to substantially the potentials suitable for sustaining decelerating field oscillations and for heating said cathode whereby free electrons are produced between the electrodes of said device, a local source of oscillations, a frequency determining circuit for said local source including a xed impedance and a portion of said electron discharge device, said portion of said discharge device constituting a variable capacitance whose dielectric material comprises evacuated space and the free electrons therein, means for varyingjhe dielectric constant of said dielectric material responsive to variations in said incoming waves whereby the frequency of the oscillations generated by said local source are varied in accordance with said incoming waves, the exact potentials with which said oscillatory and reflecting electrodes are biased being such that the amplitude of the oscillations generated by said local source re- .sin

has a negative resistance characteristic, said negmains substantially constant during said frequency variations.

3. A receiving system for ultra-short electromagnetic waves comprising means for collecting energy from incoming waves, a highly evacuated electron discharge tube including a cathode, an oscillatory electrode and a reflecting electrode, a resonant frequency-determining circuit including said tube adapted to generate local oscillations of a frequency unrelated to the frequency of the incoming waves, a portion of said tube being adaptedto form a capacitative impedance whose dielectric material is constituted by the evacuated space within the tube together with the free electrons in said space said impedance being connected in said circuit so as to control the frequency of said oscillations, connections for' impressing energy of said incoming waves upon an electrode of said tube whereby the dielectric constant of the said dielectric material is varied to vary the frequency of said oscillations, and means responsive to such variations in frequency for indicating the reception of said incoming waves.

4. A receiving system in accordance with claim 3 in which the reflecting electrode and the cathode and the space between them constitutes the said frequency determining impedance and in which the energy of the incoming waves is impressed across two points of the oscillatory electrode of said tube. 5. A receiving system in accordance with claim 3 in which the said portion of the tube which constitutes a frequency determining impedance ative resistance characteristic serving to maintain the said oscillations while the reactive component of said impedance is varied in response to variations in the energy of the incoming wave so as to vary the frequency of said oscillations.

6. A receiving system for ultra-short electromagnetic waves as claimed in claim 3 further comprising a second circuitadapted to generate local oscillations and means for deriving a beat frequency from said two local oscillations.

'7. In combination a substantially gas-free electronic discharge device which includes two electrodes and means for creating a purely electronic cloud in the space therebetween, a tuned circuit which includes an inductance and a mechanically static 'condenser comprising. said electrodes as condenser plates and comprising the space therebetween together with the electronic cloud therein as dielectric, said circuit being tuned to such a frequency that the reactance of said cloud forms a substantial portion of the effective circuit reactance, a source of varying potentials, and means for varying the effective reactance of said circuit under control of said source solely by varying the apparent dielectric constant of said dielectric, said means comprising means for varying the volumetric density of said cloud responsive to variations in said source and means for maintaining across said space such potential gradients that changes in said volumetric density cause substantial changes in said dielectric constant.

ANDRE GABRIEL CLAVIER.

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