US2205475A - Ultra-high frequency receiver - Google Patents

Description

June 25 19 lo' H. E. HOLLMANN ULTRA-HIGH FREQUENCY RECEIVER Filed May 6, 1937 DIRECTION 0F INCOMING RAD/0 WAVE -lll Illlllllllll:

N N A M L L O H H .Y Rw M R maf/ ms n VN NM A Y B Patented June 25, 1940 uNi'li-:DL STATES PATENT OFFECE ULTRA-HIGH FREQUENCY RECEIVER tion of Germany Application May 6, 1937, Serial No. 141,074 In Germany May 12, 1936 10 Claims.

This invention relates to a device for radio reception, particularly where ultra-short Waves are used. The socalled retarding field electron discharge tube is preferably used in carrying out my invention. 'I'his tube is known to be an eilicient form of detector for ultra-short wave.

receivers. 'I'he outstanding characteristic of my invention is that for the purpose of eilicient reception and demodulation of ultra-short Waves a retarding field electron discharge tube is provided and is so designed and arranged in circuit with other receiving apparatus as to collect the incoming energy on a certain electrode or electrodes of the tube. In this Way a given electrode or set of electrodes is arranged to possess the dual function of a receiving antenna system and of a device for repelling electrons in the opposite direction to that of the electronic emission. 1n one embodiment of my invention these antennas may be made non-directional in their receiving characteristics, while in another embodiment a very strong directional characteristic may be obtained.

It is an object of my invention to provide a radio receiving system employing retarding field detector tubes either for directional or nondirectional radio reception. It is another object of my invention to so arrange the elements of a retarding field tube as to employ the retarding eld electrodes within the tube for collecting the received signalling energy.

Other objects and advantages of my invention will become apparent upon review of the following detailed description when considered in connection with the accompanying drawing in which Figure 1 shows schematically an arrangement of a retarding eld tube in the focus of a parabolic reflector, and I Fig. 2 shows another embodiment of my inven- 40 tion in which the retarding field tube can be made to operate independently of an outside reector.

Exhaustive research regarding the functioning of reception and rectification in a retarding-eld or electron-oscillation tube has demonstrated that demodulation is ascribable to the non-linear internal resistance of the tube, or in other words, to the non-linear characteristic connecting the current and the voltage of such a retarding-field tube. This non-linear characteristic exists when aperiodic reception of oscillations is involved, even though the frequency is far higher than the electron transit times. The non-linear characteristic holds, also, when receiving ultrashort waves having a frequency equal to or a (Cl. Z50- 11) multiple of the frequency of oscillation of electrons of the retarding eld tube. Invariably demodulation is brought about in the retardingelectrode circuit, and the modulation currents obtained from the ultra-short wave carrier may be taken olf at will in the retarding-electrode circuit or else in the grid circuit into which they are fed by means of current transference. From a proper understanding of this situation, one important conclusion is reached, namely, that the high frequency voltages induced by the ultrashort wave carrier in a suitable receiver antenna must be impressed upon the retarder electrode itself in order to obtain the most eicient detection.

When working with radio waves of the order of 1 meter in length, it is an easy matter to couple the antenna circuit to the input circuit of an electron discharge tube. The energy collection may be made by a complex and somewhat sizable array of directional antennas if desired. Also, by taking suitable well-known precautions, as by the use of a coaxial cable, the energy may be transferred to a relatively remote receiver before detection.

Upon reducing the Wave length to about l decimeter, it is imperative that further precautions be taken in the design of the receiving system. In fact, it becomes almost necessary to apply the received energy directly to the retard electrode. A system so arranged will rst be described.

Referring to Fig. 1, I show a conventional form of retarding field tube 3 comprising a linear cathode 4, anodes 5 and an intermediate electrode 6 of grid or coil construction. The grid may be a wound wire of sufl'icient rigidity so as to make it unnecessary to attach separate convolutions to a supporting post. The circuit arrangement for this tube includes a source of direct current potential 'l which renders the grid very highly positive with respect to the potential of the cathode 4. The grid circuit includes a resistor 8 and the primary coil of a transformer T. The secondary winding of this transformer may be connected to any utilization device such as a set of headphones 9. A connection is made from the negative side of the battery 'l through a resistor I0 in parallel with a capacitor Il and thence to the anodes 5. The resistor l0 has a very high impedance like an ordinary grid leak resistor, but in this case the variations in potential applied to the anodes will produce differing voltages across the resistor l0. The cathode 4 may be heated by any convenientv source of energy such as that shown at II.

In order to collect as much radiant energy as possible and to concentrate the same on the outer surfaces of the anodes 5 the parabolic reflector I2 may be used. Without this reiiector it is evident that the characteristics of the receiver would be non-directional. However, in the case illustrated in Fig. 1, an incoming radio wave having the same directivity as-that of the axis of the parabola will be reflected upon the outer surfaces of the anode members 5', thereby varying the instantaneous potential thereof with respect to the potential of the cathode.

In the operation of this device as a receiving detector electronic emission from the cathode through the mesh of the high potential grid 6 will result in more or less of the electrons being collected by the anode members 5. If the number of electrons so collected is increased,rthe anodes become more negative. There is also a tendency to produce a drop of potential in the grid leak resistor I0. Hence, there will be a flow of current through this resistor and a simultaneous reduction in the amplitude of the current ow in the grid circuit. This is tru'e on the theory that the electronicv emission from the cathode remains constant If, then, the current iiow'in the grid` circuit is so varied in response to the incoming energy, it is evident that this current will vary in accordance with the modulations to be detected. Hence, it is possible to utilize the detected and rectiedvmodulation energy in any convenient circuit such as that which includes the secondary of the transformer T and the headphones 9.

While the anode members 5 have been shown as two coaxial cylinders connected together by a lead I3 of a suitable length for obtaining csf cillations, it is, in fact, possible to carry out the same idea in a somewhat simpler manner by usingv a single cylindrical anode member. When two anodes are used as shown, it is preferable that connection be made therewith through a yoke circuit I3 such that the junction point` I4 is positioned in an oscillatory node. From this nodal point to each anode the circuit should preferably be of a quarter wave length.

Referring now to Fig. 2, I show an entirely different system which is suitable for operation without the aid-of a parabolic reflector. The directional vcharacteristics of this system are obtained by the construction of the tube itself. 'I'he tube envelope I5 in this case contains a cathode K of plate formation where the electron emittingsurface has a relatively large area. This area may be coated with any suitable oxide or other material such as will produce high elec= tron emissivity.

Within the tube I also dispose a grid G and an antenna structure consisting of separate and distinct co-planar dipoles A1, A2 and A3. The upperarms of the dipoles A1 and A3 are connected together and to the lower arm of the antenna dipole A2. In like manner the lower arms of the dipoles A1 and A3 are connected together and tothe upper arm of the dipole A2. These dipoles are preferably spaced apart by as much as a half wave length. The plane in which they lie is perpendicular to the direction of the incoming radio wave. The wave itself is permitted to travel through an electrode H of grid formation but with the conductors thereof all lying parallel to one another and at right angles to the vlinear direction of each dipole.

This retarding eld tube is supplied with suitable potentials as from a high potential source I6 which connects through a portion of the potentiometer I1 to the grid G by way of the primary winding of a transformer T. The cathode is suitably heated by a source ofcurrent I8. If desired, the cathode may be ofrthe indirectly heated type or it may be in the form of a lament positioned in such manner that it will offer a large emissive surface facing toward the grid G. Another portion of the direct current source I9 interconnects the portions I6 and I8 and furnishes suitable potential through a potentiometer W, a tap from which may be used to supply a potential to the conductorL for enabling the dipole antennas to act as retard electrodes. Preferably two conductors L are employed, one for feeding the antenna arms of one set,v the other for feeding to the antenna arms which are excited in phase opposition by the incoming wave. The common conductor 2B is connected to the leads L preferably at a nodal point lof radio wave excitation of the dipoles.

The potentiometer W may be bridged, if desired, by a capacitor C. Another potentiometer 2| placed across the batteryportions I8 and I9 serves to supply suitable potential to the electrode H, the function of which will presently be explained.

Now, in order that a retarding eld may be set up between the lantenna system and the grid G, the antennas must be impressed with a potential which is only slightly positive or negative with respect to that of the cathode. The tap on the potentiometer W permits of this adjustment to optimum conditions for rectification. The primary consideration in making this adjustment is to draw electrons through the grid and approximately tothe plane in which the dipole antennas lie. However, the dipoles themselves lare so far apart that it would be impossible to arrest all of the electrons within a given plane. In order to smooth out the front of the retarding field the grid H is provided. The potential applied to this grid can be varied by means of a tap on the potentiometer 2l.

When suitable adjustments have been made in the potentials applied to the various electrodes of this tube, it will be found that the working point in the tube lies on the lower knee or bend of the retarding field characteristic. The homogeneous distribution of the eld inside the electron oscillation space is obtained largely by means of the adjustments of potential applied to the electrode H as has heretofore been explained. Thus, paractically all ofv the electrons which fly through the grid G are compelled to reverse their flight in one and the same plane which, according to the conditions of operation, may be situated either in front of or behind the plane of the antennas.

In order that the incoming or signal waves may reach the retarder electrode unimpededly, that is, in order that they may not be shielded or screened by H, it is necessary to design the cooperating electrode H to act as a polarizing grid having wires extending at right angles to the receiver dipoles A1, A3. Preferably the distance between grid G and the antenna system A is so chosen that the grid surface acts as a reflector, with the incidental result that the focusing or concentration power of the receiver antenna system A is boosted.

If the receiving dipoles A1 to A3 are so interconnected by way of L that the main direction of the radiation diagram lies in the plane of the' drawing, then the auxiliary electrode H naturally could consist of solid metal and conjointly with grid G will act as a wave channel.

In the drawing the directional receiver tube is shown incorporated in a suitable receiver circuit organization. The grid voltage Eg for the object of tuning the electron oscillations is variable, and in the grid lead is included the transformer T which feeds the modulation variations derived from the tube to a radio frequency or audio frequency amplifier. The potential of the antenna system by way of the high ohm leak resistance W adjusts itself spontaneously to the point of intersection of the straight resistance line and the tube characteristic. TheV said leak is shunted by the condenser C so far as the modulation potentials are concerned.

The electrons emitted from the cathode K execute to-and-fro oscillations about the positive grid G and they cause the antenna system of the retarding eld tube to be regeneratively excited. Atthe same time the resonance potentials induced by the incoming carrier oscillationsin the free ends of the receiving dipoles are rectified, and they result in the retarder electrode circuit in a rectified current which by virtue of current distribution is taken over in the grid circuit and which may be conducted away through transformer T. The regeneration and rectification actions occurring in the new tube here disclosed, therefore, do not diier from those in the customary retarder field receiver circuit organizations.

It may finally be noted that the principle underlying this invention is capable of quite a number of modified solutions which, however, are basically the same as the one incorporated in the exemplified arrangement hereinbefore disclosed. For instance, the antenna system could consist of any desired number of constituent or separate dipoles mounted adjacent or posteriorly of one another, say, in a socalled Christmas tree antenna arrangement as known in the prior art. Such modification of the system does not aiect, however, the basic principle of the invention.

I claim:

1. A radio receiver for ultra-short waves comprising an electron discharge tube having a cathode, a grid carried at a highly positive potential with respect to the cathode, an antenna system mounted within said tube and in the path of electronic emission beyond the grid, said antenna system comprising means including a plurality of co-planar dipole antennas disposed within the range of influence of radiant energy, and means for maintaining a high negative bias on said antennas with respect to said grid, thereby to reverse the direction of flight of electrons emitted by said cathode.

2. A receiver in accordance with claim 1 and having an additional electrode disposed in the path of the radiant energy, said electrode having a grid formation ofVr parallel conductors through which said radiant energy is enabled to pass before reaching the antenna system.

3. A retarding field discharge tube for a radio receiver comprising an envelope, a cathode of relatively large emissive area, a grid having means connected thereto for producing a highly positive bias thereon with respect to the cathode, a retarding electrode situated beyond the grid with respect to the cathode `and constituted by a plurality of dipole antennas having their linear axes lying parallel to one another and in a plane substantially perpendicular to the principal axis of flight of electrons emitted by said cathode and projected through the mesh of said grid, an auxiliary retard electrode maintained at a potential somewhat more positive than the cathode and further removed from said grid than the antennas, a circuit interconnecting the grid and cathode, another circuit interconnecting the antennas and cathode and means for carrying said antennas at a suitable bias potential with respect to the cathode for producing current variations of modulation frequencies in the respective circuits of said grid and said antennas in response to modulated ultra-high frequency energy collected by said antennas. y

4. A device in accordance with claim 3 and further characterized in that said auxiliary electrode is constituted by a grid having paralleldisposed conductors through which the received radiant energy has unimpeded access/to said antennas.

5. A device in accordance with claim 3 and further characterized in that said grid is disposed a predetermined distance behind the antennas, viewing the structure from the direction of the source of the incoming wave, and said grid reflects said wave back to said antennas thereby to increase the response to signals.

6. The method of collecting and detecting ultra-high frequency radiant energy in a retarding field discharge device having a cathode and at least three reticulated electrodes which comprises passing the radiant energy through the mesh of one of said reticulated electrodes while maintaining a somewhat positive bias thereon with respect to the cathode, collecting said energy on a second reticulated electrode, causing the last said electrode to variably repel the free electrons of said discharge device, subjecting a third one of said reticulated electrodes to a high positive bias relative to the cathode and causing the emission from said cathode to be maintained substantially constant while the currents between the third reticulated electrode and the cathode are varied in response to modulations of said radiant energy.

'7. A radio receiver comprising a parabolic reilector, a retarding field discharge tube disposed in the focus of said parabolic reflector, said tube having a linear cathode, a grid conformed to a cylindrical surface concentric with the cathode, and an outermost electrode also concentric with the cathode, an operating potential source having connections With the several electrodes such that the tube possesses a retarding field operating characteristic, means for impressing radiant energy on the exterior surface of the outermost electrode of said tube, and means for varying the current iiow between that electrode and another electrode of said tube in accordance with modulations of the received ultra-high frequency energy.

8. A device for ultra-short wave reception comprising an electron discharge tube having a cathode, a reticulated electrode and a plurality of other electrodes, means for applying to said reticulated electrode a potential which is highly positive with respect to saidcathode, means for enabling two of said other electrodes to act as complementary energy collectors, potential biasing means for causing the last said electrodes to serve also as retard electrodes, and a signalsensing device in circuit between said reticulated cathode, a reticulated electrode ancl a, retarding field electrode, means for energizing said reticulated electrode in a highly positive sense relative to the cathode and to the retarding eld eleotrode, means Yior disposing portions of said retarding eld electrode in two distinct but interconnected sets of radiant energy-collecting mem.-

bers, means for impressing a slightly positive bias on said retard electrodes with respect to the m cathode, and means wheretly the energy collect- ,ing members of one set are energized co-phasally and in phase opposition to the phase of the instantaneous potential with which the members of the other set are energized.

10. A device in accordance with claim 9 and including a wave-polarizing grid interposed between said retarding field electrode and the source of incoming radiant energy.

HANS ERICH' HOILMANN.

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