US2004127A - Antenna regulator for diversity reception - Google Patents

Description

June 1l, 1935. H o. PETERSON --2,004,127

ANTENNA REGULATOR FOR DIVERSITY RECEPTION Filed Nov; 1e, 1928 2 sheets-sheet E Y 39,4 /y'//Qa//VE /T f:

DEEC-' //aZ/F/-e 62 A l iT *L J- 'il' u Y E A 24 34 Y *TTV* Syvum/woz HAROLD o. PETERSON Y v' gh/S @Mom/w13, L/LL lJuil@ ll, 1935. H. o. PETERSQN l 2,004,127

ANTENNA REGULATOR FOR DIVERSITY RECEPTION v 'Filed Nov. 16. 1928 F2 iZ'T/ IMPI/Flip sz llllllll g 124 58 134 v 144 (54 55 68 wm/woz HAROLD o. PETERSON @3x1/WIJ 2 sheets-sheet 2 Patented June 11, 1935 UNITED STATES ANTENNA REGULATOR FOR DIVERSITY RECEPTION Harold O. Peterson, Riverhead, N. Y., assigner to Radio Corporation of` `AmericaVa. corporation of Delaware Application November 16, 1928, Serial No., 319,938

16 Claims.

This invention relates to diversity reception, and more particularly to a method and means for advantageously regulating the output from a plurality of antennas.

Short wave signals are subject to fading which varies both in frequency and degree in an unpredictable manner. Inasmuch as the fading at any instant may differ very widely at geographically spaced points, or in different planes of polarization, it has been suggested that a receiving station be equipped with a number of antennas having different fading characteristics, vthe energies collected by which are fed to a single signal` responsive means.

Experience has shown that high frequency energy fluctuates not only in intensity but also in phase, and that there may be considerable relative phase fluctuation at the several antennas. This phenomenon makes it impossible to. directly combine the radio frequency energies, for the energies may as often be in phase opposition as in like phase. To overcome this difculty it has been suggested to equip each of the antennas with a separate receiver, and to combine theenergies after rectification, and this,'in the case of code signals, has proven an apt solution.

However, I have found that in the case of speech telephony, or other speech-simulating signals, where the transmission energy is radiatedin the form of a carrier and side bands, there may be a relative difference in the phase fluctuations of closely adjacent frequencies, such as side band and carrier frequencies, even at one antenna, just as there is between carriers of like frequency at different antennas. This causes similar phase fluctuations in the beat of the carrier and side bands, for if of two beating waves one is kept constant in phase, while the other is'shifted in phase, their beat is equally shifted in phase. It consequently follows that although the carrier and side band energies experience only radio frequency differences in phase, these differences are transferred to the detected or audio frequency energies,

so that it is as impossible to combine'the detected energies as it is to directly combine the originally collected radio frequency energies. u

With the usual type `of diversity system, even if applied merely to code signals, the received energy is apt to vary between the extremesof almost complete fading at all of the antennas to no fading at any of the antennas. To overcome this it has'been suggested to employ a volume control with each antenna for varying the gain in the amplifier coupled thereto. Such an arrangement suffers from the disadvantage that the increased gain. given an :amplifier vof an, antenna :at which fading is .prevalent increases the noise level in the output of thatv amplifier, and therefore. the combined output of the Ventire system. vkFur,- thermore, in the case of speech-simulating signais, in the Aevent of fading of the carrier `and not of the side bands at an antenna its 'amplifxerzis givenincreased gain, asa result of which` the `beat between the side bands 'is unduly .amplified` before being combined with the output from thefother antennas, thereby creating augmented distortion, In order to overcome the foregoing diiculties I propose to select from among the several 1antennas that antenna .at which the received signal is the strongest, and 'to greatly magnify the initial signal strength differential, so` that `the energy from the selectedantenna will greatly predominate over the other. In this way there is flittle conflict due to relative phase .fluctuations at the different antennas, and a considerable amount of volume control is` providedzmerely in using Vsubstantially only one antenna at a` time. .Furthermore, an antenna receiving speech-simulating signals at which the `carrier alone has faded lis given diminished output, and therefore has but little effect on the receiver, which reduces distortion.

, In order to effect remarkably smooth operation, and to simplify the necessary apparatus, I do not physically disconnect all` of the antennas but one, but rather permit them to remainy in circuit, and regulate their outputs. In terms of a method, my invention includes simultaneously makinga plurality of separate energy collections of` relatively different fading characteristics, preferably by collecting the energy on a plurality of geographically spaced antennas, utilizing the energy from each of the antennas for reducing the strength of signal from the other of the antennas in such a mannerthat the weaker signals are further weakened more than proportionally, so that the strong signals are relatively strengthened while the weaker signals are relatively weakened, and thereafter or simultaneously combining the energies and utilizing the combined energy, so that energy is fed to the'utilization means predominately from the antenna having the strongest signal. In a preferred and an exceedingly simple modification I employ separate electron emission tube detectors for each of the antennas, Yand I couple the anode circuits of the detectors together land to a source of anode potentialv and a` common anode impedance,` so that the anode currentof each of the detectors tends to reduce the-anode potentialapplied to the following specication, which is accompanied by drawings in which Figure 1 is a wiring diagram for a form of my invention employing common regulation by variation of anode potential; Figure 2 is a diagram explanatory of the operation of the arrangement shownin Figure 1; and Figure 3 is a modified arrangement employing individual regulation by variation of control electrode potential.

Referring to Figure 1 there are a plurality of antennas 2, 4, and 6, which are given different fading characteristics in any suitable manner, such as by being geographically spaced, or positioned in different planes cf polarization, and any desired number may be used. They are coupled by transmission lines I2, I4 and IE to autodyne heterodyning means 22, 24, 25. It will be undern stood that separated local oscillators and heterodyne detectors may be employed, the autodyne circuit differing merely in that the same tube which-acts as an oscillator tube also acts as a detector tube for combining the received and locally generated energies. The resulting ener.- gies of intermediate frequency are fed to intermediate frequency ampliflers 32, 34 and 35, to which are coupled the electron emission tube detectors 42, 44 and 4t`,.across the output circuits of which there preferably are connected a suitable number of filter sections 52, 54 and 56f`or bypassing the radio frequency components of the detected energy. The anodes of the detector tubes are then connected together, as shown, and to a commonv source of anode potential 58, and a common anode impedance 6B, the lower terminal kof which is grounded to complete the anode to cathode circuit.

In operation the flow of anode current through the impedance 6U causes a reduction in anode potential. Assuming` one of the signals to be l stronger than the others the resulting reduction i which is due to the anode current of the other tubes is not suflicient to overcome its initially greater input voltage. Of course, the operation of the system is predicated upon the assumption of a differential or inequality in the received Signal strengths, and in practice it is found that this assumption is safe. If the signal strengths happen to differ even very slightly the difference is immediately magnified owing to the `'operation of the detector tubes according to an asymmetric characteristic, usually a square law. r

The operation of' the invention may be mor clearly explained in connection with Figure 2, in which the anode current Ip, of a detector tube, is plotted as a function of the input voltage, Eg.

i The characteristic curve is different at diierent Yanode potentials, this being indicated by the curves H39, |92, and |04, corresponding to decreasing potentials, say 80 Volts, 60 volts, and 40 volts, respectively. If it be supposed that the resultant' anode current fiow, due to some strong signal |96, as well as one or more weak signals |48, is sufficient to bring the anode potential down to 40 volts, the resulting characteristic curve will be the curve |44, and, noticing the intercept of this curve with the Zero line of anode current, it will be seen that as a result the signal i536 will, and the signal |08 will not, produce an output. The normal potential values have been so chosen, in this illustration, that there is no output at all from the weaker signal, which is a very desirable condition, but it should be understood that the operation may be carried out anywhere else along the characteristic curves, and owing to the fact that they folloviT a square law characteristic, there will always result a relative weakening of the weaker signals, and a magnified predominance of the stronger signal.

To obtain the combined energy for utilization the potential drop across the common anode im pedance 58'(Fig. l) is applied to the control electrode of an amplifier tube G2, through a grid bias blocking condenser'iili, and the output from the amplifier may be applied through a transformer 6G to any suitable utilization means, such asa rebroadcasting station 68. Monitoring translating devices l!) and l2 may be provided at the receiving station and at the rebroadcasting station.

The paramount factors of this arrangement are merely a plurality of antennas, a plurality of detector tubes, and a common anode impedance through which the polarizing energy for exciting the anodes of the detector tubes flows. of superheterodyne receivers with intermediate frequency amplifiers is optional, andif used, they may be connected directly to the antennas, as shown, or be provided with radio frequency amplifiers. I f

Attention is now directed to Figure 3, in which there are a plurality Yof antennas H2, H4, and I Iii, which are coupled by transmission lines |22, |24, and |26, tofradio frequency ampliers |32, |34, and |36. .The'amplied outputsjare reduced to an intermediate frequency by autodyne heterodyne detectors |42, |44, and |46, the outputs from which are amplified inV intermediate frequency amplifiers |52, |54, and |56. The intermediate frequency energies are then detected by detector tubes |62, |84, and |65.

Each of these detector tubes is individually regulated by variation of its grid bias potential. To this end there are included in the cathode to anode circuits, and preferably in series between the cathodes and ground, the resistances |12, H4, and |16, which determine the control electrode potential of the regulator tubes |82, E34, and |84. The anode circuits of the regulator tubes include resistances |92, |94, and |95, the potentials across all or a portion of each of which are used to determine the control electrode bias of the detector tubes |62, |64, and. |66, respectively. Batteries 202, 204, and 205 may be used to fix the normal detector bias at a desired value. In operation, an increase in signal strength causes an increased current flow through resistances |12, |l'4, and |16, which increases thepositive potentials on the cathodes ofthe regulator tubes |42, |04, and |94, thereby decreasing the anode'current -iiow through the resistances |92, |94, and |96, which decreases the negative potential applied to the control electrodes of the detector tubes |62, |64,

|65, thereby increasing the detector nitputs.`

However, as before, owing to the asymmetric characteristic of the detector tubes, the increases in output are not proportional, but are greater in the case of those tubes havingstrongersignals,

The use 2,004,127 setlist the output ,from` the tube having the strongersignal is relatively strengthened and predominant.

The anode'clrcuits' of the detector tubes IGZ, U54, and ISG, include low pass filter sections 2l2, 216, and 216, to shuntthe radio frequency components of the'rectiedenergy, while the signal components are combined in any suitable man- ;ner, here exemplified by connection tota-common anode battery 58 and anode impedance Se, just Y'as was disclosed in Figure l, which results in inl lecting signal energy on a plurality of antennas,

rectifyihg the signal energies, using the rectified energy from each of the antennas for reducing the strength of signal from the other of the anten'nas infsuch a` manner that the weaker signals are further weakened more than proportionally, combining the recti-ed energies, and feeding the combined rectified energy to utilizing means.

2. The method of reception which includes collecting signal energy on a plurality `of antennas, rectifying the signal energies in electron emission tube detectors, using the rectified energy from each of the detectors for reducing the anode potential applied to the other of the detectors, in order to magnify any initial signal strength differential, combining the rectied energies, and feeding the combined rectified energy to utilizing means.

3. The method of reception which includes col-Y lecting signal energy on a plurality of antennas, rectifying the collected energies in electron emission tube detectors, feeding the rectied energies from the detectors and the anode polarizing direct energy to the detectors through acommon impedance, whereby the rectified energy from each of the detectors tends to reduce the polarizing potential applied to the anodes of the other of the detectors, and feeding the combined rectifled energy to utilizing means.

4. The method of reception which includes simultaneously making a plurality of separate energy collections of relatively different fading characteristics, separately rectifying the collected energies in electron emission tube detectors, using the rectified energy from the `detectors for making the potentials on the control electrodes of the detectors more negative, whereby the weaker signals are further weakened more than proportionally, combining the rectied energies, and feeding the combined rectified energy to utilizing means.

5. The method of reception which includes simultaneously making a plurality of separate energy collections of relatively diierent `fading characteristics, separately rectifying the collected energies `in electron emission tube detectors, using the rectified energy from the detectors for making more negative the potentials applied to both the control electrodes and the anodes of the detector tubes, whereby the weaker signals are further weakened more than proportionally, combining the rectied energies, and feeding the combined rectified energy to utilizing means.

' 6." A receiving system comprising a'plurality `of antennas n having different fading characteristics, a pluralityof electron emission tube detectors `coupled thereto, meanscoupling the anode circuits of thedetectors` together and to a source of anode potential and a common anodeimpedance, wherebythe anode current of` each of `the `detectors tends to reduce the anode potential appliedto the4 other of the-detectors, andutil'ization means responsive to the combined detector current. f

` "lpA` diversity receiving system comprising a plurality of geographically spaced antennas, a plurality of electron emission tube detectors coupled thereto, a` common source ofanode potential, a common anodey impedance, means coupling the anodes of all ofthe detectors tothe common source and impedance, whereby the anode*` current of each ofthe detector tubes tends to reduce the anode potential applied to the other of the detector tubes, and a utilization circuit coupled to the common anode impedance;

c 8. A diversity receiving system` comprising a plurality oi antennas having relatively different fading characteristics, a plurality of electron emission tube detectorscoupledV thereto, means responsive to the anode currents of the detector'` tubes for varying the control electrode `biasing potentials thereof in order to magnify any initial signal strength differential, a common utilization circuit, and means coupling the anode circuits of the tubes to the utilization circuit.

`9. A diversity receiving system comprising a plurality of antennas having different fading characteristics, a plurality of electron emission tube detectors coupled thereto, an impedance in the anode to cathode circuits of each of the detector tubes, a regulatorl tube coupled to each of the impedances, an impedance in theY anode circuits of each of said regulator'y tubes, a bias lead connected from each of the latter impedances to the control electrode of the respective detector tube, a common utilization circuit, and means coupling the anode circuits of the detector tubes to the utilization circuit.

10. A diversity receiving system comprising a plurality of antennas having different fading characteristics, a plurality of electron emission tube detectors coupled thereto, an impedance in the anode to cathode circuit of each of the detector tubes, a regulator electron emission tube coupled to each of the impedances, an impedance `in the anode circuits of each of said regulator tubes, abias lead connected from each of the latter impedances to the control electrode of the respective detector tube, a common source of anode potential for the detector tubes, a common anode` impedance, means coupling the anodes of all of the detectors to the common source and impedance, whereby the anode current of each of the tubes tends to reduce the control electrode and anode potentials applied to each of the detector tubes, and a utilization circuit coupled to the common anode impedance. Y

11. A` radio receiving system comprising in combination, a rst receiver, an antenna therefor said antenna being located at one point, a second receiver, a secondV antenna therefor located at a second point so separated from said first point that fading effects vary differently at said separated points, each receiver tuned to the same frequency, common means connected to both said receivers to indicate the signals received thereby, and means to govern the operation of one of said receivers in accordance with the strength of the signal received at the other of said receivers.

12. A radio receiving system comprising in combination, a first receiver located at one point, a second receiver located at a second point, said receivers receiving signals of like frequency but being so placed as to be subjected to different fading effects from a single transmitting source, and producing outputs substantially identical in frequency, and means to govern the operation of one of said receivers in accordance with the strength of the signal received at the other of said receivers.

13. The method of reception which includes collecting signal energies on a plurality of antenn amplifying each of the collected energies, rectifying each of the amplified energies for controlling the degree of the amplification of said other energies in such manner that the weaker signal energies are further weakened by the predominant amplied energy, combining the rectified energies, and feeding the combined energy to utilization means.

14. A receiving system comprising a plurality of antennae having relatively different fading characteristics, a tube having a rectifying characteristic coupled to each of said antenna, a common utilization circuit having its input energized from said tubes, and an impedance in said input and adapted to be traversed With current passing through said tubes forl magnifying any initial signal strenth differential, whereby energy is transmitted to said utilization circuit predominantly from that tube at Which'the rectified energy is a maximum.

15. The method of operating a radio receiving system having a plurality of antennae and an electric discharge device coupled to each antenna, which comprises producing a unidirectional potential which is a function of the amplitude of the Wave of largest amplitude received at any instant in any of said devices, and utilizing said potential to so affect the discharge devices in which the received waves are of substantially smaller amplitude that they are rendered substantially inoperative for the transmission of waves of said small amplitude.

16. The method of radio reception which comprises receiving at a plurality of separate points waves carrying the same signal, changing the frequency of the received Waves, detecting the Waves of changed frequency, producing from the detected waves a unidirectional potential, and controlling in accordance with said potential, the transmission of the received waves to substantially suppress all but that one of the received Waves having at any instant the largest ampli: tude.

HAROLD O. PETERSON.

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