US1824803A - Method and apparatus for receiving wireless signals - Google Patents

Description

Sept. 29, 1931. w. M. BRUCE I 1,824,803

METHOD AND APPARATUS FOR RECEIVING WIRELESS SIGNALS Filed April 30,1928 4 Sheets-Sheet l I [1. J d7 4:

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Sept. 29, 1931. w. M. BRUCE METHOD AND APPARATUS FOR RECEIVING. WIRELESS SIGNALS Filed April 30, 1928 Sheets-Sheet 2 Sept. 29, 1931. w. M BRUCE 1,824,803

METHOD AND APPARATUS FOR RECEIVING WIREIJESS SIGNALS Filed April 30, 1928 4 Sheets-Sheet 3 Sept. 29, 1-931. w. M. BRUCE 1,824,803

METHOD AND APPARATUS FOR RECEIVING WIRELESS SIGNALS Filed p il 1928 4 Sheets-Sheet 4 b m fiat I 4- 7 a 1 Ila-B 1 D L g 1 .+B.nt7'- avwcmtoi 35% WWM PatenteclJSept. 29, 1931 I' N E YSTA ES PATE T FF wI 'nIArr-m. nat on, or SPRINGFIELD, OHIO' METHOD AND nrrnnarnsroa RECEIVING WIRELESS SIGNALS Application filed April 30,

- My invention relates to methods and apparatus for receiving wireless signals or high frequency oscillations. a.

- The object of my invention is to provide methods and meansfor eliminating from the circuits of a wireless receiving apparatusthe so-called static or disturbing impulses or ose cillations so that-the desired signals can be received free from such disturbances;

to In carrying out my invention I make' use of the-well known principle'that if two currents of opposite-phase or polarity, but hav ingthe same frequency and characteristics are impressed upon the same circuit they will cancel or neutralizeeach-other and of the further principle that by the aid of properly constructed apparatus as is usually included under the-term filter a single definite frequency can be stopped and other frequen= cies-will pass through the circuit. a

/ In its simplest form I employ in an ordi nary wireless receiving apparatus a local circuit including a filter preferably having variable tuning and I connect this local circuit to theregular'receiving circuitinsuch a way that the local receiving circuit has impressed upon it all of the incoming oscillations and impulsesin the usualmanner. By the aid of the filter or equivalent devices I prevent the. passage. through this auxiliary circuit of the frequency which it is desired to receive in the receiving set. The other frequencies are allowed to'pass through toithe local circuit and are then impressed upon the circuit of the regular receiving appartaus in such a manner that all impulses or oscillations having-like frequencies or characteristics arecancelled'. Thus the.tuned in incoming frequency is the only one which will pass through the regular receiving circuit free from the static or other disturbing influences which have been concelled by like frequencies or disturbances of opposite phase impressed thereon.

In the accompanying drawings which are diagrams of various circuits and modifications embodying my invention; r I

Fig. l'shows a well known type of superheterodyne circuit to which my invention has u been applied.

Fig. 2 shows my invention applied to a 1928.' Serial N0: 273,869.

simple receiving circuit of well known form having asingle amplifying tube.

Fig. 8is a similar circuit in which a special form of tube with multiple grids is shown. 4 is a view of a similar circuit with slight modification in the wiring connections; Fig. 5 is a diagram of a well known circuit having two radio amplifying tubes and a local cancelling circuit, which also has therein an amplifying tube.

Fig. 6 is a similar view with slight modifications. Iv Fig.3 7- is a diagram showing the application of my' invention to a receiving circuit such as is used in the reception of wireless telegraphy or undamped oscillations with a local heterodyne.

" Figs-8 and 9 are views showing modifications and including amplifying tubes in the auxiliary circuit.

" Fig.10-is a'detail view showing a special form of filter.

. "Figs. 11 and 12 are modifications in which 'an amplifier and'oscillator are used in the auxiliary or cancelling circuit. 7

Referring to Fig. 2 in which a circuit of simple form isshown 1 represents an ordinary radio amplifying tube. Theaerial A'is connected by transformer T, with the usual-variable condensento the grid of the tube and the plate circuit of the tube isconnected through transformer T to the next succeedingtube or receiving device. These parts having the usual A; B and C battery connections as shown.

Extending around thetube 1 from the aerial connection to the plate circuit and the primary coil of the transformer T- I provide an auxiliary or cancelling circuit 9 including a filter '13 which is preferably made with variable parts by which it may be made resonant to any desired frequency. There is also preferably included in this circuit a variable condenser 15 connected to the filter by wire 12 to prevent fiow of plate battery 5 throughthe filter and to regulate the amplitude of the impulse. I

In the'operation of this circuit the regular receivingdevice will be tuned to a certain definite frequency which is adapted tobe received by the receiving set. There will be usually included with this frequency certain other disturbing frequencies such as static or other characteristic currents which cannot ordinarily be tuned out by the usual tuning devices and they will pass throughithe amplifying tube and through the transformer T at the. same time there will beset up in the auxiliary or cancelling circuit 8, 12, 9, frequencies having like characteristics as those in the main circuit except that by reason of the transposition in the transformer they willbe in opposite phase or polarity. By bringing the filter 13 into resonance with the main frequency or signal carrying wave intended to. be received that, particular frequency will be prevented by the filter from passingthrough the local. or auxiliary circuit. There will therefore be impressed upon the. receiving circuit in. opposite phase or polarity all frequencies, oscillations etc.

received by the set, other than the. desired frequencies. (which will be stopped by the auxiliary or filter circuit). and these being impressed upon the regular receiving circuit will cancel or eliminate all of the disturbing factors leaving only the main signal carrying'wave or frequency to pass'through the receiving circuit and to-the final translating device. Y

Figs. 3; and 4 arediagrams similar to Fig. 2 with slight modifications in the-wiring and connections. In each case the filter-13 isin the auxiliary or.- cancelling circuit 9, 12 and 8. There is however a variable resistance R connected in the circuit and, a. fixed condenser 15, these being for the purpose. of varying the amplitude of the. impulses passing through, the auxiliary circuit.

In Fig. 3 whichv shows a tube having multiple-gnids the auxiliary circuit is connected tothe. auxiliary grid of the tube instead of the regular grid.

Fig. 1- on the same sheet showstheinven: tion applied. to a usual form of superhetero; dyne. receiving circuit. In this figure A shows the source of theincoming high frequency oscillations and B represents the source of. local oscillations. 1, 2 and3 represent the tubes of which 1 is the first detector and 2and 3 theintermediate stages of radio frequency amplification. The wires 6- and 7. lead to the second detector in. the usual manner.

Two-auxiliary circuits with two filters are shown here, one around the detector 1 and the other aroundthe radio amplifying tube-3, the connections and arrangements are substantia-llythe same as shownin Fig. 4.

A s'uperheterodyne receiving circuit lends itself readily to the application of my. invention from the fact that theradio frequency stages ofamplification have at all times a single and fixed frequency toamplify and the filter or filters maybe designed and-tuned in a permanent manner, no adjustment of the filter being necessary when different incoming high frequency oscillations or wave lengths are being selected.

Figs. hand 6 show further modifications and also show the invention applied to other forms ofreceiving circuits. In these figures the auxiliary circuit including the filter also has an amplifying tube 10 so that the impulses and oscillations which pass through the auxiliary circuit may be amplified and-regulated so. that the strength of thecancelling impulses and oscillations will equal in amplitude like impulsesv and oscillations in the circuit of the receiving set.

In Fig. 5' the transformer]? is. showrr with a. double wound and. differentially connected primary 5 to which the auxiliary circuit is connected and. by means of which the opposite phase or polarity for the impulses: passing through the auxiliary circuit and filter are secured.

Fig. 6; shows substantially. the: same; arrangement in which the usual by pass cons densers G and C1 are shown in connection with the audio. transformer which has thediffentially wound primary 5.

Figs/T. shows a type of wirelessreceivin-g c rcuit especially adapted for the. reception of wireless telegraphy or; undampedoscillations. In this. figure numerals. 1', and2 are radio. frequency amplifying tubes shown with transformer coupling. 3 is a detector and wires 6 and 7 lead to the next stage of audio frequency amplification. B shows a local source of oscillations which if desired may include the-plate circuit of the detector tube to. operate: as a selfheterodyne. The. local circuitis shown connected by'wire 9to: the second winding-of the radio transformer T and; includes the filter 1-3 with variable. re? sistance R and condenser 14 being so con.- nected that the-relativephase angleand amplitude of disturbingimpulses and. oscill'ae tions will cancel and eliminate like'and-cornespending impulses and oscillations that are pnesentin the grid. circuit of'tube 11..

Fig: 8 is. a. somewhat modified: circuitin which a nadiofrequency amplifying tube 10 is used in the auxiliary circuit whose-plate circuit is connected to-the positive 13 battery by resistance lfiand wire 18. The filter 13 whenproperly adjusted willstop the desired tuned in or 'select'edi wave length in. the receiving' circuit and at the same time allow the disturbing influences and oscillations t'o beimpressed uponthe-grid of the tube 10 by wire 9. These will in turn be amplifiedainthe plate circuit of tube 10in such'mannerthat their relative phase an le andamplitudewill cancel and eliminate lilie. and corresponding impulses and oscillations in the grid circuit of tube 1'. I

Fig. 9 shows a somewhat similiarar-rangement with. an: amplifying radio frequency tube 10 in the local circuit with the filter 13.

Fig. 10 is a detail arrangement of a filtering device which consists of two parallel resonance circuits in series comprising the inductances13 and 14 respectively connected in parallel with condensers 5 and 6. The wire 8 connects the two units in series. variable condenser 3 is preferably used to control the amplitude of the oscillations that are permitted to pass through the filter. If desired the condensers 5 and 6v may be on the single shaft for operating the tuning condensers in unison.

Fig. 11 shows another common form of receiving circuit to which the invention is applied. The auxiliary cancelling or filter circuit includes aradio frequency amplifying tube 10 and also a local oscillator 11, the oscillations of which will be modulated by the oscillations or disturbing frequencies which are not stopped by the filter. These modulated oscillations are detected and amplified by the detector 10 and the circuit is connected to the differential winding 5 of the transformer T through the differential winding so that the frequencies of the oscillations will be of the opposite phase or polarity as in the other figures described.

In the construction shown in Fig. 11 in which a local oscillator 11 is used in the cancelling or filtering circuit it is possible under certain conditions to dispense with the filter as the oscillator can be arranged to accomplish the results desired without the necessity of the filter. This would be particularly true in the broadcasting band now in use of from say 200 to 500 meters. The oscillator would be adjusted to a comparatively low radio fre uency, or say a frequency of 20,000 cycles an if the incoming or selected frequencies were of the nature of 600,000 cycles or an equivalent wave length of 500 meters,

this would have a negligible efiect in modulating the frequencies of the oscillator as any one cycle of the 600,000 would have approximately .03 of the 20,000 cycle frequency that i it could possibly modulate.

The disturbing frequencies of audio frequency will modulate the oscillations of. the

oscillator and can be combined with the receiving circuit in the manner before described to eliminate these modulated fre-' quencies from the circuit of the receiving set.

This is particularly true also of such disturb-' ances as come from the beat note or heterodyning of two broadcasting stations of different frequencies. With this arrangement the local oscillations modulated by the dis turbing oscillations would be impressed upon the receiving circuit and cancel corresponding frequencies and oscillations in the main or receiving circuit.

Fig. 12 shows another conventional form of circuit with two amplifying tubes 10 and 11 in the auxiliary or filter circuit. These tubes "represent a-resistance coupled amplifier with tuberll 'functioning as a detector. 15 represents aapotentiometer which is connected to a C battery 16 in the usual manner. The "operation so far as the filter and eliminatingfunction of the circuit are concerned are similar to those already described. It will be seen from the above description that the inventionherein described for eliminating'all of the oscillations or disturbing frequencies except the one to be received which is stopped by the filtercircuit is readily adapted'to various forms of circuits in apparatus now inuse, I

It will be understood that the various circuit drawings are merely typical and are not intended to show all the various refinements used in. present-.wirelesssets, which may be readily applied withoutin any way-interfering with the operation of thefilter or cancel-.

ling circuit which will permit all undesirable frequencies to pass through the said 131- tering circuit with an opposite phase or polarity from those in the main receiving, circuitand cancel the same whilethe main or desiredfrequency to be received is not permitted to. pass through the filtering circuit and consequently will be the only one which will pass through the main channel 'ofthe receiving set andtothe translating device and with the elimination of all disturbing frequencies.

The term lfilter as usedin these specifica-' tions and claims'is meant to describe any circuit such as.parallel resonance, or any combination of inductance, capacity, reactance, or resistance that can be adj usteo, or connected so as to oppose, and prevent the passage of a single frequency only, and at the same moment offer a minimum, or zero resistance or reactance to, and permit the passage of currents of all other frequencies. The circuit of the filter shown in the vario-us'drawings isconventional, and any one of many Well known combinations may. be used.

.Having thus described my invention, I claim:

1. In a wireless receiving set, a filter circuit having means to reject a given frequency and permit otherv frequencies to pass, said filter circuit being connected at one end to the plate circuit of a vacuum tube in the regular receiving circuit and at the other end to the grid circuit of said tube, means for changing the phase of the. frequencies or oscillations passing through the filter circuit and means in the filter circuit for bringing the filter into resonance with any desired frequency which will thereupon be stopped by said filter and impressing the other frequencies in opposite phase upon the regular receiving circuit whereby undesirable frequencies wil be cancelled and eliminated.

2. In a wireless receiving circuit having an amplifying tube, an auxiliary circuit in a shunt around said tube including a filter with,

means to bring the same into resonance With any desired frequency, the connections to said auxiliary circuit being such that frequencies impressed thereon Will be of opposite phase from those in the vacuum tube whereby undesirable oscillations or disturbing frequencies Will be cancelled. r Y

,3. In a Wireless receiving circuit having a vacuum tube amplifier, an auxiliary filter circuit connected from the plate to the grid side of said tube With means for stopping the passage therethrough of any given frequency With the free passage for other frequencies of opposite phase to those passing through the amplifying tube whereby disturbing influences Will be eliminated or cancelled by impressing upon them similar frequencies of like characteristics but of opposite phase.

4:. In a wireless receiving set a thermionic tube, an auxiliary circuit from the plate to the grid of said tube having a variable filter Which may be brought into resonance vvith and prevent the flow of a given frequency While all other frequencies pass uninterruptedly therethrough, means for bringing the frequencies passing through the filter circuit into opposite phase from those passing through the tube. and amplifying devices in'said auxiliary filter'circuit.

5. In a system for receiving Wireless s1gnals having a termionic tube, an auxlhary circuit from the plate to the grid of said tube with co-nnecti'onssuch that the frequencies passing through said tube shall be impressed upon the auxiliary circiut in an opposite phase, a local oscillator in said auxiliary circuit of a comparatively loW radio frequency which will be modulated by the disturbing impulses Within the range of audition and impress these modulations upon the receiving circuit so as to cancel corresponding or like oscillations or impulses in the main circuit.

(5. In a Wireless receiving circuit havinga vacuum tube, an auxiliary filter circuit connected from the plate to the grid side of said tube, and a transformer With its primary connectedto the plate of said tube With its secondary Winding included in the auxiliary filter circuit to change the phase of the oscillations passing through said filter circuit to cancel like oscillations in the main receiving circuit.

In testimony whereof, I have hereunto set.

my hand this 18th day ofAp-ril, 1928.

WILLIAM M. BRUCE.

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