US1888536A - Radio receiving system - Google Patents

Description

Nov. 22, 1932. L. LEVY 1,888,536

RADIO RECEIVING SYSTEM Filed Oct. 3, 1927 'I I I M I Lie Patented Ndv. 22, 1932 UNITED STATES PATENT OFFICE.

v LUGIENLEVY, or PARIS, FRANCE.

RADIO RECEIVING SYSTEM Application filed'October 3, 927, Serial no. 323,762, andin Franee=ctobcr 22,1926.

I My invention relates to an improved meth 0d and apparatus for receiving electric signal bearlngwaves, especially high frequency waves used for telegraphic andtelephonic 5 purposes.

It concerns more particularly the receiving method based on the use of beats between two waves and chiefly those of the superheterodyne type and the like. 'It is known that such methods are based on the changing of the frequency F of the incoming waves (which will be hereinafter termed primary frequency) into a frequency f, which will hereinafter be termed secondary frequency,

which latter frequency is produced at the receiving station. 7

There are two main methods for changing the primary frequency into a secondary frequency f the first consists in producing and then detecting beats at secondary frequency due to the superposition of the incoming waves having a primary frequency F with a wave produced at the receiving station and having a frequency F f, forinstance. The

tained through one single adjustment, the

sensibility and selectivity, however, being as high as in the receivers with two adjusting means. i f It consists-in modulating at the secondary frequency f*(or at a frequency which is a multiple ora sub-multiple thereof) a current having a frequency equal to .the primary frequency Fand produced by a local generator, the current thus modulated being then superimposed on the incoming waves received by the aerial and the frequency of which it is desired to change in view of producing beats at the secondary frequency, these beats being finally detected so asto produce a current at secondary frequency, which, if desired, may be subsequently'amplified.

The modulation of a frequency f or nf (n being an integer which may beequal to 1) of the local current provides currents having a frequency F+nf and F When these currentsare superimposed on the currents received through theaerial and havinga frequency F, beats'having. the frequency 5 second method consists in modulating at secnf are obtained, which beats may be detected "15 so as to produce current at'this same frequency nff v Thus, the superimposition of the local Wave and of the incoming waves produces beats or surges at secondary frequency just ondary frequency the currents at primary fre quency received through the aerial (antenna or coil antenna) and in then detecting the primary current, thus modulated, in order to make the second frequency appear. 9

The first method providesa great sensitivity and a great selectivity, butit requires the tuning of two circuits to different frequencies viz: the tuning of the aerial to the frequency F and the tuning of the local circuit producing current at the frequency F f.

According to the second method, the circuit producing'modulating currents atthe frequency 7 may be adjusted once and for 40 all. Only the aerial circuit is to be tuned.

However, the method does not allow any selectivity; any undesired wave at a frequency F sufliciently near F to allow its reception through the aerial is transformed into a wave having a frequency f acting on the receiver;

moreover, no heterodyne being used, the efficiency of the transformation is very small.

The method according to my invention combines the advantages of-the preceding are retained.

as in the superheterodynemethod, whereby the sensitivity and selectivity of this method On the otherfhand, it is no longer necessary to provide for two adjustmerits since the oscillating circuits ofthe local generator and the receiving circuitsmust al ways remain tuned to thesame frequency F of the incoming waves; it is easy to reach this result by giving to the inductances of both circuits'equal values and by also giving to the capacities values always remaining equal to each other. A very simple form of execution consists in using inductance coils I of unvariable' value, which have been adjusted once for all, to give to the self induction of 5 methods and allows the reception. to be .ob- I have describedhereinbelow by way ofiex- 10Q ample and shown on appended drawing a form of execution of my invention.

The apparatus is constituted by three vacuum tubes 1, 2, 3 each having a filament, grid,

and plate, of the well-known type. The filaments are heated by the battery 13 whose an oscillatory circuit 11 connected to thez inrput of the. amplifier 12. These oscillatory '1 circuits andthe amplifier are tuned to the fixed secondary frequency.

The vacuum tube 1'. is coupled and operated asa generator in an oscillating circuit, constitute'd by the inductance 18' and the condenser 19, inserted between the grid: and the plate, one'en'd of the filament being connected with awconveniently'chosen point of the inductance 18, the plate of said tube being connected to the positive pole of the battery 15 through the intermediary of the choke coil.'9. Be-

tween the plate and the oscillating circuit, is

inserted the condenser 23- which prevents the battery 15' from being short-circuited by the inductan'ces9 and 18.- The oscillating ci rcuit .18 19 is adjusted once for all in such manner that the oscillations generated by the tube 1 .haive:.the:- fixed secondary frequency. The

vacuumtube 2 is coupled to operate. in the same manner, its oscillating circuit being constitutedby the inductance 7 and the condenser 21; the plate 20 of said tube being connected, by the intermediary of thechoke coil 8, to the platecircuit of tube 1; thus, the potential. of the anode 20 is provided by the tube 1 and therefore oscillates at the fixed secondary frequency Between the plate 20 and the oscillating circuit 7 21,'a condenser 2 4 is provided, to prevent the shortcircuiting. of tube 2 by the oscillating circuit,

and thus to prevent the oscillating currents generated by the tube 1 from passing by the inductance 7 instead of passingacross-tube 2. The oscillating circuit 721 is adjusted so ast'o produce, when there is no modulation current, oscillations at the frequency to which thereceiving circuit 4 5 of the detecting tube is tuned. V

This equality of adjustment is obtained by the fact that the self inductances of the coil 1 '7 and of the receiving'circuit 4, 6 have the same" value and that the two condensers 5 21'are' identical, the rotors being .con- "'nected toeach other and controlled by a single knob 22'. v.

The inductance coils 6 and 7 ma be adjustably coupled together. The cho e coil 8 is adapted to prevent the high frequency ostime the anode is broughtto a negative volt- 7 age, the frequency of these impulses being F +2 and F2f. These currents produce induced. currents in the circuit 45 byrreason of the coupling; 6-7 and. thereforeibeats are produced. in thiscircuit. Thus, after 'detection through the tube 3, there is produced in the anode circuit of the said tube three currents at a frequency 2 kilocycles in the case of the examplechosen), to which frequency the said: anode circuit is'tuned. This circuit is coupled withthe circuit 11 tuned tothe frequency 2f and connected with the amplifi'er'12 also-tuned to the same frequency. The currents having: a secondary frequency 2/ are then. either used directly or transformed by a further detection and, if. required, a second heterodyning, intocurrents of low frequency. v

The above described system is giverr'only by way of example and it is possible without widening the scope: of the invention to modify it for instance in the following man ner.

It has been assumed that the secondary frequency is inaudible, but the method is applicable also when this frequency is audible.

With the connections shown, the superimposition of the waves having frequencies F,

-F+2f and F 2f is madein the circuit conmeeting the aerial with the tube 3, but it might be made in the anode circuit by any known and suitable anode modulating methods, the vacuum tube being provided, if required, with a second grid or anode. V

The connections shownprovidefor the modulation at frequency f through the interruption of the current at a frequency F produced by the tube 2, but it is obvious that this modulation may be produced just as readily by connecting the anode of tube 2 to asuitable battery. This would afford areal modulation without any interruption of the anode current but the frequencies acting on' the incoming waves would then be F f, and F-l-y instead of F2/"f and F+2fa What I claim is: 7 i v 1. Themethod of superheterodyne radio receiving, comprising tuning the antenna circuit'to a given frequency, generating local oscillations at the frequency of the incoming oscillations, generating local oscillations'at a secondary frequency, superimposing said second local oscillations on said first-mentioned local oscillations, combining the composite oscillations thus produced and the incoming oscillations by demodulation, to produce a beat frequency and rendering audible the beat oscillations thus produced.

2. A radio receiver of the superheterodyne type comprising an adjustable receiving circuit, a first vacuum tube, an adjustable oscillatory circuit, means to connect said tube and said circuit in order to generate waves at the natural frequency of said circuit, common means to tune at the frequency of the incoming waves, said adjustable receiving circuit and said oscillatory circuit, a second generating tube, nonadjustable means to cause said tube to oscillate at a predetermined secondary frequency, means to modulate the waves generated by the first tube by the waves generated by the second one, means to sunerimnose said modulated waves on the incoming waves received by the receiving circuit. and means for detecting the beats produced thereby.

3. A radio receiver of the superheterodvne tvne comprising an adiustable receiving circuit. a first vacuum tube. an adjustable oscillatory circuit. means to connect said tube and said circuit in order to enerate waves at the natural freouen cv of said circuit, means signature.

LUCIEN LEVY.

to give the same inductance to the receiving 7 and oscillatory circuits. two similar adjustable condensers. a common shaft for the rotors of said condensers. a knob actuating said shaft. means to connect each condenser one in the receiving the other in the oscillatory circuit to cause their natural frequencies to keen always eoual values. a second generatin tube. nonadjustable means to cause said tube to oscillate at a predetermined secondar frequency. means to modulate the waves generated by the fir t tube b the waves generated bv the second one. means to superimnose said modulated Waves on the incomin waves received by the receiving circuit. and means for detecting the beats produced thereby.

4. A radio receiver of the superheterodvne tyne comprising an adjustable receiving circuit. a first vacuum tube, an adjustable oscillatory circuit, means to connect said tube and said circuit in order to generate waves at the natural frequency of said circuits.

common means to tune at the frequency of the incoming waves said adjustable receiving circuit and said oscillatory circuit, a second generating tube, nonadjustable means to cause said tube to oscillate at a predeter mined secondary frequency, means to feed the anode of the first vacuum tube by the current generated by the second tube, means to superimpose the modulated waves generated by the first tube on the incoming Waves received

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