US2039657A

US2039657A - Supersonic heterodyne receiver

Info

Publication number: US2039657A
Application number: US710804A
Authority: US
Inventors: Osborne Charles Percy
Original assignee: EMI Ltd
Current assignee: EMI Ltd; Electrical and Musical Industries Ltd
Priority date: 1933-02-13
Filing date: 1934-02-12
Publication date: 1936-05-05
Anticipated expiration: 1953-05-05

Description

May 5, i936.

C. P. OSBORNE SUPERSQNIC HETERODYNE RECEIVER F11ed Feb. 12, 1934 2. sneets-shet 1 www# INVENTOR CHARLES OSBORNE May 5, g. C P, QSBQRNE Zgg? sUPERsoNIc HETERODYNE RECEIVER Filed Feb. l2, 1954 2 Sheets-Sheet 2 INVENTOR ATTORNEY CHARLES P. OSBORNE i* l'ie'terodyne receivers for vwireless-or like reception.' In'recei'vers 'offthisrkindI anfincoming carrier,"

"modulated iwithA Aafsignail,"and of a frequency-' "which willhereina'fter b'e referred to asthe :signal frequency, is caused tobeat with-a locally'gen-"- `erateld oscillatipnithe'frequency of which will bef1 calledthe oscillator'frequency, and the result- Patented May 5, 1936 STATES Pirl-#EN'rful foFFflcE 2,039,657 "sUPRs'oNIc l"HETERODYNE" vRECEIVER 7 Charles'fPercy Gsbcrne,E Hillin'g'don,"England;`as

. 'sig'nor tol Electric and Musical Industries'Lim- 'ited,y Hayes, England, a. company of Great Britain l'^'A''prilicatiorrFebruary 12;; 1934;?Seri'al Nef-'710,804

l" In Great BritaiFebllaiy- 13,1933

comms. (ci. y25W-,20)

'The*present*"inventionrelatesto kv'supersonicf-F""generating*oscillations of-*the""`oscil1ator ire- "que'nc'y ffolareffed to lrs't detector v4 for beats aiedet'eotedandfed to the input ofiv an intermediate frequency amplieri'tunedto the beat or'Aintermediate `frequency. The `output w fa;rv 'further2 amplirfl provided? vfor amplifying the modulation frequencies. v A

*The -wliole ora part of the-output voltage of from this* amplifier isrectified in :a second de-f'jfthe intermediate frequency amplifier 5 -isapplied tector tcryield4` the signals.

to variations injthe' oscillator frequency. Quite f betweentl'ie-control grid 8 and the cathode 9 of 'Difficulty isexperiencedparticularly with rean' auxiliary'therniionicfvalv I0; -that 'is to say, ceivers suitable" for ultra-shortv Wave working in foscillatioris of?aifre'qui-iificyv f1 are? produced in the which-the' signal frequencies are very high; due control g'rid"circuit of this Valve. The control gr'id 8fisgivenasuitablenegative biasing potenrise to af'ver'y'large percentage change in the 'jintermediate frequency. Another difliculty 'met --with isthe extreme sharpness Withwhich cir-4 cuits tune tothese high frequencies.

:a small change in the oscillator frequency gives,

One Way in-which thesedifliculties have been 'idealt'with hithertoI is bygiving the intermediate'- 'ffr'equency amplifier 'a band-pass characteristic- =-'which is-muchwider than would normally bear' desired. For example, when receiving a signal: l.

"-" frequency of 90 megacycles/sec." modulated with frequencies up to`5,'000 cycles/sec., the band width-y f fmay beinade lokilocycles/sec. thus permitting a drift of 90 kilocycles/sec. which is'still only one part in a'thousand andrmaywell happen in It is an-object ofthe present invention to provide means for improving the constancy of the oscillator frequency. c vAccording to the present invention, a super-1y "sonic heterodyne receiverlis provided' with means fr generating a harmonic of the intermediate` frequency and'means for utilizing this harmonick Y to Areduce variations in'` the loscillator frequencyf' AThe inventionv will bel described by way of example `With"reference to 'the '21.c'coinpanying'v drawings', whereinvFig. 1' shows one embodiment of "the'f vinvention;"Figa 2 showsanotherform' yvheterodyne receiver Acomprises a grounded ante-n-4 na'circuit l feeding anamplilier 2; tuned to the '-55i`a'inplier 2y and from"the'rmionic means 3' fori vReferring to-'Fi`g."1 of 'thedrawings a Superfy signal vfrequency (fs). "I'he outputsffrornr thel tial'relatively'tothe cathode 9 by means of a battery- I I,"forf"example. Between "the screening gridfIZ'aiidvcathode Blof thev'alve lll is' arranged apa'rallel'resonant circuit`l3'tuned to a harmonic of f1; namelyl a"frequency mf1,"wher'e m is an integer.ff"-The1 screening f' grid I 2 is maintained.

at :va-suitable' positive potential withrespect to f they cathode 9; The anode I4 of the valve is con- 'l nected 'to' itsl cathode through a parallel resonant circuit I5''tuned tothe` oscillator frequency fo, anda-source "|36 of anode current in series. The

*frequency ifo is made Aequal' to a harmonic of f1 so`fthat'^f=Kf1'where K is an integer, and 'vKnmj-'where n vi's aninteger.' The valve l0 '-thu'sgenerates "arid selects the mth harmonic of fi" in' its screen-grid-lcathode circuit and the "-'nth harmonic of this mth harmonic of f1 in its anode-cathode circuit; the overall result being a lgeneration in the anodeecathode circuit of the `-Kth `harmonic offthefrequency applied to the control grid circuit. i-Theresonant circuit l is -coupled in: the arrangement illustrated to the oscillatory circuit Il ofthe oscillator 3, and the arrangement is suchthat Vthe coupling between 4the anode-cathodelcircuit of the-auxiliary valve "pose ifo" changes to (l-l-mfo Iiilhere'a, is Va posi- "tive 'oi' negative fraction, vthen" the change in fn is l lpztjnfthecha'nge in f1 is '-wfu 'and the change in jthereof;"'Fig. S'sliows still anotherv modification*`vv l valve islKafo.' 'Thus echange in frequency of 'thefcontroll frequencydelivered by the auxiliary theffoscillator yoffiii-ajn is `acc-omplar'iied`I by a 'chan' v ,off-#Kafq inithef control frequency; that is ftof'say the ontrolfffrequency changes K times a'senuch in'iftheopposite-senseg-and by suitable cycles/sec.

coupling can therefore be made to prevent changes in oscillator frequency.

In one example f0=36 and f1=6, both in mega- In order to obtain a control frequency from ,f1 it is therefore necessary to select the 6th harmonic (K=6) and this may be done, for example, by generatingand selecting the 3rd harmonic of f1, that is 18 megacycles, in the screen grid circuit of the auxiliary valve (171:3) and byV generating the second harmonic of18 megacycles, that is 36 megacycles, in the anode circuit (11.:2) In this case any change in oscillator frequency is accompanied by a change in the control frequency of six times the amount in the `opposite sense. Y

In a modified receiver according to the invention, as shown in Fig. V2, the functions of the oscillator valve and the auxiliaryrvalve are performed by a single valve 20, which may be a so-called heptode in which five grid electrodes are arranged between the cathode and an anode.l

In such an arrangement, the second grid 2|, if

connected to the cathode through a resonant circuit 22 tuned to the oscillator frequency, in series with a source of anode current 23 and the circuit ofthe first grid 24 includes av coupling Y coil 25, the first and second gridsco-operating with the cathode to generate Vthe oscillator frequency.

The third and fifth grids are connected together, and the anode 26 is connected to the cathode through a circuit 21 coupled to that in Y the second grid circuit and tuned to the same frequency, that is, the oscillator frequency, .and the source of anode current in series. YThe whole or a part of the outputvvoltage of the intermediate frequency amplifier is applied between the fourth grid 28 and the cathode, and the third and fifth grids are connecte-d through a circuit 29 tuned to a multiple of the intermediate frequency and a` sub-multiple of the oscillator freoscillator frequency should be as weak as pos- Y .a dynatron oscillator.

In an alternative arrangement shown. in Fig. 3

in which a single valve serves both as the oscillator valve and as the auXiliary'v-alve, a thermionic tetrode 30 is so connected as to function as The potentials applied, relative Vto the cathode, to the anode 3| and screening grid 32 are so adjusted that the anodecathode path of the valve has a negative resistance characteristic. oscillations at the intermediate frequency are fed to the control grid circuit, andthe screening grid circuit comprises a resonant circuit 33 tuned to a harmonic of this frequency. The anode circuit comprises a circuit 34 tuned to the oscillator frequency, which is arranged to be a harmonic of the frequency of the oscillations generated in rthe screening grid circuit, and the oscillations generated in th anode circuit are fed to the first detector.

The resonant circuits in which the harmonics of the intermediate frequency are generated should, in all cases, preferably be of low decre-V ment in order that substantially only the desired harmonic frequencies are generated. By making these circuits sharply tuned, the tendency for the oscillator frequency to be affected by harmonics of frequencies occurring in the intermediate frequency side bands is prevented.

The invention is of particular value in the case of apparatus adapted for the reception of signals representing a picture or scene and a sound accompaniment, in which the two sets of signals are transmitted at different carrier frequencies, and in which a single oscillator is used to provide both intermediate frequencies.

Where it is desired to makeV the receiver tunable over a range of signal frequencies, means may be provided whereby the circuits tuning to the frequencies fs and fo have their resonant frequencies changed simultaneously in the proper proportion by theactuation of a single control member 35. Thusthe circuit tuning 'to .fs is made to be resonant always at a frequency (1+ K) times the frequency to which the intermediate frequency amplifier is tuned and, of course, the oscillator frequency is maintained equal to Kfi.

I claim. 1. The method of maintaining a receiver of the heterodynedl type in tune to the received wave which includes thel steps of, beating said wave Y with local oscillations to produce oscillations of a difference frequency, multiplying said oscillations Yof a difference frequency and entraining said 1o"- cal oscillations with said multiplied oscillations.

2. The method of'maintaining a receiver o f the heterodyned type in tune to the received wave, which includes the steps of, beating said received Wave with local oscillations to produce oscilla'- tions of an intermediate frequency, increasing the frequency of said intermediate frequency oscillations to a value substantially equal to the fren quency of the local oscillations and superimposing said oscillations of increased frequency on said local oscillations. Y

3. The method of reducing the amount of shift produced in the intermediate frequency of a receiver of the heterodyned type when the received wave shifts in frequency, which includes the steps of, beating said received Wave with local oscillations to produce oscillations of an intermediate frequency, multiplying the frequency of said intermediate frequency oscillations to a value substantially equal to the frequency of the local oscillations and entraining said local oscillations with said oscillations of multiplied frequency.

4. In a heterodyned receiver, the combination of a first detector responsive to signal waves to be demodulated, an oscillator coupled to said first detector, a utilization circuit coupled to the output circuit of said first detector and a frequency multiplier having its input circuit coupled to the to a frequency bearing a predetermined harmonic relation to the oscillator frequency and the rst detector output circuit frequency, and said multiplier input circuit being connected between the grid and cathode.

6. In a. receiver as dened in claim 4, said multiplier including a screen grid tube, and a. resonant network connected between the screen grid and output circuit of the multiplier tube which is tuned to a. frequency bearing a. predetermined harmonic relation to the frequencies of the oscillator output energy and the rst detector output 5 energy.

CHARLES PERCY OSBORNE.