US2452811A

US2452811A - Frequency divider

Info

Publication number: US2452811A
Application number: US542950A
Authority: US
Inventors: George L Usselman
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1944-06-30
Filing date: 1944-06-30
Publication date: 1948-11-02
Anticipated expiration: 1965-11-02

Description

Nov. 2.,'1948..

3. l.. ussx-:LMAN

FREQUENCY DIVIDER 2 Sheets-Sheet 1 Filed June 30, 1944 Y .T B c w. @Il M 31230.@

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f ,0o/.iI 9 Y a R 2. 7/ .ad I.. l Rw F Cw INVENTOR.

ATTOGNEY GEORGE L. UESEL MAN BY i 7%@ CONTROL FREQUENCY SOURCE Nov. 2, 1948. y G. L .Yus'sELMAN 2,452,811

FREQUENGY DIV-Ilma4 Filed June so, 1944 2 sheets-snm 2 L 4 ,70 -t OUT/07. FREQUENCY /6 Mom/A750 -'r l .SOURCE i i 9 5E E 49 A, v i; /4

OSC/L [147/0 GENERATOR :llllil IVEN TOR. 650,965 L. wsa MAN atented Nov. 2, 194g U N IT ED- STATES Lezen y TENT OFFICE FREQUENCY DIVIDEE 1mi-ationl of Delaware Appiicationzdune Sil., 1944Serial No. 542,950

12 claims. 1

This invention relates to frequency divider circuits and is adapted for general use in various electronic devices ng monitoring circuits, frequency modulation fansmitting apparatus, and also frequency modiylation receivers.

It is an object of my inventionto provide a. frequency divider capable'of control by an eX ternal source of alternating current where .such source is that of a constant frequency oscillator or a modulated wave.

It isv another object of my invention toprovide a frequency divider suitable for use in monitoring a high frequency alternator.

Still another object of my invention is toprovide a frequency divider having general utility, such, for example, as in a monitoring system for a frequency modulation transmitter, or :again in a heterodyne receiving circuit for frequency `modulated waves..Y

Other objects of my invention.. willbe inferentially brought out in the specication to follow'. Essentially this invention comprises a frequency divider circuit arrangement wherein the divided frequency output. is controlled by a harmonic frequency input which may .be either constan-t .or Variable within a desired range of 4modulation frequencies.

My invention will now be described .in more detail, reference being made to the accompanying drawings, in which; i

Fig. 1 shows a circuit arrangement having elec;- tronic means controlled by an external source of. alternating current and further electronicmea-ns coupled thereto for. producing a sub-harmonic frequency output; and

Figs. 2, 3, 4, and show alternative circuitar rangements for carrying out the objects of my invention.

Referring first to Fig, l, I show therein a discharge tube l having two triode sections.. .The left-hand section includes anode 2 and .control grid 3; the rightehand section includes anode. 4 and control grid 5. The cathode 6 is .common to both sections. A source of alternating .current control potentials 'i' is indicatedas avmaster oscillator. In piace of such an oscillator, "however, any suitable source of control potentials, Whether constant or variable, may be used. A1 ternative types of control potentials aregtherefore, indicated as derived from units la, lb., lc, and 'ld in the different figures of. the drawing.. The output of the source l is coupled across capacitor 8 tothe input circuit for the 'left-hand. section of tube i. This input circuit includes. a resistor 9 connected between the control grid 3 and ground.

The right-hand section of tube i has its control grid 5 connected to ground through resistor it. There is a common cathode circuitv impedance connected to ground, `thisy impedance including instable by .means of a. potentiometer I6. potential is fed to` the anode i through one partv preferably an inductance H in series with aresistor A capacitor i3. is in shunt with .resistorlZ. y

Anode potential is supplied to the twoy anodes 2 and, 4, from asource of directcurrent B. This source is. bypassed. for alternating current by capacitor Ul. Capacitor l5 provides an alternating current path to ground from the anode- 2. The D. C. potential for anode 2 is ymade adof the primary winding of an output transformer il.. .This primary has an intermediate tap. con nestedl to. the, battery circuit.

A variable capacitor i8 is in shunt with the primary winding of .transformer il and forms therewith. a parallel resonant circuit tuned to the divided frequency which is wanted for output. The secondary winding of transformer il. is connected to the. output leads. Feedback potentials are supplied to the grid 5 from the. lower terminal .of the resonant circuit, grid li being coupled thereto across capacitor L9.

`In .the operation of the. circuit arrangement shownin l,v input potentials` of the control frequency are supplied to thegrid 3. Theleft hand section. of tube l operates as an amplifier. I t ydevelops variable potentials on the cathode 6 due. to the. impedance of' the circuit betweenl thev cathode and. ground.` Since cathode E is common. to both sections ofthe tube l, control potentials are. vapplied to the right-hand section of this tube. which cause its oscillations to be locked in step. with. the .frequency of the ex.-

ternal source.. Therightfhand section of tube I' is, however, included in a resonant circuit tuned to the. divided frequency, and for this reason the output frequency isy maintained in predetermined subeharmonic. relation to the input frequency; The iunction of thev inductance ll will be readily understood, therefore, as that of a.

sharpenthe peaksofthe amplifier current. so as toY increase. itsv eiciencyas a frequency controllingmeans.

The circuit arrangement shown .in Fig. -1 has.

been found to possess. very desirable. operational characteristica since. the. snb .harmonic.frequency of, output'lis. readily lockedin. step Vwith thereonY trolfrequencmeven. though such. frequency bears a harmonic/relation ,.thereto.,

"Referring to .Eig...2, the. modification therein shown includes a discharge tube 2l having a trias an amplifier.

Oscillations are generated in the right-hand section of the tube 2| where the anode 4 is in circuit with a parallel resonant circuit composed of the primary Winding in transformer I1 and the adjustable capacitor I8. The control grid derives feedback potentials from the resonant circuit, these potentials being fed through capacitor I9 to the grid 5, the same as in Fig. 1.

The pentode tube section includes a screen grid 22 connected to the anode 2 of the triode section, and a suppressor grid 23 connected to the common cathode 6.

The other components of the circuit arrangement of Fig. 2 are similar to those having the same reference numerals in Fig. 1 and need not, therefore, be further described. The functions of the screen grid and suppressor grid in the pentode section are conventional. However, the connection of the screen grid 22 to the anode 2 constitutes a cross-coupling means between the two sections of tube 2| and this adds to the crosscoupling effect which is inherent in the use of l a common cathode. It should be noted, however, that in the circuit arrangement of Fig. 2 the inductance II of Fig. l has been omitted. There is, of course, a certain amount of voltage swing in the cathode 6 of Fig. 2 which results from the presence of the cathode resistor I2 in shunt with the capacitor I3.

The circuit arrangement shown in Fig. 3 is somewhat similar to that of Fig. 2. The functions of the control grid and the screen grid in the right hand section of tube 3l of Fig. 3 are reversed, however, with respect to the functions of these grids in Fig. 2. That is to say, control grid 5 in tube 3I is capacitively coupled across condenser 33 to the anode 2 in the amplifier section of this tube. The screen grid 32 derives feedback potentials from the parallel resonant circuit composed of the primary in transformer I1 and the adjustable capacitor I8. The feedback circuit includes capacitor I9 in shunt with a resistor 34,

which supplies positive bias potential to the screen grid 32.

The cathode impedance 35 (in shunt with capacitor I3) is in the form of a voltage divider having a tap 36 thereon which connects through a re.. sistor 31 with the positive terminal of the D. C. source B.

In the operation of the circuit arrangement shown in Fig. 3, input potentials are amplified in the left-hand (triode) section of tube 3| and are applied as control potentials across capacitor 33 and resistor I0 to the control grid 5 in the right-hand (pentode) section of tube 3l. This pentode section is in circuit with a parallel resonant circuit which is tuned to the sub-harmonic frequency of the input potentials and produces the desired sub-harmonic frequency, although this frequency is locked in step with the input frequency. The operation is, therefore, quite similar to that of the circuits shown in Figs. Y1 and 2.

In the circuit arrangement of Fig. 4, I show a discharge tube 4I comprising a pentode section and a triode section. For generating sub-harmonic frequency oscillations the two tube sections (or their equivalent) are disposed in a cascadeconnected circuit. In tube 4| there is a common cathode 6. In the left-hand section, I show a control grid 42, a screen grid 43, and a suppressor grid 44. In the right-hand section of tube 4I, I show anode 4, and control grid 5. Other cornponents of the circuit arrangement shown in Fig. 4, if they correspond with components of the figures previously described, are given like reference numerals.

A capacitor 41 is disposed in a feedback circuit between the anode 4 and the control grid 42. Positive bias for the screen grid 43 is obtained by a connection through a portion of potentiometer I6 and resistor 45. The terminals of potentiometer I 6 are respectively connected to the anode 46 and to the positive side of source B. The anode 4 in the triode section is connected to the parallel resonant circuit composed of the inductance in the primary of transformer I1 in shunt with adjustable capacitor I8. This resonant circuit is, of course, tuned to the desired sub-harmonic frequency. The feedback voltages through

capacitors

33 and 41 are in phase opposition, and hence there is no need to develop a voltage swing at more than one end of the tank circuit` I1, I8. The screen grid 43 derives control potentials from the frequency stabilizing or frequency modulated source 1c. The operation of the circuit arrangement shown in Fig. 4 will be readily understood, since it will be seen that the two sections of tube 4I are cross-coupled so as to deliver feedback potentials from one to the other in phase opposition, and the frequency of the triode section is controlled by the resonant circuit. Furthermore, the pentode section, although aperiodic, is nevertheless locked in step with the input potentials derived from the source 1c.

Fig. 5 is similar to Fig. 4 with the exception that the functions of the first and second grids in the pentode section of tube 5 I are reversed as compared with their functions in Fig. 4. That is to say, the control grid 52 is coupled to the source of input potentials, while the screen grid 53 is coupled to the anode 4 in the triode section through capacitor 54 in shunt with resistor 55. The other components of the circuit arrangement are coordinated similarly to corresponding components in the circuit arrangement of Fig. 4, and need not, therefore, be described. The operation of the circuit shown in Fig. 5 will also be understood to be such as to lend itself to frequency stabilization in aV divider circuit arrangement.

I claim:

1. A frequency dividing circuit comprising two cooperating electron discharge devices, A and B, each having a cathode, an anode, and at least one grid, a common cathode impedance connecting said cathodes to ground, means including a source of direct current connected negatively to ground and positively to said anodes for producing electronic emission in said discharge devices, aperiodic input circuits connected between one grid of each device and ground, means including input terminals coupled to a grid in device A whereby the emission in this device is controlled by alternating potentials from a given source, a parallel resonant circuit coupled between the anode of device B and a point of fixed reference potential, said resonant circuit being broadly tuned to a band of frequencies including the output frequency from said dividing circuit, means coupling the output circuit of device A to the input circuit of the device B, and feedback means for coupling the output circuit of device B to a grid in device A, :said dividing icircuit .being `further characters ized :in that 'oscillations in the Itwo devices A and B fare Ymaintained Ain Aharmonic relation one zto the other.

2. .A frequency dividing` circuit according to claim 1 in which device A is of the pentode type; the first grid thereinlis coupled t0 the output circuit of device B; the second grid therein is biased as a screen grid and is controlled by alternating potentials from said .given'source `and the third grid is a suppressor grid.

3. A frequency divider circuit subject to control by alternating :potentials from an external source, said circuit comprising a pair of electron discharge devices each having a cathode, an anode :and'at least one grid, 'means for controlling the emission in the rstof said 'devices inacc'ordancewith the alternating potentials of said external source, a frequency determining circuit coupled to the anode in the second of said devices and to a point of fixed reference potential, an aperiodic input circuit connected between ground and a grid in each of said devices, and a common cathode impedance connected between said cathodes and ground and constituting means for locking in step the oscillations generated in the second said device and the controlled oscillatory emission in the rst said device, whereby the output from the second device is maintained in sub-harmonic relation to the frequency of said external source.

4. A frequency divider circuit according to claim 3 wherein said common cathode impedance possesses a frequency discriminating characteristic such that it oiers a relatively high impedance to the oscillatory potentials of the first said device and -a relatively low impedance to the oscillatory potentials of the second said device.

5. A frequency divider circuit according to claim 3 and including means for applying an adjusted D. C. bias potential to the cathodes of said devices with respect to ground potential.

6. In a frequency divider circuit to be controlled by oscillatory energy of fundamental frequency, a pair of electron discharge systems each including an electron source, an anode and a control electrode, biasing circuits connected between the electron source and control electrode ofv each system, connections to the anode and electron source of each system for maintaining the anodes electro-positive relative to the electron source, connections for applying said oscillatory energy to the control electrode of one system, a cir-cuit tuned to resonance at a sub-harmonic frequency coupled to the anode of the other system, connections to the electrodes of the other system such that the same generates oscillatory energy in said resonant circuit of a sub-harmonic frequency and a common impedance connected between the electron source of both of said systems and the .control elcetrode of both systems, said common impedance being high with' respect to current of said fundamental frequency and constituting means for locking in step the oscillations of subharmonic frequency generated in said second system and the oscillatory energy fed to the control electrode of said first system.

7. In a frequency divider circuit to be controlled by oscillatory energy of fundamental frequency, a pair of electron discharge systems each including an electron source, an anode, and a control electrode, biasing circuits including a common impedance connecting the control electrode of each system to the electron source of each system, connections to the anodeand electron source of each system for maintaining the s. ane'des electro-'positive relative itc the electron source, iconnections for app'lyring :said oscillatory energyito ithe icontrol electrode .of ione system, .a circuit :tuned to :resonance at :a sub-harmonicirequency f'coup'led to iihe anode of itheother system, a freed back coupling :between Asaid :resonant .cin cuit and fthe control Aelectrode of said other oi said .systems .such that pscillaticns of ysaid subharmonic frequency :are generated in said resonant circuit, said common impedance constitutine 'mearrsifo-r locking :instep the 'esciua'uonsfgem erated iin said .second fsyste'm `and the fo-scillato-r'y energy fed to th'e fco'ntrol electrode of said first system.

al. .iA @frequency divider as recited in claim `6 wherein :said `common impedance lis an finductor.

.9. A .frequency divider ias recited lin claim fl' wherein said common impedance is a resistor adjustably connected to a source of direct current.

10. In a frequency divider circuit to be controlled by oscillatory energy of fundamental frequency, a pair of electron discharge systems each including an electron source, an anode and a control electrode, an additional grid-like electrode in one of said systems, biasing circuits connected between the electron source and control electrode of each system, connections to the anode and electron source of each system for maintaining the anodes electro-positive relative to the electron source, connections for applying said oscillatory energy to the control electrode of the other of said systems, a circuit tuned to resonance at a sub-harmonic frequency coupled to the anode and additional electrode of said one system and a connection between the anode of the other system and said control electrode of said one system so that said one system generates oscillatory energy in said resonant circuit of a sub-harmonic frequency and a common impedance connected between the electron source of both of said systems and the control electrode of both systems, said common impedance being high with respect to current of said fundamental frequency and constituting means for locking in step the oscillations of sub-harmonic frequency generated in said one system and the oscillatory energy fed to the -control electrode of said other system.

11. In a frequency divider circuit to be con'- trolled by oscillatory energy of fundamental frequency, a pair of electron discharge systems each including an electron source, an anode, and a grid-like electrode, one of said systems having an additional grid-like electrode, lbiasing circuits including a common impedance connecting a grid-like electrode of each system to the electron source of each system, connections to the anode and electron source of each system for maintaining the anodes electro-positive relative to the electron source, connections for applying said oscillatory energy to a grid-like electrode of one system, a circuit tuned to resonance at a subharmonic frequency coupled to the anode of the other system, cross couplings between the anode of each system and a grid-like electrode of the other system, the arrangement being such that oscillations of said sub-harmonic frequency are generated in said resonant circuit, said common impedance constituting means for locking in step the oscillations generated in said other system and the oscillatory energy'fed to the grid-like electrode of said one system.

l2. In a frequency divider circuit to be controlled by oscillatory energy of fundamental frequency, a pair of electron discharge systems each including an electron source, an anode, anda control electrode, an additional grids-like electrode in one system, biasing circuits including a common impedance connecting thecontrol electrode of each system to the electron source vof each system, connections to the anode and electron source of each system for maintaining the anodes electro-positive relative to the electron source, connections for applying said oscillatory energy to the additional electrode of said one system. a circuit tuned to resonance at a subharmonic frequency coupled to the anode of the other system, a coupling between the anode of said one system and the control electrode of said other of said systems, a coupling between the anode of said other system and the control electrode of said one system, the arrangement being such that oscillations of said sub-harmonic fre- GEORGEV L.' USSELMAN.

REFERENCES CITED The following references are of record inthe le of this patent:

UNITED STATES PATENTS Number Name Date 2,269,417 Crosby Jan. 6, 1942 2,303,511 'Iawney Dec. 1, 1942