US2418568A

US2418568A - Frequency divider

Info

Publication number: US2418568A
Application number: US530503A
Authority: US
Inventors: Bauer L Brunton
Original assignee: Hewlett Packard Co
Current assignee: HP Inc
Priority date: 1944-04-11
Filing date: 1944-04-11
Publication date: 1947-04-08
Anticipated expiration: 1964-04-08

Description

pril 8, 1947. B. BAUER FREQUENCY DIVIDER Filed April 11, 1944 M In INVENTOR.

L. 5 Bauer BY p A TTOR/VE Y Patented Apr. 8, 1947 FREQUENCY DIVIDER L. Brunton Bauer, Palo Alto, Calif., assignor to Hewlett-Packard Company, Palo Alto, Calif., 21. copartnership consisting of William R. Hewlett and David Packard Application April 11, 1944, Serial No. 530,503

4 Claims.

This invention relates generally to electrical apparatus for producing a frequency of known value from a higher given frequency. More particularly it relates to so-called frequency dividers suitable for producing frequencies which can be used as standards for test purposes and the like. It is an object of the invention to provide apparatus of the above character which has a high degree of stability with respect to the desired output frequency.

Another object of the invention i to provide a frequency divider of simple construction which can be used to produce currents of frequencies over a wide range, including frequencies ranging from say '10 kilocycles to 100 cycles per second. A further object of the invention is to provide a frequency divider in which division by numbers other than integers is possible, that is one with which any desired ratio may be obtained as distinguished from prior art dividers which are limited to obtaining frequencies having an integralrelation with the driving frequency.

Further. objects of theinvention will appear from the following description in which the preferred embodiment of the invention has been set forth in detail in conjunction with the accompanying drawing,

The frequency divider illustrated in the drawing is adapted to be excited from a suitable oscillator I0, and is adapted to deliver a given lower frequency tothe output or load I I. The oscillator can be of the electronic type preferably with a crystal control to maintain its frequency constant. The frequency divider consists of a pair of vacuum tubes I2 and It, with tube I2 arranged to operate as a modulator with high amplification gain, and with tube l3 arranged to operate also as a modulator. Under certain conditions it may be desirable to also operate tube l3 with considerable distortion to act as a frequency multiplier. Both ofthe'se tubes are preferably of the 'pentagrid type, known by manufacturers specifications as No. 6L7. Thus each tube is shown provided with plate P, cathode K, and grids Gl, G2, G3, G4 and G5. GI and G3 are control grids, G2 and G4 are screen grids, while G5 is a suppresser grid.

In :order to form suitable input and output circuits for the modulator tube 12, cathode K together with the suppressor grid G5 are connected to the grounded conductor I4, through the biasing resistor Hi. This resistor is shunted by bypass condenser IT. The control grid GI is connected to ground through the biasing resistor I5, and is coupled to the oscillator Ill through the variable resistor I8 and condenser I9. Control grid G3 of tube I2 is also connected to biasing resistor 2|, and is coupled to the plate of the tube I3 through condenser 22.

The plate circuit or output of tube I2 is tuned by the inductance 23, which is shunted by condenser 24. One side of inductance 23 connects to the plate P of tube I2, while the other side connects with the load I I and plate current source 25 through conductor 26. Transfer of energy to the load I I occurs through the coupling condenser 27.

The cathode K of tube I3 likewis connects to grounded conductor 28 through the biasing resistor 29, which is shunted by by-pass condenser 3I. Control grid GI is connected to ground through the biasing resistor 32, and is preferably directly coupled with the oscillator Ill through the variable condenser 33, resistor I8 and condenser l9. Control grid G3 is connected to grounded conductor 28 through the biasing resistor 34, and is coupled through condenser 36 to the plate P of tube I2. Conductor 23 connects with the screen grids G2 and G4, of both tubes, through the resistors 3'! and 38. An additional biasing resistor 39 connects the screen grids of tube I3 to ground. The screen grids of both tubes are also connected to ground through the by-pass condensers M and G2.

The plate circuit or output of the tube I3 is tuned to a given frequency by the inductance 43 which is shunted by condenser 44. Conductor 45 connects one side of the inductance to the plate P of tube I3, while the other side of the inductance connects with conductor 25.

The biasing resistors and plate voltages for the tubes I2 and I3 are selected and adjusted so that tube i2 operates as a modulator with high amplification gain. Tube I3 may be adjusted to operate with considerably less amplification gain. Under certain conditions of operation, particularly where n is an integer, it is desirable to adjust tube I3 for a substantial amount of distortion, whereby it also operates as a frequency multiplier.

15 kilocycles.

3 The frequency delivered to the load I! must be f where is the frequency of the oscillator Ill. The filter formed by inductance 23 and condenser 24, is tuned to this frequency The filter formed by inductance 43 and condenser 44 is tuned to the frequency Assuming for example that the oscillator I operates at a frequency of 100 kilocycles and that an cycles are therefore fed back regeneratively from the output of tube I3 to the control grid G3 of tube l2, through the coupling condenser 22.

Assuming that the apparatus is in operation, currents at the frequency of 100 kilocycles are supplied by the oscillator II] to the control grid GI of the modulator tube l2. In this modulator the frequency of 100 kilocycles is mixed with the frequency of 85 kilocycles or 115 kilocycles being fed back from the plate circuit of tube i3, as previously described, whereby there is produced a, differential frequency of 15 kilocycles. Currents at this frequency are supplied to the load II, and they are also applied to the control grid G3 of the modulator tube l3, through the coupling condenser 36. Control grid GI of this modulator is also supplied with current directly from the oscillator 10 through coupling condenser 33,

thus causing production of a differential frequency of 85 kilocycles, to which the output of tube I3 is tuned. This as previously explained is then supplied to the input of modulator tube 12 to coupling condenser 22, to beat with the frequency of 100 kilocycles to produce the desired Production of the desired differential frequency of 85 kilocycles or 115 kilo- ,cycles in the output of tube I3 is also intensified because of the distortion for which the tube is adjusted.

No difiiculty is encountered in starting the ap-' paratus in operation because initial transient pulses are quickly built up by the regenerative action. The regenerative action is not to be confused with regeneration capable of sustained generation of oscillations, because when the supply of current from the oscillator I0 is interrupted the supply of current at 15 kilocycles or immediately stops.

Assuming that the oscillator Ill is designed to maintain a desired frequency, then my frequency divider is capable of producing a lower frequency of constant value and sinusoidal wave form which can be ,usedas a standard for test purposes and the like. Should one desire to produce currents .at two or more frequencies differing from each other by say multiples of 10, a number of such frequency dividers can be provided with currents from the output of one divider serving to supply exciting current to a succeeding divider. In this manner frequencies can be supplied in steps ranga. pc ing from say 10 megacycles per second or more to cycles per second or less.

A particular feature of the invention is that it makes possible division by numbers other than integers, thereby making it possible to obtain any desired ratio. Dividers previously employed have been limited in this respect and have permitted one to obtain only frequencies having an integral relation to the driving or exciting frequency.

I claim:

1. In electrical apparatus for producing a desired fixed frequency, a pair of electronic devices, the first arranged to operate as a modulator with substantial amplification gain, and the second arranged to operate as a frequency multiplier, means for supplying current of fixed frequency f to the modulator, means for supplying current of .the frequency from the frequency multiplier to the modulator, means for supplying current of the frequency from the modulator to the frequency multiplier and for supplying current of such frequency to the input of the second modulator, where 1': is a number which may or may not be aninteger, means for tuning the output of the secondmodulator to the frequency I and for supplying current at such frequency to the input of the first modulator, and means for supplying current at the frequency f directly to the input of the second modulator.

3. In electrical apparatus for producing a desired fixed frequency, a pair of electronic modulators each having input and output circuits, the first modulator being arranged for high amplification gain and the second modulator being arranged to have lesser amplification gain 'and acting as a frequency multiplier, means for supplying current of fixed frequency f to theinput of the first modulator, means for tuning the output of the first modulator to the frequency and for supplying current of such frequency to an output load and to the input of the second modulator, means for tuning the output'of the second modulator to the frequency a and for feeding back current of suchfrequency to the input of the first modulator, and means for supplying current at the frequency 1 directly to the input of the second modulator.

4. In electrical apparatus for producing a, desired fixed frequency, a pair of electronic modulators, means for supplying current of fixed frequency f to both the first and second modulators, means for supplying current of a frequency from the second modulator to the first modulator, where n is a number which may or may not be an integer, and means serving to supply current of the frequency n from the first modulator to the second modulator and to a load output.

L. BRUNTON BAUER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS