US2548024A

US2548024A - Attenuator

Info

Publication number: US2548024A
Application number: US130791A
Authority: US
Inventors: Arnold J Hyatt
Original assignee: A F Smuckler & Co Inc
Current assignee: A F Smuckler & Co Inc
Priority date: 1949-12-02
Filing date: 1949-12-02
Publication date: 1951-04-10
Anticipated expiration: 1968-04-10

Description

April 10, 1951 A. J. HYATT 2,548,024

ATTENUATOR Filed Dec. 2, 1949 2 Sheets-Sheet 1 INVENTOR ATTORNEY April 10, 1951 A. J. HYATT 2,548,024

ATTENUATOR Filed Dec. 2, 1949 2 Sheets-Sheet 2 z/ If Z7 3 .7/

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1a 17 H W 11 Z W y? Kl Ill I I I D l J6 INVENTOR W Mil A INA l [I W W a2 ATTORNEY Patented Apr. 10, 1951 ATTENUATOR Arnold J. Hyatt, Richmond Hill, N. Y., assignor to A. F. Smuckler & 00., Inc., Brooklyn, N. Y., a corporation of New York Application December 2, 1949, Serial No. 180,791

1 Claim. 1

The present invention relates generally to a radio frequency step attenuator and is more particularly directed to an apparatus of this type which may be employed for ultra high frequency waves or microwaves. In order that the attenuator may be useful in these ranges the conductors or resistances employed are of the coaxial type. It is one of the objects of the present invention, therefore, to provide an attenuator of simple and rugged construction and which eniploys the axial type of resistors.

Another object of the invention is to provide a completely shielded attenuator of the type described.

A still further object of the invention is to provide a variable attenuator having a range of 8 decibels operable in four equal steps.

Another object of the invention is to provide an attenuator cf the type described in which the error of deviation to frequency characteristics shall be less than 10% throughout the frequency range of 70 kilocycles to 609 megacycles.

Another still further object is to provide an attenuator which may carry a load or receive an input consisting of 100 volt pulses with a 0.125% duty cycle.

A still further object of the present invention is to provide an attenuator of the class described in which the effects of temperature, humidity, and voltage on its accuracy is minimized.

For the purpose of a fuller and more detailed description of the present invention and of its many objects and inventions, reference is had to the accompanying drawings and the following specification which illustrate one specific embodiment of the present invention; it being understood that variations thereof falling within the scope of the appended claim will be apparent to persons skilled in the art.

In the drawings:

Fig. 1 is a front end View of the attenuator.

Fig. 2 is a longitudinal sectional view on line 2-2 of Fig. 1.

Fig. 3 is a transverse sectional view on line 3-3 of Fig. 2.

Figs. 4, 5, 6, 7, and 8 are partial longitudinal views on each of the resistor circuits respectively.

Fig. 9 is a detail sectional view.

In its broad outlines the present attenuator consists essentially of a metal housing and a turret disposed within the housing. The turret, preferably a solid cylindrical metal body, is pro vided with an outer and an inner series of circularly disposed passages or barrels extending from end to end. Each pair of passages or barrels,

one from the outer and one from the inner series, disposed radially with reference to each other, are connected to each other by a recess in one end of the turret. Thus the pair of barrels with the recess form a U-shaped conduit for the reception of conductor-resistors of the coaxial type. The free ends of the barrels carry connectors of the coaxial type for separably connecting with a cooperating pair of fixed connectors carried by an end plate of the housing or casing. In its normal position the turret is maintained against accidental rotation and a selected pair of coaxial conductor-resistors are in engagement with the fixed connectors on the casing and the cables attached thereto may, therefore, receive the load or input and pass the same through the desired or connected pair of attenuating conductors or resistors. When it is desired to change the attenuation, the turret is first moved axially to disengage the turret from the fixed connectors on the end plate of the casing and the turret is then rotated into the desired position for the engagement of another pair of attenuating resistances with the fixed connectors on the end plate of the casing or housing.

With the above outline of the broad aspects of the construction of the present attenuator, a more detailed description of the several elements will now give a full understanding of the invention.

The metal housing or casing comprises a tube or cylinder ID, a front end plate l I, and a rear end plate Ill. The end plates have lower straight edges and are otherwise shaped as shown in Figs. 1 and 3, and have attached thereto feet or brackets 3. The inner faces of the front and rear plates are each provided with an annular shoulder 14 to receive the tube l0. Tie rods [5 connect the marginal portions of the end plates l l and I2 and the assembly is held firmlysecured by the cap nuts I 6. The detent H is mounted on the outer face of the tube or cylinder l0 and its detent lug l8 and extends interiorly of the tube for engagement with one of the grooves IS in the turret 20 to prevent its accidental rotation as shown in Figs. 2 and 3.

The turret 20 is a cylindrical body of metal, such as brass or the like, which may be provided with the circular series of passages 2| to reduce its weight. One end of the shaft 22 is lodged in the bearing 23 carried by the rear plate l2 and the other end of the shaft 22 passes through a corresponding opening in the end plate H and carries the handle 24 which is provided with a pointer 25. The exposed face of the end plate 55 is provided with several indicia as shown in Fig. 1 to indicate the step positions of the shaft and also to indicate the degree of attenuation in each of these positions. The turret is held firmly secured to the shaft 22 by the set screw 26. The forward end of the turret is provided with a recess 2? which receives the helical spring 28 interposed between the bottom of the recess and the inner face of the end plate ii, thereby holding the turret and its shaft in the normal or engaged position shown in Fig. 2. tainers 29 are disposed at the ends of the spring 28.

The outer cylindrical face of the turret 20 is provided with a circular channel 39 designed to receive the upper end of the detent 88 to permit rotation of the turret 2t. Relatively short longitudinal grooves l9 branch out from channel 39 and serve to receive the detent I8 when the turrot is in an engaged position. When it is desired to switch or change the position of the turret, it is moved axially against the spring 28 until,

the detent it? enters, the channelor passage 30..

The turret may then be rotated to desired position.

tion 33 at its rear end which receives the coaxial type of separable connector 3 5. The shoulder 35,

against whichthe connector 3 5 abuts, preferably extends somewhat into the passage or bore 32.

The bores or barrels 32 receive coaxial conductors or coaxial type attenuating resistors and.

the recess 3! receives the coaxial jumpe conductor 36 for connecting the two longitudinal coaxial conductorsor resistors. Thus each pair of parallel and radially spaced longitudinal barrels, together with its associated recess 3i, form a U-shaped passage or conduit for housing coaxial attenuator conductor-resistors.

All of the jumper conductors Siiare of the same construction. They each comprise a short length of insulation filled coaxial cable 37 which join a pair of short metal cylinders 38 disposed in the forward end of eachbarrel or bore 32-. The central conductor 39 in the jumpers extends at each end into the cylinders 38 and the ends are bent downwardly as shown in dotted lines in Fig. 4 and enter suitable recesses in the ends of the conductor-resistors disposedin the passages 32.

The conductors or the resistors disposed in the barrels 32 of the turret vary for the, purpose of varying the, degree of attenuation. Thus in one pair of barrels, which may be spoken of as the Zero pair, illustrated in Fig. 4, there are no resistors and these contain thev coaxial conductors consisting of the coaxial conducting sleeve to and the coaxial. conductor 4|. The sleeve (it abuts the shoulder and the insulating spacer disk 42 at the, other end. The conductor ll at one end enters a recess in the central electrode 53 of the quick detachable connector 33. t its other end the conductor M has, a reduced portion that pasIes through the spacer disk 42 and receives the bent end of the conductor 39.

Thus in the position of zero attenuation the two barrels each carry substantially non-resistive coaxial cables in series with the coaxial jumper Spring re- I conductor.

a. jecting wire 61.

4 that unites the two barrels and when the turret is in this position as shown in Fig. 2, the power coming in by one of the cables 44 leaves by the other substantially unattenuated.

The second pair of passages or barrels 32 that correspond to the 20 decibel position, one carries a coaxial conductor Ml, G5, which is the same as in the zero position. In the other passage of this pair, as will be seen in Fig. 5, a rod and disk resistor unit is inserted in series with the coaxial The rod 55 is of ceramic material or other suitable insulating material with a thin coating of resistive conducting material and capped by conducting caps 46, each having a pro- At one end the wire 47 enters a suitable recess in the end of the conductor 4|. At the other end, the wire 41 enters the passage of the retainer lt which is interposed between the -rod and the disk 49. The disk is made of Bakelite or any other suitable material coated with a thin reristivecoating of conductive. material. The retainer 18 has. a shoulder which abuts the dish and a reduced portion that passes. through anopening in the diskand joins with the,

conductor 33 of the quick detachable connector.

unit. to one tenth, of its. original strength.

In. position 3 or in the. 40 decibel. position. as. shown in Fig. 6, two rod and disk units are employed in series as shown. In this the degree of attenuation is one hundred, the signal being reduced to one hundredth its. originalstrength.

In the fourth or decibel position, as shown in Fig. 7, two rod. and disk assemblies are employed in series in oneleg of the conductor resistor and a thrd rod and disk assembly is mounted in-the other leg. In position 5 or in the decibel position, two such assemblies arev disposed in each leg of the resistor, as shown in Fig. 8, Inthese positions the degree of attenuation, is 1,000 and 10,000 respectively.

The manner in which the resistor disk 49 is held in position between a pair of rods 45is i1.- lustrated in Fig. 9. The retainer 28 is provided with an axial passage receiving the wires 47 from the adjacent rods. The reduced portion of the metallic retainer passes through the central aper-- ture in the disk 29- and receives the metallic an nulus 5! which bears against the other faceo the disk. Thus the disk is held between the elements 48 and ti and the latter are held between the adjacent rods 45. The rod resistor element 45 is a ceramic rod coated with a thin layer of carbon originally applied in the form of a carbon paint or a carbon suspension. The shunt elements, the. apertured disks 49,, are. preferably a minimum. The rod resistors are very small in cross section, and in the present embodiment of the invention they are less than /9 inch in diameter, thereby substantially eliminating the skin eirect, and the ceramic insulating material employed is of very low power loss thereby preventing the increase of its conductance with a rise in frequency.

The rod resistor 45 employed in the present embodiment of the invention has a resistance of 45s ohms, and maintains an essentially resistive In this pofiticn the degree of attenuation is ten, the signal being reduced by. the rod and disk.

characteristic up to and including 600 megacycles and throughout the range of the attenuator. When the resistance of the rod unit is increased, capacitance effects enter at the higher frequencies as the frequencies approach 600 megacycles. Thus the present apparatus employs the single rod in the 20 decibel attenuation and employs 2 or 3 or 4 such rods in series in the higher attenuations. If, instead of employing several rod and disk units, a single rod and disk unit having a much higher resistance were employed, the conditions of 0 phase angle and unity power factor would not exist.

The input shunt disk elements 49 each have a resistance of 55 ohms and the output shunt disk elements 50 each have a resistance of 50 ohms. Broadly described the present attenuation system employs a T network in which the resistance units in the inner conductor are each 450 ohms of the type described herein and the shunt units are the disks which are 55 or 50 ohms as described, there being at least one such shunt disk associated with each rod or at least one such shunt disk between adjacent rods.

I claim:

A shielded attenuator comprising a metal housing, a metal turret disposed within the housing, the turret havin a series of parallel passages, co-axial resistor conductors disposed in said passages, co-axial conductors mounted on one end of said turret and connecting adjacent resistor conductors in pairs, a connector carried by the other end of each resistor, a pair of fixed connectors carried by the housing for separable and selective connection with any desired pair of said first mentioned connectors, and means for moving said turret into selective engagement between said pair of fixed connectors and a selected pair of resistor connectors.

ARNOLD J. HYATT.

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

UNITED STATES PATENTS Number Name Date 1,905,353 Potter Apr. 25, 1933 1,957,538 Jensen May 8, 1934 2,286,029 Van Buren June 9, 1942 2,429,401 Davis Oct. 21, 1947