US3665347A - T-attenuator or coupling network having an identical characteristic impedance from either end - Google Patents

Abstract

An attenuator or pad device which has an outer conductor in the form of a generally T-shaped body, formed with an interior cavity extending longitudinally therethrough. The cavity is also generally T-shaped in configuration having one part in the form of a double-ended expotential horn having its apex or smallest diameter at the center of the tubular body and extending continuously expotentially outwardly therefrom in opposed longitudinal directions to the outer ends of said body. A second part of the cavity forming the stem thereof is also generally expotential in form extending from the bottom of said stem outwardly and upwardly to communicate with the double-ended cavity part at its center. An elongated resistance element defining the inner conductor of the attenuator or pad extends centrally through the cavity and provides an impedance pad which has the same input and output magnitude whereby the device may be utilized as an interstage coupling device.

Description

United States Patent Barth [451 May 23., 1972 [54] T-A'ITENUATOR OR COUPLING NETWORK HAVING AN IDENTICAL CHARACTERISTIC IMPEDANCE FROM EITHER END 52 us. 01., ..333/s1 A, 333/34 of Radio Research Lab. Harvard u., McGrawl-lill, 1947, pp. 1,01 s 1,020.

Primary Etaminer-Herman Karl Saalbach Assistant Examiner-Wm. H. Punter Attomey-Baldwin, Egan, Walling & Fetzer ABSTRACT An attenuator or pad device which has an outer conductor in the form of a generally T-shaped body, formed with an interior cavity extending longitudinally therethrough. The cavity is also generally T-shaped in configuration having one part in the fon'n of a double-ended expotential horn having its apex or new ofs h smallest diameter at the center of the tubular body and extending continuously expotentially outwardly therefrom in op- 56] Reerences Cited posed longitudinal directions to the outer ends of said body.

Asecond part of the cavity forming the stem thereof is also UNITED STATES PATENTS' generally expotential in form extending from the bottom of 2,399,645 5 1946 Latimer ..333/34 x said Stein outwardly and lq y to communicate with the 2,620,396 12/1952 Johnson et al ...333/81 A double-ended cavity p at Its center- An elongated resistance element defining the inner conductor 4:123 3/1965 F 333/81 A of the attenuator or pad extends centrally through the cavity I 5 6 3/1967 g 333/81 and provides an impedance pad which has the same input and y output magnitude whereby the device may be utilized as an in- OTHER PUBLICATIONS terstage coupling device.

Harvard, Very High Frequency Techniques, Vol. 2, Staff '1 Claims, 2 Drawing Figures 24 I /0 24a 4 [a t4 t2 1 QWXXXX Patented May 23, 1972 3,665,347

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HTTORNEYfi T-ATTENUATOR OR COUPLING NETWORK HAVING AN IDEN'IICAL CI'IARACTERIS'I'IC IMPEDANCE FROM EITHER END Additional objects and advantages of the attenuator on. pad

device of the present invention will be apparent to one skilled in the art and upon reference to a preferred embodiment thereof as is described in the following specification and illustrated in the accompanying drawings wherein:

FIG. 1 is a side view in elevation of the attenuator or pad device embodying the present invention;

FIG. 2 is an end view taken an approximately of FIG. 1;

FIG. 3 is a longitudinal sectional view taken on line 3--3 of FIG. 2; and v FIG. 4 is a schematic diagram of the effective circuit of the attenuator device.

Referring now to the drawings, as shown particularly in FIGS. 1 and 3, the attenuator or pad device of the present invention includes an elongated tubular body 10 generally T- shaped in overall configuration formed of a suitably conductive material such as steel and defininga first or cross-bar part 12 and a second or stem part 14.

The first body part 12 is provided with an internal cavity 16 which extends generally centrally longitudinally therethrough, and is of a double-ended expotential horn configuration. The apex 17 of the horn-type cavity is located at the center of the body 10, the wall thereof extending expotentially outwardly toward the opposed longitudinal ends to an end cavity portion 18 of constant diameter.

The stem part 14 of the body 10 is also formed with an internal cavity as shown at 20 which extends centrally longitudinally therethrough being single-end expotential horn-like in configuration with the wide end of the horn communicating with the apex 17 of the aforesaid horn cavity 16.

A suitable resistance element, being generally tubular in form as identified at R, and which may be made of any suitable material merely for example a ceramic base material having a resistance material deposited on the surface thereof, maybe disposed in the cavity 16 extending centrally therethrough being thus equally spaced from the cavity wall.

As seen at 22, end caps formed of any suitable insulating the line 2-2 material may be disposed in the end cavity portions 18 and into which the ends of said resistance element R may be disposed being thus effective to retain the same centrally within the cavity 16.

A second resistance element as identified at T may be similarly disposed in the cavity 20 of the body part 14, an end thereof projecting into the apex part 17 of the horn cavity 16 and suitably rigidly attached to the resistance element R at its center point.

The stem part 14 of the body 10 is provided with an upstanding rim 24 surrounding the adjacent end of the cavity 20 and provides support for the end of the resistance element T disposed therein.

The resistance material is deposited by any suitable method upon the surface of the rod elements R and T being distributed thereover and connected together at the juncture of the said. rod elements to form a T-network comprising resistances R, and R: as shown in FIG. 4.

The stem part of the body may be threaded as seen at 240 which may enable a suitable cap 26 to be placed thereover. to effectively seal the cavity 20 at said one end. The body of the device may also be provided with a threaded port 28 which opens to the apex 17 of the horn cavity 16 directly opposite the communicatin end of cavity 20, and which may be used ly of the device and connection thereof to facilitate assem into an electronic circuit.

The input end of the attenuator or pad device may be terminals t and t and the output end similarly identified at t, and By attaching conductors to each of said terminals 1, and tgand connecting rg, to the body 10, the attenuator or pad device may be used as an interstage coupler; terminals 2, and representing the input of said attenuator and terminals and t the output thereof. Terminal i may be used as the circuit ground or neutral conductor. The resistance elements R and T with the aforesaid terminal connections defines the inner conductor of the attenuator or pad, and the body 10 the outer conductor of said device.

With the resistance values R, and R assigned, it will also be i realized that the characteristic impedance 2,, looking in either As is further understood, the inductance of the attenuato or pad varies directly as the logarithm of the spacing between the center conductor R R and the body 10 representing the outer conductor the wall of cavity 16 varying expotentially and decreasing in spacing toward the apex 17. Likewise, the capacitance varies inversely as the logarithm of the aforesaid spacing between said conductors. In like manner, the inductance of the section of the pad represented by resistance R in the stem cavity 20 varies directly as the logarithm of the spacing between the center conductor R and the wall defining said cavity 20 which is seen to vary expotentially from the apex 17 of horn cavity 16 and decreasing to the upper end thereof as seen in FIG. 3. Also, the capacitance of this pad section varies inversely as the logarithm of the aforesaid spacing between said conductors.

Having thus described a preferred embodiment of attenuator or pad device of the present invention, it will be apparent to one skilled in the art to which it pertains that this invention may be changed and/or modified without departing from the inventive concept as are defined in the claims.

What is claimed is:

1. An attenuator or pad for providing interstage coupling comprising a body formed of conductive material, means defining a double-ended expotential horn in said body and extending longitudinally therethrough with the apex of said horn being at the center of the body, means in said body defining a single-ended expotential horn extending transversely of the double-ended horn and connecting at its larger end with the apex of the double-ended horn, first resistance means extending centrally through the double-ended horn, second resistance means extending centrally through the single-ended horn, one end of the second resistance means connecting with the first resistance means at the apex of the double-ended horn to thereby form a T-network having a shunt resistor and two series resistors equal to each other, the opposite end of the shunt resistor being defined as the common terminal of the T-network, the free end of each of the series resistors representing an input tenninal and an output terminal respectively of said T-network which together with the common terminal define the input end and the output end of the network, the impedance of each series resistor of the T-network as determined by the spacing between the series resistor and its associated surrounding wall of the double-ended horn varying expotentially and in a decreasing magnitude incrementally

Claims (1)

1. An attenuator or pad for providing interstage coupling comprising a body formed of conductive material, means defining a double-ended expotential horn in said body and extending longitudinally therethrough with the apex of said horn being at the center of the body, means in said body defining a singleended expotential horn extending transversely of the double-ended horn and connecting at its larger end with the apex of the double-ended horn, first resistance means extending centrally through the double-ended horn, second resistance means extending centrally through the single-ended horn, one end of the second resistance means connecting with the first resistance means at the apex of the double-ended horn to thereby form a T-network having a shunt resistor and two series resistors equal to each other, the opposite end of the shunt resistor being defined as the common terminal of the T-network, the free end of each of the series resistors representing an input terminal and an output terminal respectively of said T-network which together with the common terminal define the input end and the output end of the network, the impedance of each series resistor of the T-network as determined by the spacing between the series resistor and its associated surrounding wall of the double-ended horn varying expotentially and in a decreasing magnitude incrementally equally toward the apex of the horn and the impedance of the shunt resistor of the T-network as determined by the spacing between said shunt resistor and its associated surrounding wall of the single-ended horn varying expotentially and in an increasing magnitude incrementally toward the apex whereby the T-network has an identical characteristic impedance from either end.

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