US2901710A - Resistance terminating loading devices - Google Patents

Description

4 E. GARTHWAITE 2,901,710

RESISTANCE TERMINATING LOADING DEVICES Filed Feb. 15, 1956 Aug. 25, 1959 L v l A -'I/ I l D I. A] V B3 .5 \A4 A2 A3" a v 3 B2 7 E501, v a

|NVENTOR BY EM fa W1 A'r'roRNEN United States Patent RESISTANCE TERMINATING LOADING DEVICES Ernest Garthwaite, Saint Albans, England, assignor to Marconi Instruments Limited, London, England, a British company Application February 13, 1956, Serial No. 565,244

Claims priority, application Great Britain February 16, 1955 4 Claims. (Cl. 333-22) This invention relates to resistance terminating loading devices.

Although not limited to its application thereto the invention is particularly well suited to the provision of resistance terminating loading devices for use in making radio frequency power measurements, for example for measuring the radio frequency power delivered by a transmitter. In order to make such a measurement it is necessary to reproduce the aerial impedance so as to( simulate the normal working conditions and also to terminate the connecting cable correctly. When dealing with high frequencies, for example frequencies of the order of 300 mc./s., and powers of more than a few watts, it is by no means easy to provide a correctly matched load since the components of the load tend to become large and therefore to present reactance. The present invention seeks to solve this problem by means of relatively simple and economical structure which shall have inherently good cooling so that large powers can be handled and which shall be such as to allow of ready and convenient adjustment when in use.

It is well known that if a resistive load terminating device is so designed that the total resistance between any section and the end remote from the input end is equal to the characteristic impedance at that section, the device will present a substantially pure ohmic resistance irrespective of the applied frequency. Resistance terminating loading devices embodying this principle are of course Well known. The present invention provides improved resistance terminating loading devices of the known kind embodying this principle and consisting in effect of a central resistance forming part of the inner conductor of a tapered line the tapering of which is so chosen in accordance with known principles to produce the result of presenting a substantially pure ohmic resistance termination independent of frequency over a wide range.

According to this invention a resistance terminating loading device consists of inner and outer conductor structures of which the inner structure comprises a pair of oppositely disposed divergent conductive plates con tinuing at their divergent ends into a resistor element and the outer structure consists of a second pair of oppositely disposed plates symmetrically positioned on opposite sides of the inner structure, the plates of the outer structure diverging from one another and from the adjacent plates of the inner structure substantially over the length over which said inner plates diverge, said outer plates converging again towards the far end of the resistor element of the inner structure, means being provided for applying input between the inner and outer conductive structures at their common convergent end.

The resistor element may be of tubular form-for example, it may consist of a graphitic deposit on a ceramic tubebut this is not essential and other forms of resistor element may be used. A prepared form of element consists of a slab like body (i.e. a fiat sided body) of ceramic material with a graphitic or other resistive ice deposit thereon. Such an element is easier to mount than a tubular element and makes the adjustment of the position of the plates of the outer structure less'critical, for correct matching, than is the case with a cylindrical tubular element.

Preferably the outer conductive plates are springily flexible and matching adjustment means constituted by means for controllably bending said outer plates towards one another is provided. Preferably also the device is mounted in a frame in such a manner that when in use the resistor element is inclined substantially with respect to the horizontal and the inner and outer plates are substantially vertical. With this arrangement inherently good cooling by induced draught is obtained.

The invention is illustrated in the accompanying drawings in which Fig. 1 is a schematic top view of one embodiment and Fig. 2 is a side view of the embodiment of Fig. 1. In both Figs. 1 and 2 the supporting frame for the device is omitted so as not to complicate the drawing and in Fig. 1 circuit elements for enabling the device to be used as a power meter are included, these circuit elements however not being repeated in Fig. 2.

The device shown in the drawings comprises inner and outer conductor structures of which the former are indicated by references including the letter A and the latter by references including the letter B.

The inner structure comprises a pair of divergent metallic plates A1, A2 which are connected together at their convergent end to the inner conductor A3 of an ordinary co-axial socket input. At their divergent ends the plates A1, A2 are connected to, and mechanically support one end of, a resistor element A4 constituted for example by a graphitic deposit on a ceramic body. An encircling metallic strap A5 at or near the far end of the tube is used for making connection to the resistance. In the drawing the ceramic body is a ceramic tube so that the resistor element is tubular. There are, however, advantages in the matter of easier mounting and less critical adjustment in using, instead of a cylindrical tubular resistor element, a slab shaped element with the major parallel flat sides of the slab at right angles to the plane of the paper of Fig. l.

The outer structure consists of a pair of flat plates B1, B2 which, starting from the input end, first diverge, then remain approximately parallel for a short distance and then converge. The plates B1, B2 are connected together at the input convergent end to the outer conducto B3 of the co-axial input socket.

The dimensions are so chosen, in accordance with well known principles, that, over the length X where the plates A1, A2 and B1, B2 diverge, a constant impedance match is provided while the remaining length Y provides a progressive matching section including the load.

About half way along the load section of the device is situated a pair of L sectioned brackets 1 and 2 which are positioned on the outer faces of the plates B1 and B2 and can be drawn towards one another to a controllable extent by means of nuts and bolts 3 and 4, thus con trollably deforming the plates B1 and B2 against their natural springiness. Adjustment of the separation of the plates B1 and B2 in this manner provides a useful and quite critical adjustment which enables reactive effects to be eliminated (when the device is in use) at any working frequency over a wide frequency band. By reactive effects as just mentioned is meant, of course, reactive effects manifested at the input socket.

For power measurement a connection is taken at 5 from the strap A5 and thence through a swamping resistance 6 to a thermo-couple the output of which is measured by a meter 8.

The device is mounted in a frame (not shown) which is so arranged with respect to the said device that in use the plates A1, A2, B1, B2 lie vertical and the resistor element A4 is at a substantial angle to the horizontal for example 30. In Fig. 2 the horizontal .is indicated by thechain line. As will be apparent this arran emen gives excellent natural draught cooling.

I claim:

"1. A resistance terminating loading device .ponsisting of inner and outer conductor struetures' ofwhich the inner structure mp ses :a p ir of -.0ppo. y disposed divergent conductive innerplates continuing attheirldivergentends into aresistor element and wherein th outer structure consists of a second pair of oppositely diSP Qd Plates ym tri l y .posi ion dnn-onub i sid sof th inner structure 'formil g vQll P1 $,i ai. i-H9 P ates 9f the outer structure being springily flexible ,and diverging m one n r-and from .theadiac nt inne .pla e .Q the inner structure substantially over the length over which said ,innerplates diverge, said outer platesiconverg ing again towards the far end ofvtheresistorQelementtof the inner structure whereat the ,resistor and the outer plates are connected, matching adjustmentmeans consti tuted by means for controllably'bending said outer, plates towards one another, .and means for applying input between the inner and outer conductive Structures at their common convergent end.

A resistance terminating loading device consisting ofinner and outer conductor structures of which theinner structure comprises a pair of oppositely disposed divergent conductive inner plates eontinuing at ,th'eirdiveIgent ends into a resistor element and the outer structuretconsistsof a second pair of oppositely disposed plates syn1- metrically positioned on opposite sidesof theinner-structure forming outer; plates, said outerpletes of the outer structure diverging from one another and frorn the adjacent inner plates of the inner Structuresubstantia lly over thelength. over which said innerplratest diverge, said outerplates converging again towards the;far ,end;of the resistor element of the inner structure whereat the .resistor and the outer plates are connected, matchingadjustment means constituted by means for controllably bending said outer plates towards one another, means for applying input between the 'innerand outer conductive structures at their common convergent end .and a framefor mounting said structures insuchaposition that when in use the resistor element is inclinedsubstantially plates symmetrically positioned on opposite sides of the inner structure and forming outer plates, said outer plates of the outer structure diverging from one another and from the adjacent inner plates of the inner structure substantially over the length over which said inner plates diverge, said outer plates converging again towards the far end of the resistor element of the inner structure whereat the resistortand the outer plates are conneeted, matching adjusting means constituted by means for controllably bending said outer plates towards one another, means for applying input between the inner and outer conductive structures at theircommonconvergent end, said outer plates being .springily flexible and means engaging the exterior sides thereof consisting of'lineal members extending transversely of said last mentioned plates and bolts havingrscrew-threaded ends thereon extending through said lineal members and adjustable nuts on said bolt or adju ting said alas rr entiened rplates toward each other and toward said inner structure and said tres st elem nt 4- A r s an enn na ing l ading device consisting o inne a d o t structures Qf'zWhiGh-ihfi inner structure comprises a pair of ;oppo sitely disposed divergent .con-

duetive inner plattis continuing v,at wtheir divergent ,ends

with respect to the'horizontal andthe inner andouter v V platesextend in substantially verticalfplanes.

' 3. A resistance terminating loading d evice consisting of inner and outer conductor structures otwhich :the inner structure comprises .a pair of oppositely disposed divergent conductive inner plates eQntinujngaptheir di.

vergent ends intoraresistor-,element and the. outer struci into a res tor el m n and athe outer structure consists of a second pair -;otv oppositely di posed plates symmetrieally positioned onioppositessides .of-;the :inner structure and torrningouter'platee, the=plates:of the outer structur rd ersing from ,Que another and :from rthe adjacent s a e e r h inne st ucture substantially lover the length over wh h said inner plates tdiverge, said outer plates fifi lfi 'llg a a n itOWhIds the {far ,end of ;-the l-resistortelen ent otth inn rrs -ruc ure whereatrthe resistor and-the outer plates ;are ,connected, matching adjustment means .QQll l lltfi' y-mee s for-coutrollablysbending said outer plates 1 towards one another, means for applying input between the inner and ,outer zconductive {structures .at their common convergent end, said outer plates :being springilyfieXibLe and beingsenga-ged on the exterior sides h ee y l nea members iextendingtransversely. of said last mentioned plates and bolts extending :through .said lineal membersand through said 1pair of .oppositelyvdis- .posed outer plates in spatial 5-1612111011 Ito diametrically opposite sidesof-said resistor, rsaid sbolts having screwthreaded ends projecting;beyondiheexterior face ofv one of said plates and adjustable nuts engaging said .screwhreade s d and adju table von .said bolts for ,adjusting the atial relation n t said outer Lplates.

References Citedin'the-file of this patent UNITED STA TES PATENTS was

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