US2938175A

US2938175A - Transducer for high frequency transmission line

Info

Publication number: US2938175A
Application number: US480195A
Authority: US
Inventors: Donald J Sommers; William J Wilson
Original assignee: Sanders Associates Inc
Current assignee: Lockheed Corp
Priority date: 1955-01-06
Filing date: 1955-01-06
Publication date: 1960-05-24
Anticipated expiration: 1977-05-24

Description

May 24, 1960 D. J. SOMMERS ET AL 2,

TRANSDUCER FOR HIGH FREQUENCY TRANSMISSION LINE Filed Jan. 6, 1955 2 Sheets-Sheet 1 Fig. 4 Fig. 5

Donald J. Sommers William J. Wilson INVENTOR.

Attorney y 1969 D. J. SOMMERS ET AL 2,938,175

TRANSDUCER FOR HIGH FREQUENCY TRANSMISSION LINE 2 Sheets-Sheet 2 Filed Jan. 6, 1955 FRE QUENCY KILOMEGACYCLES Donald J. Sommers William J. Wilson INVENTOR.

Attorney United States A TRANSDUCER FOR HIGH FREQUENCY" TRANSMISSION LINE Filed Jan. 6, 1955, Ser. No. 480,195

8' Claims. (Cl. 333-6) The present invention relates to microwave transmission lines. More particularly, this invention relates to transitions between coaxial cylindrical transmission lines and planar transmission lines.

In the prior art, there have been many devices directed toward providing a right angle transition from coaxial transmission line to various forms of planar transmission lines. Such transitions are characterized by severe impedance discontinuities which cause undesirable reflections and extraneous modes of propagation. Where such transitions are not completely surrounded by boundary defining conductive surfaces, undesirable radiation takes place causing excessive coupling with nearby circuitry.

It is therefor an object of the present invention to pro vide an improved transducer for high frequency electric transmission lines in which undesirable propagation modes are suppressed.

A further object of the present invention is to provide an improved transducer for connecting coaxial transmission line to a high frequency electric transmission line having fiat, parallel conductors.

A still further object of the present invention is to provide an improved transducer electric component holder for connecting a component between a coaxial transmission line and a transmission line having parallel, flat conductors.

Yet another object of the present invention is to provide an improved method of connecting a cartridge type crystal diode between a coaxial transmission line and a transmission line having parallel, flat conductors.

Other'and further objects of the invention will be ap-' parent from the following description of preferred embodiments thereof, taken in connection with the accompanying drawings.

In addition with the invention, there is provided "a transducer for high frequency electric transmission lines. The transmission line includes a pair of planar outer line conductors providing ground plane and an elongated planar inner line conductor disposed in parallel with and in insulated spaced relation between the outer conductors. Transducer inner conductor means are provided with transducer outer conductor means coaxial with and surrounding the inner conductor means. The transducer conductor means are disposed adjacent the surface of one of the outerline conductors substantially perpendicular to the planes of the parallel line conductors. Means are further provided for connecting the line inner conductor and the transducer inner conductor means. A plurality of conductive elements are coupled between the line outer conductors and the transducer outer conductor means in an array surrounding the connection of the line inner conductors. The conductive elements provide electrical connections between the outer conductors and serve to confine high frequency electrical energy substantially therewithin. Any two, of the conductive elements are separated less than one-half wave-length apart at the highest operating frequency of the line. Y

In a preferred embodiment there is provided a trans- Pat ented May 24, 1960' CC I 2,938,175

ducer crystal diode holder for connecting a coaxial transmission line through a crystal diode to a high frequency electric transmission line having a pair of parallel, fiat, elongated outer conductors and a flat, elongated inner conductor disposed between the outer conductors parallel thereto. The transducer comprises a cylindrical inner particular reference to Figs. 1, 2 and 3, a transducer is shown for high frequency electric transmission lines havconductor and a cylindrical outer conductorcoaxial with and surrounding the cylindrical inner conductor. A crystal diode is coaxial with and surrounded by the cylindrical outer conductor. Insulating means position the inner conductor and diode in spaced insulated relation to the outer conductors. Means are provided connecting an end of the diode and the cylindrical inner conductor. Means are further provided connecting the other end of the diode and the fiat inner conductor. Conductive rods spaced less than one quarter of a wave length apart at the highest operating frequency of the line surround the flat inner conductor and diode, connecting the line and transducer outer conductors. The rods thus provide electrical connections therebetween to confine high frequency electric energy substantially within the confines of the outer conductors. v

' In accordance with the present invention there is further provided a preferred method of connecting a coaxial transmission line through a cartridge type crystal diode to a high frequency electric transmission line having a pair of parallel, flat elongated outer conductors and a flat, elongated inner conductor disposed between the outer conductors and parallel thereto. The diode has a relatively large, flanged, conductive, connection means with yet a narrower axial cylindrical extension at the other end. Insulating means position the inner conductor in spaced insulated relation to the outer conductors. The

method comprises removing the narrower, axial cylindrical extension from the diode and providing an aperture through one of the outer conductors. The narrower connection means end of the diode is placed in contact with the inner conductor through the aperture. The diode is oriented with a cylindrical outer conductor coaxial therewith. Electrical conductive resilience means is applied to the larger connection means end of the diode to direct forces through the diode to maintain its other end in contact with the inner conductor. The resilience means is connected to a cylindrical inner conductor by the' cylindrical outer conductor. Conductive rods are connected to the outer conductors. Adjacent rods are spaced less than one half a wave length apart at the highest operating frequency 'of the lines in an array surrounding the flat inner conductor, providing electrical connections be tween the outer conductors to confine high frequency electric energy substantially within the confines of the outer conductors. No pair of the rods has a greater separation than one-half wave-length apart. The wave length is taken herein to be A =elfective wave length within the transmission line.

In the accompanying drawings:

Fig. 1 is an isometric elevation'al view of a preferred embodiment of the present invention;

Fig. 2 is a bottom view of the embodiment of Fig. 1;

Fig. 3 is a sectional view of the embodiment of Fig. 1 taken substantially along the lines III-III of Fig. 2;

Fig. 4 is a sectional view of a modification of the em-.

Fig. 6 is a graph illustrating an aspect of the operation of the invention; and a Fig. 7 is a graph illustrating another aspect of the operation of the invention. Referring now in more detail to the drawings and with sser 3 ing a pair of elongated outer conductors 1 and and an elongated inner conductor 3 disposed between the

outer conductors

1 and 5. The transducer comprises inner conductor means here represented by the member 6 and an outer conductor 7, coaxial with and surrounding the inner conductor 6. The conductors are positioned by insulating means, here represented by the

members

2, 4 and 8. The

conductors

6 and 7 are cylindrical, while the

conductors

1, 3 and 5 are fiat and oriented parallel with each other as shown. Means, such as solder, con; nect the line and transducer

inner conductors

3 and 6,

respectively.

A plurality of conductive elements '9 extend between the line and transducer outer conductors, providing elec:v trical connections therebetween. The elements 9 may comprise threaded screws connected in threaded holes in the transducer outer conductor 7 through apertures in the flat transmission line. The elements 9 are spaced less than one half ofa wave length apart at the highest operating frequency of the line for best performance. The conductive elements 9. are disposed in an array surrounding the connection of the line inner conductor 3 to the transducer inner conductor 6. The elements 9 are so spaced as to avoid an electrical connection with the inner conductor 3. Likewise, an aperture 10 precludes an electrical connection between thetransducer inner conductor 6 and the transmission line outer conductor 1.

In the embodiment shown in Fig. 4 a cartridge type crystal diode 12, such as type 1N21B, is shown connected between a transducer inner conductor 64: and the trans-- mission line inner conductor 3,. A cover comprising an outer conductor 13 is coaxial with and surrounds the diode 12. An electrically conductive resilience means rep resented here by a spring 14 formed, for example, of beryllium copper, provides an electrical connection between the diode 12 and the inner conductor 6a. The spring 14 applies pressure to the diode to maintain 'ts other end in electrical contact with the inner conductor 3. A connection between a rivet 11 and the conductors 1, 3 n 5 pr id s a res ant tuning st to m tc the p anc o e. an duc o the imp a o t e transmission line.

n P e 5 a a trid e type ry al di e s o as mo nt d thout remo ing the smal e xi l cylind ical extension 15.-

Th t nsd e of; the Pr se t in ent on p o s a mea s or in rea in e e bil ty Qt etched circuit type. transmission lines. There are, of course, many applications where it is desirable and necessary to connect a I transmission line having parallel, fiat conductors to a, cylindrical coaxial transmission line. Etched circuit type transmission line has great advantages over conventional coaxial line or wave guides because of its structural simplicity and, consequently, its economy' of manufacture. The great disadvantage of such a transmission line is the. excessive coupling which can occur between neighboring sections of line in the event of impedance discontinuities. This is particularly true where discontinuity is introduced into the system, such as the right angle connection. The present invention solves this problem by the insertion of the conductive rods 9 electrically connecting the

outer conductors

1 and 5 in such a manner as to preclude radiation outside the extremities of the outer conductors by confining high frequency energy substantially within the confines of the outer conductors.

ure reduces the problem of matching the impedance of the diode with the transmission line. Conventional type crystal diodes, such as shown in outline by the diode 12a in Fig. 5, are very difficult to connect between the transmission lines without introducing severe impedance discontinuity by removing the narrower axial cylindrical extension 15 from the diode with, for example, a jewelers saw, the radio frequency path between the crystal and the inner conductor 3 is shortened to a minimum amount. An aperture 16 is provided through the outer conductor 1 and insulating member 2. The narrower connection means end of the remaining portion of the diode is placed in the aperture to contact the inner conductor 3. The electrically conductive resilience means,

such as the spring 14, applies pressure to the larger end of the diode and maintains its contact with the inner conductor 3. The spring is connected to the cylindrical inner conductor 6a which is surrounded by and afiixed to the cylindrical outer conductor 13. The outer conductor 13 being threaded internally .as shown is mechanically and electrically connected to the outer conductor 7. Conductive rods 9, spaced one quarter of a wave length apart at the highest operating frequency of the lines, are connected between the

outer conductors

1 and 5. The rods 9 surroundthe fiat inner conductor in that area where contact with the crystal is made. In this mariner high frequency electric energy may be confined substantially within the confines of the

outer conductors

1, 3, 7 and 13.

The line is preferably fashioned from a sheet of plastic, such as XXXP-Phenolic resin laminate, which is copper clad on both sides. The copper on one side comprises the outer conductor of the present invention and functions as a ground plane. e copper on the other side is etched to provide the inner conductor of the present invention. A second sheet of plastic, which is copper clad on one side only, provides the other outer conductor-and. functions as the other ground plane. It has been found desirable to provide a feed-through con nection from .the inner conductor through the plastic sheet with a suitable feed-through connector, such as an eyelet'or rivet. The use of such a feed-through connector permits greater flexibility in locating the inner conductor of the transducer or the diode (or other electric component) of the holder.

In a m del of the ransd cer hi h was ctu ly con ructe an ested. th nduct rs 1,. 3 n 5 re .00 of an inch thick and the

conductors

1 and 5 were .774; i ch w de nd he nne n uct r 3 was n h Wid The rods 9 were formed from 2 56 x /2 flathead screws. The. transducer is formed from a type N coaxial connection. Teflon Fiberglas .064 inch thick is used for the insulating-

members

2 and 4. Teflon .125 inch thick and .375 inch in diameter was used for the insulating meme her 8.

In Fig. 6 a graph of measurements of voltage standing wave ratio versus frequency is presented for a terminated transmission line embodying the transducer of Figs. 1, 2 and 3. As is apparent from Fig. 6, the transducer is operative over an extraordinary frequency range with substantially constant impedance characteristics. These, measurements were taken on three models.

Fig. 7 presents the well-known Smith chart (magnified scale) of impedance variations with frequency of the, crystal holders. of Figs. 6 and 7. Here the curves illuse trate the impedance characteristics of the crystal holders in the :frequencyrange from 4.100 to. 4500 megacycles, The curve having a phase. spread characterized by the angle [Sis obtained with the embodiment of the invention illustrated .in Fig. 5. Here the. shorting .r-ivet. 11 is optimally located 564 inch from the connection between the diode 12a and conductor When the extension is removed, asin Big. ahthe, phase spread over'the frequency range. .isrconsiderahly reduced as is illustrated. by the curve having a phase spread characterized by the angle a. For optimum impedance match, the rivet 11 is located .436 inch from the connection 12 and conductor 3 in Fig. 4. The improved impedance match is obtained at the expense of a slight increase in phase spread as shown by the angle 6. This graph strikingly reveals the enormous increase in operating frequency range with substantially constant impedance characteristics obtainable by the method of the present invention; i.e., removing the extension 15 as described above.

By means of the present invention the scope of application of etched circuit type transmission lines is greatly enlarged. This invention provides for the elimination of more expensive, complex, bulky and heavy transmission line installations.

While there has been hereinbefore described what is at present considered preferred embodiments of the invention, it will be apparent that many and various changes and modifications may be made with respect to the embodiment illustrated, without departing from the spirit of the invention. It will be understood, therefore, that all such changes and modifications as fall fairly within the scope of the present invention, as defined in the appended claims, are to be considered as a part of the pres ent invention.

What is claimed is:

1. A transducer crystal diode holder for connecting a coaxial transmission line through a crystal diode to a high frequency electric transmission line having a pair of parallel, flat, elongated outer line conductors and a fiat, elongated inner line conductor disposed between said outer conductors parallel thereto, comprising a cylindrical inner conductor; cylindrical outer conductor means coaxial with and surrounding said cylindrical inner conductor, said cylindrical conductors being substantially perpendicular to the planes of said parallel line conductors; a crystal diode coaxial with and surrounded by said cylindrical outer conductor means; insulating means positioning said inner conductor and diode in insulated relation to said outer conductor and conductor means; resilience means connecting an end of said diode and said cylindrical inner conductor; means connecting the other end of said diode and said flat inner conductor; and conductive rods, adjacent ones of which being spaced less than one quarter of a wave length apart at the highest operating frequency of said line in an array surrounding said connection between said fiat inner conductor and said diode, connecting said outer conductors and conductor means and providing electrical connections therebetween, to confine high frequency electric energy substantially within the confines of said outer conductors, no pair of said rods being separated more than one-half wave length apart.

2. The method of connecting a coaxial transmission line through a cartridge type crystal diode to a high frequency electric transmission line, said diode having a relatively large flanged, conductive, connection means at one end and smaller, flanged, conductive connection means with yet a narrower axial cylindrical extension at the other end and said line having a pair of parallel, flat, elongated outer conductors, a flat, elongated inner conductor disposed between said outer conductors and parallel thereto and insulating means positioning said inner conductor in insulated spaced relation to said outer conductors, comprising removing said narrower axial cylindrical extension from said diode; providing an aperture through one of said outer conductors and insulat ing means; placing the smaller connection means end of said diode in said aperture to contact said inner conductor; applying an electrically conductive resilience means to the larger connection means end of said diode to direct a force through said diode to maintain its other end in contact with said inner conductor; surrounding said diode with a cylindrical outer conductor coaxial therewith; connecting said resilience means to a cylindrical inner conductor surrounded by and aflixed to said cylindrical outer conductor; and connecting conductive rods, adjacent ones of which being spaced one quarter of a wave length apart at the highest operating frequency of said lines in an array surrounding said connection between said flat inner conductor and said diode, to said outer conductors and'providing electrical connections therebetween, to confine high frequency electric energy substantially within the confines of said outer conductors, no pair of said rods being separated more than one-half wave length apart.

3. A transducer for high frequency electric transmission lines, comprising: a pair of planar, outer line conductors providing ground planes; an elongated, planar, inner line conductor disposed in parallel with and in insulated, spaced relation between said outer conductors to provide a transmission line section; transducer inner conductor means; transducer outer conductor means coaxial with and surrounding said inner conductor means and disposed adjacent a surface of one of said outer line conductors,said transducer conductor means being substantially perpendicular to the planes of said parallel line conductors; means connecting said line inner con-' ductor and said transducer inner conductor means; and a plurality of conductive elements extending between said line outer conductors and said transducer outer conductor means in an array surrounding said connection of said line inner conductor to provide electrical connections between said outer conductors and confine high frequency electric energy substantially therewithin, any two of said conductive elementsbeing separated less than one-half. wave length apart at the highest operating frequency of said line. v

4. A transducer for. high frequency electric transmission lines, comprising: a pair of planar, outer line con ductors providing ground planes; an elongated, planar, inner line conductor disposed in parallel with and in insulated, spaced relation between said outer conductors to provide a transmission line section; transducer inner conductor means; transducer outer conductor means coaxial with and surrounding said inner conductor means and disposed adjacent a surface of one of said outer line conductors, said transducer conductor means being substantially perpendicular to the planes of said line conductors; means connecting said line inner conductor and said transducer inner conductor means; and a plurality, of conductive elements extending between said line outer conductors and said transducer outer conductor means in an array surrounding said connection of said inner conductor to provide electrical connections between said outer conductors to confine high frequency electric energy substantially within the confines of said outer conductors, said conductive elements being adjacently disposed less than a quarter-wave length apart and any two of them being separated less than one-half wave length apart at the highest operating frequency of said line.

5. A transducer for high frequency electric transmission lines, comprising: a pair of planar, outer line conductors providing ground planes; an elongated, planar, inner line conductor disposed in parallel with and in insulated spaced relation between said outer conductors to provide a transmission line section; transducer cylindrical inner conductor; a transducer hollow, cylindrical outer conductor coaxial with and surrounding said transducer inner conductor and having an end disposed adjacent a surface of one of said line outer conductors, said transducer conductors being substantially perpendicular to the planes of said line conductors; means connecting said inner conductors; and a plurality of conductive elements extending between said line outer conductors and said transducer outer conductor in an array surrounding said connection between said inner conductors to provide electrical connections between said outer conductors and confine high frequency electric energy substantially therewithin, any two of said conductive e1emeats .being separated lessv than one-half wavelength apart. at the highest operating frequency of said line. .A transducer. for high frequency, electric transmisr. sicn. n s, c mpris ng: a p r- Of thin, e o ga e p congrueut y di i qssd; clo e y spa e t r li c d tors provi ing ground planes; a thin, elongated, plane, inner line conductor disposed in parallel with and in insulated spaced relation between said outer conductors to provide. a transmission line section; a; pair of elongated, plane insulating panels, each disposed between said inner conductor and one of said outer conductors; a transducer. cylindrical inner conductor; a transducer, hollow, cylindrical, outer conductor coaxial with and surrounding said transducer inner conductor having an end afiixed and connected to a surface. of one of said line outer conductors; an annular dielectric insulating spacer disposed within said transducer outer conductor adjacent said end and adapted centrally to hold said transducer inner conductor in spaced relation to said transducer outer conductor, said transducer inner conductor extending through said end; means connecting said inner conductors, said transducer inner conductor contacting said line inner conductor through an enlarged orifice in the adjacent line outer conductor and a smaller orifice in the adjacent nsulating panel; and a plurality of conductive rods connecting said line outer conductors and transducer outer conductors in an array surrounding said connection between said inner conductors to confine high frequency energy therewithin, any two of said conductive rods being separated less than one-half a wave length apart at the highest operating frequency of said line.

7. A crystal holder for high frequency, electric transmission lines, comprising: a pair of thin, elongated, plane, congruently disposed, spaced, outerline, conductors providing ground planes; a thin, elongated, plane, innerline conductor disposed in parallel with and in insulated spaced relation between said outer conductors to provide a transmission line section; a pair of elongated, plane insulating panels each disposed between said inner conductor and one of said outer conductors; a transducer cylindrical inner conductor; a transducer, hollow, cylindrical outer conductor coaxial with and surrounding said transducer inner conductor having and end afiixed and connected to a surface of one of said line outer conductors; a crystal rectifier having a cylindrical central part carrying said crystal, a flanged metal cap connector surrounding an end of said part and connected to said crystal, and a fiat, metal, disc-like connector concentrically abutting the other end of said part and providing the second connection for said crystal, said crystal rectifier being concentrically disposed within said transducer outer conductor and extending therefrom with said discconnector contacting said line inner conductor through an enlarged orifice in'the adjacent line outer conductor and a smaller orifice in the adjacent insulating panel;

resilience means extending from. said transducer inner conductor and contacting said flanged connector to apply aforce. to hold said crystal in contact with said line inner. conductor; and a plurality of conductive rods connecting said line outer conductors and transducer outer conductors. in an array surrounding said connection between said crystal and said line inner conductor to confine high frequency energy therewithin, any two of said conductive rods being separated less than onehalf a wave length apart at the highest operating fre-. quencyof said line.

8,. .A transducer for high frequency electric transmis-. sion lines, comprising: a pair of thin, elongated, plane, congruently disposed, spaced, outerline conductors providing ground planes; a thin, elongated, plane, innerline conductor disposed in parallel with and in insulated spaced relation between said outer conductors to provide a transmission line, section; a pair of elongated, plane insulating panels each disposed between said inner conductor and one of said outer conductors; a transducer cylindrical inner conductor; a transducer, hollow, cylindrical outer conductor coaxial with and surrounding said transducer inner conductor having an end affixed and connected to a surface of one of said line outer conductors, said transducer conductor having a rotatable section with an inside screw thread and a fixed section with an outside screw thread for engagement together; an annular dielectric insulating spacer disposed within said transducer outer conductor adjacent said end and adapted to hold said transducer inner conductor in spaced rela-, tion to said outer conductor and extending from within said outer conductor through said end; means connecting said inner conductors, said transducer inner conductor contacting said line inner conductor through an enlarged orifice in the adjacent line outer conductor and a smaller orifice in the adjacent insulating panel; and a plurality of conductive rods connecting said line outer conductors and transducer outer conductors in an array surroundingsaid connection between said inner conductors to confine high frequency energy therewithin, any two of said con ductive rods being separated less than one-half a wave length apart at the highest operating frequency of said line.

References Cited in the tile of this patent UNITED STATES PATENTS 2,602,858 Rumsey July 8, 1 952 2,603,749 Kock July 15, 1952 2,734,170 Engelmann et al Feb. 7, 1956' FOREIGN PATENTS 156,688 Australia May 24, 1954 OTHER REFERENCES Electronics, June 1952, pages 114-118.