US2403252A - High-frequency impedance-matching device - Google Patents

Description

July 2, 1946.

H. A. WHEELER HIGH-FREQUENCY IMPEDANCE-MATCHING DEVICE Filed Nov. 16, 1944 FIG.I

2 Sheets-Sheet l A RNEY y 2, 5- H. A. WHEELER 2,403,252

HIGH-FREQUENCY IMPEDANCE-MATCHING DEVICE Filed Nov. 16, 1944 '2 Sheets-Sheet 2 INVENTOR HA CL A. WHEELER W RNEY Patented July 2, 1946 Harold A. Wheeler, Great Neck, N. Y., assignor, by

r mesne assignments, to Hazeltine Research, Inc.,

Chicago, 11]., a corporation of Illinois Application November 16, 1944, Serial No. 563,713

The present invention relates to, high-frequency impedance-matching devices and, particularly, to

such devices of a type adapted for connection for example in high-frequency wave-signal circuits, the impedance encountered and required to be matched are complex so that a satisfactory result necessitates a matching of the resistance components and a cancellation of the reactance components of the impedances.

Transmission lines of either fixed or adjustable lengths have heretofore been widely used as impedance-matching devices, especially in highfrequency wave-signal circuits. A transmission line when so used exhibits the properties of an impedance transformer in that it is able to transform the value of an impedance coupled to one end of the line to a different value of impedance at its other end. The maximum ratio of impedance transformation varies with the ratio between the characteristic impedance of the line and the value of the impedance to be transformed, but both the actual ratio of the impedance transformation and the magnitude and nature of the reactance components after transformation vary with the effective electrical length of the transmission line. The use of an open or balanced type of transmission line for this purpose requires an adjustment both of theline length and line characteristic impedance where an impedance balance at several operating frequencies is re- I quired. This is because both the magnitudes and phase angles of the impedances to be matched and the electrical length of the line all vary with frequency.

It has been proposed that a coaxial transmission line one wave length or more long be employed for impedance matching, the line having a characteristic impedance equal to the value of impedance of one or both of the terminal impedances and being provided with two quarterwave sliders which surround the inner conductor of the line and are independently adjustable axially therealong. These sliders modify the characteristic impedance of the line over the length of each slider and effect, over a range of impedances, a matching of the resistance com- 11 Claims. (01. 178-44) ends of the line.

ponents and a cancellation of the reactance components of two impedances coupled to individual This impedance-matching device when once properly adjusted to provide an impedance match at one operating frequency may not maintain even an approximate impedance match over more than a small range of operating frequencies so that the device may be said to be critical of frequency. The reason for this is that the change of phasethrough the line with change of frequency becomes more severe as the line length increases, there being a cumulative phase shift for the reflected wave-signal energy which is produced at a multitude of points along the length of the device described. It is desirable in many applications that an impedancematching device provide an exact impedance match at one frequency and that a closely approximate impedance match be maintained without further adjustment over a substantial range of operating frequencies. Additionally, it is frequently desirable that an impedance-matching device of this type have a physicalsize appreciably smaller than is possible with the device described.

It is an object of the present invention, therefore, to provide a new and improved highfrequency impedance-matching device which avoids one or more of the disadvantages of prior 80. devices of this type.

It is an additional object of the invention to provide a new and improved high-frequency impedance-matching device having minimum physical size, one of simple yet sturdy constructlon,. and one which is characterized by case and frequency impedance-matching device adaptedv for connection between and for matching at a given frequency a pair of impedanceshaving any values within a predetermined range of magnitude and phase comprises a plural-conductor transmission line adapted-to be connected between the impedances and having a predeter- 3 mined electrical length at the aforementioned given frequency and a predetermined characteristic impedance din'eringin one sense from the geometric mean of the pair of impedances. The device includes a plurality of members positioned between the conductorsof the line and independently adiustably movable axially therealong. Each of the adjustable members has at the given frequency a predetermined effective electrical length substantially less than one-half the length of the line and has its shape and material so selected as to cause the characteristic impedance of the line over the lengths of the members to diifer from the geometric mean of the aforesaid impedances in opposite sense from the sense in which the line differs there-- from, and by such magnitude as to enable the transmission line for an adjusted position of the members to match the resistance components and to cancel the reactance components of the afore- 20 ends. The discs ll,

table means such as screws ll. Terminals I'I,

' The present invention is related to that disclosed and claimed in applicant's copending apsaid pair of impedances.

plication entitled Wave-signal transmission line, Serial No. 563,714, flled November 16, 1944, and assigned to the same assignee a the present invention. Whereas the transmission line of the co ending application utilizes a member of magnetic material movable axially along the line to effect an adjustment of the line terminal impedance, the impedance-matching device of the present invention utilizes two members of conductive, dielectric or magnetic material axially independently movable along a quarter-wave line for purposes of matching, over a range of values of magnitude and phase, two impedances which are coupled to individual ends of the line. The present invention is also related to the device of applicants copending application entitled Wave-signal. tuning device, Serial No. 563,712, filed November -16, 1944, and assigned to the same assignee as the present application. In thelast-mentioned copending application, a member of conductive, dielectric or magnetic material, or a combination of such materials, is axially movable along a transmission line having an electrical length of an odd number of quarter-wave length and short-circuited at its remote end to provide a resonant line adjustable to resonance at any frequency in a range of o erating frequencies.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings. and its scope will be pointed out in the 3 appended claims.

In the drawings, Fig. 1 is a longitudinal sectional view of a high-frequency impedancematching device embodying the present invention; Fig. 2 is a diagrammatic representation of the device of Fig. 1; Fi 3 is a sectional view of amass:

less than one wave length 4 coaxial transmission line including a hollow outer conductor H and an inner conductor l! main-- tained in coaxial relationship by spaced insulating discs II, II. 'l'hetransmission line ii, If has a characteristic impedance Zo' differing in a given sense from. for example an impedance either higher or lower than, the geometric mean of the terminal impedances Z1, Z2 and an electrical length less than one wave length at the aforementioned given frequency. Minimum physical size is attained when the transmission line has an electrical length equal to one-quarter wave length. When the ratio of the terminal impedances Z1 to Z:, or vice versa, is relatively large, the transmission line I I, I2 preferably has an eifective electrical length equal either to one-quarter wave length or to three-quarters wave length since it then is enabled to provide an optimum ratio of impedance transformation between its terminal 13 are held in position by and l8, l8 are provided at opposite extremities of the conductors II and If to permit the impedances Z1, Z2 which are to be matched to be connected in circuit with the device.

The impedance-matching device also includes a plurality of members l5, 18 ositioned between the conductors II and I 2 and independently adiustably movable axially along the conductors. Each of the adjustable members 15 and It has at the aforementioned given frequency a predetermined eflective electrical length substantially less than one-half the length of the line II, If, a preferred physical length for optimum range of control being one-quarter the line length but not exceeding a physical length which provides an effective electrical length of one-quarter wave length. The members It, I8 have their shape and material so selected as to cause the characteristic impedance Zo" of the line H, l2 over the lengths of the members l5, It to differ from the geometric mean of the terminal impedances Z1,

Z2, though in opposite sense from the sense in which the line II, I 2 differs therefrom, and by such magnitude as to enable the transmission line for an adjusted position of the members l5, [6 to match the resistance components and to cancel the reactance components of the terminal impedances Z1 and Z2. Specifically, the members l5 and I8 may be of conductive, dielectric, or magnetic materials, or a combination of these materials and, for a coaxial transmission line, are

preferably of circular cross section. The adjustan embodiment of the'invention which is useful L for matching one impedance to a pair of parallel impedances; and Fig. 4 is an impedance chart for the devices of Figs. 1 and 3 and is used to demonstrate their capabilities. 1 Referring now more particularly to the drawings, the device illustrated in Fig. 1 and shown diagrammatically in Fig. 2 comprises a high-frequency impedance-matching device which is adapted for connection between, and for matching at a given frequency, a pair of unequal impedances designated Z1 and Z: having any values within a substantial range of magnitude and able members l5 and I8 are movable by the insertion of a suitable tool, througna slot 40 in the outer conductor ll, into engagement with screws 25 which are loosened during adjustment of members-i5 and IE but are tightened thereafter to engage the inner conductor I! for the purpose of maintaining the members I5, 18 in adjusted position.

A brief discussion of the design of the impedance-matching device to provide proper matching for a pair of unequal impedances Z1 and Z: follows. When the members l5 and it are of conductive or dielectric materials, the outer di-' ameter of the inner conductor l2 and the inner diameter of the outer conductor I i are so proportioned that the characteristic impedance Zo' of the line is substantially greater than the geo-' metric mean impedance of the terminal impedances Z1 and Z2. When the members l5 and it are of conductive material and electrically engage the inner conductor 12, the outer diameters phase. This device comprises a lural-conductor 7 thereof are proportioned with relation tothe inmean values This applies also in the event the members II and It are'of conductive material but electrically engage only the outer conductor ii, there being the difference in this case that the'inner diameter of the members II and II are proportioned with relation to the diameter of the conductor ll so that the amid! "e Considering now the operation of the device, shown schematically in Finland 2, with imconductor I! to eifect the reduction of characteristic impedance last mentioned. If, on the other hand, the members I! and It are of dielectric material, the desired reduction of line characteristic impedance over the lengths of the members is effected by a choice of the dielectric constant of the material used.

In the alternative case where the members II and I. are of material having an eflectlve predominant magnetic characteristic, the transmisslon line l1, I2 is proportioned to have a characteristic impedance substantially less than the geometric mean impedance of Z1 and Z: and the eifective coemcient of magnetic permeability of the material of members I! and I8 is so selected with relation to the efle'ctive dielectric constant of the members that the characteristic impedance Z0" of the line II, I! is substantially greater than the geometric mean impedance of Z1 and Z: over the lengths of these members. The adjustable members, having an effective electrical length of approximately one-fourth the length of the line i II, I: and thus a range of movement equal at least to their own length, provide ample flexibility for matching unequal impedances Z1 and Z: over a wide range of impedance ratios.

It will be observed that the matching device is, in efiect, a transmission line consisting of a where D=the inner diameter of the outer conductor of the line portion under consideration, and d=the outer diameter of the inner conductor of the line portion considered.

For those line portions having adjustable members of dielectric material, the characteristic impedance given by Equation 1 must be multiplied by the reciprocal of the square root of the effective dielectric constant of the member, the efl'ective dielectric constant taking into account any air gaps between the adjustable member and either or both of the conductors I I and I2. Similarly, where the adjustable member is of magnetic material, the characteristic impedance given,

by Equation 1 must be multiplied by the square 1 pedances Z1 and Z2, the following relation should it pedances Z1 and Z: connected thereto, the-terminal impedances are matched bysliding the adjustable members II and" so as to vary the dis-. tance B, or the distance A, Fig, 2,,or boththe distances A and B. Thefadjustments in'this regard are somewhat similar to thoserequired to balance resistance and reactance components, of an unknown impedancein'an alternating current Wheatstone bridge.

For the range of impedance adjustment to include the geometric mean of the terminal imbe fulfilled:

"/%" V Z 1 Z:

where L=the total inductance. of the line conductors H and I2 including the inductance of the members I! and I6, I

C=the total capacitance between the line conductors II and I2 including the members l5 and I6. r a

The maximum range of adjustment, insofar as the length of the members II, It is concerned, is attained by the preferred length described above;

' namely, a physical length for each member equal and Z2, insofar as the characteristic impedances Z0 and Z0" are concerned, is attained when th following relation is fulfilled:

""Zo'Z0"=1/7TZ; For a length l of the line H, l2 equal to or less than one-half wave length 1 of the translated 1 wavesignal and for a value of K, defined below, less than unity, the following relation gives the approximate value of the reflection coefllcient r that can be introduced or cancelled:

.. where root of the efiective magnetic permeability and divided by the square root of the effective dielectric constant of the member.

In order to match most complex impedances Z1, Z2 over a substantial range of impedance ratios, two independent adjustments of the impedance-matching device are required. The adjustable members It and it provide this matching feature.

or whichever is positive =1 K 2 log Z0,

K=a factor expressing the diflerence of impedance in successive sections of the impedance-matching device.

From this, it will be apparent that a wider range of impedance matching is provided by longer lengths of the line H, l2. -It should be pointed out, however, that the. longest useful'lengthof line designed by these principles is one which latedelectromsgnetic-wavesignai.

allel at the other end of the device. This device ence numerals. Asecond hcllow'outer'conductor 21 at ri ht angles to the axis of conductor ll.

' members II thus form coaxial connectors for atcaasa I -1 provides an eifectiveelectrieal length'not substantially exceeding one wave length of the trans- Fig. 3 illustrates thigh-frequency impedance matching device for matching one terminal impedance coupled toone end of the device to a pair of terminal impedances connected in paris generally similarto that shown in Fig. 1 and similar elements are designated by similar refer- 21 is inserted through an aperture 30 in thehollow conductor] I. and is electrically connected at its mid-portion and ina symmetricalmanner to the latter conductor with the-axis of conductor At the extremities of hollowconductor 21 are a a j pair of insulating discs 28, 28 which support a second inner conductor 29 coaxiallywith the outer conductor 21 by means of a pair of :cen-

'trally disposed conductive pins 30. One end of conductor I2 is similarly supported in the first hollow conductor II by another disc 28 and a conductive pin 30. The other end of conductor I2 is conductively connected to the mid-portion g5 of conductor 29. Annular conductive members {I are secured to the outer ends-of hollow conductors H and 21 by means of'screws I to form a rigidunit. The conductive pins 30 and the annular 80 coupling the impedance-matching device of Fig.

3 in circuit with the external impedances whichare to be matched. -A conductive, disc it closes the end of the-conductor ll adjacent the conductor 21. Slot 0 provides access to members 5 II and It for adjustment purposes as in the Fig.

1 arrangement.

By way of example, an impedance-matching device embodying the present invention has been constructed for operation at a frequency near 500 megacycles for matching a -ohm impedance Z: to a 25-ohm impedance Z1 composed of two 50-oh'm impedances each 2Z1 connected in parallel, the geometric mean of the terminal at pedances thus being 35 ohms. This matching problem therefore involves an impedance ratio of 2 to 1. This device, when accuratel adjusted at one operating frequency, has been found to maintain a close impedance match over a wide range of operating frequencies or band width of approximately one-third to one-half the mean frequency. The following dimensions aregiven as illustrative of values of the elements whichv were utilized in this impedance-matching device for the application stated above:

Hollow outer conductor I i Length inches-- Inner diameter do 1 Hollow conductor 21: I a

Len th 2% Inner diameter do 7 Inner conductor l2:

Length do 51 5' Outer diameter ..do Inner conductor 29:

Length do 1% Outer diameter do Adjustable members I! and l8: 7 j

Length 4 do 1% 7 Outer diameter ....do..- V Impedance Zo' ohms 52 Impedance Z0" -do 18 Referring now to Fig. 4, there is illustrated on a hemispherical impedance chart a representative v chartat a 8 particular operating frequency for an impedance-matching device embodying thepresent invention and having its dimensions so chosen that the line II, I! has a length of one-quarter wavelength and a char- I acteristic impedance equal 'to 32: while each of the members it and I I has a length of one-sixtecnth wave length and a characteristic impedance equal to 0.82:. A chart of this type is useful indetermining the required settings ofthe adjustable members l5, II in aparticular impedance-matching device. -This chart is also useftfl as a graphical representation of the matchingcapabilities of sucha device. In this chart, the magnitude of any given impedance is expressed as a ratio between the value of that impedance and a value of resistance arbitrarily assigned the unit center of the chart. Ratio values are indicated by the lines of latitude. ratio values greater than unity lying above the straight horizontal line while those less than unity fall below this line. The possible phase angles of the given impedance are represented by the lines of longitude.

represents thev extreme impedance-matching capabilities of an impedance-matching device having the values of characteristic impedance mentioned in the preceding paragraph. The data from which this triangular figure was plotted was determined'by calculation using standard transmission line theory. In. this regard, it is convenient to derive a general equation for the impedance Z: seen at one end of the line when an impedanceZr is coupled to the other end of the line. In this general equation, there will be one term for each of the line sections A, B and C, Fig. 2, in which the impedance transformation effected by each section is expressed as a func- .tion of the length of the section. There will also be one term expressing the impedance transformation efrected by the line sections which include the members It and I, but each of these terms will involve no variables sincethe characteristic impedance and the length of each suchsection have fixed values. In performing these computations, it is convenient to assign for a given set of computations a fixed value to one of the spacings A or B and then to compute values of impedance transformation eflected by the impedance-matching device for selected values of the other spacing A or B. To plot the data thus obtained by calculation, an arbitrary value of resistance is assigned to the unit center of the impedance chart, as earlier explained. For the triangular'flgure shown on the impedance chart of Fig. 4, it was assumed that the impedance Z: was resistive and was equal to the value assigned to the center of the impedance chart. Z2 may, for example, correspond to a resistance having a value of 50 ohms.

It will be notedthat the triangular figure shown on the impedance chart is subdivided by a series of curves A and curves B which correspond to various possible A and B spacings, expressed in electrical degrees, of the adjustable members It and It. A and B spacings here rei'erredto correspond to those indicated in Fig. 2. The plotted data determined by calculation for-three values of dimension A for 0, l5 and 30 electrical degrees are plotted on the impedance chart and the resultant curves are indicated. as

' A-o'. A-15*, and s-ao' respectively. The

A-O' curve, for example, represents the values 7 of impedance transformation effected by the impedance-matching device with variations of the spacing B for a fixedspacing of zero electrical degrees for dimension A. similarlmthe curve A==15 represents the values of transformation with variation of the dimension B when the dimension A has a fixed value of 16 electrical degrees. Since the lengths of themembers II and II each correspond to 22.5 electricalcated byjhe point denoted A=45 as shown in aaoaasa V s m bers II and I. whereth'e latterare or magnetic materials, Furthenwhiie the'invem tion has been described in connection with a comission lines having adjustable members. of conthose shown and described in axial-impedance-matching "device, it will be apparent to one skilled in the art that the inventic'mv is also useful with open-pair or balanced transfiguration, construction and mounting similar to copending applications.

tion of the invention that a high-frequency impedance-matching device embodying the inven- I tioni's of minimum-physical size, is not critical the upper left of the figure. The triangular figure is also subdivided by three 13 curves indicated as ZB=, 3:15 and B=30 which represent the values of impedance transformation effected by thedevice for selected fixed values of the B spacing but with varying values of the A spacing. For a B spacing equal to 45, the mem I hers II and ii are in abutting relation and peeltioned at .one end of the transmission line ii, I:

members It, I8, assume that it is desired that the impedance-matching device transform an impedance Z1 having a value indicated by the point P on the impedance chart to the valueof impedance Z2, whereby the impedances Z1 and Z: are matched by the device. This point P lies on the intersection of the curves A=15 and B==0. Hence, if the member l5 is'adjusted to the end of the transmlssionline ll, I2 which reduces the B spacing to zero and if the adjustable member i6 is then adjusted to make the A spacing equal to electrical degrees, an' impedance Z1 having the value represented by the point P on the impedance chart is transformed to the value of impedance Z: at the opposite end of the of adjustment, and is not critical with regard to frequency or, expressed in another manner, is able to provide an exact impedance match at a selected operating frequency and a closely approximate impedance match over a wide range of operating frequencies. v

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A- high-frequency impedance-matching device adapted for connection between and for matching at a given frequency a pair of impedtransmission line, or conversely the impedance example, assume that an impedance Z1 having the value represented by the point P' on the impedance chart is to be matched by the impedancematching device to an impedance having the value Z2. As indicated by the inter-section of the broken lines which represent only portions of A and 3 curves, an impedance match is effected when the spacing B has a value of approximately 7%; electrical degrees and the spacing A a value of approximately 7 /2 electrical degrees.

While members i5 and it have been illustrated as closed or solid conductors slidable on the inner conductor, these members may have any of the configurations and mountings of, and may be formed in similar manner as, the adjustable members shown and described in the aforementioned copending applications. Thus the members l5 and it may be entirely of conductive, magnetic, or dielectric materials or may be formed of two or more of these materials in combination to provide an impedance-matching device having a particular desired characteristic.-

ances having any values within a predetermined range of magnitude and phase comprising, a plural-conductor transmission line adapted to be connected between said impedances and having a predetermined electrical length less than one wave length at said given frequency and a predetermined characteristic impedance differing in one sense from the geometric mean of said impedances, and a plurality of members positioned between the conductors of said line and independently adjustably movable axially therealong, each of said adjustable members having at said given frequency a predetermined efiective electrical length substantially less than one-half the length of said line and having its shape and material so selected as to cause the characteristic impedance of said line over the lengths of said members to differ from said geometric mean of said impedances in th opposite sense from the sense in which said line differs therefrom and by such magnitude as to enable said transmission line for an adjusted position of said members to match the resistance components and to cancel the reactance components of said pair of impedances.

2. A high-frequency impedance-matching device adapted for connection between and for matching at a given frequency a pair of impedances having any values within a predetermined range of magnitude and phase comprising, a plural-conductor transmission line adapted to be connected between said impedances and having a predetermined electrical length less than one wave length at said given frequency and a Predetermined characteristic impedance differing in one sense from the geometric mean of said impedances, and a plurality of members positioned between the conductors of said line and independently adjustably movable axially therealons.

of modemthe aforementioned acoaass v. 7 11 length of said line and'having its shape and material so selected as tocause the characteristic impedanceofsaidlineoverthelengthsofsaid.

members to differ from said geometric mean of sald impedances by pproximately the amount as that of said line but'in the-opposite sense from the sense in which said line diifer's therefrom toenable said line for an adjusted position of said members to match a plurality of members positioned between the conductors of said line and independently adjustably movable axially therealong, each of said adjustable members having at said given frequency a predetermined effective electrical length substantially less than one-half the length of said a line and having its shape and material so selected as to cause the characteristicimpedance of said line over the lengths of said members to be less than said geometric mean of said impedances by such magnitude as to enable said transmission line for an adjusted position of said members to match the resistance components and to cancel thereactance components of said pair of impedances.

' 4. A high-frequency impedance-matching device adapted-for connection between and for matching at a given frequency 'a pair of impedances having any values within a predetermined range of magnitude and phase comprising, a plural-conductor transmission-line adapted to be connected between said impedances and having a predetermined electrical length less than:

one wave length at said given frequency and a predetermined characteristic impedance greater than the geometric mean of said impedances, and f a plurality of conductive members positioned between the conductors of said line but spaced 1 from at least one conductor thereof and independently adjustably movable axially therealong.

each of said adjustable members having at said given frequency a predetermined effective elec- 1 trical length substantially less than one-half the 1 length of said line and having its shape so selected 1 as to cause the characteristic impedance of said 1 line over the lengths of said members to be less 1 than said geometric mean of said impedances by i such magnitude as to enable said transmission line for an adjusted position of said members to 1 match the resistance components and to cancel the reactance components of said pair of im- 1 pedances.

5. A high-frequency impedance-matching device adapted for connection between and for 1 matching at a given frequency a pair of impedances having any values within a predetermined range of magnitude and phase comprising, f a plural-conductor transmission line adapted to be connected betweensaid impedances and hav- 1 ing a predetermined electrical length less than 1 one wave length at said given frequency and a A predetermined characteristic impedance greater 1 than the geometric mean of said impedances, and

pair of impedances.

' a plurality of members of dielectric asitioned between the conductors of said line and.

independently adjustably movable axially there-q along, eachof said adjustable members having at said given frequency apredetermh ied eifective electrical length substantially less than one-half the length of said line and having its shapeso selected'as to cause the characteristic impedance of said line over the lengths of said members to be less than said geometric mean of said impedances by such magnitude as to enable said a transmission line for an adjusted position of said members to match the resistance components and to cancel the reactance components of said 6. A high-frequency impedance-matching device adapted for connection between and for matching at a given frequency a of impedances having any values within a predetermined range of magnitude and phase comp g, a plural-conductor transmission line adapted to be connected between said impedances and h ving a predetermined electrical length less than one wave length at said given frequency and a predetermined characteristic impedance less than the geometric mean of said impedances, and a plurality of members positioned between the. conductors of said line and independently adjustably' movable axially therealon'g, each of said adjustable'members having at said given frequency a predetermined eifective' electrical length substantially lem thanone-half the length of said line and having its shape and material so selected as to cause the characteristic impedance of said line over the lengths of said members to be greater than said geometric mean of said impedances by such magnitude as to enable said transmission line for an adjusted position of said members to match the resistance components and to cancel the reactance components of said pair of impedances. v

7. A high-frequency impedance-matching device adapted for connection between and for matching at a given frequency a pair of imped ances having any values within a predetermined range of magnitude and phase comprising, a plural-conductor transmission line adapted to be connected between said impedances and having a predetermined electrical length less than one wave length at said given frequency and a predetermined characteristic impedance less than the geometric mean of said impedances. and a plurality of members of magnetic material positioned between the conductors of said line and independently adjustably movable axially therealong, each of said adjustable members having at said given frequency a predetermined eflective electrical length substantially less than one-half the length of said line and having its shapeso selected as to cause the characteristic impedance of said line over the lengths of said members to be greater than said geometric mean of said impedances by such magnitude as to enable said transmission line for an adjusted position of said members to match the resistance components and to cancel the reactance components of said pair of impedances.

8. A high-frequency impedance-matching device "adapted for connection between and for matching at a given frequency a pair of impedances having any values within a predetermined range of magnitude and phase com-' 13 than one wave length at said given frequency and a predetermined characteristic impedance differing in one sense from the geometric mean of said impedances, and a plurality of members positioned within said line between the conductors thereof and independently adjustably movable axially along said line, each of said adjustable members having at said given frequency a predetermined eifective electrical length substantially less than one-half the length of said line and having its shape and material so selected as to cause the characteristic impedance of said line over the lengths of said members to differ from said geometric mean of said impedances in the opposite sense from the sense in which said line differs therefrom and by such magnitude as to enable said transmission line for an adjusted position of said members to match the resistance components and to cancel the reactance components of said pair of impedances.

9. A high-frequency impedance-matching device adapted for connection between and for matching at a given frequency a pair of impedances having any values within a predetermined range of magnitude and phase comprising, a coaxial transmission line adapted to be connected between said impedances and having a predetermined electrical length less than one wave length at said given frequency and a predetermined characteristic impedance differing in one sense from the geometric mean of said impedances, and a plurality of members each enclosing the inner conductor of said line and independently adjustably movable axially along said line, each of said adjustable members having at said given frequency a predetermined effective electrical length substantially less than one-half the length of said line and having its shape and material so selected as to cause the characteristic impedance of said line over the lengths of said members to differ from said geometric mean of said impedances in the opposite sense from the sense in which said line differs therefrom and by such magnitude as to enable said transmission line for an adjusted position of said members to match the resistance components and to cancel the reactance components of said pair of impedances.

10. A high-frequency impedance-matching device adapted for connection between and for matc ing at a given' frequency a pair of impedances having any values within a predetermined range of magnitude and phase comprising, a plu- .14 rel-conductor transmission line adapted to be connected between said impedances and having an electrical length of approximately one-quarter wave length at said given frequency and a predetermined characteristic impedance differing in one sense from the geometric mean of said impedances, and a plurality of members positioned between the conductors of said line and independently adjustably movable axially therealong, each of adjustable members having at said given frequency an effective electrical length of approximately one-sixteenth wave length and having its shape and material so selected as to cause the characteristic impedance of said line over the lengths of said members to differ from said geo- -metric mean of said impedances in the opposite sense from the sense in which said line differs therefrom andby such magnitude as to enable said transmission line for an adjusted position of said members to match the resistance components and to cancel the reactance components of said pair of impedances.

11. A high-frequency impedance-matching device adapted for connection between and for matching at a given frequency a pair of impedances having any values within a predetermined range of magnitude and phase comprising, a plural-conductor transmission line adapted to be connected between said impedances and having an electrical length of approximately one-quarter wave length at said given frequenc and a predetermined characteristic impedance differing in one sense from the geometric mean of said impedances, and a plurality of members positioned between the conductors of said line and independently adjustably movable axially therealong, each of said adjustable members having at said given frequency an effective electrical length of approximately one-sixteenth wave length and having its shape and material so selected as to' cause the characteristic impedance of said line over the lengths of said members to differ from said geometric mean of said impedances by approximately the same amount as that of said line but in the opposite sense from the sense in which said line differs therefrom to enable said transmission line for an adjusted position of said members to match the resistance components and to cancel the reactance components of said pair of impedances.

HAROLD A. WHEELER.

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