High-power coupler synthesis

Abstract

A way of interconnecting noncommensurate lengths of coupler type elements with uncoupled lines is disclosed. The synthesis of inductive and capacitive forward transverse characteristics is taught by varying the number of coupled lines employed in making up a coupler type element to be included in an overall structure as disclosed in U.S. Pat. No. 3,761,843. FIELD OF THE INVENTION This invention relates to the interconnection of noncommensurate lengths of coupler type elements with uncoupled line lengths. BACKGROUND OF THE INVENTION In my prior U.S. Pat. No. 3,761,843, which issued on Sep. 25, 1973, I disclosed a system in which noncommensurate lengths of coupled and uncoupled lines were interconnected to produce four port networks having designable response characteristics in a common impedance system. In that patent it was taught that by adjusting the length of a pair of coupled lines and a pair of uncoupled lines interconnecting the pair of coupled lines varying response characteristics could be achieved in a common impedance system. It was specifically taught that such an interconnection of lines in the common impedance system could be made equivalent in amplitude response to different impedance quarter wave structures. It was further taught that by adding additional uncoupled lines a complete equivalency could be obtaining in both amplitude and phase. It has been found that many response characteristics which were not achievable in the past can be synthesized in accordance with the teaching of U.S. Pat. No. 3,761,843. It has been found, however, that certain limitations exist upon the useful structures which can be practically realized in accordance with the teachings thereof. One of the limitations taught in the above-mentioned patent which limits the physical realizability of common impedance systems as heretofore constructed is the requirement that the even mode impedance of the common impedance system must be equal to or greater than the equivalent quarter wave impedance of the highest impedance structure whose response is being simulated. It has been found when synthesizing multi-element devices that the requirement of a high even mode impedance results in narrow lines of close spacing. The narrowness of the lines ultimately limits the overall power handling capability of the device. Further, the physical tolerances necessary to produce controlled thin lines ultimately limits the realizability of the device itself. Further, the close spacing between lines also requires physical tolerances on dielectric materials which are not commerically realizable. In an article in MICROWAVES of Apr. 1965, J. Paul Shelton et al. teach that several loose coupled devices can be tandem connected to simulate a more tightly coupled device. The result of this tandemization of loosely coupled devices results in a higher power handling capability and a relaxation of manufacturing tolerances. In the Shelton et al. disclosure, each individual coupler making up the synthesis is always a quarter wavelength long at the center operating frequency. Further, Shelton et al. goes on to disclose the interconnection of pairs of interconnected quarter wavelength couplers of common impedance with additional sets of quarter wave couplers of different impedances in order to synthesize varying amplitude characteristics. There, Shelton et al. taught the tandemization of quarter wave couplers in the forward scattered mode to achieve amplitude synthesis in multi-section couplers. The shelton et al. system was still basically a commensurate one in a variable impedance environment even though parts of commensurate devices did have common impedances. BRIEF DESCRIPTION OF THE INVENTION In accordance with the teachings of this invention it has been found that noncommensurate structures can be synthesized in a common impedance system wherein the even mode impedance in the common impedance system can be less than the even mode impedance of quarter wave structures being simulated wherein tandem connected lengths of coupled lines of common impedance are interconnected in a backward scattered sense with uncoupled lines. Each of the coupled lines tandemly connected are less than a quarter wavelength long and may be noncommensurate in length within a tandem connected element so long as they are symmetric. The resulting structure adds an additional degree of design freedom in noncommensurate common impedance systems that were not conceived or taught either in my above-mentioned prior patent or the Shelton et al. article. The system taught herein produces a degree of design freedom resulting in useful structures far exceeding the combined results taught by these two references.

Description

DESCRIPTION OF THE DRAWINGS

A more complete understanding of the invention can be had by referring to the following detailed description of the invention and the drawings in which:

FIG. 1 is a plain view of a circuit board having conductors or lines on both sides thereof which form a coupler type element in accordance with the teachings of this invention;

FIG. 2 is a sectional view taken along the line 2--2 of FIG. 1, showing the layers making up a coupler type element of this invention; and

FIG. 3 is a cut-away view of a portion of another coupler type element constructed in accordance with the teachings of this invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, we see a printed circuit board 10 having conductive lines printed on opposite sides thereof to form a multi-element coupler type element in accordance with the teachings of this invention. In FIG. 1 the conductive lines such as line 11, having the outline thereof shown in solid lines, is on the top surface of the printed circuit board 10. The line such as line 12 having its outline shown as dashed lines is on the back surface of the printed circuit board 10. The lines such as line 13, which are shown as cross hatched, have lines on both sides of the printed circuit board 10.

FIG. 2 shows a section through the circuit board 10, also showing the additional layers of boards which provide the ground planes for the coupler type device of this invention. It can be seen that a line 14 lies on the top surface of the board 10 while a line 16 is on the bottom surface of the board 10. A pair of conducting ground planes, 17 and 18, each sandwiched by a pair of insulating boards, 19 and 21, respectively, complete the structure of the coupler type element.

Referring again to FIG. 1, we see that there are three coupled sections 22, 23 and 24 connected by two uncoupled sections 26 and 27 which make up the coupler type element of FIG. 1. Each of the coupled sections 22, 23 and 24 include three pairs of coupled lines, each less than a quarter wavelength long, interconnected by shorter lengths of uncoupled lines. The overall effect of the connection of the three pairs of coupled lines by the short lengths of uncoupled lines is analogous in some respects to one pair of coupled lines as shall become apparent below.

The section 22 includes pairs of coupled lines 28, 29 and 31. As discussed before, each of these pairs of coupled lines 28, 29 and 31 are shown as cross hatched which means that a line appears for each on each side of the printed circuit board 10. The lines 28, 29 and 31 are considered coupled lines because the line on one side of the board 10 is overlaying the line on the other side of the board 10 and therefore substantial electromagnetic coupling therebetween exists. A short length of uncoupled line 32 connects the left sides of the portions of the coupled lines 28 and 29 which are on the top surface of the printed circuit board 10 and uncoupled line 33 connects the right sides of the portions of the coupled lines 28 and 29 which are on the back surface of the printed circuit board 10. In a like manner uncoupled lines 34 and 36 connect the portions of the coupled lines 29 and 31 which are on the back of the printed circuit board 10 and shown to the left in FIG. 1 and the top portions of the coupled lines 29 and 31 shown on the right side of FIG. 1, respectively. These interconnections, as discussed immediately above, combine the coupled lines 28, 29 and 31 into the coupled section 22. It will be appreciated that the lengths of uncoupled lines 32, 33, 34 and 36 are short when compared with the lengths of the coupled lines 28, 29 and 31. It should further be observed that the uncoupled lines 32, 33, 34 and 36 are transverse to the coupled lines 28, 29 and 31 so that they can be maintained short in length and be relatively widely spaced one from the other to prevent large amounts of electromagnetic coupling between each other.

It should be noted that the coupled lines 28 and 31 are of equal length while the coupled line 29 is of a different length. It is preferred that the coupled section 22 be symmetrical but there is no need for equality in all of the coupled lines. It should be noted that by the construction as described above, the even and odd mode impedances of each of the coupled lines 28, 29 and 31 are equal due to the size of the lines and spacing therebetween. They also each exhibit equal phase velocity and even and odd modes of excitation.

The characteristic impendance of the coupled lines can be expressed as Z.sub.t which is equal to the square root Z.sub.e .times. Z.sub.o, where; Z.sub.e is the even mode impedance thereof when each of the terminals of the particular coupled line is terminated in impedance of Z.sub.t, and Z.sub.o is the odd mode impedance when each of the terminals of the particular coupled line are terminated in the impedance of Z.sub.t.

The coupled section 22, as described above, can be interconnected with other similar sections as shown in FIG. 1 by pairs of uncoupled lines, such as uncoupled line 37, 38, 39 and 41 to provide networks in accordance with the teachings of my prior U.S. Pat. No. 3,761,843. One advantage of employing coupled sections such as the coupled section 22 instead of merely a pair of coupled lines, as taught in my prior patent, is that equivalent quarter wave impedance devices can be synthesized with the present invention which have a higher even mode impedance than the even mode impedance Z.sub.e of the individual coupled lines 28, 29 and 31. This is a substantial advantage in fabrication of devices and enables the synthesis of devices not previously physically realizable.

In the preferred embodiment of this invention the characteristic impedance Z.sub.t of the coupled lines 28, 29 and 31 are equal. Useful devices can be synthesized in which the characteristic impedance of the coupled line 29 differs from the characteristic impedance of the coupled lines 28 and 31. This could be easily achieved in a pre-printed circuit configuration by having the two lines which make up the coupled line 29 slightly out of registration one with the other.

Another advantage of employing coupled sections in place of individual coupled lines in a device as taught in U.S. Pat. No. 3,761,843 is that devices having both poles and zeroes in the forward transmission path can be achieved without the rotation of elements required by my prior teaching in U.S. Pat. No. 3,660,783. It has been found that when any odd number of coupled lines are interconnected, as shown in FIG. 1, to form a coupled section, and inductive form of transmission path results. On the other hand, when even numbers of coupled lines are employed (as shown in FIG. 3) a capacitive type forward transmission characteristic results. Combinations of coupled sections having even and odd numbers of coupled lines therein can be interconnected to form resonant structures not achievable in accordance with the prior teaching of U.S. Pat. No. 3,761,843.

Referring particularly now to FIG. 3, we see a cutaway view of a coupler type element showing, in particular, two coupled sections 20, and 30 interconnected by a pair of uncoupled lines 42 and 43 in accordance with the teachings of U.S. Pat. No. 3,761,843. Each of the coupled sections 20 and 30 have a pair of coupled lines 44 and 46; and 47 and 48, respectively. The coupled lines 44 and 46 are connected on the back surface of the printed circuit board by a short length of uncoupled line 49 and on the front side of the printed circuit board by an uncoupled line 51. In a like fashion the coupled lines 47 and 48 are interconnected by the uncoupled lines 52 and 53. The structure as thus described with respect to FIG. 3 provide a coupler type element which can be employed to match the amplitude response of a quarter wave coupler in which the forward transmission path has a capacitive characteristic.

While this invention has been described with regard to particular embodiments thereof it should, of course, be understood that numerous other embodiments which fall within the spirit and scope thereof will become obvious to those of ordinary skill in the art in light thereof.

Claims

What is claimed is:

1. A distributed parameter device including:

first and second lines electromagnetically coupled to each other; said first line providing first and second terminals at opposite ends thereof; said second line providing third and fourth terminals at opposite ends thereof; said electrical length of said first and second lines being equal; said first and second lines exhibiting an even mode impedance of Z.sub.e when said first, second, third and fourth terminals are terminated in an impedance of Z.sub.t; said first and second lines exhibiting an odd mode impedance of Z.sub.o when said first, second, third and fourth terminals are terminated in said impedance of Z.sub.t, where:

Z.sub.t= .sqroot. Z.sub.e Z.sub.o;

said first and second coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

third and fourth lines electromagnetically coupled to each other; said third line providing fifth and sixth terminals at opposite ends thereof; said fourth line providing seventh and eighth terminals at opposite ends thereof; said electrical length of said third and fourth lines being equal; said third and fourth lines exhibiting said even mode impedance of Z.sub.e when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth lines exhibiting said odd mode impedance of Z.sub.o when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

a fifth line for connecting said second terminal to said fifth terminal;

a sixth line for connecting said fourth terminal to said seventh terminal;

said fifth and sixth lines being uncoupled lines;

seventh and eighth lines electromagnetically coupled to each other; said seventh line providing ninth and tenth terminals at opposite ends thereof; said eighth line providing eleventh and twelfth terminals at opposite ends thereof; said electrical length of said seventh and eighth lines being equal; said seventh and eighth lines exhibiting said even mode impedance of Z.sub.e when said ninth, tenth, eleventh and twelfth terminals are terminated in said impedance of Z.sub.t; said seventh and eighth lines exhibiting an odd mode impedance of Z.sub.o when said ninth, tenth, eleventh and twelfth terminals are terminated in said impedance of Z.sub.t, said seventh and eighth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

ninth and tenth lines electromagnetically coupled to each other; said ninth lines providing thirteenth and fourteenth terminals at opposite ends thereof; said tenth line providing fifteenth and sixteenth terminals at opposite ends thereof; said electrical length of said ninth and tenth lines being equal; said ninth and tenth lines exhibiting said even mode impedance of Z.sub.e when said thirteenth, fourteenth, fifteenth and sixteenth terminals are terminated in said impedance of Z.sub.t, said ninth and tenth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

an eleventh line for connecting said tenth terminal to said thirteenth terminal;

a twelfth line for connecting said twelfth terminal to said fifteenth terminal;

said eleventh and twelfth lines being uncoupled lines; and

means for connecting said third and eighth terminals to said eleventh and sixteenth terminals respectively.

2. A distributed parameter device including:

first and second lines electromagnetically coupled to each other, said first line providing first and second terminals at opposite ends thereof; said second line providing third and fourth terminals at opposite ends thereof; said electrical length of said first and second lines being equal; said first and second lines exhibiting an even mode impedance of Z.sub.e when said first, second, third and fourth terminals are terminated in an impedance of Z.sub.t; said first and second lines exhibiting an odd mode impedance of Z.sub.o when said first, second, third and fourth terminals are terminated in said impedance of Z.sub.t, where:

Z.sub.t= .sqroot. Z.sub.e Z.sub.o;

said first and second coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

third and fourth lines electromagnetically coupled to each other; said third line providing fifth and sixth terminals at opposte ends thereof; said fourth line providing seventh and eighth terminals at opposite ends thereof; said electrical length of said third and fourth lines being equal; said third and fourth lines exhibiting dual even and odd mode impedance when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t, said third and fourth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

a fifth line for connecting said second terminal to said fifth terminal; and

a sixth line for connecting said fourth terminal to said seventh terminal;

said fifth and sixth lines being uncoupled lines;

seventh and eighth lines electromagnetically coupled to each other; said seventh line providing ninth and tenth terminals at opposite ends thereof; said eighth line providing eleventh and twelfth terminals at opposite ends thereof; said electrical length of said seventh and eighth lines being equal; said seventh and eighth lines exhibiting said even mode of Z.sub.e when said ninth, tenth, eleventh and twelfth terminals are terminated in said impedance of Z.sub.t; said seventh and eighth lines exhibiting said odd mode impedance of Z.sub.o when said ninth, tenth, eleventh and twelfth are terminated in said impedance of Z.sub.t, said seventh and eighth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

a ninth line for connecting said third terminal to said tenth terminal;

a tenth line for connecting said first terminal to said twelfth terminal;

said ninth and tenth lines being uncoupled lines; and

said first and fourth; second and third; sixth and seventh; fifth and eighth; ninth and twelfth; and tenth and eleventh terminals respectively being physically adjacent to each other.

3. The distributed parameter device as defined in claim 2 for operating at a center operating frequency in which each of said first, second, third, fourth, seventh and eight lines are less than a quarter wavelength long at said center operating frequency.

4. A distributed parameter device including:

first and second lines electromagnetically coupled to each other; said first line providing first and second terminals at opposite ends thereof; said second line providing third and fourth terminals at opposite ends thereof; said electrical length of said first and second lines being equal; said first and second lines exhibiting an even mode impedance of Z.sub.e when said first, second, third and fourth terminals are terminated in an impedance of Z.sub.t; said first and second lines exhibiting an odd mode impedance of Z.sub.o when said first, second, third and fourth terminals are terminated in said impedance of Z.sub.t, where:

Z.sub.t= .sqroot. Z.sub.e Z.sub.o;

said first and second coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

third and fourth lines electromagnetically coupled to each other; said third line providing fifth and sixth terminals at opposite ends thereof; said fourth line providing seventh and eighth terminals at opposite ends thereof; said electrical length of said third and fourth lines being equal; said third and fourth lines exhibiting dual even and odd mode impedances when said fifth sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t, said third and fourth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

a fifth line for connecting said second terminal to said fifth terminal; and

a sixth line for connecting said fourth terminal to said seventh terminal;

said fifth and sixth lines being uncoupled lines;

seventh and eighth lines electromagnetically coupled to each other; said seventh line providing ninth and tenth terminals at opposite ends thereof; said eighth line providing eleventh and twelfth terminals at opposite ends thereof; said electrical length of said seventh and eighth lines being equal; said seventh and eighth lines exhibiting said even mode of Z.sub.e when said ninth, tenth, eleventh and twelfth terminals are terminated in said impedance of Z.sub.t; said seventh and eighth lines exhibiting said odd mode impedance of Z.sub.o when said ninth, tenth, eleventh and twelfth terminals are terminated in said impedance of Z.sub.t, said seventh and eighth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

a ninth line for connecting said third terminal to said tenth terminal;

a tenth line for connecting said first terminal to said twelfth terminal;

said ninth and tenth lines being uncoupled lines; and

said third and seventh lines are equal in length and said first line is different in length than said third and seventh lines.

5. The distributed parameter device as defined in claim 4 in which said third line is longer than said first line.

6. A distributed parameter device having a center operating frequency including:

first and second lines electromagnetically coupled to each other; said first line providing first and second terminals at opposite ends thereof; said second line providing third and fourth terminals at opposite ends thereof; said electrical length of said first and second lines being equal; said first and second lines exhibiting an even mode impedance of Z.sub.e when said first, second, third, and fourth terminals are terminated in an impedance of Z.sub.t; said first and second lines exhibiting an odd mode impedance of Z.sub.o when said first, second, third and fourth terminals are terminated in said impedance of Z.sub.t, where:

Z.sub.t= .sqroot. Z.sub.e 2.sub.o

where first and second coupled lines exhibiting equal phase velocity in said even and odd modes of excitation; said first and fourth terminals being physically adjacent to each other; said second and third terminals being physically adjacent to each other;

third and fourth lines electromagnetically coupled to each other; said third line providing fifth and sixth terminals at opposite ends thereof; said fourth line providing seventh and eighth terminals at opposite ends thereof; said electrical length of said third and fourth lines being equal; said third and fourth lines exhibiting said even mode impedance of Z.sub.e when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth lines exhibiting said odd mode impedance of Z.sub.o when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth coupled lines exhibiting equal pphase velocity in said even and odd modes of excitation; said fifth and eighth terminals being physically adjacent to each other; said sixth and seventh terminals being physically adjacent to each other;

a fifth line for connecting said second terminal to said fifth terminal; and

a sixth line for connecting said fourth terminal to said seventh terminal;

said fifth and sixth lines being uncoupled lines;

said first and third lines being less than a quarter wavelength at said center operating frequency.

7. A distributed parameter device having a center operating frequency including:

first and second lines electromagnetically coupled to each other; said first line providing first and second terminals at opposite ends thereof; said second line providing third and fourth terminals at opposite ends thereof; said electrical length of said first and second lines being equal; said first and second line exhibiting an even mode impedance of Z.sub.e when said first, second, third and fourth terminals are terminated in an impedance of Z.sub.t; said first and second lines exhibiting an odd mode impedance of Z.sub.o when said first, second, third and fourth terminals are terminated in said impedance of Z.sub.t, where:

Z.sub.t= .sqroot. Z.sub.e Z.sub.o;

said first and second coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

third and fourth lines electromagnetically coupled to each other; said third line providing fifth and sixth terminals at opposite ends thereof; said fourth line providing seventh and eighth terminals at opposite ends thereof; said electrical length of said third and fourth lines being equal; said third and fourth lines exhibiting said even mode impedance of Z.sub.e when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth lines exhibiting said odd mode impedance of Z.sub.o when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

a fifth line for connecting said second terminal to said fifth terminal; said fifth line covering the shortest distance between said second and fifth terminals;

a sixth line for connecting said fourth terminal to said seventh terminal; said sixth line covering the shortest distance between said fourth and seventh terminals;

said first and third lines being less than a quarter wavelength at said center operating frequency.

8. A distributed parameter device having a center operating frequency including:

first and second lines electromagnetically coupled to each other; said first line providing first and second terminals at opposite ends thereof; said second line providing third and fourth terminals at opposite ends thereof; said electrical length of said first and second lines being equal; said first and second lines exhibiting an even mode impedance of Z.sub.e when said first, second, third and fourth terminals are terminated in an impedance of Z.sub.t; said first and second lines exhibiting an odd mode impedance of Z.sub.o; when said first, second third and fourth terminals are terminated in said impedance of Z.sub.t, where:

Z.sub.t= .sqroot. Z.sub.e Z.sub.o;

said first and second coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

third and fourth lines electromagnetically coupled to each other; said third line providing fifth and sixth terminals at opposite ends thereof; said fourth line providing seventh and eighth terminals at opposite ends thereof; said electrical length of said third and fourth lines being equal; said third and fourth lines exhibiting said even mode impedance of Z.sub.e when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth lines exhibiting said odd mode impedance of Z.sub.o when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

a fifth line for connecting said second terminal to said fifth terminal; said fifth line being transverse to said first line; and

a sixth line for connecting said fourth terminal to said seventh terminal; said sixth line being transverse to said second line;

said first and third lines being less than a quarter wavelength long at said center operating frequency.

9. A distributed parameter device having a center operating frequency including:

first and second lines electromagnetically coupled to each other; said first line providing first and second terminals at opposite ends thereof; said second line providing third and fourth terminals at opposite ends thereof; said electrical length and second lines exhibiting an even mode impedance of Z.sub.e when said first, second, third and fourth terminals are terminated in an impedance of Z.sub.t; said first and second lines exhibiting an odd mode impedance of Z.sub.o when said first, second, third and fourth terminals are terminated in said impedance of Z.sub.t, where:

Z.sub.t= .sqroot. Z.sub.e Z.sub.o;

said first and second coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

third and fourth lines electromagnetically coupled to each other; said third line providing fifth and sixth terminals at opposite ends thereof; said fourth line providing seventh and eighth terminals at opposite ends thereof; said electrical length of said third and fourth lines being equal; said third and fourth lines exhibiting said even mode impedance of Z.sub.e when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth lines exhibiting said odd mode impedance of Z.sub.o when said fifth, sixth, seventh and eighth terminals are terminated in said impedance of Z.sub.t; said third and fourth coupled lines exhibiting equal phase velocity in said even and odd modes of excitation;

a fifth line for connecting said second terminal to said fifth terminal, and

a sixth line for connecting said fourth terminal to said seventh terminal; said fifth and sixth lines being spaced apart along the entire lengths thereof by a distance substantially equal to the lengths of said first and second lines;

said first and third lines being less than a quarter wavelength at said center operating frequency.