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Publication numberUS2611822 A
Publication typeGrant
Publication dateSep 23, 1952
Filing dateFeb 3, 1945
Priority dateFeb 3, 1945
Publication numberUS 2611822 A, US 2611822A, US-A-2611822, US2611822 A, US2611822A
InventorsRoderic Bliss William
Original AssigneeRoderic Bliss William
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Coupling device
US 2611822 A
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Description  (OCR text may contain errors)

Sept. 23, 1952 w R, Buss 2,611,822

COUPLING DEVICE Filed Feb. 3, 1945 W. RODERIC BLIS-S @3M @Wdfed @www Patented Sept. 23, 1952 UNITED vSTATES PATENT OFF-ICE ooUPLING DEVICE william Rosario Bliss, Washington, n. c.

Application AFebruary 3, 1945, Serial No. 576,111 1:?. claims. (01.178444) (Granted under the act of March y3, 1883, as amended April A30, 1928; 370 O. G. 757) This invention relates to the problem of -coupling a source of high frequency energy to a low impedance load. The invention is more particularly directed to the problem of coupling a tuned circuit to a low impedance transmission line.

Whereas the invention has many applications, it lis of special utility in coupling the tank circuit of a radio transmitter to a low impedance transmission line feeding the antenna.

vIt is an object of the invention' to provide means matching a low impedance transmission line or coupling the line` to ahigh impedance electrical network.

^ It is a further object of the invention to provide a highly eicient coupling network `for feeding a low impedance transmission line.

Yet another object of the invention is `to provide means for electrically coupling a low impedance transmission line toanother network at high efficiency over` a wide frequency band.

It is a more specific object of the invention to provide means for coupling a radio frequency generator to a low impedance transmission line through a coupling device matching the transmission line impedance.

The coupling elements of 'the 'presentzinvention are primarily intended for application at vhigh frequency work, where difculty is encountered in eiiciently transferring large amounts of energy from a tuned circuit to "a low impedance line.

Coupling elements previously used in this field have been relatively ineffective due largely tothe fact that their impedance varies considerably with small frequency variations, and further that their impedance does not match that of the transmission line.

' The invention will be further described with reference to the exemplary embodiments shown in .the drawing, wherein:

Figure 1 illustrates a circuit diagram, partially schematic, of a high-frequency signal transmitting system employing therein an embodiment of the invention.

Figure 2 shows a transmitter circuit similar to Figure 1 in which another embodiment of the invention is shown in perspective.

Figure 3 illustrates a, plan view of a portion of the resonant tank circuit of a transmitter and the modified coupling device shown in Figure 2 in an operating position.

Figure 4 is a perspective view of another embodiment of the invention in which a block of dielectric material separates the loopfrom a supporting ground plate, and

Figure 5 is a perspective view of another embodiment of the invention wherein the separated metallic plates form the energy pickup device Coupling elements of the present invention may be employed for either electromagnetic Lor electrostatic coupling. The invention as shown in Figure 1 includes an electromagnetic coupling loop. The source of energy in the system ofA Figurel l consists of a resonant circuit'whichylas shown, is a resonant line section II. This sec'- tion comprises line elements IZ and I3 shorted across one end by conductor I4. For excitation the resonant circuit is coupled in an oscillator network, and for this purpose line I3 is connected to the anode of tube Il).4 `Line element I2 is connected through blocking condenser I5 to the .grid of tube I0, which is returned to ground through resistor I'I. Anode potential is supplied' through radio frequency choke I6. The operating frequency may be varied over a range by condenser 9 connected across the open ends of the line sec` The resonant circuit'llI of Figure 1 is coupled to a load, shown as antenna 23, through a low impedance concentricftransmission line 8. The impedance of line J8 is matched to that of antenna 23 by transformersection 22. Line 8 therefore constitutes a flat line. i 1

Line 8 is coupled to resonant circuit II inductively through loop I8. This loop is specifically constructed to have a characteristic im.- pedance matching that of rline 8. Since this eliminates any electrical discontinuity between the coupling element and the line itself, standing waves with their attendant loss of energyare eliminated from the coupling element itself. Further, the characteristic impedance of the coupling element is not dependent upon lthe frequency of excitation, and consequently maximum coupling may be effected with efficiency over a comparatively Wide band. As a result, in a system such as shown in Figure 1, the operating frequency may be varied by `condenser 9 without requiring attendant adjustment of the coupling y D" is the width of the conducting strip, d is the spacing of the horizontal parallel portions of the strip, and e is the dielectric constant of the interposing material. In the embodiment shown in Figure 1 air is employed as the dielectric, having a dielectric constant equal of unity. For the normal range of low impedance lines D is larger than 41.

In the system shown in Figure 1, the transmission line coupling element I8 is short-circuited at its end, and has a rectangular formation. If transmission line 8 is assumed to have a characteristic impedance of 50 ohms, the ratio of width to spacing of the coupling element to obtain this value with air dielectric is substantially 6.5. In the drawings for the purpose of clarity of illustration, a smaller ratio is shown. Another embodiment of the operating prin- `ciples of the invention is shown in the electromagnetic couplingelement of Figures 2 and 3. As in the system of Figure 1, the energy is derived from a resonant line section I I and is coupled into a low impedance concentric line 8, which is terminated by a matching load not shown. In this formof the invention the coupling section comprises a flat conductor positioned above a metallic ground plate. In this construction, the characteristic impedance of the coupling element as a transmission line also depends upon the ratio of the Width of the conductor to its spacing from the .ground plate, and also upon the dielectric constant of the interposed material. Due to the fact that one of thetransmission line conductors is effectively extended to form the ground plate, the characteristic impedance diifers from that of section I8 shown in Figure 1, and may be found substantially'according to the formula:

D is the width of the upper transmission line member comprising the flat elongated conductor, and d is the spacing between this conductor and the ground plate. e is the dielectric constant of the interposed material.

In the embodiment shown in Figure 2 metallic member 24 constitutes the ground plate. The transmission line conductor, which is connected to the inner element of concentric line 8, is shown at 2B. This conductor may be curved in its own plane to form a flat loop above the ground plate, ,as is' shown in Figure 2. Ihe upper conductor is positioned above ground plate 24 on insulating blocks 25.

In order to obtain magnetic coupling to the tuned circuit II shown in Figure 2, the conductor positioned abovethe ground plate is connected at its extremity thereto( electrical contact with ground plate 24.

As in the system shown in Figure 1, it will be vunderstood thatthe dimensions and proportions of the coupling element shown in Figure 2 are .f

Asuch as to obtain an impedance match between this element and the concentric line' 8, in accordance with the formula given above.

A top elevation view of thelsystem'shown in .Figure 2 is disclosed in Figure 3. As is preferable For this purpose end 28 of conductor 2G is turned downwardly to form an for magnetic coupling, the coupling loop 2S is positioned closely beneath the high current end of the resonant line section I I.

Whereas in the system of Figures 2 and 3 the average dielectric constant of the material interposed between coupling 26 and ground plate 24 may be considered to be substantially unity, in

vthe embodimentshown in Figure 4 a dielectric sheet 30 is interposed between loop 32 and ground plate 29. It will be understood that this effectively lowers the characteristic impedance of the coupling element in accordance with the dielectric constant of sheet 30. Consequently, the use of a dielectric sheet interposed between the coupling loop andthe ground plate allows further latitude in the design of the coupling element in order to obtain a match to transmission line 8.

In the system shown in Figure 4, end 34 of the coupling 32 is turned downwardly through aperture 3l in the insulating member 3D, and is there electrically connected to the ground plate. Consequently, this coupling element may be used for magnetic coupling'in such a system as shown in Figure 2.

An electrostatic coupling element constructed according to the principles of the invention is shown in Figure 5. Such elements differ from those disclosed in Figures 1 through 4 in that the end of the coupling element is not short-circuited and may be capacitatively energized in proximity to a conductor carrying a radio frequency voltage, such as the-unshorted end of one of the transmission line members of resonant section I I shown in Figure, 1.

Employment of the coupling section for electrostatic energization does not affect the dimensions of the device. Consequently, the same may be constructed according to the above stated formulae, as a transmission line, or as a hat conductor operating in relation to an extended ground plane. The embodiment shown in Figure 5 constitutes a transmission line section in al1 respects similarto thatof Figure 1, except that it is open at the end.V As shown in this iigure the coupling elements lcomprises a pair'of at plates, 35 and 3L Plate 35 is grounded as is the lower member of element I8 of Figure 1 for connection with the external member of the concentric line.Y Upper plate 31l is directly connected to the central-.conductor I9 of the line. As in the preceding embodiments, the g physical dimensions of thecoupling element itself will be selected in accordance' with the above noted formulae, and 'match the concentric lines impedance without electrical discontinuity.

While there has been described preferred embodiments of this invention it is obvious to those skilled in the art that various changes and modications can be made therein without departing from the spirit of the invention and the scope of the appended claims.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposes without payment of any royalty thereon or therefor. 1 y

1.l In combination, a low impedance radio frequency transmission line, and a coupling element connected -thereto comprising a pair of opposed laterally extended plate conductors, one of said conductors being formed as a flat loop, the other conductor underlying said loop, said conductors having a characteristic radio'frequency impedance matching that of the line.

2. In combination, a low impedance radio frequency transmission line having solid dielectric interposed between conducting members, and a coupling element connected thereto comprising a pair of opposed laterally extended plate conductors, one of said conductors being formed as a flat loop, the other conductor underlying said loop, said conductors having a characteristic radio frequency impedance matching that of the line.

3. In combination, a low impedance radio frequency concentric transmission line, and a coupling element connected thereto comprising a pair of opposed laterally extended plate conductors, one of said conductors being formed as a fiat loop, the other conductor underlying said loop, said conductors having a characteristic radio frequency impedance matching that of thev line.

4. In combination, a low impedance radio frequency transmission line, and an electromag' netic coupling element connected thereto comprising a pair of opposed laterally extended plate conductors forming an electrically closed circuit, one of said conductors being formedv as a iiat loop and the other of said conductors underlying said loop, said conductors having a characteristie radio frequency impedance matching that of the line.

5. In combination, a low impedance radio frequency transmission line, and an electromagnetic coupling element connected thereto comprising a pair of opposed laterally extended plate conductors forming an electrically closed circuit, one of said conductors being formed as a flat loop, and the other of said conductors underlying said loop and areas within and without said loop, said conductors having a characteristic radio frequency impedance matching that of the line.

6. In combination, a low impedance radio frequency transmission line, and an electromagnetic coupling element connected thereto comprising a pair of opposed laterally extended plate conductors forming an electrically closed circuit, one of said conductors being formed as a fiat loop, and the other of said conductors forming a conducting sheet underlying the loop area and extending beyond the same, and a solid dielectric interposed between the two conductors, said conductors having a characteristic radio frequency impedance matching that of the transmission line.

7. In combination, means for generating a high frequency magnetic iield, a low impedance transmission line, and an electromagnetic coupling element connected thereto comprising a pair of opposed laterally extended plate conductors, one of said conductors being formed as a fiat loop, said conductors forming an electrically closed circuit and having a characteristic radio frequency impedance equal to that of the transmission line, said coupling element being positioned within said iield.

-8. In combination, an oscillation generator including a resonant line, a low Aradio frequency impedance coaxial transmission line having inner and outer conductors defining a space of annular cross section therebetween, a solid dielectric filling said space, and a coupling device disposed in magnetically coupled relationship with the resonant line and having an impedance equal to the characteristic radio frequency impedance of the transmission line, the coupling device comprising two fiat conductive plates arranged in closely spaced parallel planes, one conductive y plate being connected to the inner conductor of the coaxial line and the other plate being connected to the outer conductor, the conductive plates being connected together at a point removed from the connection with the transmission line, whereby there is maximum energy transfer to the coaxial transmission line.

9. In combination, a low impedance radio frequency two conductor transmission line having a region between the conductors, a solid dielectric filling said region, capacitative space coupling -means therefor consisting of a first laterally extendedfplate conductor connected to one transmission line conductor, a second laterally extended plate conductor opposed to the first in spaced relationship'and connected to the other transmission line conductor, and insulation means interposed between the plate conductors of a dielectric constant establishing their characteristic radio frequency impedance at a value matching that of the transmission line.

10. .In combination, a low impedance radio frequency two conductor transmission line having a region between the conductors, a solid dielectric iiiling said region, space coupling means therefor consisting of a first laterally extended plate conductor connected to one transmission line conductor, a second laterally extended plate conductor opposed to the first in at least partially spaced relationship and connected to the other transmission line conductor, and insulation means interposed between the plate conductors of a dielectric constant establishing their characteristic radio frequency impedance at a. value matching that of the transmission line.

11. The structure defined in claim 10 further including a resonant circuit positioned in exciting relation to said coupling means.

12. In combination, a low impedance radio frequency two conductor transmission line having a. region between the conductors, a solid dielectric iilling said region, space coupling means therefor consisting of a iirst laterally extended conductor connected to one transmission line conductor, a second laterally extended plate conductor larger than the first extended conductor and affording a ground plane with respect thereto and in at least partially spaced relation therewith, and insulation means interposed between the extended conductors of a dielectric constant establishing their characteristic radio frequency impedance at a value matching that of the transmission line.

W. RODERIC BLISS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Reference Data for Radio Engineers, by Federal Telephone and Radio Corporation, pages S22-328, August 1949, Knickerbocker Printing Corp., N. Y.

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Referenced by
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US2693582 *Mar 11, 1953Nov 2, 1954Collins Radio CoVariable coupling device
US2710946 *Jun 18, 1951Jun 14, 1955IttSupports for microwave transmission lines
US2721309 *Jun 29, 1951Oct 18, 1955IttDirectional couplers for microwave transmission systems
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US2725535 *May 31, 1951Nov 29, 1955IttAttenuators
US2734170 *Jun 22, 1951Feb 7, 1956 Sazanl
US2735073 *Aug 2, 1952Feb 14, 1956InterBandpass
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US2749521 *Mar 5, 1952Jun 5, 1956IttMicrowave coupling arrangements
US2749524 *Apr 1, 1952Jun 5, 1956IttSwitching devices
US2749545 *Aug 1, 1951Jun 5, 1956IttElectromagnetic horn
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Classifications
U.S. Classification333/32, 331/99, 333/246
International ClassificationH03H2/00
Cooperative ClassificationH03H2/006
European ClassificationH03H2/00T1