DE964693C - Microwave directional coupler - Google Patents

Description

ISSUED MAY 29, 1957

W9923 Villa / 2ΐα *

has been named as the inventor

Microwave directional coupler

The invention relates to microwave directional couplers, in particular systems of this type which are used for Transmission of waves with wavelengths of a few millimeters are intended.

It has been known for many years that electromagnetic waves can be transmitted via a transmission medium which consists only of dielectric material, unlike the more well-known Means in which either a conductive jacket surrounds the dielectric material or a conductive one axial core is arranged within the dielectric material. Tests have shown that the Leitang effect is also obtained when using a very thin dielectric rod, whose diameter is only a fraction of a wavelength. With the thin, fully dielectric one A large part of the transmitted wave energy is derived from the dielectric conductor Material is pushed out into the surrounding space so that it does not suffer the losses of the dielectric Material is subject. For this reason, the line attenuation is a thin one fully dielectric conductor very small. Heretofore, however, applications of such conductors have been essentially limited to experimental arrangements where the ladder is perfectly straight

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was held because curvatures of the fully dielectric conductor or slight movements of the same tended to increase the conduction loss by having the desired waveform in Secondary forms of a higher order or the like degenerate and, to a certain extent, as a consequence of this degeneration increased the power loss due to radiation from the conductor.

In practice, rods with a circular cross-section have been used to carry wave energy longitudinally a straight and rigid path. When these rods are made pliable or in a curved path, it is found that a larger substantial amount of the wave energy, those at one end of the curved fully dielectric conductor with a certain plane of polarization is introduced, through the aforementioned degeneration into other forms with an opposite the original polarization different ao angle is lost as the other shapes are not have the polarization selected by the receiving means at the other end of the conductor if these are suitable for the selection of the original polarization. if ag z. B. such a circular conductor is used to collect fundamental wave energy from a transmitter To transmit to a receiver, a noticeable amount of energy appears at the receiver with a polarization that is perpendicular to the polarization that is absorbed by the receiver can be. Such depolarization will cause loss of transmission.

The invention is based on a microwave directional coupler with a pair of strips of uncovered dielectric material and has to the goal, the phenomena associated with the ladder curvature for the Koppkmgswirkune to take advantage of.

The special feature of the invention is that the two strips are made of dielectric material are designed in their cross-section so that a dimension of the strip cross-section is several times the dimension perpendicular to it, and the strips run to each other that they move away from each other from an intermediate area of close proximity in both directions, and that the largest cross-sectional dimension of the strips is small in relation to the wavelength the shortest wave to be transmitted. It has been found that the cross-sectional dimension of the conductor is the phase velocity of a wave polarized parallel to this dimension certainly. Thus, it has a waveform that is parallel to one of the faces of the conductor with rectangular Cross-section is polarized, a phase velocity, which is essentially different from that of other forms. For example the wave is which is polarized parallel to the larger dimension of the cross section, more narrowly limited to the conductor than the wave polarized parallel to the small dimension. The former becomes accordingly have a lower phase velocity and higher attenuation than the latter wave.

So if the desired basic shape with a certain polarity at one end of the conductor is introduced polarized parallel to the small dimension of the conductor, it will be so in the conductor propagate that the plane of polarization always follows a plane of constant phase velocity. There the waves do not tend to couple or in shapes with different phase velocities to degenerate, the tendency to degenerate into forms of other polarities becomes negligible Amount reduced. The polarity of the desired shape remains in relation to the given one The surface of the conductor is preserved even if the conductor is twisted or curved Web is bent.

Further features of the invention are shown in connection with special features shown in the drawing Embodiments explained.

Fig. Ι is a perspective view of an inventive fully dielectric directional coupler, which shows schematically the electrical connections;

FIG. 2 shows a first different embodiment of the directional coupler of FIG. 1;

3 shows a second different embodiment of a directional coupler;

Fig. 4 shows a particular embodiment of a directional coupler according to the invention for electrical go Connection of two fully dielectric waveguides; Fig. 5 is a cutaway perspective View of an adjustable and shielded full dielectric coupler according to a preferred one Embodiment of the invention;

Fig. 6 schematically illustrates a standing wave detector for full dielectric Waveguide systems according to the invention.

Fig. R shows a special embodiment of a directional coupler according to the invention, which is used to couple two fully dielectric conduction paths. The coupler includes a main conduction path which is a straight strip 26 of all-dielectric waveguide and an auxiliary power path which is a slightly curved portion of a strip 27, preferably of the same material, and which is bent to be close to part of the Strip or conductor 26 is. The conductors 26 and 27 should preferably have equal propagation speeds for the electromagnetic wave energy of each frequency. This can be achieved if the conductors are made of material with the same dielectric constant and have the same cross-section. As shown, the narrow surfaces of both strips 26 and 27 lie in the same plane while the transverse dimensions of the wider surfaces are parallel.

The conductors 26 and 27 can be held in this position relative to one another in many ways. Fig. Ι shows in particular a novel means for this, which consists of a block 28 made of a material which has low losses and a low dielectric constant which is essentially close to that of air and therefore significantly different from that of the material

Conductors 26 and 27 is. The block 28 has a straight slot 29 into which the conductor 26 is pressed is, further a curved slot 30 into which the conductor 27 is pressed. A suitable fabric for the block 28 is polystyrene foam material. Over the slotted surface of the block 28 can a disk 31 made of the same material can be suitably attached. The front and rear ends Both the main and the auxiliary power path can be connected to associated metallic by means of horns Waveguide systems are coupled. The device according to FIG. 1 can then perform the functions exercise, for which the usual directional couplers were used in the past. Such connections are shown in FIG. 1 shown schematically by a signal source 32 which is coupled to the front end of the conductor 26 is, through a payload 34 ,. which is coupled to its rear end, and by adapted loads 33 and 35, which are coupled to the front and rear ends of the conductor 27.

A substantial amount of the wave energy is carried away in the space around each conductor because the cross-sectional dimensions of the conductors 26 and 27 are small compared to the wavelength of the «5 directed energies are chosen. So when the conductors 26 and 27 are moved physically close to one another the fields guided by the conductors act on one another in such a way that they become one bring about electromagnetic coupling between the dielectric paths. The size this coupling is inversely proportional to the distance between the conductors. Hence the result physical proximity of conductors 26 and 27 a distributed increasing and decreasing coupling, which of the maximum coupling in the middle of the coupling area to a small coupling at the Places where the conductors are far apart. It is already known that a distributed increasing and decreasing coupling between two dependent line paths a broadband direction-dependent Coupling results and that the power transmitted between the paths changes periodically like the sine or cosine function of the product of the size of the coupling per length • 45 unit and the route over which the coupling is effective.

Thus, a certain distance between the conductors 26 and 27 is chosen to the size of the Determine coupling, which in turn determines the amount of power transferred between the conductors certainly. When the auxiliary conductor 27 is brought closer to the conductor 26, the electromagnetic Wave energy from the source, represented by 32, of the front clamp of the main line of the coupler, d. H. the left end of the conductor 26, takes on the the rear terminal of the conductor 26 to the load 34 gradually decreases to zero, and at the same time you get most of the power so stung at the rear terminal of the conductor 27 to Transfer to load 35. Substantially no power appears on the front Clamp of conductor 27. Bringing the conductors even closer together causes the performance at the rear terminal of the conductor 26 increases again and the power at the rear Terminal of conductor 27 decreases to zero. This cycle can be repeated a few times before the conductors 26 and 27 touch in the middle. By changing the distance between the Conductors 26 and 27 can therefore achieve any coupling ratio. At a special Embodiment of the invention operating at the frequencies and with the dielectric conductors that have already been specified in detail, it was found that a minimum distance · of half a centimeter between the centers at a curvature of the conductor 27 with a radius of 30.5 cm results in a coupling loss of 3 decibels results, d. H. equal distribution of power to both conductors in the forward direction and a directional effect of over 30 decibels.

Fig. 2 shows another directional coupler according to the invention. The supporting block 36 made of polystyrene foam is provided with two straight grooves 37 and 38 on the opposite surfaces. The axes of the grooves lie in planes which intersect at an acute angle along a line perpendicular to the grooved surfaces of the block 36. The dielectric waveguides 39 and 40, which are identical to the conductors 26 and 27 of FIG. 1 in every respect, are pressed into these grooves. The point of maximum coupling between the conductors is the aforementioned line of intersection, and the degree of coupling is determined by the distance between the conductors 39 and 40 measured along this line. By changing the angle of intersection, the degree of increase and decrease of the distributed coupling and its length can be adjusted.

Both in Fig. 1 and in Fig. 2, the dielectric conductors are coupled in the electrical plane, in other words, it is the wider surfaces of the rectangular full dielectric Conductors arranged in the coupling area so that they adjoin one another.

Fig. 3 shows an embodiment of the invention in which the fully dielectric conductor in the magnetic Level are coupled. Thus, in Fig. 3 there is a straight strip 42 and a slightly curved one Strips 43, which are fully dielectric waveguides, held in a block 44, with the corresponding narrow surfaces are parallel and the wider surfaces of the conductor 43 the plane of the touch wider surfaces of conductor 42. The maximum degree of coupling between the conductors is thus by the distance between the neighboring planes measured parallel to the contact planes determined on narrow surfaces.

An important feature of the directional couplers shown in FIGS. 1, 2 and 3 is the Fact that the exact point on one way or both ways in which the effective electrical Point of Rieh · coupling is obtained, can be changed easily and at will. This peculiarity was missing from the previously known metallic

th transmission lines in which the coupling point is essentially invariable through the position of the slots, holes or openings was determined in adjacent parts of the corresponding Boundaries of the coupled lines cut or otherwise provided was.

In accordance with the invention, preferably either or both are dielectric waveguides ίο of the directional coupler inserted slidingly into the slots of the supporting block. So z. B. in Fig. Ι the block 28 are moved along the path between the source 32 and the load 34, the Conductor 26 slides in slot 29 so that conductor 27, which is carried along by block 28, be coupled to conductor 26 at any point between source 32 and load 34 can. This setting can be made during operation, during one or both conductors lead electromagnetic wave energy. The specific application of this feature will be discussed later shown in connection with FIG. 6.

Each of the directional couplers explained can, if it is aimed at maximum power transmission between the conductors is set as a means of electrically connecting two dielectric conductors Serve at the same phase velocity when it is otherwise difficult to get two pieces of To technically weld dielectric waveguides or to connect them in a suitable manner. In Fig. 4 an embodiment of the invention particularly suitable for this purpose is shown, which is similar in many respects to the embodiment of FIG. 1, except that the dependent fully dielectric waveguides 46 and 47 both slightly curved and through slots in the load-bearing Block 48 are held in such a way that the axis of the output end 49 of the conductor 47 is on is the axis of the input end 50 of the conductor 46. So if the distance between the conductors 46 and 47 is set for maximum power transfer, the end 50 will in fact be the end 49 coupled for power transmission in either direction. Ends 51 and 52 of conductors 46 and 47 are, matched by anechoic impedance means 53 and 54, terminated to avoid reflections from Avoid small amounts of benefits that are not coupled.

The directional couplers described are sufficient for many applications; but it is possible that even a small amount of power radiation is present in certain Systems in which the couplers are used, interference or mutual interference caused. In the embodiment according to FIG. 5, such radiation is prevented, while the Ease of coupling for dielectric conductors is preserved. The directional coupler of FIG. 5 consists from a hollow metal assembly 60, which has a chamber with four metal shaft fan ends 61, 62, 63 and 64 forms. The conductors 61 and 62 terminate on opposite walls of the chamber, and theirs Axes are in one line. The conductors 63 and 64 terminate at opposite walls of the chamber and are directed substantially to a common point on the axes of conductors 61 and 62. All four conductors end in a horn. For example, the conductor 61 at the apex may have a pyramid-shaped recess 65, which is worked into the inner wall 66 of the arrangement 60, ends is. Identical horns or recesses 67, 68 and 70

69 are provided for conductors 62, 63 and 64, each horn being symmetrical about the axis of the associated conductor is arranged. These horns are used to introduce the dielectric waves provided within the chamber. A fully dielectric waveguide 70 with tapers 71 on each end goes through chamber 60 with one end into conductor 61 and horn 65 and the other is plugged into conductor 62 and horn 69. A second fully dielectric conductor 72 with the same cross-sectional dimensions as the conductor

70 and with tapers 73 at each end goes through the chamber 60 in a slightly curved arc, the central part of the arc being almost adjacent to the central part of the conductor 70. One end of conductor 72 is inserted into conductor 63 and horn 67 and the other end into conductor 64 and horn 68. As shown in FIG. 5, conductors 70 and 72 are coupled in the electrical plane, similar to the conductors of FIG. 1, but it should be noted that conductors 70 and 72 can also be coupled in the magnetic plane, as in FIG 3. The tapers 71 and 73 at the ends of the dielectric conductors 70 and 72 result in a good match between the dielectric conductors and the metallic conductor pieces 61 and 62 as well as 63 and 64. It is thus possible to cut each end of the dielectric conductor 72 along the metallic wave rider ends 63 or 64 to move without affecting the transmission of wave energy between 10 »the conductors 63 and 72 or between the conductors 64 and 72. As a result, if the dimensions of the chamber 60 are chosen so that the dielectric conductor 72 is approximately the correct distance from the conductor 70, the fine adjustment of that distance and, consequently, the fine adjustment of the coupling factor between the conductors 70 and 72 can easily be done by moving each end of the conductor 72 along its metal waveguide 63 or 64. Such a movement will bring the conductor 72 closer to or further from the conductor 70 and thus change the coupling factor between the conductors 70 and "J2" in order to achieve any desired power transfer from the conductor 72 to the conductor 70 according to the principles already outlined To avoid inside the chamber 60, the inner surfaces thereof are coated with an absorbent material 74, which may, for example, be a coating of carbon, with the exception of part of the inner surfaces in the vicinity of the dielectric conductors 70 and 72, in particular those Bringing horns 65, 6y, 68 and 69 surrounding areas, which are shown as an example by the area surrounding the horns 65 and 67. The area 75 should be so large that

that the resistor material 74 does not have a noticeable portion of the normal on the conductors 70 and 72 absorbs transmitted wave energy.

Fig. 6 schematically illustrates a standing wave detector for fully dielectric waveguide systems by which the over the dielectric conductor 83 from the source 81 to the load 82 Incoming power delivered can be compared to that through load 82 to source 81 reflected power, and thus the degree of impedance matching between the impedance Z of the Load 82 and the wave resistance of the conductor 83 can be determined. A first dielectric Directional coupler 84, which can be one of the arrangements shown in FIGS. 1, 2 or 3, carries out the necessary pick-off functions. With directional coupler 84, conductor 83 is the main line path, which can slide relative to the auxiliary conduit path consisting of the conductor 85. So

ao the conductor 85 can be moved in the longitudinal direction of the conductor 83, as indicated by the arrow 80 is to change the point of electrical coupling between conductors. The distance between the auxiliary conduction path and the main conduction path of the coupler 84 is previously described Way adjusted so that only a small part of the incoming wave power in conductor 83 on the front arm 86 of the coupler 84 and an equally small portion of the reflected wave to serve rear arm 87 is transferred.

The continuations of arms 86 and 87 are called coupled dielectric conductor parts 88 and 89 a second fully dielectric directional coupler 90 brought together. The distance between the Conductors 88 and 89 is selected in the manner previously described so that a directional coupler with a coupling factor of 3 decibels arises, the same part of the power to the two front arms gives. The front arm of the conductor 88 is closed by an adapted load 91. Of the front arm of the conductor 89 is connected to an adapted detector means 92, whose Output is indicated by a meter 93. When operating the standing wave detector -45 of Fig. 6, the tapped portion of the forward wave appears in arm 86 and goes to coupler 90, where it is divided between the load 91 and the detector 92 substantially evenly. The tapped portion of the reverse wave appears in arm 87 and goes to coupler 90, around also to be divided essentially equally between the load 91 and the detector 92. The component of the two waves that occurs at the load 91 is swallowed. Consequently the detector 92 measures a value proportional to the sum of the forward and reverse waves is just as the probe does in the previously known standing wave detector arrangement. if the entire loop arrangement including the conductor 85 along the conductor 83 pushed back and forth changes the amplitudes of the incoming and reflected waves that do not get to detector 92, but their phases change. The result will be that one reads off a series of maxima and minima on the measuring device 93, which are the amplitude maxima and minima of the standing wave on conductor 83 correspond. To the detector for standing To calibrate the waves of Figure 6, the conductor 83 can be provided with a fully reflective finish be e.g. B. with a perpendicular to the dielectric conductor 83 arranged metal plate. The depth of the minima is observed when the conductor 85 is moved relative to the conductor 83. The minimum points are zero if the amplitudes of the incoming and the reflected Wave components in detector 92 are the same. If the minima don't reach zero, either must the coupling factor of the coupler 90 adjusted or an attenuation in one of the conductors 86 and / or 87 are switched on in order to equalize the two components on detector 92. Fig. 6 shows how to make a suitable attenuation in the conductor 86 by means of a strip can turn on a resistive paint 94 z. B. from in a suitable binder suspended carbon particles may exist, and that on the surface of the dielectric conductor 86 installed in order to reduce part of the wave power carried by the field around the conductor "90 swallow.

If you connect the front and rear ends of the conductor 83 through horns to associated metallic Coupled waveguide systems, the device of FIG. 6 for measuring the ratio of the standing wave can be used in these systems. Its usability is therefore not alone limited to systems with fully dielectric waveguides.

Claims (11)

PATENT CLAIMS: 1. Microwave directional coupler with a pair Strips of uncoated dielectric material, characterized in that the Strips are designed in their cross-section so that one dimension of the strip cross-section is a multiple of the perpendicular dimension and in the manner of each other run away from an intermediate area of great approximation in both directions away from each other and that the largest cross-sectional dimension of the strips is small in relation to the wavelength of the shortest wave to be transmitted. 2. Coupling device according to claim 1, characterized in that the strip with unequal cross-sectional dimension has a right-angled or oval profile. 3. Coupling device according to claim 1 or 2, characterized in that each Strip between one end of one waveguide and one end of another waveguide is arranged. 4. Coupling device according to claim 3, characterized in that at least one 709 524/183 the strip slidably protrudes into the interior of the associated waveguide ends. 5. Coupling device according to one of claims ι to 4, characterized in that Align the broadside of the strips to each other and between two parallel planes lie, which run perpendicular to their broad side or to the broad central plane, and that at least one of the strips forms an arc facing the other strip. 6. Coupling device according to one of claims ι to 4, characterized in that the strips in the transverse direction of their broad side or their broad central plane against each other are offset and lie with their broad side between two parallel planes which are perpendicular to its broad side or to the broad central plane, and that at least one of the strips is on either side of the other strip-removing arc. 7. Coupling device according to one of claims ι to 4, characterized in that those lying with their broad side or with their broad central plane in parallel planes Stripes cross each other. 8. Coupling device according to one of claims ι to 7, characterized in that a conductive sheath surrounds the pair of strips and forms a cavity into which the insert both pairs of waveguide ends. 9. Coupling device according to one of claims ι to 7, characterized in that the strips are at least partially and optionally slidably embedded in a block whose material has a dielectric constant that is significantly lower than is the dielectric constant of the strips. 10. Coupling device according to one of the preceding claims, characterized in that that at least one of the strips is flexible. 11. Coupling device according to one of the preceding claims, characterized in that at least one of the strips on a part of its surface is provided with a coating of resistance material. Considered publications:
"Journal of Applied Physics," December 1949, pp. 1188-1192; U.S. Patent No. 2,575,571;
British Patent No. 420 447. 1 sheet of drawings © 609 736/284 12.56 (709 524/183 5. 57)