DE1030904B - Microwave transmission line in the manner of a printed circuit with a first strip-shaped conductor, which is arranged at a very small distance with respect to the wavelength and parallel to a second strip-shaped conductor separated by a dielectric layer and of equal or greater width - Google Patents

Description

The invention relates to microwave transmission lines of the printed circuit type, in strip conductor designs. In particular, the invention is directed to the dimensioning of such Lines with the aim of reducing the attenuation values so far as possible.

In the simplest form, such a ribbon or strip line is known to have two flat lines Strips of conductive material on opposite surfaces of a dielectric layer upset. The two conductors are therefore parallel to each other, at a distance from each other, which corresponds to a small fraction of the wavelength of the frequency to be transmitted.

Either both conductors are of the same width, or it is just one of these conductors as a narrow strip formed, while the second conductor is dimensioned much wider or the shape of a conductive Has area.

The invention is now aimed at the optimal dimensioning of these lines for a possible loss-free energy transfer. Apart from the obvious use of low-loss material the invention is based on the idea, taking into account the possibly occurring Waveforms to determine the dimensions of these open to the sides pipe types so that as possible little electromagnetic energy is radiated into the outside space.

A further object of the invention is to provide multiple lines of the printed circuit type indicate, the dimensions of which are also adapted and specially adapted to the frequencies to be transmitted are chosen so that the propagation of undesired waveforms is largely prevented. The invention relates to the width of the arranged in the space between the conductors dielectric layer in relation to the narrow strip conductor, more precisely in relation to the Wavelength of the respective operating frequency. Known Under certain conditions there is also a propagation of electrical waves along dielectric waves Separating layers instead, so that the present task is to prevent such energy propagation in the lateral Direction from the microwave transmission line.

In order to achieve this, it is proposed that the laterally protruding beyond the first strip-shaped conductor Parts of the dielectric or of the second wider conductor are dimensioned so that the Boundary surfaces of the dielectric maximum reflection conditions for in the lateral direction from the actual parallel line emerging waveforms are made. This is z. B. da microwave transmission line

in the manner of a printed circuit

with a first strip-shaped conductor that is in one with respect to the wavelength very small distance parallel to a second one through a dielectric layer

separate strip-shaped conductor

of equal or greater width

is arranged

Applicant:
International

Standard Electric Corporation,
New York, NY (V. St. A.)

Representative: Dipl.-Ing. H. Ciaessen, patent attorney,
Stuttgart-Zuffenhausen, Hellmuth-Hirth-Str. 42

Claimed priority:
V. St. v. America May 8, 1952

Maurice Arditi, Clifton, N.J.,

and Philip Parzen, Forest Hills, N.Y. (V. St. A.),

have been named as inventors

achieved by the fact that in a transmission line in which both conductors have practically the same width, the lateral dimensioning of the dielectric material exceeds this width by a multiple of half the wavelength of the operating frequency l _e. l _e is the wavelength propagating in the dielectric for free waves. In this way, an optimal reflection takes place on the lateral boundary surfaces of the line, since the wave resistance of the surrounding outer space is significantly greater than the wave resistance of the dielectric. This dielectric can therefore be regarded as an open line in the lateral direction.

In a further development of the invention it is proposed that to increase the reflection on the a layer of ferromagnetic material is arranged on the side boundary surfaces of the dielectric, whereby the mismatch between the dielectric and the outside space is significantly increased. Of the

80S 528/342

As is well known, wave resistance for free waves is proportional to the square root of the permeability constant divided by the dielectric constant of the material in question.

Furthermore, it is particularly advantageous to have several lines on a correspondingly widened layer to arrange their conductors parallel to one another in a lateral distance corresponding to half the wavelength lie. As a result, these lines are largely decoupled from one another.

For another embodiment of the microwave transmission line in which the second conductor is much wider than the first strip-shaped conductor, it is accordingly proposed that the

2 shows in section the coupling of such a line to a coaxial line;

3 shows graphically the attenuation values of such a line as a function of the width of the Dielectric;

FIGS. 4 to 10 show a number of exemplary embodiments, the optimal dimensioning of which is based on the invention is possible; in

Fig. 11 and 12 are flat multiple lines geo dimension of the invention shown while

Fig. 13 shows a multi-line cable, the dimensioning of which in the proposed Way done.

In Fig. 1, the basic structure of the dimensioning of the dielectric material is shown the width of the 15 strip or ribbon line with two equally wide narrow conductors by a multiple of the half conductors. The conductors 1 and 2 are overprinted at both wavelengths of the wavelength X _s valid for propagation along dielectric sides of the dielectric 3 by gluing, refreshing, separating layers, or increases by painting on a conductive one. Layer or according to a corresponding etching process

Finally, according to the invention, it is also possible to produce 20. The dielectric, for example polyfor both cable forms, i.e. for a cable with styrene, polyethylene, fiberglass, quartz, consists of a narrow second conductor as well as for a line a low-attenuation material with a low one with a two-dimensional second conductor, the reflection of the dielectric constant. The production of these leiseitlichen To achieve energy propagation thereby, tung, whose, ladder only about a twentieth to that the dielectric layer diverges in the lateral direction 25 only by the fiftieth part of the operating wavelength to x / 4 or odd multiples of this, can be according to each of the technology of the printed value known methods are carried out across the width of the strip-shaped conductor, protrudes and that, for reflection, the lateral

Boundary surfaces of the dielectric with a reflective surface opposite one another Metal layer are provided. In the further spread of electromagnetic fields instead. One lets Formation of this thought, if two different one of these surfaces are developed, then the electrical spreads Options suggested. Either the field can also be along the surface of the dielectric reflective metallic layer made up of two separate. With one attached to a dielectric lateral boundary strips exist, or one finds parallel double lines the directed over can achieve reflection by carrying a similar electromagnetic wave metallic layer on both sides of the dielectric with no field strength components in the propagation cumulative through the outer, at right angles to the direction. At the same time are between these ladders Dielectric bent surface parts of the spreading also other wave forms in the dielectric or longitudinally terten second conductor is shown. In the first case, the outer surfaces of which can also become one side of the on lines with two narrow conductors and thus to a loss of energy

being able to lead. It has been experimentally confirmed that a certain coupling between the actual electromagnetic field of the form of transmission, appropriately referred to as TEM wave, in

is to be laid, which is the same as the wavelength at lengthwise direction of the line and the undesired spread on the surface of the dielectric. Wave forms in the other spatial directions "un-

When using this dimensioning information is to be avoided. An optimal, low-loss transmission is achieved through the undesired waves, as is the energy of electromagnetic energy of a waveform that is propagated in other directions, as can be achieved according to the invention on a minisie on ribbon lines. These waves 50 mum bring about this energy spreading form, which creates a uniform field course of the elec- tric through reflections of the waves. the separating layers as fresh as the magnetic field in each
- has a cutting plane perpendicular to the direction of propagation, represents a special form of the electromagnetic field, which can be described as £ 00 - and with the lateral boundary surfaces equal to zero, its same right also as an ifoo wave. target. It can be assumed that this is in good order in the Anglo-Saxon manner of definition
such wave is referred to as a TEM mode. These
The designation is better insofar as this wave

In fact, no electrical line 5 is coupled in in the direction of propagation and can propagate evenly along the Irish and no magnetic field component on the dielectric 3. Proves, i.e., strictly speaking, neither an E nor an attempt is made to represent the resulting forms of the field-H wave, so that the designation TEM in the distribution is retained for one that follows perpendicular to the propagation. direction practically constant course of the electrical The invention is based on the drawings on 65 and thus also of the magnetic field, so there is a number of corresponding designs in any line cross-section

homogeneous field distribution of the so-called TEM wave. Is in the direction of propagation of this wave as is known, only the Poynting vector, which is perpendicular to both fields, is present, so that

is used, the reference value X _{e is} the wavelength valid for the propagation in the dielectric, while in the second case, which is a line with a wide conductor, l _{s is the} basis

of the dielectric prevented. This means, mathematically in the spatial coordinates given for FIG. 1, that not only H ", but also H ₂ in

An approximation is possible if the microwave energy as shown in FIG. 2 is evenly distributed between the two conductors 1 and 2 of a stripline through a coaxial

examples and further training explained in more detail.

Fig. 1 shows a perspective view of the section of a ribbon or strip line, on the Dimensioning refers to the invention;

5 6

This field shape is similar to that in the spatial element in The invention now ensures that the on a

Far field of a broadcast antenna is, with the sub-such line propagating in the X-direction

decided that the waves on the microwave line are reflected as strongly as possible, so that

carried shaft is laterally limited. Standing waves occur in the area that

between the two conductors 1 and 2, a transmission in this direction cannot be involved. the

Form a series of different waveforms: Reflection, a wave is known to be the larger, the

a) the actual TEM wave with the field composition greater the difference between the wave resistors E _z and H _x ; stands of the individual media, so that a

b) such waves, which in the Z-direction from complete energy transfer actually only with broad; but these fall into the restricted area if io can prevent metal surfaces. By observing only the distance Z between the two conductors smaller than the proposals made with the invention, Z ₀ = 2 _e / ₂ , where X _{e represents} the wavelength of free oscillation, but also the reflection at the interface between connections in the dielectric in question; in the case of the line dielectric and the air, however, it is necessary to bring the maximum value to one of the frequencies in question. Since it is well known that the wave resistance is about twenty to fifteen of each medium in this case differently fifty times smaller, so that this waveform is not one, there is practical significance for the interface between the dielectric and the outside space, an over-adaptation of the dielectric energy transfer own; trikums instead, whose wave resistance is known

c) those waves that are relatively small in the X-direction. That could spread to the side. For these waveforms, the width 20 of the extraordinarily wide dielectric branch line of the stripline Z _{1 is} too small and below it has the character of an open line. Lock value X ₀ = 2 _{e / 2} . On the other hand, the on the other hand, the free-standing part of the dielectric transmission in the F-direction occurs in turn to the actual parallel line, the lower the current losses, the wider one. the over-adapted, so that with a width of 2/2 of the line, so the larger you make X. In the interest of outside space against the low wave resistance of a low attenuation, it is known that the actual line is maximally mismatched. Compromise chosen in such a way that the width of the on the other hand can be made as large as possible from this transformation narrow conductor, but not considering also that a dielectric is made larger than the value 2/4, so a width of only 2 / 4 at the end with an aluminum layer that reflects the fundamental wave of the operating frequency 30 in the same way does not find any transmission conditions. There can be maximum mismatch results. In this case there is between the conductors, 1 and. 2 at most the low wave resistance of the metallic Be harmonics, namely // - waves of the? J-th harmonic boundary layer through a 2/4 transforma.tion see the parallel line transformed with high resistance in the known form. These

35 Properties of the lateral rated values again

_ co s im χ _χ naturally pick up when the

^x ~~ X ₁ dielectric; layer equally spaced,

which correspond to half the wavelength.

form, while £ -waves in the X-direction do not In Fig. 3 the corresponding curves of the

can occur because in the closely adjacent 40 attenuation values of a ribbon line shown, the

Areas between the two conductors 1 and 2 have the characteristics that can be achieved using the invention

E _x -components definitely have the value zero gain in line quality in the various designs

got to. show examples. You can see that the damping

If one applies the same considerations to the smallest fungus for the width «X ₀ = 0, that is, the area of the dielectric outside the two conductors 45 when the dielectric does not extend beyond the line, then there are obviously other conditions. In goes. In addition, minima occur when the width X _{0 of} the F direction can of course be a multiple of the value 2/2. If a TEM wave is excited, but this does not damage the metal plate across the strip-shaped conductor 1 in terms of losses, since this transmission is arranged parallel to the line, this periodic character-desired transmission between the conductors is retained instead of the curve 9, . That would find. In the Z-direction, the free-standing curve 10 can show a strong increase in the standing dielectric also does not excite any wave, damping, especially at point 11, if here too the distances between the separators compared to the invention the width of the free dielectric layers are too small. Waves which take on odd multiples of the value 2/4, the frequencies were known to be between the 55 In FIGS of these layers wiped out. shows even and symmetrical parallel line,

Unlike Hegen, the relationships in the free-standing model represent the special case X ₀ = 0, which is known per se. Part of the dielectric with respect to the X direction. This line shape is according to FIG. 3 for H ₀ = O. The TEM-60 propagating in the main direction Y is relatively low-loss, its properties, who-wave namely has a sinusoidal course in which, as curves 9 and 12 show, practically also this Direction. If one observes this course in achieved with a line, the dielectric of which sees that of the X-direction, one recognizes that the width is λ / 2 . On the other hand, it should be mentioned that waves can propagate in this direction on both sides of the line E _0n - an even narrower strip of the dielectric 3a, since the lateral width of the only part of the space between the dielectric can be seen in this direction as any two conductors 1 and 2, is again considerably large. This is possible because the dielectric causes greater losses because of the increasing this area not closed by the adjacent metal field concentration and because of the lateral energy wave resistance of the free space, which is favored by the surface of the conductor, but by the much higher speaking stray field is. 70 spread.

FIG. 5 shows a line continuation with the dimensioning according to the invention, the attenuation of which corresponds to the first minimum of curve 9 in FIG. Fig. 6 shows a further embodiment with the difference that here the second conductor is significantly widened. This broadening reduces the losses somewhat compared to the line shape shown in FIG. 4 with the same dielectric. 7 shows a line in which the dielectric and the second conductor extend laterally by λ / 2 over the first conductor. Since in this case the waves occurring in the free dielectric are of the type of waves occurring at separating layers, the exact measurement of the value λ / 2 must be based on the wavelength λ _ε as a reference value. The conductor 2a has the same extent as the dielectric 3b. It has been shown that the presence of the dielectric in this form causes particularly great attenuation of the undesired wave propagation. The corresponding line losses of the arrangement according to FIG. 7 are expressed by curve 12 in FIG.

The line shown in FIG. 8 has a dielectric strip approximately half the width of the line shown in FIG. 7, namely with the value Z ₀ == X _sli . A corresponding expansion of the earth conductor 2b, which is denoted by 13, results in a line characteristic which corresponds to that which can be achieved with FIG. 7.

A similar characteristic is also created with the arrangement according to FIG. 9. The conductors 1 and 2 of this arrangement correspond to the previous Figs. 4 and 5, as shown at 14, with the difference that additional layers of conductive material are attached c only at the side edges of the dielectric 3. A very similar conduction effect is also achieved by covering the conduction shown in FIG. 5 with ferromagnetic material 15 on the sides of the dielectric Zb, which results in a high reflection factor. Such a line is shown in FIG. 10, in which ferrite can preferably be used.

The double line according to FIG. 11 is constructed similarly to the form according to FIG. 5, with the difference that the space between the adjacent conductors 1 α and 1 b also has the value 2 _{e / 2} . The side of the dielectric 16 is enlarged by the same amount. The second conductor 2 may la- the, cable ladders and Ib correspond to or instead desse_n the full width of the dielectric 16 are taking, wherein, instead of the reference value X _s then the reference value X _s to contact. Finally, FIG. 12 shows another embodiment in which the second conductor 17 extends over the dielectric 18 and also delimits it on the sides, as shown at 19. The space between the line conductors 1 α and 1 b must again correspond to the value I _{s / 3} , while the width of the dielectric on the sides has the value X _{s / i} .

A further development of the multiple cable according to FIG. 12 is shown in FIG. Two multi-channel strips back to back form a cylindrical cable, in the inner part of which the dielectric 20 is arranged, which carries the conductors 23 and 24 and other conductors at the appropriate intervals. As shown at 22_, 22 α and 22 b, 22 c , the abutting edges are the dielectric. Materials separated from each other by metal. These conductors, which are arranged circularly in the interior along the cylinder axis, can already represent a complete cable, the common conductor layer 21 consisting, for example, of copper braid and being provided with an insulating protective jacket in the usual way. It is advantageous that the individual dielectric strips 20 are separated from one another by arranging the lateral metal strips 22 so that mutual shielding or attenuation of the conductors against crosstalk is achieved.

In the embodiment of Figure 13, the cable is further provided with a second dielectric layer 25 provided, the conductors 27 and 28 and other strip-shaped conductors in a very corresponding manner of microwave transmission lines. The distances are the same, just mutual There is no shielding between the individual conductors. However, the suggested spacing already offers one considerable attenuation against coupling of the conductors.

In any case, a possible energy propagation perpendicular to the direction of propagation of the conductor To avoid security, it is expedient to also include the outer dielectric layer at least between two to interrupt this conductor, as shown at 26. Incidentally, are the main dimensions entered in this figure. Furthermore, the entire multiple cable can still with dielectric or be surrounded by a corresponding envelope. However, it is preferable that a certain air gap remains above the outer conduit conductors, to ensure low losses in every case. Appropriate attempts have been made namely, it has been shown that a considerable amount of energy also spreads on the surfaces of the line conductors.

Claims (10)

Patent claims: 1. Printed circuit-type microwave transmission line having a first strip-shaped conductor that is parallel at a very small distance in terms of wavelength to a second strip-shaped conductor of the same type, separated by a dielectric layer or greater width is arranged, characterized in that the laterally over the first strip-shaped conductor protruding parts of the dielectric or of the second, wider conductor are dimensioned so that maximum reflection conditions at the boundary surfaces of the dielectric for the waveforms emerging from the actual parallel line in a lateral direction are made 2. Transmission line according to claim 1, wherein the second conductor has practically the same width as the first conductor, characterized in that the lateral dimensioning of the dielectric material this width by a multiple of half the wavelength of the operating frequency, preferably that for free waves in the dielectric valid wavelength X _e . 3. Transmission line according to claim 1 or 2, characterized in that to increase the Reflection on the lateral boundary surfaces of the dielectric creates a layer of ferromagnetic !! Material is provided. 4. Transmission line according to one of the preceding claims, characterized in that on a correspondingly widened; dielectric layer several lines are arranged, their Conductors in one half of the wavelength speaking lateral distance are arranged parallel to each other. 5. Transmission line according to claim 1, wherein the second conductor is substantially wider than the first strip-shaped conductor, characterized in that the dimensioning of the dielectric material increases the width of the narrow conductor by a multiple of half the wavelength of the wavelength valid for propagation along dielectric separating layers k exceeds _s. 6. Transmission line according to claim 1, characterized in that the dielectric layer in the lateral direction only by 2/4 or odd multiples of this value across the width of the strip-shaped conductor protrudes and that the lateral boundary surfaces for reflection of the dielectric are provided with a reflective metal layer. 7. Transmission line according to claim 6, characterized in that the reflective metallic layer consists of two separate lateral boundary strips (Fig. 9). 8. Transmission line according to claim 6, characterized in that the reflective metallic layer on both sides of the dielectric through the outer, at right angles around the dielectric curved surface parts of the widened second conductor are shown (Fig. 8). 9. Transmission line according to claim 1, characterized in that the strip-shaped conductors of several separate lines are arranged next to one another _{at a respective distance A s} / _{2 on a correspondingly widened dielectric layer with a second conductor of the same extent (Fig. 12).} 10. Transmission line according to claim 9, characterized in that the dielectric layer carrying a plurality of lines is rolled up in the shape of a cylinder to form a cable and that preferably two such cylindrical layers share a continuous second conductor, the strip-shaped conductors of the first dielectric on the outer circumference and the strip-shaped conductors of the second dielectric are arranged on the inner circumference of the common, conductive cylinder at a distance of 2 _{s / 2} from each other, and that each of the two dielectric layers is at least between two of the strip-shaped conductors running in the axial direction of a continuous metallic separating layer is interrupted (Fig. 13). Considered publications:
Proc. of the IRE, December 1952, p. 1644 ff. 1 sheet of drawings ι 809 528/342 5.