EP1655800B1 - Planar microwave line with a directional change - Google Patents

Description

The invention relates to a planar microwave line having a dielectric substrate and a planar arrangement of a first microstrip line and at least one further microstrip line, wherein a distance of the first microstrip line and the further microstrip line allows electromagnetic coupling, a first region in which the microwave line a first direction has, a second region in which the microwave line has a second direction, and a transition region in which a change from the first direction to the second direction occurs.

Such a microwave line is from the DE 29 43 502 , which forms the preamble of claim 1, known. This document relates to so-called supported microstrip lines, under which there is understood a composite of two parallel metal surfaces, a parallel to and arranged between these dielectric support and arranged on a first surface of the support first strip-shaped microstrip. After DE 29 43 502 a second microstrip conductor is to be arranged on the surface of the carrier, which runs mainly parallel to the first conductor and can be electromagnetically coupled thereto. In the case of a curve in the line, this document prescribes interrupting the first and second lines through a gap in the direction of a bisector of the deflection angle and cross-connecting the first and second conductors. This is intended to keep the length of the two conductors equal along the curve. The crosswise connection takes place with the aid of a first connection running in the conductor plane and with the aid of a second connection which runs outside the conductor plane and is realized in the form of a conductor wire bridge.

However, it is known that discontinuities in the signal path, such as open ends, vias through the dielectric, impedance jumps, line crossings, or direction changes, for example kinks in the line, create distortions in the electromagnetic fields that distort transmitted signals.

For example, coplanar lines (without accompanying ground layer on the substrate side, the substrate side with the planar microstrip lines opposite), with straight laying very good high-frequency characteristics. In the case of changes in direction, as occur, for example, when laying in circular arcs, unwanted signal distortions and shifts of the electrical ground zero point are shown.

The known microwave line also has discontinuities and the outgoing from the plane in the third dimension extending conductor wire bridge discontinuities and thus undesirable wave resistance jumps.

From the in IEE Proceedings: Microwaves, Antennas and Propagation, Vol. 143, No. 5, October 1996 at pages 447-450 Published article "Coplanar Waveguide Bend with radial compensation" by D. Jaisson is a coplanar line with a bend known in which the propagation of the "slot modes" is prevented by so-called "air bridges" in the straight sections of the waveguide are arranged.

Out Patent Abstracts of Japan, Vol. 2003, No. 12, 5 December 2003 as well as out JP 2003 289206 A a coplanar line is known with a bend having a conductor, wherein on the inner edge of the middle conductor a crenellated phase shifter is provided, wherein the difference in length of adjacent edges but is increased.

From the in IEEE Transactions on Microwave Theory and Techniques, vol. 37, no. 4, April 1989 at pages 748-753 H. Diestel's "A Quasi-TEM Analysis for Curved and Straight Planar Multicon- ductor Systems" is a planar multi-conductor system which has straight and circularly curved sections of coupled transmission lines.

Against this background, the object of the invention is to specify a directional changes having planar microwave line with minimized distortion of transmitted signals.

This object is solved by the features of patent claim 1.

By these features, the object of the invention is achieved. In this case, the invention is based on the fact that both different transit times of signals on mutually coupled microstrip conductors, as well as discontinuities in the line path are avoided. When a microwave line with a first parallel direction in the first direction extending microstrip lines in the two-dimensional transition region to the second direction undergoes a curvature, initially results without countermeasures, a difference between the lengths of the outer microstrip line and the inner microstrip line, since the arc lengths of different radii of curvature are different. This results in different signal propagation times between the two coupled microstrip conductors, which together transmit the propagating signal.

The identical lengths of the coupled microstrip conductors in the transition region according to the invention eliminate the cause of signal distortions resulting from different signal path lengths in the two-dimensional transition region from a first direction to a second direction. In addition, due to the course of the microstrip conductors, which also takes place in a transitional region in a plane and without crossing, discontinuities are avoided.

Because of the elimination of these causes of signal corruption, complex analysis of the branching and the inclusion of compensating reactive elements are not necessary. The invention thus provides a planar microwave line, the good high-frequency properties are largely retained even with a curved installation.

Within the scope of embodiments of the invention, it is preferable for the microwave line to have a second microstrip conductor and a third microstrip conductor as further microstrip conductors.

This configuration results in a coplanar line, which can be known to be used as a cost-effective replacement for a coaxial line. It is a particular advantage of the invention that it can also be used in such coplanar lines. In an application of the subject of the DE 29 43 502 on a coplanar line, on the other hand, there would be an exchange of signal conductor and shielding conductor, which would destroy the shielding functionality of the coplanar line. It is also preferred that the distance of the first microstrip conductor from each further microstrip conductor in the first region and in the second region is constant in each case and in the transition region has a periodic modulation around an average which corresponds to the distance in the first region and / or in the second region.

By this embodiment, in addition to the length equality even a substantial constancy of the dependence of the distance of the microstrip characteristic impedance of the microwave line is achieved. Ideally, sections with greater distance and thus greater characteristic impedance and sections with smaller spacing and thus smaller characteristic impedance compensate each other.

Furthermore, it is preferred that the periodic modulation of the spacing results from a periodic convolution of at least one inner edge having a particular wavelength.

By means of such periodic folding, an inner edge can be lengthened as desired and thus be matched to the length of a further outer edge of an adjacent microstrip conductor having a larger radius of curvature.

It is also preferable that the periodic modulation of the pitch results from convolution of opposite edges of adjacent microstrip lines having different wavelengths.

As a result of this configuration, bulges in the progressions of the edges can be largely approximated to the ideal of a parallel course, so that deviations of the distance between the two edges from an average value are very small.

It is also preferable that a number of convolution periods, that is a number of wavelengths, on an inner edge of the microwave line is equal to a number of convolution periods on each other inner edge of the microwave line.

As a result of this refinement, minimum distance deviations from a mean distance also result for microwave lines with more than two microstrip lines coupled to one another.

Furthermore, it is preferred that the lengths of all edges of all microstrip lines in a transition region are the same. Alternatively it is preferred that at least the lengths of the inner edges are equal, wherein the lengths of the outer edges may be different.

As a result of this refinement, a corruption of transmitted signals caused by propagation delay differences is avoided even in the case of microwave lines with more than two coupled microstrip lines.

It is also preferable that the amplitude of the convolution increases with shorter wavelength.

As a result, there is the advantage that the length of an edge with a smaller radius of curvature and a predetermined number of convolution periods can be adjusted by an enlargement of the convolution amplitude arbitrarily exactly to the length of an adjacent edge with a larger radius of curvature and the same number of convolution periods.

It is also preferred that the shortest wavelength of a convolution of an edge of the microwave line is longer than the wavelength of a highest transmitted over the microwave line useful signal frequency.

In general, interactions such as diffraction phenomena between structures and waves occur when the geometric dimensions of the structures are of the order of magnitude of the wavelength. Because the shortest wavelength of the structure in this embodiment is smaller than the wavelength resulting from the highest (permitted) frequency of the transmitted useful signal, such undesired interactions are avoided.

Further advantages will become apparent from the description and the accompanying figures.

drawings

Fig. 1

schematisch eine Draufsicht einer planaren Mikrowellenleitung auf einem dielektrischen Substrat;

Fig. 2

einen Schnitt durch die Mikrowellenleitung und das Substrat der Fig. 1 gemäss Linie II-II; und

Fig. 3

eine weitere Ausgestaltung einer erfindungsgemäßen Mikrostreifenleitung mit Merkmalen der Erfindung.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it:

Fig. 1

schematically a plan view of a planar microwave line on a dielectric substrate;

Fig. 2

a section through the microwave line and the substrate of Figure 1 along line II-II. and

Fig. 3

a further embodiment of a microstrip line according to the invention with features of the invention.

In detail, FIG. 1 shows a planar microwave line 10 which extends on a dielectric substrate 12 and has a first microstrip line 14 and two further microstrip lines 16 and 18. FIG. 1 thus shows a coplanar line as microwave line 10. The coplanar line is known to correspond to a planar coaxial line. A first distance 20 between the first microstrip conductor 14 and a second microstrip conductor 16 as a further microstrip conductor is dimensioned so that an electromagnetic coupling between the first microstrip conductor 14 and the second microstrip conductor 16 occurs during the transmission of microwaves. Similarly, a second distance 22 between the first microstrip conductor 14 and a third microstrip conductor 18 as a further microstrip conductor is dimensioned such that an electromagnetic coupling between the first microstrip conductor 14 and the third microstrip conductor 18 occurs during the transmission of microwaves.

The first microstrip conductor 14 corresponds to the inner conductor of a coaxial line, and the further microstrip conductors 16 and 18 are to be compared with the outer conductor (shield) of a coaxial line. The width of the first microstrip line 14, the distances 20 and 22, and the dielectric constant of the dielectric substrate 12 essentially determine the characteristic impedance Z of the microwave line 10. Such coplanar microwave line 10 has very good high-frequency characteristics as long as it can be laid. In FIG. 1, the microwave line 10 is laid straight in a first area 24 in a first direction and in a second area 26 in a second direction. The change of direction from the first direction to the second direction and vice versa takes place in a transition region 28 in which the microstrip conductors 14, 16 and 18 of the microwave line 10 are laid in a curved manner. Therefore, edges 30, 32, 34, 36, 38 and 40 of the three microstrip conductors 14, 16 and 18 in the transition region 28 have a curvature.

In this case, the microwave line 10 of Figure 1 has the peculiarity that of the edges 30, 32, 34, 36, 38 and 40 at least adjacent edges 34 and 32 and 36 and 38 of the first microstrip line 14 and the second microstrip line 16 and the first microstrip line 14 and the third microstrip conductor 18 in the transition region 28 have an equal length and extend without crossing. This embodiment of the length of the edges 34, 32 and 36, 38 is based on the recognition that the highest field strengths at the inner edges 32, 34, 36 and 38 of the microstrip conductors 14, 16 and 18 occur during the transport of high-frequency signals via the microwave line 10. Characterized in that the lengths of the edges 34, 32, 36 and 38 are equal to each other, there are no differences in transit time of running along the edges 34, 32, 36 and 38 signals. The same length of the edges 34, 32, 36 and 38 is achieved in the embodiment of Figure 1, characterized in that the distance between the first microstrip line 14 and the second microstrip line 16 and / or between the first microstrip line 14 and the third microstrip line 18 is a periodic Modulation around a mean around. The mean value corresponds to the distance 20 and / or the distance 22 of the microstrip conductors 14 and 16, or 14 and 18 in the first region 24 and / or in the second region 26. The modulation results in an inner edge, e.g. the edge 34, periodically closer to an outer edge, e.g. led the edge 32 and led away from the outer edge. Compared to a purely parallel course of the edges 34 and 32, the inner edge 32 is extended by the periodic approach and removal, which ideally compensates for their shortening by the smaller radius of curvature. The same applies to an extension of the edge 40 to approximate the length of the edge 36. In addition, the length of the edge 36 is adjusted to the length of the edge 34, so that the edges 34, 32, 36 and 38 in the article of Figure 1 the same are. As already mentioned, mean values of distance maxima and distance minima in the transition region 28 should correspond to the associated constant distance in the first region 24 and / or second region 26.

For illustration, FIG. 1 shows distance maxima 42 and distance minima 44, which lie in the transition region 28 and whose average values correspond to the distance 20 from the first region 24. As already mentioned, it can also be provided in one embodiment of the invention that the lengths of all the edges 30, 32, 34, 36, 38 and 40 with each other are equal or the lengths of the edges 32, ..... 40 are aligned with the length of the longest edge 30 due to their radius of curvature. In this case, the alignment can be generated by a sinusoidal folding of the inner edges 32, ...., 40, in which each inner edge 32, ...., 40 carries the same number of waves. As a result, the further down an edge lies, the shorter the wavelength becomes. The fact that the length of each edge corresponds to the length of another edge results from the fact that the amplitude of the convolution increases with shorter wavelength. In other words, the amplitude of the innermost edge 40 is greater than the amplitude of the edge 38, which in turn is greater than the amplitude of the inner edge 36 and so on. 2 shows a section through the dielectric substrate 12 and the microwave line 10 thereon with microstrip lines 18, 14 and 16. FIG. 2 thus shows in particular a section through a coplanar line without accompanying ground on a side 46 of the substrate 12 facing away from the microwave line 10 ,

FIG. 3 shows an alternative planar microwave line 10.1, which has only a first microstrip line 14.1 and a further microstrip line 16.1. Here, too, a first distance 20.1 between the first microstrip conductor 14.1 and the second microstrip conductor 16.1 is dimensioned as a further microstrip conductor such that an electromagnetic coupling between the first microstrip conductor 14.1 and the second microstrip conductor 16.1 occurs during the transmission of microwaves.

The width of the two microstrip conductors 14.1 and 16.1, their distance 20.1 and the dielectric constant of the dielectric substrate 12, which carries the microstrip conductors 14.1, 16.1, essentially determine the characteristic impedance Z of the microwave line 10.1. In FIG. 3, the microwave line 10. 1 is laid straight in a first area 24. 1 in a first direction and in a second area 26. 1 in a second direction. The direction change from the first direction to the second direction and vice versa takes place in a transition region 28.1, in which the microstrip conductors 14.1 and 16.1 of the microwave line 10.1 are laid in a curved manner.

Also in the embodiment of FIG. 3, at least the adjacent edges 34.1 and 32.1 of the first microstrip conductor 14.1 and the second microstrip conductor 16.1 in the transition region 28.1 an equal length in conjunction with a crossing-free course. The same length of the edges 34.1 and 32.1 is also achieved in the embodiment according to FIG. 3 in that the distance between the first microstrip conductor 14.1 and the second microstrip conductor 16.1 has a periodic modulation about an average value. The mean value corresponds to the distance 20.1 of the microstrip conductors 14 and 16.1 in the first region 24.1 and / or in the second region 26.1. Due to the modulation, the edge 34.1 is periodically brought closer to the edge 32.1 and led away from it. Compared to a purely parallel course of the edges 34.1 and 32.1, the edge 34.1 is relatively more extended by the periodic approach and removal, which ideally compensates for their relative shortening relative to the edge 32.1, which is due to the smaller radius of curvature.

In this case, mean values of distance maxima 42.1 and distance minima 44.1 in the transition region 28.1 should correspond to the associated constant distance 20.1 in the first region 24.1 and / or second region 26.1. The periodic modulation thus essentially corresponds to the comparable periodic modulation in FIG. 1, but appears more clearly in the subject matter of FIG. 3.

The approximation of the lengths of the inner edges 34.1, 32.1 can again be generated by a sinusoidal convolution of the inner edges 34.1 32.1, in which each inner edge 34.1, 32.1 carries the same number of waves. In the embodiment of FIG. 3, these are each three half-waves. As a result, the further down an edge lies, the shorter the wavelength becomes. The fact that the length of the edge 32.1 corresponds to the length of the edge 34.1 results from the fact that the amplitude of the convolution increases with shorter wavelength. In other words, the amplitude of the inner edge 34.1 is greater than the amplitude of the edge 32.1. In the embodiment of FIG. 3, the amplitudes differ approximately by a factor of 3. The outer edges 30.1 and 36.1 have their somewhat natural arc length in the embodiment of FIG. 3, ie they have different lengths. This is unproblematic in most cases, because the high-frequency signals propagate along the inner edges 32.1 and 34.1 which couple with one another. It is understood that these modifications also in the coplanar embodiment of FIG. 1 is usable.

It is also understood that the same length of the inner edges 34.1, 32.1 or the edges in Fig. 1 can be achieved not only by a sinusoidal convolution but also by other types of folding. An example of another type of convolution results, for example, from the use of sections of straight lines, parabolic arcs or, more generally, arcs or sections of polynomials.

Claims (9)

1. Planar microwave guide (10) with a dielectric substrate (12) and a coplanar arrangement of a first microstrip conductor (14) and at least one further microstrip conductor (16, 18), in which a spacing (20, 22) of the first microstrip conductor (14) and the further microstrip conductor (16, 18) allows an electromagnetic coupling, a first region (24) in which the microwave guide (10) has a first direction, a second region (26) in which the microwave guide (10) has a second direction and a transition region (28) in which a change from the first direction to the second direction takes place, characterised in that the first microstrip conductor (14) and the further microstrip conductor (16, 18) extend in the transition region free of crossing and adjacent edges (32, 34; 36, 38) of the first microstrip conductor (14) and of the further microstrip conductor (16, 18) have the same length in the transition region (28).
2. Microwave guide (10) according to claim 1, with a second microstrip conductor (16) and a third microstrip conductor (18) as further microstrip conductor (16, 18).
3. Microwave guide (10) according to claim 1 or 2, characterised in that a spacing (20, 22) of the first microstrip conductor (14) from each further microstrip conductor (16, 18) is respectively constant in the first region (24) and the second region (26) and has in the transition region (28) a periodic modulation about a mean value corresponding with the spacing (20, 22) in the first region (24) and/or in the second region (26).
4. Microwave guide (10) according to claim 3, characterised in that periodic modulation of the spacing results as a consequence of a periodic folding, which has a specific wavelength, of an inner edge (32, 34; 36, 38).
5. Microwave guide (10) according to claim 4, characterised in that the periodic modulation of the spacing results by folding opposite edges (32, 34; 36, 38) of adjacent microstrip conductors (14, 16, 18) with different wavelengths.
6. Microwave guide (10) according to claim 4 or 5, characterised in that a number of fold periods on one inner edge (32, 34; 36, 38) of the microstrip conductors (14, 16, 18) is the same as the number of fold periods on each other inner edge (32, 34; 36, 38) of the microstrip conductors (14, 16, 18).
7. Microwave guide (10) according to at least one of claims 3 to 6, characterised in that the lengths of all edges (32, 34, 36, 38, 40) of all microstrip conductors (14, 16, 18) are the same with respect to one another in the transition region (28).
8. Microwave guide (10) according to at least one of claims 4 to 7, characterised in that the amplitude of the folding increases with reducing wavelength of the folding.
9. Microwave guide (10) according to at least one of claims 3 to 8, characterised in that the shortest wavelength of a folding of an edge (32, 34, 36, 38, 40) of the microwave guide (10) is longer than the wavelength of a highest useful signal frequency transmissible by way of the microwave guide (10).

Images