EP2100343B1 - Ferrite filter from iris-coupled finlines - Google Patents

Abstract

A magnetically-tunable filter comprising a filter housing with two tunable resonator spheres made of magnetizable material, which are disposed one above the other in two filter arms. At least one filter arm provides a fin line or slot line disposed on a substrate layer and extending in the direction towards an electrical contact, and a common coupling aperture, thereby connecting the two filter arms to one another. In this context, one resonator sphere is positioned within each filter arm on each of the two sides of the coupling aperture.

Description

In the prior art, tunable band pass filters have resonator elements made of ferrites in which the resonant frequency is set via an external DC magnetic field. The resonators are usually spherical, as this shape can be technically relatively easily in the dimensions required for use at high frequencies (ball diameter ≤ 0.3mm) can be made. One reason to use spherical resonators is the linear relationship between the resonant frequency and the magnitude of the external DC magnetic field.

As material for the resonators YIG (Yittrium Iron Granet) is used at frequencies up to approx. 50GHz. For frequencies above 50 GHz, the use of hexaferrites proves to be advantageous. Due to their crystal structure, hexaferrites have an anisotropy field, which, when appropriately aligned with the external magnetic dc field, enables high resonance frequencies to be set at significantly lower field strengths of the dc field than is the case with YIG. This feature of the Hexaferrite avoids the technically demanding generation of high magnetic field strengths for setting high resonance frequencies in accordance with the prior art.

Shielded (suspended) strip lines are, for example, in fully milled metal channels. These channels are only connected to each other via a circular coupling opening (iris). The state of the art assumes that the lines perpendicular to each other, which due to the orthogonality of the electromagnetic fields leads to a high decoupling out of resonance, the balls are mounted in this structure as in many other coupling structures according to the prior art in the vicinity of a short circuit. The reason for this is that the coupling of the resonators, in particular the resonator balls via the magnetic field (RF field) takes place, which is maximum in the region of the short circuit. Since this maximum occurs independently of the frequency according to the prior art in the short circuit range, a good coupling of the balls is made possible in the resonance case over a wide frequency range.

Furthermore, in the case of resonance, the field energy fed in by the ferrite properties of the balls is radiated in the direction of the diaphragm, as a result of which-unlike outside the resonance case-increased energy transmission between the filter input and the filter output occurs.

A possibility of reducing the insertion loss of the filter under otherwise identical conditions (same line width of the resonance curve of the resonator, same saturation magnetization of the resonator and the same diameter of the iris), according to the prior art in the use of inverse shielded (suspended) strip lines. In this type of conduction, the center conductor is mounted on the side of the substrate facing the resonator or resonator ball, the resonators furthermore being arranged with the associated disadvantages in the short-circuit region.

In the prior art, it is disadvantageous if in the short-circuit region of two metallic strips within of the coupling region, the magnetic field has a considerable component parallel to the transport direction of the coupled-out shaft. This can be excited in the coupling disturbing secondary modes.

The item " Side-Wall Coupled, Strip Transmission-Line Magnetically Tunable Filters Employing Ferrimagnetic YIG Resonators "by P. Carter, published in IEEE Transactions on Microwave Theory and Techiques, Vol. MTT-13, No.3, May 1965 (1965-05 ), Pages 306-315, XP001367185 USA describes a ferrite filter with two or three resonance balls, which are coupled via a slot-shaped opening in a common side wall of the waveguide or housing. The resonator balls are arranged either in the short-circuit region of symmetrical strip lines or waveguides.

In the US 4,888,569 B1 Coupling structures with four resonator balls are listed for the construction of magnetically tunable filters. From this patent, for example, a variable bandpass for frequencies within a frequency range of a maximum of one waveguide band, for example 50-75 GHz emerges. The variable bandpass includes an input waveguide, output waveguide and transition waveguide designed to propagate a TE ₁₀ wave mode. The end of the short-circuited wall input waveguide, the beginning of the output waveguide, which is also provided with a shorting wall and mounted in the direction of externally applied homogeneous magnetic field below the input waveguide and the output waveguide transitional waveguide, is arranged in the operation of the filter between two magnetic poles the variable for the setting of a resonant frequency Apply magnetic field. Input waveguide and output waveguide have in the direction of wave propagation on a rectangular profile, which has a significantly smaller cross-sectional area in the coupling region than at the connecting flange. The coupling region of the variable bandpass comprises the four resonator balls mounted near a shorting wall and each of the tapered end of the input waveguide and output waveguide and the transitional waveguide of constant cross-sectional area.

A disadvantage of in the US 4,888,569 B1 described variable bandpass is that in the case of resonance, the field distribution of the coupled-out wave in the coupling region is unfavorable, since this is guided in a waveguide whose profile decreases perpendicular to the direction of propagation of the output shaft to the coupling region. This leads to unwanted reflections, which overlap destructively and thus reduce the amount of energy transported by the incoming wave. This effect also affects the output in the waveguide expiring wave, which now has a defined frequency, so that total relative to the input of the input waveguide and the output of the output waveguide, the insertion loss is increased because the field distributions in the coupling region are disturbed because of the tapered geometry of the waveguide ,

Another disadvantage is the limited bandwidth of the waveguide concept.

The invention is therefore based on the object to provide a magnetically tunable filter for high frequencies, which in the case of resonance has the lowest possible insertion loss and in the decoupling a very high isolation of the filter input and filter output and the coupling structure does not stimulate disturbing secondary modes.

This object is achieved by the magnetically tunable filter described in claim 1.

Advantageous developments of the filter according to the invention are described in the dependent on claim 1 dependent claims.

The filter according to the invention is integrated in a filter housing with two filter arms and has two tunable and made of magnetizable material resonator balls, which are arranged one above the other in the two filter arms. At least one of the filter arms has a substrate layer which is coated with a fin line or slot line extending in the direction of an electrical connection. Both filter arms are connected by a common coupling opening, wherein in each case a resonator ball is positioned on each side of the coupling opening within the two filter arms.

A particular advantage of using a fin line for the magnetically tunable filter according to the invention results from the only weakly pronounced component of the magnetic RF field (high-frequency field) in the propagation direction of the coupled-out electromagnetic wave (x-direction). The magnetic field in the region of the resonator ball advantageously has only a very weak component in the x direction. Due to these properties of the field distribution of the 210-side mode is only very weakly excited, so that the undesirable side resonance advantageously only significantly weakened appears in the resonance curve.

Furthermore, it is advantageous that both filter arms are arranged one above the other, so that the two resonator balls are no longer positioned side by side but one above the other. This brings further advantages in the integration of the filter according to the invention together with other components in a common housing by itself. So can in a housing with a specific and limited footprint now more components are used around the filter according to the invention, since this advantageously has a smaller lateral extent.

Advantageously, the internal structures, which are defined by a sequence of the different layers, are constructed analogously in the case of both filter arms, which simplifies the production of the filter according to the invention.

A realization of the coupling opening as a single-gap or as a pinhole with any free cross-section is also easy to manufacture.

Advantageously, the coupling opening has a free cross-section whose surface area corresponds at least to the surface area of an equatorial surface of a resonator sphere. This ensures that inhomogeneous field regions (edge effects) are shielded from the walls beyond the coupling opening, so that the coupling mechanism via electron spin resonance can occur only in a homogeneous field region in which the two resonator spheres are located.

In addition, it is advantageous if the metal strips of the fin line are laterally soldered with indium solder.

It is also advantageous if the resonator ball is arranged in each case within the filter arm over an idling region, wherein the no-load area isolates the metal strip of the fin line at their ends from each other and at the same time also forms an insulated area relative to the walls of the filter housing. By such an arrangement is advantageously reduces the component of the RF magnetic field in its amount, which causes disturbing secondary modes in the decoupled electromagnetic wave.

In addition, it is advantageous if a filter arm is composed of two differently sized cuboids, so that the structure of the substrate layer takes place on the smaller cuboid. This ensures a stable attachment of the substrate layer within a filter arm.

Expediently, the layer thickness of the substrate layer can be varied so that the magnetically tunable filter according to the invention can advantageously be used in different frequency bands. The dielectric constant of the material from which the substrate layer is advantageously low.

Advantageously, the metal strip of the fin line on a substrate made of Teflon, since Teflon has the property that it is stable to jam in the filter arm.

The resonator spheres preferably have a diameter of approximately 300 .mu.m, and this size is still easy to handle during their production.

A mirror-image arrangement of the resonator balls on both sides of the coupling opening would also be advantageous since this contributes to reducing the adjustment effort. In particular, it is advantageous if the resonator balls are each glued directly to the substrate layer, so that the expense can be circumvented by attaching a suitable holder, which advantageously in turn facilitates the assembly of the filter according to the invention.

Another advantage of the filter according to the invention is when the resonator balls are arranged in filter arms with different internal structure. Thus, a magnetically tunable filter according to the invention, which consists of a dazzling-coupled microstrip line and a unilateral fin line, has a stretched geometry with a reduced overall height. As a result, the entire filter according to the invention is easier to install in a narrow slot between the pole pieces of an electromagnet. By a small distance between the pole pieces high magnetic field strengths with a reduced effort and thus can be easily generated. Also on the homogeneity of the DC field, a small distance advantageously has a positive effect.

Fig. 1

einen Aufbau von bislang üblichen blendengekoppelten geschirmten (Suspended) Streifenleitungen;

Fig. 2

die Abhängigkeit der Isolation der in Fig. 1 dargestellten Streifenleitungen von der Frequenz;

Fig. 3

einen Resonanzverlauf der in Fig. 1 dargestellten Streifenleitungen in Abhängigkeit von der Frequenz;

Fig. 4

einen Aufbau von bisher üblichen blendengekoppelten geschirmten (Suspended)- Streifenleitungen in inverser Bauart;

Fig. 5

die Abhängigkeit der Isolation der in Fig. 4 dargestellten inversen Streifenleitungen in Abhängigkeit von der Frequenz;

Fig. 6

einen Resonanzverlauf der in Fig. 4 dargestellten Streifenleitungen in Abhängigkeit von der Frequenz;

Fig. 7

eine Verteilung der m_x-Komponente des 210- Wellenmodes im Inneren einer Resonatorkugel;

Fig. 8

eine örtliche Verteilung des magnetischen Feldes einer herkömmlichen inversen geschirmten (Suspended) Streifenleitung im Bereich der Resonatorkugel;

Fig. 9

ein erstes Ausführungsbeispiel eines erfindungsgemäßen magnetisch durchstimmbaren Filters mit einer unilateralen Flossenleitung;

Fig. 10

einen beispielhaften Querschnitt durch eine unilaterale Flossenleitung;

Fig. 11

eine örtliche Verteilung des magnetischen Feldes im Bereich des Kurzschlusses einer unilateralen Flossenleitung als Beispiel für ein besseres Verständnis der vorliegenden Erfindung;

Fig. 12

die Beziehung zwischen einem magnetischen Gleichfeld und einem magnetischen Hochfrequenzfeld bei Anregung der Elektronenspinresonanz als Beispiel für ein besseres Verständnis der vorliegenden Erfindung;

Fig. 13

drei örtliche Verteilungen des magnetischen Feldes im Leerlaufbereich einer unilateralen Flossenleitung des ersten Ausführungsbeispiels des erfindungsgemäßen magnetisch durchstimmbaren Filters bei 50 GHz, 60 GHz und 70 GHz;

Fig. 14

eine örtliche Verteilung des magnetischen Feldes eines zweiten Ausführungsbeispiels des erfindungsgemäßen magnetisch durchstimmbaren Filters mit einer antipodalen Flossenleitung;

Fig. 15

die Abhängigkeit der Isolation des erfindungsgemäßen magnetischen Filters von der Frequenz;

Fig. 16

einen Resonanzverlauf des erfindungsgemäßen magnetischen Filters in Abhängigkeit von der Frequenz;

Fig. 17

einen Aufbau des ersten Ausführungsbeispiels des erfindungsgemäßen magnetischen Filters, wobei eine schlitzförmige Blende zum Einsatz kommt;

Fig. 18

einen Aufbau des zweiten Ausführungsbeispiels des erfindungsgemäßen magnetischen Filters, wobei eine Lochblende Blende zum Einsatz kommt;

Fig. 19

einen beispielhaften Querschnitt durch eine antipodale Flossenleitung wie sie in dem erfindungsgemäßen Filter angewendet wird;

Fig. 20

ein drittes Ausführungsbeispiel eines erfindungsgemäßen magnetisch durchstimmbaren Filters mit einer Mikrostreifenleitung sowie einer unilateralen Flossenleitung unter Verwendung einer Lochblende;

Fig. 21

ein viertes Ausführungsbeispiel eines erfindungsgemäßen magnetisch durchstimmbaren Filters mit einer Mikrostreifenleitung sowie einer unilateralen Flossenleitung unter Verwendung einer schlitzförmigen Blende;

Fig. 22

eine unilaterale Flossenleitung, zur besseren Übersicht ohne Hohlleiter dargestellt, mit einer Aussparung innerhalb der Metallisierung für eine Anwendung in einem erfindungsgemäßen magnetisch durchstimmbaren Filter;

Fig. 23

ein fünftes Ausführungsbeispiel eines erfindungsgemäßen magnetisch durchstimmbaren Filters mit einer unilateralen Flossenleitung unter Verwendung einer schlitzförmigen Blende, welche als doppelter Doppelspalt ausgebildet ist;

Fig. 24

das fünfte Ausführungsbeispiel eines erfindungsgemäßen magnetisch durchstimmbaren Filters mit einer unilateralen Flossenleitung in beiden Filterarmen unter Verwendung einer schlitzförmigen Blende, welche als doppelter Doppelspalt ausgebildet ist aus Fig. 23 in einer Draufsicht;

Fig. 25

eine perspektivische 3D-Darstellung des fünften Ausführungsbeispiels aus Fig. 23 und Fig. 24 mit einer Substratschicht aus Teflon;

Fig. 26

eine perspektivische 3D-Darstellung des Übergangs der Mikrostreifenleitung auf die Flossenleitung bzw. Schlitzleitung des vierten Ausführungsbeispiels des erfindungsgemäßen Filters;

Fig. 27

eine Draufsicht des in Fig. 26 gezeigten Übergangs;

Fig. 28

eine Seitenansicht des in Fig. 26 gezeigten Übergangs und

Fig. 29

eine Ansicht des in Fig. 26 gezeigten Übergangs von der Unterseite aus betrachtet.

Both the structure and operation of the invention, as well as other advantages and objects thereof, will be best understood by reference to the following description taken in conjunction with the accompanying drawings. In the drawing show:

Fig. 1

a structure of previously customary iris-coupled shielded (Suspended) strip lines;

Fig. 2

the dependence of isolation of in Fig. 1 illustrated strip lines of the frequency;

Fig. 3

a resonance course of in Fig. 1 illustrated strip lines as a function of the frequency;

Fig. 4

a structure of previously conventional blind-coupled shielded (Suspended) - strip lines in inverse design;

Fig. 5

the dependence of isolation of in Fig. 4 illustrated inverse strip lines as a function of the frequency;

Fig. 6

a resonance course of in Fig. 4 illustrated strip lines as a function of the frequency;

Fig. 7

a distribution of the m _x component of the 210 wave mode inside a resonator sphere;

Fig. 8

a local distribution of the magnetic field of a conventional inverse shielded (suspended) stripline in the region of the resonator ball;

Fig. 9

a first embodiment of a magnetically tunable filter according to the invention with a unilateral fin line;

Fig. 10

an exemplary cross section through a unilateral fin line;

Fig. 11

a local distribution of the magnetic field in the region of the short circuit of a unilateral Fin line as an example of a better understanding of the present invention;

Fig. 12

the relationship between a DC magnetic field and a high frequency magnetic field upon excitation of electron spin resonance as an example of a better understanding of the present invention;

Fig. 13

three local distributions of the magnetic field in the idle region of a unilateral fin line of the first embodiment of the magnetically tunable filter according to the invention at 50 GHz, 60 GHz and 70 GHz;

Fig. 14

a local distribution of the magnetic field of a second embodiment of the magnetically tunable filter according to the invention with an antipodal fin line;

Fig. 15

the dependence of the isolation of the magnetic filter according to the invention on the frequency;

Fig. 16

a resonance curve of the magnetic filter according to the invention as a function of the frequency;

Fig. 17

a structure of the first embodiment of the magnetic filter according to the invention, wherein a slot-shaped aperture is used;

Fig. 18

a structure of the second embodiment of the magnetic filter according to the invention, wherein a pinhole aperture is used;

Fig. 19

an exemplary cross section through an antipodal fin line as it is applied in the filter according to the invention;

Fig. 20

A third embodiment of a magnetically tunable filter according to the invention with a microstrip line and a unilateral fin line using a pinhole;

Fig. 21

A fourth embodiment of a magnetically tunable filter according to the invention with a microstrip line and a unilateral fin line using a slit-shaped aperture;

Fig. 22

a unilateral fin line, shown for clarity without waveguide, with a recess within the metallization for use in a magnetically tunable filter according to the invention;

Fig. 23

A fifth embodiment of a magnetically tunable filter according to the invention with a unilateral fin line using a slit-shaped aperture, which is formed as a double double slit;

Fig. 24

the fifth embodiment of a magnetically tunable invention Filter with a unilateral fin line in both filter arms using a slit-shaped aperture, which is designed as a double double slit Fig. 23 in a plan view;

Fig. 25

a perspective 3D representation of the fifth embodiment FIGS. 23 and 24 with a substrate layer of Teflon;

Fig. 26

a 3D perspective view of the transition of the microstrip line on the fin line or slot line of the fourth embodiment of the filter according to the invention;

Fig. 27

a top view of the in Fig. 26 shown transition;

Fig. 28

a side view of the in Fig. 26 shown transition and

Fig. 29

a view of the in Fig. 26 shown transition seen from the bottom.

For a better understanding of the magnetically tunable filter according to the invention is first based on the FIGS. 1 to 8 on hitherto conventional in the registration forms and their disadvantages briefly before, with Fig. 9 a first embodiment of the magnetically tunable filter 1 according to the invention will be described in more detail. In the description of the hitherto conventional designs and the embodiments of the present invention identical reference numerals used for functionally identical elements.

Fig. 1 shows a hitherto conventional structure of blind-coupled shielded (suspended) strip lines, wherein a coupling structure consisting of two superposed and separated by a pinhole 13 resonator 3 a, 3 b is used for coupling the connection resonators 23.

The external magnetic DC field H ₀ for tuning the resonance frequency is parallel to the z-axis of in Fig. 1 aligned to seeing coordinate system.

Fig. 2 shows the dependence of the isolation of in Fig. 1 shown strip lines of the frequency of the coupled electromagnetic wave over a frequency range of 50-70 GHz. The shown curve of the isolation is obtained when the magnetic DC field H _{0 is} switched off. At a sufficiently large distance from the main resonance frequency, that is, when the frequency of the incident electromagnetic wave is not near the main resonance frequency, the course of the S-parameter | s ₂₁ | approaches or | s ₁₂ | the course of the isolation curve.

Fig. 3 shows a resonance course of in Fig. 1 shown strip lines as a function of the frequency of the incident electromagnetic wave. Just below a frequency of 61 GHz, the disturbing secondary mode 210 is pronounced.

Fig. 4 shows a hitherto conventional structure of iris-coupled shielded (suspended) Inverse-type stripline. The difference to Fig. 1 is that in the inverse type of stripline both metallizations 10 are each disposed on the opposite surface 16a, 16b of the substrate layer 5.

Fig. 5 shows the dependence of the isolation of in Fig. 4 shown inverse strip lines of the frequency. Due to the concentration of the field energy in the region of the iris (pinhole 13), a smaller decoupling is achieved with the strip lines of inverse design than is the case when using the shielded (suspended) strip lines.

Fig. 6 shows a resonance course of in Fig. 4 Strip lines shown as a function of frequency, the interfering 210 Nebenmode just below a frequency of 61 GHz is more pronounced than in the course of the resonance curve in Fig. 3 , In the resonance course of the Fig. 6 you can see that in the passband a lower insertion loss is achieved. Furthermore, one can clearly see the secondary resonance occurring below the main resonance (210-mode). This unwanted spurious resonance is due to inhomogeneities of the magnetic RF field to conditions. The distribution of the m _x component of the magnetization of 210 modes inside a resonator sphere 3a, 3b is in Fig. 7 shown.

For a better understanding of this secondary mode shows Fig. 7 a distribution of the m _x component of the 210 wave mode inside a resonator ball 3a, 3b. It can be clearly seen that in the respective hemispheres one resulting m _x component prevails, which causes the occurrence of the interfering 210 Nebenmodes.

Fig. 8 shows a spatial distribution of the magnetic field of a conventional inverse (suspended) strip line in the region of the resonator ball 3a, 3b. The excitation of the 210 mode is favored by inhomogeneities of the x component of the magnetic RF field. How to get in Fig. 8 In the case of a (supended) strip line, the x component of the magnetic field is particularly pronounced, which is why a strong excitation of the 210 mode is given. In order to suppress the 210-mode better, a line structure is needed with a very little to no pronounced x-component of the magnetic field. This property is fulfilled by fin leads, which are used according to the invention in a magnetically tunable filter.

Fig. 9 1 shows a first exemplary embodiment of a magnetically tunable filter 1 according to the invention. The filter 1 according to the invention is integrated in a filter housing 2 with two filter arms 4a, 4b and has two tunable and magnetizable material resonator balls 3a, 3b which are arranged one above the other in the two filter arms 4a, 4b are arranged. At least one of the filter arms 4a, 4b has a substrate layer 5 on which a fin line 7 or slot line running in the direction of an electrical connection 6 is provided. Both filter arms 4a, 4b are arranged one above the other in the filter housing 2 and connected by a common coupling opening 8, one resonator ball 3a, 3b being positioned on each side of the coupling opening 8 within the two filter arms 4a, 4b. Both filter arms 4a, 4b have a internal structure, which is defined by a sequence of different layers. The various layers comprise the substrate layer 5 with a metallization layer 10, and an air layer 11 surrounding the other layers. The substrate layer 5 itself has a variable layer thickness 31. In this first exemplary embodiment of the filter 1 according to the invention, the internal structures of both filter arms 4a, 4b are symmetrical to each other. As a line structure, a unilateral fin line 7 is provided.

The substrate layers 5 of the two filter arms 4a, 4b are each located in two milled or eroded metal propagation channels, which are interconnected only by a circular opening or through a pinhole. According to the invention, the pinhole 13 has a free cross-section whose surface area corresponds at least to the area of an equatorial surface of a resonator sphere 3a, 3b. The resonator balls 3a, 3b, which consist of a ferrimagnetic or a ferro-magnetic material, in particular a ferrite, are positioned on opposite sides, mirror images of each other on either side of the coupling aperture 8 and the pinhole within an open-circuit region 17 of the fin lines 7. The coupling of the resonator spheres 3a, 3b over an idling region 17 differs significantly from the conventional concepts in which the resonator spheres 3a, 3b, which have a diameter in the range of 100 μm to 1000 μm, are coupled in the region of a short circuit.

The two filter arms 4a, 4b common coupling opening 8 is also a combination of To realize pinhole 13 with at least one single gap 12.

Fig. 10 shows an exemplary cross section through a classic unilateral fin line 7, wherein the substrate layer 5 is mounted symmetrically to a median plane 21 of a waveguide 25 with a rectangular, also symmetrical cross section. In a unilateral fin line 7, two metal strips 15a, 15b separated by a non-conductive strip 14 are arranged together on a first surface 16a of the substrate layer 5.

In a bilateral fin line 7, which is not shown in the drawing, two separated by a non-conductive strip 14 metal strips 15a, 15b are arranged together on a first surface 16a of the substrate layer 5, wherein at the same time a second surface 16b of the substrate layer 5 at least one metal strip 15c having.

In contrast to this classic unilateral fin line 7, where the substrate layer 5 is preferably mounted in the middle of the surrounding waveguide 25, the substrate layer 5 is arranged in the magnetically tunable filter 1 according to the invention to the aperture or to a coupling opening 8 towards shifted. As a result of this arrangement of the substrate layer 5, the distance between the substrate layer 5 and the coupling opening 8, which in this first exemplary embodiment is designed as a pinhole 13 or as an iris, is reduced in order to ensure a good coupling between the two resonator spheres 3a, 3b in the case of resonance.

The entire propagation channel for the electromagnetic wave to be transported is designed stepped, which means that in each case a filter arm 4a, 4b from a larger cuboid 20a and from a smaller cuboid 20b (see Fig. 23 ), so that the substrate layer 5 with its applied additional layers can be easily mounted on the smaller cuboid 20b. As a result, a stable support of the substrate layer 5 within the waveguide 25 or within the propagation channel is made possible. The fixation of the substrate layer 5 in the propagation channel or in the waveguide 25 can be done for example by a conductive adhesive on the side edges 26 (see Fig. 19 ) is applied at the boundary between the larger cuboid 20a and the smaller cuboid 20b. The conductive connection of the lateral metallizations with the surrounding waveguide 25 according to the invention prevents the propagation of unwanted modes. The magnetic DC field H ₀ , with which the filter 1 according to the invention is tuned, is perpendicular to the substrate layer fifth

As a substrate layer 5, quartz, ceramic, or a similar material is provided, which has a low dielectric constant ε _r . In the substrate layers 5, which consist of the materials mentioned, the line wavelength is greater than when using substrate materials with a high dielectric constant ε _r . The greater conduction wavelength has the advantage that the magnetic field in the interior of the resonator sphere 3a, 3b is more homogeneous and thus the excitation of magnetostatic modes of higher order, which make themselves noticeable as disturbing secondary resonances, is reduced.

Fig. 11 shows a local distribution of the magnetic field in the region of the short circuit of a unilateral fin line 7 as an example for a better understanding of the present invention. The unilateral fin line 7 causes the characteristic of an x-component of the magnetic field to be lower than that of the inverse-type shielded (suspended) strip line, which is described in US Pat Fig. 8 is shown.

The coupling of the resonator spheres 3a, 3b takes place according to the invention over an idling region of the two lateral metal strips 15a, 15b. The idle region isolates both metal strips 15a, 15b at their ends from one another and also from a wall 18 of the filter housing 2. The reasons for this type of coupling will be explained in more detail below. Fig. 11 clearly shows that at the short circuit, the field lines of the magnetic RF field parallel to the external magnetic DC field H ₀ , are. In order to excite the electron spins in the resonator sphere 3a, 3b or the ferrite sphere, which are responsible for the occurrence of the resonance, the magnetic RF field in the area of the sphere must be perpendicular to the external constant field H ₀ , which is shown in FIG Fig. 12 is illustrated.

Fig. 12 shows the relationship between a DC magnetic field H ₀ and a high-frequency magnetic field (RF field) upon excitation of the electron spin resonance as an example for a better understanding of the present invention and in particular for explaining the above-described facts.

Fig. 13 shows three local distributions of the magnetic field in the idle region of the unilateral Fin line 7 of the first embodiment of the magnetically tunable filter 1 according to the invention at the frequencies 50 GHz, 60 GHz and 70 GHz. Due to the formation of an open-circuit region 17, the proportion of the component of the magnetic RF field perpendicular to the magnetic constant field in the region of the resonator spheres 3a, 3b is more pronounced. Therefore, a good excitation of the electron spins and thus a good coupling of the resonator spheres 3a, 3b allows. This ensures the desired field distribution in the region of the resonator spheres 3a, 3b over a wide bandwidth, which is reflected in FIG Fig. 13 is shown. Here it can be seen that the magnetic field component of the RF field, which is perpendicular to the external constant field H ₀ , dominates with increasing distance to the substrate layer 5, so that it is favorable to position the resonator spheres 3 a, 3 b at a sufficiently large distance from the substrate layer 5 , The fixing of the aligned resonator balls 3a, 3b takes place in a holder made of a non-conductive material, which will not be discussed here.

Fig. 14 shows a spatial distribution of the magnetic field of a second embodiment of the magnetically tunable filter according to the invention 1 with an antipodal fin line 7a, it can be seen from this figure that it is convenient to position the resonator balls 3a, 3b along the z-axis, since In this area, the magnetic field has a vanishingly small x-component.

Fig. 15 shows the dependence of the isolation of the magnetic filter according to the invention as a function of the frequency, wherein the attenuation (-75 dB) is better here by a few orders of magnitude than in a hitherto customary Filters, like the isolation curves in Fig. 2 (about -55dB) or in Fig. 5 (about -45dB) show.

Fig. 16 shows a resonance course of the iris-coupled unilateral fin lines 7 as a function of the frequency according to the first embodiment of the magnetically tunable filter 1 according to the invention.

In the resonance course out Fig. 16 In the passband of the filter, a significantly lower insertion loss is achieved than is the case with the shielded (suspended) strip line filter. In addition, results for the unilateral fin lines 7 a better isolation far from the resonant frequency, especially when excited with higher frequencies. In addition, the undesired secondary resonance - despite the same coupling in the case of resonance and higher isolation far from the resonant frequency - in the shielded unilateral fin line filter significantly less pronounced than the (susped) stripline filter inverse design.

The inventive use of a coupling in the idle region 17 and the use of unilateral fin lines 7 a significantly better performance than with the classical coupling structures using a coupling in the short circuit region is achieved. The coupling of the two waveguides 25 and propagation channels takes place according to the first embodiment of the magnetically tunable filter 1 according to the invention via a slot-shaped coupling opening or via a single gap 12. When using slot-shaped coupling openings 12 results in Fig. 17 illustrated coupling structure. Here, too, the coupling of the resonator balls 3a, 3b takes place via an idling region 17 DC magnetic field H ₀ is also perpendicular to the substrate layer. 5

An increase in isolation can be seen in both coupling structures Fig. 9 and Fig. 17 by cascading, ie by suitably connecting in series the same structure or by combining the different coupling structures, which is realized in the third and fourth embodiments of the invention (see Fig. 20 and 21 ).

For both coupling structures off Fig. 9 and Fig. 17 the resonator balls 3a, 3b are coupled to the connecting resonator 23, which is designed to transport a H ₁₁₀ wave mode, either through the width of the slot or the single gap 12 between the lateral metallizations 10 or through the spacing of the resonator balls 3a 3b for the substrate layer 5. For wide gaps 12 results in a stronger coupling of the resonator balls 3a, 3b, since the electromagnetic wave is more out in the air than is the case with narrow columns 12. The adjustment of the coupling between the resonator balls 3a, 3b takes place according to Fig. 9 over the diameter of the pinhole 13 or according to Fig. 17 over the length and the width of the single-gap 12.

Fig. 18 shows a structure of the second embodiment of the magnetic filter 1 according to the invention, wherein also a pinhole 13 is used. The difference from the first exemplary embodiment is that the magnetically tunable filter 1 according to the invention has antipodal fin leads 7a. In contrast to the unilateral fin line 7 are the lateral in the antipodal fin line 7a Metallizations 10 mounted on opposite substrate sides 16a, 16b. The substrate layer 5 is located in two milled or eroded metal propagation channels or waveguides 25, which are interconnected only by a coupling opening 8, which is provided as a circular opening or as a pinhole 13. The coupling opening 8 can also be designed as an ellipse, a rectangle or a triangle. In addition, the coupling opening 8 is at least as a single gap 12 or as a multiple-gap, such as a double or double double slit 29 gestaltbar.

The resonator balls 3a, 3b are positioned on opposite sides of the pinhole 13 in the idling region of the fin line 7 and the fin lines 7, respectively. Also in this coupling structure, the coupling of the resonator balls 3a, 3b via the open-circuit region 17 takes place, since the course of the magnetic field is very similar to the field profile of a unilateral fin line 7. The magnetic field energy is preferably conducted in the substrate layer 5 in the antipodal fin line, which makes the difference to an application of a unilateral fin line 7. For this reason, the resonator spheres 3a, 3b are applied or glued directly to the substrate layer 5, for which reason ball retainers are not required in this structure. For exact positioning of the resonator spheres 3a, 3b on the substrate layer 5, circular contours 24 were provided in the lateral metallizations.

In contrast to the classical antipodal fin line 7a, in which the substrate layer 5 is mounted in the middle of the surrounding waveguide 25, the substrate layer 5 to the coupling opening 8 is out arranged so that the substrate layer 5 in the filter arms 4a, 4b is respectively arranged asymmetrically with respect to a median plane 21 of the respective filter arm 4a, 4b. Because of this arrangement, the distance between substrate layer 5 and coupling opening 8 is reduced in order to ensure a good coupling between the resonator balls 3a, 3b in the case of resonance.

By concentrating the magnetic field energy in the substrate layer 5, the overall height of the structure of the second embodiment can be further reduced with respect to the first embodiment with the unilateral fin line 7, whereby the magnetically tunable filter 1 according to the second embodiment is easier to fit into a narrow slot between the pole shoes an electromagnet is integrated.

The propagation channel or the waveguide 25 is also stepped in the second embodiment in order to allow a stable support of the substrate layer 5 on one of the smaller cuboid 20b of the filter housing 2. The fixation of the substrate layer 5 in the propagation channel or in the waveguide 25 is realized for example by a conductive adhesive, which is applied to the side edges 26 at the boundary between the smaller cuboid 20b and a larger cuboid 20a. Furthermore, soldering with indium solder ensures a conductive connection of the lateral metallizations 10 with the propagation channel surrounding them, so that the propagation of undesirable modes is prevented. The magnetic DC field H ₀ is also perpendicular to the substrate layer fifth

Even with the use of an antipodal fin line 7a in a magnetically tunable filter 1 according to the invention, a coupling of the resonator balls 3a, 3b via a slot-shaped coupling opening 8 or aperture is possible according to the second embodiment, in this case have in the construction Fig. 17 only the substrate layers 5 with the unilateral line structure are replaced by substrate layers 5 with antipodal line structure 7a.

An increase in the isolation is also possible by suitable cascading of the coupling structures. The coupling structures from the Fig. 9 and Fig. 17 can also be built by using bilateral fin lines. The coupling of the resonator balls 3a, 3b also takes place in the bilateral fin lines via an open-circuit region 17. However, this embodiment is not shown in the drawing.

Fig. 19 shows an exemplary cross section through an antipodal fin line 7a, wherein two separated by the non-conductive substrate layer 5 metal strips 15a, 15b or metallizations 10 are arranged symmetrically on opposite surfaces 16a, 16b of the substrate layer 5.

Fig. 20 shows a third embodiment of a magnetically tunable filter 1 according to the invention with a microstrip line 22 and a unilateral fin line 7 using a pinhole 13 as a coupling opening 8 between the two filter arms 4a, 4b. The waveguides are located in two metal milled or eroded propagation channels, the only connected via a coupling opening 8 according to the invention in the. The resonator balls 3a, 3b are positioned on opposite sides of the coupling opening 8 in the idling region 17 of the fin line 7 or in the short-circuit region of the microstrip line 22. Since the field line images of a unilateral fin line 7 and a microstrip line are orthogonal, when using the iris-shaped coupling opening 8 (pinhole 13) for the third embodiment of the filter 1 according to the invention a stretched structure 28 results.

Since the two resonator spheres 3a, 3b are subjected to different boundary conditions with respect to the course of the magnetic field, one possibility for rotating at least one of the two resonator spheres 3a, 3b is provided. Different boundary conditions in the field profile lead to offset resonance frequencies of the individual resonator balls 3a, 3b, whereby the insertion loss in the passband of the relevant filter is increased. Through targeted rotations of the resonator spheres 3a, 3b, it is possible to adjust the position of the resonant frequency of the individual resonator spheres 3a, 3b within a certain frequency range.

Fig. 21 shows a fourth embodiment of a magnetically tunable filter 1 according to the invention with a microstrip line 22 and a unilateral fin line 7 using a slot-shaped aperture 12 as a coupling opening 8. In this embodiment, the resonator balls 3a, 3b are arranged one above the other in two filter arms 4a, 4b with different internal structure ,

Instead of the microstrip line 22, the use of a coplanar line with or without ground is provided in further embodiments of the present invention. For additional examples, the fin line 7 in the second filter arm 4b is to be replaced by a (suspended) strip line or by a (suspended) strip line of inverse type. The unilateral fin line 7 can also be replaced by an antipodal fin line 7a or a bilateral fin line. The increase in isolation is, as already mentioned, possible by cascading with the same or another coupling structure. In the coupling structures Fig. 9 . Fig. 17 . Fig. 18 . Fig. 20 and Fig. 21 is the coupling opening 8 to realize by polygons with arbitrary shape.

Fig. 22 shows a unilateral fin line 7 without a surrounding waveguide 25. The unilateral fin line 7 has a recess 24 which is provided within the metallization 10. This structure is also intended for use in a magnetically tunable filter 1 according to the invention.

Fig. 23 shows a fifth embodiment of a magnetically tunable filter 1 according to the invention, each with a unilateral fin line 7 in two filter arms 4a, 4b, being provided as a coupling opening 8 between the two filter arms 4a, 4b, a slot-shaped aperture, which is formed as a double double gap 29.

Fig. 24 shows again the fifth embodiment of a magnetically tunable filter 1 according to the invention Fig. 3 in the plan view. This Embodiment has in each filter arm 4a, 4b each have a unilateral fin line 7.

Fig. 25 shows a 3D perspective view of the fifth embodiment FIGS. 23 and 24 , wherein as a substrate layer 5 Teflon is used, which is easy to fix in a waveguide 25 by clamping.

Fig. 26 shows a perspective 3D representation of the transition 30 of the microstrip line 22 on the fin line 7 and slot line of the fourth embodiment of the inventive filter 1. The center conductor 32 of the microstrip line 22 is short-circuited.

Fig. 27 shows a plan view of the in Fig. 26 shown transition 30 and Fig. 28 a side view of the in Fig. 26 shown transition 30, wherein Fig. 29 a view of the in Fig. 26 shown transition 30 from the bottom.

In many areas of high-frequency technology, tunable bandpass filters are needed whose center frequency can be set as desired over a certain frequency range. For the construction of a magnetically tunable bandpass filter according to the present invention, a coupling structure for coupling the resonator balls 3a, 3b is required, which ensures that far away from the resonant frequency there is a high decoupling / isolation between filter input and filter output. At the same time a high energy transfer from the input to the output must be ensured by the coupling structure in the case of resonance. The invention makes it possible at frequencies far Beyond 70GHz up to 110GHz a high isolation and at the same time in case of resonance a high energy transfer can be achieved.

The invention is not limited to the embodiments shown in the drawing, in particular not spherical resonators made of a ferrite.

Claims (32)

1. Magnetically tuneable filter (1) comprising a filter housing (2) with two tunable resonator spheres (3a, 3b) made of magnetisable material, which are arranged one above the other in two filter arms (4a, 4b), wherein the two filter arms (4a, 4b) provide two hollow conductors (25) or metallic propagation channels, which are connected by a common coupling aperture (8), and one resonator sphere (3a, 3b) is positioned on each side of the coupling aperture (8) within each of the two filter arms (4a, 4b),
   characterised in that
   at least one of the filter arms (4a, 4b) contains a substrate layer (5), which provides a fin line (7) or slot line, which is coupled to the resonator sphere (3a, 3b), extending from the resonator sphere (3a, 3b) in the direction towards an electrical connection (6).
2. Magnetically tuneable filter according to claim 1,
   characterised in that
   both filter arms (4a, 4b) provide an internal structure (9), which is defined by a sequence of the substrate layer (5), a metallisation layer (10) and an air layer (11), wherein the metallisation layer is arranged on a first surface and/or on a second surface of the substrate layer.
3. Magnetically tuneable filter according to claim 2,
   characterised in that
   the internal structures (9) of both filter arms (4a, 4b) are symmetrical relative to one another.
4. Magnetically tuneable filter according to any one of claims 1 to 3,
   characterised in that
   the coupling aperture (8) common to the two filter arms (4a, 4b) is formed at least as a single gap (12).
5. Magnetically tuneable filter according to any one of claims 1 to 3,
   characterised in that
   the coupling aperture (8) common to the two filter arms (4a, 4b) is formed as an apertured diaphragm (13).
6. Magnetically tuneable filter according to any one of claims 1 to 5,
   characterised in that
   the coupling aperture (8) is circular, elliptical, rectangular or triangular or provides a polygonal shape.
7. Magnetically tuneable filter according to claim 5,
   characterised in that
   the apertured diaphragm (13) provides an open cross-section, of which the area corresponds at least to the area of an equatorial surface of one of the resonator spheres (3a, 3b).
8. Magnetically tuneable filter according to any one of claims 4 to 7,
   characterised in that
   the coupling aperture (8) common to the two filter arms (4a, 4b) comprises an apertured diaphragm (13) in combination with at least one single gap (12).
9. Magnetically tuneable filter according to any one of claims 1 to 8,
   characterised in that
   the two filter arms (4a, 4b) are arranged one above the other within the filter housing (2).
10. Magnetically tuneable filter according to any one of claims 1 to 9,
    characterised in that
    the fin line (7) is unilateral, wherein two metal strips (15a, 15b) separated by a non-conductive strip (14) are disposed on a first surface (16a) of the substrate layer (5).
11. Magnetically tuneable filter according to any one of claims 1 to 9,
    characterised in that
    the fin line (7) is bilateral, wherein two metal strips (15a, 15b) separated by a non-conductive strip (14) are disposed on a first surface (16a) of the substrate layer (5), and at the same time, a second surface (16b) of the substrate layer (5) provides at least one metal strip (15c).
12. Magnetically tuneable filter according to any one of claims 1 to 9,
    characterised in that
    the fin line (7) is antipodal, wherein two metal strips (15a, 15b) separated by a non-conductive substrate layer (5) are disposed symmetrically relative to one another on mutually-opposing surfaces (16a, 16b) of the substrate layer (5).
13. Magnetically tuneable filter according to any one of claims 10 to 12,
    characterised in that
    the metal strips (15a, 15b) and the filter housing (2) are soldered laterally with solder, in particular, with indium solder.
14. Magnetically tuneable filter according to any one of claims 10 to 13,
    characterised in that
    the resonator sphere (3a, 3b) within each filter arm (4a, 4b) is disposed in the proximity of an open-circuit region (17) of the two lateral metal strips (15a, 15b), wherein the open-circuit region (17) isolates the metal strips (15a, 15b) at their ends both relative to one other and also relative to a wall (18) of the filter housing (2).
15. Magnetically tuneable filter according to claim 2,
    characterised in that
    each filter arm (4a, 4b) is composed respectively of a relatively-larger cuboid (20a) and a relatively-smaller cuboid (20b).
16. Magnetically tuneable filter according to claim 15,
    characterised in that
    the sequence of different layers is implemented on the relatively-smaller cuboid (20b).
17. Magnetically tuneable filter according to any one of claims 1 to 16,
    characterised in that
    the substrate layer (5) in each of the filter arms (4a, 4b) is arranged asymmetrically relative to a central plane (21) of the respective filter arm (4a, 4b).
18. Magnetically tuneable filter according to claim 17,
    characterised in that
    the substrate layer (5) in each of the filter arms (4a, 4b) is displaced parallel to the central plane (21) of the respective filter arm (4a, 4b) in each case in the direction towards the coupling aperture (8).
19. Magnetically tuneable filter according to any one of claims 1 to 18,
    characterised in that
    the substrate layer (5) provides a low relative dielectric constant ε_r.
20. Magnetically tuneable filter according to any one of claims 1 to 19,
    characterised in that
    the substrate layer (5) is made of Teflon.
21. Magnetically tuneable filter according to any one of claims 1 to 20,
    characterised in that
    the resonator spheres (3a, 3b) are made of a ferrimagnetic material or a ferromagnetic material, in particular, a ferrite.
22. Magnetically tuneable filter according to any one of claims 1 to 21,
    characterised in that
    the resonator spheres (3a, 3b) provide a diameter of 100 µm to 1000 µm, preferably approximately 300 µm.
23. Magnetically tuneable filter according to any one of claims 1 to 22,
    characterised in that
    the resonator spheres (3a, 3b) are disposed in mirror-image symmetry relative to one another on both sides of the coupling aperture (8).
24. Magnetically tuneable filter according to any one of claims 1 to 23,
    characterised in that
    the resonator sphere (3a, 3b) in each filter arm (4a, 4b) is fixed by means of a mounting made of a non-conductive material.
25. Magnetically tuneable filter according to any one of claims 1 to 24,
    characterised in that
    the resonator sphere (3a, 3b) in each filter arm (4a, 4b) is glued to the substrate layer (5).
26. Magnetically tuneable filter according to claim 25,
    characterised in that
    a recess (24) is provided in the metal strips (15a, 15b) of the fin line (7), within which the resonator sphere (3a, 3b) is glued directly onto the substrate layer (5).
27. Magnetically tuneable filter according to any one of claims 1 or 2,
    characterised in that
    the resonator spheres (3a, 3b) comprising magnetisable material are disposed one above the other in two filter arms (4a, 4b) with a different internal structure (9).
28. Magnetically tuneable filter according to claim 27,
    characterised in that
    the one filter arm (4a or 4b) contains a microstripline (22), and the other filter arm (4b or 4a) contains a fin line (7).
29. Magnetically tuneable filter according to claim 27,
    characterised in that
    the one filter arm (4a or 4b) contains a microstripline (22), and the second filter arm (4b or 4a) contains a shielded (suspended) stripline.
30. Magnetically tuneable filter according to claim 27,
    characterised in that
    the one filter arm (4a or 4b) contains a microstripline (22), and the other filter arm (4b or 4a) contains an inverse shielded (suspended) stripline.
31. Magnetically tuneable filter according to claim 28,
    characterised in that
    a matching of the surge impedances of the fin line (7) and the microstripline (22) is realised in the terminal region of a connecting resonator (23) of the two filter arms (4a, 4b) by means of a shortcircuited middle conductor (32) of the microstripline (22).
32. Magnetically tuneable filter according to claim 31,
    characterised in that
    the connecting resonator (23) is designed for a transport of an H₁₁₀ wave mode.

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