EP0296007B1 - Whispering-gallery mode microwave resonator - Google Patents

Description

The present invention relates to a dielectric resonator for microwave frequencies: this resonator is of the planar type, that is to say it is in the form of a flat disc, which is either physically distinct from the components with which it cooperates , or integrated into a dielectric plate in which the flat disc is defined by a magnetic wall. This resonator works in "whisper mode", better known by the acronym "whispering-gallery mode".

The mode of whispering was discovered by Lord Rayleigh, in the acoustic field: in a building having a vaulted architecture in a gallery, a noise as low as a whisper is transmitted along the vault, and is easily transmitted at great distance, without loss of energy.

This type of propagation also applies to other fields including that of microwaves, and the theory was studied by Vedrenne and Arnaud, in an article "Whispering-gallery modes of dielectric resonators" published in IEE Proc. flight. 129, N ° 4, pages 183-187 of August 1982.

For a cylinder of dielectric material in which an electromagnetic wave propagates, the resolution of the propagation equation makes it possible to define the longitudinal and transverse components of the modes liable to propagate. These modes are defined by an azimuth number (propagation along the cylinder axis) and a radial number (propagation along a radius of the cylinder). For the modes with high azimuth number, the electric fields E and magnetic H which maintain the wave are confined between a surface known as caustic and the lateral surface of the dielectric cylinder: there is thus a radial confinement.

If we call:
a: the radius of the cylinder,
a _c : the radius of the caustic surface,
R: the radius of a point whose waveform is considered,
for R <a _c : the wave is evanescent,
for a _c <R <a: the wave is oscillating,
for R> a: the wave is evanescent.

In addition, it is known to trap these waves in whisper mode by reducing the diameter of the dielectric cylinder on either side of the record region in which there is a wave confined by whisper mode. Indeed, the external radiation is very weak, since a whisper wave is confined in a disk of thickness 2d for a mode with high azimuth number.

The invention therefore proposes to produce the resonators for microwave devices no longer, as in the known art, by means of a cylinder of dielectric material, the length of which is of the same order of magnitude as the diameter, but by means of a disc of dielectric or metallic material, of small thickness compared to its diameter, operating in whisper mode, the frequency of the whisper wave being related to the radius of the disc, the radius of the caustic surface and the material of the material.

Because the electromagnetic wave is confined, and the external radiation is very weak, a resonator according to the invention operates on any support, whether dielectric or metallic.

Because this resonator in whisper mode is a flat disc, it can either be deposited by screen printing or any other similar process, or engraved in a ceramic plate.

More precisely, the invention consists of a microwave resonator with a resonant element, in gallery whisper mode, characterized in that the resonant element is a flat disc, of diameter much greater than its thickness and the periphery of which is the seat of a propagation of electromagnetic waves whose resonant frequencies are linked to the diameter of the disc, said electromagnetic waves being confined, by the mode of whispering in gallery, between the periphery of the disc and an internal surface called caustic.

• fig. 1 : schéma d'un cylindre en matériau diélectrique, dans lequel une onde électromagnétique est confinée selon le mode de chuchotement, selon l'art connu,
• fig. 2 : représentation, sous forme de rayons optiques, du confinement d'une onde par mode de chuchotement, selon l'art connu,
• fig. 3 : vue de 3/4 dans l'espace d'un résonateur planaire fonctionnant en mode de chuchotement en galerie (WG mode) selon l'invention,
• fig. 4, 5, 6 : différents moyens d'excitation et de couplage à une onde extérieure d'un résonateur planaire en mode de chuchotement selon l'invention,
• fig. 7 : vue en coupe d'un résonateur pseudo-planaire, fonctionnant en mode de chuchotement en galerie, selon l'invention,
• fig. 8, 9 : moyens d'excitation et de couplage à une onde extérieure d'un résonateur pseudo-planaire en mode de chuchotement selon l'invention,
• fig. 10 à 21 : exemples de réalisations de résonateurs planaires ou pseudo-planaires, selon l'invention.

The invention will be better understood from the more detailed description of the operating mode and of several exemplary embodiments, and the advantages detailed during this description which is based on the attached figures, representing:

• fig. 1: diagram of a cylinder made of dielectric material, in which an electromagnetic wave is confined according to the whisper mode, according to known art,
• fig. 2: representation, in the form of optical rays, of the confinement of a wave by whisper mode, according to known art,
• fig. 3: 3/4 view in space of a planar resonator operating in gallery whisper mode (WG mode) according to the invention,
• fig. 4, 5, 6: different means of excitation and coupling to an external wave of a planar resonator in whisper mode according to the invention,
• fig. 7: sectional view of a pseudo-planar resonator, operating in gallery whisper mode, according to the invention,
• fig. 8, 9: means of excitation and coupling to an external wave of a pseudo-planar resonator in whisper mode according to the invention,
• fig. 10 to 21: examples of embodiments of planar or pseudo-planar resonators, according to the invention.

FIG. 1 represents a dielectric cylinder in which an electromagnetic wave is created, by suitable external coupling means. This cylinder 1, of axis z, has a diameter 2a, and, to trap the confined wave according to the mode of whispering, a region of this cylinder, of length 2d, is defined, by reducing in 2 the diameter of the cylinder to l outside said region.

Resonance in gallery whisper mode - better known by the acronym "WG mode" - can be described as a wave which is reflected against the concave wall of a cylinder, at the curved interface between the dielectric medium and the 'ambiant air. The wave moves in the plane of a circle of radius "a", perpendicular to the z axis, and it is confined by the dielectric discontinuity air, but also by a cylindrical surface 3 called caustic, of radius a _c , coaxial with the dielectric cylinder, of radius a> a _c .

FIG. 2 gives, in a plane perpendicular to the z axis, the representation, in the form of an optical ray, of the phenomenon of whisper mode in the gallery. A light ray from A is reflected on the concave surface 1, at B, C, D ..., and thus defines a caustic surface 3 against which it always remains tangent. The process is exactly the same with a microwave electromagnetic wave.

• l'onde est oscillante si a_c < R < a
• l'onde est évanescente si R < a_c ou si R > a

A wave that travels in a medium is governed by a propagation equation, which includes the longitudinal (along the z axis) and transverse (along a radius a) components of the modes likely to propagate. With these components are associated a number of azimuth mode n, a number of radial mode α and a propagation constant h along the axis. To obtain a wave confined by whispering mode, h = 0 and the number n of azimuth mode must be large, and in this case the excitation fields of the electromagnetic wave are confined between a caustic of radius a _c and the lateral surface of the cylinder, of radius a. If we consider a point distant from R from the z axis,

• the wave is oscillating if a _c <R <a
• the wave is evanescent if R <a _c or if R> a

In addition, the axial confinement is improved if, as in FIG. 1, the dielectric cylinder 1 is reduced in diameter in the regions 2 external to the region in which the wave is created in whisper mode. Thus, the field of the resonant mode decreases exponentially in the axial direction z, outside the region of large diameter.

This is shown in FIG. 1 by the two curves 4 and 5 which have been superimposed on the geometric section. Curve 4, which gives the variation of the transverse field, shows that the wave oscillates between a _c and a, and is evanescent inside the caustic of radius a _c and outside the cylinder of radius a. Curve 5, which gives the variation of the axial field, shows that the wave oscillates in the region of length 2d of cylinder 1, and is evanescent outside this region. We therefore have a disc-shaped resonator, in which an electromagnetic wave is confined by whispering mode in the gallery.

In addition, n is called the number of periods along the circle, in radial section, that is to say the number of reflections in B, C, D, E ... in the optical representation of FIG. 2. The frequency of the whisper wave depends on a _c , a, on the nature of the material, therefore on its dielectric constant ε _r , and a little on the length 2d of region 1 of the cylinder.

The fields of whispering gallery modes being confined between the caustic and the outside radius of the cylinder in which there is a wave, they are very weak. This is why the quality factors Q associated with these devices are high, close to the intrinsic quality factors of the material, and limited only by the losses in the material.

In addition, these types of gallery whispering modes allow easy removal of parasitic, axially evanescent modes which are easily absorbed without disturbing the other modes.

Finally, whisper gallery modes can exist in a metal guide.

The object of the invention is to apply the mode of whispering in a gallery, known for cylinders of dielectric materials, to the production of resonators, in microwave electronics in particular. Indeed, while, for very high frequencies, for example 10 to 100 GHz, conventional cylindrical resonators have dimensions so small that they become difficult to handle, the resonators in whisper mode are in the form of a flat disc, very thin, which can be screen printed on a substrate or delimited in a plate of larger dimensions.

FIG. 3 represents a first type of planar resonator in whisper mode according to the invention, seen from 3/4 in space.

It consists of a small disc 7 of isotropic, anisotropic or piezoelectric dielectric material, placed on a substrate 6, which can be insulating or metallic since the resonator does not radiate. The disc 7 has a diameter 2a, defined above, a very small thickness 2d and the material has a permittivity ε _r . The disc 7 can be covered by a metal disc 8 whose usefulness will be detailed later, and it is excited and coupled to the outside by at least one waveguide or a microstrip line 9 and its ground plane 10.

• le diamètre 2a est de l'ordre de 8 à 19 mm, pour des fréquences de l'ordre de 10 à 20 GHz,
• l'épaisseur 2d est de l'ordre de 0,2 à 1,3 mm,
• la permittivité est comprise entre 9 et 36.

By way of nonlimiting examples, for a resonator in gallery whisper mode:

• the diameter 2a is of the order of 8 to 19 mm, for frequencies of the order of 10 to 20 GHz,
• the thickness 2d is of the order of 0.2 to 1.3 mm,
• the permittivity is between 9 and 36.

The resonant frequencies of the whispering modes excited in these resonators are practically independent of the thickness of the disc 7, only the values of the diameter 2a and the permittivity ε _r intervening as shown in Table I in which we also note that the factors Q quality follow an evolution comparable with the frequency and independently of the thickness.

This independence of the resonance frequency with respect to the thickness 2d of the disc can be confirmed by placing the resonator 7 sandwiched between two rings of absorbent materials: the resonance frequencies and the quality factors are the same.

On the other hand, we observe that the quality factor Q increases with the order n of the mode, that is to say with the frequency. Indeed, the radiation decreasing when the frequency increases, the quality factor tends towards the intrinsic value of the quality factor of the material. This is shown in Table II, by comparison with the right part of Table 1.

• modes WGE, possédant un champ électrique E radial,
• modes WGH, possédant un champ électrique E axial, selon la façon dont ils sont excités. On observe que, pour un même résonateur, les facteurs de qualité Q sont plus élevés pour les modes WGE que pour les modes WGH comme le montre le tableau III.

The modes of whispering in the gallery are classified into:

• WGE modes, having a radial electric field E,
• WGH modes, having an axial electric field E, depending on how they are excited. It is observed that, for the same resonator, the quality factors Q are higher for the WGE modes than for the WGH modes as shown in Table III.

Finally, the comparison between Table II and Table IV shows that the resonant frequency decreases when the permittivity ε _r increases.

The excitation and coupling of the whisper modes in the gallery are obtained by synchronizing an external mode with the wave in whisper mode in the resonator disc.

• soit au moyen de lignes microélectroniques: ligne microbande telle que représentée en figure 3, ou ligne à fente.
• soit au moyen d'un guide d'onde métallique muni d'une fente,
• soit au moyen d'un guide image diélectrique dont la permittivité est identique à celle du résonateur planaire en WG mode. La figure 4 donne une représentation du montage réalisé pour mesurer n, F et Q qui sont donnés dans les tableaux I à IV. Le disque résonateur 7 est maintenu à proximité d'un barreau 11 fonctionnant en guide d'onde diélectrique, muni de transitions 12 vers un guide d'onde métallique non représenté.

This coupling can be carried out:

• either by means of microelectronic lines: microstrip line as shown in FIG. 3, or slotted line.
• either by means of a metal waveguide provided with a slot,
• either by means of a dielectric image guide whose permittivity is identical to that of the planar resonator in WG mode. Figure 4 gives a representation of the arrangement made to measure n, F and Q which are given in Tables I to IV. The resonator disc 7 is held near a bar 11 operating as a dielectric waveguide, provided with transitions 12 to a metal waveguide, not shown.

The excitation of the whisper in gallery mode can also be done according to FIGS. 5 and 6. In FIG. 5, a resonator 7, placed flat on a substrate 6, is excited by two microstrip lines 9 oriented along a diameter of the resonator 7 The equivalent in dielectric image guide is given in figure 6.

It has been said previously that a whisper mode resonator can operate on a metal substrate: in this case, it is understood that the microstrip line or lines 9 must be isolated from the substrate which can then serve as a ground plane.

• soit par découpe d'un cylindre diélectrique, si l'épaisseur 2d du disque est suffisante, et de l'ordre de 0,2mm ou davantage,
• soit par sérigraphie d'une pâte diélectrique, sur un substrat céramique, métallique ou résistif, si l'épaisseur est suffisamment faible pour permettre la sérigraphie ( < 0,5 mm). Le dépôt d'une pâte est particulièrement commode, car on peut faire varier, par mélanges, la permittivité de la pâte, et, par les écrans, le diamètre et l'épaisseur du disque de résonateur.

A whisper mode resonator, as defined up to now in the context of the invention, therefore consists of a flat disc in which waves are trapped between a caustic surface and a lateral surface. This disc can be produced:

• either by cutting a dielectric cylinder, if the thickness 2d of the disc is sufficient, and of the order of 0.2 mm or more,
• or by serigraphy of a dielectric paste, on a ceramic, metallic or resistive substrate, if the thickness is small enough to allow serigraphy (<0.5 mm). The deposition of a paste is particularly convenient, because it is possible to vary, by mixing, the permittivity of the paste, and, through the screens, the diameter and the thickness of the resonator disc.

However, the invention also includes a pseudo-planar resonator, operating in whisper mode, the structure of which is easily integrated into hybrid or monolithic circuits.

In a planar resonator, the dielectric-air interface around the periphery of the disk roughly satisfies the boundary conditions of an open circuit. To make a pseudo-planar resonator, it suffices to simulate such an open circuit condition on a dielectric substrate.

A pseudo-planar resonator is shown in section in FIG. 7. Or a dielectric substrate 6, metallized at 10 on a lower face. The pseudo-planar resonator is defined at 12 by a metal ring 13 of width w, deposited on the upper face of the substrate 6. The ring 13 and the metallization 10 simulate a magnetic short circuit 14 in the body of the substrate 6, and this short circuit constitutes an interface equivalent to the side wall of a cylinder. The flat disc of a whisper mode resonator is therefore integrated into a substrate and is defined magnetically.

The gallery whispering modes excited in these resonators are of the same type as those presented above. Table V gives the resonance frequencies and the quality factors for two pseudo-planar resonators.

The resonant frequencies are in good agreement with those of table I for two planar resonators.

It can also be seen that the quality factors are higher when the width w of the metal ring 13 is greater, because that the magnetic short-circuit condition is better respected.

The results obtained were with the same type of excitation as for planar resonators, and Figures 8 and 9 give two examples. In FIG. 8, two microstrip lines 9 on the substrate 6 are coupled along a diameter to a metal ring 13 which defines the resonator 12. In FIG. 9, two dielectric image guides 11, placed on the substrate 6, are coupled along a diameter to a dielectric ring 15, itself placed on a metal ring which defines the resonator 12.

Resonators, planar or pseudo-planar, in gallery whisper mode can be achieved in other ways as well. For example by engraving a flat disc in relief on a main surface of a substrate, comparable to the mesas of semiconductors. Or by etching a circular groove in a substrate, the disc being coplanar with the substrate.

It has been said that the phenomenon of gallery whispering also develops in metals: a resonator in WG mode can be produced by means of a disc or a metal ring, but the substrate is in this case necessarily a dielectric.

Finally, since the modes of whispering are confined between a caustic surface of radius a _c and a surface external to the caustic, of radius a, the space inside the caustic, of radius less than a _c , does not intervene. not, which justifies that a resonator can in certain embodiments be in the form of a ring of material, of thickness 2d. This space can be used to integrate other components, such as semiconductor chips, without altering the properties of the whisper modes. A resonator in WG mode can therefore constitute the encapsulation box of a semiconductor device, this box being formed by a metal cover, which we have seen that it does not disturb the whisper modes since they do not radiate.

• 6 = le substrat de permittivité ε_r
• 10 = le plan de masse
• 9 = au moins une microbande de couplage
• 11 = au moins un guide image diélectrique.

Figures 10 to 21 show several examples of embodiments of resonators in whisper mode in gallery, planar and pseudo-planar. For each figure is given a view in section associated with a plan view. The reference numbers are constant for all these figures and include in particular:

• 6 = the permittivity substrate ε _r
• 10 = the ground plane
• 9 = at least one coupling microstrip
• 11 = at least one dielectric image guide.

• fig. 10 : résonateur planaire,tel que décrit en figure 3 constitué par un disque diélectrique plat 7 rapporté sur un substrat 6,
• fig. 11 : résonateur planaire, constitué par un disque plat 17 taillé en mésa dans un substrat 16, de permittivité différente de celle du substrat 6,
• fig. 12 : résonateur planaire, constitué par un disque plat métallique 18 rapporté sur un substrat diélectrique,
• fig. 13 : résonateur planaire, constitué par un anneau métallique 19 rapporté sur un substrat diélectrique,
• fig. 14 : résonateur pseudo-planaire, défini dans un substrat diélectrique par un anneau métallique 20, très fin, pour simuler la surface extérieure du résonateur et un anneau métallique 21, très fin et concentrique, pour simuler la surface caustique,
• fig. 15 : résonateur pseudo-planaire, défini dans un substrat diélectrique par un anneau métallique 20, très fin, pour simuler la surface extérieure du résonateur, et un trou 22 dans le substrat, de diamètre égal à celui de la caustique,
• fig. 16 : résonateur pseudo-planaire, constitué par un disque 23 découpé dans un substrat diélectrique par une rainure circulaire 24,
• fig. 17 : résonateur pseudo-planaire, défini dans un substrat diélectrique par un anneau métallique 20, très fin, et par une rainure circulaire 25, pratiquée dans la face du substrat qui porte le plan de masse,
• figure 18 : résonateur planaire 17, couplé à un guide image diélectrique 11, les deux étant taillés en mésa dans un substrat diélectrique 16.
• fig. 19 : résonateur planaire constitué par un disque diélectrique 7, couplé à un guide image diélectrique 11 rapportés sur un substrat métallique 26.
• fig. 20 : résonateur constitué par un disque ou anneau 21 métallique, placé dans une ligne triplaque et couplé à une microbande 9,
• fig. 21 : résonateur constitué par un disque diélectrique 7, placé dans un guide d'onde métallique 10, et couplé à une microbande 9 déposée sur un substrat diélectrique 6.

Depending on the case, we have:

• fig. 10: planar resonator, as described in FIG. 3 consisting of a flat dielectric disc 7 attached to a substrate 6,
• fig. 11: planar resonator, constituted by a flat disc 17 cut in mesa in a substrate 16, with a permittivity different from that of the substrate 6,
• fig. 12: planar resonator, consisting of a flat metal disc 18 attached to a dielectric substrate,
• fig. 13: planar resonator, consisting of a metal ring 19 attached to a dielectric substrate,
• fig. 14: pseudo-planar resonator, defined in a dielectric substrate by a very thin metal ring 20, to simulate the external surface of the resonator and a very thin and concentric metal ring 21, to simulate the caustic surface,
• fig. 15: pseudo-planar resonator, defined in a dielectric substrate by a very thin metal ring 20, to simulate the exterior surface of the resonator, and a hole 22 in the substrate, of diameter equal to that of the caustic,
• fig. 16: pseudo-planar resonator, consisting of a disc 23 cut from a dielectric substrate by a circular groove 24,
• fig. 17: pseudo-planar resonator, defined in a dielectric substrate by a very thin metal ring 20, and by a circular groove 25, formed in the face of the substrate which carries the ground plane,
• FIG. 18: planar resonator 17, coupled to a dielectric image guide 11, the two being cut in mesa in a dielectric substrate 16.
• fig. 19: planar resonator constituted by a dielectric disc 7, coupled to a dielectric image guide 11 attached to a metal substrate 26.
• fig. 20: resonator constituted by a metal disc or ring 21, placed in a triplate line and coupled to a microstrip 9,
• fig. 21: resonator constituted by a dielectric disc 7, placed in a metal waveguide 10, and coupled to a microstrip 9 deposited on a dielectric substrate 6.

Other variants are obvious to a person skilled in the art, by combinations between the different substrates and the different forms of resonators and coupling means. Among other things, all the resonators shown can be coupled to two microstrips 9 or two dielectric image guides 11.

These gallery whisper resonators have very interesting properties in the field of millimeter frequencies for the design of hybrid or monolithic circuits, but also in the field of optical frequencies. They have characteristics close to those of the best realizations in non-planar techniques, such as metal cavities.

• pour la stabilisation en fréquence des oscillateurs.
• pour la conception de combineurs de puissance millimétrique.
• pour le filtrage micro-onde passif ou actif.

They are used in microwave electronics, in particular:

• for frequency stabilization of the oscillators.
• for the design of millimeter power combiners.
• for passive or active microwave filtering.

Claims (18)

1. A microwave resonator with a whispering gallery mode resonating element, characterized in that the resonating element is comprised in a flat disk (7) having a diameter (2a) very much greater than that the thickness (2d) thereof, and whose periphery is the site of the propagation of an electromagnetic wave, whose resonant frequencies are linked to the diameter (2a) of the disk (7), the said electromagnetic wave being confined, by the whispering gallery mode around the periphery of the disk (7) and an internal surface. called caustic (3), with a smaller radius (a_c).

2. The resonator as claimed in claim 1, characterized in that the resonant frequencies are independent of the thickness (2d) of the flat disk (7).

3. The resonator as claimed in claim 1, characterized in that the resonant frequencies are predetermined by the mode (n) or the number of reflections of the electromagnetic wave on the periphery of the flat disk (7), said number (n) being itself predetermined by the external excitation of the resonator which is coupled with a strip transmission line (9) or with a dielectric image guide (11).

4. The resonator as claimed in claim 1, characterized in that, the electromagnetic wave being confined by the whispering gallery mode, the resonator (7) does not radiate into the surroundings and in that the substrate, which bears the resonator (7), is manufactured of a dielectric material (6) which is isotropic, anisotropic, piezoelectric, metallic (26) or resistive.

5. The resonator as claimed in claim 1, characterized in that, the electromagnetic wave being confined between the periphery (radius a) of the resonator and the caustic (radius a_c), the resonator is a ring (19) with an outer radius (a) equal to that of the disk (7) and an inner radius (a_c) equal to that of the caustic (3).

6. The resonator as claimed in claim 1, characterized in that, the flat disk of the element is simulated, in its thickness, by a dielectric substrate (6) provided with a ground plane metallized layer (10) by at least one metallic ring (13) which, in combination with the ground plane (10), creates a magnetic short circuit (14) with an inner radius equal to the outer radius (a) of the resonator (12).

7. The resonator as claimed in claim 1, characterized in that it is constituted by a dielectric disk (7) on a dielectric substrate (6) or a metallic substrate (26).

8. The resonator as claimed in claim 1, characterized in that it is constituted by a metallic disk (18) or a ring (19) on a dielectric substrate (6).

9. The resonator as claimed in claim 1, characterized in that it is constituted by a disk (17) cut in accordance with a mesa in a dielectric substrate (16).

10. The resonator as claimed in claim 1, characterized in that it is constituted by two fine concentric metallized layers arranged on a dielectric substrate (6), the outer metallized layer (20) (radius a) simulating in the substrate (6) the periphery of the disk of the resonant element, the inner metallized layer (21) (radius a_c) simulating the caustic.

11. The resonator as claimed in claim 1, characterized in that it is constituted by a fine metallized layer (20) (radius a) arranged on a dielectric substrate (6) and a hole (22) (radius a_c) made in the substrate (16) concentrically to the metallized layer (20), said hole (22) simulating the caustic.

12. The resonator as claimed in claim 1, characterized in that it is constituted by a disk (23) defined in a dielectric substrate (6) by a circular groove (24).

13. The resonator as claimed in claim 1, characterized in that it is constituted by a metallic ring (20) arranged on a first principal surface of a dielectric substrate (6) and by a groove (25) made in a second principal surface of the said substrate, and in alignment with the metallic ring (20).

14. The resonator as claimed in claim 1, characterized in that it is constituted by a flat disk or by a ring (21 ), manufactured of a dielectric or metallic material, arranged in a dielectric substrate (6) which is metallized on its two surfaces (10) and constituting a triple plate line, a strip transmission line (9) being arranged further in the substrate (6) in the plane of the disk (21).

15. The resonator as claimed in claim 1, characterized in that it is constituted by a disk (7) manufactured of a dielectric or metallic material, arranged inside a metallic wave guide, in parallelism with one of its principal surface, a strip transmission line (9) being furthermore arranged on a dielectric substrate (6), on an internal surface of the wave guide.

16. The resonator as claimed in any one of the preceding claims, characterized in that it is coupled with at least one metallic strip transmission line (9) arranged on the substrate (6) in the vicinity of the disk of the resonant element (7).

17. The resonator as claimed in any one of the preceding claims, characterized in that it is coupled with at least one dielectric image guide (11) inserted in the dielectric substrate (16) or arranged on the metallic substrate (26).

18. The resonator as claimed in any one of the preceding claims, characterized in that the dielectric or metallic disk (7) or the ring (19) is produced on the substrate by screen printing.

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