WO2013093976A1

WO2013093976A1 - Tunable resonant elements and filter based on these elements

Info

Publication number: WO2013093976A1
Application number: PCT/JP2011/007195
Authority: WO
Inventors: Taras Kushta
Original assignee: Nec Corporation
Priority date: 2011-12-22
Filing date: 2011-12-22
Publication date: 2013-06-27

Abstract

A filter of the present invention includes a first terminal, a second terminal and a resonant element. The resonant element includes a multilayer substrate, ground vias through the multilayer substrate and a signal via through the multilayer substrate, surrounded by the ground vias and connected to the first and the second terminals. The multilayer substrate further includes a top conductor layer, a bottom conductor layer with at least one aperture, at least one intermediate conductor layer between the top and the bottom conductor layers and a dielectric material which isolates the top, each intermediate and the bottom conductor layers from each other. Each intermediate conductor layer includes a conductive plate connected to the signal via and isolated from the ground vias. The bottom conductor layer is connected to the other end of the signal via. The signal via and an area surrounded by the ground vias in the multilayer substrate act as an artificial dielectric.

Description

TUNABLE RESONANT ELEMENTS AND FILTER BASED ON THESE ELEMENTS

This invention is related to compact resonators tuned mechanically and filters based on these resonators. The structures considered have been formed in multilayer substrates, including printed circuit boards.

Resonators and filters formed using multilayer substrate technologies are widely applied in communication systems due to their cost-effectiveness and high performance. To provide compactness of these structures, an artificial dielectric of a high permittivity can be used as a filling medium of a resonant element serving as a building block of a filter.

Tuning or reconfiguration of functional components in modern and next-generation communication systems is important as a way leading to the reduction of system cost and size. Also, tuning is a necessary step to achieve a desired performance of the components overcoming the fabrication process tolerance effect, particularly.

Japanese Laid Open Patent JP4367660 (US7705695B2) discloses composite via structures and filters based on these structures which are formed in multilayer substrates. Compactness of resonant elements in these structures is provided by conductive plates connected to the signal via forming in such way an artificial dielectric of a high permittivity.

Japanese Laid Open Patent PCT/JP2008/073942 discloses via structures and filters based on these via structures in which an artificial dielectric of a high permittivity is formed by corrugated conductive plates connected to the signal via.

Japanese Laid Open Patent PCT/JP2009/063315 discloses resonant elements and filters based on these elements in which an artificial dielectric is formed by double corrugated surface obtained by the corrugation of both the signal plates and ground plates.

Above-mentioned structures are miniature and cost-effective ones. However it is important to provide tuning for resonant elements and filters.

Japanese Laid Open Patent JP4367660 (US7705695B2) Japanese Laid Open Patent PCT/JP2008/073942 Japanese Laid Open Patent PCT/JP2009/063315

It is an object of the present invention to provide a resonator in a multilayer substrate which is tunable one.

In an aspect of the present invention, such structure is obtained by the design of resonant elements in the vertical direction (perpendicular to multilayer substrate conductor layers). These elements are obtained by a signal via and ground vias which are disposed around the signal via. Compactness of the elements in the vertical direction is provided by a high permittivity artificial dielectric disposed in the area between signal via and ground vias. This artificial dielectric can be obtained by conductive plates connected to the signal vias. Tuning of the resonant elements is made by following method. In the bottom conductor layer of the multilayer substrate, a number of apertures are arranged. The use of floating conductive plates, providing entirely or partially open or closed states of these apertures gives desired frequency response.

It is another object of this invention to provide filters using tunable resonant elements proposed.

Fig. 1A is a top view illustrating the filter in an exemplary embodiment of the present invention. Fig. 1B is a vertical cross-sectional view of the filter shown in Fig. 1A on the 1B-1B section. Fig. 1C is a vertical cross-sectional view of the filter shown in Fig. 1A on the 1C-1C section. Fig. 1D is a bottom view of the filter shown in Fig. 1A. Fig.1E is a vertical cross-sectional view of the filter shown in Figs. 1A to 1D on the 1B-1B section as a physical model of the resonant element. Fig. 2A is a top view of a related art filter. Fig. 2B is a vertical cross-sectional view of the related art filter shown in Fig. 2A on the 2B-2B section. Fig. 2C is a vertical cross-sectional view of the related art filter shown in Fig. 2A on the 2C-2C section. Fig. 2D is a bottom view of the related art filter shown in Fig. 2A. Fig.2E is a vertical cross-sectional view of the related art filter shown in Figs. 2A to 2D on the 2B-2B section as a physical model of the resonant element. Fig.3 is a circuit diagram representing the resonant element used in the filter shown in Figs. 1A to 1D. Fig.4 is a circuit diagram representing the resonant element used in the related art filter shown in Figs. 2A to 2D. Fig. 5A is a top view of a filter of another exemplary embodiment of the present invention. Fig. 5B is a vertical cross-sectional view of the filter shown in Fig. 5A on the 5B-5B section. Fig. 5C is a vertical cross-sectional view of the filter shown in Fig. 5A on the 5C-5C section. Fig. 5D is a bottom view of the filter shown in Fig. 5A. Fig. 6 is a graph showing the effect of the floating plates of the filter for which the resonant elements are presented in Figs. 5A to 5D. Fig. 7A is a top view of a filter of a filter of another exemplary embodiment of the present invention. Fig. 7B is a vertical cross-sectional view of the filter shown in Fig. 7A on the 7B-7B section. Fig. 7C is a vertical cross-sectional view of the filter shown in Fig. 7A on the 7C-7C section. Fig. 7D is a bottom view of the filter shown in Fig. 7A. Fig. 8 is a graph showing an effect of the floating plate of the filter for which the resonant elements are presented in Figs 7A to 7D.

Hereinafter, several types of tunable resonators and compact filters based on these resonators disposed in multilayer substrates according to the present invention will be described in details with reference to attached drawings. But, it would be well understood that this description should not be viewed as narrowing the appended claims.

(An exemplary embodiment)
In Figs. 1A to 1D, an exemplary embodiment of a filter comprising a resonator designed vertically in a multilayer substrate is shown. The multilayer substrate is provided with a plurality of conductor layers 1L1 to 1L6. In each of those six conductor layers 1L1 to 1L6, a ground layer conductor 111 is disposed. Six ground layer conductors 111 are isolated from each other by a dielectric material 105.

Fig. 1A is a top view illustrating the filter in an exemplary embodiment of the present invention. The filter of the present exemplary embodiment includes a signal via 101, a plurality of ground vias 102, a clearance hole 103, a signal via pad 104 and a microstrip line 112.

Fig. 1B is a vertical cross-sectional view of the filter shown in Fig. 1A on the 1B-1B section. The filter of the present exemplary embodiment further includes a dielectric material 105, a plurality of conductive plates 106, a plurality of isolating slits 107, a first pair of

apertures

108 and 108A, a second pair of

apertures

109 and 109A, a third pair of

apertures

110 and 110A and a plurality of ground layer conductors 111.

Fig. 1C is a vertical cross-sectional view of the filter shown in Fig. 1A on the 1C-1C section. Fig. 1D is a bottom view of the filter shown in Fig. 1A.

The plurality of conductor layers 1L1, 1L2, 1L3, 1L4, 1L5 and 1L6 are arranged in this order from top to bottom. The signal via 101 and each of the plurality of the ground vias 102 are disposed through the six conductor layers 1L1 to 1L6. The signal via 101 is surrounded by the plurality of the signal vias 102 which are disposed in a square shape. In this case, the signal via is disposed in a center of the square shape. The signal via pad 104 is disposed in the top conductor layer 1L1 and is connected to the signal via 101. The microstrip line 112 is disposed in the top conductor layer 1L1 and is connected to the signal via pad 104. The clearance hole 103 is disposed in the top conductor layer 1L1 to isolate the signal via pad 104 and the microstrip line 112 from the ground layer conductor 111 of the top conductor layer 1L1.

The plurality of ground layer conductors 111 is disposed in each of the six conductor layers 1L1 to 1L6. The plurality of ground layer conductors 111 are isolated by the dielectric material 105 in one hand and are connected by the plurality of the ground vias 102 in the other hand.

The plurality of conductive plates 106 is disposed in each of the plurality of conductor layers 1L2 to 1L5, except the top conductor layer 1L1 and the bottom conductor layer 1L6. The plurality of conductive plates 106 are isolated from each other by the dielectric material 105, isolated from the plurality of the ground vias 102 by the plurality of isolating slits 107 and connected in common to the signal via 101.

The three pairs of

apertures

108 and 108A, 109 and 109A and 110 and 110A are arranged in the bottom conductor layer 1L6, in parallel to each other. Those

apertures

108, 108A, 109, 109A, 110 and 110A are surrounded by the plurality of ground vias 102. The signal via 101 is between the third pair of

apertures

110 and 110A. The signal via 101 and the third pair of

apertures

110 and 110A are disposed between the second pair of

apertures

109 and 109A. The signal via 101, the third pair of

apertures

110 and 110A and the second pair of

apertures

109 and 109A are disposed between the first pair of

apertures

108 and 108A.

Six-conductor-layer substrate is only an example of multilayer substrates. Number of conductor layers, filling dielectric material and other substrate parameters can be different and are defined by an application.

Fig.1E is a vertical cross-sectional view of the filter shown in Figs. 1A to 1D on the 1B-1B section as a physical model of the resonant element. In present embodiment, a resonant element 1R is formed by the signal via 101 surrounded by ground vias 102. An artificial dielectric 1AD is disposed between the signal via 101 and the plurality of ground vias 102. Here the artificial dielectric 1AD is obtained by the plurality of conductive plates 106 connected to the signal via 101 and separated from ground layer conductors 111 by isolating slits 107.

Consider physical mechanisms which are in the base of the present invention using a model shown in Fig. 1E. The via structure in this figure can be approximated as a coaxial transmission line segment arranged from the top conductor layer 1L1 of the substrate to the bottom conductor layer 1L6. In this coaxial transmission line, the signal via 101 serves as the inner conductor surface, while the plurality of ground vias 102 connected to the conductor layers 1L1 to 1L6 forms the outer conductive boundary.

In a general case, the characteristic impedance of the via structure can be defined as in corresponding coaxial transmission line with smooth and continuous boundaries. The characteristic impedance can be shown by the equation (1a) below:

As for an example, for a round arrangement of ground vias, the function of the above equation (1a) can be shown by the equation (1b) below:

If a square arrangement of the plurality of ground vias 102 is used in the via structure, then the function of the equation (1a) above can be obtained in a form of the equation (1c) below:

The propagation constant for the via structure considered can be defined by the equation (2) below:

Forming the artificial dielectric 1AD in the area between the signal via 101 and the plurality of ground vias 102, one can change the relative permittivity to an effective relative permittivity. In this case, above equations (1a) and (2) can be rewritten as the equations (3a) and (3b) below, respectively:

Also, the length of the resonant elements in the substrate material and artificial dielectric can be respectively defined as the equations (4a) and (4b) below:

As one can see from the above equations (4a) and (4b), developing the artificial dielectric of the effective permittivity higher than the substrate material, the reduction of the length for the resonant element can be obtained.

(Related art)
In Figs.2A to 2D, a filter of an art related to the current invention is presented. Fig. 2A is a top view of a related art filter. Fig. 2B is a vertical cross-sectional view of the related art filter shown in Fig. 2A on the 2B-2B section. Fig. 2C is a vertical cross-sectional view of the related art filter shown in Fig. 2A on the 2C-2C section. Fig. 2D is a bottom view of the related art filter shown in Fig. 2A.

The related art filter shown in Figs. 2A to 2D is composed with same components of the filter of the exemplary embodiment of the present invention shown in Figs. 1A to 1D, except the pairs of

apertures

108 and 108A, 109 and 109A and 110 and 110A. In other words, the related art filter shown in Figs. 2A to 2D can be obtained by closing the pairs of

apertures

108 and 108A, 109 and 109A and 110 and 110A from the filter of the present exemplary embodiment shown in Figs. 1A to 1D.

In this case of the related art shown in Figs. 2A to 2D, the filter includes a resonator designed also vertically in the multilayer substrate including a plurality of conductor layers 2L1 to 2L6. These six conductor layers 211 are isolated by a dielectric material 205.

Fig.2E is a vertical cross-sectional view of the related art filter shown in Figs. 2A to 2D on the 2B-2B section as a physical model of the resonant element. The resonator 2R is formed by the signal via 201 surrounded by the plurality of ground vias 202 with an artificial dielectric 2AD disposed between the signal via 201 and the plurality of ground vias 202. The artificial dielectric 2AD is obtained by conductive plates 206 connected to the signal via 201 and separated from ground conductors by isolating slits 207. Ends of a microstrip line 212 connected to the signal via 201 by means of a pad 204 act as terminals in this filter.

However, in this related art resonator, providing tuning is a bottleneck.

Fig.3 is a circuit diagram representing the resonant element used in the filter shown in Figs. 1A to 1D. The circuit shown in Fig. 3 includes a resistance R, an inductance L and a capacitance C-C_adj(m). In the circuit shown in Fig. 3, the resistance R, the inductance L and the capacitance C-C_adj(m) are connected in series.

Fig.4 is a circuit diagram representing the resonant element used in the related art filter shown in Figs. 2A to 2D. The circuit shown in Fig. 4 can be obtained by substituting the capacitance C-C_adj(m) of the circuit shown in Fig. 3 by a capacitance C.

Using a circuit representation for the resonant element of Fig. 4, the resonance frequency can be written by means of its capacitance and inductance as the following equation (5):

In this invention, to control the frequency response of the resonant element,

apertures

108, 108A, 109, 109A, 110 and 110A in the bottom conductor layer 1L6 (marked as 1AA in Fig. 1E) are proposed to apply. Due to these

apertures

108, 108A, 109, 109A, 110 and 110A, the resonant frequency is changed from the case of the circuit representation shown in Fig. 3 and defined by formula of the equation (6) below:

It should be noted the apertures can be disposed symmetrically with respect to the signal via to provide minimal effect on the electromagnetic field distribution in the resonant element.

In the present exemplary embodiment shown in Figs. 1A to 1D, apertures are grouped by pairs: 108 and 108A; 109 and 109A; 110 and 110A. Components of each pair have the same dimensions and are disposed symmetrically with respect to the signal via conductor 101.

Signaling in the filter is provided by means of a microstrip line 112 connected to a signal via pad 104 which is separated from other conductors by a clearance hole 103. Ends of the microstrip line 112 serve as input and output terminals of this filter.

(Another exemplary embodiment)
In Figs. 5A to 5D, another exemplary embodiment of a tunable filter of the present invention is shown.

Fig. 5A is a top view of a filter of another exemplary embodiment of the present invention. The filter of the present another exemplary embodiment includes a signal via 501, a plurality of ground vias 501, a clearance hole 503, a signal via pad 504 and a microstrip line 512.

Fig. 5B is a vertical cross-sectional view of the filter shown in Fig. 5A on the 5B-5B section. The filter of the present another exemplary embodiment further includes a dielectric material 505, a plurality of conductive plates 506, a plurality of isolating slits 507, a first pair of

apertures

508 and 508A, a second pair of

apertures

509 and 509A, a third pair of

apertures

510 and 510A, a plurality of ground layer conductors 511 and a pair of floating

plates

513 and 513A.

Fig. 5C is a vertical cross-sectional view of the filter shown in Fig. 5A on the 5C-5C section. Fig. 5D is a bottom view of the filter shown in Fig. 5A.

The above components are disposed similarly to the components of the filter shown in Figs. 1A to 1D, except the pair of floating

plates

513 and 513A which are disposed over the bottom conductor layer 5L8 to entirely of partially seal the

apertures

508, 508A, 509, 509A, 510 and 510A.

The filter shown in Figs. 5A to 5D includes a resonant element based on a multilayer substrate including eight ground layer conductors 511 disposed in eight conductor layers 5L1 to 5L8. These conductor layers 5L1 to 5L8 are isolated by a material 505.

In the present another exemplary embodiment, the resonant element, formed by the signal via 501 surrounded by the plurality of ground vias 502, includes an artificial dielectric disposed between the signal via 501 and the plurality of ground vias 502. This artificial dielectric is obtained by the plurality of conductive plates 506 which are connected to the signal via 501 and separated from ground conductors by the plurality of isolating slits 507.

Also, this resonant element includes the plurality of

apertures

508, 508A, 509, 509A, 510 and 510A made in the bottom conductor layer 5L8 in the area between the signal via 501 and the plurality of ground vias 502.

To provide tuning of the resonant element, two floating

plates

513 and 513A are set over the surface of the bottom conductor layer 5L8 to make the state of the plurality of

apertures

508, 508A, 509, 509A, 510 and 510A as entirely or partially open or closed one in dependency on which the center frequency is desired. Also it should be noted that the floating

plates

513 and 513A can be moved by mechanisms 5M and 5MA in a direction parallel to the bottom conductor layer and, as a result, to provide simultaneous entire of partial open or closed states for predetermined pairs of apertures.

If apertures are open, then the total capacitance reduction for the resonant element will be C_adj(m). This magnitude is dependent on summarized opening area of the apertures. In this case the resonant frequency will be shifted to a higher magnitude according to the above equation (6).

It should be noted that moving of the floating

plates

513 and 513A can be made by mechanisms 5M and 5MA providing both their contact to the bottom conductor layer 5L8 and the relocation along the bottom conductor layer 5L8.

The tunable filter is formed by the resonant element and two transmission line segments 512 in which one end is connected to a pad 504 and other end serves as a terminal of the tunable filter. The signal pad 504 is isolated from other conductors disposed at the top conductor layer 5L1 by a clearance hole 503.

To show the effect of the apertures on the frequency characteristics, full-wave electromagnetic simulations were made by the Finite-Difference Time-Domain (FDTD) technique which is one of the most used numerical methods. A filter structure used in simulations was consisted of two same resonant elements which are shown in Figs. 5A to 5D. Signal via pads of these resonant elements were connected by a strip segment of 0.11mm width and length of 3mm. Also, 50Ohm transmission lines connected to signal via pads were used as terminals.

The characteristic dimensions of the resonant elements were as followings: the thickness of the substrate was 1.33mm; the thickness of copper conductor layers was 0.035mm; the signal via diameter was 0.5mm; ground vias of 0.25mm diameter surrounding the signal via were arranged as the square with the side of 3.0mm; the artificial dielectric was formed by the square conductive plates with the side of 2.4mm; the isolating slits separating these plates from the ground conductors had the width of 0.1mm; the signal pad diameter was 0.8mm; the clearance hole diameter was 1.0mm. In the bottom conductor layer of each resonant element, six identical rectangular apertures having the length of 1.4mm and the width of 0.1mm were arranged. These apertures are grouped as three pairs. Elements of each pair are disposed symmetrically with respect to the signal via. At the same time, the longer side of all apertures is parallel to the transmission line. The distance between apertures was 0.25mm.

Fig. 6 is a graph showing the effect of the floating plates of the filter comprising two same resonant elements presented in Figs. 5A to 5D. The graph shown in Fig. 6 includes six lines (a) to (f). The six lines (a) to (f) in Fig. 6 represent simulation results of three states for the six apertures of each resonant element disposed in the bottom conductor layer of the 8-conductor-layer substrate.

The lines (e) and (f) correspond to the first state for the position of the floating plates where only one pair of apertures in each resonant element is open. Here, the lines (e) and (f) respectively correspond to the parameters S11 and S21 of the filter.

The lines (c) and (d) correspond to the second state for the position of the floating plates where two pairs of apertures in each resonant element are open. Here, the lines (c) and (d) respectively correspond to the parameters S11 and S21 of the filter.

The lines (a) and (b) correspond to the third state for the position of the floating plates where all pairs of apertures in each resonant element are open. Here, the lines (a) and (b) respectively correspond to the parameters S11 and S21 of the filter.

Results shown in the graph of Fig. 6 by means of the S-parameters S11 and S21 verify tuning the filters realized by floating plates opening or closing apertures made in the bottom conductor layer.

(Further another exemplary embodiment)
Further another embodiment of a tunable filter of the present invention is shown in Figs. 7A to 7D.

Fig. 7A is a top view of a filter of a filter of another exemplary embodiment of the present invention. The filter of the present further another exemplary embodiment includes a signal via 701, a plurality of ground vias 702, a clearance hole 703, a signal via pad 704 and a microstrip line 712.

Fig. 7B is a vertical cross-sectional view of the filter shown in Fig. 7A on the 7B-7B section. The filter of the present further another exemplary embodiment further includes a dielectric material 705, a conductive plate 706, an isolating slit 707, a plurality of apertures 708 and a floating plate 713.

Fig. 7C is a vertical cross-sectional view of the filter shown in Fig. 7A on the 7C-7C section. Fig. 7D is a bottom view of the filter shown in Fig. 7A.

The above components are disposed similarly to the components of the filter shown in Figs. 1A to 1D, except the plurality of apertures 708 which form no pair and the floating plate 713 which is disposed over the bottom conductor layer 7L8 to entirely seal the apertures 708.

The filter shown in Figs. 7A to 7D includes a resonant element disposed in a multilayer substrate including three ground layer conductors 711 disposed in three conductor layers 7L1 to 7L3. These conductor layers 7L1 to 7L3 are isolated by a dielectric material 705.

In the present further another exemplary embodiment, the resonant element, formed by the signal via 701 surrounded by the plurality of ground vias 702, includes an artificial dielectric disposed between the signal via 701 and the plurality of ground vias 702. This artificial dielectric is obtained by the conductive plate 706 connected to the signal via 701 and separated from ground conductors by the isolating slit 707.

Also, this resonant element includes the plurality of apertures 708 arranged between the signal via 701 and the ground vias 702 in the bottom conductor layer 7L3.

To provide tuning of the resonant element, the floating plate 713 is designed under the bottom conductor layer 7L3. This floating plate 713 can provide one state in which all apertures 708 are closed and the other state in which all apertures 708 will be open. These two states are obtained by a mechanism 7M moving the floating plate 713 in the vertical (perpendicular to the substrate conductor layers) directions.

Open or closed apertures 708 can considerably change the capacitance of the resonant element and, in such way, its resonant frequency, according to the above equation (6).

The tunable filter in present embodiment is formed by the resonant element and two transmission line segments 712 in which one end is connected to the signal pad 704 and other end serves as a terminal. The signal pad 704 is isolated from other conductors disposed at the top conductor layer 7L1 by the clearance hole 703.

Fig. 8 is a graph showing an effect of the floating plate of the filter comprising two same resonant elements which are presented in Figs 7A to 7D. Signal via pads of these two resonant elements were connected by a strip of 0.11mm width and the length of 3mm. Input and output terminals were provided by 50Ohm transmission line segments connected also to the signal via pads. In Fig.8, S-parameter data are obtained by simulation for such filter formed by resonant elements similar to those shown in Figs. 7A to 7D. Dimensions of the resonant elements in this filter were as followings: the thickness of the substrate was 0.505mm; the thickness of copper conductor layers was 0.035mm; the signal via diameter was 0.7mm; a plurality of ground vias were arranged as the square with the side of 3.2mm; the ground via diameter was 0.3mm; the artificial dielectric was formed by the square conductive plates with the side of 2.6mm; the isolating slits separating these plates from the ground conductors had the width of 0.1mm; the signal pad diameter was 1.0mm; the clearance hole diameter was 1.4mm. In the bottom conductor layer of each resonant element, eight identical square apertures having the side of 0.3mm were arranged.

The graph shown in Fig. 8 includes four lines (a) to (d). The four lines (a) to (d) in Fig. 8 represent simulation results of two states for the eight apertures in the each resonant element.

The lines (a) and (b) correspond to the first state for the position of the floating plate where all apertures in the each resonant element are open. Here, the lines (a) and (b) respectively correspond to the parameters S11 and S21 of the filter.

The lines (c) and (d) correspond to the second state for the position of the floating plate where all apertures in the each resonant element are closed. Here, the lines (c) and (d) respectively correspond to the parameters S11 and S21 of the filter.

As one can see, the position of the passband for close and open states is different in the frequency domain. Thus, these states can serve for reconfiguration of a communication channel, for example.

While the present invention has been described in relation to some exemplary embodiments, it is to be understood that these exemplary embodiments are for the purpose of description by example, and not of limitation. While it will be obvious to those skilled in the art upon reading the present specification that various changes and substitutions may be easily made by equal components and art, it is obvious that such changes and substitutions lie within the true scope and spirit of the presented invention as defined by the claims.

Claims

A filter comprising:
a first terminal;
a second terminal; and
a resonant element connected to both said first terminal and said second terminal,
wherein said resonant element comprises:
a multilayer substrate;
a signal pad disposed in one of said plurality of conductor layers and connected to both said first terminal and said second terminal;
a plurality of ground vias, each of which is arranged through said multilayer substrate; and
a signal via arranged through said multilayer substrate, connected to said signal pad and surrounded by said plurality of ground vias,
wherein said multilayer substrate comprises:
a top conductor layer connected to one end of said signal via and one end of said each ground via;
a bottom conductor layer connected to other end of said signal via and other end of said each ground via;
at least one intermediate conductor layer disposed between said top and bottom conductor layers; and
a dielectric material disposed to isolate said top, said bottom and each of said at least one intermediate conductor layers from each other,
wherein said top conductor layer comprises:
a signal pad connected to said one end of said signal via, said first terminal and said second terminal;
a ground layer conductor connected to said one end of said each ground via; and
a clearance hole arranged to isolate said signal via from said ground layer conductor,
wherein said each intermediate conductor layer comprises:
a conductive plate connected to said signal via;
a ground layer conductor connected to said each ground via; and
an isolating slit arranged to isolate said conductive plate from said ground layer conductor,
wherein said bottom conductor layer comprises at least one aperture disposed between said signal and said ground vias, and
wherein said signal via, said conductive plate of said each intermediate conductor layer, said dielectric material disposed in an area surrounded by said plurality of ground vias and said at least one aperture act as an artificial dielectric with an effective permittivity different from a permittivity of said dielectric material.
The filter according to claim 1,
wherein said resonant element further comprises at least one floating plate disposed over said bottom conductor layer to entirely or partially open or close said at least one aperture,
wherein said effective permittivity changes based on a plurality of states of said at least one aperture entirely or partially open or closed.
The filter according to claim 2,
wherein said at least one aperture comprises:
a first group of aperture; and
a second group of aperture disposed symmetrically to said first group of aperture with respect to said signal via, and
wherein said at least one floating plate comprises:
a first floating plate disposed over said first group of aperture; and
a second floating plate disposed over said second group of aperture.
The filter according to claim 2 or 3,
wherein said plurality of states are provided by a mechanism which moves said at least one floating plate in a direction parallel to said bottom conductor layer.
The filter according to claim 2 or 3,
wherein said plurality of states are provided by a mechanism which moves said at least one floating plate in a direction perpendicular to said bottom conductor layer.
The filter according to any of claims 1 to 5,
wherein said plurality of ground vias are disposed in a square shape, and
wherein said signal via is disposed in a center of said square shape.
The filter according to any of claims 1 to 6,
wherein said first terminal comprises a planar transmission line disposed in said top conductor layer and of which one end is connected to said pad,
wherein said second terminal comprises another planar transmission line disposed in said top conductor layer and of which one end is connected to said pad, and
wherein said first and said second terminals are isolated from said ground layer conductor of said top conductor layer by said clearance hole.
The resonant element according to any of claims 1 to 7.