WO2004025771A1

WO2004025771A1 - Miniaturised radio frequency component

Info

Publication number: WO2004025771A1
Application number: PCT/GB2003/003830
Authority: WO
Inventors: Robert Brian Greed
Original assignee: Bae Systems Plc
Priority date: 2002-09-12
Filing date: 2003-09-03
Publication date: 2004-03-25
Also published as: GB0221125D0; AU2003263309A1

Abstract

A miniaturised radio frequency filter comprising a plurality of planes of resonators (22, 23, 42, 43). The component includes first and second electrically non-conductive resonator substrates (20, 40) mounted in a stacked arrangement. Signal couplings are provided within a plane of resonators and between the planes of resonators to provide additional coupling and cross-coupling paths.

Description

MINIATURISED RADIO FREQUENCY COMPONENT

The present invention relates to miniaturised radio frequency components comprising elements formed from patterned conductors, and to methods of manufacturing such components. More particularly, but not exclusively, the present invention relates to miniaturised radio frequency filters comprising resonators, formed from patterned conductors, which are cross- coupled, and to methods of manufacturing such filters.

Conventionally, radio frequency filters have been manufactured by arranging conductor patterns on a non-conductive substrate to form a series or

"cascade" of contiguous electrically or magnetically coupled elements.

Elements formed by the conductor patterns include so-called "lumped elements"

(such as inductors, capacitors, etc.), which operate at relatively low frequencies, and "distributed elements" (such as distributed transmission lines, stubs, resonators, etc.), which operate at relatively high frequencies. Elements that are adjacent, in terms of the cascade, may be coupled in phase or out of phase.

By selecting various individual elements, and by coupling them in various arrangements to form a cascade, radio frequency filters of various types (such as Chebyshev, elliptic or quasi-elliptic function filters) may be constructed which exhibit required frequency response characteristics. The performance of such filters is generally dictated by losses caused by the conductor materials, the substrate and by the enclosing package.

Miniaturisation is a continual objective in the electronic component industry. It is known that micro-machining methods, such as used in the semiconductor industry, may be used to create miniaturised radio frequency components. For example, the paper "Conductor-Loss Limited Stripline Resonator and Filter" by Chen-Yu and Gabriel M. Rebeiz, published in IEEE Transactions on Microwave Theory and Techniques, Vol. 44, No. 4, April 1996 describes using micromachining methods to manufacture a 20 GHz stripline filter on a silicon wafer capped with a 1.5 micron thick dielectric membrane.

However, with increasing miniaturisation of radio frequency components, performance tends to degrade. It is known that by suspending the elements (whether lumped or distributed) on a thin substrate in a cavity, improved performance may be achieved. In the above paper, it is described that a micro- machined cavity wafer is stacked on top of the membrane wafer to form the top cavity and a carrier wafer is stacked beneath the membrane wafer to form the bottom cavity. The unloaded quality factor (Q_u) of the resulting filter was measured and improved conductor-loss reported.

It is also known that the cross-coupling of the individual elements forming a radio frequency filter (i.e. arranging for electro/magnetic coupling between elements which are not adjacent in terms of the cascade of elements) enables significantly improved performance. As with couplings between adjacent elements in a cascade, cross-couplings may be in phase or out of phase. With elliptic or quasi-elliptic function filter types, for example, the use of multiple out of phase cross-couplings produces multiple transmission zeroes in the frequency response at or close to the filter band edges, thereby enabling improved rates of rejection of unwanted frequencies.

Many arrangements of cascaded elements with cross-coupling are known. For example, an analysis of one type of cross-coupled filters known as Cascaded Quadruplet (CQ) filters is given in "Direct Synthesis of Cascaded Quadruplet (CQ) Filters" by Ralph Levy, published in IEEE Transactions on Microwave Theory and Techniques, Vol. 43, No. 12, December 1995. Cross- coupling of radio frequency filter elements realised in microstrip form is also known - see "On the Development of Superconducting Microstrip Filters for Mobile Communications Applications" by Jia-Sheng Hong, Michael J. Lancaster, Dieter Jedamzik and Robert Greed, in IEEE Transactions on Microwave Theory and Techniques, Vol. 47, No. 9, September 1999. The paper describes the manufacture of a planar microstrip filter comprising eight meander open-loop resonators arranged in a cascade with one cross-coupling, as shown in Figures 4 and 5 of that paper.

With the introduction of cross-couplings, whether in or out of phase, the performance of radio frequency components may be improved when miniaturisation is sought. However, the design freedom to introduce cross- coupling of elements in known micro-machined radio frequency components is limited.

Accordingly, it would be desirable to manufacture miniaturised radio frequency components, such as radio frequency filters, in which elements may be cross-coupled with greater freedom.

One object of the present invention is to enable the manufacture of miniaturised radio frequency components using micro-machining techniques in which the constraints on cross-coupling are reduced.

Another object of the present invention is to enable the manufacture of miniaturised radio frequency components with improved performance characteristics.

According to a first aspect of the present invention, there is provided a miniaturised radio frequency component comprising a plurality of electrically conductive patterned elements arranged in the component to process a signal between a signal input path and a signal output path by coupling the signal between the patterned elements, the component including: first and second electrically non-conductive substrates mounted in a stacked arrangement; a first said element supported on the first substrate; a second said element supported on the second substrate; and a third said element supported on the first substrate, wherein the component is arranged to provide a first signal coupling between the first element and the second element and a second signal coupling between the first element and the third element. By arranging at least the second element on a second substrate, which is not in the plane of the first substrate, three-dimensional coupling and cross- coupling arrangements may be achieved between the patterned elements with greater freedom than in conventional two-dimensional planar arrangements, thereby improving component performance when providing miniaturisation. Preferably, a conductive layer is disposed between the first and second substrates, the conductive layer being optionally supported on a third planar, non-conductive substrate. Thereby, electric and magnetic interference between elements on each substrate may be controlled.

In one embodiment of the present invention, the component includes a conductive spanning element providing a signal coupling between parts of the respective conductor patterns of said elements. Preferably, where a conductive layer is disposed between the first and second substrates, the conductive spanning element passes through a hole in the conductive layer. Thus, electrical cross-coupling, including both in-phase and out-of-phase coupling, may be achieved between the supporting substrates, by suitably arranging parts of the conductive spanning element thereon.

In another embodiment of the present invention, the first and second substrates are arranged such that the areas occupied by the second element and the first element at least partially overlap thereby allowing magnetic coupling between said elements. Preferably, where a conductive layer is disposed between the first and second substrates, the second element and the first element are magnetically coupled by a hole in the conductive layer between them. Thus, magnetic coupling, including both in-phase and out-of-phase cross- coupling, may be achieved between the elements by suitably arranging the elements with respect to each other in the stack and by suitably configuring a hole in the conductive layer.

Preferably, the first and second substrates are disposed between and spaced apart from two enclosing conductive layers, each said conductive layer being optionally supported on a respective planar, non-conductive substrate.

Thereby, the stacked arrangement of substrates is electrically and magnetically shielded from external interference.

Further aspects of the invention are set out in the appended claims.

There now follows, by way of example only, a detailed description of preferred embodiments of the present invention, given with reference to the accompanying drawings. Figure 1 is an exploded, selectively cut-away, perspective view of a stacked and layered arrangement of a radio frequency filter comprising resonator elements arranged on different membrane substrates magnetically coupled by means of two holes in a conductive ground plane between the membranes;

Figure 2 is a schematic diagram showing a signal coupling path provided in the component illustrated in Figure 1 ;

Figure 3 is an exploded, selectively cut-away, perspective view of a stacked and layered arrangement of a radio frequency filter comprising resonator elements arranged on different membrane substrates electrically coupled by means of two conductive probes;

Figure 4 is a perspective view of the conductor patterns and conductive probes of the radio frequency filter of Figure 3 with the substrates and conductive ground planes removed for clarity; and Figure 5 is a schematic diagram showing a signal coupling path provided in the component illustrated in Figures 3 and 4.

According to the present invention, radio frequency components are manufactured using micro-machining processes. In particular, bulk machining and surface additive machining are used. Surface additive machining involves the selective deposition or plating of one or more layers of a conductor or insulator onto a substrate surface. Bulk machining involves selective etching of conductor or insulator material from a base substrate. Both processes use two- dimensional graphic patterns to deposit or remove selectively insulator or conductor material. By combined and repeated processes of surface additive machining and bulk machining, and bonding of stacked layers, three- dimensional structures are constructed.

Figure 1 is an exploded view of a stacked and layered arrangement of a radio frequency filter comprising resonator elements arranged on different substrates magnetically cross-coupled by means of two holes in a conductive ground plane between the resonators. The filter includes an upper shielding cavity arrangement 10, an upper resonator arrangement 20, an intermediate conductive ground plane 30, a lower resonator arrangement 40 and a lower shielding arrangement 50.

The filter comprises four meander open-loop resonators 22, 23, 42, and 43 supported on two planar dielectric substrates 21 , 41. Each substrate supports two respective resonators 22, 23; 42, 43, individually configured and arranged adjacent one another to provide a signal coupling of a desired phase relationship between the two adjacent resonators. The upper and lower shielding arrangements 10, 50 each include a dielectric substrate 11 , 51 coated with a conductive deposition layer 12, 52 forming a ground plane. The dielectric substrates 11 , 51, each include a relatively thick outer frame and a relatively thin ground plane support membrane, arranged to form upper and lower cavities inside the component. As shown in Figure 1 , the upper shielding arrangement has a dielectric ground plane support membrane 13, conductive deposition 12 and a frame 14. Each of the dielectric substrates may be made for example of silicon, gallium arsenide, quartz or glass, and the respective substrates may have a thickness in the region of 100 micron to 600 micron, preferably approximately 500 micron in thickness. In the case of the substrates being etched out or formed from two separate parts to form membranes supported on a frame, the frames may have a thickness in the region of 100 micron to 600 micron whilst the respective membranes may have a thickness of about 0.2 micron to 2 micron, preferably 1 micron to 1.5 micron in thickness.

The resonators 22, 23, 42, 43 are formed from conductor patterns deposited on the substrate layers using deposition techniques. The conductor patterns may be formed from aluminium, copper or gold. The conductive patterns and other conductive layers may have a thickness of about 1 micron to

5 micron in thickness, preferably approximately 2 micron.

The upper resonator patterns include input and output connections 24,

25 respectively which cross the width of the frames of the upper and lower shielding arrangements 10, 50. These connections may directly connected as shown or otherwise electrically or magnetically coupled to the resonators. On each substrate 21 , 44, thin conductive ground plane connector layers 26, 27, 44, 45 are deposited on the periphery of each side of the substrate on opposite sides to the conductor patterns. The connector layers have a width corresponding approximately to the width of the frames of the upper and lower shielding arrangements 10, 50. The intermediate ground plane may be formed by deposition directly onto the lower side of the upper resonator arrangement 20. Via holes 28, 46 coated by deposition with a conductive layer, are formed in the resonator substrates to provide electrical connections between each of the ground planes formed by the conductive layers 12, 30, 52.

The resonator substrates 20, 40 are stacked either side of the intermediate ground plane 30, which covers substantially all the substrate area except for two holes 31 , 32 with the dielectric membranes facing each other adjacent the intermediate ground plane 30.

The two holes 31 , 32 in the conductive ground plane are sized, shaped and located such that selected parts of resonators 23 and 24 are appropriately magnetically coupled to parts of resonators 42 and 43 to provide a desired phase relationship in the signal coupling. The holes overlie one side of the respective resonators between which a signal coupling is being provided. Either in phase or out of phase coupling may be achieved between the resonators by positioning the hole adjacent different parts of each resonator. The remainder of the intermediate ground plane 30 electrically and magnetically isolates the remainder of the resonators and conductor patterns.

Layers 10 and 50 are constructed from two planar substrate layers which are partially etched, but not etched completely through the substrate, leaving for example a thin membrane 13 in substrate layer 11 , and not etched at the perimeter of the substrate layers, leaving for example square or rectangular frame 14 which is relatively thick. The conductive layers 12, 52 are then deposited across each of the partially etched areas. The conductive layers 12, 52 act as shielding for the component. The shielding arrangements 10, 50 are stacked on either side of the resonator arrangements 20, 40 and bonded at the periphery creating two air cavities in which the resonator patterns are suspended. The conductor pattern dimensions across the relatively short width of the frames, which lie across the input and output connections 24, 25, are configured to reduce the degrading effect on performance.

Figure 2 shows in schematic view the cross-coupling provided by the arrangement of resonators in the embodiment of Figure 1 between the input connection 24 and the output connection 25. Each resonator is shown as a node of the signal path, represented by solid and dotted lines. Note that, in the case of two resonators being formed adjacent one another on a plane, if the free ends of the resonator patterns are located immediately adjacent one another, the coupling is a primarily electric coupling in which the relatively high voltages generated at the free ends are coupled. On the other hand, if the resonators are located with continuous line parts of the resonator elements immediately adjacent, the coupling is primarily magnetic. The first resonator 22 is coupled by magnetic interaction via the first coupling hole 31 to the second resonator 42. The first resonator 22 is also coupled by electric interaction with the adjacent third resonator 23. The second resonator 42 is also coupled by magnetic interaction with the adjacent fourth resonator 43. The fourth resonator 43 is coupled by magnetic interaction via the second coupling hole 32 to the third resonator 23.

Figure 3 is an exploded view of a stacked and layered arrangement of a radio frequency filter comprising resonator elements arranged on thin membrane layers electrically cross-coupled between by means of two conductive probes. The filter includes an upper shielding arrangement 60, an upper resonator arrangement 70, an intermediate ground plane arrangement 80, a lower resonator arrangement 90 and a lower shielding arrangement 100. The component comprises three intermediate substrate frames 71 , 81 , 91 which are rectangular or square and have etched centres. On each of these frames, a thin dielectric membrane 72, 82, 92 is bonded to the frame to cover substantially all the frame area. Alternatively, the membranes and frames may be integrally formed by an etching process. Four meander open-loop resonators 73, 74, 93, 94 are formed from conductor patterns deposited on the dielectric membranes 72, 92 of resonator arrangements 70, 90. Signal input and output connections 95, 96 are formed on the lower resonator arrangement 90 but in alternative arrangements of the resonators the connections could be formed on different layers. The conductor pattern dimensions at 95, 96 across the relatively small width of the frames 81 , 91 are configured to reduce the degrading effect on performance at the signal input and outputs 95, 96.

A conductive ground plane 83 covering substantially all the substrate area except for two routing holes 84, 85, and coupling holes 86, 87, is deposited on the dielectric membrane 82 of intermediate ground plane arrangement 80. The three intermediate arrangements 70, 80, 90 are stacked on top of each other and bonded together via their frames to form two air cavities, one between dielectric membrane 72 and the conductive ground plane 83, the other between dielectric membrane 82 and the lower resonator patterns 93, 94.

The resonators are coupled via magnetic coupling holes 86, 87, which are sized, shaped and located such that selected parts of resonators 73, 74 are appropriately magnetically coupled to parts of resonators 94, 93 respectively to provide the main signal coupling paths in the filter component.

Additional cross-couplings are provided through parts of each of the resonators 73, 74, 93, 94, which are located adjacent to parts of two conductive probes 75, 76 and primarily magnetically coupled thereto. The conductive probes may be made for example of metallic wire of about 20 microns diameter, metallic tape of about 20 micron thick or fabricated as metal-coated vias using micro-machining techniques, and are routed through coupling holes 84, 85 without forming electrical contact with the conductive ground plane, the holes 84, 85 may for this purpose be insulated about their periphery. The coupling holes are of small cross-sectional areas relative to the cross-sectional area of the resonators. By locating parts of the conductive probes adjacent to selected parts of the resonators either in phase or out of phase coupling may be achieved between the resonators. The remainder of conductive ground plane 83 electrically and magnetically isolates the remainder of the resonators and conductor patterns.

Upper shielding arrangement 60 is constructed from a planar substrate 61 which is partially etched, but not etched completely through the substrate, leaving a thin membrane 63, and not etched at the perimeter of the substrate layers, leaving a square or rectangular frame 64. A conductive layer 62 is then deposited across the partially etched area. Thus, layer 62 is similar to layer 12 in the embodiment of Figure 1 and forms an upper ground plane. Upper shielding arrangement 60 is stacked and bonded on top of intermediate arrangements 70, 80, 90 creating an air cavity above the resonator patterns which are suspended therein. In the lower shielding arrangement 100, a conductive ground plane 102 covering substantially all the substrate area is deposited on a dielectric substrate layer 101. The remaining arrangements 60, 70, 80, 90 are stacked and bonded on top of lower shielding arrangement 100, creating air cavities beneath the resonator patterns suspended therein.

In this embodiment, each of the dielectric substrates may be made for example of silicon, gallium arsenide, quartz or glass, and the respective substrates and frames may have a thickness of about 100 micron to 600 micron, preferably approximately 500 micron. The respective membranes may have a thickness of about 0.2 micron to 2 micron, preferably 1 micron to 1.5 micron. The conductive patterns and layers may have a thickness of about 5 micron to 1 micron, preferably approximately 2 micron.

In Figure 3, ground plane connector layers and via holes are not shown, however it should be appreciated that appropriate electrical connections are made between all three of the ground planes 62, 83, 102.

Figure 4 is a view of the conductor patterns forming the resonator elements of the radio frequency filter of Figure 3 with the membranes, conductive ground planes and substrate frames removed for clarity. Thus, only input and output connections 95, 96, resonators 73, 74, 93, and 94 and conductive probes 75, 76 are shown.

Figure 5 shows in schematic view the cross-coupling provided by the arrangement of resonators in the embodiment of Figures 3 and 4 between the input connection 95 and the output connection 96. Each resonator is shown as a node of the signal path, represented by solid, dash-dotted and dashed lines. The first resonator 93 is coupled by magnetic interaction with the fourth resonator 73 via coupling hole 86 and by magnetic interaction via the first coupling probe 76 to the second resonator 74. The first resonator 93 is also coupled by electric interaction with the adjacent third resonator 94. The third resonator 94 is coupled by magnetic interaction with the second resonator 74 via the coupling hole 87 and by magnetic interaction via the second coupling probe 75 to the fourth resonator 73. The fourth resonator 73 is also coupled by electric interaction with the adjacent second resonator 74.

Whilst in the above embodiments, only two resonator elements per plane are coupled and cross-coupled in two stacked planes, in further embodiments of the invention, more than two resonator elements, for example four or above, may be included in at least one of the planes. Furthermore, three or more resonator planes may be stacked, coupled and cross-coupled in a single component.

Whilst in the first embodiment, the resonator substrates are in the form of a solid planar dielectric substrate as shown in Figure 1 , they may alternatively be manufactured in the form of membranes supported on outer frames similar to the resonator arrangements shown in Figure 3. In relation to the arrangements shown in Figure 3, whilst the resonator patterns are formed on the planar surface of the membrane opposite the etched-out surface, alternatively the resonator patterns may be formed on the opposite side of the membrane inside the cavity formed by the etched-out surface.

Whilst in the embodiment shown in Figure 1 , only magnetic couplings are used between the resonator arrangements, in alternative embodiments of the invention the magnetic couplings can be replaced or augmented by electric couplings similar to those shown in Figure 3. Further, whilst a mixed electric and magnetic coupling arrangement is shown in Figure 3, in alternative embodiments only magnetic or only electric couplings may be used.

It should be appreciated that filters comprising one or more resonators or other elements, such as "lumped elements" or "distributed elements", arranged in each of the one or more planes may be constructed according to the present invention. The elements of each plane may be coupled together to form a cascade and cross-coupled with each other within the constraints of the planar topology. The coupling/cross-coupling may be either in or out of phase. Furthermore, elements of adjacent layers or non-adjacent layers may be electrically or magnetically coupled together to extend the cascade or cross- coupling.

It should also be appreciated that a variety of other radio frequency components may be constructed according to the present invention - for example, diplexers and multiplexers. Thus, it can be seen that radio frequency components may be manufactured according to the present invention with significantly greater design freedom to introduce coupling and cross-coupling, whether in- or out of phase, between various elements. The components produced in accordance with the invention may be included in a radio frequency system including a digital electronic control system, such as a radio frequency transceiver.

Herein, the term "radio frequency" is intended to cover a broad range of frequencies. The term includes frequencies in the region spanning hundreds of MHz to hundreds of GHz inclusive.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. A miniaturised radio frequency component comprising a plurality of electrically conductive patterned elements arranged in the component to process a signal between a signal input path and a signal output path by coupling the signal between the patterned elements, the component including: first and second electrically non-conductive substrates mounted in a stacked arrangement; a first said element supported on the first substrate; a second said element supported on the second substrate; and a third said element supported on the first substrate, wherein the component is arranged to provide a first signal coupling between the first element and the second element and a second signal coupling between the first element and the third element.

2. A miniaturised radio frequency component according to claim 1 , wherein the first element and the second element are arranged in an at least partially overlapping stacked configuration.

3. A miniaturised radio frequency component according to claim 1 or 2, wherein the first element and the third element are arranged immediately adjacent one another on the first substrate.

4. A miniaturised radio frequency component according to claim 1 , 2 or 3, further including a fourth said element supported on the second substrate, wherein the component is arranged to provide a third signal coupling between the fourth element and the second element and a fourth signal coupling between the fourth element and the third element.

5. A miniaturised radio frequency component according to any preceding claim, comprising an intermediate conductive layer mounted in the stacked arrangement between the first substrate and the second substrate.

6. A miniaturised radio frequency component according to claim 5, wherein the intermediate conductive layer forms a common ground plane for elements supported on both the first and second substrates respectively.

7. A miniaturised radio frequency component according to claim 5 or 6, wherein the second signal coupling includes an aperture in the intermediate conductive layer.

8. A miniaturised radio frequency component according to claim 7, wherein the aperture in the intermediate conductive layer is positioned and shaped so as to provide a magnetic signal coupling having a selected phase relationship between the first and second elements.

9. A miniaturised radio frequency component according to claim 5, 6, 7 or 8, wherein the second signal coupling includes an electrically conductive spanning element traversing said intermediate conductive layer.

10. A miniaturised radio frequency component according to claim 9, wherein the electrically conductive element includes a first part supported on the first substrate and a second part supported on the second substrate, the first and second parts being positioned and shaped so as to provide a signal coupling having a selected phase relationship between the first and second elements.

11. A miniaturised radio frequency component according to any preceding claim, comprising first and second enclosing conductive layers, the first and second substrates being mounted in the stacked arrangement between the first and second enclosing conductive layers.

12. A miniaturised radio frequency component according to any preceding claim, wherein at least part of the first and/or second substrates are in the region of 100 micron to 600 micron in thickness.

13. A miniaturised radio frequency component according to any preceding claim, wherein the first and/or second substrate is in the form of a relatively thin membrane supported on a thicker frame.

14. A miniaturised radio frequency component according to claim 13, wherein the membrane and the frame are integrally formed.

15. A miniaturised radio frequency component according to claim 13 or 14, wherein the membrane has a thickness in the region of 0.2 to 2 micron.

16. A miniaturised radio frequency component according to any preceding claim, including one or more further electrically non-conductive substrates mounted in the stacked arrangement, one or more said elements being supported one each of said further substrates and coupled to one or more of the other said elements of the component.

17. A miniaturised radio frequency component according to any preceding claim, including one or more further said elements supported on said first substrate and coupled to one or more of the first and third said elements.

18. A miniaturised radio frequency component according to any preceding claim, wherein said elements are resonator elements.

19. A miniaturised radio frequency component according to any preceding claim, wherein the component is a radio frequency filter.

20. A radio frequency system comprising a component according to any preceding claim and a digital electronic control system.

21. A method of manufacturing a miniaturised signal processing component, the method comprising the steps of: depositing Conductive patterns on a first non-conductive substrate to form at least a first and a third element, the first and the third element being coupled together; depositing conductive patterns on a second non-conductive substrate to form at least one second element; arranging the first and second substrates in a stacked arrangement such that the second element is coupled to the first element.

22. A method according to claim 21 , comprising the step of etching the first substrate and/or the second substrate to form a relatively thin membrane supported on a thicker frame.

23. A miniaturised signal processing component comprising: a first electrically conductive patterned element and a third electrically conductive patterned element, the first and the third element being coupled together, the elements being supported on a first non-conductive substrate in a first cavity; a second electrically conductive patterned element coupled to the first element and formed from a conductor pattern supported on a second non-conductive substrate in a second cavity, the first and second cavities being arranged in a stacked configuration.

24. A miniaturised radio frequency component comprising a plurality of electrically conductive patterned elements arranged in the component to process a signal between a signal input path and a signal output path by coupling the signal between the patterned elements, the component including: at least one said element supported on a first electrically non-conductive substrate; and at least one said element supported on a second electrically non- conductive substrate, wherein the first and second substrates are mounted in a stacked arrangement and the component is arranged to couple a signal between the at least one said element on the first substrate and the at least one element on the second substrate.