WO2005034593A2

WO2005034593A2 - Substrate comprising a tuneable electrical component and use of the same

Info

Publication number: WO2005034593A2
Application number: PCT/EP2004/052067
Authority: WO
Inventors: Oliver Dernovsek; Richard Matz; Ashkan Neaini; Carsten Schuh; Wolfram Wersing
Original assignee: Siemens Aktiengesellschaft
Priority date: 2003-09-29
Filing date: 2004-09-07
Publication date: 2005-04-14
Also published as: WO2005034593A3

Abstract

The invention relates to a substrate (1) comprising at least one tuneable electrical component (2, 22). According to the invention, a volume section (11) of the substrate is provided with at least one cavity (3) that is partially filled with a continuous strip (4) of fluid having a determined electrical property in such a way that the position of the strip of fluid in the cavity can be modified. Said fluid strip is arranged in the cavity such that an electrical operating variable of the electrical component can be modified by a modification of the position of the fluid strip. The invention enables a concept described as "software defined radio" to be implemented. The position of the fluid strip can be modified in any way, enabling both a digital and a continuous modification of the operating variable of the tuneable electrical component to be achieved. Preferably, the substrate is a ceramic multilayer substrate formed by low temperature co-fired ceramics technology. The inventive substrate provided with the component is used, for example, for tuning the frequency of a mobile radio telephone.

Description

description

Substrate with a tunable electrical component and use of the substrate with the component

The invention relates to a substrate with at least one tunable electrical component and a use of the substrate with the component.

Modern mobile phones are operated with different frequency ranges. Switching from frequency range to frequency range takes place, for example, using PIN diodes. Due to an increasing variety of bands and standards, switching using the PIN diodes is very complex. In addition, the power consumption of the PIN diodes is relatively high.

A change in the frequency range of a mobile phone can be achieved with the help of varactor diodes (varactors). A varactor diode is a semiconductor component with a voltage-dependent capacitance. The change in the frequency range can also be achieved via controllable paraelectric capacitors, the capacitance of which is also voltage-dependent. The capacity of these components is a variable operating size of the components. The components are tunable. However, since the operating variable "capacity" can only be changed in a relatively small frame with these tunable components, the frequency range of a mobile radio telephone can also only be changed in a relatively small frame.

The object of the present invention is to provide a possibility of how an operating variable of a tunable electrical component can be changed in a significantly wider range compared to the prior art.

To achieve the object, a substrate with at least one tunable electrical component is specified, In the volume section of the substrate, at least one cavity is arranged, which is partially filled with a continuous fluid band of a fluid with a certain electrical property, so that a position of the fluid band in the cavity can be changed and the fluid band is arranged in the cavity in such a way that by a change the position of the fluid band in the cavity, an electrical operating variable of the electrical component can be changed ver.

With the invention, a concept can be realized that as

"Software Defined Radio" is called. The position of the fluid band can be changed as desired. This makes it possible to achieve both a digital and a continuous change in the operating size of the tunable electrical component.

The substrate is an arbitrary circuit carrier. The component is preferably a passive electrical component. The passive electrical component is, for example, an electrical resistance with the "electrical" operating variable

Conductivity ", a capacitor with the operating size" capacitance "or a coil with the operating size" inductance ". The electrical property of the fluid is, for example, electrical conductivity or permeability. A tunable resistor can also be integrated into the substrate. The passive components mentioned are, for example, components of a potentiometer or the like.

The fluid is present as a coherent fluid band (liquid band). This means that the fluid is a coherent liquid. The liquid can be single or multi-phase. This fluid band can be moved within the cavity. For this purpose, the fluid is advantageously characterized by a low wettability of the cavity boundary. The fluid essentially does not spread itself on the cavity boundary. The fluid can thus be localized in certain areas of the cavity. The fluid can be liquid, pasty or gel-like. The fluid can be a pure substance. For example, the fluid is a liquid metal or a liquid solvent. A mixture of solvents, for example a mixture of water and alcohol, is also conceivable. Various substances can also be dissolved in the solvent or the solvent mixture. For example, ions can be contained in a water, which contribute to the electrical conductivity of the fluid. In addition, the fluid can also be in the form of a dispersion or emulsion.

The position of the fluid band in the cavity can be changed by exerting an electrical, magnetic and / or mechanical force on the fluid. In particular, the

The position of the fluid band in the cavity can be changed electrostatically, magnetohydrodynamically and / or piezoelectrically. In each of the cases mentioned, a force is exerted on the fluid which ensures that the fluid is moved in the cavity. For a defined setting of the operating size of the tunable component, its position in the cavity remains constant after the fluid band has been moved.

The position of the fluid band is preferably caused by the application of an electrical field. To change the position of the fluid band, an electrical charge can be applied to the fluid, so that the fluid band can be moved in the electrical field and thus in the cavity. In the case of the magnetohydrodynamic movement of the fluid, an electromagnetic field is created. The fluid is characterized by a paramagnetic or diamagnetic material.

It is also conceivable that a piezoelectric transducer is used which exerts a force on the fluid by electrical control and thus a change in the position of the

Fluids causes. The piezoelectric transducer can exert the force directly on the fluid. The converter is preferably integrated in the substrate with the tunable component. It is also conceivable that the force is exerted on the fluid indirectly via a force transmission medium. The power transmission takes place, for example, hydraulically or pneumatically. The converter can be arranged outside the substrate with the electrical component. The power transmission medium is advantageously designed such that it essentially does not influence the operating size of the component.

The electrical operating size of the component is influenced by changing the position of the fluid in the cavity. For example, the component is a capacitor. Such a capacitor can be referred to as a "sliding capacitor". A region of the cavity of the substrate is arranged between the electrodes of the capacitor. At least one further area of the cavity is not arranged between the electrodes of the capacitor, that is to say outside of the capacitor. The fluid can be moved between the two areas of the cavity. Since the fluid is characterized by a certain permeability, the capacitance of the capacitor depends on the position of the fluid band in the cavity. The higher the permeability of the fluid, the more sensitive the capacitance of the capacitor is to the change in the position of the fluid band. A high-dielectric fluid is therefore preferably used. Such a fluid is characterized by a dielectric constant of over 50. The dielectric constant of pure water is, for example, about 80 at room temperature. It is advantageous to use an emulsion or a dispersion of a high-dielectric material.

According to a special embodiment, the cavity is delimited by an electrode of the electrical component. It is therefore possible that the electrode and the direct contact are in contact or can be brought into contact by changing the position of the fluid band in the cavity. If the electrical de and the fluid band are in direct contact, electrical charge can be transferred from the electrode of the component to the fluid by electrical control of the electrode of the component. In addition, the electric field generated by applying a voltage to the electrodes of the capacitor can be efficiently coupled into the fluid. It is also conceivable that the electrical charge on the fluid is transferred from a further electrode of a further electrical component to the fluid band. By applying the electric field, the fluid band is moved in the cavity such that the fluid band is first brought into contact with the electrode of the tunable component.

Instead of the sliding capacitor described, a so-called sliding resistance can also be implemented. An electrically conductive fluid is placed between two electrodes that directly delimit the cavity. The fluid band and the electrodes are in direct contact with one another. An electrical short circuit occurs when the fluid band comes into contact with the electrodes of the capacitor. The level of electrical resistance of such an arrangement depends, among other things, on the electrical conductivity of the fluid. The fluid can be an electron conductor. For example, the fluid is a resistance paste. A fluid in the form of an ion conductor is also conceivable. The ion conductor is, for example, a solution of a solvent and ions dissolved in it. The solvent is, for example, water or another polar solvent such as ethanol or the like.

In a special embodiment, the cavity is closed. The fluid cannot flow out of the cavity or out of the substrate with the cavity. This ensures that the position of the fluid band can be changed. For example, the cavity has a bypass, which enables pressure equalization necessary for moving the fluid. The substrate can be any circuit carrier made of an organic or inorganic material. For example, a substrate made of silicon is conceivable, into which structures are introduced by so-called "micromachining". In a special embodiment, the substrate is a multilayer substrate and the cavity is formed by a recess which is continuous in the thickness direction of at least one layer of the multilayer substrate. The multi-layer substrate can be a multi-layer substrate with layers of one plastic or of several plastics.

A multilayer substrate made of layers made of a ceramic material is advantageous. Such a multilayer body is, for example, a so-called HTCC (high temperature co-fired ceramics) substrate. The multilayer substrate is preferably an LTCC (Low Temperature Cofired Ceramics) substrate. The ceramic used in such a substrate is a glass ceramic that densifies at a relatively low sealing firing temperature. Due to the low sealing firing temperature, electrically tunable materials such as silver or copper, which melt at a relatively low temperature, can be integrated in the volume of the substrate for the tunable electrical component and further electrical components integrated in the substrate. The quality of the components made with these materials is therefore relatively high.

In addition, with the LTCC technology (and the HTCC technology) different ceramic materials with different electrical properties in the volume of the

Substrate to be integrated. In this way, a highly dielectric ceramic material can be used directly adjacent to the cavity, which promotes the coupling of the electric field into the fluid. For this purpose, the recess for forming the cavity is made, for example, in a layer made of the high-dielectric ceramic material. Conceivable is also that an adjacent layer delimiting the cavity has the high-dielectric ceramic material.

To produce the multilayer substrate using LTCC technology, for example, ceramic green foils, which have appropriate ceramic materials and are possibly provided with appropriate metal structures, are structured, stacked one above the other, debindered and sintered to form a monolithic ceramic body. The structuring includes the creation of a recess in at least one of the ceramic green sheets, from which the cavity is formed after sintering. Likewise, possibly required channel structures for filling the cavity with the fluid and / or for forming a bypass required for moving the fluid band in the cavity are introduced.

The tunable electrical component of the substrate is used in a wide variety of applications. The tunable electrical component of the substrate is preferably used for digitally controlling an operating frequency of a microwave oscillator, for controlling a pass and / or blocking behavior of a frequency filter and / or for adapting at least two circuits. In particular, the tunable electrical component is used to set a frequency range of a mobile radio telephone used for transmitting and / or receiving electromagnetic waves.

In summary, the following significant advantages result from the present invention:

The arrangement of the fluid in the cavity makes it possible to coordinate the operating size of an electrical component over a wide range. - In particular, the integration of the component and the cavity in an LTCC substrate leads to an inexpensive, compact and variable solution.

The invention is explained in more detail below with the aid of several exemplary embodiments and the associated figures. The figures are schematic and do not represent true-to-scale illustrations.

FIG. 1 shows a multilayer substrate with several tunable capacitors in a lateral cross section.

FIG. 2 shows an equivalent circuit diagram of the electrical circuit with the tunable capacitors from FIG. 1.

FIG. 3 shows a further multilayer substrate with several tunable capacitors in a lateral cross section.

FIG. 4 shows an equivalent circuit diagram of the electrical circuit with the tunable capacitors from FIG. 3.

FIG. 5 shows a multilayer substrate with a short-circuit slide or a tunable coplanar line.

FIG. 6 shows a multilayer substrate with tunable resonators.

FIG. 7 shows various contacting concepts that can be integrated in a multi-layer substrate.

FIG. 8 shows calculated transmission spectra for a bandpass filter at different resonator lengths.

Several tunable electrical components 2 are integrated in an LTCC substrate 1. The substrate 1 is a ceramic multilayer substrate 12, which consists of several, each one Ceramic layers 13 to 18 comprising glass ceramic.

A cavity 3 is present in a volume section 11 of the substrate 1, which is introduced into one of the ceramic layers (layer 14). In this cavity 3, a coherent fluid band 4 is arranged from a fluid with a certain electrical property. The position of the fluid band 4 can be changed within the cavity 3.

The cavity 4 extends over the entire layer thickness 141 of the layer 14 and is delimited by adjacent ceramic layers 13 and 15. At least one electrode 21 of the electrical component 2 delimits the cavity 3 and is in contact with the fluid 4.

Example 1:

The tunable, variable electrical component is a capacitor 23, which can be referred to as sliding capacitors (FIG. 1). The capacitor is suitable for high frequency applications. The fluid of the fluid band 4 is highly dielectric. The position of the fluid band is changed electrostatically with the aid of control electrodes 30. Depending on the dielectric constant of the glass ceramic of the ceramic layers 13 to 18, in particular the ceramic layers 13 and 15 adjacent to the cavity 3 with the fluid band 4, the capacitance can be of the capacitors can be varied 8 to 60 times by varying the position of the fluid band. The ceramic layers 15 to 17 consist of a high-dielectric glass ceramic with a dielectric constant of approximately 80. The ceramic layers 13 and 18 have a glass ceramic with a dielectric constant of approximately 6.

The smallest capacity level results from the geometry for the application of the static electric field used control electrodes 30. A typical value for LTCC technology is about 0.1 pF.

Figure 2 shows an equivalent circuit 5 of this example. For completion, further electrical components are included, which are not shown in FIG. 1. These further components include, for example, coils 23, groundings 24 and further capacitors 25.

Together with further tunable and / or non-tunable capacitors and tunable and / or non-tunable inductors, tunable resonant circuits can be formed.

With tunable capacitors, integrated line resonators, for example λ / 4 lines, can also be integrated into the substrate.

Example 2:

In contrast to the previous example, a fluid band 4 with an electrically highly conductive fluid is used (FIG. 3). The fluid 4 consists of mercury. An electrode 25 of the tunable capacitor 23 does not delimit the cavity 3. The ceramic layer 13 also consists of a high-dielectric glass ceramic, so that an efficient coupling of the electric field indirectly into the fluid band 4 is possible via the layer 13.

Compared to the previous example, this solution has the advantage that the feed chokes shown in the equivalent circuit diagram (FIG. 4) and integrated in the substrate for the electrostatic drive of the fluid band and decoupling and blocking capacitors can be omitted. Example 3:

According to this exemplary embodiment, a sliding resistance is implemented (FIG. 5). The fluid of the fluid band 4 consists of a low-viscosity resistance paste with a certain electrical conductivity.

Example 4:

A tunable coplanar line with ground line is integrated in a multilayer substrate 12 on the rear side of the line dielectric (cf. FIG. 5). Here the fluid is electrically highly conductive. The fluid consists of mercury. The coplanar line, which is variable in length as a result, can be tuned within wide frequency limits for impedance adaptations

Resonators and filters tunable within wide frequency limits, etc. used.

Example 5:

Tunable resonators with vertically superimposed stripline lines 61 are integrated in a multilayer substrate 12 (FIG. 6). The line lengths of the stripline lines 61 are approximately 10 mm. For the sake of clarity, the other circuit elements are just like that

Stripline cables are arranged horizontally and symmetrically to the center of the substrate.

A cavity 3 is located between the coupled stripline lines 61. A fluid band 4 made of mercury is located in the cavity 3. The fluid band 4 is electrically conductively connected to ground potential 62.

A piezoelectric membrane 63 is provided to change the position of the fluid in the cavity 3. By changing the position of the fluid band 4 in the cavity 3, the length changes the line up to the ground potential 62 and thus the center frequency of a filter constructed with the resonator.

On the back of the membrane 63 there is another cavity 64 which is hermetically sealed by a cover 65. To balance the pressure, the left end of the cavity 3 in the interior of the multilayer substrate 12 is connected to the further cavity 64.

The membrane 63 is round and has a radius r of approximately 2 mm. With a center deflection h of approximately 20 μm, the membrane 63 displaces a liquid volume V of approximately 0.13 mm ^.

Further exemplary embodiments result from the fact that the stripline lines 61 are wound spirally or that the stripline lines 61 extend over several layers of the multilayer body 12.

FIG. 7 shows contacting concepts with the aid of which the changes in length of the stripline lines 61 can be achieved. According to FIG. 7A, the stripline lines 61 are connected directly to the electrically conductive fluid band 4. According to FIG. 7B, the stripline lines 61 are connected to the fluid band via transverse webs 66. According to FIG. 7C, the length of the stripline lines is varied via separate resonators 67 (with MEMS switches).

By changing the length of the stripline lines, the resonators from which a bandpass filter is built are tuned. By changing the length by about 10 mm, a large tuning range of the spectral transmission from 1 to 6 GHz is achieved. The calculated transmission spectra can be seen in FIG. 8. The resonator length was varied from left to right as follows: 10 mm, 6 mm, 3 mm, 1.5 mm, 0.8 mm, 0.5 mm and 0.4 mm.

Claims

claims

1. substrate (1) with at least one tunable electrical component (2, 22), wherein - in a volume section (11) of the substrate (1) at least one cavity (3) is arranged, which partially with a continuous fluid band (4) Fluid is filled with a certain electrical property, so that a position of the fluid band (4) in the cavity (3) can be changed, and the fluid band (4) is arranged in the cavity (3) such that a change in the position of the fluid band (4) an electrical operating quantity of the electrical component (2, 22) can be changed in the cavity (3).

2. The substrate of claim 1, wherein the electrical component (2) is selected from the group of capacitor, inductance and / or electrical resistance.

3. Substrate according to claim 1 or 2, wherein the position of the fluid band in the cavity can be changed electrostatically, magnetohydrodynamically and / or piezoelectrically.

4. Substrate according to one of claims 1 to 3, wherein the cavity (3) by an electrode (21) of the electrical component (2) is limited.

5. Substrate according to one of claims 1 to 4, wherein the cavity is closed.

6. Substrate according to one of claims 1 to 5, wherein the substrate is a multilayer substrate (12) and the cavity (4) is formed by a recess in the thickness direction of at least one layer (14) of the multilayer substrate.

7. The substrate of claim 6, wherein the multilayer substrate is an HTCC substrate or an LTCC substrate.

8. Use of the tunable electrical component of the substrate according to one of claims 1 to 7 for digital control of an operating frequency of a microwave oscillator.

9. Use of the tunable electrical component of the substrate according to one of claims 1 to 7 for controlling a pass and / or blocking behavior of a frequency filter.

10. Use of the tunable electrical component of the substrate according to one of claims 1 to 7 for adapting at least two circuits.

11. Use of the tunable electrical component of the substrate according to one of claims 1 to 7 for setting a frequency range of a mobile radio telephone used for transmitting and / or receiving electromagnetic waves.