Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2003-03-31
2004-03-02
Ponomarenko, Nicholas (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S309000
Reexamination Certificate
active
06700299
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an assembly of variable capacitance in accordance with the introductory clause of Patent claim 1, as well as to a method of setting a predeterminable capacitance by application of this assembly.
The principle field of application of the present invention is within the domain of high-frequency technology, particularly in applications in communication technology. In this field, there is an ever-increasing demand for settable high-frequency capacitance levels at a maximum of quality achievable. So far, semiconductor components, so-called varactors, have been used to this end, which, however, reach Q-factor levels between 20 and 40 at maximum. Specifically for the application in mobile telephony or cellular phones, however, Q-factors of at least 100 are desirable. These high Q-factors in a resonant circuit can be achieved, at present, only with the use of micro-mechanical capacitors.
PRIOR ART
Capacitors manufactured by micro-engineering means are mechanically mobile elements that permit a variation of the distance or the overlapping or coverage degree of two capacitor plates for setting different capacitance levels. When such mobile elements are used a reaction of the component to exterior accelerations cannot be completely precluded, however. To this adds that in the high-frequency range at the frequencies from 0.8 to 2 GHz, which are specifically employed in cellular telephones and with the intended low attenuation levels, mainly metal materials are used as basic material for the mobile elements. Their specific density is definitely higher than the density in silicon, for instance, so that the mass of the mobile element is additionally increased by these materials. Low driving voltage levels and the resulting low driving forces for the mobile elements, in combination with the desired positioning distances of several 10 &mgr;m, require comparatively soft suspending systems.
On the other hand, a settable capacitor for mobile application should be as stable as possible so that neither thermal nor mechanical influences from the outside cannot lead to a drift in capacitance. This resistance, particularly to accelerations, cannot be achieved with the afore-described properties of the known micro-mechanical assemblies.
The present invention is therefore based on the problem of providing an assembly of variable capacitance as well as a method of operating this assembly, which ensure a high stability of the respective capacitance set in resistance to outside influences.
BRIEF DESCRIPTION OF THE INVENTION
The problem of the invention is solved by the assembly according to claim 1 as well as by the method according to claim 18. Expedient embodiments of the assembly as well as of the method are the subject matters of the dependent Claims.
In the inventive assembly, the variable capacitance is constituted by a variable coverage or a variable distance of at least one first and one second electrically conductive region. In the context of the present patent application, the term “coverage” denotes an at least partial mutual overlapping or coverage of the two regions, seen in a viewing direction substantially orthogonal on or parallel to the surface of the substrate of the assembly.
The first electrically conductive region is configured here on or in the substrate while the second electrically conductive region is configured on or in an actuator element of a first micro-mechanical actuator. Both regions are preferably constituted by plane layers or plate-shaped elements and are substantially parallel to each other whenever the capacitance is set. However, this is not a definitely required prerequisite for the function of the assembly.
The first micro-mechanical actuator is so configured and disposed on the substrate that it is capable of performing a movement of the actuator element with the second region along the surface of the substrate at different positions relative to the first region, where the second region overlaps, at least partly, the first region. The first region is preferably disposed in or below the substrate surface and in parallel with the latter. The first region, however, may also extend in the form of a separate structure in a direction orthogonal on the substrate surface.
In the different positions which the actuator element may take, hence different distances and/or degrees of overlapping coverage prevail between the first and second regions, which gives rise to a different capacitance level. In accordance with the present invention, moreover holding means are provided on the substrate, which are capable of pulling or pushing the actuator element in the different positions towards the substrate or a mechanical stop on the substrate, and of holding it in this position. This holding function of the present assembly prevents a variation of the respective positions set and hence of the capacitance level set in the event of outside influences acting upon it.
The fixing of the actuator element relative to the substrate or the first region, respectively, can be ensured by both an electrostatic holding force and a further holding element producing a purely mechanical action upon the actuator element.
The holding means for the implementation of an electrostatic holding function can be achieved here in a very simple manner by the configuration of further electrically conductive regions on or in the actuator element and on or in the substrate, which are opposed to each other in the different positions to be set, so that the actuator element will be pulled towards the substrate surface due to the application of a differential voltage between these further electrically conductive regions. As a matter of fact, either an insulating layer must be configured over the additional electrically conductive region on the actuator element or on the substrate, or the respective regions are held by spacer or stops on the substrate or on the actuator element at a distance in order to avoid a short circuit. This applies also to the first and second electrically conductive regions that constitute the variable capacitance. These regions, too, must not come into direct contact with each other when the holding position is realised.
The holding means may also be implemented by a thermo-mechanical micro actuator. This micro actuator is so configured and disposed relative to the first micro-mechanical actuator that in response to a thermal excitation, it will be deflected in a substantially orthogonal direction on the surface of the substrate and that a first section of the actuator element of the first micro-mechanical actuator in the different positions to be set or that can be set up reaches up to a position underneath a second section of the thermo-mechanical actuator—if the latter is in a deflected state. When the thermo-mechanical actuator is switched off the actuator element of the first micro-mechanical actuator is then clamped between the first section of the thermo-mechanical actuator and the substrate. Due to this clamping effect, a holding function can be expediently implemented, which does not require that energy be supplied during the holding function. For release of this holding position, the thermo-mechanical actuator is, in its turn, heated so that it will expand or will be deflected, respectively, and hence releases again the first micro-mechanical actuator.
In addition, the respective sections of the two actuators, which are superimposed on each other, may present corresponding structures that permit a mutual engagement or mutual hooking at the respective holding positions. This ensures a particularly stable holding position.
The first micro-mechanical actuator may be configured, for instance, as electrostatic or thermo-mechanical actuator. With appropriate suitability, micro actuators operating on other driving principles can, equally be employed, of course. Electrostatic micro actuators are, however, particularly well suitable for the application in a network-independent device such as a cellular telephone, due to their low energy
Quenzer Hans-Joachim
Wagner Bernd
Wenk Beatrice
Breiner & Breiner L.L.C.
Fraunhofer-Gesellschaft zur Forderung der ange-wandten Forschung
Mohandesi Iraj A.
Ponomarenko Nicholas
LandOfFree
Assembly having variable capacitance does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Assembly having variable capacitance, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Assembly having variable capacitance will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3194986