Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2001-10-01
2004-05-11
Budd, Mark (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S31300R
Reexamination Certificate
active
06734600
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a component which is suitable for high-frequency applications.
High-frequency application technology makes use, on the one hand, of grounded signals, which are usually referred to in the pertinent technical literature as single ended, and on the other hand of differential signals, which are usually referred to in the pertinent technical literature as balanced signals, are used. Grounded signals are sensitive to fluctuations of the ground potential. By contrast, differential signals, which are preferably symmetrical to the ground potential, are insensitive to shifts of the ground potential.
In certain high-frequency applications, for example between an antenna and a first amplifier stage of a mobile communication device, grounded signals are used, subsequently filtered and converted into differential signals. Impedance matching is often additionally required.
Resonators which have a piezoelectric layer arranged between two electrodes are often used as filters for high-frequency signals (see for example K. M. Lakin et al., IEEE MTT-S International 1995, pages 883-86; K. M. Lakin et al., IEEE Trans. Microwave Theory Techn., Vol. 41, No. 12, 1993, pages 2139-46; and W. W. Lau et al., 1996 IEEE Int. Frequency Control Symp., pages 558-62). If the high-frequency signal is applied to the two electrodes, a mechanical oscillation is induced in the piezoelectric layer. For a wavelength which corresponds to twice the thickness of the piezoelectric layer, a standing wave forms. The frequency selectivity of the impedance of such a resonator can be used for the filtering of signals.
Different types of such resonators have been proposed (see K. M. Lakin et al., IEEE MTT-S International 1995, pages 883-86). On the one hand, the resonator is fastened on a support only at the edge, while the active resonator part is arranged on the surface of a membrane above a cavity. It has also been proposed to isolate the active resonator part by an air gap from a substrate, to which the resonator is fastened at the edge. Finally, it has been proposed to arrange the resonator above a series of layers which reflects the wavelength amplified by the resonator. In that case, the resonator is connected to the substrate over its full width. The series of layers has a plurality of &lgr;/4 layers and acts as an acoustic mirror. The space requirement of these resonators is typically 200 &mgr;m×200 &mgr;m.
These resonators have two electrodes, that is to say they are one-port assemblies, often referred to in the pertinent technical literature as one-port devices.
A two-port assembly is disclosed in K. M. Lakin et al., IEEE Trans. Microwave Theory Techn., Vol. 41, No. 12, 1993, pages 2139-46, with a piezoelectric layer arranged between two electrodes on each of both sides of a substrate. A further two-port assembly of a resonator has two filters stacked one above the other on a substrate. For this purpose, on the substrate there is provided a floating electrode, on that a first piezoelectric layer, on that a grounded electrode, on that a second piezoelectric layer and on that two electrodes arranged alongside each other. That arrangement has a high insertion loss, although stacked filters as a one-port assembly have a high stop-band attenuation. Owing to the two piezoelectric layers required in the two-port assemblies, they entail increased expenditure in comparison with the one-port assemblies.
Another possibility for filtering high-frequency signals is the use of surface-acoustic-wave filters, wherein two electrodes are arranged on the surface of a substrate of piezoelectric material (quartz, lithium niobate). These electrodes are used to induce surface acoustic waves, which propagate in the surface of the substrate. Customary dimensions of surface-acoustic-wave filters are 2×3 mm
2
.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a component, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which is suitable for high-frequency applications and which can be implemented as a multi-port assembly with a small surface area requirement and low expenditure.
With the foregoing and other objects in view there is provided, in accordance with the invention, a component for forming vertically standing waves of a wavelength &lgr;, comprising:
a piezoelectric layer having a first main surface, a second main surface opposite the first main surface, and a thickness of substantially &lgr;/2 or an integral multiple of &lgr;/2;
a first pair of electrodes including a first lower electrode and a first upper electrode, and a second pair of electrodes including a second lower electrode and a second upper electrode;
the first upper electrode and the second upper electrode being formed on the first main surface of the piezoelectric layer, and the first lower electrode and the second lower electrode being formed on the second main surface of the piezoelectric layer;
the first upper electrode, the second upper electrode, the first lower electrode, and the second lower electrode each being structured such that structures of the first upper electrode and of the second upper electrode engage in one another and structures of the first lower electrode and of the second lower electrode engage in one another.
In other words, the component has a piezoelectric layer with a first pair of electrodes and a second pair of electrodes. The first pair of electrodes has a first lower electrode and a first upper electrode. The second pair of electrodes has a second lower electrode and a second upper electrode. The first upper electrode and the second upper electrode are arranged on a first main area of the piezoelectric layer. The first lower electrode and the second lower electrode are arranged on a second main area of the piezoelectric layer, which lies opposite the first main area. The first upper electrode, the second upper electrode, the first lower electrode and the second lower electrode are in each case structured, the structures of the first upper electrode and the structures of the second upper electrode, and the structures of the first lower electrode and the structures of the second lower electrode respectively engaging in one another. In other words, structures of the first upper electrode and of the second upper electrode and of the first lower electrode and of the second lower electrode are respectively arranged alongside one another, preferably in an alternating manner.
If, for example, a high-frequency signal is applied to the first pair of electrodes, this causes a mechanical oscillation of the piezoelectric layer. The mechanical oscillation forms in the entire piezoelectric layer, including in the regions wherein the surface of the piezoelectric layer is not occupied by the respective electrode between neighboring structures of the first upper electrode or the first lower electrode. What is known as the inverse piezo effect causes this mechanical oscillation between the second lower electrode and the second upper electrode of the second pair of electrodes to generate a high-frequency signal.
The structures of the first upper electrode, of the second upper electrode, of the first lower electrode and of the second lower electrode are preferably so fine in one dimension that they have dimensions which are less than the wavelength of a mechanical oscillation which forms between the first upper electrode and the second upper electrode on the one hand and the first lower electrode and the second lower electrode on the other hand when a high-frequency signal is applied to the first pair of electrodes.
In accordance with an added feature of the invention, the structures of the first upper electrode, of the second upper electrode, of the first lower electrode and of the second lower electrode are so fine in one dimension that they have dimensions which are less than twice the spacing between the upper electrodes and the lower electrodes. This means that these d
Aigner Robert
Ella Juha
Budd Mark
Greenberg Laurence A.
Infineon - Technologies AG
Locher Ralph E.
Stemer Werner H.
LandOfFree
Component for forming vertically standing waves of a wavelength does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Component for forming vertically standing waves of a wavelength, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Component for forming vertically standing waves of a wavelength will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3231517