Epcos Ag

Michael Unterberger

Edgar Schmidhammer

Pasi Tikka

Ralph Stömmer

Thomas Baier

The invention relates to a resonator operating with bulk acoustic waves (BAW resonator, BAW=Bulk Acoustic Wave) and band-pass filters constructed of such resonators. To increase the edge steepness of the transmission band of a BAW band-pass filter, the invention proposes reducing the effective coupling of a BAW resonator by using the connection in parallel of a BAW resonator and a capacitor instead of only one resonator. In addition, to increase the edge steepness of the transmission band, the use of a connection of coupled BAW resonators in the serial branch of a filter circuit with another resonator or resonator stack in the parallel branch of the filter circuit is proposed, the additional resonator or resonator stack being connected to the center electrode of the resonator stack specified initially.

Bulk acoustic wave resonator and circuit comprising same

A reactance filter, which is constructed from BAW resonators, has at least one basic element that has a first resonator in a first branch and a second resonator in a second branch. In one branch, there is situated a resonator having a greater ratio of dynamic to static capacitance than in the second branch, so that a filter is obtained having a resulting passband in which one edge is set steeper than the other edge. The selection of the edge that is to be set steeply takes place through the allocation of the first branch to the serial or to the parallel branch.

Reactance filter having an improved edge steepness

Proposed is a SAW HF filter with reactance elements, which is particularly suitable for mobile radio. The filter is balanced on both sides, is electrically symmetric, and comprises a four-pole reactance series element, which can be formed from two two-pole pole reactance elements or from a four-pole reactance element, and a resonator. One bar of the respective reactance elements is connected to the input side of the filter, while the other bar is connected to the output side of the filter.

Surface wave filter comprising reactance elements

A component operating with bulk acoustic waves has two Bulk Acoustic Wave (BAW) resonators that are stacked and are acoustically coupled to one another, with a first resonator being connected to an asymmetric port, and a second resonator being connected to a symmetrical port. The acoustic coupling is provided by a partially permeable coupling layer system, which has an alternating sequence of at least two &#x3bb;/4 mirror layers with different acoustic impedance. The coupling layer system furthermore has a compensation layer, which has an approximate thickness of &#x3bb;/8. The compensation layer according to the invention makes it possible to match any discrepancy in the phase difference (which is caused by reflections on the mirror layers) from the predetermined 180&#xb0; between the connections of the symmetrical port to approximately 180&#xb0;.

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Unterhaching, Germany

Michael Unterberger