Reactance filter having an improved edge steepness
AssigneeEpcos AG
InventorMichael Unterberger
Life of this patent
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Abstract
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.
Claims14
A reactance filter comprising at least one basic element having a first resonator in a first branch and a second resonator in a second branch, one of the branches being a serial branch and the other branch being a parallel branch, each resonator being of a BAW type having a specific ratio VC=C1/C0 of dynamic to static capacitance and the ratio VC for the resonator of the second branch being set smaller than the ratio VC for the resonator of the first branch.
A wireless communication system having a transmit part and a receiver part, each part having a reactance filter comprising at least one basic element having a first resonator in a first branch and a second resonator in a second branch, with one of the branches being a serial branch and the other branch being a parallel branch, each resonator being a BAW type having a specific ratio VC=C1/C0 of a dynamic to static capacitance and the ratio VC for the resonator of the second branch being set smaller than the ratio of the ratio VC for the resonator of the first branch, the filter for the transmit part having the second branch being a serial branch and the first branch being the parallel branch, so that the filter has a steeper right edge, and the filter for the receive part having the second branch being the parallel branch and the first branch being the serial branch, so that the filter has a steeper left edge.
A duplexer having two passband filters, each passband filter being a reactance filter comprising at least one basic element having a first resonator in a first branch and a second resonator in a second branch, one of the branches being a serial branch and the other branch being a parallel branch, each resonator being of a BAW type having a specific ratio VC═C1/C0 of a dynamic to static capacitance and the ratio VC for the resonator of the second branch being smaller than the ratio VC for the resonator of the first branch, one of the passband filters having a low center frequency and being a reactance filter, with the second branch being a serial branch and the first branch being a parallel branch, so that it has a steeper right edge and the other of the two passband filters having a high center frequency and being a reactive filter with the second branch being a parallel branch and the first branch being a serial branch, so that the other filter has a steeper left edge.
Dependencies are inferred from the claim text.