Saw filter with a large bandwidth
AssigneeSnapTrack, Inc.
InventorsThomas DENGLER, Thomas BAUER
Life of this patent
Estimating the term…
Abstract
A SAW filter arrangement (FA) with a large bandwidth is specified, wherein a first filter (F1) and a second filter (F2) are connected in parallel between a first node (K1) and a second node (K2). The first filter (F1) and the second filter (F2) are both SAW filter configurations that are configured as DMS filters and both comprise two DMS tracks each, connected in series (S11, S12; S21, S22). The two filters (F1, F2) have different center frequencies and create a common passband together. The filter arrangement may comprise a serial resonator (RS) and shunting coils (L1, L2).
Claims11
A filter arrangement with a large bandwidth,
- having one first and one second filter, which filters are connected to each other in parallel between a first and a second node of the filter arrangement,
- wherein both filters are configured as DMS filters and both comprise two DMS tracks each, connected in series,
- wherein the two filters have different center frequencies and together create a common passband.
The filter arrangement according to any of the preceding claims,
- wherein the DMS tracks of the two filters are connected to each other via two or more coupling converters,
- wherein the two coupling converters are arranged in phase opposition
- wherein earth connections of the two coupling converters are connected to each other but not to an external potential.
The filter arrangement according to any of the preceding claims,
- wherein the DMS tracks of the two filters are structured as metallizations on (a) lithium niobate substrate(s) and coated with a dielectric covering layer, which is positioned directly on top of the metallization.
The filter arrangement according to the preceding claim,
- wherein the dielectric covering layer has a temperature coefficient TCF that is lower than that of the substrate or is opposed to that of the substrate.
The filter arrangement according to any of the preceding claims,
- wherein the input converters and the output converters of a DMS track are coupled with the corresponding coupling converters of the same filter via parallel capacitances.
The filter arrangement according to the preceding claim,
- wherein the parallel capacitances are only provided for the filter that has the higher center frequency.
The filter arrangement according to any of the preceding claims,
- wherein, parallel to each of the two nodes of the filter arrangement, a coil is respectively connected to ground.
The filter arrangement according to any of the preceding claims,
- wherein the finger connection sequence in the two DMS tracks of the filter with the higher center frequency is selected such that, at least in one instance, two adjacent terminal converter fingers of different converters are potential-carrying converter fingers.
The filter arrangement according to any of the preceding claims,
- wherein the filter arrangement has a balanced port,
- wherein each of the two filters at the balanced port has two anti-phase output converters or one V-split converter, which comprises two partial converters that are arranged side by side in longitudinal direction and that are electrically connected to each other in parallel.
The use of the filter arrangement according to one of the preceding claims as receive filter for covering two adjacent bands and for simultaneous reception in the two bands within a Carrier Aggregation mode operation.
Dependencies are inferred from the claim text.