Filter device comprising two connected filter circuits
A filter device having a reduced sensitivity to production tolerances comprises a multilayer panel with integrated wiring, a piezoelectric substrate mounted to the panel. A first filter circuit (FC 1 ) and a signal path (SP) comprising a second filter circuit are realized on the substrate and connected to a common antenna terminal (AT) as well as to a common node (CN) located on top of the piezoelectric substrate. A first matching circuit (MC 1 ) and further matching circuits (MC 2 ) are realized by the wiring in the multilayer panel.
1. A filter device comprising:
a multilayer panel with wiring;
a piezoelectric substrate mounted to the multilayer panel;
a first filter circuit;
a signal path comprising a second filter circuit, wherein the first filter circuit and the second filter circuit are both filter circuits being realized on a top surface of the piezoelectric substrate and connected to a common antenna terminal on the piezoelectric substrate;
a first matching circuit having a first end connected to the common antenna terminal on the piezoelectric substrate and a second end connected to the signal path with the second filter circuit, the first matching circuit including the wiring in the multilayer panel; and
a common node to which the first filter circuit, the signal path and the common antenna terminal are connected to, the common node being a pad located on the top surface of the piezoelectric substrate.
2. The filter device of claim 1 ,
wherein the first matching circuit realized by the wiring in the multilayer panel is circuited in a series line between the signal path and the common node;
wherein a first series line section arranged on the piezoelectric substrate connects the common node and a first pad;
wherein a second series line section arranged on the piezoelectric substrate connects a second pad and the signal path comprising the second filter circuit;
wherein a first interconnection connects the first pad to a first end of the first matching circuit; and
wherein a second interconnection connects the second pad to a second end of the first matching circuit.
3. The filter device of claim 1 , wherein a second matching circuit is circuited between the common antenna terminal and the common node.
4. The filter device of claim 1 , wherein at least one of the first and second filter circuits comprises SAW resonators.
5. The filter device of claim 1 , the filter device being one of a Duplexer, a multiplexer or an extractor.
6. The filter device of claim 1 , wherein the first filter circuit is a band pass filter for global positioning system (GPS) frequencies and/or global navigation satellite system (GNSS) signals.
7. The filter device of claim 6 , wherein the signal path has a voltage standing wave ratio of less than 2 between 617 MHz and 4.2 GHz with except around the GPS/GNSS frequencies.
8. The filter device of claim 1 , wherein the multilayer panel comprises one of a laminate, a high temperature co-fired ceramic (HTCC) and a low temperature co-fired ceramic (LTCC).
9. The filter device of claim 1 ,
wherein a second matching circuit is circuited between the common antenna terminal and the common node,
wherein the second matching circuit comprises a series coil to match an antenna to the first filter circuit and to the signal path.
10. The filter device of claim 1 ,
wherein every interconnect between any pad on the piezoelectric substrate and a respective contact area on a surface of the multilayer panel comprises a bump, and
wherein an interconnect between the common antenna terminal and a respective pad on the piezoelectric substrate is located near a corner of the piezoelectric substrate.