Configurable micro-acoustic RF filter
A configurable micro-acoustic RF filter comprises first and second filter subsections ( 140, 150 ) and at least one switch ( 160 ) to selectively bypass or activate the second filter subsection ( 150 ). The filter sections include at least one serially connected and at least one shunt connected micro-acoustic resonator.
1. A configurable micro-acoustic RF filter, comprising:
a first port and a second port;
a first filter subsection including at least one serially connected micro-acoustic resonator and at least one shunt connected micro-acoustic resonator, the first filter subsection coupled to the first port;
a switch having a first terminal connected to the first filter subsection, a second terminal and a third terminal;
a second filter subsection including at least one serially connected micro-acoustic resonator and at least one shunt connected micro-acoustic resonator, the second filter subsection coupled to the third terminal of the switch and to the second port; and
an additional switch having a first terminal coupled to the second port, a second terminal coupled to the second terminal of the switch, and a third terminal coupled to the second filter subsection.
2. The configurable micro-acoustic RF filter according to claim 1 , further comprising a third port connected to the second terminal of the switch.
3. The configurable micro-acoustic RF filter according to claim 1 , further comprising a shunt connected inductance coupled to the third terminal of the switch.
4. The configurable micro-acoustic RF filter according to claim 3 , the shunt connected inductance configured to compensate a parasitic capacitance of the switch or to improve matching of the RF filter.
5. The configurable micro-acoustic RF filter according to claim 3 , the inductance having an inductance value L of L=1/(ω2*2Cp) or of L=1/(ω2*2Cp)±20%, wherein co represents an angular frequency at which compensation is to be applied or matching of the RF filter is achieved and 2 Cp represents a capacitance value of a parasitic capacitance of the switch.
6. The configurable micro-acoustic RF filter according to claim 1 , further comprising a shunt connected inductance coupled to the third terminal of the additional switch and configured to compensate for a parasitic capacitance of the additional switch relative to ground potential.
7. The configurable micro-acoustic RF filter according to claim 1 , the first and second filter subsections each having a first and a second terminal and each being symmetrical with respect to the first and second terminals.
8. The configurable micro-acoustic RF filter according to claim 1 , wherein the first and second filter subsections each comprise a TEE-configuration comprising:
the serially connected micro-acoustic resonator having a terminal;
the shunt connected micro-acoustic resonator coupled between the terminal of the serially connected micro-acoustic resonator and a terminal for ground potential; and
another serially connected micro-acoustic resonator connected to the terminal of the serially connected micro-acoustic resonator.
9. The configurable micro-acoustic RF filter according to claim 1 , wherein the first and second filter subsections each comprise a PI-configuration comprising:
the serially connected micro-acoustic resonator having a first terminal and a second terminal;
the shunt connected micro-acoustic resonator coupled between the first terminal of the serially connected micro-acoustic resonator and a terminal for ground potential; and
another shunt connected micro-acoustic resonator coupled between the second terminal of the serially connected micro-acoustic resonator and the terminal for ground potential.
10. The configurable micro-acoustic RF filter according to claim 9 , wherein the shunt connected micro-acoustic resonator or the second shunt connected micro-acoustic resonator are configured with reduced capacitance to compensate a parasitic capacitance of the switch or the additional switch.
11. The configurable micro-acoustic RF filter according to claim 1 , further cascading one or more additional filter subsections through one or more additional switches between the first filter subsection and the additional switch.
12. The configurable micro-acoustic RF filter according to claim 1 , further comprising a third switch, a fourth switch and a third filter subsection, the third switch having a first terminal coupled to the second filter subsection, a second terminal and a third terminal, the third terminal coupled to the third filter subsection, the fourth switch having a first terminal coupled to the third terminal of the additional switch, a second terminal coupled to the second terminal of the third switch and a third terminal coupled to the third filter subsection.
13. The configurable micro-acoustic RF filter according to claim 1 , wherein the configurable micro-acoustic RF filter is part of a communication device, the communication device comprising a detector configured to detect an interferer in a stopband region of the RF filter and configured to generate a detection signal indicating one of presence and absence of the interferer, setting switches of the RF filter in dependence on the detection signal.
14. A configurable micro-acoustic RF filter, comprising:
a first port and a second port;
a first filter subsection including at least one serially connected micro-acoustic resonator and at least one shunt connected micro-acoustic resonator, the first filter subsection coupled to the first port;
a switch having a first terminal connected to the first filter subsection, a second terminal and a third terminal; and
a second filter subsection including at least one serially connected micro-acoustic resonator and at least one shunt connected micro-acoustic resonator, the second filter subsection coupled to the third terminal of the switch and to the second port; and
an impedance element connected between the at least one shunt connected micro-acoustic resonator and the terminal for ground potential;
wherein the first and second filter subsections comprise a TEE-configuration comprising:
the serially connected micro-acoustic resonator having a terminal;
the at least one shunt connected micro-acoustic resonator coupled between the terminal of the serially connected micro-acoustic resonator and a terminal for ground potential; and
another serially connected micro-acoustic resonator connected to the terminal of the serially connected micro-acoustic resonator.
15. A configurable micro-acoustic RF filter, comprising:
a first port and a second port;
a first filter subsection including at least one serially connected micro-acoustic resonator and a first shunt connected micro-acoustic resonator, the first filter subsection coupled to the first port;
a switch having a first terminal connected to the first filter subsection, a second terminal and a third terminal;
a second filter subsection including at least one serially connected micro-acoustic resonator and a second shunt connected micro-acoustic resonator, the second filter subsection coupled to the third terminal of the switch and to the second port; and
an impedance element connected between the first shunt connected micro-acoustic resonator and the terminal for ground potential; and
an additional impedance element connected between the second shunt connected micro-acoustic resonator and the terminal for ground potential;
wherein the first and second filter subsections each comprise a PI-configuration, with the PI-configuration comprising:
the serially connected micro-acoustic resonator having a first terminal and a second terminal;
the shunt connected micro-acoustic resonator coupled between the first terminal of the serially connected micro-acoustic resonator and a terminal for ground potential; and
another shunt connected micro-acoustic resonator coupled between the second terminal of the serially connected micro-acoustic resonator and the terminal for ground potential.