Frequency shunt
View Patent ↗A frequency separating unit includes an antenna unit, a first signal path, a second signal path, first band-pass filter in the first signal path, a second band-pass filter in the second signal path, and a matching circuit between the antenna unit and the second band-pass filter in the second signal path. The matching circuit includes a shunt arm to ground that includes a first impedance component, and a parallel circuit that includes an acoustic wave resonator and a second impedance component. The matching circuit is configured to operate as a phase shifter and to produce a substantially open circuit at an input of the second filter in a pass band of the first band-pass filter.
1. A frequency separating unit comprising:
an antenna unit;
a first signal path;
a second signal path;
a first band-pass filter in the first signal path;
a second band-pass filter in the second signal path;
a matching circuit between the antenna unit and the second band-pass filter in the second signal path,
wherein the matching circuit comprises:
a shunt arm to ground that comprises a first impedance component; and
a parallel circuit comprising an acoustic wave resonator and a second impedance component;
wherein the matching circuit is configured to operate as a phase shifter and to produce a substantially open circuit at an input of the second filter in a pass band of the band-pass filter.
2. The frequency separating unit of claim 1 , wherein the first impedance component comprises an inductor.
3. The frequency separating unit of claim 1 , wherein the first impedance component comprises a capacitor.
4. The frequency separating unit of claim 1 , wherein the first impedance component comprises an acoustic wave resonator.
5. The frequency separating unit of claim 1 , wherein the first impedance component comprises a parallel circuit comprised of an acoustic wave resonator and an inductor; and
wherein a resonance frequency of the parallel circuit corresponding to a pass-band frequency of the band-pass filter.
6. The frequency separating unit of claim 1 , wherein the second impedance component comprises an inductor.
7. The frequency separating unit of claim 1 , wherein the second impedance component comprises a capacitor.
8. The frequency separating unit of claim 1 , further comprising:
a third impedance component in the second signal path between a connection point of the shunt arm and the parallel circuit.
9. The frequency separating unit of claim 8 , wherein the third impedance component comprises an inductor or a capacitor.
10. The frequency separating unit of claim 1 , further comprising:
a fourth impedance component in the second signal path between the antenna connection and a connection point of the shunt arm.
11. The frequency separating unit of claim 10 , wherein the fourth impedance component comprises an inductor or a capacitor.
12. The frequency separating unit of claim 1 , wherein the first band-pass filter and/or second band-pass filter has a ladder-type structure comprised of series resonators in a signal path and parallel resonators in parallel branches; and
wherein each parallel branch comprises an impedance component between a parallel resonator and ground.
13. The frequency separating unit of claim 12 , wherein at least two different parallel branches are interconnected electrically via an impedance component.
14. The frequency separating unit of claim 1 , further comprising:
another impedance component in the first signal path before and/or after the first band-pass filter.
15. The frequency separating unit of claim 1 , further comprising:
another impedance component in the second signal path after the second filter.
16. The frequency separating unit of claim 1 , wherein a resonance frequency of a circuit comprised of the matching circuit corresponds to a pass-band frequency of the second band-pass filter.
17. The frequency separating unit of claim 1 , wherein the second signal path comprises a receive path and the first signal path comprises a transmit path.
18. The frequency separating unit of claim 1 , wherein the first impedance component is for diverting an overvoltage appearing on the antenna unit to ground.
19. The frequency separating unit of claim 1 , wherein the first band-pass filter and/or the second band-pass filter each comprises a balanced-unbalanced transformer.
20. The frequency separating unit of claim 1 , wherein the acoustic wave resonator comprises a thin-film acoustic wave resonator.
21. The frequency separating unit of claim 1 , wherein the acoustic wave resonator comprises at least one acoustic wave transducer.
22. The frequency separating unit of claim 17 , wherein the first band-pass filter works with bulk acoustic waves and the second band-pass filter works with surface acoustic waves.