Multi-mode surface acoustic wave filter with impedance conversion
Aspects of this disclosure relate to an acoustic wave filter that includes a multi-mode surface acoustic wave filter and a ladder section. The multi-mode surface acoustic wave filter has a higher impedance at an output than at an input. The ladder section is connected to the output of the multi-mode surface acoustic wave filter. Related radio frequency systems, radio frequency modules, wireless communication devices, and methods are disclosed.
1. An acoustic wave filter comprising:
a multi-mode surface acoustic wave filter including an input that is single-ended and an output that is single-ended, the input including at least one more track than the output, and the multi-mode surface acoustic wave filter having a higher impedance at the output than at the input;
a ladder section connected to the output of the multi-mode surface acoustic wave filter, the ladder section including at least one shunt acoustic wave resonator and at least one series acoustic wave resonator; and
a shunt inductor, the ladder section coupled between the multi-mode surface acoustic wave filter and the shunt inductor, and the acoustic wave filter configured to filter a radio frequency signal.
2. The acoustic wave filter of claim 1 wherein the acoustic wave filter is configured as a receive filter.
3. An acoustic wave filter comprising:
a multi-mode surface acoustic wave filter including an input that is single-ended and an output that is single-ended, the input including at least one more track than the output, and the multi-mode surface acoustic wave filter having a higher impedance at the output than at the input;
a ladder section connected to the output of the multi-mode surface acoustic wave filter, the ladder section including at least one shunt acoustic wave resonator and at least one series acoustic wave resonator; and
a shunt inductor, the ladder section coupled between the multi-mode surface acoustic wave filter and the shunt inductor, the acoustic wave filter configured to filter a radio frequency signal, and the acoustic wave filter is configured as a transmit filter.
4. The acoustic wave filter of claim 1 wherein the multi-mode surface acoustic wave filter includes a plurality of interdigital transducer electrodes longitudinally coupled to each other.
5. The acoustic wave filter of claim 1 wherein the at least one more track is a single track.
6. The acoustic wave filter of claim 1 wherein the input has more interdigital transducer electrode fingers than the output.
7. The acoustic wave filter of claim 1 wherein the acoustic wave filter has a passband, and the output has an impedance of greater than 50 Ohms for the passband.
8. The acoustic wave filter of claim 1 wherein the at least one shunt acoustic wave resonator and the at least one series acoustic wave resonator are surface acoustic wave resonators.
9. A radio frequency system comprising:
a low noise amplifier; and
an acoustic wave filter including a multi-mode surface acoustic wave filter, a shunt inductor, and a ladder section coupled between the multi-mode surface acoustic wave filter and the shunt inductor; the ladder section being in a signal path between the multi-mode surface acoustic wave filter and an input of the low noise amplifier, the multi-mode surface acoustic wave filter including an input and an output, the input of the multi-mode surface acoustic wave filter having at least one more track than the output of the multi-mode surface acoustic wave filter, and the multi-mode surface acoustic wave filter having a higher impedance at the output than at the input.
10. The radio frequency system of claim 9 further comprising an antenna, the acoustic wave filter being in a signal path between the antenna and the low noise amplifier.
11. The radio frequency system of claim 9 comprising a multiplexer, the multiplexer including all receive filters, and the acoustic wave filter being one of the receive filters of the multiplexer.
12. The radio frequency system of claim 9 wherein the input is single-ended and the output is single-ended.
13. The radio frequency system of claim 9 wherein the input of the multi-mode surface acoustic wave filter has more interdigital transducer electrode fingers than the output of the multi-mode surface acoustic wave filter.
14. The radio frequency system of claim 9 wherein the output of the multi-mode surface acoustic wave filter has an impedance of greater than 50 Ohms.
15. A wireless communication device comprising:
the acoustic wave filter of claim 1 ;
an antenna operatively coupled to the acoustic wave filter;
a radio frequency amplifier operatively coupled to the acoustic wave filter and configured to amplify a radio frequency signal; and
a transceiver in communication with the radio frequency amplifier.
16. The wireless communication device of claim 15 wherein the radio frequency amplifier is a low noise amplifier having an input, and the ladder section is in a signal path between the multi-mode surface acoustic wave filter and the input of the low noise amplifier.
17. The wireless communication device of claim 15 wherein the at least one more track is a single track.
18. The wireless communication device of claim 15 wherein the input of the multi-mode surface acoustic wave filter has more interdigital transducer electrode fingers than the output of the multi-mode surface acoustic wave filter.
19. The wireless communication device of claim 15 wherein the output of the multi-mode surface acoustic wave filter has an impedance of greater than 50 Ohms.
20. The wireless communication device of claim 15 wherein the wireless communication device is a mobile phone.