Transmitter filter arrangement for multiband mobile phone
View Patent ↗A filter arrangement for use in a multiband dual-mode mobile phone. In particular, the mobile phone is operable in a W-CDMA mode and a band-reject filter comprising at least a series and a shunt acoustic-wave resonators is used to create a deep notch at the receive frequency band. The band-reject filter further includes a plurality of inductive elements for matching static capacitance of the resonators at the passband frequency. The mobile phone is also operable in 1800 and 1900 GSM bands. The band-reject filter is operatively connected to a harmonic trap in order to eliminate the third harmonic of these GSM bands. The mobile phone is also operable in the lower GSM band, for which a harmonic filter can share an antenna path with the band-reject filter.
1. A method of filtering transceiver signals in a mobile terminal, the mobile terminal operable in at least one transmit frequency band and one receive frequency band separated from the transmit frequency band, wherein the mobile terminal has a signal source for providing transmit signal in the transmit frequency band, said method comprising the steps of:
providing a signal path between the signal source and an antenna; and
providing a band-reject filter in the signal path so as to attenuate signal in the receive frequency band, wherein the band-reject filter comprises:
at least one series resonator operatively connected between the signal source and the antenna, the series resonator having a first end and an opposing second end, with the first end connected to the signal source;
at least one shunt resonator connecting between the second end of the series resonator and a grounding point, the shunt resonator and the series resonator forming an L-section; and
at least one inductor connected in parallel with the L-section.
2. The method of claim 1 , wherein the transmit frequency band substantially occupies a frequency range of 1920 to 1980 MHz, and the receive frequency band substantially occupies a frequency range of 2110 to 2170 MHz.
3. The method of claim 2 , wherein the mobile terminal operates in a code-division multiple access (CDMA) mode.
4. The method claim 3 , wherein the further transmit frequency band substantially occupies a frequency range of 1710 to 1770 MHz.
5. The method of claim 3 , wherein the further transmit frequency band substantially occupies a frequency range of 1710 to 1785 MHz.
6. The method of claim 3 , wherein the further transmit frequency band substantially occupies a frequency range of 1850 to 1910 MHz.
7. The method of claim 3 , wherein the mobile terminal is operable in a code division multiple access (CDMA) mode in said at least one transmit frequency band and one receive frequency band, and also operable in a GSM mode in said further transmit frequency band.
8. The method of claim 7 , further comprising the step of
providing a harmonic trap, operatively connected to the band-reject filter, for attenuating a harmonic of the GSM mode.
9. The method of claim 1 , wherein the mobile terminal is also operable in a further transmit frequency band, the mobile terminal further having a further signal source for providing a further transmit signal in the further transmit frequency band, said method further comprising the step of
operatively connecting the further signal source to the signal path at the first end of the series resonator.
10. The method of claim 1 , wherein the series resonator comprises an acoustic wave resonator and the shunt resonator comprises another acoustic wave resonator.
11. The method of claim 1 , wherein the series resonator comprises a bulk acoustic wave resonator and the shunt resonator comprises another bulk acoustic wave resonator.
12. A band-reject filter for use in a mobile terminal, the mobile terminal operable in at least one transmit frequency band and one receive frequency band separated from the transmit frequency band, wherein the mobile terminal has a signal source for providing transmit signal in the transmit frequency band, and a signal path between the signal source and an antenna, said filter comprising:
at least one series resonator operatively connected to the signal path between the signal source and the antenna, the series resonator having a first end and an opposing second end, with the first end connected to the signal source;
at least one shunt resonator connecting between the second end of the series resonator and a grounding point, the shunt resonator and the series resonator forming an L-section; and
at least one inductor connected in parallel with the L-section.
13. The filter of claim 12 , wherein said at least one inductor is connected between the first end of the series resonator and the grounding point, said band-reject filter further comprising
a further inductor connected between the second end of the series resonator and the grounding point.
14. The filter of claim 12 , wherein the series resonator comprises an acoustic wave resonator and the shunt resonator comprises another acoustic wave resonator.
15. The filter of claim 12 , wherein the series resonator comprises a bulk acoustic wave resonator and the shunt resonator comprises another bulk acoustic wave resonator.
16. The filter of claim 12 , wherein the transmit frequency band substantially occupies a frequency range of 1920 to 1980 MHz, and the receive frequency band substantially occupies a frequency range of 2110 to 2170 MHz.
17. A mobile terminal operable in at least one transmit frequency band and one receive frequency band separated from the transmit frequency band, said mobile terminal comprising:
a signal source for providing transmit signal in the transmit frequency band;
a signal path between the signal source and an antenna; and
a band-reject filter operatively connected to the signal path so as to attenuate signal in the receive frequency band, wherein the band-reject filter comprises:
at least one series resonator operatively connected between the signal source and the antenna, the series resonator having a first end and an opposing second end, with the first end connected to the transmission source;
at least one shunt resonator connecting between the second end of the series resonator and a reference point, the shunt resonator and the series resonator forming an L-section; and
at least one inductance connected in parallel with the L-section.
18. The mobile terminal of claim 17 , wherein the transmit frequency band substantially occupies a frequency range of 1920 to 1980 MHz, and the receive frequency band substantially occupies a frequency range of 2110 to 2170 MHz.
19. The mobile terminal of claim 18 , wherein said transmit signal comprises a code division multiple access (CDMA) signal.
20. The mobile terminal of claim 18 , further operable in a GSM900 transmit band, said mobile terminal further comprising
a further signal source, operatively connecting to the antenna, for providing a further transmit signal in the GSM900 transmit band.
21. The mobile terminal of claim 17 , also operable in a further transmit frequency band, said mobile terminal further comprising:
a further signal source, operatively connecting to the signal path at the first end of the series resonator, for providing a further transmit signal in the further transmit frequency band.
22. The mobile terminal of claim 21 , wherein the further transmit frequency band substantially occupies a frequency range of 1710 to 1770 MHz.
23. The mobile terminal of claim 21 , wherein the further transmit frequency band substantially occupies a frequency range of 1710 to 1785 MHz.
24. The mobile terminal of claim 21 , wherein the further transmit frequency band substantially occupies a frequency range of 1850 to 1910 MHz.
25. The mobile terminal of claim 21 , wherein the transmit signal comprises a code division multiple access (CDMA) signal, and the further transmit signal comprises a GSM signal.
26. The mobile terminal of claim 25 , further comprising a harmonic trap, operatively connected to the band-reject filter, for attenuating a harmonic of the GSM signal.
27. The mobile terminal of claim 26 , wherein the harmonic trap is connected to the band-reject filter through a diode which is unbiased when the mobile terminal is in the CDMA mode for transmitting the CDMA signal.
28. The mobile terminal of claim 17 , wherein the series resonator comprises an acoustic wave resonator and the shunt resonator comprises another acoustic wave resonator.
29. The mobile terminal of claim 17 , wherein the series resonator comprises a bulk acoustic wave resonator and the shunt resonator comprises another bulk acoustic wave resonator.