Communications receiver using multi-band transmit blocking filters
Communications receivers and devices are disclosed. A communications receiver includes a low noise amplifier; a multi-band transmit blocking filter having a first port connected to an output of the low noise amplifier, and an RF analog-to-digital converter having an input connected to a second port of the multi-band transmit blocking filter. The multi-band transmit filter passes the receive frequencies of a group of two or more LTE bands, where a first receive frequency range of a first band in the group and a second receive frequency range of a second band in the group are disjoint and not subsets of a receive frequency range of a third band in the group, and attenuates the transmit frequencies of at least some bands in the group by at least twenty dB.
1. A dual-passband filter having a first passband, a second passband higher in frequency than the first passband, a first stopband lower in frequency than the first passband, and a second stopband between the first and second passbands, the dual pass-band filter comprising:
a first surface acoustic wave (SAW) band-pass filter in parallel with a second SAW band-pass filter, wherein:
the first SAW band-pass filter passes the first passband,
the second SAW band-pass filter passes the second passband, and
the second stop band attenuates, by at least 20 dB, transmit frequencies of at least one LTE band.
2. The dual-passband filter of claim 1 , wherein
a relative phase of the transfer functions of the first and second SAW band-pass filters is controlled such that an insertion loss of the dual-passband filter is greater than insertion losses of both the first and second SAW band-pass filters in isolation for at least one frequency in the at least one of the first and second stop bands.
3. The dual-passband filter of claim 1 , wherein
the first passband includes receive frequencies of at least a first LTE band;
the second passband includes receive frequencies of at least a second LTE band; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of the first and second LTE bands.
4. The dual-passband filter of claim 3 , wherein
the first SAW band-pass filter is configured to pass receive frequencies of LTE band 30;
the second SAW band-pass filter is configured to pass receive frequencies of LTE band 7; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of LTE bands 7 and 30.
5. The dual-passband filter of claim 1 , wherein
the first passband includes receive frequencies of two or more first LTE bands;
the second passband includes receive frequencies of at least one second LTE bands; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of all of the first and second LTE bands.
6. The dual-passband filter of claim 5 , wherein
the first SAW band-pass filter is configured to pass receive frequencies of LTE bands 20, 28A, 28B, and 68;
the second SAW band-pass filter is configured to pass receive frequencies of LTE band 8; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of LTE bands 8, 20, 28A, 28B, and 68.
7. The dual-passband filter of claim 1 , wherein
the first passband includes receive frequencies of two or more first LTE bands;
the second passband includes receive frequencies of two or more second LTE bands; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of all of the first and second LTE bands.
8. The dual-passband filter of claim 7 , wherein
the first SAW band-pass filter is configured to pass receive frequencies of LTE bands 12, 13, 14, and 17;
the second SAW band-pass filter is configured to pass receive frequencies of LTE bands 5, 6, 18, 19, and 26; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of LTE bands 5, 6, 12, 13, 14, 17, 18, 19, and 26.
9. The dual-passband filter of claim 7 , wherein
the first SAW band-pass filter is configured to pass receive frequencies of LTE bands 3 and 9;
the second SAW band-pass filter is configured to pass receive frequencies of LTE bands 1, 4, 10, 23, 65, and 66; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of LTE bands 1, 3, 4, 9, 10, 23, 65, and 66.
10. A communications receiver comprising:
a low noise amplifier;
a dual-passband filter having a first port connected to an output of the low noise amplifier; and
an RF analog-to-digital converter having an input connected to a second port of the dual-passband filter, wherein
the dual-passband filter has a first passband, a second passband higher in frequency than the first passband, a first stopband lower in frequency than the first passband, and a second stopband between the first and second passbands, and
the dual pass-band filter comprises:
a first surface acoustic wave (SAW) band-pass filter in parallel with a second SAW band-pass filter, the first SAW band-pass filter passing the first passband and the second SAW band-pass filter passing the second passband.
11. The communications receiver of claim 10 , wherein
a relative phase of the transfer functions of the first and second SAW band-pass filters in at least one of the first and second stop bands is controlled such that an insertion loss of the dual-passband filter is greater than insertion losses of both the first and second SAW band-pass filters in isolation for at least one frequency in the at least one of the first and second stop bands.
12. The communications receiver of claim 10 , wherein
the first passband includes receive frequencies of at least a first LTE band;
the second passband includes receive frequencies of at least a second LTE band; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of the first and second LTE bands.
13. The communications receiver of claim 12 , wherein
the first SAW band-pass filter is configured to pass receive frequencies of LTE band 30;
the second SAW band-pass filter is configured to pass receive frequencies of LTE band 7; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of LTE bands 7 and 30.
14. The communications receiver of claim 10 , wherein
the first passband includes receive frequencies of two or more first LTE bands;
the second passband includes receive frequencies of at least one second LTE bands; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of all of the first and second LTE bands.
15. The communications receiver of claim 14 , wherein
the first SAW band-pass filter is configured to pass receive frequencies of LTE bands 20, 28A, 28B, and 68;
the second SAW band-pass filter is configured to pass receive frequencies of LTE band 8; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of LTE bands 8, 20, 28A, 28B, and 68.
16. The communications receiver of claim 10 , wherein
the first passband includes receive frequencies of two or more first LTE bands;
the second passband includes receive frequencies of two or more second LTE bands; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of all of the first and second LTE bands.
17. The communications receiver of claim 16 , wherein
the first SAW band-pass filter is configured to pass receive frequencies of LTE bands 12, 13, 14, and 17;
the second SAW band-pass filter is configured to pass receive frequencies of LTE bands 5, 6, 18, 19, and 26; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of LTE bands 5, 6, 12, 13, 14, 17, 18, 19, and 26.
18. The communications receiver of claim 16 , wherein
the first SAW band-pass filter is configured to pass receive frequencies of LTE bands 3 and 9;
the second SAW band-pass filter is configured to pass receive frequencies of LTE bands 1, 4, 10, 23, 65, and 66; and
the dual-passband filter is configured to attenuate, by at least twenty dB, transmit frequencies of LTE bands 1, 3, 4, 9, 10, 23, 65, and 66.