Tunable RF channel select filter
Methods and apparatus, including computer program products, are provided for RF filtering. Related apparatus, systems, methods, and articles are also described.
1. An apparatus comprising:
a first bandpass filter to receive a differential signal, wherein the first bandpass filter comprises a resistive-capacitive configuration of N-path filters tunable to a first center frequency;
a first notch filter to receive a first output of the first bandpass filter, wherein the first notch filter comprises a capacitive-resistive configuration of N-path filters tunable to a first notch center frequency;
a second bandpass filter to receive a second output of the first notch filter, wherein the second bandpass filter comprises a resistive-capacitive configuration of N-path filters tunable to the first center frequency;
a second notch filter to receive a third output of the second bandpass filter, wherein the second notch filter comprises a capacitive-resistive configuration of N-path filters tunable to a second notch center frequency; and
a third bandpass filter to receive a fourth output of the second notch filter and to provide a filtered output of the apparatus, wherein the third bandpass filter comprises a resistive-capacitive configuration of N-path filters tunable to the first center frequency.
2. The apparatus of claim 1 , wherein the first notch center frequency is offset in frequency at least one of above and below the first center frequency.
3. The apparatus of claim 1 , wherein the second notch center frequency is offset in frequency at least one of above and below the first center frequency.
4. The apparatus of claim 1 , wherein the first notch filter further includes a first feedforward transconductance amplifier and a second feedback transconductance amplifier configured to provide frequency shifting of the first notch center frequency.
5. The apparatus of claim 1 , wherein the second notch filter further includes a first feedforward transconductance amplifier and a second feedback transconductance amplifier configured to provide frequency shifting of the second notch center frequency.
6. The apparatus of claim 1 further comprising:
a first transconductance amplifier to amplify the first output provided to the first bandpass filter.
7. The apparatus of claim 1 further comprising:
a second transconductance amplifier to amplify the second output provided by the first notch filter.
8. The apparatus of claim 1 further comprising:
a balun coupled to the first bandpass filter to provide the differential signal input to the first bandpass filter.
9. A method comprising:
receiving, at a first bandpass filter, a differential signal, wherein the first bandpass filter comprises a resistive-capacitive configuration of N-path filters tunable to a first center frequency;
receiving, at a first notch filter, a first output of the first bandpass filter, wherein the first notch filter comprises a capacitive-resistive configuration of N-path filters tunable to a first notch center frequency;
receiving, at a second bandpass filter, a second output of the first notch filter, wherein the second bandpass filter comprises a resistive-capacitive configuration of N-path filters tunable to the first center frequency;
receiving, at a second notch filter, a third output of the second bandpass filter, wherein the second notch filter comprises a capacitive-resistive configuration of N-path filters tunable to a second notch center frequency;
receiving, at a third bandpass filter, a fourth output of the second notch filter, wherein the third bandpass filter comprises a resistive-capacitive configuration of N-path filters tunable to the first center frequency; and
outputting, by the third bandpass filter, a filtered output.
10. The method of claim 9 , wherein the first notch center frequency is offset in frequency at least one of above and below the first center frequency.
11. The method of claim 9 , wherein the second notch center frequency is offset in frequency at least one of above and below the first center frequency.
12. The method of claim 9 , wherein the first notch filter further includes a first feedforward transconductance amplifier and a second feedback transconductance amplifier configured to provide frequency shifting of the first notch center frequency.
13. The method of claim 9 , wherein the second notch filter further includes a first feedforward transconductance amplifier and a second feedback transconductance amplifier configured to provide frequency shifting of the second notch center frequency.
14. The method of claim 9 further comprising:
amplifying, by a first transconductance amplifier, the first output provided to the first bandpass filter.
15. The method of claim 9 further comprising:
amplifying, by a second transconductance amplifier, the second output provided by the first notch filter.
16. The method of claim 9 , wherein a balun provides the differential signal to the first bandpass filter.
17. A non-transitory computer-readable storage medium including computer program code which when executed by at least one processor causes operations comprising:
receiving, at a first bandpass filter, a differential signal, wherein the first bandpass filter comprises a resistive-capacitive configuration of N-path filters tunable to a first center frequency;
receiving, at a first notch filter, a first output of the first bandpass filter, wherein the first notch filter comprises a capacitive-resistive configuration of N-path filters tunable to a first notch center frequency;
receiving, at a second bandpass filter, a second output of the first notch filter, wherein the second bandpass filter comprises a resistive-capacitive configuration of N-path filters tunable to the first center frequency;
receiving, at a second notch filter, a third output of the second bandpass filter, wherein the second notch filter comprises a capacitive-resistive configuration of N-path filters tunable to a second notch center frequency;
receiving, at a third bandpass filter, a fourth output of the second notch filter, wherein the third bandpass filter comprises a resistive-capacitive configuration of N-path filters tunable to the first center frequency; and
outputting, by the third bandpass filter, a filtered output.