Frequency agile duplex filter
View Patent ↗Systems and methods are disclosed for an electronically adjustable signal filter system, which comprises, in some embodiments, a first filter coupled to an antenna coupling network and a second filter, a power amplifier coupled to the first filter, an antenna connected to an antenna coupling network, a pilot tone generator coupled to the first filter, and a first signal source connected to the power amplifier and first filter. In some embodiments, the power amplifier amplifies the first signal, the first filter places a notch into the first signal transmitted to the antenna coupling network, the antenna coupling network combines the first signal and a second signal received from the antenna and transmits a third signal to the second filter.
1. A method of processing signals in wireless communications equipment, the method comprising:
notch filtering an input transmit signal to reduce signal power in at least one receive frequency band to provide a filtered transmit signal, wherein notch filtering the input transmit signal comprises tuning a reject band of the notch filtering based on a pilot signal;
coupling the filtered transmit signal to an antenna via an antenna coupling network for transmission by the antenna;
coupling a receive signal from the antenna to the antenna coupling network; and
notch filtering the receive signal to reduce power in a transmit frequency band to provide a filtered receive signal.
2. A method as defined in claim 1 , wherein the step of notch filtering the input transmit signal comprises:
amplifying the input transmit signal to provide an amplified transmit signal; and
notch filtering the amplified input transmit signal to provide the filtered transmit signal.
3. A method as defined in claim 2 , wherein the step of notch filtering the input transmit signal comprises using vector cancellation to suppress receive band noise.
4. A method as defined in claim 3 , further comprising isolating the vector cancellation from the input transmit signal.
5. A method as defined in claim 1 , wherein the step of notch filtering the receive signal comprises:
selecting a transmit frequency band from a plurality of transmit frequency bands; and
notch filtering the receive signal to reduce power in the selected frequency band to provide the filtered receive signal.
6. A method as defined in claim 1 , wherein the step of notch filtering the input transmit signal comprises reducing signal power in multiple receive frequency bands.
7. A method as defined in claim 1 , further comprising amplifying the filtered receive signal with a low noise amplifier to provide an amplified receive signal.
8. A method as defined in claim 7 , further comprising down converting the amplified receive signal to provide a down-converted receive signal.
9. A method as defined in claim 1 , further comprising down converting the amplified receive signal to provide a down-converted receive signal in a mixer tuned to the pilot signal.
10. A method as defined in claim 1 , wherein the antenna coupling network comprises at least one circulator operable:
to couple the filtered transmit signal from a transmit signal path to the antenna for transmission by the antenna; and
to couple the receive signal from the antenna to a receive signal path.
11. A method as defined in claim 10 , further comprising:
estimating a portion of the filtered transmit signal coupled to the receive signal path by the circulator; and
at least partially cancelling the portion of the filtered transmit signal coupled to the receive signal path.
12. The method of claim 1 , wherein the pilot signal is provided by a local oscillator.
13. The method of claim 9 , wherein the pilot signal is provided by a local oscillator.
14. The method of claim 5 , wherein the step of notch filtering the input transmit signal comprises tuning a reject band of the notch filtering based on a pilot signal.
15. The method of claim 6 , wherein the step of notch filtering the receive signal comprises:
selecting a transmit frequency band from a plurality of transmit frequency bands; and
notch filtering the receive signal to reduce power in the selected frequency band to provide the filtered receive signal.
16. The method of claim 15 , further comprising amplifying the filtered receive signal with a low noise amplifier to provide an amplified receive signal.
17. The method of claim 10 , wherein the step of notch filtering the input transmit signal comprises tuning a reject band of the notch filtering based on a pilot signal.
18. The method of claim 17 , wherein the pilot signal is provided by a local oscillator.
19. The method of claim 18 , further comprising:
estimating a portion of the filtered transmit signal coupled to the receive signal path by the circulator; and
at least partially cancelling the portion of the filtered transmit signal coupled to the receive signal path.
20. The method of claim 1 , further comprising cancelling an antenna reflection based in part on a transmit error signal.