Radio frequency systems with tunable filter
Radio frequency (RF) systems with tunable filters are provided herein. In certain embodiments, an RF system includes a first RF processing circuit configured to process a first frequency band of a first communication standard and a second frequency band of a second communication standard. The first frequency band and the second frequency band are close in frequency and/or partially overlapping in frequency. The first RF processing circuit includes a tunable filter for changing the bandwidth of the first RF processing circuit to enhance the robustness of the first RF processing circuit to blocker or jammer signals of a third frequency band.
1. A mobile device comprising:
a first antenna; and
a front end circuit electrically coupled to the first antenna and including a first radio frequency processing circuit implemented to support reception of a first frequency band of a first communication standard and a second frequency band of a second communication standard, the first radio frequency processing circuit including a tunable filter having adjustable bandwidth to control an amount of filtering provided to a blocker signal of a third frequency band, the tunable filter operates with a first bandwidth in a first mode and with a second bandwidth in a second mode, the first mode providing a higher amount of filtering to the blocker signal than the second mode, the tunable filter further includes a notch filter component that is activated in the first mode and deactivated in the second mode, the front end circuit further including a second radio frequency processing circuit configured to generate a transmit signal in the third frequency band.
2. The mobile device of claim 1 further comprising a second antenna configured to receive the transmit signal from the second radio frequency processing circuit, the blocker signal arising from antenna-to-antenna coupling between the first antenna and the second antenna.
3. The mobile device of claim 1 wherein the front end circuit further includes a diplexer configured to couple the first radio frequency processing circuit and the second radio frequency processing circuit to the first antenna, the blocker signal arising from a finite isolation of the diplexer.
4. The mobile device of claim 1 wherein the first bandwidth is narrower than the second bandwidth.
5. The mobile device of claim 1 wherein the tunable filter has higher insertion loss in the first mode relative to the second mode.
6. The mobile device of claim 1 wherein selection between the first mode and the second mode is controlled based on data received over a serial interface.
7. The mobile device of claim 1 wherein the third frequency band is of the second communication standard.
8. The mobile device of claim 1 wherein the first communication standard is long term evolution (LTE) and the second communication standard is fifth generation (5G).
9. The mobile device of claim 1 wherein the first frequency band is LTE B42, the second frequency band is 5G n77, and the third frequency band is 5G n79.
10. A mobile device comprising:
a first antenna; and
a front end circuit electrically coupled to the first antenna and including a first radio frequency processing circuit implemented to support reception of a first frequency band of a first communication standard and a second frequency band of a second communication standard, the first radio frequency processing circuit including a tunable filter having adjustable bandwidth to control an amount of filtering provided to a blocker signal of a third frequency band, the tunable filter operates with a first bandwidth in a first mode and with a second bandwidth in a second mode, the first mode providing a higher amount of filtering to the blocker signal than the second mode, the front end circuit further including a second radio frequency processing circuit configured to generate a transmit signal in the third frequency band, the front end circuit further includes a blocker detector configured to generate a detection signal based on detecting for the blocker signal, selection between the first mode and the second mode controlled based on the detection signal.
11. The mobile device of claim 10 wherein the blocker detector is implemented along a radio frequency signal path through the first radio frequency processing circuit.
12. The mobile device of claim 10 wherein the blocker detector is implemented along a radio frequency signal path through the second radio frequency processing circuit.
13. A mobile device comprising:
a first antenna; and
a front end circuit electrically coupled to the first antenna and including a first radio frequency processing circuit implemented to support reception of a first frequency band of a first communication standard and a second frequency band of a second communication standard, the first radio frequency processing circuit including a tunable filter having adjustable bandwidth to control an amount of filtering provided to a blocker signal of a third frequency band, the tunable filter operates with a first bandwidth in a first mode and with a second bandwidth in a second mode, the first mode providing a higher amount of filtering to the blocker signal than the second mode, the front end circuit further including a second radio frequency processing circuit configured to generate a transmit signal in the third frequency band, and selection between the first mode and the second mode is controlled based on whether the second radio frequency processing circuit is transmitting the transmit signal.
14. A front end system comprising:
a first radio frequency processing circuit implemented to support reception of a first frequency band of a first communication standard and a second frequency band of a second communication standard, the first radio frequency processing circuit including a tunable filter having adjustable bandwidth to control an amount of filtering provided to a blocker signal of a third frequency band, the tunable filter operates with a first bandwidth in a first mode and with a second bandwidth in a second mode, the first mode providing a higher amount of filtering to the blocker signal than the second mode, the tunable filter further includes a notch filter component that is activated in the first mode and deactivated in the second mode; and
a second radio frequency processing circuit configured to generate a transmit signal in the third frequency band.
15. The front end system of claim 14 wherein the first bandwidth is narrower than the second bandwidth.
16. The front end system of claim 14 wherein the tunable filter has higher insertion loss in the first mode relative to the second mode.
17. A method of radio frequency communication, the method comprising:
receiving a first signal and a second signal via an antenna, the first signal of a first frequency band of a first communication standard and the second signal of a second frequency band of a second communication standard;
processing the first signal and the second signal using a first radio frequency processing circuit;
transmitting a transmit signal in a third frequency band using a second radio frequency processing circuit; and
controlling an amount of filtering provided to a blocker signal of the third frequency band by adjusting a bandwidth of a tunable filter of the first radio frequency processing circuit, the tunable filter operates with a first bandwidth in a first mode and with a second bandwidth in a second mode, the first mode providing a higher amount of filtering to the blocker signal than the second mode, the tunable filter further includes a notch filter component that is activated in the first mode and deactivated in the second mode.
18. The method of claim 17 wherein the first bandwidth is narrower than the second bandwidth.
19. The method of claim 17 wherein the tunable filter has higher insertion loss in the first mode relative to the second mode.
20. The method of claim 17 wherein selection between the first mode and the second mode is controlled based on data received over a serial interface.