Filtering characteristic adjustments of weakly coupled tunable RF filters

1. An apparatus comprising:

a first RF filter structure comprising a first plurality of RF resonators and configured to adjust a first filtering characteristic of the first RF filter structure based on a first detected signal, wherein:

the first plurality of RF resonators comprises a a first resonator, a second resonator, and a third resonator;

during a first configuration of the first RF filter structure, the first resonator is coupled to the second resonator and the first resonator is not coupled to the third resonator;

during a second configuration of the first RF filter structure, the first resonator is coupled to the second resonator via the third resonator;

one of the first plurality of RF resonators is configured to provide a first sampled RF signal; and

RF detection circuitry configured to detect the first sampled RF signal to provide the first detected signal.

2. The apparatus of claim 1 wherein the first plurality of RF resonators comprises a first pair of weakly coupled RF resonators, which comprises the first resonator and the second resonator, such that each of the first pair of weakly coupled RF resonators comprises a corresponding resonating inductive element to form a first pair of resonating inductive elements, such that a magnetic coupling coefficient between each of the first pair of resonating inductive elements is less than 0.3.

3. The apparatus of claim 1 wherein the first RF filter structure further comprises a unidirectional coupling stage coupled to the first plurality of RF resonators, such that the unidirectional coupling stage is configured to provide amplification in a forward direction.

4. The apparatus of claim 1 wherein the first RF filter structure further comprises a bidirectional coupling stage coupled to the first plurality of RF resonators, such that the bidirectional coupling stage is configured to provide coupling in a forward direction and a reverse direction.

5. The apparatus of claim 1 wherein control circuitry is configured to receive the first detected signal and provide a first filter control signal to the first RF filter structure based on the first detected signal, such that the first RF filter structure is further configured to adjust the first filtering characteristic based on the first filter control signal.

6. The apparatus of claim 5 wherein the control circuitry comprises a resonator frequency tuning block, which is configured to provide the first filter control signal.

7. The apparatus of claim 1 wherein the first RF filter structure is further configured to operate in one of an FDD operating mode, a TDD transmit mode, and a TDD receive mode.

8. The apparatus of claim 1 wherein control circuitry is configured to receive the first detected signal and provide a first filter reconfiguration signal to the first RF filter structure based on the first detected signal, such that the first RF filter structure is further configured to adjust the first filtering characteristic based on the first filter reconfiguration signal.

9. The apparatus of claim 8 wherein the control circuitry comprises a coupling tuning block, which is configured to provide the first filter reconfiguration signal.

10. The apparatus of claim 1 wherein the first filtering characteristic is associated with at least one signal path through the first plurality of RF resonators.

11. The apparatus of claim 1 wherein the first filtering characteristic is associated with a single signal path through at least three of the first plurality of RF resonators.

12. The apparatus of claim 11 wherein the first filtering characteristic provides interference rejection filtering.

13. The apparatus of claim 11 wherein the first detected signal is an indication of an interfering signal.

14. The apparatus of claim 1 wherein the first filtering characteristic is associated with at least two parallel signal paths through the first plurality of RF resonators.

15. The apparatus of claim 14 wherein an insertion loss of the at least two parallel signal paths is less than an insertion loss of any one of the at least two parallel signal paths.

16. The apparatus of claim 1 wherein the first detected signal is an indication of an absence of an interfering signal.

17. The apparatus of claim 1 wherein the first filtering characteristic is associated with a bandpass filter response.

18. The apparatus of claim 1 wherein the first filtering characteristic is associated with a bandpass filter response with at least one notch filter response.

19. The apparatus of claim 1 wherein the first filtering characteristic is associated with an impedance transformation via a path through the first plurality of RF resonators.

20. The apparatus of claim 1 wherein electric coupling between two of the first plurality of RF resonators is configured to be adjusted based on a first filter reconfiguration signal.

21. The apparatus of claim 1 wherein the first plurality of RF resonators has electric coupling and magnetic coupling between the first RF resonator and the second RF resonator.

22. The apparatus of claim 21 wherein the electric coupling is configured to be adjusted to provide one of about a net zero coupling, a net positive coupling, and a net negative coupling between the first RF resonator and the second RF resonator based on a first filter reconfiguration signal.

23. The apparatus of claim 21 wherein the electric coupling and the magnetic coupling are configured to be adjusted to provide one of about a net zero coupling, a net positive coupling, and a net negative coupling between the first RF resonator and the second RF resonator based on a first filter reconfiguration signal.

24. The apparatus of claim 1 wherein the first RF filter structure is further configured to further adjust the first filtering characteristic of the first RF filter structure based on external information.