Weakly coupled tunable RF transmitter architecture
View Patent ↗RF communications circuitry, which includes a first tunable RF filter and an RF power amplifier (PA), is disclosed. The first tunable RF filter includes a pair of weakly coupled resonators, and receives and filters a first upstream RF signal to provide a first filtered RF signal. The RF PA is coupled to the first tunable RF filter, and receives and amplifies an RF input signal to provide an RF output signal.
1. An apparatus comprising:
a first tunable RF filter comprising a pair of weakly coupled resonators and configured to:
receive and filter a first upstream RF signal to provide a first filtered RF signal;
operate in a Class F mode of operation during an average power tracking mode; and
operate in a Class inverse F mode of operation during an envelope tracking mode;
an RF power amplifier (PA) coupled to the first tunable RF filter and configured to:
receive and amplify an RF input signal to provide an RF output signal; and
operate in the average power tracking mode when an output power from the RF PA is above a power threshold and operate in the envelope tracking mode when the output power from the RF PA is below the power threshold; and
a transformer coupled between the first tunable RF filter and an output of the RF PA.
2. The apparatus of claim 1 wherein the RF PA is a multi-band RF PA.
3. The apparatus of claim 1 wherein the RF PA comprises a driver PA stage and a final PA stage.
4. The apparatus of claim 3 wherein an output of the final PA stage is the output of the RF PA.
5. The apparatus of claim 4 wherein the first tunable RF filter is further configured to attenuate noise produced by the final PA stage.
6. The apparatus of claim 4 wherein an input impedance to the first tunable RF filter is programmable.
7. The apparatus of claim 6 further comprising control circuitry configured to adjust the input impedance to the first tunable RF filter using a first filter reconfiguration signal.
8. The apparatus of claim 6 wherein the first tunable RF filter is further configured to provide at least a partial output impedance match to the final PA stage.
9. The apparatus of claim 6 wherein the final PA stage is segmented.
10. The apparatus of claim 9 further comprising a segmented PA coupling circuit, which is coupled between the output of the final PA stage and the first tunable RF filter.
11. The apparatus of claim 10 wherein the segmented PA coupling circuit comprises the transformer, which is a multi-tap transformer.
12. The apparatus of claim 9 wherein the final PA stage has a plurality of segment connection nodes.
13. The apparatus of claim 12 wherein the first tunable RF filter comprises a plurality of capacitive elements coupled in parallel with one another, such that each capacitive element is coupled to a corresponding one of the plurality of segment connection nodes.
14. The apparatus of claim 4 further comprising a second tunable RF filter coupled to the first tunable RF filter.
15. The apparatus of claim 14 further comprising a third tunable RF filter coupled to the second tunable RF filter.
16. The apparatus of claim 1 wherein during the Class F mode of operation, the first tunable RF filter is further configured to substantially attenuate at least one even harmonic of a frequency of the RF input signal; and during the Class inverse F mode of operation, the first tunable RF filter is further configured to substantially attenuate at least one odd harmonic of the frequency of the RF input signal.
17. The apparatus of claim 1 wherein the pair of weakly coupled resonators has a magnetic coupling coefficient that is less than 0.3.
18. The apparatus of claim 1 further comprising control circuitry configured to select the one of the average power tracking mode and the envelope tracking mode.
19. An apparatus comprising:
a first tunable RF filter comprising a pair of weakly coupled resonators and configured to receive and filter a first upstream RF signal to provide a first filtered RF signal, wherein an input impedance to the first tunable RF filter is programmable;
an RF power amplifier (PA) comprising a driver PA stage and a final PA stage, which is segmented and has an output coupled to the first tunable RF filter, such that the RF PA is coupled to the first tunable RF filter and configured to receive and amplify an RF input signal to provide an RF output signal; and
control circuitry configured to enable at least a portion of segments of the final PA stage based on an expected output power from the RF PA using a segment control signal and tune a load line of the final PA stage by adjusting the input impedance to the first tunable RF filter based on enabled segments of the final PA stage.
20. The apparatus of claim 19 further comprising a tapped inductor coupled between the first tunable RF filter and an output of the RF PA.
21. The apparatus of claim 19 wherein the pair of weakly coupled resonators has a magnetic coupling coefficient that is less than 0.3.
22. An apparatus comprising:
a first tunable RF filter comprising a pair of weakly coupled resonators and configured to receive and filter a first upstream RF signal to provide a first filtered RF signal, wherein an input impedance to the first tunable RF filter is programmable; and
an RF power amplifier (PA) comprising a driver PA stage and a final PA stage, which is segmented and has a plurality of segment connection nodes, such that the RF PA is coupled to the first tunable RF filter and configured to receive and amplify an RF input signal to provide an RF output signal, wherein the first tunable RF filter comprises a plurality of switched capacitors coupled in parallel with one another, such that each switched capacitor includes a capacitive element coupled in series with a switching element, and each switched capacitor is coupled to a corresponding one of the plurality of segment connection nodes.
23. The apparatus of claim 22 wherein the pair of weakly coupled resonators has a magnetic coupling coefficient that is less than 0.3.