Acoustic load-line tuning in a wireless transmission circuit
Acoustic impedance tuning in a wireless transmission circuit (a.k.a. wireless device) is provided. In aspects discussed herein, the wireless transmission circuit includes an acoustic load-line tuning circuit that can be configured to adapt a load-line impedance presenting to a power amplifier circuit. In embodiments disclosed herein, the acoustic load-line tuning circuit can be dynamically controlled to provide impedance matching between a power amplifier circuit and other load-line circuits (e.g., filter circuits, antenna switch circuits, and/or antenna circuits). As a result, it is possible to reduce a signal reflection resulting from an impedance mismatch between the power amplifier circuit and the load-line circuits, thus helping to improve performance of the wireless transmission circuit.
1 . An acoustic load-line tuning circuit comprising:
a plurality of acoustic resonator structures coupled in parallel between a signal input and a signal output and free of switches, each of the plurality of acoustic resonator structures is configured to resonate at a series resonance frequency to pass a signal from the signal input to the signal output and present a respective one of a plurality of load-line impedances at the signal input in response to receiving a respective one of a plurality of pulse voltages; and
a control circuit configured to:
determine a desired load-line impedance at the signal input based on a maximum power of the signal; and
apply the respective one of the plurality of pulse voltages to a selected one of the plurality of acoustic resonator structures having the respective one of the plurality of load-line impedances that is closest to the desired load-line impedance.
2 . The acoustic load-line tuning circuit of claim 1 , wherein the control circuit is coupled to each of the plurality of acoustic resonator structures via a respective one of a plurality of resistors.
3 . The acoustic load-line tuning circuit of claim 1 , further comprising a tunable active circuit coupled in parallel to the plurality of acoustic resonator structures between the signal input and the signal output, the tunable active circuit is configured to cancel a respective electrical capacitance associated with each of the plurality of acoustic resonator structures.
4 . The acoustic load-line tuning circuit of claim 3 , wherein the tunable active circuit comprises:
a first inductor and a second inductor coupled in series between the signal input and the signal output; and
an impedance circuit coupled between an intermediate node located in between the first inductor and the second inductor and a ground, the impedance circuit is configured to actively generate a shunt impedance to thereby cause a negative capacitance between the signal input and the signal output.
5 . The acoustic load-line tuning circuit of claim 1 , wherein each of the plurality of acoustic resonator structures comprises a bulk acoustic wave (BAW) resonator.
6 . The acoustic load-line tuning circuit of claim 5 , wherein the BAW resonator comprises a pair of stacked BAW resonators.
7 . The acoustic load-line tuning circuit of claim 6 , wherein the pair of stacked BAW resonators comprises a polarized BAW resonator and a polarized-inverted BAW resonator.
8 . A wireless transmission circuit comprising:
an acoustic load-line tuning circuit comprising:
a plurality of acoustic resonator structures coupled in parallel between a signal input and a signal output and free of switches, each of the plurality of acoustic resonator structures is configured to resonate at a series resonance frequency to pass a signal from the signal input to the signal output and present a respective one of a plurality of load-line impedances at the signal input in response to receiving a respective one of a plurality of pulse voltages; and
a control circuit configured to:
determine a desired load-line impedance at the signal input based on a maximum power of the signal; and
apply the respective one of the plurality of pulse voltages to a selected one of the plurality of acoustic resonator structures having the respective one of the plurality of load-line impedances that is closest to the desired load-line impedance.
9 . The wireless transmission circuit of claim 8 , wherein the control circuit is coupled to each of the plurality of acoustic resonator structures via a respective one of a plurality of resistors.
10 . The wireless transmission circuit of claim 8 , wherein the acoustic load-line tuning circuit further comprises a tunable active circuit coupled in parallel to the plurality of acoustic resonator structures between the signal input and the signal output, the tunable active circuit is configured to cancel a respective electrical capacitance associated with each of the plurality of acoustic resonator structures.
11 . The wireless transmission circuit of claim 10 , wherein the tunable active circuit comprises:
a first inductor and a second inductor coupled in series between the signal input and the signal output; and
an impedance circuit coupled between an intermediate node located in between the first inductor and the second inductor and a ground, the impedance circuit is configured to actively generate a shunt impedance to thereby cause a negative capacitance between the signal input and the signal output.
12 . The wireless transmission circuit of claim 8 , wherein each of the plurality of acoustic resonator structures comprises a bulk acoustic wave (BAW) resonator.
13 . The wireless transmission circuit of claim 12 , wherein the BAW resonator comprises a pair of stacked BAW resonators.
14 . The wireless transmission circuit of claim 13 , wherein the pair of stacked BAW resonators comprises a polarized BAW resonator and a polarized-inverted BAW resonator.
15 . The wireless transmission circuit of claim 8 , further comprising:
a power amplifier circuit configured to amplify the signal;
a band switch circuit coupled to the power amplifier circuit and configured to pass the amplified signal in a respective one of a plurality of passbands;
a filter circuit comprising the acoustic load-line tuning circuit and configured to:
pass the signal in the series resonance frequency of the selected one of the plurality of acoustic resonator structures; and
present the respective one of the plurality of load-line impedances of the selected one of the plurality of acoustic resonator structures at the signal input;
an antenna switch circuit coupled to the filter circuit; and
an antenna circuit coupled to the antenna switch circuit.
16 . The wireless transmission circuit of claim 8 , further comprising:
a power amplifier circuit configured to amplify the signal;
the acoustic load-line tuning circuit coupled to the power amplifier circuit and configured to:
pass the signal in the series resonance frequency of the selected one of the plurality of acoustic resonator structures; and
present the respective one of the plurality of load-line impedances of the selected one of the plurality of acoustic resonator structures at the signal input;
a band switch circuit coupled to the power amplifier circuit and configured to pass the amplified signal in a respective one of a plurality of passbands;
a filter circuit comprising an acoustic ladder network coupled to the band switch circuit;
an antenna switch circuit coupled to the filter circuit; and
an antenna circuit coupled to the antenna switch circuit.
17 . A method for performing acoustic impedance tuning in a wireless transmission circuit comprising:
coupling a plurality of acoustic resonator structures in parallel between a signal input and a signal output and free of switches;
configuring each of the plurality of acoustic resonator structures to resonate at a series resonance frequency to pass a signal from the signal input to the signal output and present a respective one of a plurality of load-line impedances at the signal input in response to receiving a respective one of a plurality of pulse voltages;
determining a desired load-line impedance at the signal input based on a maximum power of the signal; and
applying the respective one of the plurality of pulse voltages to a selected one of the plurality of acoustic resonator structures having the respective one of the plurality of load-line impedances that is closest to the desired load-line impedance.
18 . The method of claim 17 , further comprising performing the acoustic impedance tuning in the wireless transmission circuit using an acoustic load-line tuning circuit.