CMOS tuner and related tuning algorithm for a passive adaptive antenna matching network suitable for use with agile RF transceivers
A novel and useful adaptive antenna tuner and associated calibration mechanism for passive adaptive antenna matching networks. The tuner is suitable for use with cellular antennas and in one embodiment uses MEMS based tunable devices. The tuner contains voltage and current sensors inserted before the antenna matching network. The sensed complex impedance generates one or more update control signals for the tuning algorithm which drives the MEMS-based tunable devices.
1. An adaptive antenna tuner coupled to an antenna matching network, comprising:
a sensor circuit operative to generate:
a current sense signal sensed from an input to the antenna matching network;
a voltage sense signal sensed from the input to the antenna matching network; and
a tuning control signal circuit operative to generate, in accordance with said current sense signal and said voltage sense signal, control signals for output to the antenna matching network for modifying the impedance thereof to improve impedance matching between an associated antenna and power amplifier coupled thereto;
wherein first control signals are generated so as to add capacitance and/or inductance to said matching network to minimize a phase difference between said voltage sense signal and said current sense signal, wherein the phase difference represents an imaginary part of the impedance; and
wherein second control signals are generated, once said phase is minimized, so as to modify capacitance and/or inductance within said matching network to maximize a product of said voltage and said current, thereby moving said impedance to a center of a Smith chart and maximizing power transfer to said antenna.
2. The adaptive antenna tuner according to claim 1 , wherein said voltage sense signal is generated utilizing a capacitive divider.
3. The adaptive antenna tuner according to claim 1 , wherein said current sense signal is generated based on magnetic coupling with a transmission line connecting a power amplifier to the antenna matching network.
4. The adaptive antenna tuner according to claim 1 , wherein said current sense signal and said voltage sense signal are processed to obtain an X-path signal to indicate a sign of an input impedance imaginary part and an R-path signal to indicate whether a magnitude of input power from an associated power amplifier is maximized.
5. The adaptive antenna tuner according to claim 4 , wherein said R-signal indicates maximum transmitted power corresponding to an impedance at a center of a corresponding Smith chart representing impedance of the antenna matching network.
6. The adaptive antenna tuner according to claim 4 , wherein said X-signal indicates whether a current real part of said voltage sense signal and said current sense signal is closer or further away from a horizontal axis of a corresponding Smith chart representing impedance of the antenna matching network.
7. The adaptive antenna tuner according to claim 1 , wherein said first control signal is operative to indicate whether to add capacitance or inductance to a tunable component in the antenna matching network.
8. The adaptive antenna tuner according to claim 1 , wherein said second control signal is operative to indicate whether to tune a tunable component in the antenna matching network in a same or opposite direction as a previous tuning step.
9. A method of tuning an adaptive matching network coupled to an antenna matching network, the method comprising:
receiving sense signals indicating voltage and current input to the antenna matching network and representing a complex input impedance thereof;
generating an X-path signal indicating a sign of an imaginary part of said complex input impedance;
generating an R-path signal indicating whether a current real part of said one or more sense signals is closer or further away from a horizontal axis of a corresponding Smith chart representing a complex impedance of the antenna matching network;
generating, based on said voltage and current sense signals, control signals for modifying the impedance of the antenna matching network in accordance therewith to improve impedance matching between an associated antenna and power amplifier coupled thereto;
wherein first control signals are generated so as to add capacitance and/or inductance to said matching network to minimize a phase difference between said voltage sense signal and said current sense signal; and
wherein second control signals are generated, once said phase is minimized, so as to modify capacitance and/or inductance within said matching network to maximize a product of said voltage and said current, thereby moving said impedance to a center of the Smith chart and maximizing power transfer to said antenna.
10. The method according to claim 9 , wherein said voltage sense signal is generated utilizing a capacitive divider.
11. The method according to claim 9 , wherein said current sense signal is generated based on magnetic coupling with a transmission line connecting a power amplifier to the antenna matching network.
12. The method according to claim 9 , wherein said R-path signal indicates whether a magnitude of input power from said associated power amplifier is maximized.
13. The method according to claim 9 , wherein said first control signal is operative to indicate whether to add capacitance or inductance to a tunable component in said antenna matching network.
14. The method according to claim 9 , wherein said second control signal is operative to indicate whether to tune a tunable component in said antenna matching network in a same or opposite direction as a previous tuning step.
15. An adaptive antenna tuner coupled to an antenna matching network, comprising:
a sensor circuit operative to generate from one or more sense signals indicating voltage and current input to the antenna matching network and representing a complex input impedance thereof:
an X-path signal indicating a sign of an imaginary part of said complex input impedance;
an R-path signal indicating whether a current real part of said one or more sense signals is closer or further away from a horizontal axis of a corresponding Smith chart representing a complex impedance of the antenna matching network;
a tuning control signal circuit operative to generate, based on said voltage and current sense signals, control signals for output to said antenna matching network for modifying the impedance thereof to improve impedance matching between an associated antenna and power amplifier coupled thereto;
wherein first control signals are generated so as to add capacitance and/or inductance to said matching network to minimize a phase difference between said voltage and current sense signals, wherein the phase difference represents an imaginary part of the impedance; and
wherein second control signals are generated, once said phase is minimized, so as to modify capacitance and/or inductance within said matching network to maximize a product of said voltage signal and said current signal, thereby moving said impedance to a center of a Smith chart and maximizing power transfer to said antenna.
16. The adaptive antenna tuner according to claim 15 , wherein said second control signal is operative to indicate whether to tune a most sensitive R-tuning component in the antenna matching network in a current R-tuning step in the same or opposite direction of a previous R-tuning step.
17. The adaptive antenna tuner according to claim 15 , wherein said voltage sense signal is generated utilizing a capacitive divider.
18. The adaptive antenna tuner according to claim 15 , wherein said current sense signal is generated based on magnetic coupling with a transmission line connecting a power amplifier to the antenna matching network.
19. The adaptive antenna tuner according to claim 15 , wherein said first control signal is operative to indicate whether to add capacitance or inductance to a most sensitive X-tuning component in the antenna matching network.
20. A method of adaptively tuning an antenna matching network coupled to an antenna, the method comprising:
generating a current signal and a voltage signal sensed from an output of a power amplifier coupled to said antenna matching network;
generating one or more control signals for output to the antenna matching network for modifying the impedance thereof in accordance with said current signal and said voltage signal, wherein said one or more control signals are generated so as to:
add capacitance and/or inductance to said matching network to minimize a phase difference between said voltage signal and said current signal thereby generating a substantially real impedance, wherein the phase difference represents an imaginary part of the impedance; and
modify capacitance and/or inductance in said matching network, once said phase is minimized, to move said substantially real impedance to a center of a Smith chart by maximizing a product of said voltage and current, thereby maximizing power transfer to said antenna.