Method and apparatus for automatic tuning of a resonant loop antenna in a transceiver circuit
First Claim
1. A transceiver circuit having a transmitter circuit, a receiver circuit, and an automatic tuning circuit, where the transmitter circuit includes a power amplifier and where the automatic tuning circuit comprises:
- a capacitance bank coupled between the power amplifier and a package connection for connecting to a resonant circuit that includes an antenna, the capacitance bank having an input that is coupled to an output of the power amplifier, an output that is coupled to the resonant circuit, and a control input, where a capacitance of the capacitance bank is determined by a control word received at the control input; and
a tuning circuit having a first input for receiving a first voltage present at the inputs of the power amplifier, a second input for receiving a second voltage present across the capacitance bank, a mode input for receiving a mode signal, and an output for generating the control word responsive to the first and second voltages, where the tuning circuit is further configured to hold constant the value of the control word responsive to the mode signal, where the mode signal corresponds to a receive mode.
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Accused Products
Abstract
Disclosed is a circuit and method for automatic tuning of a resonant circuit in a transceiver having a receiver and a transmitter that includes a power amplifier for driving the resonant circuit. During a transmit mode of the transceiver, a resonance voltage of the resonant circuit is compared to an input voltage signal to the power amplifier to determine an error signal that is converted into a control word. The control word drives an adjustable capacitance bank that is part of the resonant circuit. During a receive mode of the transceiver, the control word value is held constant to substantially maintain resonance of the resonant circuit during operation of the receiver.
76 Citations
17 Claims
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1. A transceiver circuit having a transmitter circuit, a receiver circuit, and an automatic tuning circuit, where the transmitter circuit includes a power amplifier and where the automatic tuning circuit comprises:
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a capacitance bank coupled between the power amplifier and a package connection for connecting to a resonant circuit that includes an antenna, the capacitance bank having an input that is coupled to an output of the power amplifier, an output that is coupled to the resonant circuit, and a control input, where a capacitance of the capacitance bank is determined by a control word received at the control input; and a tuning circuit having a first input for receiving a first voltage present at the inputs of the power amplifier, a second input for receiving a second voltage present across the capacitance bank, a mode input for receiving a mode signal, and an output for generating the control word responsive to the first and second voltages, where the tuning circuit is further configured to hold constant the value of the control word responsive to the mode signal, where the mode signal corresponds to a receive mode. - View Dependent Claims (2, 3, 4, 5)
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6. A method for automatically tuning a resonant circuit that includes an antenna, the resonant circuit being part of transceiver circuit that includes a receiver circuit and a transmitter circuit that includes a power amplifier for driving the resonant circuit, the method comprising the steps of:
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providing an adjustable capacitance as part of the resonant circuit; comparing a resonance signal of the resonant circuit to an input signal to the power amplifier in order to generate a control word signal for controlling the adjustable capacitance; varying the adjustable capacitance responsive to the control word signal in order to tune the resonant circuit during a transmit mode; and maintaining a constant value for the control word signal responsive to a mode signal corresponding to a receive mode of the transceiver. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A transceiver system, the transceiver system including an automatic tuning circuit for automatically tuning a resonant circuit that includes an antenna, where the transceiver system also includes a receiver and a transmitter having a power amplifier for driving the resonant circuit, the system comprising:
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adjustable capacitance means for providing an adjustable capacitance as part of the resonant circuit; means for comparing a resonance signal of the resonant circuit to an input signal to the power amplifier in order to generate a control word signal for controlling the adjustable capacitance; and means for varying the adjustable capacitance responsive to the control word signal in order to tune the resonant circuit during a transmit mode and maintaining a constant value for the control word signal responsive to a mode signal corresponding to a receive mode of the transceiver. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification