Circuit and method for impedance matching
AssigneeMotorola, Inc.
InventorsGerard Jean Louis Bouisse, John E. Morgan
Life of this patent
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Abstract
An impedance matching circuit (10) matches the impedance of a load (19) coupled to an RF amplifier (12) to that of the RF amplifier (12). The impedance matching circuit (10) samples a transmitted signal from the RF amplifier (12) and a reflected signal from the load (19). The amplitude and the phase of the sampled reflected signal are compared with those of the sampled transmitted signal to calculate the impedance mismatch. A control logic circuit (80) adjusts the capacitance and inductance values of variable capacitance (23; 27) and inductance (35) elements in the impedance matching circuit (10), thereby matching the impedance of the load (19) to that of the RF amplifier (12).
Claims15
An impedance matching circuit, comprising:
- an interface circuit having an input, an output, and a plurality of control terminals, the interface circuit including a first capacitance element having a first terminal coupled to the input and the output of the interface circuit, and a second terminal coupled for receiving a reference voltage, wherein the first capacitance element comprises a first voltage controlled variable capacitor having a first electrode coupled to the first terminal of the first capacitance element and a second electrode coupled to the second terminal of the first capacitance element, and a first resistor having a first electrode coupled to a first control terminal of the plurality of control terminals of the interface circuit and a second electrode coupled to the first electrode of the first voltage controlled variable capacitor;
- a phase and magnitude detection element having a first terminal coupled to the output of the interface circuit, a second terminal, a phase output, and a magnitude output;
- and
- a control logic circuit having a first input coupled to the phase output of the phase and magnitude detection element, a second input coupled to the magnitude output of the phase and magnitude detection element, and a plurality of outputs coupled to the plurality of control terminals of the interface circuit.
An impedance matching circuit, comprising:
- a first adjustable capacitance element having a first terminal coupled for receiving a radio frequency signal, a second terminal coupled for receiving a reference voltage, and a control terminal. the first adjustable capacitance element including a first variable capacitor having a first electrode coupled to the first terminal of the first adjustable capacitance element and a second electrode coupled to the second terminal of the first adjustable capacitance element, and a first resistor having a first electrode coupled to the control terminal of the first adjustable capacitance element and a second electrode coupled to the first electrode of the first variable capacitor;
- a second adjustable capacitance element having a first terminal, a second terminal coupled for receiving the reference voltage, and a control terminal;
- an adjustable inductance element having a first terminal coupled to the first terminal of the first adjustable capacitance element, a second terminal coupled to the first terminal of the second adjustable capacitance element, and a control terminal;
- a Voltage Standing Wave Ratio (VSWR) detection element having a first terminal coupled to the first terminal of the second adjustable capacitance element, a second terminal coupled for transmitting the radio frequency signal and receiving a reflected signal in response to the radio frequency signal, a VSWR phase output, and a VSWR magnitude output;
- and
- a control logic circuit having a first input coupled to the VSWR phase output of the VSWR detection element, a second input coupled to the VSWR magnitude output of the VSWR detection element, a first output coupled to the control terminal of the first adjustable capacitance element, a second output coupled to the control terminal of the second adjustable capacitance element, and a third output coupled to the control terminal of the adjustable inductance element.
Dependencies are inferred from the claim text.