AUTOMATIC IMPEDANCE ADJUSTMENT

摘要

An apparatus and method are described for automatically matching the impedance of an antenna. An impedance matching network includes at least one variable impedance element and has an input for receiving a drive signal and an output connectable to an antenna. The impedance matching network includes a shunt capacitor in series between the input and output. A phase measuring measures the phase difference between the voltage and the current of the drive signal using the voltage drop across the shunt capacitor and outputs a measured phase signal. A voltage measuring circuit measures the magnitude of the voltage of the drive signal and the voltage drop across the shunt capacitor and outputs a measured drive voltage signal and shunt capacitor voltage signal. An automatic impedance matching circuit can output a control signal to adjust the impedance of the variable impedance element and determines the impedance of the impedance matching network from the measured phase, drive voltage and shunt capacitor voltages automatically to reduce the difference between the determined impedance of the impedance matching network and the impedance of the antenna.

主权项

1. An apparatus for automatically adjusting the impedance of network to match a target impedance, the apparatus comprising:
an electrical power source configured to deliver AC electrical power to a target impedance; a network having an input for receiving a drive signal from the electrical power source and an output connectable to an antenna, the network including a shunt reactance between the input and the output and at least one variable impedance element; a phase measuring circuit arranged to measure the phase difference between the voltage of the drive signal and the current of the drive signal in the network using the voltage drop across the shunt reactance; a voltage measuring circuit arranged to measure the magnitude of the voltage of the drive signal and the magnitude of the voltage drop across the shunt reactance; and an automatic impedance adjustment circuit in communication with the variable impedance element, the phase measuring circuit and the voltage measuring circuit and arranged to receive the measured phase difference, measured magnitude of the voltage of the drive signal and measured magnitude of the voltage drop across the shunt reactance, to determine the impedance of the network from them and automatically to reduce the difference between the determined impedance of the network and the target impedance by outputting a control signal to adjust the impedance of the variable impedance element.