Automatic impedance matching system, method and apparatus
Automatic impedance matching measures the RF source frequency and RF load voltage, current and phase to determine a single match solution for a capacitive value of the variable capacitor and an inductive value for the variable inductor, and whether a shunt reactance is coupled to the RF source or RF load. Once the capacitance and inductance values for a match solution are determined they are contemporaneously selected without any iterative searching necessary for the match solution.
1. A system for matching an impedance of a radio frequency (RF) load to an impedance of a RF source, said system comprising:
a frequency detector for determining a frequency of a RF source;
voltage, current and phase detectors for determining voltage, current and phase of a RF load;
a RF attenuator having an input coupled to the RF source and an output coupled to the frequency, voltage, current and phase detectors;
an impedance matching network coupled to the RF attenuator, frequency, voltage, current and phase detectors and to the RF load, wherein the impedance matching network comprises a variable capacitor and a variable inductor;
a measurement, calculation and control circuit coupled to the frequency, voltage, current and phase detectors, and the variable capacitor and the variable inductor;
wherein from the frequency of the RF source and the voltage, current and phase of the RF load, the measurement, calculation and control circuit calculates capacitance and inductance values required for the variable capacitor and the variable inductor to match the impedance of the RF load to the RF source impedance, and then sets the variable capacitor and the variable inductor to the capacitance and inductance values, respectively;
a first switch coupled in parallel with the impedance matching network;
a second switch coupled in parallel with the RF attenuator and frequency, voltage, current and phase detectors;
wherein
the first switch is closed during calculation of the capacitance and inductance values and setting of the variable capacitor and the variable inductor thereto, and open thereafter, and
the second switch is open when the first switch is closed and closed when the first switch is open.
2. The system according to claim 1 , wherein the impedance matching network is configured as a low pass filter whereby the variable capacitor is coupled at the RF source and the variable inductor is coupled between the RF source and the RF load.
3. The system according to claim 1 , wherein the impedance matching network is configured as a high pass filter whereby the variable inductor is coupled at the RF source and the variable capacitor is coupled between the RF source and the RF load.
4. The system according to claim 1 , wherein the variable inductor comprises a plurality of inductors having an inductance configured with a first plurality of switches that short out unused ones of the plurality of inductors, and the variable capacitor comprises a plurality of capacitors having a capacitance configured with a second plurality of switches that disconnect unused ones of the plurality of capacitors.
5. The system according to claim 4 , wherein the first and second plurality of switches are a first and second plurality of relay contacts.
6. The system according to claim 1 , wherein the RF source is a RF transmitter and the RF load is an antenna.