Impedance adjusting apparatus
An impedance adjustment apparatus of the invention performs impedance matching using characteristic parameters, even where a high frequency power source of variable frequencies is used. The apparatus is applicable to a power supply system using a high frequency power source of variable frequencies. Characteristic parameters obtained by targeting a portion of combinations of position information (C) of a variable capacitor and output frequency information (F) of the power source are stored in a memory. A T-parameter acquisition unit acquires characteristic parameters corresponding to (C now , F now ) at the current time. An output reflection coefficient calculation unit calculates a reflection coefficient of an output end. A target information specifying unit, based on the above information and a target input reflection coefficient, specifies target combination information in which a reflection coefficient of an output end approaches the target input reflection coefficient. Impedance matching is performed based on this information.
1. An impedance adjustment apparatus that is provided between a high frequency power source and a load, and adjusts a target impedance seen from the high frequency power source to the load, the apparatus comprising:
an input end for connecting to the high frequency power source;
an output end for connecting to the load;
a variable electrical characteristic element;
a characteristic parameter storage unit for storing a plurality of characteristic parameters indicating transmission characteristics of the impedance adjustment apparatus, the plurality of characteristic parameters being parameters that are respectively acquired for a plurality of adjustment points at which a plurality of frequency adjustment points that correspond to output frequencies of the high frequency power source are combined with a plurality of electrical characteristic adjustment points that correspond to electrical characteristics of the variable electrical characteristic element;
a high frequency information detection unit for detecting high frequency information of the input end;
an output frequency acquisition unit for acquiring an output frequency of the high frequency power source;
an electrical characteristic acquisition unit for acquiring an electrical characteristic of the variable electrical characteristic element;
a characteristic parameter acquisition unit for acquiring a characteristic parameter for an adjustment point at which the acquired output frequency is combined with the acquired electrical characteristic, based on the plurality of characteristic parameters;
an output reflection coefficient calculation unit for calculating an output reflection coefficient of the output end, based on the high frequency information detected by the high frequency information detection unit and the characteristic parameter acquired by the characteristic parameter acquisition unit;
a specifying unit for specifying an impedance adjustment point at which to match the target impedance to the impedance of the high frequency power source, among the plurality of adjustment points, based on the output reflection coefficient, a target input reflection coefficient set in advance, and the plurality of characteristic parameters;
an electrical characteristic element adjustment unit for adjusting the electrical characteristic of the variable electrical characteristic element to an electrical characteristic of the impedance adjustment point; and
a command signal output unit for outputting, to the high frequency power source, a command signal for adjusting the output frequency of the high frequency power source to an output frequency of the impedance adjustment point.
2. The impedance adjustment apparatus according to claim 1 ,
wherein the characteristic parameter storage unit stores characteristic parameters measured for every adjustment point, or characteristic parameters that are converted from the measured characteristic parameters and are different in type from the measured characteristic parameters.
3. The impedance adjustment apparatus according to claim 2 ,
wherein the measured characteristic parameters are S-parameters (scattering parameters) and the characteristic parameters that are different in type from the measured characteristic parameters are T-parameters (transmission parameters).
4. The impedance adjustment apparatus according to claim 1 ,
wherein the plurality of characteristic parameters that are stored in the characteristic parameter storage unit include actual values measured at each adjustment point with respect to a portion of the plurality of adjustment points, and estimated values computed at each adjustment point by interpolation using the actual values with respect to adjustment points that have not been measured among the plurality of adjustment points.
5. The impedance adjustment apparatus according to claim 4 ,
wherein the adjustment points at which the characteristic parameters were measured are adjustment points at which a portion of frequency adjustment points extracted at a first interval from the plurality of frequency adjustment points are combined with a portion of electrical characteristic adjustment points extracted at a second interval from the plurality of electrical characteristic adjustment points.
6. The impedance adjustment apparatus according to claim 1 ,
wherein the specifying unit, based on the target input reflection coefficient and the plurality of characteristic parameters, calculates a virtual output reflection coefficient of the output end at each adjustment point assuming that the output frequency of the high frequency power source and the electrical characteristic of the variable electrical characteristic element have been adjusted to the plurality of adjustment points, and specifies an adjustment point at which a difference between the output reflection coefficient and the virtual output reflection coefficient is smallest as an adjustment point of the target impedance.
7. The impedance adjustment apparatus according to claim 1 ,
wherein the high frequency information is a traveling wave voltage that travels from the high frequency power source to the load and a reflected wave voltage that is reflected from the load to the high frequency power source.
8. The impedance adjustment apparatus according to claim 1 ,
wherein the output reflection coefficient calculation unit calculates an input reflection coefficient of the input end based on the high frequency information, and calculates the output reflection coefficient based on the calculated input reflection coefficient and the acquired characteristic parameter.
9. The impedance adjustment apparatus according to claim 1 , further comprising:
a frequency detection unit for detecting the output frequency of the high frequency power source using the high frequency information.
10. The impedance adjustment apparatus according to claim 1 ,
wherein the high frequency power source outputs, to the impedance adjustment apparatus, information on an output frequency of a high frequency wave that is output, and
the output frequency acquisition unit acquires the information on the output frequency that is input from the high frequency power source, as the output frequency of the high frequency power source.