Patent ID: 7933381

Claim:
An HF frequency tuning device comprising: an HF generator for generating a high frequency traveling wave; a resonance cavity to which said high frequency traveling wave is introduced, said resonance cavity reflecting the high frequency traveling wave and generating a high frequency reflected wave; a phase detecting section for detecting the high frequency traveling wave and the high frequency reflected wave in said resonance cavity, said phase detecting section generating a sign data which represents a sign of a phase difference between the high frequency traveling wave and the high frequency reflected wave; a controlling section configured to control a frequency of said high frequency traveling wave to reduce said phase difference based on said sign data; and a storage device storing a first pitch value; wherein said controlling section is configured to execute a first controlling process in which a frequency of said high frequency traveling wave is repeatedly shifted by said first pitch value until said sign represented in said sign data is inverted, and perform the first controlling process based on said sign represented by said sign data without using a value of said phase difference.