Design of telescopic stub tuner of 1 5/8′′ transmission line

Stub tuners are integral part of matching network of plasma impedance matching with high power RF generator for maximum transfer of power. Here at IPR we are using various types of stub tuners along with phase shifters for matching the plasma impedance with that of high power RF generator. Here we present the design details of indigenously developed telescopic type stub tuner. In the conventional type stub tuners the overall length of the stub tuner system is more than double the length of matching length. This is because of the movement of plunger and the whole length of the driving rods has to come out of the stub. Hence the overall stub length is more than double the length required for matching. In Telescopic design, during movement of the rods, the single rod does not come out but is adjusted within the other and hence the overall length is just 20% more than the matching length. This not only makes the movement easier, but also reduces the weight, dimensions and the cost of the whole system. In this paper we present the design details, selection of materials, calculations regarding dimensions as per RF frequency requirement, design aspects in handling high RF power and the test results.