4000-Watt Automatic Impedance Matching Networks
Coaxial Power Systems Ltd
manufacture two styles of impedance matching network to link the load to the RF
generator, Automatic networks and Manually operated networks. In both cases the
purpose of the network is to adjust the input impedance of the load to 50 Ohms
so that maximum power is transferred from the generator, whose output impedance
is 50 Ohms, to the load. The network must be installed as close a possible to
the load. The best possible position, in a plasma application for example, would
be to mount the network directly on the vacuum chamber with a direct connection
to the electrode or magnetron.
Automatic Matching Network
At
the input of the network, a phase and magnitude detector determines the error in
the position of the capacitors. This information is transferred to the separate
controller. The controller then drives the servomotors to the positions of
minimum reflected power.
The controller is 19 inch rack, 2U high and is usually located near the generator.
As an alternative CPS can supply
a RF generator with the AMN controller installed in the front panel of the
generator. This option is available on nearly all 4U full width RFG models.
The position of each variable capacitor is shown on a 31/2 digit LED meter, and made available on a “remote” connector. Automatic or Manual mode is switch selectable - in manual mode the servomotors can be tuned by the operator using two switches.
The
start or base position of the capacitors can be individually adjusted. When the
RF is turned off, the motors drive the capacitors back to their base position.
The start positions are adjusted using potentiometers accessible via the
controller front panel, or they can be programmed externally via the remote
connector.
Option: Model
DCP-1 : Dark Space Bias Voltage Measurement and Control
A probe, installed inside the network, measures the d.c voltage (0 to 1999V) developed across the dark space in plasma applications such as sputtering and reactive ion etching. The voltage is converted to a 0 to 5V signal, which can be fed back to the generator control system. The voltage is displayed on the loading capacitor position meter. Includes all necessary cables to link to any generator in the low power range manufactured by Coaxial Power Systems Ltd.
(07.06.2007)