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300Watt
Impedance Matching Networks Manual
and Automatic Coaxial
Power Systems Ltd manufacture range of styles of impedance matching network to
link the load to the RF generator. 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. Coaxial Power Systems Ltd. manufacture
two types of network - Manual and Automatic
The manual matching network consists of
two adjustable air vane capacitors and a fixed inductor, which are usually
arranged as an ”L” network. (The arrangement can be simply converted to a
“Pi” network if required). Geared drives with vernier dials are used to
adjust the capacitors for minimum reflected power as displayed on the generator
reflected power meter. When the reflected power is zero, the system is
“tuned” and all of the power output of the generator is being fed to the
load.
The automatic matching network is similar
to the manual version except that servomotors drive the capacitors. At the input of the network, a phase and
magnitude detector determines the position of the capacitors. This information
is transferred to the separate controller. The controller then drives the
servomotors to the positions, which give zero, or minimum reflected power. The controller is ½ rack, 2U high and
can be fitted alongside any generator in the Coaxial Power Systems range of low
power RF generators.
The start position of the capacitors can
be individually adjusted. When RF power is detected, the capacitors
automatically adjust for minimum reflected power. When the RF is turned off, the
motors drive the capacitors back to heir original position. The start positions
are adjusted using potentiometers accessible via the controller front panel 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 that 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. Note:
This option not available on manual networks (07.06.2007)
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