RF Power Applications
Morgan
Electro Ceramic is a leader in the design and manufacture
of advanced ceramic products with over 50 years experience
in the manufacture of electroceramic materials and
components for the RF industry.
RF (Radio
Frequency) Induction Heating
Metals can be
heated or melted rapidly by inducing a high current to
flow through them. The heaters are used for many end
purposes e.g.,
- heating metal car panels to enable them to be formed to
shape.
- heating metal billets to allow them to be formed into
tubes or rods
- induction welding of
pipes
- fusion of metals for casting in the dental and jewellery
industries
- induction hardening of metals.
RF Dielectric Heating
Rapid Drying
of materials which usually contain water e.g. textiles,
wood, wood glues, foodstuffs such as biscuits.
In this case
the molecules of water in the material are made to vibrate
by the application of a high RF field causing them to
generate heat with the result that drying occurs.
RF Broadcast Transmitters
High power
radio transmitters use these types of capacitors in the
antenna circuit.
RF Power - Plasma Generators used in Semiconductor
Manufacture.
(1 100MHz) RF
Power used to ionise gas thus generating RF plasma used in
various deposition 1 etching 1 cleaning processes.
High Power Matching Networks in Plasma Generators.
Matching
network used to tune Plasma Chamber Impedance to a
constant load.
Flat Panel
Displays
Medical RF
Generators
How and
why these capacitors are used
The
capacitors act as filters to block D and pass AC. They
also form the capacitive part of the resonant circuit to
drive the induction coil - please see the attached diagram
for an explanation of where they are used in the circuit.
The ability
to withstand high RF voltages.
They handle
high RF power and current levels due to the low loss 1
high Q of the ceramic dielectrics employed.
The Doorknob range, in particular,
exhibit low equivalent series inductance (ESL, due to
their small size. The latter increases the self resonant
frequency allowing their use at higher frequencies.
Tight
tolerance grading can be offered, on certain parts,
permitting precise tuning within the matching units thus
minimising power loss within the load maximising
efficiency.
The low
temperature coefficients, particularly the NPO, of the
dielectric materials used, result in minimal frequency
drift with operating temperature again allowing precise
tuning within matching units
RF Power
Capacitor Applications
RF
Induction Heating / Dielectric Heating
C1 =
1-5nF for induction heating
C1 = 50-200pF for dielectric heating
Capacitors
Coupling
- Passes ac
- Block dc
Blocking
- Blocks dc voltage
- Passed ac signal to RF resonant circuit
Decoupling
- FIlters out, to ground, ac noise generated in the
cathode
Tank
- Tuned circuit comprising tank capacitor and inductance
coil to provide high circulating current in the tuned
resonant circuit
You
may also find the following sections of particular
interest if you are associated with high power RF
applications:-
Capacitors Tutorial and Guides
RF Multilayer Capacitor Applications
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