US 4,375,051 AGranted

Automatic impedance matching between source and load

AssigneeThe Perkin-Elmer Corporation

InventorC. Earle Theall

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Abstract

An R.F. generator for providing power to a load via a transmission line wherein load impedance is automatically matched to the surge impedance of the transmission to provide maximum transfer of energy from the generator to the load. Voltages representative of input power and reflected power are utilized to control a load match circuit to cause load impedance to equal transmission line impedance. Feedback loop means are also provided to maintain net load power at an externally commanded level.

Claims17

Dependent claims

A system for supplying R.F. power to a load, comprising;

R.F. power source means,
load match circuit means connected between said R.F. power source means and the load,
said load match circuit means comprising;
first and second variable capacitors together with an inductance forming a tank circuit and first and second reversible stepping motors connected to said first and second variable capacitors, respectively, for varying the capacitance of each;
bi-directional coupler means connected between said R.F. power source means and said load match circuit means for providing voltage outputs proportional to forward and reflected power;
control circuit means connected to receive said outputs from said bi-directional coupler means proportional to forward and reflected power and connected to said load match circuit means for energizing said first and second motors to vary said first and second capacitors to cause apparent load impedance to automatically match the surge impedance of said transmission line means to reduce reflected power substantially to zero regardless of variations of load impedance,
said control circuit means comprising;
first circuit means connected to said first motor for driving said first motor in a first or second direction,
second circuit means connected to said second motor for driving said second motor in a first or second direction,
first logic circuit means connected to said first and second circuit means for driving said first and second motors only in a direction for reducing the voltage from said bi-directional coupler means proportional to said reflected power,
second logic circuit means connected to said first and second circuit means for periodically selecting one of said first and second motors to be energized,
a pulse generator providing first, second, third and fourth pulses periodically,
said second logic circuit comprising,
a first flip-flop connected to said first and second circuit means,
counter means connected between said generator means and said first flip-flop causing said first flip-flop to change states after said fourth pulse has occurred a predetermined number of times for selecting said first or second motors to be energized in accordance with the state of said first flip-flop.

12 more elements

A system for supplying R.F. power to a load, comprising;

R.F. power source means including an oscillator and a preamplifier,
bi-directional coupler means connecting said R.F. power source means to the load for passing substantially all the power from said R.F. power source to the load and having voltage outputs proportional to forward and reflected power,
feedback circuit means including summing means connected to said R.F. power source means and to said bi-directional coupler means to receive said voltage outputs,
input means providing an input to said summing means representative of the amount of desired R.F. power at the load to maintain power to the load at the power called for by said input means, said summing means comprising,
a summing point for receiving said voltage outputs and said input representative of desired R.F. load power,
a field effect transistor connected between said oscillator and said preamplifier and having a control electrode connected to said summing point,
power amplifier means connected between said preamplifier and said bi-directional coupler means,
d.c. power source means,
second means coupled between said d.c. power source means and said power amplifier and to said input means for controlling the amount of d.c. voltage delivered to said power amplifier in accordance with the amount of R.F. power called for by said input means.

6 more elements

Dependencies are inferred from the claim text.

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Abstract

A system for supplying R.F. power to a load, comprising;

R.F. power source means,
load match circuit means connected between said R.F. power source means and the load,
said load match circuit means comprising;
first and second variable capacitors together with an inductance forming a tank circuit and first and second reversible stepping motors connected to said first and second variable capacitors, respectively, for varying the capacitance of each;
bi-directional coupler means connected between said R.F. power source means and said load match circuit means for providing voltage outputs proportional to forward and reflected power;
control circuit means connected to receive said outputs from said bi-directional coupler means proportional to forward and reflected power and connected to said load match circuit means for energizing said first and second motors to vary said first and second capacitors to cause apparent load impedance to automatically match the surge impedance of said transmission line means to reduce reflected power substantially to zero regardless of variations of load impedance,
said control circuit means comprising;
first circuit means connected to said first motor for driving said first motor in a first or second direction,
second circuit means connected to said second motor for driving said second motor in a first or second direction,
first logic circuit means connected to said first and second circuit means for driving said first and second motors only in a direction for reducing the voltage from said bi-directional coupler means proportional to said reflected power,
second logic circuit means connected to said first and second circuit means for periodically selecting one of said first and second motors to be energized,
a pulse generator providing first, second, third and fourth pulses periodically,
said second logic circuit comprising,
a first flip-flop connected to said first and second circuit means,
counter means connected between said generator means and said first flip-flop causing said first flip-flop to change states after said fourth pulse has occurred a predetermined number of times for selecting said first or second motors to be energized in accordance with the state of said first flip-flop.

12 more elements