High frequency solid state switching for impedance matching
First Claim
1. A circuit of a variable capacitance element of an impedance matching network comprising:
- a capacitor coupled between a first voltage line and a first node;
a first diode having anode coupled to the first node and a cathode coupled to a second node;
a second diode having anode to couple to a second voltage line and a cathode to couple to the first node;
a transistor having a first, second, and control terminals, wherein;
the first terminal is coupled to the second node;
the second terminal is coupled to the second voltage line;
the control terminal is coupled to a controller; and
the capacitor is switched into the variable capacitance element when the transistor is on and switched out after the transistor is off.
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Abstract
In accordance with this invention the above and other problems are solved by a switching apparatus and method that uses a switching circuit having a pair of parallel solid-state diodes (e.g., PN diodes), one of which is connected to a transistor (e.g., power MOSFET or IGBT), to switch a capacitor in or out of a variable capacitance element of an impedance matching network. Charging a body capacitance of the transistor reverse biases one of the two diodes so as to isolate the transistor from the RF signal enabling a low-cost high capacitance transistor to be used. Multiple such switching circuits and capacitors are connected in parallel to provide variable impedance for the purpose of impedance matching.
66 Citations
27 Claims
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1. A circuit of a variable capacitance element of an impedance matching network comprising:
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a capacitor coupled between a first voltage line and a first node; a first diode having anode coupled to the first node and a cathode coupled to a second node; a second diode having anode to couple to a second voltage line and a cathode to couple to the first node; a transistor having a first, second, and control terminals, wherein; the first terminal is coupled to the second node; the second terminal is coupled to the second voltage line; the control terminal is coupled to a controller; and the capacitor is switched into the variable capacitance element when the transistor is on and switched out after the transistor is off. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A circuit of a variable capacitance element of an impedance matching network comprising:
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a capacitor coupled between a first voltage line and a first node; a first diode having anode coupled to the first node and a cathode coupled to a second node; a low power DC bias source providing a first DC bias to the first node via a second diode; a transistor having a first terminal, a second terminal, and a control terminal, wherein; the first terminal is coupled to the second node; the second terminal is coupled to a second voltage line; the control terminal receives signals controlling switching of the transistor; and the capacitor is switched into the variable capacitance element when the transistor is on and switched out after the transistor is off. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. A method of switching a capacitor in and out of a variable capacitance element of an impedance matching network, the method comprising:
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turning a transistor of the variable capacitance element off; charging a body capacitance of the transistor via a first diode using current from an RF signal passing through the capacitor; reverse biasing the first diode with a voltage supplied by the body capacitance of the transistor after charging; reducing the current from the RF signal through the capacitor to near zero amperes so as to reduce an impedance of the variable capacitance element; turning the transistor of the variable capacitance element on; discharging the body capacitance of the transistor; forward biasing the first diode with current from the RF signal passing through the capacitor; and increasing the current from the RF signal through the capacitor so as to increase the impedance of the variable capacitance element.
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Specification