Method and apparatus for impedance matching in an amplifier using lumped and distributed inductance
First Claim
1. An impedance matching circuit comprising:
- an input node adapted to receive an input signal from an amplifier circuit;
an output node adapted to couple an output signal to a transmission circuit;
a first capacitive element electrically coupled in parallel with said output node and having a capacitance C;
an inductor and a transmission line electrically coupled between and in series with the input node and the output node, said transmission line having a length selected in combination with the inductor to provide a predetermined amount of inductance, L;
wherein values of L and C provide an impedance substantially equal to an input impedance of the transmission circuit at a first frequency.
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Accused Products
Abstract
An impedance matching circuit (140) includes a capacitive element (C1, 220), having a capacitance C, coupled in parallel with an output node (215) of the matching circuit, and an inductor (L1, 225) coupled in series with a transmission line (T1, 230) between the input node and the output node. The transmission line has a length that, in combination with the inductor, provides impedance substantially equal to the input impedance of the transmission circuit (150) at a frequency of interest. In one embodiment, the inductor is connected to an output (195) of an amplifier (180), and the transmission line is connected to the inductor and to the output (215). The capacitive element is connected to the transmission line such that the length of the transmission line between the inductor and the capacitive element provides the desired inductance.
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Citations
22 Claims
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1. An impedance matching circuit comprising:
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an input node adapted to receive an input signal from an amplifier circuit;
an output node adapted to couple an output signal to a transmission circuit;
a first capacitive element electrically coupled in parallel with said output node and having a capacitance C;
an inductor and a transmission line electrically coupled between and in series with the input node and the output node, said transmission line having a length selected in combination with the inductor to provide a predetermined amount of inductance, L;
wherein values of L and C provide an impedance substantially equal to an input impedance of the transmission circuit at a first frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of matching an output impedance of an amplifier circuit to an input impedance of a transmission circuit, comprising:
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providing a series combination of an inductor and a transmission line coupled between and in series with an output of the amplifier circuit and an input of the transmission circuit, the transmission line having a length selected, in combination with the inductor, to provide a predetermined amount of inductance, L; and
electrically coupling a first capacitive element to an in parallel with the output of the amlifier circuit, the capacitive element having a capacitance C, so that L and C provide an impedance substantially equal to an input impedance of the transmission circuit at a first frequency. - View Dependent Claims (10, 11, 12, 13)
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14. A transceiver for use in a wireless communication system, the transceiver comprising:
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an amplifier circuit for amplifying signals transmitted by the transceiver;
a transmission circuit for transmitting signals transmitted by the transceiver, the transmission circuit including an antenna; and
an impedance matching circuit electrically coupled between and in series with an output of the amplifier circuit and an input of the transmission circuit, the impedance matching circuit comprising;
a first capacitive element electrically coupled to and in parallel with the output of the amplifier circuit, the capacitive element having a capacitance C;
a series combination of an inductor and a transmission line electrically coupled between and in series with the input of the transmission circuit and the output of the amplifier circuit, the transmission line having a length selected, in combination with the inductor, to provide a predetermined amount of inductance, L;
wherein L and C are selected to provide an impedance equal to the input impedance of the transmission circuit at a first frequency. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. An impedance matching circuit comprising:
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an input node for receiving an input signal from an amplifier circuit;
an output node for coupling an output signal to a transmission circuit;
a capacitive element electrically coupled in parallel with said output node and having a capacitance C;
an inductor and a transmission line electrically coupled between and in series with the input node and the output node, the transmission line having a length selected in combination with the inductor to provide a predetermined amount of inductance, L, values of L and C being selected to provide in impedance substantially equal to an input impedance of the transmission circuit at a frequency;
said inductor having a first end electrically connected to said input node and a second end electrically connected to the transmission line, said transmission line having a first end electrically connected to the second end of the inductor and a second end electrically connected to the output node of the impedance matching circuit, and the capacitive element being electrically connected to the transmission line such that the length of the transmission line between the second end of the inductor and the capacitive element is selected to, in combination with the inductor, provide the predetermined amount of inductance;
wherein the transmission line comprises a conductor over a ground plane on a printed circuit board in the form of a co-planar grounded waveguide, the capacitive element being mounted on the printed circuit board, and the capacitive element comprising a shorted waveguide electrically connected to the transmission line.
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22. A method of matching an output impedance of an amplifier circuit to an input impedance of a transmission circuit, comprising:
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providing a series combination of an inductor and a transmission line coupled between and in series with an output of the amplifier circuit and an input of the transmission circuit, the transmission line having a length selected, in combination with the inductor, to provide a predetermined amount of inductance, L, the transmission line comprising a conductor over a ground plane on a printed circuit board;
electrically coupling a first capacitive element to and in parallel with the output of the amplifier circuit, the capacitive element having a capacitance C, so that L and C provide an impedance substantially equal to an input impedance of the transmission circuit at a frequency;
the inductor having a first end connected to an output of the amplifier circuit and a second end connected to the transmission line, and the transmission line having a first end connected to the second end of the inductor and a second end connected to the impedance matching circuit, wherein the first capacitive element is electrically connected to the transmission line such that the length of the transmission line between the second end of the inductor and the first capacitive element is selected to, in combination with the inductor, provide the predetermined amount of inductance;
mounting the first capacitive element on the printed circuit board such that a first end of the capacitive element is electrically connected to the conductor of the transmission line and a second end of the first capacitive element is electrically connected to the ground plane;
electrically connecting a second capacitive element to the transmission line in parallel with the first capacitive element such that the length of the transmission line between the second end of the inductor and the second capacitive element is selected to, in combination with the inductor, provide a second predetermined amount of inductance, L′
, L′ and
C providing an impedance substantially equal to the input impedance of the transmission circuit at a second frequency; and
electrically coupling the second capacitive element to the ground plane and electrically decoupling the first capacitive element from the ground plane through a single pole double throw switch capable of alternately electrically decoupling the first and second capacitive elements from the ground plane.
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Specification