Integrated transformer balun with enhanced common-mode rejection for radio frequency, microwave, and millimeter-wave integrated circuits
First Claim
1. A transformer balun, comprising:
- a first winding of at least one turn forming a primary coil, having first and second differential leads oriented in a first direction and connected at a center tap of the primary coil, the primary coil formed in a first conductive layer over a substrate and the first differential lead of the primary coil being grounded, the second differential lead providing a first terminal of the balun; and
a second winding of at least one turn forming a secondary coil, having a third and fourth differential leads providing second terminals of the balun, oriented in a second direction offset by an angle of substantially ninety degrees from the first direction and connected at a center tap of the secondary coil, the secondary coil formed in a second conductive layer separated by an insulating layer from the first conductive layer, the first and second windings capacitively and inductively coupled forming an equivalent return-path inductance in both the third and fourth differential leads of the balun;
wherein the primary coil and the secondary coil form a transformer balun wherein having;
the first differential lead of the primary coil being a half-coil with a second segment and a fourth segment, that are substantially grounded and the second differential lead of the primary coil being a half-coil with a first segment and a third segment, that are a substantially higher impedance and provide the first terminal of the balun;
the third differential lead of the secondary coil being a half-coil with a third segment parallel to and capacitively and inductively coupling with the higher impedance third segment of the primary coil, and a fourth segment parallel to and capacitively and inductively coupling with the grounded fourth segment of the primary coil, the third differential lead providing a first one of the second terminals of the balun;
the fourth differential lead of the secondary coil being a half-coil with first segment parallel to and capacitively and inductively coupling with the higher impedance first segment of the primary coil, and a second segment parallel to and capacitively and inductively coupling with the grounded second segment of the primary coil, the fourth differential lead providing a second one of the second terminals of the balun;
whereby aggregate impedances in the third differential lead and in the fourth differential lead of the secondary coil are substantially equivalent, to maximize common mode rejection.
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Abstract
Apparatus and method example embodiments provide an improved common mode rejection ratio in high frequency transformer baluns. According to an example embodiment of the invention, an apparatus comprises a first winding of at least one turn forming a primary coil, having first and second differential leads oriented in a first direction, the primary coil formed in a first conductive layer over a substrate and the first differential lead of the primary coil being grounded; and a second winding of at least one turn forming a secondary coil, having a third and fourth differential leads oriented in a second direction offset by an angle of greater than zero degrees and less than 180 degrees from the first direction, the secondary coil formed in a second conductive layer separated by an insulating layer from the first conductive layer.
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Citations
13 Claims
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1. A transformer balun, comprising:
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a first winding of at least one turn forming a primary coil, having first and second differential leads oriented in a first direction and connected at a center tap of the primary coil, the primary coil formed in a first conductive layer over a substrate and the first differential lead of the primary coil being grounded, the second differential lead providing a first terminal of the balun; and a second winding of at least one turn forming a secondary coil, having a third and fourth differential leads providing second terminals of the balun, oriented in a second direction offset by an angle of substantially ninety degrees from the first direction and connected at a center tap of the secondary coil, the secondary coil formed in a second conductive layer separated by an insulating layer from the first conductive layer, the first and second windings capacitively and inductively coupled forming an equivalent return-path inductance in both the third and fourth differential leads of the balun; wherein the primary coil and the secondary coil form a transformer balun wherein having; the first differential lead of the primary coil being a half-coil with a second segment and a fourth segment, that are substantially grounded and the second differential lead of the primary coil being a half-coil with a first segment and a third segment, that are a substantially higher impedance and provide the first terminal of the balun; the third differential lead of the secondary coil being a half-coil with a third segment parallel to and capacitively and inductively coupling with the higher impedance third segment of the primary coil, and a fourth segment parallel to and capacitively and inductively coupling with the grounded fourth segment of the primary coil, the third differential lead providing a first one of the second terminals of the balun; the fourth differential lead of the secondary coil being a half-coil with first segment parallel to and capacitively and inductively coupling with the higher impedance first segment of the primary coil, and a second segment parallel to and capacitively and inductively coupling with the grounded second segment of the primary coil, the fourth differential lead providing a second one of the second terminals of the balun; whereby aggregate impedances in the third differential lead and in the fourth differential lead of the secondary coil are substantially equivalent, to maximize common mode rejection. - View Dependent Claims (2, 3, 4)
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5. A method, comprising:
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forming, with an apparatus, a primary coil of a balun, of at least one turn in a first conductive layer over a substrate, the primary coil having first and second differential leads oriented in a first direction and connected at a center tap of the primary coil and the first differential lead of the primary coil being grounded, the second differential lead providing a first terminal of the balun; and forming, with an apparatus, a secondary coil of the balun, of at least one turn in a second conductive layer separated by an insulating layer from the first conductive layer, the secondary coil having a third and fourth differential leads providing second terminals of the balun, oriented in a second direction offset by an angle of substantially ninety degrees from the first direction and connected at a center tap of the secondary coil, the primary and secondary coils capacitively and inductively coupled forming an equivalent return-path inductance in both the third and fourth differential leads of the balun; wherein the primary coil and the secondary coil form a transformer balun having; the first differential lead of the primary coil being a half-coil with a second segment and a fourth segment, that are substantially grounded and the second differential lead of the primary coil being a half-coil with a first segment and a third segment, that are a substantially higher impedance and provide the first terminal of the balun; the third differential lead of the secondary coil being a half-coil with a third segment parallel to and capacitively and inductively coupling with the higher impedance third segment of the primary coil, and a fourth segment parallel to and capacitively and inductively coupling with the grounded fourth segment of the primary coil, the third differential lead providing a first one of the second terminals of the balun; the fourth differential lead of the secondary coil being a half-coil with first segment parallel to and capacitively and inductively coupling with the higher impedance first segment of the primary coil, and a second segment parallel to and capacitively and inductively coupling with the grounded second segment of the primary coil, the fourth differential lead providing a second one of the second terminals of the balun; whereby aggregate impedances in the third differential lead and in the fourth differential lead of the secondary coil are substantially equivalent, to maximize common mode rejection. - View Dependent Claims (6, 7, 8, 9)
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10. A transformer balun, comprising:
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a first winding of at least one turn forming a first coil, having first and second differential leads oriented in a first direction and connected at a center tap of the first coil, the first coil formed in a first conductive layer over a substrate and the first differential lead of the first coil being grounded, the second differential lead providing a first terminal of the balun; and a second winding of at least one turn forming a second coil, having a third and fourth differential leads providing second terminals of the balun, oriented in a second direction offset by an angle of substantially ninety degrees from the first direction and connected at a center tap of the second coil, the second coil formed in a second conductive layer separated by an insulating layer from the first conductive layer, the first and second windings capacitively and inductively coupled forming an equivalent return-path inductance in both the third and fourth differential leads of the balun; wherein the first coil and the second coil form a transformer balun wherein having; the first differential lead of the first coil being a half-coil with a second segment and a fourth segment, that are substantially grounded and the second differential lead of the first coil being a half-coil with a first segment and a third segment, that are a substantially higher impedance and provide the first terminal of the balun; the third differential lead of the second coil being a half-coil with a third segment parallel to and capacitively and inductively coupling with the higher impedance third segment of the first coil, and a fourth segment parallel to and capacitively and inductively coupling with the grounded fourth segment of the first coil, the third differential lead providing a first one of the second terminals of the balun; the fourth differential lead of the second coil being a half-coil with first segment parallel to and capacitively and inductively coupling with the higher impedance first segment of the first coil, and a second segment parallel to and capacitively and inductively coupling with the grounded second segment of the first coil, the fourth differential lead providing a second one of the second terminals of the balun; whereby aggregate impedances in the third differential lead and in the fourth differential lead of the second coil are substantially equivalent, to maximize common mode rejection. - View Dependent Claims (11, 12, 13)
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Specification