Balun phase and amplitude imbalance correction
In one example, an apparatus comprises: a first metal layer including a first segment and a second segment, in which the first segment is electrically coupled to a single-ended signal terminal, the second segment has a disconnected end; a second metal layer including a third segment and a fourth segment, in which the third segment is magnetically coupled to the first segment, the fourth segment is magnetically coupled to the second segment, a first end of the third segment and a first end of the fourth segment are electrically coupled at a center tap, and a second end of the third segment and a second end of the fourth segment are electrically coupled to respective first and second signal terminals of a pair of differential signal terminals; and a phase adjustment device proximate the center tap and electrically coupled to a second voltage reference terminal.
1 . An apparatus comprising:
a first metal layer including a first segment and a second segment, in which the first segment is coupled to a first signal terminal, the second segment has a disconnected end;
a second metal layer including a third segment and a fourth segment, in which the third segment extends along the first segment, the fourth segment extends along the second segment, a first end of the third segment and a first end of the fourth segment are electrically coupled at a center tap, and a second end of the third segment and a second end of the fourth segment are coupled to a second signal terminal and a third signal terminal;
a via at the center tap and coupled to a first reference terminal; and
a device extending along at least one of: a first subsegment of the third segment overlapping at least partially with the first signal terminal or a second subsegment of the fourth segment overlapping at least partially with the disconnected end of the second segment, the device coupled to a second reference terminal.
2 . The apparatus of claim 1 , wherein the device includes a metal strip on a side of the one of the first or second subsegments.
3 . The apparatus of claim 2 , further comprising a third metal layer enclosing the first, second, third, and fourth segments;
wherein the third metal layer is electrically coupled to the first or second reference terminal; and
wherein the device is coupled between the third metal layer and the one of the first or second subsegments.
4 . The apparatus of claim 3 , wherein the third metal layer is part of a Faraday cage.
5 . The apparatus of claim 3 , wherein:
the via is a first via;
the apparatus further includes a second via external to the first and second metal layers, the second via coupled to the first or second reference terminal; and
the metal strip extends from one of the first or second subsegments to the second via.
6 . The apparatus of claim 3 , wherein the metal strip is a first metal strip on a side of the first subsegment; and
wherein the apparatus includes a second metal strip on a side of the second subsegment, the second metal strip coupled to the third metal layer.
7 . The apparatus of claim 6 , wherein the apparatus includes a third metal strip on a side of the via, the third metal strip coupled to the third metal layer.
8 . The apparatus of claim 1 , wherein:
the via is a first via;
the apparatus further includes a stack of metal layers including the first and second metal layers, and a third metal layer over or below the second metal layer, the third metal layer electrically coupled to the first or second reference terminal; and
the device includes second vias coupled between the third metal layer and the one of the first or second subsegments, the second vias positioned along the one of the first or second subsegments.
9 . The apparatus of claim 1 , further comprising:
a first metal wire coupled between the second end of the third segment and the first signal terminal;
a second metal wire coupled between the second end of the fourth segment and the second signal terminal;
a first metal shield layer over the first metal wire, in which the first metal shield layer includes first metal teeth extending therefrom and having respective first widths; and
a second metal shield layer over the second metal wire, in which the second metal shield layer includes second metal teeth extending therefrom and having respective second widths, the second widths are smaller than the first widths, and the second metal teeth are coupled to the first metal teeth over the first and second metal wires.
10 . The apparatus of claim 9 , wherein adjacent first metal teeth are separated by a first distance;
wherein adjacent second metal teeth are separated by a second distance; and
wherein the first distance is shorter than the second distance.
11 . The apparatus of claim 9 , further comprising:
a third metal layer over the first and second metal layers;
a fourth metal layer below the first and second metal layers; and
vias coupled between the third metal layer and the fourth metal layer,
wherein the first and second metal shield layers are part of the third metal layer, and the fourth metal layer is coupled to the first or second reference terminal.
12 . The apparatus of claim 1 , further comprising a third metal layer over the first and second metal layers, in which the third metal layer is coupled to the first or second reference terminal,
wherein the third metal layer includes first metal strips that overlap at least partially with the third segment and second metal strips that overlap at least partially with the fourth segment.
13 . The apparatus of claim 12 , wherein the third metal layer further includes a third metal strip that overlaps at least partially with: the via; the first and second ends of the third segment; and the first and second ends of the fourth segment.
14 . The apparatus of claim 13 , wherein:
the first metal strips extend from a first side of the third metal strip; and
the second metal strips extend from a second side of the third metal strip, the second side being opposite to the first side.
15 . The apparatus of claim 14 , further comprising fourth metal strips and fifth metal strips,
wherein the fourth metal strips extend from the first side and do not overlap with the third segment, and the fifth metal strips extend from the second side and do not overlap with the fourth segment.
16 . The apparatus of claim 12 , wherein:
the first metal strips have respective first widths, and adjacent first metal strips are separated by a first distance; and
the second metal strips have respective second widths different from the first widths, and adjacent second metal strips are separated by a second distance different from the first distance.
17 . The apparatus of claim 12 , wherein the third metal layer includes a shield layer, the shield layer being part of a shield structure that surrounds the first, second, third, and fourth segments, the shield structure being adapted to be electrically coupled to the first or second reference terminal; and
wherein the first and second metal strips are electrically coupled to the shield layer.
18 . The apparatus of claim 1 , wherein the first and second metal layers form a stack of metal layers.
19 . The apparatus of claim 1 , wherein the first and second metal layers, the via, and the device are part of a package of an integrated circuit.
20 . The apparatus of claim 1 , wherein the first and second metal layers, the via, and the device are on a semiconductor substrate of an integrated circuit.
21 . The apparatus of claim 1 , wherein the first and second metal layers, the via, and the device are part of a printed circuit board (PCB).
22 . The apparatus of claim 1 , wherein:
the first segment is configurable to transmit a first signal to the second segment;
the second segment is configurable to transmit the first signal to the disconnected end and transmit a second signal from a reflection of the first signal at the disconnected end;
the third segment is configurable to transmit a third signal responsive to the first signal propagating in the first segment and responsive to a magnetic coupling between the first and third segments;
the fourth segment is configurable to transmit a fourth signal responsive to the second signal propagating in the second segment and responsive to a magnetic coupling between the second and fourth segments; and
the device is configurable to adjust at least one of: (a) a first phase relationship between the first signal in the first segment and the third signal in the third segment; or (b) a second phase relationship between the second signal in the second segment and the fourth signal in the fourth segment.
23 . The apparatus of claim 22 , wherein a length of the first subsegment or the second subsegment is based on a frequency of the first signal.
24 . The apparatus of claim 1 , wherein the first and second metal layers and the via are part of a balun.
25 . The apparatus of claim 1 , wherein the first signal terminal is a single-ended signal terminal, and the second and third signal terminals are differential signal terminals.
26 . The apparatus of claim 1 , wherein the first and second reference terminals are coupled together.
27 . An apparatus comprising:
a balun including:
a first metal segment coupled between a first signal terminal and a disconnected end; and
a second metal segment coupled between a second signal terminal and a third signal terminal, the second metal segment having a center tap coupled to a first reference terminal; and
a device overlapping at least partially with the first signal terminal or the disconnected end but not the second and third signal terminals and coupled to a second reference terminal.
28 . The apparatus of claim 27 , wherein the device includes at least one of: a metal strip, or a set of vias.