US 8,283,991 B1 · Wideband, differential signal balun for rejecting common mode electromagnetic fields

Abstract

Provided are assemblies and processes for efficiently coupling wideband differential signals between balanced and unbalanced circuits. The assemblies include a broadband balun having an unbalanced transmission line portion, a balanced transmission line portion, and a transition region disposed between the unbalanced and balanced transmission line portions. The unbalanced transmission line portion includes at least one ground and a pair of conductive signal traces, each isolated from ground. The balanced portion does not include an analog ground. The transition region effectively terminates the analog ground, while also smoothly transitioning or otherwise shaping transverse electric field distributions between the balanced and unbalanced portions. Beneficially, the balun is free from resonant features that would otherwise limit operating bandwidth, allowing it to operate over a wide bandwidth of 10:1 or greater. Assemblies can include RF chokes with back-to-back baluns, and other elements, such as balanced filters, and also be implemented as integrated circuits.

Claims18

Dependent claims

A broadband balun, comprising:

an unbalanced transmission line portion, including a first in-phase trace extending along a longitudinal axis, a first anti-phase trace extending parallel to the first trace, and at least one ground plane parallel to, electromagnetically coupled with, and physically isolated from each of the first in-phase and anti-phase traces;
a balanced transmission line portion, the balanced transmission line portion including a second in-phase trace in electrical communication with the first in-phase trace, and a second anti-phase trace in electrical communication with first anti-phase trace, each of the second in-phase and anti-phase traces vertical parallel plates (or co-planar) with its respective first in-phase and anti-phase traces and substantially uncoupled to the at least one ground plane;
and
a transition region disposed between the unbalanced transmission line portion and the balanced transmission line portion, the transition region comprising a respective terminal edge defining a boundary of each of the at least one ground planes between the unbalanced and balanced transmission line portions and a ground plane edge variation extending along the longitudinal axis for a predetermined length measured from the respective terminal edge, wherein respective cross sections of each of the unbalanced, balanced and transition regions are substantially symmetric with respect to the longitudinal axis.

1 more element

Dependencies are inferred from the claim text.

Wideband, differential signal balun for rejecting common mode electromagnetic fields

Life of this patent

Wideband, differential signal balun for rejecting common mode electromagnetic fields

Life of this patent

Abstract

Claims18