Inductor devices – Coil or coil turn supports or spacers – Printed circuit-type coil
Reexamination Certificate
2002-07-23
2004-03-16
Nguyen, Tuyen T. (Department: 2832)
Inductor devices
Coil or coil turn supports or spacers
Printed circuit-type coil
C336S232000, C257S531000
Reexamination Certificate
active
06707367
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
This invention relates generally to radio communication technology and more particularly to transformers used within the radio communication technology.
2. Description of Related Art
Two-way radios, which may be incorporated in wireless communication devices, are known to include an antenna, a transformer, an antenna switch, a receiver section, and a transmitter section. The antenna switch couples either the receiver section or the transmitter section to the antenna via the transformer. The transformer may be a transformer balun (balanced/unbalanced) and is generally used to convert single ended signals into differential signals and conversely to convert differential signals into single ended signals. For example, received RF signals via the antenna are converted into differential signals, which are provided to a low noise amplifier of the receiver section. Conversely, differential signals from a power amplifier of the transmitter section are converted into single ended signals, which are provided to the antenna.
As the demand for integrated circuit radios increases, many attempts have been made to integrate transformers and/or transformer baluns onto radio frequency integrated circuits. However, such integration has been limited due to flux leakage, capacitive coupling limits, and significant series resistance. To reduce these limitations, advances have been made in transformer IC design including coplanar interleaved transformers, toroidal and concentric transformers, overlay transformers and symmetric coplanar transformers. Coplanar interleaved transformers have the primary and secondary windings interleaved on the same integrated circuit layer, where the primary and secondary windings are constructed of planer metal traces. While coplanar interleaved transformers reduces size and resistance and are widely used, they suffer from how quality (Q) factor, small coupling coefficients, and, if used as a balun, the center tap is often at an undesirable location, resulting in an asymmetric geometry. As is known, asymmetry of a transformer winding causes an imbalance in the resulting differential signal and/or an imbalance in the resulting single ended signal from a differential signal.
Toroidal and concentric transformers have the primary and secondary windings on several dielectric layers of an integrated circuit. Each layer includes one or more primary and secondary turns, where turns on different layers are coupled in series using vias. Each of the primary turns, on each layer, is constructed around the secondary turns on the same layer. While such toroidal and concentric transformers are well suited for multi-layer structures, they suffer from weak coupling, inconvenient center tap locations, and are asymmetrical.
Overlay transformers include a primary spiral inductor on a top layer and a secondary spiral inductor on a lower layer. Such transformers have high coupling coefficients and relatively small area; however, the secondary is asymmetrical creating a loading asymmetry.
Symmetric coplanar transformers include the primary and secondary windings on the same layer with interconnecting bridges on lower layers. While such transformers have high symmetry, they have weak magnetic coupling and are usually large for desirable inductor values.
While each of these various embodiments of on-chip transformers have utility and certain applications they do not provide multiple uses for various applications. Therefore, a need exists for a multi-use on-chip transformer that is small, provides reasonable inductance values, has a high quality factor, reduces resistance and has a high coupling coefficient.
BRIEF SUMMARY OF THE INVENTION
The on-chip multiple tap transformer and inductor of the present invention substantially meets these needs and others. One embodiment of an on-chip multiple tap transformer balun in accordance with the present invention includes a 1
st
winding and a 2
nd
winding having two portions. The 1
st
winding is on a 1
st
layer of an integrated circuit and is operably coupled for a single ended signal. The 1
st
and 2
nd
portions of the 2
nd
winding are on a 2
nd
layer of the integrated circuit. The 1
st
portion of the 2
nd
winding includes a 1
st
node, a 2
nd
node, and a tap. The 1
st
node is operably coupled to receive a 1
st
leg of a 1
st
differential signal and the 2
nd
node is coupled to a reference potential. The tap of the 1
st
portion is operably coupled for a 1
st
leg of a 2
nd
differential signal. The 2
nd
portion of the 2
nd
winding includes a 1
st
node, a 2
nd
node, and a tap. The 1
st
node is operably coupled to receive a 2
nd
leg of the 1
st
differential signal and the 2
nd
node is operably coupled to the reference potential. The tap of the 2
nd
portion is coupled for a 2
nd
leg of the 2
nd
differential signal. The 1
st
and 2
nd
portions of the 2
nd
winding are symmetrical with respect to the 1
st
and 2
nd
nodes and with respect to the tap nodes. Such an on-chip multiple tap transformer balun may be used to convert single ended signals into one or more differential signals. Further, the on-chip multiple tap transformer balun may be used to convert one or more differential signals into a single ended signal.
Another embodiment of a multi-tap differential inductor in accordance with the present invention includes a 1
st
winding and a 2
nd
winding. The 1
st
winding is on a 1
st
layer of an integrated circuit and is coupled for a single ended signal. The 2
nd
winding is on a 2
nd
layer of the integrated circuit and is coupled to receive 1
st
and 2
nd
differential signals. To receive such differential signals, the 2
nd
winding includes 1
st
and 2
nd
nodes that are coupled to receive the 1
st
differential signal and 1
st
and 2
nd
taps to receive the 2
nd
differential signal. A 3
rd
tap of the secondary is coupled to a reference potential. The 2
nd
winding is symmetrical about the 3
rd
tap to produce a symmetrical on-chip multi-tap transformer balun.
An embodiment of an on-chip multi-tap differential inductor includes a 1
st
winding and a 2
nd
winding. Each winding is on the same layer of an integrated circuit. The 1
st
winding includes a 1
st
node that is coupled to receive a 1
st
leg of a differential signal and a 2
nd
node coupled to a reference potential. The 1
st
winding also includes a tap that is operably coupled to receive a 1
st
leg of a 2
nd
differential signal. The 2
nd
winding includes a 1
st
node coupled to receive a 2
nd
leg of the 1
st
differential signal and a 2
nd
node coupled to the reference potential. The 2
nd
winding further includes a tap operably coupled for a 2
nd
leg of the 2
nd
differential signal. The 2
nd
winding is substantially symmetrical to the 1
st
winding and the tap of the 1
st
winding is substantially symmetrical to the tap of the 2
nd
winding.
The various embodiments of multiple tap differential transformer baluns and differential inductors provide for multiple uses in various applications including radio frequency integrated circuits. By including one or more sets of taps, an on-chip multi-tap transformer balun or inductor, the transformer or inductor may be used in a variety of different manners, which may correspond to different operating frequencies, different desired inductancies, different transformer ratios, et cetera.
REFERENCES:
patent: 6476704 (2002-11-01), Goff
patent: 6577219 (2003-06-01), Visser
patent: 6580334 (2003-06-01), Simburger et al.
patent: 6608364 (2003-08-01), Carpentier
“RF Microelectronoics” by Behzad Razavi, University of California, Los Angeles; Prentice Hall Communications Engineering and Emerging Technologies Series, Theodore S. Rappaport Series Editor (Section 7.6-Monolithic Inductors), no date.
“Monolithic Transformers for Silicon RF IC Design” by John R. Long, Member IEEE; IEEE Journal of Solid-State Circuits, vol. 35, No. 9, Sep. 2000.
Long, “Monolithic transformers for silicon RFIC Design”, IEEE Journal of Solid-State Circuits, vol. 35, pp. 1368-1381, Se
Bhatti Iqbal S.
Castaneda Jesus A.
Rogougaran Razieh
Yang Hung Yu
Broadcom Corp.
Markison Timothy W.
Nguyen Tuyen T.
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