Monolithic wideband trifilar transformer
Transformers that provide impedance transformations within integrated circuits (ICs) are disclosed. Embodiments of the transformers may include a plurality of conductors connected in series within one another wherein the conductors are arranged to form transmission lines. A first port, a second port, and a third port are coupled to the conductors so that impedance transformations can be provided between the first port and the second port. Some embodiments of the transformers are arranged so that the third port can be used to apply a bias signal. The arrangement between the conductors and the ports allows the transformer to provide impedance transformations between the first port and the second port over a relatively wide passband at high frequency ranges and with relatively small insertion losses.
1. A transformer comprising:
a first conductor;
a second conductor connected in series with the first conductor wherein the first conductor and the second conductor are disposed so as to operate in a waveguide mode such that a radiated magnetic field and/or electric field from the first conductor and the second conductor field couple the first conductor and the second conductor and form a first transmission line;
a third conductor connected in series with the second conductor wherein the second conductor and the third conductor are disposed so as to operate in a waveguide mode such that a radiated magnetic field and/or electric field from the second conductor and the third conductor field couple the second conductor and the third conductor and form a second transmission line;
a first port coupled so as to provide an intermediary tap to the first transmission line;
a second port coupled to the first conductor; and
a third port coupled to the third conductor, wherein the first conductor, the second conductor, and the third conductor define a conductive path between the second port and the third port such that the first conductor, second conductor, and third conductor are connected in series within the conductive path;
at least a portion of the first conductor is connected between the first port and the second port;
the first transmission line is provided such that the first conductor and the second conductor are in a bootstrap arrangement;
the second conductor and the third conductor are connected in series between the first port and the third port so that the second transmission line provides the second conductor and the third conductor in a common mode choke arrangement; and
the transformer is configured to provide an impedance transformation that transforms a low impedance presented at the first port to a higher impedance at the second port.
2. The transformer of claim 1 wherein the first conductor, the second conductor, and the third conductor define the conductive path between the second port and the third port such that the first conductor, second conductor, and third conductor are connected in series within the conductive path.
3. The transformer of claim 2 wherein:
the first conductor defines a first end of the conductive path;
the second conductor is connected between the first conductor and the third conductor;
the third conductor defines a second end of the conductive path oppositely disposed to the first end of the conductive path;
at least a portion of the first conductor is connected between the first port and the second port;
the second port is coupled to the first end of the conductive path; and
the third port is coupled to the second end of the conductive path.
4. The transformer of claim 3 wherein the first port is connected so as to provide the intermediary tap to the first conductor such that less than a whole portion of the first conductor is connected between the first port and the second port.
5. The transformer of claim 3 wherein the first port is coupled so as to provide the intermediary tap between the first conductor and the second conductor such that a whole portion of the first conductor is connected between the first port and the second port.
6. The transformer of claim 3 further comprising a capacitive element connected in series between the first end of the conductive path and the second port.
7. The transformer of claim 3 further comprising a capacitive element connected in shunt between the third port and the second end of the conductive path.
8. The transformer of claim 3 wherein the second conductor and the third conductor are connected in series within a path that is connected in shunt with respect to the first port.
9. The transformer of claim 1 wherein the first conductor, the second conductor, and the third conductor are arranged so that the transformer is a bias Tee wherein the first port is a low impedance port, the second port is a high impedance port and the third port is a bias port.
10. The transformer of claim 1 whereby the transformer is further configured to provide an impedance transformation that transforms a higher impedance presented at the second port to a lower impedance at the first port.
11. The transformer of claim 1 wherein the transformer is a monolithic microwave integrated circuit (MMIC) integrated into a semiconductor substrate.
12. The transformer of claim 1 wherein:
the first conductor is a first winding;
the second conductor is a second winding; and
the third conductor is a third winding.
13. The transformer of claim 12 wherein the first winding, the second winding, and the third winding form a planar coil such that the first winding is an outermost winding, the third winding is an innermost winding, and the second winding is an intermediate winding connected between the first winding and the third winding.
14. The transformer of claim 13 wherein the first winding and the second winding are edge coupled so as to provide the first transmission line.
15. The transformer of claim 14 wherein the second winding and the third winding are edge coupled so as to provide the second transmission line.
16. The transformer of claim 12 wherein:
the first winding defines a first end and a second end, wherein the first end is coupled to the second port and the second end is connected to the second winding; and
the first port comprises a terminal connected to an outermost edge of the first winding such that the first port provides an intermediary tap to the first winding so that a portion of the first winding is connected between the first port and the second port.
17. The transformer of claim 14 further comprising a first Metal Insulator Metal (MIM) capacitive element and a second MIM capacitive element wherein:
the first MIM capacitive element is connected in series between the first end and the second port;
the second winding defines a third end that is connected to the second end of the first winding and a fourth end;
the third winding defines a fifth end connected to the fourth end of the second winding and a sixth end connected to the third port; and
the second MIM capacitive structure is connected to the sixth end and in shunt with respect to the third port.
18. The transformer of claim 12 further comprising a grounding plate wherein:
the first winding defines a first end and a second end, wherein the first end is directly connected to the second port and the second end is connected to the second winding;
the first port is connected to the second end of the first winding so that the first winding is connected between the first port and the second port;
the second winding defines a third end that is connected to the second end of the first winding and a fourth end;
the third winding defines a fifth end connected to the fourth end of the second winding and a sixth end connected to the third port; and
the grounding plate is connected in shunt with respect to the sixth end and to the third port.