A balun is a circuit transformer that combines two out-of-phase signals into a common port, or splits the common signal into two out-of-phase signals. Baluns are utilized for antenna feeds, high-efficiency amplifier techniques, and broadband 2nd-order cancellation. Previous attempts of baluns, generally, have a limited bandwidth, typically 3:1. For printed-circuit type applications, a Marchand balun is widely used with bandwidths of 3:1 having been demonstrated. However, current high frequency baluns, including the Marchand Balun, have high insertion loss and do not operate effectively at high frequencies.
Therefore, a need exists in the art for a broadband balun with the features as described herein.
One approach to a broadband balun includes an un-balanced line, a balanced line, a double-y transition section, a first connection section, and a second connection section. The un-balanced line includes a ground trace and a signal trace. The balanced line includes a first and second signal trace. The double-y transition section includes a first slot trace and a second slot trace. The first slot trace couples the ground trace of the un-balanced line to the first signal trace of the balanced line. The second slot trace couples the signal trace of the un-balanced line to the second signal trace of the balanced line. The first connection section couples the first slot trace of the double-y transition section to the first signal trace of the balanced line. The second connection section couples the second slot trace of the double-y transition section to second signal trace of the balanced line.
Another approach to a broadband balun is a balun circuit. The circuit includes an un-balanced line, a balanced line, a double-y transition slotline, a first connection section, and a second connection section. The un-balanced line includes a first center conductor and first and second coplanar conductors. The balanced line includes a second center conductor and third and fourth coplanar conductors. The double-y transition slotline includes a first conductor and a second conductor. The first conductor couples the first center conductor to the third and fourth coplanar conductors. The second conductor couples the first and second coplanar conductors to the second center conductor. The first connection line couples the first conductor to the third and fourth coplanar conductors. The second connection line couples the first and second coplanar conductors to the second center conductor.
In other examples, any of the approaches above can include one or more of the following features.
In some examples, the un-balanced line includes an un-balanced coplanar waveguide (CPW) line.
In other examples, the balanced line includes a balanced coplanar waveguide (CPW) line.
In some examples, the double-y transition section includes a coupled slotline.
In other examples, the coupled slotline includes first and second conductors mounted on a substrate.
In other examples, the first signal trace is a center conductor of the balanced line.
In some examples, the first connection section includes a first metal interconnection and the second connection section includes a second metal interconnection.
In other examples, the first connection section includes a first microstrip and the second connection section includes a second microstrip.
In some examples, power input into the un-balanced line and power output from the balanced line is substantially the same.
In other examples, the first connection line includes a first metal interconnection and the second connection line includes a second metal interconnection.
In some examples, the first connection line includes a first microstrip and the second connection line includes a second microstrip.
The technology described herein can provide one or more of the following advantages. The technology advantageously has, at least, a 72:1 bandwidth on a monolithic microwave integrated circuit (MMIC) and enables easy integration in a standard MMIC fabrication process, thereby reducing the manufacturing cost of the broadband balun and increasing the effectiveness of the signal transformation. The technology advantageously has a low insertion loss, is compact compared to alternative solutions, and is less expensive than alternative solutions to manufacture.
The foregoing and other objects, features and advantages will be apparent from the following more particular description of the embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiments.
As a general overview of the technology, a broadband balun is a stand-alone 180 degree power splitter. The balun, as described herein, operates in the broadband frequency range. The balun has, for example, a 72:1 bandwidth, with low loss and is implemented utilizing standard monolithic microwave integrated circuit (MMIC) processing technology. This technology provides a broadband, low-loss, compact structure that is easily integrated in MMIC or board processing where baluns are utilized.
The technology includes a double-y transition and a coplanar waveguide (CPW). The double-y transition achieves broadband performance and converts the CPW to a slotline and vice versa. The technology can further include a coplanar waveguide (CPW)-T to convert the slotline (e.g., coplanar stripline (CPS) fields) from the double-y transition, thereby providing the low-loss broadband balun as described herein.
An advantage of the double-y transition is that the fine lithography of MMIC fabrication technology enables a double-y transition to operate at high frequencies with low loss, thereby increasing the efficiency of the technology. An advantage of the use of the CPW-T is that the CPW-T enables the balun to have a small size, thereby enabling the balun to operate at high frequencies without a large physical size. An advantage of the MMIC fabrication technology of the balun enables the ground-plane to be positioned close to the other components of the balun, thereby enabling the balun to be efficiently utilized in high-frequency applications by reducing the time for transformation of the electrical signals while reducing interface between the electrical signals.
The conductor 122 of the double-y transition slotline 120 couples the signal potential at conductor 122, which is electromagnetically coupled to the center conductor 112 of the un-balanced line 110, to the coplanar conductors 133 and 134 and to the center conductor 132 of the balanced line 130. The conductor 124 of the double-y transition slotline 120 couples the signal potential at conductor 124, which is electromagnetically coupled to the two coplanar conductors 111 and 116 of the un-balanced line 110, to the coplanar conductors 135 and 136 and to the center conductor 131 of the balanced line 130.
The balanced line 130 further includes two connection lines 142 and 144. The connection line 142 (referred to as the first connection line) couples the conductor 122 of the double-y transition slotline 120 to the coplanar conductors 133 and 134 and the center conductor 132 of the balanced line 130. The connection line 144 (referred to as the second connection line) couples the conductor 124 of the double-y transition slotline 120 to the coplanar conductors 135 and 136 and to the center conductor 131 of the balanced line.
In some examples, the un-balanced line 110 includes an un-balanced coplanar waveguide (CPW) line and/or any other type of dielectric waveguide (e.g., microstrip, stripline, etc.).
In other examples, the double-y transition slotline 120 includes a coupled slotline and/or any other type of dielectric waveguide.
In some examples, the balanced line 130 includes a balanced coplanar waveguide (CPW) line and/or any other type of dielectric waveguide.
In other examples, the first connection line 142 includes a first metal interconnection and the second connection line 144 includes a second metal interconnection. In some examples, the first connection line 142 includes a first microstrip and the second connection line 144 includes a second microstrip.
In some examples, the power input into the un-balanced line 110 and power output from the balanced line 130 is substantially the same (e.g., exactly, within +5%, within −10%, etc.).
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The double-y transition section 220 can, for example, convert the un-balanced line 210 (e.g., 50 ohm CPW line, 100 ohm CPW line, etc.) to a slotline. The slotline of the double-y transition section 220 can, for example, feed a CPW-T structure (e.g., two CPW lines branching from the slotline of the double-y transition section 220 in the shape of a “T”, two 95 ohm CPW lines, two 125 ohm CPW lines, T junction, etc.) of the balanced line 230. In this example, each set of the center conductors and the opposing coplanar conductors, respectively, of the CPW-T structure are connected to a side of the slotline of the double-y transition section 220 via an interconnect (e.g., a metal interconnect, a microstrip interconnect, etc.).
The balun 200 can be, for example, utilized to connect lines with the same or different impedances (e.g., the un-balanced line 210 and the balanced line 230 have the same impedance, the un-balanced line 210 and the balanced line 230 have different impedances, etc.). For example, the impedance of the un-balanced line 210 is 50 ohms and the impedance of the balanced line 230 is 95 ohms. As another example, the impedance of the un-balanced line 210 is 115 ohms and the impedance of the balanced line 230 is 45 ohms. The balun 200 can advantageously provide a high frequency and low loss conversion between un-balanced and balanced lines, thereby increasing the efficient transfer of signals between different types of lines.
The un-balanced line 210 can, for example, include a ground trace and a signal trace. The balanced line 230 can, for example, include a first and second signal trace. The first signal trace can, for example, be a center conductor of the balanced line 210.
The double-y transition section 220 can, for example, include a first slot trace and a second slot trace. The first slot trace can couple the ground trace of the un-balanced line 210 to the first signal trace of the balanced line 230. The second slot trace can couple the signal trace of the un-balanced line 210 to the second signal trace of the balanced line 230.
In some examples, the balun 200 includes a first connection section and a second connection section. The first connection section can couple (e.g., direct connection, electromagnetic coupling, etc.) the first slot trace of the double-y transition section 220 to the first signal trace of the balanced line 210. The second connection section can couple the second slot trace of the double-y transition section 220 to the second signal trace of the balanced line 230.
In other examples, the first connection section includes a first metal interconnection and/or the second connection section includes a second metal interconnection.
In some examples, the first connection section includes a first microstrip and/or the second connection section includes a second microstrip.
In some examples, the un-balanced line 210 includes an un-balanced coplanar waveguide (CPW) line and/or any other type of dielectric waveguide.
In other examples, the double-y transition section 220 includes a coupled slotline and/or any other type of dielectric waveguide. The coupled slotline can, for example, include first and second conductors mounted on a substrate.
In some examples, the balanced line 230 includes a balanced coplanar waveguide (CPW) line and/or any other type of dielectric waveguide.
In some examples, the power input into the un-balanced line 210 and power output from the balanced line 230 is substantially the same (e.g., exactly the same, within ±10%, within ±100 watts, etc.), thereby enabling the balun 200 to be low loss and highly efficient.
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The coupling of lines and/or conductors can include, for example, a direct physical connection, an indirect physical connection, an electromagnetic connection, and/or any other type of direct or indirect coupling.
Comprise, include, and/or plural forms of each are open ended and include the listed parts and can include additional parts that are not listed. And/or is open ended and includes one or more of the listed parts and combinations of the listed parts.
One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
The U.S. Government may have certain rights in this invention as provided for by the terms of Contract No. (classified) awarded by (classified).