transformer

Abstract

A transformer includes a primary winding and a secondary winding. The primary winding has N2 turns and has a first terminal and a second terminal. A secondary winding having N1 fractional sections (the N1 fractional sections together forming a complete turn) is adjacent to the primary winding to establish coupling between the primary winding and the N1 fractional coil sections, and the transformer turns ratio from the primary winding to the secondary winding is N2:(N3 / N1), where N2 is an integer equal to or greater than 1, N1 is an integer greater than or equal to 2, and N3 is an integer greater than or equal to 1. Also disclosed is a stacked integrated transformer having a primary winding and a secondary winding, wherein one or both of the primary winding and the secondary winding have a waterfall structure, and portions of the secondary winding and the primary winding serve as a ground shield between the secondary winding and the primary winding.

Description

Technical Field

[0001] The present invention relates to transformers and isolation devices, and in particular to radio frequency (RF) transformers and isolation devices. Background Art

[0002] The miniaturization of radio communication equipment has made significant leaps in the past decade with the development of new integrated circuits (ICs). These developments have facilitated the miniaturization of many components.

[0003] Transformers are commonly used in communications equipment to provide various functions, such as impedance transformation and isolation, such as between an output amplifier and an antenna. High-frequency RF transformers are also widely used as impedance matching circuits in RF integrated circuits. Examples include boost output transformers used in Wi-Fi and LTE RF power amplifiers. RF transformers are also used to provide common-mode isolation or perform differential-to-single-ended signal conversion (or vice versa).

[0004] However, the physical size of transformers is inherently large compared to the size of transistors in modern silicon technology. Unlike silicon transistors, the physical size of transformers is not scalable, resulting in higher chip costs when using more advanced silicon process technologies. Therefore, it would be very interesting if these transformers could offer improved performance over existing designs while still being integrated.

[0005] Furthermore, challenges exist when attempting to make integrated transformers capable of operating at high frequencies, such as RF and above. Surface-mounted transformers are one proposed solution, but such designs are large and consume valuable board space, limiting circuit size reductions. This design has performance and cost limitations.

[0006] Integrated transformers are another proposed solution, however integrated circuits also present challenges as circuits and systems operate at higher frequencies. For example, prior art circuit designs suffer from unwanted reflections from the secondary winding to the primary winding, high capacitance, and poor Q or K factors when presented with high-frequency signals.

[0007] The transformer can be a step-up transformer with a transformation ratio of N1:N2, a step-down transformer with N2:N1, or a simple unity transformer with a transformation ratio of just 1:1; where N1 and N2 are integers equal to or greater than 1. At higher GHz operating frequencies (above about 5 GHz), N2 is typically set to the lowest possible integer equal to "1" to achieve the highest possible quality factor, Q.

[0008] For step-down transformers operating at higher GHz frequencies, the transformer is often referred to as an N1:1 transformer. Conversely, for step-up transformers, it's often referred to as a 1:N1 transformer. Even at lower operating frequencies, where the transformer windings require higher inductance, we rarely see N2 > 2. Therefore, even in the lower GHz frequency range, transformer designs typically don't use, for example, an 8:4 transformer. Instead, the transformer is more likely to be a 4:2 transformer to achieve the equivalent 2:1 ratio.

[0009] Therefore, there is a need in the art for a transformer design that optimizes space consumption while maintaining performance parameters that do not degrade system performance. Furthermore, the transformer is required to have a high coupling coefficient, low resistance, and minimize reflections from the high-voltage winding to the low-voltage winding. Summary of the Invention

[0010] When designing and constructing RF transformers, there are several factors to consider and several challenges to overcome. As used herein, the term RF is defined to refer to, but not limited to, cellular bands, WIFI bands, and millimeter wave bands (such as, but not limited to, 1 / 2 GHz to 100 GHz). The design disclosed herein can also be used in integrated circuits or non-integrated applications, or as part of a printed circuit board, or as a discrete, independent component to obtain the following benefits. Any embodiment disclosed herein can be specifically implemented as an integrated transformer, part of a printed circuit board, or as an independent discrete component or stand-alone component such as mounted on a circuit board. For example, the TV band is in a frequency range that may not be suitable for integration, but it will still benefit from the transformer design disclosed herein. One aspect to consider is the K factor, which is defined as the coupling coefficient and must be optimized or balanced together with other performance parameters. The K factor refers to the fraction or amount of magnetic flux generated by a winding coupled to the secondary winding. A higher K factor (up to 1) is ideal.

[0011] The Q factor is also an important design consideration. The Q factor is commonly used with respect to inductors and sometimes for transformers. For transformers, the Q factor can be considered an indicator of the losses within the transformer due to resistance / impedance. The higher the Q factor, the lower the losses within the transformer due to lower resistance. Therefore, a higher Q factor is preferred to reduce signal loss and attenuation. Typically, for integrated inductors, the Q factor is no greater than 10, while discrete coil wire inductors can have a Q factor as high as 60.

[0012] While a high Q factor is desirable, achieving it at the expense of other transformer operating parameters is undesirable. For example, increasing the Q factor may come at the expense of a resonant frequency that is too low for the desired operating frequency. If the resonant frequency is too low, the transformer may be too large in capacitance to be useful for RF applications. For example, if the operating frequency is 5 GHz but the resonant frequency is 4 GHz, the transformer is not suitable for this application. It is preferable for the transformer to have a resonant frequency higher than the operating frequency.

[0013] Another factor that must be considered when designing an RF transformer is capacitance. This presents a significant design challenge in prior art transformers. As is understood in the art, capacitance occurs when a conductive conductor is adjacent to another conductor. This is a common arrangement in transformers where flux coupling occurs. Capacitance is often balanced with the coupling coefficient, K, which is also important. A K factor of 1 is preferred and ideal. However, a K factor of 1 is nearly impossible in RF transformers because there must be a gap filled with insulating material between the primary and secondary windings, and therefore the winding spacing cannot be zero or very close to zero. The closer the spacing between the primary and secondary windings, the better the coupling coefficient, K, but reducing this spacing also increases capacitance.

[0014] In the prior art, this conflicting relationship limits RF transformer performance. For example, a high resonant frequency is preferred, but to achieve this, capacitance must be kept low. To maintain low capacitance, a greater distance between the primary and secondary windings is required. However, a high K factor is also preferred, and to achieve a high K factor, the spacing between the primary and secondary windings must be minimized. This, in turn, creates more capacitance. These competing performance factors make RF transformer design difficult.

[0015] Furthermore, the insulating material separating the primary and secondary windings in integrated transformers is typically plastic, glass, or silicon, which generally has magnetic properties equivalent to air. This material does not provide ideal coupling and therefore cannot optimize the K factor.

[0016] Another design issue arises because the K factor from the primary to the secondary depends on the voltage seen on the secondary. If you build a transformer that steps up a voltage (for example, from 1V to 10V), the capacitance from the primary to the secondary is not referenced to ground, but to 10V. Typically, capacitance is measured with respect to or referenced to ground, but in this case, the capacitance is compared to the 10 volts seen on the secondary. The secondary typically has a higher voltage than the primary. This has the effect of multiplying the capacitance by the voltage gain of the transformer. This situation is similar to the Miller effect involving capacitance and amplification.

[0017] Typically, the capacitance from the primary winding to the secondary winding is multiplied by the amount of voltage step-up. This presents a design challenge for step-up transformers because as capacitance increases, the frequency collapses and the circuit output becomes severely distorted. The primary-side circuit will see a signal being transmitted because the secondary-side signal will couple back to the primary. The reflected signal will appear as a source of interference to the primary-side circuit.

[0018] Furthermore, most circuits are differential, but antennas are single-ended, with opposite terminals grounded or referenced to ground. This results in unbalanced coupling from the single-ended side, generating undesirable harmonics (including a very high number of odd harmonics). Government regulations do not allow for high harmonic signals because transmission systems are not allowed to transmit outside their authorized frequency bands, and such harmonics degrade the transmitted signal quality. Higher harmonics intersect / intermodulate with each other, generating undesirable in-band interference signals that may appear in the baseband.

[0019] To overcome the shortcomings of the prior art and provide additional benefits, an integrated transformer is disclosed, comprising a planar substrate, a primary winding, and a secondary winding. The primary winding on the substrate comprises a conductor having a first primary terminal and a second primary terminal. The secondary winding on the substrate comprises two or more fractional sections connected in parallel, the fractional sections together forming a complete turn, such that each of the two or more fractional sections is adjacent to the primary winding to maximize coupling.

[0020] In one embodiment, the primary winding is one turn and the secondary winding is one turn, and the secondary winding is divided into three fractional sections connected in parallel. In one configuration, the primary winding and the secondary winding are in the same plane. Consider that each fractional section has a first terminal and a second terminal. In one embodiment, the first terminal of each fractional section is connected and the second terminal of each fractional section is connected. In one configuration, the primary winding, the secondary winding, or both include fractional sections connected in parallel. In this configuration, the parallel-connected first terminal and second terminal of each fractional section provide a differential output from the secondary winding. The transformer can be part of a printed circuit board, a ceramic substrate, a semiconductor package, or a semiconductor die containing an integrated circuit.

[0021] Also disclosed is an integrated transformer comprising a primary winding having N2 turns. The primary winding includes a conductive path having a first terminal and a second terminal, and the conductive path forms an inner region generally enclosed by the conductive path. Another portion of the transformer is a secondary winding having N1 fractional sections proximate to the primary winding to establish coupling between the primary winding and the N1 fractional sections. The transformer has a turns ratio from the primary winding to the secondary winding of N2:(1 / N1), where N2 is an integer equal to or greater than 1, and N1 is an integer equal to or greater than 2.

[0022] In one embodiment, the primary winding and the secondary winding are located on the same layer. The integrated transformer may further include a substrate, such that the primary winding and the secondary winding are located on the substrate. In one configuration, N2 is equal to two and N1 is equal to three. It is contemplated that the N1 fractional parts, when added together, equal one.

[0023] In one arrangement, two or more fractional sections are connected in parallel. Also disclosed is an embodiment in which the length of each of the two or more fractional sections is less than a full turn, which reduces impedance, and the parallel connection of the two or more fractional sections reduces impedance compared to the impedance of a full turn. The integrated transformer can be part of a circuit board or a semiconductor package or semiconductor die.

[0024] A transformer including a primary winding and a secondary winding is also disclosed. The primary winding has N2 turns and a conductive path having a first terminal and a second terminal. The secondary winding has a fractional portion of N1 turns proximate to the primary winding to establish coupling between the primary winding and the fractional portion of two or more turns.

[0025] In one embodiment, the secondary winding comprises two turns, each of which comprises at least one fractional portion of a turn. In one configuration, the primary and secondary windings are located on the same layer. In one arrangement, the transformer further comprises a substrate, such that the primary and secondary windings are located on the substrate. In one embodiment, N2 is equal to 1, and 1 / N1 is equal to 0.75. Two or more fractional portions of a turn may be connected in parallel.

[0026] It is also contemplated that the fractional portions of two or more turns are each less than a full turn in length, which reduces the impedance of the secondary winding, and that the parallel connection of the fractional portions of two or more turns reduces the impedance compared to the impedance of a full turn. The transformer is one of the following types of transformers: a stand-alone discrete component, in a printed circuit board, in a semiconductor package, or integrated as part of an integrated circuit.

[0027] This document also discloses a transformer comprising a primary winding and a secondary winding. The primary winding comprises a conductor having two terminals. The secondary winding is adjacent to the primary winding, and the secondary winding comprises two or more turns, such that each turn is divided into two or more quadrants including an outer segment closest to the primary winding and one or more inner segments. The outer segment is connected to ground at a first outer segment end and to one of the one or more inner segments at a second outer segment end. The one or more inner segments have a first inner segment end and a second inner segment end that are interconnected. The first inner segment end is connected to the second outer segment end or another first inner segment end. The second inner segment end is connected to another first inner segment end or an output node of the secondary winding. The one or more inner segments are further away from the primary winding than the outer segments. The grounded outer segment is configured to shield the primary winding, protecting the primary winding from voltage reflections on the secondary winding.

[0028] The transformer can be part of a printed circuit board, a semiconductor package, or a semiconductor die that also includes an integrated circuit. The scribe line-like structure can form part of the primary winding, the secondary winding, or both. In one embodiment, the output node of the secondary winding is connected to the antenna. In one configuration, the transformer has a 1:1 primary-to-secondary turns ratio and four quadrants, each with one outer shield segment and three inner segments. As described herein, the connections between the outer and inner segments, as well as the connections between the inner segments, occur with waterfall transitions.

[0029] For a 1:1 turns ratio, the total number of segments is equal to the number of quadrants. For turns ratios greater than 1:1, the number of segments in each quadrant is greater than the number of quadrants. For turns ratios less than 1:1, the number of segments in each quadrant is less than the number of quadrants.

[0030] In another embodiment, a transformer is disclosed that includes a substrate and a primary winding positioned above the substrate. Insulation separates the primary winding from the substrate. The primary winding is formed of a conductive material having a first terminal and a second terminal. Insulating material covers the primary winding, and two or more shielding portions are positioned on the insulating material covering the primary winding. The two or more shielding portions are aligned with the primary winding such that each of the two or more shielding portions has a ground connection and two or more secondary winding connection points. Insulating material covers the two or more shielding portions. A secondary winding is positioned on the insulating material covering the two or more shielding portions. The secondary winding is aligned with the primary winding and the two or more shielding portions. The secondary winding is formed of a conductive material having two or more secondary winding connection points and two or more output terminals.

[0031] In one configuration, the conductive material of the primary winding has a shape that forms an inner region, and the two or more shielding portions have a shape that does not extend into the inner region. In one embodiment, the antenna is connected to two or more output terminals. The secondary winding may include two or more fractional turns. In one embodiment, the transformer further includes a waterfall structure between each fractional turn.

[0032] It is contemplated that the two or more shield sections include a spacer between each shield section, and the spacer is aligned with the waterfall structure. In one embodiment, the two or more fractional turns are connected in parallel. The transformer is configured as one of the following: a discrete component, a portion of a printed circuit board, a portion of a semiconductor package, or a portion of a semiconductor die containing an integrated circuit.

[0033] This document also discloses an integrated transformer having stacked elements, one above the other, with insulating material between the conductive elements. In one embodiment, the configuration includes a primary winding formed of conductive material having a first terminal and a second terminal. The insulating material covers the primary winding. Two or more shielding sections are positioned above and aligned on the primary winding, such that each of the two or more shielding sections has at least one ground connection and at least one connection point. The insulating material covers the two or more shielding sections. A secondary winding is positioned above and aligned with the primary winding and the two or more shielding sections. The secondary winding is formed of conductive material and is configured with two or more output terminals and an electrical connection to at least one connection point.

[0034] In one embodiment, the conductive material of the primary winding has a shape that forms an interior region, and the two or more shielding portions have a shape that does not extend into the interior region. The transformer may also include or be connected to an antenna that is connected to two or more output terminals of the secondary winding. In one arrangement, the secondary winding is divided into N quadrants, each quadrant containing M segments, where N is an integer greater than 2 and M is an integer greater than 2. The transformer may have a waterfall structure between each quadrant. It is contemplated that the two or more shielding portions may include a spacer between each shielding portion, with the gap aligned with the waterfall structure.

[0035] In one embodiment, the secondary winding includes two or more segments in each quadrant, such that the two or more segments include at least an inner segment closest to the inner region and an outer segment farthest from the inner region, and the two or more segments are connected in parallel. It is also contemplated that the transformer may be configured as one of the following: a discrete component, a portion of a printed circuit board, a portion of a semiconductor package, or a portion of a semiconductor die containing an integrated circuit. The two or more shielding portions block electrical interference from the secondary winding to the primary winding.

[0036] Other systems, methods, features and advantages of the present invention will be or will become apparent to those skilled in the art by studying the following drawings and detailed description. All such additional systems, methods, features and advantages should be included within this description, be within the scope of the present invention, and be protected by the following claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The components in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the different views.

[0038] Figure 1A An example environment using an RF transformer is shown.

[0039] 1B , 1C and 1D illustrate prior art RF transformer configurations.

[0040] FIG. 1E shows a prior art RF transformer configuration for a distributed amplifier transformer.

[0041] Figure 2A The proposed design of parallel fractional-winding transformer is shown.

[0042] Figure 2B Provides a center connection between the parallel connected inner windings (at Figure 2A An enlarged view of the center of the inner winding is shown).

[0043] Figure 2C yes Figure 2A A circuit diagram of the RF transformer is provided to aid understanding.

[0044] Figure 2D It shows that by Figure 2B An example embodiment of a very large turns ratio obtained by doubling the number of primary turns of a 1:(1 / 3) transformer is shown.

[0045] Figure 2E Shows that it can be used for Figure 2A 、 Figure 3A An example configuration of a primary winding with 3 turns in the embodiment of or any other embodiment disclosed herein.

[0046] Figure 2F An exemplary fractional primary winding is shown.

[0047] Figure 3A An example embodiment of a 1:(1 / 2) step-down transformer is shown.

[0048] Figure 3B is included Figure 3A A magnified view of the terminals of the secondary winding.

[0049] Figure 3C yes Figure 3B A circuit representation of the RF transformer is provided to aid understanding.

[0050] Figure 4 A transformer fraction ratio of 1:(2 / 3) is shown.

[0051] Figure 5A An example configuration of a transformer with multiple sections in a waterfall structure is shown.

[0052] Figure 5B yes Figure 5A The enlarged part.

[0053] Figure 6 Shown Figure 5A An alternative embodiment of a segmented partial waterfall structure is shown.

[0054] Figure 7 One example embodiment of an exemplary non-integer transformer ratio is shown.

[0055] Figure 8A An alternative embodiment of a differential to single-ended transformer is shown having a 1:2 turns ratio and 1 / 2 turn segment length.

[0056] Figure 8B A differential input and differential output transformer with waterfall transition is shown.

[0057] Figure 8C yes Figure 8B Circuit representation of the transformer.

[0058] Figure 9A A side view of the stacked layers of an exemplary stacked transformer configuration is shown.

[0059] Figure 9B 、 Figure 9C and Figure 9D A top view of separated stacked layers of an exemplary stacked transformer embodiment is shown.

[0060] Figure 9E Shown is a side perspective view of stacked layers of an exemplary stacked transformer configuration.

[0061] FIG. 10A shows a perspective view of a prior art conductive trace (wire) illustrating the aspect ratio of an integrated circuit.

[0062] Figure 10B Shown is a perspective view of a conductive line illustrating an improved aspect ratio on an integrated circuit.

[0063] Figure 11A A top view of an exemplary transformer winding with crossover features is shown.

[0064] Figure 11B Shown Figure 11A A side view of a portion of an exemplary transformer winding is shown.

[0065] Figure 12 Alternative embodiments of primary and secondary winding structures are shown.

[0066] Figure 13 A waterfall winding structure is shown in a square or diamond configuration.

[0067] Figure 14 A top view of the elements of a stacked transformer with waterfall transition is shown. DETAILED DESCRIPTION

[0068] Figure 1A An example environment for using an RF transformer is shown. This is just one possible use case, and other use cases are contemplated. As shown, differential input 160 provides a signal to amplifier 164. Amplifier 160 can be any type of amplifier. The amplifier output is an amplified differential signal that is connected to RF transformer 168. RF transformer 168 provides isolation and can step up or down voltage. The output of the RF transformer is a single-ended signal that is connected to antenna 172.

[0069] FIG1B and FIG1C illustrate example configurations of prior art radio frequency (RF) transformers. Both configurations have primary and secondary windings with generally symmetrical paths. As shown in FIG1B , inner winding 108 is a single turn, and outer winding 120 is also a single turn, resulting in a 1:1 transformer ratio. The inner and outer turns are generally symmetrical. Outer turn 120 has terminals 124A, 124B, while inner turn 108 has terminals 112A, 112B.

[0070] FIG1C is another example embodiment of an RF transformer in which the windings are configured in a generally square shape. In this embodiment, the inner winding 138 is a single turn, and the outer winding 150 is also a single turn, resulting in a 1:1 transformer ratio. The inner and outer turns are generally symmetrical. The outer turn 150 has terminals 154A, 154B, while the inner turn 138 has terminals 132A, 132B.

[0071] FIG1D illustrates a prior art RF transformer configuration. In this embodiment, in a prior art arrangement, inner winding 160 has two turns, while outer winding 164 has one turn, creating a 1:2 turns ratio. Inner (secondary) winding 160 is a concentric winding. Also shown are the input terminals, antenna connection, and ground connection. Axiom Micro devices can provide a distributed active transformer of this nature. This configuration suffers from the shortcomings of the prior art.

[0072] FIG1E shows a prior art RF transformer configuration for a distributed amplifier transformer. In this prior art configuration, secondary winding 170 has output terminals connected to antenna 174 and ground node 178. As shown, four amplifiers 182 are connected to primary winding 184. An input signal is provided to each amplifier 182 via amplifier input 186. An example of this embodiment is disclosed in U.S. Patent 7,471,153, issued on December 20, 2008. Although this prior art configuration divides primary winding 184 into separate, independent sections connected in series by amplifiers 182, it suffers from the possibility of large antenna-side signals being injected into the primary winding. This design also suffers from the shortcomings of the prior art and requires the four-amplifier connection shown, which requires four amplifiers instead of one (limiting its use) and increases power consumption compared to the design disclosed herein. This design lacks shielding segments, waterfall transition structures, and any parallel-connected windings.

[0073] This document discloses that, in some embodiments, as few turns as possible are used for transformers operating at higher GHz frequencies. One challenge to overcome is to construct a high-frequency transformer that mathematically has an N1:1 transformation ratio while using a maximum number of turns of only 1, even on the primary side, when N1 is an integer equal to or greater than 2. Another way to state this relationship is: when N1 is an integer equal to or greater than 2, the goal is to construct a 1:(1 / N1) step-down transformer using no more than one turn on the primary side. As described below, other turns ratios and relationships are possible in other configurations. In addition, the aforementioned operating parameters, such as capacitance, K factor, Q factor, and resonant frequency, must be considered and maintained.

[0074] The following definitions help clarify the following discussion:

[0075] Inductor (L): Traditionally, inductors are made from a circular or square coil of a conductor, such as copper wire. Inductors of different sizes and shapes have different inductance values. The larger the coil, the greater the inductance. For the sake of completeness, even straight wire has parasitic inductance associated with it. In well-made inductors, the value of the parasitic inductance is typically much smaller than the main inductance.

[0076] Coil: Historically, a coil is a round wire with N turns. Coils can be formed in a variety of shapes, geometries, and sizes. Many commercial inductors are called coil inductors. This indicates that the inductor is made in the form of a coil of wire. Therefore, it is common to use the terms "coil" and "inductor" interchangeably. The terms "coil" and "winding" are used interchangeably in this article.

[0077] Winding: Traditionally, a winding or coil is made by wrapping a straight metal wire around a round bobbin. As used herein, the term "winding" refers to any conductor that forms the primary or secondary side of a transformer. The words "winding" and "coil" are used interchangeably, with "coil" being thought of as a wire wound into a coil. A winding consists of one or more turns of a conductor. A winding can be made of any conductive material and can be a conventional wire, a circuit board trace or conductor, or a conductor in an integrated circuit.

[0078] Turns: Traditionally, inductors are made from at least one turn of conductive material, such as wire. Inductors with higher inductance values ​​are made from multiple turns. A one-turn winding has wire formed into a 360-degree rotation (of any geometry), where the start and end points of the wire terminate in the same general location. As disclosed herein, fractional turns are possible so that the fractional turns do not extend for a full 360 degrees. Multiple fractional turns can be combined to create a full 360-degree rotation.

[0079] Transformer: Defined as two or more inductors placed adjacent to each other. These inductors are magnetically coupled to each other. The closer the spacing between these inductors, the higher the coupling coefficient factor.

[0080] Transformer Ratio: Defined as the ratio of the number of turns between the transformer's windings. For a simple transformer with a primary and a secondary, this is essentially the ratio of the number of turns in the primary to the number of turns in the secondary. The transformer ratio is a ratio of two integers because transformers must have windings that are a full multiple of 360 degrees to prevent magnetic leakage.

[0081] Coupling coefficient (K): This defines the degree of coupling between multiple inductors in a transformer. In an ideal transformer, where the spacing between inductors and the size of the inductors are essentially zero, K is essentially close to 1. By definition, the leakage inductance of an ideal transformer is zero.

[0082] Fractional Ratio Transformer: A fractional ratio transformer is defined herein as a transformer in which at least one winding has a non-integer (less than 1) number of turns. To prevent magnetic leakage, a fractional ratio transformer has a winding with multiple sections of 1 / N turns, with N of these sections positioned relative to each other so that they form a full 360-degree turn and are equally loaded (such as by connecting them in parallel with each other), or so that one or more sections are equally loaded. In a fractional ratio transformer, the fractional turns add up to an integer value.

[0083] Waterfall structure transformer: a transformer with waterfall transformation structure and shielding structure.

[0084] Transformer Input / Output Arrangements: Any transformer configuration or embodiment disclosed herein or derived from any disclosure herein may be configured with any combination of primary windings having differential or single-ended inputs and secondary windings having differential or single-ended outputs.

[0085] Wire: As used herein, the term "wire" is defined to mean any type of conductor used in a transformer. Wire can include conventional wire of any geometry, such as wound into a coil, or conductive traces on a circuit board, semiconductor package, or integrated circuit die. Wire can have or not have surrounding insulation associated with it.

[0086] Segment: A segment is defined in this document as the conductors in a transformer winding that, when combined, form a complete turn and are separated by waterfall transitions. One of the segments can act as a shield segment while the other segments are waterfall segments.

[0087] Quadrant: A quadrant is a designation for a division or portion of a transformer winding having a waterfall transition configuration. If a winding of a transformer winding having a waterfall transition has two waterfall transitions, then the winding has two quadrants, such that the waterfall transitions divide the winding into quadrants.

[0088] Fractional Ratio Transformer

[0089] To overcome the shortcomings of the prior art, a transformer design is proposed having a (1 / N1) turn secondary winding suitable for integration into a printed circuit board, silicon chip, or for package integration. First, it is important to note that the use of fractional 1 / N1 windings ostensibly violates the coupling constraint requirements for building a well-designed transformer. To address this coupling issue, the first step is to create N1 1 / N1 turn windings so that all of the 1 / N1 turn windings together will have complete and equal coupling with the primary winding (a single-turn primary winding in this example). The concept of parallelizing these N1 1 / N1 turn windings into a single equivalent 1 / N1 winding is then used to effectively reduce resistance compared to separate fractional windings.

[0090] To illustrate this concept, an example is provided where N1 is equal to 3. In other embodiments, a different number of turns can be established such that N can be equal to any positive integer. Figure 2A The proposed design of the parallel fractional winding transformer is shown. An example embodiment of the step-down transformer 248 with a turns ratio of 1:(1 / N1) or 1:(1 / 3) is shown. Figure 2AIn the proposed design shown, all three of the 1 / 3 turns are connected in parallel. The outer winding 250 is the primary winding and is a single-turn winding, while the inner windings are three windings 254A, 254B, and 254C connected in parallel. The outer primary winding 250 has terminals 252A and 252B. The inner secondary windings 254A, 254B, and 254C, connected in parallel, have terminals 260A and 260B.

[0091] Each of the fractional windings is referred to as a winding, and each of the fractional windings has a first terminal and a second terminal, i.e., two terminals. Three of the six terminals (not shown with dotted lines) of the 1 / 3-turn (fractional) windings 254A, 254B, and 254C are interconnected. The other three of the six terminals (shown with dotted lines) are connected together using a second layer of metal connection (shown in the center of the inner winding). The windings are effectively connected in parallel.

[0092] Figure 2B Provides a center connection between the parallel connected inner windings (at Figure 2A The center of the inner winding is shown in an enlarged view. Terminals 3 and 4 are both Figure 2A and Figure 2B Similarly, Figure 2A and Figure 2B Both show a large dot designating the winding polarity. Maintaining consistent direction is important when establishing polarity and dot notation. This can be achieved by maintaining a consistent (clockwise or counterclockwise) path from the input terminal to the output terminal / ground. Dashed lines show connections between endpoints (shown as small dots) but do not connect to any lines intersected by the dashed lines. Small circles are shown at the connection points. Therefore, dashed lines that cross solid lines are not connected to the solid lines. The dashed lines are on another layer of the RF transformer in a multilayer semiconductor implementation.

[0093] Each of the three 1 / 3 turns of the secondary side 254A, 254B, 254C is magnetically "equally coupled" to the primary side 250 due to the generally equal length and symmetrical configuration of each fractional portion. Equally importantly, all of the flux from the primary side 250 is fully coupled to the secondary side 254A, 254B, 254C, with virtually no leakage other than minimal, unavoidable leakage due to the non-zero spacer gap and other external connections required to connect to actual active circuitry. Consequently, the transformer coupling coefficient between the primary turns 250 and the secondary turns (fractional portions 254A, 254B, 254C) is generally the same as that of a conventional 1:1 ratio transformer of the same equivalent construction size.

[0094] The designs disclosed in the variations of Figures 2 and 3 offer numerous advantages over the prior art. For the transformer's overall maximum diameter or width, the smaller number of turns keeps each turn larger, compared to windings with multiple turns (which must have smaller turns to accommodate a fixed size). As turns become smaller, the Q factor decreases. Thus, the disclosed design maintains a lower number of turns while also maintaining a larger size, which in turn improves the Q factor and maintains low inductance. Furthermore, the number of parallel paths reduces resistance as the distance of each parallel path is shortened.

[0095] Figure 2C yes Figure 2A A circuit diagram of the RF transformer is provided to aid understanding. Identical elements are labeled with the same reference numerals, and the discussion of these elements and connections will not be repeated. It can be seen that the three fractional windings 245A, 254B, and 254C are connected in parallel, and the terminals 3 and 4 of the secondary winding correspond to Figure 2B The small leads 3 and 4 are shown. The primary winding is 1 turn, and the three parts of the 1 / 3 length winding each constitute a complete turn of the secondary winding. After the discussion of Figure 3, the following discussion Figure 2D 、 Figure 2E and Figure 2F .

[0096] To further illustrate this concept, another example embodiment is shown with N1 equal to 2 for a 1:(1 / 2) step-down transformer. Figure 3A As shown. The outer winding (primary winding) 350 has terminals 352A, 352B. As shown, the inner winding (secondary winding) 354A, 354B has terminals 360A, 360B. The sum of the two fractional 1 / 2 turn windings 354A, 354B on the secondary side also equals 1 full turn, and all of the fractional turns 354A, 354B are equally magnetically coupled to the primary side winding 350, creating two parallel-connected 1 / 2 turns to produce a transformer with a much higher Q factor compared to traditional 2:1 transformers at higher GHz operating frequencies. This is one of the significant benefits of the design of the present disclosure.

[0097] Figure 3B Yes Figure 3A An enlarged view of the secondary winding including terminals 360A, 360B is shown. Dashed lines that intersect the solid lines are not connected to the solid lines. The dashed lines are on another layer of the RF transformer implemented in a multilayer semiconductor.

[0098] Figure 3C yes Figure 3B The circuit diagram of the RF transformer is shown in FIG. 1 to aid understanding. Like elements are labeled with like reference numerals, and discussion of these elements and connections will not be repeated. Figure 3CThe arrangement of the components, the electrical connections and the parallel arrangement of the fractional turns of the secondary winding are clearly shown.

[0099] Another benefit of the design disclosed herein is that the series resistance of the windings of a 1:(1 / N1) transformer is much smaller than that of their conventional N1:1 counterparts. For example, for a 1:(1 / 3) step-down transformer, the series resistance of the secondary turns is theoretically 9 times smaller than that of a conventional 3:1 transformer. To achieve this resistance reduction in prior art transformers, a 3:1 transformer with a secondary winding with 1 / 9 the resistance would require the secondary winding to be very small, such as 1 / 9 the area of ​​the primary winding. In this embodiment, the inductance is based on the length of the wire forming the winding, but as the winding size decreases, performance also decreases.

[0100] The disclosed design has such low resistance because each 1 / 3 fractional winding is 1 / 3 of a full turn in length and therefore has a resistance of 1 / 3 a full turn, resulting in a 1 / 3 reduction in resistance, plus the parallel arrangement of three 1 / 3 turn windings results in a total resistance of 1 / 9 compared to a prior art transformer using a single turn without a 3:1 ratio of fractional windings.

[0101] As the winding size decreases, the inductance also decreases, but the Q factor deteriorates. A low Q factor is undesirable, while a high Q factor is preferred. With the disclosed design, for very high frequency applications, the winding size does not need to be too small, while achieving low inductance and high Q factor due to the fractional nature of the winding configuration. This is ideal when ultra-low inductance is required on one or more sides of the transformer. This is a significant improvement over the prior art. Even including the additional parasitic resistance for connecting three separate 1 / 3 turns of wire in parallel, the overall series resistance is still many times lower.

[0102] This principle can be further extended to create a fractional transformer with a higher transformer turns ratio by making the number of turns of the primary winding greater than 1. Typically, this is expressed as an N2:(1 / N1) step-down transformer, where N2 is equal to or greater than 1 and N1 is equal to or greater than 2.

[0103] For example, if N2 equals 2 and N1 equals 3, the resulting ratio is a 2:(1 / 3) transformer, which has an incredible equivalent mathematical ratio of 6:1, and a footprint generally similar to a traditional 2:1 transformer. For the reasons mentioned above, this design also has very low resistance, which is not possible with prior art designs. This extremely large transformer turns ratio is achieved by Figure 2B The 1:(1 / 3) transformer shown in the figure is realized by doubling the number of turns on the primary side. Figure 2D As shown. Figure 2DIn FIG. 1 , like reference numerals refer to like elements, except for the primary winding 250 , which now has two turns instead of one.

[0104] Figure 2E Shows that it can be used for Figure 2A 、 Figure 3A Example configuration of a primary winding with 3 turns in the embodiment of or any other embodiment disclosed herein. Only one winding ( Figure 2E 270B). It will be appreciated that the winding 250 will be located adjacent to the other winding to allow for coupling of magnetic flux. As shown, winding 250 has two terminals 252A, 252B and can therefore be configured for differential or single-ended operation. Winding 250 has two crossovers 270A, 270B. These crossovers 270A, 270B achieve uniform coupling within winding 250.

[0105] Figure 2F An exemplary fractional primary winding is shown. This is only one possible fractional winding configuration, and one of ordinary skill in the art will appreciate that other fractional numbers can be used, various shapes can be employed for the windings, and the fractional windings can be positioned as inner or outer windings. Furthermore, this fractional winding configuration can be combined with any of the configurations or embodiments shown herein. One or both of the primary or secondary (first and second) windings can be fractional windings.

[0106] In this example embodiment, the primary winding includes three fractional turns 274A, 274B, 274C. Terminals 3 and 4 are connected to an amplifier 290 so that the amplifier provides an amplified input signal to the primary windings 274A, 274B, 274C. A secondary winding 286 is adjacent to each fractional turn 274A, 274B, 274C to achieve magnetic flux coupling. The secondary winding 286 includes two terminals connected to the amplifier 278 and the ground node 282, as shown. As shown, Figure 2F The transformer has a differential pair input and differential pair output configuration and in this embodiment is a 1 / 3:1 turns ratio, which is magnetically equivalent to a 1:3 turns ratio.

[0107] In addition to the combinations shown, other combinations are possible, such as a 1 / 2:1 ratio transformer, a 1 / 2:2 ratio transformer, or a 1 / 2:1 / 2 ratio transformer. The fractional value can vary, such as, but not limited to, 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 6, or any 1 / N, where N is any positive integer. Any winding can have a fractional turn structure. Furthermore, it is disclosed herein that the amplifier 290 can be replaced by a receiver.

[0108] The low series resistance property of fractional 1 / N1 turns is very useful for high current (or power) applications because it greatly reduces I 2R losses. At operating frequencies exceeding 5 GHz, this allows for a high-ratio N2:(1 / N1) step-down transformer with a very compact form factor. Conversely, this also allows for the opposite (1 / N1):N2 step-up transformer. Such a high-ratio step-up transformer can be used in the final stage of a high-power CMOS power amplifier, for example using low-voltage MOS transistors, and can be used in many other applications.

[0109] The transformer structure can be configured to have a generalized ratio of (1 / N2):(1 / N1). For example, in such an embodiment, the primary winding N2 can be 2 and the secondary winding N1 can be 3. Thus, the resulting ratio is 1 / 2:1 / 3. This is mathematically equivalent to a 3:2 ratio, but only 1 turn is used for each of the primary and secondary turns. Using fewer turns, such as only one turn each in the primary and secondary, rather than the 3:2 turns ratio configuration of 3 turns and 2 turns of the prior art, reduces inductance and resistance, thereby improving operation at high frequencies (such as RF as defined herein). In addition, the 3-turn winding must be made very small for operation at 6 GHz, while the 1-turn winding composed of three 1 / 3 turn fractional parts does not have to be made as small because it only has one turn (albeit a fractional one).

[0110] For example, a three-turn winding might be only 50 microns in size, while a one-turn winding might be 200 microns in size. For better performance, the ratio of the winding bundle size to the overall transformer diameter is preferably small. A very special case is when N2 and N3 are the same (N2=N3), which results in an effective ratio of 1:1. This can be expressed as a 1 / 3:1 / 3 ratio. The benefit of having fractional windings on both the primary and secondary sides is a significant reduction in resistance and a higher Q factor, suitable for very high frequency (over 10 GHz) operation.

[0111] An example where N2 is preferably greater than 1 is for cellular radio applications (low 1-2 GHz operating frequencies). In such a system, it may be desirable to have the equivalent of a 4:1 transformer, but with the equivalent dimensions of a 2:(1 / 2) transformer, while the transformer will have a higher quality Q factor than prior art designs. In such a design, the primary winding will have two turns, and the secondary winding will have two 1 / 2 fractional windings. This will be Figure 2D The primary winding 250 and Figure 3A The fractional-turn transformer will allow a variety of new integrated circuit products to be manufactured with integrated transformers because the cost will be more attractive with smaller transformer components.

[0112] Another benefit of the compact size of these high-ratio N2:(1 / N1) transformers is that the transformers (which are often smaller in size than traditional transformers) can now be placed directly on top of the active transistors. This allows integrated circuit designers and manufacturers to save more of the precious silicon area of ​​the RF chip. Many of the existing RF circuit topologies that rely on the use of multiple discrete RF transformers can now be integrated into the silicon chip with minimal or no additional cost. Without this new fractional transformer topology, many transformer-intensive RF circuits would be unusable in commercial applications or impossible to build at all, especially when the transformer quality Q factor is very high.

[0113] Although the above disclosure shows a single turn that can be divided by N1, where N1 is an integer equal to or greater than 2, there is no restriction that the configuration must only start with a single turn. Therefore, it is contemplated and disclosed that, for example, there can be 2 turns (or any integer) of winding on the primary or secondary side of the transformer. These turns can be divided into N1 segments. Thus, in this example embodiment, the length of each wire segment has an equal length of 2 / N1. The simplest example is when N1 is equal to 3, using a total of 2 turns of wire. Therefore, the length of each divided wire is 2 / 3, and there are 3 such wires. When these three 2 / 3 wire segments are connected in parallel, a transformer ratio of N2:(2 / 3) is generated. When N2 is equal to 1, a transformer ratio of 1:(2 / 3) is generated. Using this design arrangement, other integer-to-integer ratios (such as 2:(2 / 3) and (1 / 3):(2 / 3)) are also possible. This arrangement can be further generalized to N2:(M1 / N1), where M1, N1, and N2 are the same or different values, and include numbers equal to or greater than 1. It is also contemplated that N2 may be 1 / N2 or even M2 / N2.

[0114] Figure 4 An example embodiment of a transformer having a fractional ratio of 1:(2 / 3) is shown. This is just one example embodiment. As shown, the 1:2 / 3 transformer 404 includes a primary winding 408 having input terminals 412A, 412B. The primary winding 408 is a single turn winding, but in other embodiments, it can have more than one turn (see Figure 2D and Figure 2E) or a fractional turn winding. The secondary winding 416 includes three sections, each of which is 2 / 3 of a turn in length. As shown, the secondary winding 416 includes three fractional winding sections 420A, 420B, and 420C. These three windings are electrically connected in parallel. When combined, the segment length is equal to 2 / 3+2 / 3+2 / 3=6 / 3, or 2. In other words, the three segments are defined as segment A1+A2, segment B, and segment C, where the segment lengths A1+A2=B=C. As understood in the art, slight variations from "exactly equal" occur during the manufacturing process and may even be intentional without departing from the concept of the invention and the subsequent claims. As shown, the secondary winding 416 has a common antenna connection and a ground connection.

[0115] Thus, unique transformer ratios can be constructed that are not possible in the prior art and that have low impedance and high Q. This concept can be extended to other fractional ratios, such as four segments, each ¾ the length of a full turn, such that 3 / 4 + 3 / 4 + 3 / 4 + 3 / 4 = 12 / 4 = 3 turns.

[0116] In summary, in one or more embodiments, various disclosed innovations implement and provide a compact high turns ratio transformer that includes the concept and configuration of dividing the conductor of a single turn winding into N1 approximately equal winding sections, where N1 is an integer equal to or greater than 2. The design connects N1 of these sections in parallel in such a way that all of the signals are in phase with each other and the sections are connected as shown by the dot symbols in the figure. Although 2 fractional turns or 3 fractional turns are shown, it is contemplated that any number of fractional turns can be used on the secondary winding or even the primary winding. It is also contemplated that the primary winding can have an integer number of turns or (multiple) fractional configurations of turns, or that the secondary winding or the primary winding can be a fractional winding, i.e., a single turn comprising multiple windings connected in parallel or multiple turns comprising multiple windings connected in parallel. Also disclosed herein are the following: Figure 2B and Figure 3B Different RF transformer shapes are shown in the circular form. Contemplated shapes include, but are not limited to, square, triangle, hexagon, octagon, pentagon, heptagon, enneagon, decagon, or any other shape. The transformer designs disclosed herein are contemplated to be integrated or formed on a semiconductor device, die, package, or any other arrangement. The primary winding, secondary winding, or both can be fractional-turn structures and have any number of turns or any number of fractional turns.

[0117] Transformer with waterfall transition and shielding section

[0118] With very few exceptions, almost all modern integrated circuit designs utilize differential circuit topologies. This is preferred because differential circuits are inherently more immune to common-mode interference from the power supplies than their single-ended counterparts. This is the primary reason why nearly every CMOS RF integrated circuit built today is built using differential implementations, even though historically, discrete RF circuits were built exclusively using single-ended topologies.

[0119] However, when implemented, any RF integrated circuit must ultimately still interface with single-ended devices, such as the single-ended antenna found in all cell phones and radios. The job of performing the differential-to-single-ended signal conversion is dedicated to RF transformers.

[0120] However, differential-to-single-ended transformers are inherently unbalanced. They are unbalanced because on one side of the transformer (e.g., the primary side of an RF power amplifier circuit), the signal pins are connected differentially, meaning the AC signals move in equal but opposite directions. However, on the other side of the transformer (e.g., the secondary antenna side), one of the signal pins is grounded (connected to GND). The remaining pin carries the output signal (now referenced to GND).

[0121] Unfortunately, when implemented, it is necessary to consider that there is always parasitic coupling capacitance between the primary and secondary signal pins, as this parasitic coupling capacitance is undesirable. When one side of the signal pin is grounded, the signal coupling from the secondary pin to the primary pin is not balanced, as only the parasitic coupling capacitance from the signal pin will inject the signal into one of the differential pins.

[0122] Further challenges arise because CMOS RF integrated circuits operate at low voltages, while the signal voltage swing at the antenna is many times higher than the typical CMOS transistor operating voltage. For example, when transmitting a typical 1-watt power level signal to a typical antenna with a 50-ohm matched impedance, the actual transmitted single-ended RF signal has a peak-to-peak voltage swing of + / -10 volts. However, the CMOS transistors used to construct integrated RF amplifiers typically operate at only about 3.3 volts.

[0123] It has been observed through testing that in the higher GHz operating frequency range, even a 1 pF coupling capacitance from the high voltage terminal of the secondary transformer terminal to one of the terminals on the primary side can seriously interfere with the operation of our low voltage CMOS RF amplifier.

[0124] This article provides a discussion that explains and illustrates how to design a transformer with reduced signal coupling from the single-ended side to the differential side of the transformer. RF transformer designs are disclosed that have shielding structures using (various) novel winding structures. An example of such a structure is Figure 5AAs shown. The unique feature of this new structure is the introduction of what is referred to herein as segmented multi-strand wires, so that the "outer" segments of the multi-strand wire bundle are the winding wires (conductors) connected to ground (plane, terminal, pin) and therefore have the lowest signal amplitude. The segments closest to the primary winding act as a shield to prevent or reduce electrical coupling. Moving from the outer segments of the multi-strand bundle toward the center bundle are winding segments that produce a variety of winding types. Each of these series-connected wire segments is generally identical to each other and are arranged in parallel with each other to produce an equivalent single-turn winding.

[0125] like Figure 1A As shown in FIG. 1B , the further disclosed design provides additional benefits over prior art designs. Figure 5A An example configuration of a segmented waterfall transformer is shown. This is only one possible arrangement of the elements, and it is contemplated that the disclosed waterfall structure may be applied to a variety of other designs, shapes, and transformer applications. This example embodiment is considered a planar arrangement because the various elements (primary winding, waterfall segments, shield segments, secondary windings) are all on the same general plane or level, except for interconnects (also known as jumpers) that may extend upward and downward (such as through vias) to connect different elements of the transformer. The terms "waterfall segment" and "segment" are used interchangeably and are defined to refer to a segment that is not a shield segment.

[0126] In this embodiment, waterfall transformer 504 includes a primary winding 508 having input terminals 512A, 512B. Primary winding 508 is an outer winding. As described below, the primary winding can also form an inner winding, or include two parallel-connected windings configured as an inner winding and an outer winding.

[0127] Located adjacent to the primary winding 508 is the secondary winding 520 (commonly), which comprises segments 520A, 520B, 520C, and 520D for one turn. Each quadrant has a similar configuration. In this exemplary embodiment, there are four quadrants 524A, 524B, 524C, and 524D. As shown, as each segment progresses around the turn in each quadrant, segments 520A, 520B, 520C, and 520D form a complete turn. Each segment constitutes a fraction of a turn, in this embodiment, ¼ of a turn. This configuration can be referred to as a quarter-wave waterfall structure. When transitioning to the next quadrant, the segments waterfall inward to a more inward position, i.e., away from the other windings. If the secondary coil were outside the primary coil, the waterfall would occur in the opposite direction, i.e., cascading outward. For quadrant 524A, shield segment 520A is the shield segment because it is directly adjacent to the primary winding 508. There are four copies of segments 520A, 520B, 520C, 520D forming the secondary winding, with four segments per quadrant, and each segment rotated 90 degrees (for the quarter-wave design shown) and extending to a complete turn when combined in series. For a fraction of a turn (1 / 2 or less) (for a quadrant), the shield segment is closest to the other turns and then falls away from the other turns where it becomes a waterfall segment to form a complete turn.

[0128] The segments adjacent to the primary winding 508 (such as segment 520A) serve as shields due to being connected to ground 528 at one end of these segments. The function and benefits of shielding will be described in detail below. As shown, the shield segments (one in each quadrant) are connected in parallel and in close proximity to the primary winding 508. As shown, all transformer turns are connected in parallel and are very close to other transformer components. The shield segments (the segments closest to the primary winding 508, such as shield segment 520A) allow magnetic field coupling from the primary winding to the secondary winding, but reduce the electrical coupling from the secondary winding to the primary winding (higher voltage winding to lower voltage winding). The magnetic field from the primary winding can pass through the metal shield segments into the secondary winding, but the electric field from the secondary winding cannot pass through the metal shield segments into the primary winding. In other embodiments, other shapes and configurations are possible.

[0129] Moving one level (segment) inward on secondary winding 520 is segment 520B in quadrant 524B. Because segment 520B is not the segment closest to primary winding 508, it is no longer a shield segment and is now referred to as a waterfall segment. Waterfall segment 520B captures magnetic flux from primary coil 508, which in turn generates voltage and current in secondary coil 520. Moving one more level (segment) inward on secondary winding 520 is waterfall segment 520C in quadrant 524C. This waterfall segment 520C captures magnetic flux from primary winding 508, which in turn generates voltage and current in secondary winding 520. Moving an additional level inward on secondary winding 520 is segment 520D in quadrant 524. This waterfall segment 520D captures magnetic flux from primary coil 508, which in turn generates voltage and current in secondary winding 520. In this embodiment, the end of the innermost (last) waterfall section 520D is connected to an antenna (not shown), or is an output (or input) terminal 530 of the secondary winding 520. In this example embodiment, the secondary winding is single-ended, such that one terminal of the winding is connected to ground 528, and the other terminal is the output (or input) terminal 530.

[0130] For the disclosed quarter-wave waterfall configuration, each shield segment extends 1 / 4 of the distance of a single winding turn. The secondary winding has four copies, each 90 degrees (rotated) from the next. For other wave values ​​(such as a 1 / 3 wave configuration), each shield segment extends 1 / 3 of the winding distance. Thus, the secondary winding will have three copies, each rotated 120 degrees from the next. Other configurations are contemplated.

[0131] The following operation and functionality of the shield are described in the example context of an RF transformer located between an amplifier and an antenna to provide isolation and optional step-up or step-down functionality. In operation, the input signal from the amplifier is provided to input terminals 512A and 512B of primary winding 508. The input to the primary winding is a differential signal. This establishes an AC current in primary winding 508. This current generates a magnetic field that couples to secondary winding 520. The magnetic field couples into secondary winding 520, generating a current and voltage in the secondary winding. The output terminal 530 of the secondary winding is connected to the antenna to enable transmission of the secondary winding signal from the antenna.

[0132] In prior art RF transformers, signals from the secondary winding are reflected back to the primary winding, thereby degrading system performance. In the embodiment shown herein, the embodiment includes shield segments (segments closest to the other windings, such as shield segment 520A) connected to and as part of the secondary winding 520. In addition, the shield segments are connected to ground 528 and are adjacent to the primary winding. The segments are shield segments for a fraction of a turn (for quadrant distance, not a full turn) and then transition to a position not adjacent to the primary winding for the remainder of the turn. This limits the accumulation of charge on the shield segment 520A to (at Figure 5A In the embodiment of FIG, 1 / 4 of the total voltage of the secondary winding 520. The shielding section length is less than one turn, such as generally the length within one quadrant.

[0133] like Figure 5A As shown, at node A, which is grounded, the voltage is 0 volts. Continuing clockwise along this segment to node B, the voltage rises to 2.5 volts. Continuing to node C, the voltage accumulates to 5 volts. At node D, magnetic coupling generates a voltage of 7.5 volts. Finally, at the end of this turn, the voltage at node E, which is the connection point for the antenna, is 10 volts. As a result, the primary winding 508 only sees or experiences a maximum reflection of 2.5 volts of electrical coupling, which is a 75% reduction compared to prior art designs. If an additional 1 / 4 turn were added to each turn, the transformer would have a 1:1.25 turns ratio, and the output voltage provided to the antenna would be 12.5 volts, while the reflection from the secondary winding to the primary winding would remain at a maximum of 2.5 volts.

[0134] In other designs, such as if there are three quadrants with three waterfall structures, the voltage reflections will be reduced by a factor of 3. The shield segment structure and ground connection limit the amount of charge accumulation from the secondary winding 520 to the primary winding 508, thereby limiting the reflections. The secondary conductor segment closest to the primary winding is voltage limited due to the repeated grounding, and due to the waterfall nature of the design, its distance directly adjacent to the primary winding is limited. Figure 5A As shown, the secondary winding is connected to ground 528 at four locations. This limits the amount of charge that accumulates on the outermost shield segment 520A, which in turn limits the amount of charge that can be reflected back to the primary winding. The greater the number of quadrants, the less charge accumulates.

[0135] Figure 5B An enlarged portion 536 of the transition (drop) between quadrants is shown. Figure 5B The waterfall transition is between quadrants 524A and 524D. Figure 5A and Figure 5BAs shown, enlarged portion 536 shows the primary winding 508 and the fractional portion of the secondary winding. In quadrant 524D, shield segment 540A is the outermost segment, but it falls inward, becoming a waterfall segment in quadrant 524A. Similarly, segment 540B in quadrant 524D falls inward, becoming a waterfall segment in quadrant 524A. Segment 540C in quadrant 524D falls inward, becoming a segment in quadrant 524A. The end of segment 520A in quadrant 524A is connected to ground 528, while the end of segment 540D in quadrant 524D is connected to output terminal 530, which is typically connected to an antenna. This configuration shown in enlarged portion 536 shows a waterfall transition between quadrants, and is repeated at each transition between quadrants.

[0136] exist Figure 5A and Figure 5B In this embodiment, the outermost segments of secondary winding 520 adjacent to primary winding 508 (such as shield segment 520A) serve as shields to suppress and reduce coupling from secondary winding 520 to primary winding 508. Other quadrants also have shield segments that are similar but not labeled with reference numerals. The shield segments are connected to ground 528. Due to ground connection 528, only a small portion of the total voltage developed in secondary winding 520 is adjacent to the primary winding. In this example configuration, each outermost segment is adjacent to primary winding 508 for only ¼ of a turn of the winding. Therefore, the voltage of the shield segment starts at the ground terminal (0 volts) and then advances ¼ of the distance of a complete turn as the outermost segment advances. Therefore, assuming a total output of 8 volts for the secondary winding, the maximum charge that can be accumulated by the secondary winding is ¼ of 8 volts, or 2 volts. This is true for each of the outermost segments. Therefore, the total reflection from the outermost segments of secondary winding 520 back to primary winding 508 is limited to 2 volts. As mentioned previously, reflections from the secondary winding to the primary winding and then into the amplifier can negatively impact amplifier performance, linearity, and can introduce unwanted harmonics.

[0137] In other words, the RF transformer has four quadrants (quarter-wave design), with four segments (strands) of wire in each quadrant. In each quadrant, the outer wire is connected in parallel as a shield to suppress and reduce coupling to the primary side. The other end of the shield structure is connected in series to one of the three freely available center wires of the other quadrant segment. These connections are repeated in all segments, creating a wiring diagram that looks like a waterfall, with the wire segments cascading at each transition between quadrants, as shown in the figure.

[0138] Although four quadrants and four segments per quadrant are shown, these values ​​can vary. Various designs are contemplated, such as an eight-wave design with eight quadrants and eight segments (strands) of wire in each quadrant. For a single primary winding turn, the eight segments include one shield segment adjacent to the primary winding and the other seven segments forming the remaining secondary winding. Because the primary winding sees a lower voltage from the secondary winding, a higher number of quadrants (divisions) improves performance but complicates wiring.

[0139] The final endpoints of the series-connected segments are connected together to form a single star point node in the center or any other arrangement. In this example, it is conveniently located in the center of the transformer, but other locations can also be considered to reduce the length of the output terminal connection. Although there are four segments of wire in each quadrant, the effective number of turns of each of the series-connected wire segments in this example is exactly equal to 1. It is worth noting that the uniqueness of this structure is that the ground connection 528 of each of the four outer segments is offset from its neighbors by 90 degrees (1 / 4 turn). It is also observed that only the grounded wire (segment) is close to the primary winding, and therefore any capacitive coupling from the single-ended side to the differential side is mostly the ground signal and a scaled-down single-ended signal.

[0140] Another important feature of this structure is that the maximum voltage swing seen at the outer conductors of the waterfall structure is now exactly one-quarter that of the conventional one-turn winding structure. The segments of the secondary winding are also almost evenly coupled to the differential side of the transformer. Specifically, two of the wire segments are coupled to the positive side of the primary winding, while the other two are coupled to the negative side of the primary winding.

[0141] As a result, the interference from the single-ended secondary winding to the differential primary winding is significantly lower than in conventional prior art transformers. The interference can also be seen by electronic circuits (such as amplifiers) connected to the primary side, but it will not appear as common-mode noise. Reducing the interference seen by the amplifier improves system linearity. This also results in greater power output, such as up to 1 dBm. If distortion is considered an important performance parameter, the increase in output power can be at least 3 dBm. This is a significant improvement because in prior art transformers, the interference seen by the differential circuit is essentially single-ended and has a greater magnitude than that seen in the newly disclosed structure.

[0142] Another beneficial feature of the winding structure disclosed herein is that each of the inner / center wire strands conducts generally the same amount of current as the outer strands (due to the series connection of these segments). On the other hand, due to the magnetic proximity and RF skin effect in conventional single-turn transformers operating at GHz frequencies, even with very thick wire, most of the current flows only on the surface of the thick wire immediately adjacent to the transformer's opposing winding. Consequently, the effective series resistance of a waterfall-configured (cascaded) multi-strand winding at higher GHz operating frequencies is many times smaller than that of a conventional transformer.

[0143] although Figure 5A 、 Figure 5B Only a transformer with four quadrants is shown, but any number D of quadrants is possible, where D is an integer equal to or greater than 1. For a one-turn transformer, with a one-turn coil and a double-sided shield, the number of segment conductors in each quadrant is equal to the number of quadrants plus 1 (i.e., D+1). Therefore, for D=2 (two quadrants), the number of segment conductors in each quadrant is 3. For N=3, the number of segment conductors in each quadrant is 4.

[0144] For a one-turn coil and a single-sided shield structure, the number of segment conductors in each quadrant is equal to the number of quadrants, i.e. (D). Therefore, for D = 2 (2 quadrants), the number of segment conductors (i.e., segments) in a quadrant is 2. For D = 3, the number of segment conductors in a segment is 3. Figure 5A With D = 4 shown, the number of segment conductors in a quadrant is 3, plus one segment conductor for shielding, for a total of 4 conductor segments in each of the 4 quadrants. For single-sided and double-sided shielding, the number of segments (conductors) in each quadrant can be increased or decreased to produce waterfall fractional-turn windings, as described below.

[0145] The higher the number of D (quadrants), the lower the imbalance in single-ended to differential signal injection. However, higher D values ​​will also result in higher self-capacitance seen in multi-strand conductors because the segments are in close proximity to each other. As D values ​​increase, the improvement in signal injection reduction rapidly decreases, while inter-winding self-capacitance rapidly increases. For maximum balance in single-ended to differential injection, it is also recommended to set N to an even number. Considering the above trade-offs, this means that for optimal operation, D can be 2, 4, 8, or larger, but other values ​​are also contemplated.

[0146] Figure 6 Shown Figure 5A An alternative embodiment of a segmented waterfall transformer is shown. This is just one possible configuration, and other configurations or shapes can be derived by one of ordinary skill in the art. Figure 5A 、 Figure 5BIn comparison, identical elements are labeled with the same reference numerals. In this embodiment, the primary winding 508 includes an outer primary winding 508A and an inner primary winding 508B. The outer primary winding 508A and the inner primary winding 508B are connected by a conductor 550, which can be on another layer or level so as not to be electrically connected to the secondary winding 520. As in all embodiments, when the primary winding extends onto the secondary winding, the two windings do not touch, thereby preventing the two windings from short-circuiting. The secondary winding 520 includes a shielding segment 520A, followed by three secondary winding waterfall segments 520B, 520C, and 520D that form a complete turn. This can be referred to as a self-shielding structure. In this embodiment, an innermost secondary shielding segment 554 is also shown. The innermost secondary shielding segment 554 is adjacent to the inner primary winding 508B to reduce coupling from the secondary winding to the primary winding 508B as described above. The waterfall structure 536, output terminal (antenna connection point) 530 and other aspects are generally similar to Figure 5A 、 Figure 5B Another important observation is that if a double-sided shielding structure is used, the number of wires per segment is theoretically less than Figure 5A The single-sided shield structure shown is one more.

[0147] It is also contemplated that the waterfall transformer may be configured with only the inner primary winding 508B ( Figure 6 ), and therefore does not include the external primary winding 508A ( Figure 6 ). In such an embodiment, the outer segment (conductor) in each quadrant can be removed as it acts as a shield between the secondary and primary windings. Figure 6 , in quadrant 524A, the outer secondary segment 520A may be removed.

[0148] In an example embodiment, the primary winding may have more than one winding. Thus, as Figure 5A The outer winding of the primary winding can be wound with two or more turns to increase the number of turns of the primary winding. This can be configured as Figure 2D and Figure 2E The primary winding is shown.

[0149] also, Figure 5A 、 Figure 5B and Figure 6 The example embodiment shows a 1:1 ratio transformer, however, the concepts of multi-stranding (segmenting) the transformer windings in a staggered offset manner and dropping the segments are also applicable to other transformer ratios (including non-integer transformer ratios previously thought to be impossible).

[0150] For example, if you design a 1:1.25 transformer, in addition to Figure 5AIn addition to what is shown in FIG, another conductor (conductor segment) is added in each quadrant of the winding. Figure 7 An example embodiment of an exemplary non-integer transformation ratio is shown. Figure 7 The shielded segment of the multi-stranded (segmented) winding (secondary winding 520A in quadrant 524A) is still used for shielding. However, each quadrant now has four waterfall segments (conductors), compared to the previous 1:1 transformer's three waterfall segments. The additional conductor segments 704 in each quadrant allow each series-connected conductor segment to now have a length of 1.25 turns. Once these four 1.25 full turns are connected in parallel, a 1:1.25 ratio transformer is created.

[0151] Although shown as a 1:1.25 ratio transformer, it is contemplated that the primary winding can be any value or number of turns greater than 1 or less than 1 (fractional and greater than zero). Likewise, although shown and described as having a value of 1.25 for the secondary winding, the secondary winding can be set to any value greater than 1, including fractional values ​​such as, but not limited to, 1.1, 1.2, 1.5, 1.75, 2.1, 2.25, 2.5, 2.75, 1:1 / 3, 1:2 / 3, 2:1 / 3, or any other value.

[0152] It is also contemplated that a 1:0.75 (or 0.75:1) ratio transformer (ratio less than 1) can be constructed by reducing the number of segments (wires) in each quadrant of the secondary winding by one wire. In this case, each of the series-connected winding segments is only 0.75 turns in length. In such an embodiment, Figure 5A The embodiment of will have one less segment in each quadrant. Thus, compared to the embodiment in which one segment is added per quadrant Figure 7 Differently, the 0.75 turns ratio reduces the number of segments by one, thus leaving the outer shield segment 520A ( Figure 5A ), and then two additional inner waterfall segments for a total of three segments in each quadrant. These values ​​are provided for example only. When implemented, as disclosed herein and understood by one of ordinary skill in the art, any value may be used.

[0153] Using this innovative winding technique, it is possible to construct differential to single-ended transformers of specific real (rather than integer) ratios while having the disclosed shielding structure. In one or more embodiments, the sum of all the windings in the series connection is equal to an integer multiple of the number of turns to ensure that the coupling coefficient of the resulting transformer is as close to the ideal value as possible. For example, there are no turns or segments that extend only a portion of the turns (the circumference of the winding). In other words, the sum of all the turns must be an integer. Figure 5A , each quadrant has four segments, and there are four quadrants, and each segment extends 1 / 4 turn.

[0154] Voltage differentials cause charge losses because current wants to flow through the wires, but at high frequencies, displacement currents also occur between the wires, depending on the voltage across them. Using shield segments, each of which is adjacent to the primary winding for only one quadrant, reduces displacement currents, thereby improving efficiency.

[0155] To calculate the number of turns after the waterfall is segmented, divide the number of segments by the number of quadrants. Figure 7 In the embodiment, there are a total of 5 segments / 4 quadrants in 360° turns, equivalent to a 1.25 turn winding. Note that if there is only one segment, it is similar to the fractional turn embodiment, which is formed as above in Figure 2A and Figure 3A For example, a total of 1 section / 4 quadrants – 1 / 4 turn winding. Figure 2A , has one segment and three quadrants, so it is a 1 / 3 turn winding.

[0156] For real-ratio transformers, the disclosed design is very useful for a variety of applications because the desired amount of maximum output power can be controlled by the number of turns in the RF transformer. Adjusting the output power by adding or subtracting fractional turns (segments) to create fractional turns ratios can greatly reduce the complexity required to achieve the desired maximum output power. For example, if slightly higher output power is desired, but the driver amplifier operates at high efficiency and high linearity, and it is preferred not to change the operating parameters to generate more power, the transformer can be slightly modified, such as by adding a 1 / 4 or 1 / 3 secondary winding to increase the transformer's output voltage, thereby increasing the transmitted power.

[0157] Figure 8A An alternative embodiment of a differential to single-ended transformer with a 1:2 turns ratio and 1 / 2 turn segment length is shown. Figure 5A In comparison, the same elements are indicated by the same reference numerals. In addition, the secondary winding and shielding structure use 1 / 2 winding quadrant, while the previous Figure 5A The example configuration shows a single-turn primary winding and a secondary winding with two shield segments in each quadrant (one on each side of the primary winding).

[0158] As described above, the primary winding 508 includes input terminals 512A, 512B. In this configuration, the secondary winding is divided into an inner secondary winding portion 808 and an outer secondary winding portion 804. In this example embodiment, a 1:2 ratio transformer is shown such that for every turn in the primary winding 508, there will be two turns 804, 808 in the secondary winding. Thus, in this example embodiment, the secondary winding is replicated but rotated such that there is an outer secondary winding portion 804 located outside the primary winding 508 and an inner secondary winding portion 808 located inside the primary winding. These two sets of secondary turns 804, 808 are offset 90 degrees from each other and are electrically coupled in parallel.

[0159] As shown, for the inner secondary winding portion 708, a waterfall structure exists at a first waterfall transition 812 and a second waterfall transition 816. The waterfall transitions 812, 816 separate the two sections 824A, 824B of the inner secondary winding portion 808. For the outer secondary winding portion 804, a waterfall structure exists at a first waterfall transition 828 and a second waterfall transition 832. The waterfall transitions 828, 832 separate the two segment groups 820A, 820B of the outer secondary winding portion 804 (as shown, the right and left quadrants).

[0160] The inner secondary winding portion 808 has two shield segments 840A, 840B adjacent to the primary winding 508. The shield segments 840A, 840B function as described above. The outer secondary winding portion 804 has two shield segments 836A, 836B adjacent to the primary winding 508. The shield segments 836A, 836B function as described above.

[0161] In an equivalent circuit, the secondary windings 804, 808 would consist of four two-turn windings arranged in parallel. This is generally equivalent to winding two turns with a wire four times thicker. From a transformer ratio perspective, the circuit is indeed a 1:2 transformer. However, in the disclosed embodiment, it has built-in shielding structures 836A, 836B, 840A, 840B to significantly reduce single-ended coupling from the secondary windings 804, 808 to the primary winding 508.

[0162] Summarizing FIG8 , the transformer includes a “dual” 2-turn secondary winding consisting of multiple strands of wire (segments) divided into 1 / 2 turn (circle) segments. Each segment (wire) is connected in such a way that the high voltage node is shielded by the outermost segment connected to the ground pin 528. Internally, some of the high voltage segments are also shielded to the next low voltage wire to reduce the effective self-capacitance on the secondary turns. The term “dual” refers to the duplication of the secondary windings 804 , 808 . One secondary winding turn is located inside the primary winding 508 , while the other secondary winding turn is located outside the primary winding. The secondary windings 804 , 808 are identical to each other, but one of them is offset by 90 degrees to spread the single-ended signal coupling more evenly onto the differential primary winding 508 .

[0163] In this example, a single-sided shield structure is shown. The shield is placed next to the primary winding 508. If additional primary winding turns are added inside and / or outside the structure of Figure 8, additional ground shielding can be added (in addition to the shield segments 836A, 836B, 840A, 840B).

[0164] All output end terminals are connected to a center point or terminal 530 for a balanced connection, such as to an antenna (not shown). All ground terminals 528 are connected together to an external ground or another multi-point connection.

[0165] The primary winding may have more than one turn and may have center taps or fractional turns and any combination. In this example, only one turn of the primary winding is shown.

[0166] Figure 8B A differential input and differential output transformer with a waterfall transition is shown. In this example embodiment, the number of quadrants, segments, and turns is merely exemplary, and other embodiments with different configurations can be created without departing from the inventive concept. The figure shows a differential input and differential output transformer with a waterfall transition. When configuring a differential output (as opposed to a single-ended output), the coupling between the positive and negative terminals of the secondary winding must be equal, but with opposite polarity, to match the differential input, which also has two terminals with opposite polarity.

[0167] In this embodiment, the primary winding 850 includes a positive polarity input 854A and a negative polarity input 854B. The secondary winding is divided into two quadrants, each separated by a waterfall transition. On the outside of the primary winding 850 are two outer segments 858 of the secondary winding, while on the inside of the primary winding are two inner segments 862. The secondary winding has two negative polarity output terminals 866A, 866B and two positive polarity output terminals 872A, 872B.

[0168] Tracing each conductive path reveals that the primary winding 850 is one turn, while the secondary winding is two turns. For example, starting from the negative output terminal 866A, the winding progresses, forming a complete two turns before reaching the positive output terminal 872A. Similarly, starting from the negative output terminal 866B, the winding progresses, forming a complete two turns before reaching the positive output terminal 872B. These two paths are connected in series, making the transformer ratio a 1:2 transformer. Each winding is divided into two parallel turns to form a 1 / 2 wave waterfall structure. The center tap node 880 is set in the middle of each turn (midway), and it is a virtual ground located in the middle of the positive and negative terminals of each winding. The winding closest to the center tap becomes the shield.

[0169] Each output has opposite polarity and is balanced because each two turn paths (866A to 872A and 866B to 872B) have equal coupling. The outer segment 858 and the inner segment 862 form the secondary winding and are arranged so that the segments run in opposite directions from each positive terminal 872A, 872B. Therefore, if starting from either positive output terminal 872A, 872B, the turns run in a counterclockwise direction. Conversely, if starting from the negative output terminal 866A, 866B, the turns run in a clockwise direction. This maintains that the signals at the positive output terminals 872A, 872B of the secondary winding have opposite polarity to the signals at the negative output terminals 866A, 866B.

[0170] Figure 8C yes Figure 8B The circuit representation of the transformer. Figure 8B Each winding is two separate windings connected in parallel, with a center tap terminal 880 .

[0171] As mentioned above, the segment closest to the primary winding 850 still acts as a shield, limiting reflections from the secondary winding to the primary winding. Note that because this embodiment has two quadrants, it reduces the voltage seen by the primary winding from the secondary winding by 1 / 2.

[0172] Stacked windings with waterfall transitions and shielded segments

[0173] The present invention also discloses that the transformer windings and shielding can be in a stacked configuration. In a stacked configuration, the various components of the transformer are stacked one on top of the other. Figure 5A - In contrast to the embodiment of FIG8 , Figure 5A - In the embodiment of Figure 8, the transformer components are generally in one plane or layer (except for the interconnections). Figure 9A A side perspective view of the stacked layers of an example transformer embodiment is shown. Figure 9AAs shown, the substrate 904 of the semiconductor device serves as a supporting layer or base layer. The disclosed transformer can also be placed on top of an amplifier or other circuit element. The substrate can include silicon, ceramic, organic material, glass, or any other base layer or insulator used in semiconductor devices. The substrate can be part of an integrated circuit die, a printed circuit board, or a semiconductor package. Above the substrate 904 is a thick insulating layer 906. The next layer above the insulating layer 906 is a primary winding 908 formed of a conductive material, which is configured as shown in FIG. Figure 9B As shown. Covering the primary winding 908 is an insulating layer 910. Adjacent to the primary winding 908 away from the base 904 and on top of the insulating layer 910 is a shield portion 912, which is typically a grounded conductive layer. Covering the primary winding 908 is an insulating layer 914 covering the shield portion 912. Adjacent to the shield 912 away from the base 904 and on top of the insulating layer 914 is a secondary winding 916. Secondary winding segments 916A, 916B, 916C are stacked on the shield layer and can all be arranged in one plane or layer. Thus, the secondary winding segments 916A, 916B, 916C ( Figure 9D ) can be primarily in a single plane and arranged above the shield 912, in addition to a waterfall structure, which can use one or more vias or jumpers 902 to extend upward (or downward) and over the traces of the primary winding or secondary winding. The jumper 902 connects the shield 912 to the segment 916A. Although shown as stacked upward from the base 904, it is contemplated that the stack can be rotated in any direction (such as, for example, 180 degrees) so that the components are stacked downward. What is important is the layered (non-planar) geometry of the windings and shield, and that the high voltage winding is farther from the base than the low voltage winding.

[0174] Note that in this embodiment the primary winding layer 908, which is at a lower voltage than the secondary winding layer 916, is closer to the substrate 904. This reduces interference and improves performance. If the secondary winding is at a lower voltage than the primary winding, then the secondary winding can be closer to the substrate than the primary winding.

[0175] Figure 9B 、 Figure 9C and Figure 9D A top view of the stacked layers of an exemplary stacked transformer embodiment is shown separated. This is only one possible configuration and shape, and one skilled in the art can devise any different embodiment without departing from the concepts and claims of the present invention. Each of the layers is stacked on top of another and is generally aligned along a central axis. Figure 9BAs shown, the first layer is the primary winding layer 908. In this embodiment, a single turn forms the primary winding conductive layer 920. The width of the conductor is based on at least the number of turns in the secondary winding, the width of the secondary winding, the available space, and the desired amount of coupling. The conductive layer of the primary winding 920 has two terminals 924A, 924B.

[0176] Covering the primary winding 920 is an insulating layer (now shown). The insulating layer prevents the primary winding 920 from shorting to the shield / secondary winding. Any type of non-conductive material can be used for the insulating layer.

[0177] Above the primary winding 920 and its associated insulation layer (not shown) is the shielding layer 912. Figure 9C In this embodiment, the shielding layer includes four conductive ground pads 930A, 930B, 930C, and 930D ​​connected to ground 934. There is a gap 938 or space between each ground pad 930A, 930B, 930C, and 930D. Figure 9D The four conductive ground pads 930A, 930B, 930C, 930D ​​also have connection points 942A, 942B, 942C, 942D, which are connected to Figure 9D The secondary winding is shown. The shielding layer 912 reduces or prevents coupling from the secondary winding to the primary winding.

[0178] Figure 9D The top layer 916 of the stacked transformer is shown. The top layer 916 includes the secondary winding. In this embodiment, the secondary winding has four quadrants, and in each quadrant there are three parallel connected segments 944A, 944B, 944C. The secondary winding has a ground connection point 946 that runs down toward the shield 912 to connect to the connection point 942. The opposite terminal 950 of the secondary winding can be connected to an antenna or other circuit element. This design shares similar Figure 5B The waterfall structure shown.

[0179] Figure 9E Shown is a side perspective view of stacked layers of an exemplary stacked transformer configuration. Figure 9A The reference numerals in the Figure 9E , to aid understanding. As shown, the substrate is at the bottom level. The substrate can extend for a distance in all directions. Covering the substrate is an insulating layer 906. This insulating layer can be quite thick to prevent coupling or interference between the substrate and the metal layers of the transformer. Above insulating layer 906 is a portion of primary termination 908, which has a thickness of T1. Above primary winding portion 908 is additional insulating material 910, and on top of the insulating material is a shielding portion 912, which has a thickness of T2.

[0180] Above the shield portion 912 are segments 916A, 916B, 916C of the secondary winding. Connecting the outermost segment 916A to the shield segment 912 is a jumper 902, which may also be referred to as a via. Above the secondary windings 916A, 916B, 916C is additional insulating material 918.

[0181] One benefit of the stacked transformer configuration is that it places the secondary winding farther from the substrate. This improves performance compared to designs that place the waterfall structure near the substrate or at the same distance from the substrate as other transformer components (such as on the same plane). In some embodiments, the secondary winding is at a higher voltage than the primary winding, and performance can be improved by positioning the secondary winding farther from the substrate.

[0182] As used herein, the term "quadrant" is defined as a sector or divided portion of a winding and is not limited to the term "quad" which means four. Thus, since the secondary winding is divided into three quadrants, the embodiment of FIG. 9 has three quadrants, each separated by a waterfall structure. Furthermore, although the primary and secondary windings and the shielding structure are shown as circular, it is disclosed that in any embodiment disclosed herein, these elements may be any shape other than circular, such as a square, triangle, octagon, hexagon, ellipse, pentagon, or any other shape or combination of shapes. As will be appreciated by one of ordinary skill in the art, the manufacture of circular shapes in integrated circuits may be more challenging than linear shapes.

[0183] Transformer having a line-shaped structure as a winding portion

[0184] FIG10A shows a perspective view of a prior art conductive trace (wire) having a height-to-width ratio suitable for an integrated circuit. In this embodiment, conductive trace 1004 is typical of a primary or secondary winding that may be used in a transformer as disclosed herein. Due to semiconductor process limitations, the ratio of height H 1008 to width W 1012 of conductive trace 1004 is approximately 1:1. Therefore, H=W. This is a general ratio that varies with the manufacturing process and the process itself. For a given material and ratio of height H 1008 to width W 1012, conductive trace (wire) 1004 has a set trace resistance / trace distance.

[0185] In order to reduce the resistance, it has been proposed to increase the height of the conductive traces without increasing their width. In many applications, it is not possible or desirable to increase the width of the conductive traces forming the windings in a transformer as this would affect the performance of the transformer. Figure 10BA perspective view of a conductive trace is shown, illustrating the improved aspect ratio on the integrated circuit. This configuration may be referred to herein as stacked metal layers with vias. As shown, conductive trace 1020 has the same width W 1012 as the configuration of FIG. 10A , but the height is composed of three stacked layers 1024, 1028, and 1032. The height H of layer 1032 is the metal layer height MLH. Conductive layer 1032 has the same general height 1008 as layer 1004 in FIG. Atop conductive layer 1032 is a scribe-line-like structure 1028 formed of conductive material, which is formed by a row of electrically connected vias. The height H of layer 1028 is the via height VH. Layer 1028 can be any manufacturable height, but is typically about ½H. Scribe lines are described in U.S. Publication No. US2014 / 0077320, entitled Scribe Lines in Wafers, published on March 20, 2014, the entire contents of which are incorporated herein by reference. Placing one or more rows of electrically connected vias on top of metal layer 1232 allows for the build-up of two or more metal layers 1024, 1232. Placing metal layer 1024 directly on metal layer 1232 is not permitted in semiconductor manufacturing processes or would increase the cost of the manufactured semiconductor device, but using a scribe-like structure between metal layers allows for increased transformer winding height.

[0186] On top of the via layer 1028 is another metal layer 1024. The height H of layer 1032 is the metal layer height MLH. Layer 1032 has the same general height 1008 as layer 1004 in FIG. 10A. As a result, although the width W 1012 of the conductive trace 1020 is the same as the width 1012 shown in the prior art (FIG. 10A), the height is much greater, in this embodiment MLH + VH + MLH, which is approximately 2.5 times the height of the prior art embodiment.

[0187] The additional height of the conductive traces forming the transformer windings results in the traces having a lower resistance / impedance for a given length compared to prior art windings. As discussed above, this provides additional benefits associated with lower resistance / impedance.

[0188] Figure 11A A top view of an exemplary transformer winding with crossover features is shown. This configuration is shown for discussion purposes. Through-hole stacked metal layers can be used to form any winding or conductive path shown or described herein. Figure 11A, the winding is a two-turn winding having a first turn 1104 and a second turn 1108. Turns 1104, 1108 cross at region 1112. The turns have terminals 1120A, 1120B. As shown, winding portion 1160A crosses to become winding portion 1160B. Winding portion 1164A crosses to become winding portion 1164B.

[0189] Figure 11B Shown Figure 11A A side view of a portion of an exemplary transformer winding is shown. Figure 11B The parts shown in Figure 11A As shown, winding section 1160A crosses to become winding section 1160B. Winding section 1164A crosses to become winding section 1164B. These reference numerals and elements may be found in Figure 11A 1134 are cross-referenced to aid understanding. Layers 1130 and 1138 are metal (conductive) layers, while layer 1134 is a scribe-like structure of electrical connections and conductive vias that electrically connect metal layers 1130 and 1138. Between the layers is a gap or space 1142, which is typically an insulating material. Also shown are metal layer 1146, a via scribe layer 1150, and a metal layer 1154. Via layer 1150 is located between and electrically connected to metal layers 1146 and 1154. Power and ground lines can also be configured with stacked metal and scribe-like structures.

[0190] At intersections 1160, specific layers are omitted to allow windings to cross and overlap without shorting the stacked conductive layers. The intersection area can be filled with oxide, an exemplary insulator. Thus, via layer 1134 and metal layer 1138 are removed, and via layer 1150 and metal layer 1154 are removed. In this open area 1160, at the intersection, the outer winding becomes the inner winding, and the inner winding becomes the outer winding.

[0191] Figure 12 Another configuration of the primary and secondary winding structures is shown.As discussed herein, the physical shapes of the various transformer primary windings, shielding structures, and secondary windings can take a variety of shapes and configurations. Figure 12 The diamond shape is one such configuration that includes the primary winding 1212 and the two terminals 1208A, 1208B. A square, diamond, or other more linear shape may be preferred when laying out the circuit mask and depositing the integrated circuit. This shape and configuration can be used with any of the embodiments disclosed herein, as well as additional embodiments derived therefrom. Although a primary winding is shown, based on the teachings of other embodiments, the shielding structure and the secondary winding can have substantially similar shapes to allow the primary winding to be in close proximity to the secondary winding, which in turn maximizes the coupling coefficient.

[0192] Figure 13 A square or diamond shaped waterfall winding configuration is shown. As mentioned above, in many cases the shape of the transformer is not limited to a specific geometry or configuration. Figure 13 An example configuration of a waterfall winding structure 1304 is shown in a square or diamond configuration. This is a four-quadrant configuration with an output terminal 1308 and a ground terminal 1312. Each quadrant is separated by a waterfall transition 1316. In this embodiment, the ground terminal 1312 is located in the interior region of the winding, so the other windings (primary or secondary) will be located in the interior region adjacent to the shield segment connected to the ground 1312.

[0193] Figure 14 A top view of the components of a stacked transformer with a waterfall transition is shown. In this embodiment, a text callout is provided to aid understanding and provide additional disclosure. Due to the limitations of the patent figures, the primary winding (coil) is offset to provide a better visual representation. When configured for operation, the primary winding (coil) will align with the shield segment and the secondary winding segment.

[0194] Although various embodiments of the present invention have been described, it will be apparent to those skilled in the art that more embodiments and implementations are possible within the scope of the present invention. In addition, the various features, elements, and embodiments described herein may be protected or combined in any combination or arrangement.

Claims

1. A transformer, comprising: a primary winding comprising one or more conductors having two or more terminals; a secondary winding adjacent to the primary winding, the secondary winding comprising one or more turns such that each turn is divided into two or more segments, the two or more segments comprising a shield segment proximate the primary winding and one or more waterfall segments, wherein the length of each of the two or more segments is less than a complete turn, which reduces impedance, and parallel connection of the two or more segments further reduces impedance compared to the impedance of a complete turn; The shield segment is grounded at a first shield segment end of the shield segment and connected to one of the one or more waterfall segments at a second shield segment end of the shield segment; The one or more waterfall segments have a first waterfall segment end and a second waterfall segment end; The first waterfall segment end is connected to the second shield segment end or another first waterfall segment end; and The second waterfall segment end is connected to another first waterfall segment end or an output node of the secondary winding; and The one or more waterfall segments are further from the primary winding than the shield segment; The grounded shielding segment is configured to shield the primary winding from reflection of the voltage on the secondary winding.

2. The transformer according to claim 1, wherein: The transformer is part of a printed circuit board, a ceramic substrate, a semiconductor package, or a semiconductor die containing an integrated circuit.

3. The transformer according to claim 1, wherein: The primary winding, the secondary winding, or both are formed from two or more metal layers shorted together by a scribe-like structure.

4. The transformer according to claim 1, wherein: Where the second waterfall segment end is connected to an output node of the secondary winding, the output node is connected to an antenna.

5. The transformer according to claim 1, wherein: There is one shield segment in each turn.

6. The transformer according to claim 1, wherein: The primary winding has one or more shield segments and two or more waterfall segments.

7. The transformer according to claim 1, wherein: Each turn is divided into quadrants, and for a 1:1 turns ratio, the number of segments in each quadrant is equal to the number of quadrants.

8. The transformer according to claim 1, wherein: Each turn is divided into a number of quadrants, and for a turns ratio of 1:>1, the number of segments in each quadrant is greater than the number of quadrants.

9. The transformer according to claim 1, wherein: Each turn is divided into a number of quadrants, and for a turns ratio of 1:<1, the number of segments in each quadrant is less than the number of quadrants.

10. A transformer comprising: substrate; an insulating material covering the substrate; a primary winding located on an insulating material covering the substrate, the primary winding being formed of a conductive material having a first terminal and a second terminal; an insulating material covering the primary winding; two or more shield sections positioned on the insulating material covering the primary winding and aligned with the primary winding, each of the two or more shield sections having a ground connection point and a connection point to two or more secondary windings; an insulating material covering the two or more shielding portions; as well as a secondary winding located on the insulating material covering the two or more shielding portions and aligned with the primary winding and the two or more shielding portions, the secondary winding being formed of two or more conductive segments connected by a waterfall structure, the secondary winding having two or more secondary winding connection points and two or more output terminals, the two or more secondary winding connection points being connected to the two or more shielding portions, Wherein, the length of each of the two or more shielding portions is less than a complete turn, which reduces impedance, and the parallel connection of the two or more shielding portions further reduces impedance compared to the impedance of a complete turn.

11. The transformer according to claim 10, wherein: The primary winding, the secondary winding, or both are formed from two or more stacked metal layers shorted together by a scribe-like structure.

12. The transformer according to claim 10, wherein: The two or more shield portions include a spacer between each shield portion, and the spacer is aligned with the waterfall structure.

13. The transformer according to claim 10, wherein: The transformer is configured as one of: part of a printed circuit board, part of a semiconductor package, part of a semiconductor die containing an integrated circuit.

14. The transformer according to claim 10, wherein: The thickness of the insulating material covering the two or more shielding portions is two or more layers thick.

15. An integrated transformer, comprising: a first winding formed of a conductive material having a first terminal and a second terminal; an insulating material covering the first winding; two or more shield sections positioned above and aligned on the first winding, each of the two or more shield sections having at least one ground connection point and a connection point to at least one second winding; an insulating material covering the two or more shielding portions; as well as a second winding positioned above and aligned on the first winding and the two or more shield portions, the second winding being formed from two or more conductive segments including at least one electrical connection to the at least one second winding connection point, Wherein, the length of each of the two or more shielding portions is less than a complete turn, which reduces impedance, and the parallel connection of the two or more shielding portions further reduces impedance compared to the impedance of a complete turn.

16. The transformer according to claim 15, wherein: The first winding, the second winding, or both are formed from two or more stacked metal layers shorted together by a scribe-like structure.

17. The transformer according to claim 15, wherein: The output terminal of the first winding or the second winding is connected to one of the following: an antenna, a receiver, an amplifier.

18. The transformer according to claim 15, wherein: The second winding is divided into N quadrants, and each quadrant contains M segments, where N is an integer greater than 2, and M is an integer greater than 2.

19. The transformer according to claim 15, wherein: The first winding, the second winding, or both include a waterfall transition structure.

20. The transformer according to claim 19, wherein The two or more shield portions include a spacer between each shield portion, and the spacer is aligned with the waterfall transition structure.

21. The transformer according to claim 15, wherein: The transformer is configured as one of: part of a printed circuit board, part of a semiconductor package, part of a semiconductor die containing an integrated circuit.

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