On-chip magnetic coil and three-dimensional on-chip magnetic sensor including on-chip magnetic coil

Abstract

an on-chip electrical coil comprising: a semiconductor substrate; a plurality of metal layers disposed on the semiconductor substrate; a plurality of insulating layers disposed on the semiconductor substrate; a plurality of metal vias defined in the insulating layers; and a plurality of planar spirals formed by the metal layers and the metal vias, wherein each insulating layer is disposed between an adjacent pair of metal layers to form an alternating arrangement of metal layers and insulating layers, and each metal via electrically connects each adjacent pair of metal layers; the planar spirals include a plurality of interconnected loops, each loop including two metal wires, an intra-loop column, and an inter-loop column, wherein the two metal wires are disposed within respective metal layers, the intra-loop column electrically connects the two metal wires of each loop to each other, and the inter-loop column electrically connects one of the metal wires of each loop to one of the metal wires of a loop subsequent to the loop.

Description

[Technical Field]

[0001] Cross-Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 443,576, entitled "Spatial Encoding Using AC Magnetic Field Gradients for Localization of Microdevices," filed February 6, 2023, and U.S. Provisional Patent Application No. 63 / 443,592, entitled "Monolithic 3D Sensor in CMOS for AC Field Sensing by Electromagnetic Induction," filed February 6, 2023, which are incorporated herein by reference.

[0002] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH This invention was made with government support under Grant No. CBET1823036 awarded by the National Science Foundation. The United States Government has certain rights in this invention.

[0003] Technical Field This application generally relates to magnetic sensors for three-dimensional position measurement using oscillating magnetic field gradients generated by alternating current. [Background technology]

[0004] Magnetic sensors have become increasingly ubiquitous, as they form an integral part of several fast-growing fields such as automobiles, navigation, robotics, medical devices, power grids, industrial applications, consumer electronics, and space equipment. Examples of magnetic sensors that have been developed for these applications include Hall sensors, semiconductor magnetoresistors, fluxgate sensors, resonant sensors, inductive-based magnetometers, and superconducting quantum interference devices (SQUIDs).

[0005] Hall sensors are one of the most widely used types of magnetic sensors due to their compatibility with standard, low-cost complementary metal-oxide-semiconductor (CMOS) fabrication processes. Recently, Hall sensors have been used for magnetic gradient-based navigation and tracking of microdevices in different biomedical applications. However, one of the major challenges of CMOS-based Hall sensors is their relatively low sensitivity due to the low Hall coefficient of silicon. To achieve better sensitivity, the Hall sensors need to be biased at higher current levels, which hinders their widespread use in low-power bioelectronics and other power-constrained applications. Another challenge is the difficulty of realizing highly sensitive 3D (three-dimensional) Hall sensors using standard CMOS fabrication processes. This is often overcome by using ferromagnetic materials, which require additional and expensive steps during the fabrication process, thus increasing complexity and cost. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 1,145,7835 Summary of the Invention [Means for solving the problem]

[0007] The preferred embodiments described herein have innovative features, none of which, taken alone, is essential to, or solely responsible for, the desirable attributes of, those features. The following description and drawings set forth in detail exemplary implementations of the invention, which illustrate some representative ways in which various principles of the invention may be practiced. However, these illustrative examples do not exhaust the many possible embodiments of the invention. Without limiting the scope of the claims, some of these advantageous features will now be summarized. Other objects, advantages, and novel features of the invention will be described in the following detailed description of the invention when considered in conjunction with the drawings, which are intended to illustrate, but not limit, the invention.

[0008] One aspect of the present invention is directed to an on-chip electrical coil comprising: a semiconductor substrate; a plurality of metal layers disposed on the semiconductor substrate; a plurality of insulating layers disposed on the semiconductor substrate; a plurality of metal vias defined in the insulating layers; and a planar spiral formed by the metal layers and the metal vias, wherein each insulating layer is disposed between an adjacent pair of metal layers to form an alternating arrangement of metal layers and insulating layers, and each metal via electrically connects each adjacent pair of metal layers, and the planar spiral includes a plurality of interconnected loops, each loop including two metal wires, an intra-loop column, and an inter-loop column, wherein the two metal wires are disposed within respective metal layers, the intra-loop column electrically connects the two metal wires of each loop to each other, and the inter-loop column electrically connects one of the metal wires of each loop to one of the metal wires of a loop subsequent to the loop.

[0009] In one or more preferred embodiments, the two metal wires of each loop have a respective length measured along a first axis, a respective width measured along a second axis perpendicular to the first axis, and a respective height measured along a third axis perpendicular to the first and second axes, the two metal wires of each loop being spatially offset from one another along the third axis, and the respective lengths of the metal wires being greater than the respective widths. In one or more preferred embodiments, the length-to-width ratio of each metal wire is about 500:1 to about 10,000:1. In one or more preferred embodiments, each loop extends parallel to a plane defined by the first and third axes.

[0010] In one or more embodiments, the plurality of interconnected loops includes a first and a second loop, with the two metal wires of the second loop disposed between the two metal wires of the first loop. In one or more embodiments, the two metal wires of the first loop include an upper metal wire disposed in an upper metal layer and a lower metal wire disposed in a lower metal layer; the two metal wires of the second loop include a third metal wire disposed in a third metal layer and a fourth metal wire disposed in a fourth metal layer, the third and fourth metal layers being between the upper and lower metal layers; the first loop includes a column within the first loop electrically connecting the upper and lower metal layers; the column within the first loop includes at least a first metal segment of the third metal layer, a first metal segment of the fourth metal layer, a first metal via electrically connecting the upper metal wire to the first segment of the third metal layer, a second metal via electrically connecting the first segment of the third metal layer to the first metal segment of the fourth metal layer, and a third metal via electrically connecting the first segment of the fourth metal layer to the lower metal wire. The first loop includes a first inter-loop column electrically connecting the upper metal wire to the fourth metal wire, and the first inter-loop column includes at least a second metal segment of a third metal layer, a third metal via electrically connecting the upper metal wire to the second metal segment of the third metal layer, and a fourth metal via electrically connecting the second metal segment of the third metal layer to the fourth metal wire.

[0011] In one or more embodiments, the planar helix is ​​a first planar helix, and the on-chip electrical coil further includes a second planar helix electrically connected to the first planar helix, the interconnected loops of each planar helix wound around an axis, the first and second planar helixes being spatially offset from one another along the axis. In one or more embodiments, the on-chip electrical coil further includes a plurality of planar helixes, the interconnected loops of each planar helix wound around the axis, the multiple planar helixes being spatially offset from one another along the axis, and adjacent planar helixes being electrically connected to one another. In one or more embodiments, the on-chip electrical coil further includes a plurality of intra-helical connecting wires, each intra-helical connecting wire electrically connecting a first terminal to a second terminal of an adjacent planar helix.

[0012] In one or more embodiments, the axis is a first axis, the length of the on-chip electrical coil is measured along the first axis, the height of each planar spiral is measured along a second axis, each planar spiral is parallel to a plane defined by the first and second axes, and the length of the on-chip electrical coil is greater than the height of each planar spiral. In one or more embodiments, the ratio of the length of the on-chip electrical coil to the height of each planar spiral is between about 50:1 and about 250:1.

[0013] Another aspect of the invention is directed to an on-chip magnetic sensor comprising: a semiconductor substrate; a plurality of metal layers disposed on the semiconductor substrate; a plurality of insulating layers disposed on the semiconductor substrate; a plurality of metal vias defined in the insulating layers; a first conductive coil having a first planar spiral formed by the metal layers and the metal vias; and a second conductive coil having a second planar spiral formed by at least a portion of the metal layers and at least a portion of the metal vias, wherein the metal layers are spaced apart along a first axis, each insulating layer is disposed between an adjacent pair of the metal layers to form an alternating arrangement of metal layers and insulating layers, each metal via electrically connects a respective adjacent pair of the metal layers, the first planar spiral includes a plurality of interconnected first loops wound about a second axis orthogonal to the first axis, and the second planar spiral includes a plurality of interconnected second loops wound about the second axis.

[0014] In one or more embodiments, at least a portion of the metal layer and at least a portion of the metal vias form a continuous metal structure along the entire length of the second planar spiral along the second axis. In one or more embodiments, the on-chip magnetic sensor further includes a third conductive coil having a third planar spiral formed by the metal layer and the metal vias, the third planar spiral including a plurality of interconnected third loops wound around a third axis orthogonal to the first and second axes. In one or more embodiments, each of the interconnected first loops and each of the interconnected third loops includes a respective metal wire pair, a respective intra-loop column, and a respective inter-loop column, each metal wire pair disposed in a respective metal layer, each intra-loop column electrically connecting each metal wire pair in each interconnected loop, and each inter-loop column electrically connecting one metal wire of the metal wire pair in each interconnected loop to one metal wire of the metal wire pair in the interconnected loop subsequent to the first interconnected loop.

[0015] Another aspect of the invention is directed to a three-dimensional on-chip magnetic sensor comprising: a semiconductor substrate; a plurality of metal layers disposed on the semiconductor substrate; a plurality of insulating layers disposed on the semiconductor substrate; a plurality of metal vias defined in the insulating layers; a first conductive coil having a plurality of first planar spirals formed by the metal layers and the metal vias; a second conductive coil having a plurality of second planar spirals formed by the metal layers and the metal vias; and a third conductive coil having a third planar spiral formed by at least a portion of the metal layers and at least a portion of the metal vias, wherein each insulating layer is formed by a pair of adjacent metal layers. disposed between the layers to form an alternating arrangement of metal layers and insulating layers, each metal via electrically connecting a respective adjacent pair of metal layers, each first planar spiral including a plurality of interconnected first loops wound about a first axis, adjacent first planar spirals being electrically connected to one another, each second planar spiral including a plurality of interconnected second loops wound about a second axis orthogonal to the first axis, adjacent second planar spirals being electrically connected to one another, and a third planar spiral including a plurality of interconnected third loops wound about a third axis orthogonal to the first and second axes, the metal layers being spaced apart along the third axis.

[0016] In one or more embodiments, the first planar spirals are spatially offset from one another along a first axis, and the second planar spirals are spatially offset from one another along a second axis. In one or more embodiments, the three-dimensional on-chip magnetic sensor further comprises a plurality of first intra-spiral connecting wires; and a plurality of second intra-spiral connecting wires, each of which electrically connects a first terminal to a second terminal of an adjacent first planar spiral, and each of which electrically connects a first terminal to a second terminal of an adjacent second planar spiral.

[0017] In one or more embodiments, a catheter is attached to the three-dimensional on-chip magnetic sensor. In one or more embodiments, a guidewire is attached to the three-dimensional on-chip magnetic sensor.

[0018] For a more complete understanding of the nature and advantages of the concepts disclosed herein, reference is made to the detailed description of the preferred embodiment and the accompanying drawings. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a block diagram of a three-dimensional (3D) position measurement system using an alternating current generated oscillating magnetic field gradient, according to one embodiment. [Figure 2] FIG. 2 is a top view of the 3D magnetic field sensor shown in FIG. 1 according to one embodiment. [Figure 3] FIG. 3 illustrates a cross section of a spiral within the first conductive coil shown in FIG. 2 according to one embodiment. [Figure 4] 3 illustrates a cross section of a spiral within the first conductive coil shown in FIG. 2 according to another embodiment. [Figure 5] 3 illustrates a cross section of a spiral within the first conductive coil shown in FIG. 2 according to another embodiment. [Figure 6] 3 illustrates a cross section of a spiral within the first conductive coil shown in FIG. 2 according to another embodiment. [Figure 7] FIG. 3 illustrates a cross section of a spiral within the second conductive coil shown in FIG. 2 according to one embodiment. [Figure 8] 3 illustrates a cross section of a spiral within the second conductive coil shown in FIG. 2 according to another embodiment. [Figure 9] 3 illustrates a cross section of a spiral within the second conductive coil shown in FIG. 2 according to another embodiment. [Figure 10] 3 illustrates a cross section of a spiral within the second conductive coil shown in FIG. 2 according to another embodiment. [Figure 11] FIG. 3 is a top view of the third conductive coil shown in FIG. 2 according to one embodiment. [Figure 12] FIG. 3 is a top view of the third conductive coil shown in FIG. 2 according to another embodiment. [Figure 13] FIG. 12 illustrates a first cross section of the helix in the third conductive coil shown in FIG. 11 according to one embodiment. [Figure 14]FIG. 12 illustrates a first cross section of a spiral within the third conductive coil shown in FIG. 11 according to another embodiment. [Figure 15] FIG. 12 illustrates a second cross section of the helix in the third conductive coil shown in FIG. 11 according to one embodiment. [Figure 16] FIG. 12 illustrates a second cross section of the helix within the third conductive coil shown in FIG. 11 according to another embodiment. [Figure 17] FIG. 10 is a block diagram of an equivalent circuit formed within a semiconductor chip of a 3D magnetic field sensor for the first and second conductive coils. [Figure 18] FIG. 18 is a circuit diagram of the instrumentation amplifier shown in FIG. [Figure 19] FIG. 19 is a circuit diagram of the Gm1 block of the instrumentation amplifier shown in FIG. 18. [Figure 20] Figure 20A is a graph showing measured input referred noise (IRN) as a function of frequency for the instrumentation amplifier shown in Figure 17. Figure 20B is a graph showing gain as a function of frequency. [Figure 21] FIG. 10 is a block diagram of an equivalent circuit formed in a semiconductor chip of the 3D magnetic field sensor for the third conductive coil. [Figure 22] FIG. 18 is a circuit diagram of the bandpass filter shown in FIG. 17, according to one embodiment. [Figure 23] FIG. 18 is a circuit diagram of the programmable gain amplifier shown in FIG. 17, according to one embodiment. [Figure 24] 24A and 24B are circuit diagrams of a differential positive peak detect and hold circuit according to one embodiment. [Figure 25] 24A and 24B are circuit diagrams of the Gm3 stage of the differential positive peak detect and hold circuit and the differential negative peak detect and hold circuit, respectively. [Figure 26] Figure 26A shows a sampling clock synchronized with the peaks of the EMF signal, and Figure 26B is a graph of the output of the programmable gain amplifier and the output of the peak detect and hold circuit. [Figure 27] FIG. 18 is an example of a circuit diagram of the analog-to-digital converter shown in FIG. 17. [Figure 28] FIG. 27 is a circuit diagram of a comparator 2701 in the analog-to-digital converter shown in FIG. [Figure 29] FIG. 1 is a block diagram of a 3D magnetic field generator that generates an oscillating magnetic field gradient, according to one embodiment. [Figure 30] FIG. 30 is a schematic top view of the first electromagnetic coil set shown in FIG. 29, according to one embodiment. [Figure 31] FIG. 30 is a schematic top view of the second electromagnetic coil set shown in FIG. 29, according to one embodiment. [Figure 32] FIG. 30 is a schematic top view of the third electromagnetic coil set shown in FIG. 29, according to one embodiment. [Figure 33] 10 is a graph illustrating an example of the total peak magnetic field gradient produced simultaneously by the first and third electromagnetic coil sets. [Figure 34] 10 is a graph illustrating an example of the total peak magnetic field gradient produced simultaneously by the second and third electromagnetic coil sets. [Figure 35] 10 is a graph illustrating an example of a monotonically varying total peak magnetic field generated by the third electromagnet coil set. [Figure 36] FIG. 10 shows an example of an oscillating magnetic field gradient and peak value for the total peak magnetic field gradient in the Z direction. [Figure 37] 37A and 37B are diagrams illustrating the logic blocks and digital sine wave signals for generating the reset (RST) signal in FIGS. 24A and 24B. [Figure 38] 10 is a flowchart of an example algorithm for determining 3D position coordinates corresponding to measurements of total peak magnetic field values ​​of a 3D magnetic field sensor. [Figure 39] FIG. 10 is a block diagram of a 3D magnetic field sensor according to another embodiment. [Figure 40] Figure 40A is a top view of a 3D magnetic field sensor mounted on a catheter, and Figure 40B is a top view of a 3D magnetic field sensor mounted on a guidewire within a sheath or cannula. [Figure 41]FIG. 1 is a top view of a 3D magnetic field sensor attached to an anatomical feature such as an organ of a human or other mammal. [Figure 42] 1 is a flowchart of a method for 3D localization of an object using an oscillating magnetic field gradient, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Detailed Description A three-dimensional (3D) magnetic sensor is implemented on a monolithic semiconductor chip and operates with high sensitivity and ultra-low power. The sensor includes three orthogonal metal coils that generate respective voltage signals by electromagnetic induction in response to an oscillating magnetic field gradient. These voltage signals are processed by on-chip circuitry to determine the peak voltages and relative position of the 3D magnetic sensor, which correspond to the magnitude of the oscillating magnetic field gradient generated by an AC current.

[0021] Our 3D magnetic sensor can be fully CMOS-compatible, e.g., in 65-nm CMOS or other process nodes, and achieves high sensitivity with only a microwatt-level power budget. Three orthogonal metal coils generate an induced electromotive force (EMF) in response to magnetic flux oscillating along the axis of each coil. The three orthogonal metal coils can be implemented using metal stacks available in standard CMOS processes. By integrating the 3D coils and the entire processing circuitry on a monolithic CMOS chip, we can significantly reduce the sensor footprint and enhance sensitivity. Furthermore, the microwatt-level power required by our sensor can be delivered wirelessly and harvested locally from biological fluids. Such highly miniaturized, ultralow-power, and wireless magnetic sensors are highly beneficial for several applications, especially bioelectronics.

[0022] The on-chip circuitry may include amplifiers, filters, peak detectors, and / or analog-to-digital (A / D) converters. In one implementation, the magnetic sensor can perform low-noise amplification, filtering, peak detection, and 12-bit digitization while consuming only 14.8 μW and producing μT (tesla)-level sensitivity, which corresponds to 3D position measurements with an average accuracy of approximately 500 μm.

[0023] 1 is a block diagram of a system 10 for 3D position measurement using AC-generated oscillating magnetic field gradients, according to one embodiment. The system 10 includes a 3D magnetic field generator 100 and a 3D magnetic field sensor 110.

[0024] The 3D magnetic field generator 100 is configured to generate oscillating magnetic field gradients along or parallel to multiple orthogonal axes. The 3D magnetic field generator 100 uses AC power to generate oscillating (e.g., sinusoidal) magnetic field gradients.

[0025] The 3D magnetic field generator 100 sequentially generates a first position-measuring oscillating magnetic field gradient along or parallel to a first axis, a second position-measuring oscillating magnetic field gradient along or parallel to a second axis, and a third position-measuring oscillating magnetic field gradient along or parallel to a third axis. The first, second, and third axes are mutually orthogonal. In a Cartesian coordinate system, the first axis can correspond to the "X" axis, the second axis can correspond to the "Y" axis, and the third axis can correspond to the "Z" axis. At least a portion and / or a majority of each oscillating magnetic field gradient can have a peak magnitude that varies monotonically along the respective axis to uniquely encode the relative position of the 3D magnetic field sensor 110 with respect to the 3D magnetic field generator 100. In some embodiments, the magnitude of each position-measuring oscillating magnetic field gradient can vary linearly or nonlinearly across part or all of the respective oscillating magnetic field gradient.

[0026] The 3D magnetic field sensor 110 is monolithically formed on a semiconductor chip 120. The 3D magnetic field sensor 110 includes three conductive coils 112A-C (collectively, conductive coils 112) and a processing circuit 114. The conductive coils 112 are oriented orthogonal to one another and generate an induced electromotive force (EMF) in response to a magnetic flux oscillating along the respective axis of each conductive coil 112. The induced EMF drives an AC current through the processing circuit 114, and the peak magnitude of the AC current is detected for each conductive coil 112. The peak magnitude of the AC current for each conductive coil 112 corresponds to the peak magnitude of the induced EMF in the respective conductive coil and corresponds to the peak magnitude of the oscillating magnetic field gradient at the location of the 3D magnetic field sensor 110. The peak magnitude of each oscillating magnetic field gradient can be used to determine the 3D position of the 3D magnetic field sensor 110 relative to the 3D magnetic field generator 100. The peak magnitude of the induced EMF in each conductive coil 112 for each oscillating magnetic field gradient can be used to determine the orientation angle of the 3D magnetic field sensor 110 relative to the 3D magnetic field generator 100 .

[0027] The 3D magnetic field sensor 110 may further include contact pads and / or other circuitry 130. The circuitry 130 may include wireless communication circuitry that enables the 3D magnetic field sensor to communicate with an external device. The wireless communication circuitry may support one or more local wireless communication protocols or standards, such as Bluetooth, near-field communication (NFC), and / or backscatter. Additionally or alternatively, the wireless communication circuitry may support Wi-Fi and / or cellular communication protocols or standards. The wireless communication circuitry may transmit peak magnetic field measurements from the 3D magnetic field sensor 110 (e.g., from each conductive coil 112).

[0028] 2 is a top view of a 3D magnetic field sensor 110 according to one embodiment. The first conductive coil 112A includes multiple spirals 210A, which are electrically connected in series with one another through wires 220A. The spirals 210A are parallel to a plane defined by the first and third axes 201, 203 and are wound around the second axis 202. The first, second, and third axes 201-203 are orthogonal to one another. The first, second, and third axes 201-203 may alternatively be referred to as the first, second, and third tip axes, respectively. The magnitude of the induced EMF in the first coil 112A corresponds to the component of the magnetic flux of the oscillating magnetic field that is transverse to the first axis 201.

[0029] Second conductive coil 112B includes multiple helices 210B, which are electrically connected to one another in series through wire 220B. Helices 210B are parallel to a plane defined by second and third axes 202, 203 and are wound around first axis 201. The magnitude of the induced EMF in second coil 112B corresponds to the component of the magnetic flux of the oscillating magnetic field that is transverse to second axis 202. In some embodiments, first conductive coil 112A and second conductive coil 112B can be the same, except that second conductive coil 112B is rotated 90 degrees relative to first conductive coil 112A.

[0030] The third conductive coil 112C includes one helix 210C that is parallel to the plane defined by the first and second axes 201, 202 and wound around the third axis 203. The magnitude of the induced EMF in the third coil 112C corresponds to the component of the magnetic flux of the oscillating magnetic field that is transverse to the third axis 203.

[0031] The induced EMF in each conductive coil 112A-C is the product of the effective cross-sectional area of ​​conductive coil 112A-C and the rate of change of the oscillating magnetic field, given by: dB / dt=B0×ω×cos(ωt) (1) where B × sin(ωt) is the oscillating magnetic field at the sensor location. Equation (1) shows that the frequency ω of the oscillating magnetic field can be varied to enhance the signal at the sensor 110. This is an advantage over using a direct current (DC) magnetic field gradient, where the signal at the sensor 110 can only be enhanced by increasing B, which requires a higher current or a greater number of turns in the gradient coil. In contrast, an AC magnetic field gradient offers a more power-efficient method by increasing the frequency of operation while keeping the current (and therefore B) constant. Higher power efficiency is also achieved for the sensor 110 because 3D coil-based sensing requires only μW-level power consumption by the processing circuitry 114, which is orders of magnitude less than the mW-level power consumed by Hall sensors to sense DC gradients.

[0032] To select the excitation frequency ω, Equation (1) indicates that a higher ω value results in a higher EMF signal. The reactive (inductive-capacitive) impedance (jLω) of the gradient coils used in the 3D magnetic field generator 100 also increases with ω, requiring a higher voltage AC power supply for the same current. The gradient coils can be powered at a frequency within the range of about 100 Hz to about 100 kHz, including about 500 Hz, about 1 kHz, about 10 kHz, about 50 kHz, and any value or range between any two of the above values. In other embodiments, the frequency can be higher than about 100 kHz, for example, about 250 kHz or higher. The value of ω should be high enough to avoid electromagnetic interference from the environment, the most common of which is the 50 / 60 Hz component generated by the power grid.

[0033] The induced EMF in each conductive coil 112A-C is an indirect measure of the oscillating magnetic field generated by the external gradient coils and is given by: EMF=dφ / dt=NA×dB / dt (2) where NA is a geometric factor that depends on the sensor and dB / dt is a factor that depends on the AC gradient. For a sinusoidal magnetic field generated by the gradient coils of the 3D magnetic field generator 100: B = B0 × sin(ωt) (3) dB / dt=B0×ω×cos(ωt) (4)

[0034] In the 3D magnetic field generator 100, B0 and ω are used together to enhance the EMF given by equation (2). In the 3D magnetic field sensor 110, the geometric factor of NA is increased to control the amount of induced voltage, where A is the effective cross-sectional area of ​​the coil sensor perpendicular to the magnetic flux of the incoming oscillating magnetic field, and N is the total number of turns of the coil sensor in the direction of the incoming magnetic flux.

[0035] For two coils with a mutual inductance M between them, the induced EMF in one (secondary) coil due to a changing current I in the other (primary) coil is given by: EMF=M×dI / dt (5) M depends on various factors, including (i) the area and number of turns in both the primary and secondary coils; (ii) the distance between the two coils; (iii) the relative orientation of the two coils; and (iv) the medium between the two coils. Therefore, the best way to evaluate M is through electromagnetic simulation, and then verifying the results of the simulation by comparing them with theoretical calculations. For the purpose of calculating M, another equation is utilized: EMF=N×A×dB / dt (6) This equation describes the induced EMF in a secondary coil (e.g., conductive coils 112A, 112B, and / or 112C) as a function of the number of turns (N) of the secondary coil, the cross-sectional area (A) perpendicular to the magnetic flux B, and the rate of change of the magnetic flux. Equating (5) and (6) yields: M = N × A × (dB / dt) / (dI / dt) (7) where I is the current in the primary coil (e.g., one of the coils in the 3D magnetic field generator 100) and B is the oscillating magnetic field at the location of the secondary coil. For a sinusoidal current I, it is given by: I=I0×sin(ω×t) (8)

[0036] The oscillating magnetic field B at the location of the secondary coil is given by: B=B0×sin(ω×t) (9) By substituting I and B from equations (8) and (9), respectively, into equation (7), we obtain: M = N × A × B0 / I0(10) where I0 is the peak current used to energize the primary coil, and B0 is the peak magnetic field observed at the secondary coil. For simple coil configurations, B0 can be theoretically calculated from I0 using Biot-Savart's law, since both are peak values ​​(and therefore considered DC for calculation purposes). For more complex geometries, such as the gradient coils used in this study, the value of B0 for a given I0 can be found experimentally and / or by Maxwell-based magnetic field simulations. Once the ratio B0 / I0 is found, this value can be inserted into Equation (10) to calculate the mutual inductance M using the secondary coil's geometric parameters N and A. This theoretical value of M can be compared with the value obtained from Maxwell-based magnetic field simulations to provide greater confidence in the effective coupling that will occur between these two coils in the ultimate real-world scenario. For a comprehensive study, the value of M can be evaluated under different environments, such as a silicon chip environment, frequency variations, eddy currents, and the presence of human tissue.

[0037] There are several advantages to using AC (e.g., oscillating) magnetic field gradients instead of DC for position measurement of magnetic field sensing microdevices. First, for a gradient G0 corresponding to a DC current of I0, the same gradient in the AC domain requires a current excitation of I0 sin(ω0t). Power losses due to heating in the coil can be very significant for continuous operation and for DC excitation. (outside 1) JPEG2026505256000002.jpg1613, but for AC excitation (outside 2) JPEG2026505256000003.jpg913.

[0038] Second, for AC gradient-based position measurement systems, the 3D magnetic field sensor is not constrained to employ a Hall effect-based magnetic sensor for high resolution. Instead, a passive coil-based sensor can be used that can sense the induced EMF due to the AC magnetic field generated by the gradient coil. As shown in Equation (11), the position resolution Δx obtained by using a magnetic sensor with a DC gradient G and resolution ΔB can be improved by increasing the value of G, which scales linearly with the DC current (for a given sensor and coil geometry).

[0039] Therefore, a lower Δx implies a higher G, and a higher G requires a higher I. On the other hand, while using an AC gradient, the induced EMF is given by:

[0040] EMF=dφ / dt=NA×dB / dt (12) where NA is a geometric factor that depends on the sensor, and dB / dt is a factor that depends on the AC gradient. For a sinusoidal magnetic field generated by a gradient coil:

[0041] B = B0 × sin(ωt) (13)

[0042] dB / dt=B0×ω×cos(ωt) (14)

[0043] As can be seen from equation (14), dB / dt not only depends on B0, but also on the frequency component ω, which is the peak magnetic field value that depends on the peak current in the coil. Therefore, we now have an additional knob of frequency ω to increase the sensitivity of the sensor, thus reducing ΔB in equation (11). This improves Δx without having to ramp up the current to produce a higher G. If the current I in the gradient coil remains the same while the frequency is changed, then I 2 R thermal losses also remain the same and increasing the current linearly increases the I 2 Unlike DC gradients which cause a quadratic increase in R losses, this results in a more power efficient system.

[0044] Third, AC gradient-based position measurement sensors can be replaced with passive EMF-sensing inductor coils, which do not consume any active power during the EMF sensing mechanism. EMF processing, as described herein, can easily be achieved within the 2-3 μW power range. The complete end-to-end power of the coil-based sensor and processing circuitry described herein can be <15 μW, significantly less than the milliwatt-level power consumed by the power-hungry Hall sensors used in DC magnetic gradient sensors. Furthermore, the sensitivity of Hall sensors is directly dependent on the current used in the Hall element, implying that higher sensitivity comes at the expense of higher power. However, for passive coil-based sensors, sensitivity can be enhanced by either using a higher frequency on the gradient coil side or a higher geometric factor on the sensor side. As previously mentioned, higher frequencies do not result in greater power dissipation in the gradient coils. Therefore, AC gradient-based position measurement systems are more power-efficient from both the gradient coil side and the sensor side.

[0045] AC gradient-based systems are more robust to DC offsets, ambient geomagnetic fields, and avoid problems with low frequency noise.

[0046] FIG. 3 is a cross-section of spiral 210A in first conductive coil 112A taken along plane 30 in FIG. 2 , according to one embodiment. Spiral 210A includes multiple metal layers 300 and multiple insulating layers 310 disposed on a semiconductor substrate 320. Semiconductor substrate 320 can include or be silicon, silicon dioxide, aluminum oxide, sapphire, germanium, gallium arsenide, silicon germanium, indium phosphide, or other semiconductor materials. Active elements for transistors, such as source 321 and drain 322, can be defined on or within semiconductor substrate 320. These active elements can be located within a portion of semiconductor substrate 320 directly below spiral 210A and / or within other portions of semiconductor substrate 320. For example, these active elements can be located within a portion of semiconductor substrate 320 that corresponds to processing circuitry 114 ( FIGS. 1 and 2 ).

[0047] In the illustrated example, metal layer 300 includes metal levels M1-M10. In other embodiments, additional or fewer metal layers 300 may be included. Note that the numbering used herein is relative and does not necessarily correspond to the metal level numbers within semiconductor chip 120. In some embodiments, one or more metal levels may exist between first metal level M1 and semiconductor substrate 320 to, for example, form electrical connections to active devices within the portion of semiconductor substrate 320 immediately below spiral 210A (e.g., below metal level M1). In other embodiments, first metal level M1 may be the first metal level within semiconductor chip 120. Using more metal layers increases the induced EMF of first conductive coil 112A.

[0048] Insulating layers 310 are disposed between adjacent metal layers 300 (e.g., between metal levels M1 and M2). Each insulating layer provides mechanical support to any layers above it and electrically insulates adjacent metal layers 300 from one another. Insulating material 312 is also disposed in any gaps 313 in the metal layers 300 to electrically insulate any metal wires 302 and / or metal wire segments 304 defined within those metal layers 300. Insulating layers 310 and insulating material 312 may include or consist of a dielectric material, such as silicon dioxide.

[0049] The spiral 210A includes a plurality of interconnected metal loops 330. Each loop 330 includes a pair 340 of metal wires 302, an intra-loop metal column 342, and an inter-loop metal column 344. The intra-loop metal column 342 includes one or more metal vias 332 and one or more metal segments 304 of either metal layer 300 between the pair 340 of metal wires 302. The metal vias 332 and any metal segments 304 are electrically connected to each other and to the pair 340 of metal wires 330, thereby electrically connecting the pair 340 of metal wires 330 through the intra-loop metal column 342. The inter-loop metal column 344 includes one or more metal vias 332 and one or more metal segments 304 of either metal layer 300 between the first metal wire 302 of one pair 340 and the second metal wire 302 of the other pair 340. The metal vias 322 are defined in the insulating layer 310.

[0050] The first pair 340A of metal wires 302 includes metal wires 302 formed between the M1 and M10 layers. The second pair 340B of metal wires 302 includes metal wires 302 formed between the M2 and M9 layers. The third pair 340C of metal wires 302 includes metal wires 302 formed between the M3 and M8 layers. The fourth pair 340D of metal wires 302 includes metal wires 302 formed between the M4 and M7 layers. The fifth pair 340E of metal wires 302 includes metal wires 302 formed between the M5 and M6 layers. The first pair 340A is the outermost pair, and the second pair 340B is the next outermost pair. The fifth pair 340E is the innermost pair (furthest from the outside).

[0051] The second pair 340B is disposed between the first pair 340A. The third pair 340C is disposed between the second pair 340B and the first pair 340A. The fourth pair 340D is disposed between the third pair 340C, the second pair 340B, and the first pair 340A. The fifth pair 340E is disposed between the fourth pair 340D, the third pair 340C, the second pair 340B, and the first pair 340A. The first pair 340A is the outermost pair, and the fifth pair 340E is the innermost pair.

[0052] The first intra-loop metal column 342A electrically connects the first pair 340A of metal wires 302 within the first loop 330. The first intra-loop metal column 342A includes metal vias 332 in via levels V1-V9 and metal segments 304 in metal levels M2-M9. The first inter-loop metal column 344A electrically connects the metal wire 302 in metal level M10 within the first pair 340A to the metal wire 302 in metal level M2 within the third pair 340B, electrically coupling the first and second loops 330.

[0053] The second intra-loop metal column 342B electrically connects the second pair 340B of metal wires 302 within the second loop 330. The second intra-loop metal column 342B includes metal vias 332 in via levels V2-V8 and metal segments 304 in metal levels M3-M8. The second inter-loop metal column 344B electrically connects the metal wire 302 in metal level M9 in the second pair 340B to the metal wire 302 in metal level M3 in the third pair 340C, electrically coupling the second and third loops 330.

[0054] The third intra-loop metal column 342C electrically connects the third pair 340C of metal wires 302 within the third loop 330. The third intra-loop metal column 342C includes metal vias 332 in via levels V3-V8 and metal segments 304 in metal levels M4-M7. The third inter-loop metal column 344C electrically connects the metal wire 302 in metal level M8 in the third pair 340C to the metal wire 302 in metal level M4 in the fourth pair 340D, electrically coupling the third and fourth loops 330.

[0055] The fourth intra-loop metal column 342D electrically connects the fourth pair 340D of metal wires 302 within the fourth loop 330. The fourth intra-loop metal column 342D includes metal vias 332 in via levels V4-V6 and metal segments 304 in metal levels M5 and M6. The fourth inter-loop metal column 344D electrically connects the metal wire 302 in metal level M7 within the fourth pair 340D to the metal wire 302 in metal level M5 within the fifth pair 340E, electrically coupling the fourth and fifth loops 330.

[0056] The fifth intra-loop metal column 342E electrically connects the fifth pair 340E of metal wires 302. The fifth intra-loop metal column 342E includes metal vias 332 in via level V5.

[0057] The metal wires 302 have respective lengths, respective widths, and respective heights. The respective lengths of the metal wires 302 can be measured relative to a first axis 351, which can be parallel to the first axis 201 (FIG. 2). The respective widths of the metal wires 302 can be measured relative to a second axis 352, which can be perpendicular to the first axis 351 and parallel to the second axis 202 (FIG. 2). The respective heights of the metal wires 302 can be measured relative to a third axis 353, which can be perpendicular to the first and second axes 351, 352 and parallel to the third axis 203 (FIG. 2). The respective lengths of the metal wires 302 are greater (e.g., significantly greater) than their respective heights, increasing the magnetic field of the cross section. The ratio of the respective lengths to the respective heights of the metal wires 302 can be in a range of 500:1 to approximately 10,000:1, including any value or range therebetween. The width and height of each metal wire can be the same or approximately the same, and thus the ratio of the respective length to the respective width of a given metal wire 302 can be the same or approximately the same as the ratio of the respective length to the respective height of each metal wire 302 for that metal wire.

[0058] Spiral 210A and coil 330 are wound around axis 360, which is parallel to second axis 352. Because the thickness (e.g., height) of metal layer 300 and insulating layer 310 generally increases with distance from semiconductor substrate 320 (e.g., metal level M10 is thicker than metal level M1), the position of axis 360 is offset and is closer to metal level M1 than to metal level M10. Spiral 210A is generally flat and lies within or parallel to the plane defined by first and third axes 351, 353. In FIG. 3, spiral 210A is wound in a counterclockwise direction relative to axis 360. In other embodiments, spiral 210A is wound in a clockwise direction relative to axis 360, as shown in FIG. 4.

[0059] Two terminals are present at opposite ends of the first helix 210A. The first terminal 361 is disposed on (e.g., electrically connected to) a metal wire 302 formed in the M1 metal layer. The first terminal 361 and the first intra-loop metal column 342A can be disposed on (e.g., electrically connected to) opposite ends of the metal wire 302 formed in the M1 metal layer. The second terminal 362 is disposed on (e.g., electrically connected to) a metal wire 302 formed in the M6 ​​metal layer. The second terminal 362 and the fifth intra-loop metal column 342E can be disposed on (e.g., electrically connected to) opposite ends of the metal wire 302 formed in the M6 ​​metal layer.

[0060] Adjacent spirals 210A within the first conductive coil 112A are electrically coupled to each other through first and second terminals 361, 362 and wires 220A (e.g., in a cascade connection), which can increase the effective coupling area of ​​the first conductive coil 112A. The first terminal 361 of one spiral 210A is electrically connected to the second terminal 362 of the adjacent spiral 210A through one or more wires 220A. Similarly, the second terminal 362 of one spiral 210A is electrically connected to the first terminal 361 of the adjacent spiral 210A through one or more wires 220A. The terminals 361, 362 at opposite ends of the first conductive coil 112A can be electrically coupled to the processing circuit 114.

[0061] In other embodiments, first terminal 361 is disposed on (e.g., electrically connected to) metal wire 302 formed in the M10 metal layer, as shown, for example, in Figures 5 and 6. In Figure 5, spiral 210A is wound in a counterclockwise direction about axis 360. In Figure 6, spiral 210A is wound in a clockwise direction about axis 360.

[0062] The total length of coil 112A, measured relative to second axis 202, is significantly greater than the height of helix 210A (e.g., coil-metal stack) measured relative to third axis 203, 353, increasing the effective cross-sectional area of ​​coil 112A and increasing the induced EMF. For example, the ratio of the total length of coil 112A to the height of helix 210A can be from about 50:1 to about 250:1, including about 100:1, about 150:1, about 200:1, and any value or range between any two of the above ratios. In some embodiments, the length of coil 112A can be equal to or approximately equal to one of the dimensions (e.g., width or length) of semiconductor chip 120.

[0063] As explained above, second conductive coil 112B can be the same as first conductive coil 112A, but second conductive coil 112B is rotated 90 degrees relative to first conductive coil 112A. Thus, helix 210B in second conductive coil 112B can be the same as helix 210A in first conductive coil 112A, but helix 210B is rotated 90 degrees relative to helix 210A.

[0064] Figure 7 is a cross-section of helix 210B in second conductive coil 112B taken through plane 32 in Figure 2, according to one embodiment. In this embodiment, helix 210B is the same as helix 210A in the embodiment shown in Figure 3, except that helix 210B is rotated 90 degrees relative to helix 210A.

[0065] Thus, the respective lengths of each metal wire 302 in the spiral 210B can be measured relative to the second axis 352. The respective widths of each metal wire 302 in the spiral 210B can be measured relative to the first axis 351. The respective heights of each metal wire 302 in the spiral 210B can be measured relative to the third axis 353. The respective lengths of each metal wire 302 in the spiral 210B are greater (e.g., significantly greater) than their respective heights. The ratio of the respective length to the respective height of each metal wire 302 can be in the range of about 50 to about 250, including about 100, about 150, about 200, and any value or range between any two of the above values. The width and height of each metal wire can be the same or approximately the same. Thus, the ratio of the respective length to the respective width of a given metal wire 302 can be the same or approximately the same as the ratio of the respective length to the respective height of each metal wire 302 for that metal wire.

[0066] Spiral 210B and coil 330 are wound around axis 760, which is parallel to first axis 351 and perpendicular to axis 360. Because the thickness (e.g., height) of metal layer 300 and insulating layer 310 generally increases with distance from semiconductor substrate 320 (e.g., metal level M10 is thicker than metal level M1), the position of axis 360 is offset and located closer to metal level M1 than to metal level M10. Spiral 210B is generally flat and lies within or parallel to the plane defined by second and third axes 352, 353.

[0067] In Figure 7, spiral 210B is wound in a counterclockwise direction about axis 760. In another embodiment, spiral 210B is wound in a clockwise direction about axis 760, as shown in Figure 8.

[0068] Two terminals are present at opposite ends of the second helix 210B. The first terminal 761 is disposed on (e.g., electrically connected to) the metal wire 302 formed in the M1 metal layer. The first terminal 761 and the first intra-loop metal column 342A can be disposed on (e.g., electrically connected to) opposite ends of the metal wire 302 formed in the M1 metal layer. The second terminal 762 is disposed on (e.g., electrically connected to) the metal wire 302 formed in the M6 ​​metal layer. The second terminal 762 and the fifth intra-loop metal column 742E can be disposed on (e.g., electrically connected to) opposite ends of the metal wire 302 formed in the M6 ​​metal layer.

[0069] Adjacent spirals 210B within the second conductive coil 112B are electrically coupled through first and second terminals 761, 762 and wires 220B. The first terminal 761 of one spiral 210B is electrically connected to the second terminal of the adjacent spiral 210B through one or more wires 220B. Similarly, the second terminal 762 of one spiral 210B is electrically connected to the first terminal 761 of the adjacent spiral 210B through one or more wires 220B. The terminals 761, 762 at opposite ends of the second conductive coil 112B can be electrically coupled to the processing circuit 114.

[0070] In other embodiments, terminal 761 is disposed on (e.g., electrically connected to) metal wire 302 formed within the M10 metal level, as shown, for example, in Figures 9 and 10. In Figure 9, spiral 210B is wound in a counterclockwise direction about axis 760. In Figure 10, spiral 210B is wound in a clockwise direction about axis 760.

[0071] 11 is a top view of the third conductive coil 112C shown in FIG. 2 in isolation. The spiral 210C is formed from metal wire within one or more metal levels of the semiconductor chip 120. The third conductive coil 112C includes two terminals 1101, 1102 at opposite ends of the spiral 210C. The terminals 1101, 1102 can be electrically coupled to the processing circuit 114. The spiral 210C is generally planar and lies within or parallel to a plane defined by the first and second axes 351, 352.

[0072] Spiral 210C has a plurality of interconnected loops 1100 wound around an axis 1160 parallel to third axis 203. The windings are closely spaced to increase the density of spiral 210C. Spiral 210C is wound in a clockwise direction about axis 1160. In other embodiments, spiral 210C is wound in a counterclockwise direction about axis 1160, as shown, for example, in FIG. 12 .

[0073] A large number of turns in helix 210C and / or a large cross-sectional area of ​​helix 210C can be achieved by using multiple (e.g., some or all) metal layers to form helix 210C, increasing the EMF induced by third conductive coil 112C.

[0074] A large number of turns in helix 210C and / or a large cross-sectional area of ​​helix 210C can be achieved by using multiple (e.g., some or all) metal layers to form helix 210C, increasing the EMF induced by third conductive coil 112C.

[0075] Spiral 210C includes multiple wires 1302 formed in multiple metal levels M1-M10. The wires 1302 are stacked and aligned vertically. Wires 1302 in adjacent metal levels are electrically connected by one or more conductive vias 332 formed in their respective insulating layers 310.

[0076] In some embodiments, via 332 and wire 1302 can have the same or approximately the same length to maximize the cross-sectional area of ​​helix 210C and conductive coil 112C, as shown, for example, in FIG. 14. In FIG. 14, via 332 and wire 1302 have the same length, as measured relative to first axis 201. FIG. 15 is a cross-section of helix 210C within third conductive coil 112C, taken along plane 1500 in FIG. 11, according to one embodiment, where via 332 and wire 1302 have the same width, as measured relative to second axis 202. Thus, via 332 and wire 1302 can combine to form interconnected metal loop 1100, which can form an uninterrupted and / or continuous metal structure relative to third axis 203 along the entire length of helix 210C. FIG. 16 is a cross section of helix 210C taken through plane 1500 in FIG. 11 according to the embodiment shown in FIG.

[0077] For the helical third conductive coil 112C shown in FIGS. 11 and 12, the equivalent definition of Z and NA in equation (6) is modified to: NA = A1 + A2 + An (15) where A1 represents the area of ​​the outermost loop 1100, A2 represents the area of ​​the second loop 110, etc. As is evident from equation (15), a multi-turn spiral coil generates a correspondingly large EMF. To achieve this, the third conductive coil 112C can be designed with minimum width and spacing requirements set by design rule check (DRC) to achieve the maximum number of turns per given area. To achieve a further increase in effective area, identical coils can be implemented in some or all metal layers, such as M1 at the bottom to M10 at the top, and all stacked together to form a single spiral spanning some or all of the available metal layers.

[0078] FIG. 17 is a block diagram of an equivalent circuit formed in the semiconductor chip 120 of the 3D magnetic field sensor 110. As shown in FIG.

[0079] The circuit includes an instrumentation amplifier (IA) 1700, a band-pass filter (BPF) 1702, a programmable gain amplifier (PGA) 1703, a peak detect and hold (PDH) circuit 1704, an analog-to-digital converter 1705, and a serializer 1706. An input terminal of the IA 1701 is electrically coupled to a conductive coil 112 (e.g., conductive coil 112A or 112B). An output terminal of the IA 1701 is electrically coupled to an input terminal of the BPF 1702. An output terminal of the BPF 1702 is electrically coupled to an input terminal of the PGA 1703. An output terminal of the PGA 1703 is electrically coupled to an input terminal of the PDH circuit 1704. An output terminal of the PDH circuit 1704 is electrically coupled to an input terminal of the ADC 1705. The output terminal of the ADC is electrically coupled to the input terminal of the serializer 1706 .

[0080] Each conductive coil 112 has a parasitic resistance R Coil Inductor L Coil The oscillating (e.g., AC) magnetic field gradient generated by the 3D magnetic field generator 100 (FIG. 1) is expressed as a corresponding oscillating voltage V EMF The EMF with inductor L Coil Lead inward.

[0081] Parasitic resistance R Coil is the unit (Outside 3) JPEG2026505256000004.jpg1813 with broadband noise (outside 4) JPEG2026505256000005.jpg2139, where k is the Boltzmann constant and T is the temperature in Kelvin. Sense broadband noise (outside 5) Reduce to JPEG2026505256000006.jpg1639. C Sense R cannot be made arbitrarily large for noise suppression because the low-pass frequency of the RC (resistor-capacitor) should be higher than the frequency of the EMF signal, from about 100 Hz to about 100 kHz, including about 500 Hz. Coil can be about 1 Mohm to about 10 Mohm for each conductive coil 112 (e.g., for the first conductive coil 112A (e.g., the X magnetic sensor), for the second conductive coil 112B (e.g., the Y magnetic sensor), and for the third conductive coil 112C (e.g., the Z magnetic sensor)), and can be about 2 Mohm, about 6 Mohm, about 8 Mohm, and any value or range between any two of the above values. Coil can be the same or different for each conductive coil 112. In one example, R Coil is 8 MΩ for first and second conductive coils 112A, B and 5.4 MΩ for third conductive coil 112C, (outside 6) There is a thermal noise floor of JPEG2026505256000007.jpg1539, and for the third conductive coil 112C, (outside 7) There is a thermal noise floor of JPEG2026505256000008.jpg1539.

[0082] To provide a magnetic field resolution of ≦10 μT for each axis of the 3D magnetic field sensor, a simulation was performed with an oscillating magnetic field of 10 μT for conductive coils 112A-C to determine an acceptable noise floor for the front-end circuit block. In response to a 10 μT magnetic field, first and second conductive coils 112A,B generated an EMF of 660 nV, while the Z sensor generated an EMF of 40 μV. Because the EMFs of first and second conductive coils 112A,B are close to their respective thermal noise floors, front-end instrumentation amplifier (IA) 1701 provides a lower input referred noise (IRN) floor, i.e., about 5 to 10 times lower, including any subrange. (outside 8) JPEG2026505256000009.jpg1339, which is described in more detail below.

[0083] The IA1701 is capacitively coupled to the input, as shown in Figure 18, which is a circuit diagram of the IA1701. The IA1701 can be implemented in a fully differential closed-loop architecture to achieve high common-mode noise rejection and ensure sufficient linearity. The input coupling capacitor C1 can be X × C2, where X can be approximately 10 to approximately 100, including approximately 50, approximately 75, and any value or range between any two of these values. The value of X can be determined based on the desired gain, total capacitance value, area limitations, and / or other factors. In one example, C2 can be an approximately 230 fF (femtofarad) metal-oxide-metal (MOM) capacitor to produce an overall closed-loop gain of 50 V / V (output voltage to input voltage ratio of 50). This gain is not kept very high to avoid amplifying input noise. A pseudo resistor 1800 implemented using a transistor can be added in the feedback loop of the IA1701 to provide a GΩ (gigaohm) level impedance, which can be used to set the high-pass corner frequency to be in the range of about 10 to about 100 Hz, including any subrange. The low-pass corner frequency of the IA1701 is G m1 The output impedance and load capacitor C of block 1810 L It is determined by C L can be approximately 25 pF (picofarads). L The value of can be determined based on the desired gain, total capacitance value, area limitations, and / or other factors.

[0084] G m1 Block 1810 can be implemented as a cascade of two current recycling stages, as shown in Figure 19. Since M3 and M5 (and M4 and M6) both carry the same current, IRN of the first stage is given by:

number

[0085] For the IA1701, the relatively low gain is subsequently compensated for after the sensitive EMF signal has been filtered by the bandpass filter following the IA. A pseudo resistor is used in the IA1701 to simulate a non-feedback node P + and P - V to ref biased, V refcan be Vdd / 2. N + Node and P + Node and (similarly N - Node and P - By separating the biases applied at nodes V and V, it is possible to bias these two independently and apply the same input signal V in+ (and similarly V in- ) can be used to drive both PMOS (p-channel metal oxide semiconductor) and NMOS (n-channel MOS) transistors. The common-mode voltage at the output of each stage of the IA1701 is G m2 V (selected as Vdd / 2) ref It can be set to G m2 is the V used to bias the non-feedback path ref The differential output of the PGA 1703 can also be centered around a common mode voltage of Vdd=600 mV on the semiconductor chip 120.

[0086] Due to the stringent noise requirements of first and second conductive coils 112A, B compared to third conductive coil 112C, IA 1701 may be used at the front end of first and second conductive coils 112A, 112B, with third conductive coil 112C connected directly to bandpass filter (BPF) 1702 ( FIG. 17 ). In other words, the equivalent circuit for first and second conductive coils 112A, B includes IA 1701, which has an input terminal electrically coupled to first conductive coil 112A (in the equivalent circuit for first conductive coil 112A) or has an input terminal electrically coupled to second conductive coil 112B (in the equivalent circuit for second conductive coil 112B). In the equivalent circuit for first and second conductive coils 112A, B, the output terminal of IA 1701 is electrically coupled to the input terminal of BPF 1702. In the equivalent circuit for third conductive coil 112C, the output terminal of IA 1701 is electrically coupled to the input terminal of BPF 1702, as shown in FIG.

[0087] FIG. 22 is a circuit diagram of BPF 1702 according to one embodiment. BPF 1702 is configured to filter out excess out-of-band noise to improve the signal-to-noise ratio (SNR). BPF 1702 is implemented as a capacitively coupled, fully differential, and closed-loop architecture. BPF 1702 can be implemented with other architectures, as will be understood by those skilled in the art. To achieve a sharp BPF response, the low-pass corner frequency should be lower than the high-pass corner frequency, causing the intersection of the two responses within their respective steep slope regions to produce sharp respective filter responses. A minor drawback of this is a gain of less than unity at the output, which can be approximately 0.4 V / V at a center frequency of 500 Hz, which is not a problem since the gain can be compensated for by the programmable gain amplifier (PGA) 1703 (FIGS. 17 and 21) in the subsequent block. The G of BPF 1702 is m1 Stage 2100 is IA1701 G m1 This can be implemented in the same manner as block 1810. Therefore, G in FIG. m1 The circuit diagram for block 1810 is G m1 The circuit diagram of the stage 2100 can also be shown. m1 The output impedance of the output stage (the gate terminal of M8 in Figure 19) is connected to the on-chip reference current I ref The filter is controlled externally by an adjustable DC voltage rather than by the filter resistor (Figure 19). This can allow the filter response to be adjusted after fabrication, especially since the transistors operate in the subthreshold regime, which is more susceptible to process variations. Examples of passive component values ​​used in the BPF are C a =1pF, C b =15pF, C c =1pF, C d =1pF, C e =106pF, R a = 10.4 kΩ, and R b= 105.5 kΩ. Other values ​​can be used in other embodiments. Resistor R a and R b are not realized as pseudo resistors because they are more prone to process variations, which is undesirable for a BPF. ref is selected as Vdd / 2, which may be in the range of about 500 mV to about 800 mV, including about 600 mV, about 700 mV, and any value or range between any two of the foregoing values.

[0088] The output terminal of BPF 1702 is electrically coupled to the input terminal of PGA 1703 as shown in Figures 17 and 21. In other embodiments, PGA 1703 can be implemented as another amplifier. The function of the PGA is to amplify the EMF signal sufficiently for processing by analog-to-digital converter (ADC) 1705 (Figures 17 and 21).

[0089] The PGA1703 can be implemented as a capacitively coupled fully differential architecture, but its N + Node and P + Node, and N - Node and P - The nodes are grouped together as shown in Figure 23 and are distinct from the IA1701 and BPF1702. At the input terminal of the PGA1703, a 3-bit adjustable capacitive network 2310 is implemented to control the gain of the PGA1703 from 40V / V to 280V / V in steps of 40V / V. This adjustability corresponds to the range of the varying EMF signal due to the varying peak magnetic field magnitude generated by the gradient coils across the field of view (FOV) of the 3D magnetic field generator 100. A feedback capacitor C g The feedback capacitor C can be approximately 44.6 fF or some other value. g The value of can be determined based on the required gain, total capacitance value, area limitations, and / or other factors. Switches S1-S3 can be implemented using pass-transistor logic circuits and driven using inverter-based drivers.

[0090] PGA1703G m1 Stage 2300 is IA1701 G m1 This can be implemented in the same manner as block 1810. Therefore, G in FIG. m1 The circuit diagram of the block is also m1 23 can be a circuit diagram of stage 2300.

[0091] The differential output of the PGA1703 measured with a typical mV level input is approximately 1 V. pp The total integrated noise at the output of the PGA is approximately 8 mV for the first and second conductive coils 112A, B. rms (root-mean squared) (effective value of about 8 mV), and for third conductive coil 112C, about 1 mV rms and these values ​​are approximately 64 μT rms and 8μT rms In other embodiments, the magnetic field resolution per conductive coil 112 is approximately 1 μT. rms ~approx. 100μT rms can be in the range of about 25 μT rms , about 50μT rms , about 75T rms , and any range of values ​​between any of the above values. This resolution can be further improved by averaging several consecutive samples, as described herein.

[0092] The output terminal of PGA 1703 is electrically coupled to the input terminal of peak detect and hold (PDH) circuit 1704, as shown in FIGS.

[0093] As previously mentioned, the peak magnitude of the sinusoidal magnetic field at any given point of interest in the FOV is the only signal of interest for position decoding purposes. This relaxes the constraints on the ADC, which can be configured to digitize only the peak values ​​and not operate in continuous mode, significantly reducing power. To extract the peak magnitude from the differential output of the PGA 1703, a positive differential PDH circuit 2401 is implemented for positive peak extraction, as shown in FIG. 24A. In addition, a negative differential PDH circuit 2402 is implemented for negative peak detection, as shown in FIG. 24B. The positive and negative differential PDH circuits 2401, 2402 operate in three modes: peak detect, peak hold, and reset.

[0094] For the positive PDH circuit 2401, V in+ As G increases m3 decreases, causing an increase in the current in the current mirror pair, which increases V until a positive peak is detected. out+ Increase V in+ When V begins to decrease, out+ cannot be tracked because the holding capacitor C p This is because the capacitor (e.g., 15 pF) cannot discharge from the current mirror transistor above it, thus holding the previous peak value. p After digitizing the peak values ​​stored above, V out+ The reset transistor (RST) at p immediately discharges for the next cycle. A similar operation occurs for the negative peak extraction in the negative PDH circuit 2402.

[0095] Each G of the positive and negative differential PDH circuits 2401 and 2402 m3Stage 2410 can be implemented as shown in the circuit diagram of FIG. 25. To digitize the output of PDH circuit 1704, ADC 1705 can generate a sampling clock synchronized with the peak of the EMF signal, as shown in FIG. 26A. The power consumption of PDH circuit 1704 can be approximately 1 μW, e.g., approximately 1.14 μW. The sampling clock needs to be high for the duration of the peak hold time, which extends from the peak of the sine wave to the crossing of the common mode (600 mV), as shown in FIG. 26B. This is achieved by converting the sine wave signal to a rail-to-rail (upper power supply voltage - lower power supply voltage) digital voltage using a comparator, with the other input terminal of the comparator connected to 600 mV. A cosine waveform is generated by differentiating the sine wave signal, and the cosine waveform is also converted to a rail-to-rail digital voltage. An XOR (exclusive or) operation on these two digital signals is used to obtain the sampling clock shown in FIG. 26A. The reset (RST) signal in Figures 24A and 24B is also obtained using a digital sine wave signal and associated logic block 3700, as shown in Figures 37A and 37B.

[0096] The differential output of the PDH circuit 1704 is fed to a 12-bit differential-input successive approximation register (SAR)-based ADC 1705. In other embodiments, the ADC 1705 can have a different number of bits and / or a different implementation. An example circuit diagram of the ADC 1705 is shown in FIG. 27. SAR ADCs are highly power-efficient at the relatively low sampling rates (e.g., about 20 kS / s (kilosamples per second)) used for the 3D magnetic field sensor 110. As shown in FIG. 27, power and area requirements are further reduced by employing a simple capacitor switching procedure (e.g., a step-down switching procedure). Additionally, discharging through an NMOS transistor is faster than discharging through a PMOS transistor. The ADC 1705 includes four main blocks: a comparator 2701, a capacitive digital-to-analog converter (DAC) 2702, a SAR logic block 2703, and a bootstrap switch 2704. The input is first sampled onto the upper plate of the capacitor through the bootstrap switch 2704, while the lower plate is connected to V refP (1.2V). When the bootstrap switch 2704 is turned off, the comparator 2701 performs a first comparison without switching any capacitors. If the output of the comparator is high (most significant bit (MSB)=1), the higher voltage (V in+ ) side capacitor C1 is V refN (0V), and the lower voltage (V in- ) remains uncharged. If MSB=0, the opposite scenario occurs. This process is repeated until the least significant bit (LSB) is calculated. Clearly, there is only one capacitor switching per bit calculation, which reduces charge transfer within the DAC and control logic, resulting in significant power savings. The DAC capacitors can be binary weighted, with C i =2×C i+1 and C 11 =C12 =4fF.

[0097] Figure 28 is a circuit diagram of comparator 2701, which includes a preamplifier 2801 followed by a regenerative latch 2802 for optimal operation. The dynamic nature of the comparator ensures that there is no static power consumption. When the ADC clock (CLK) is high, outputs O1 and O2 are reset. When the clock is low, V P and V N and are compared by a preamplifier 2801, and the result is fed to a regenerative latch 2802 to generate the digital output. Low noise and high power efficiency are achieved by using an upper current mirror to bias the preamplifier's input transistors. The SAR logic and DAC control block generate control and clock signals using a 50 kHz external clock. The 12-bit output of the ADC1705 is serialized to generate a single stream of X, Y, and Z sensor data. The ADC can consume a total power of 2.26 μW.

[0098] 29 is a block diagram of a 3D magnetic field generator 100 that generates an oscillating magnetic field gradient, according to one embodiment. The 3D magnetic field generator 100 includes a controller 2901, a first electromagnetic coil set 2910, a second electromagnetic coil set 2920, and a third electromagnetic coil set 2930. The first electromagnetic coil set 2910 is configured to generate a first oscillating magnetic field gradient with respect to a first axis 2921 (e.g., the X-axis in a Cartesian coordinate system). The second electromagnetic coil set 2920 is configured to generate a second oscillating magnetic field gradient with respect to a second axis 2922 (e.g., the Y-axis in a Cartesian coordinate system). The third electromagnetic coil set 2930 is configured to generate a third oscillating magnetic field gradient with respect to a third axis 2923 (e.g., the Z-axis in a Cartesian coordinate system). The first, second, and third axes 2921-2923 may alternatively be referred to as first, second, and third position measurement axes 2921-2923, respectively. Depending on the relative angular orientation and / or rotational orientation of the 3D magnetic field sensor 110 with respect to the 3D magnetic field generator 100, the first, second, and third position measurement axes can be parallel to the first, second, and third tip axes 201-203 or in other directions.

[0099] The electromagnetic coil sets 2910, 2920, 2930 can be stacked together and / or aligned longitudinally along a third axis (e.g., aligned longitudinally relative to an underlying surface). The electromagnetic coil sets 2910, 2920, 2930 are preferably centered (e.g., concentrically centered) and / or aligned relative to the first and second axes. Additionally, the electromagnetic coil sets 2910, 2920, 2930 each have top and bottom planar surfaces (e.g., perpendicular to the Z axis), which allows the coil sets to be stacked and integrated into or embedded within a flat device such as a board, wall, chair back, conformable wearable belt, or other location.

[0100] The controller 2901 is electrically coupled to the first electromagnetic coil set 2910, the second electromagnetic coil set 2920, and the third electromagnetic coil set 2930. The controller 2901 is configured to selectively power the first electromagnetic coil set 2910, the second electromagnetic coil set 2920, and / or the third electromagnetic coil set 2930. Selectively powering the electromagnetic coil sets 2910, 2920, and / or 2930 sequentially generates a total oscillating magnetic field gradient for each axis, at least a portion and / or a majority of each of the total oscillating magnetic field gradients having a peak magnitude that varies monotonically along the respective axis to encode the relative position of the 3D magnetic field sensor 110. For example, the electromagnetic coil sets 2910, 2920, and / or 2930 can be selectively powered such that at least a portion of the total oscillating magnetic field gradient for the first axis has a monotonically varying magnitude. In another example, the electromagnetic coil sets 2910, 2920, and / or 2930 can be selectively energized so that the total oscillating magnetic field gradient relative to the second axis has a monotonically varying magnitude. In yet another example, the electromagnetic coil sets 2910, 2920, and / or 2930 can be selectively energized so that the total oscillating magnetic field gradient relative to the third axis has a monotonically varying magnitude. By measuring the total oscillating magnetic field while generating each position-measuring oscillating magnetic field gradient, the relative position of the magnetic sensor device relative to the electromagnetic coil sets 2910, 2920, and / or 2930 can be determined. The portion of the total oscillating magnetic field gradient that has a monotonically varying magnitude relative to a given axis can be referred to as the field of view (FOV). The total oscillating magnetic field gradient relative to each axis uniquely encodes the relative position of the 3D magnetic field sensor 110 within the FOV of the 3D magnetic field generator 100.

[0101] 30 is a schematic top view of a first electromagnetic coil set 2910 according to one embodiment. The first electromagnetic coil set 2910 includes a clockwise spiral winding 2912 and a counterclockwise spiral winding 2914, which are positioned adjacent or next to each other. The spiral windings 2912, 2914 can be mirror images of each other. Each spiral winding 2912, 2914 has a respective axis of symmetry 3012, 3014, which are parallel to a first axis 2921 (e.g., the X-axis). The axes of symmetry 3012 and 3014 are aligned within the spiral windings 2912, 2914 to generate a uniform or nearly uniform oscillating magnetic field gradient (e.g., a first oscillating magnetic field gradient) relative to the first axis. The spiral windings 2912, 2914 extend along a second axis 2922 (e.g., the Y-axis) to form, for example, an oval, a racetrack (e.g., stadium), a rectangle, a rounded rectangle, or other elongated shape. The spiral windings 2912, 2914 can have an extension along the second axis 2922 of approximately 15 cm, which can keep the first oscillating magnetic field gradient substantially uniform throughout the Y FOV (e.g., the FOV relative to the second axis 2922). The width 2916 of the first electromagnetic coil set 2910 is measured along or parallel to the first axis 2921 (e.g., the X-axis). The length of the first electromagnetic coil set 2910 is measured across or parallel to the second axis 2922.

[0102] The spiral windings 2912, 2914 are formed by respective wires 3022, 3024 (e.g., first and second wires). Alternatively, two or more wires can be connected together to form the spiral windings. The spiral windings 2912, 2914 have a thickness (e.g., outer diameter) determined by the thickness of the respective wires 3022, 3024. The wires 3022, 3024 can be identical and therefore have the same thickness. Thus, the spiral windings 3022, 3024 have upper and lower planes (or surfaces that are approximately planar (e.g., at least 95% flat)), which are parallel to the XY plane 3000 (e.g., the plane defined by the first and second axes 2921, 2922). The upper and lower planes of the spiral windings 2912, 2914 are defined by the upper and lower surfaces of the respective wires 3022, 3024. The thickness of the spiral windings 2912, 2914 about a third axis 2923 (e.g., the Z-axis) is equal to the thickness of the wires 3022, 3024. The wires 3022, 3024 can have a number of windings or turns suitable for generating a first oscillating magnetic field gradient.

[0103] The wires 3022, 3024 can be configured to receive AC current in the range of about 10 A to about 50 A, including about 20 A, about 30 A, and about 40 A, or other currents. For example, the wires 3022, 3024 can be copper wire, such as Litz 50 / 32 AWG (American wire gage) wire, where 50 / 32 AWG wire represents 50 bundles of 32 AWG wire. The wires 3022, 3024 have insulating covers to prevent electrical shorting between each other.

[0104] 31 is a schematic top view of a second electromagnetic wire set 2920, according to one embodiment. The second electromagnetic coil set 2920 includes a clockwise spiral winding 2925 and a counterclockwise spiral winding 2924, which are positioned adjacent to one another. The spiral windings 2924, 2925 can be mirror images of one another. Each spiral winding 2924, 2925 has a respective axis of symmetry 3112, 3114, which are parallel to a second axis 2922 (e.g., the Y-axis). The axes of symmetry 3112 and 3114 are aligned within the spiral windings 2924, 2925 to generate a uniform or nearly uniform oscillating magnetic field gradient (e.g., a second oscillating magnetic field gradient) relative to the second axis. The second electromagnetic coil set 2920 is the same as the first electromagnetic coil set 2910, except that the second electromagnetic coil set 2920 is rotated 90 degrees compared to the first electromagnetic coil set 2910. In other embodiments, the second electromagnetic coil set 2920 can have other configuration differences compared to the first electromagnetic coil set 2910.

[0105] The spiral windings 2925, 2924 are formed by the respective wires 3122, 3124 (e.g., the third and fourth wires). Alternatively, two or more wires can be connected together to form the spiral winding. The spiral windings 2925, 2924 have a thickness (e.g., outer diameter) determined by the thickness of the respective wires 3122, 3124. The wires 3122, 3124 can be identical and therefore have the same thickness. Thus, the spiral windings 2924, 2925 have upper and lower planes (or surfaces that are approximately planar (e.g., at least 95% flat)), which are parallel to the XY plane 3100 (e.g., the plane defined by the first and second axes 2921, 2922). The upper and lower planes of the spiral windings 2925, 2924 are defined by the upper and lower surfaces of the respective wires 3122, 3124. The thickness of the spiral windings 2925, 2924 about a third axis 2923 (e.g., the Z-axis) is equal to the thickness of the wires 3122, 3124. The wires 3122, 3124 can have a number of turns or windings suitable for generating the second oscillating magnetic field gradient. The length of the second electromagnetic coil set 2920 is measured along or parallel to the first axis 2921 (e.g., the X-axis). The width of the second electromagnetic coil set is measured along or parallel to the second axis 2922 (e.g., the Y-axis).

[0106] Wires 3122, 3124 can be configured to receive AC current in the range of about 10 A to about 50 A, including about 20 A, about 30 A, and about 40 A, or other currents. For example, wires 3022, 3024 can be Litz 50 / 32 AWG wire. Wires 3122, 3124 can be the same as or different from respective wires 3022, 3024.

[0107] 32 is a schematic perspective view of a third electromagnetic coil set 2930, according to one embodiment. The third electromagnetic coil set 2930 includes a helical winding 2932, which includes one or more wires 3212 wound in the shape of a ring, circle, or ring 2934 (generally annular). In one embodiment, two or more wires 3212 are wound adjacent to each other to form the ring 2934. The wires 3212 are wound in a counterclockwise direction, although in other embodiments, the wires 3212 can be wound in a clockwise direction.

[0108] Annulus 3924 has an inner diameter 3240 and an outer diameter 3250, where inner diameter 3240 defines a hollow region or inner cavity that does not include wire 3212. The ratio of outer diameter 3250 to inner diameter 3240 can be selected to allow for the generation of an appropriate number of windings of wire 3212 or third oscillating magnetic field gradient. In a specific embodiment, outer diameter 3250 can be approximately 28 cm and inner diameter 3240 can be approximately 10 cm. Wires 3212 have insulating coverings to prevent electrical shorting between each other.

[0109] The spiral winding 2932 has an axis of symmetry 3232 that is parallel to the third axis 2923 (e.g., the Z-axis). The spiral winding 2932 has a thickness (e.g., a profile) that is determined by the thickness of the wire 3212. Thus, the spiral winding 2932 has upper and lower planes (or substantially planar (e.g., at least 95% flat) surfaces) that are parallel to the XY plane 3200 (e.g., the plane defined by the first and second axes 2921, 2922). The upper and lower planes of the spiral winding 2932 are defined by the upper and lower surfaces, respectively, of the wire 3212. The thickness of the spiral winding 2932 about the third axis 2923 (e.g., the Z-axis) is equal to the thickness of the winding 3212. The wire 3212 can have a number of windings or turns suitable for generating a third oscillating magnetic field gradient.

[0110] Wire 3212 can be configured to receive an AC current in the range of about 10 A to about 50 A, including about 20 A, about 30 A, and about 40 A, or other currents. For example, wire 3212 can be a Litz 50 / 32 AWG wire. Wire 3212 can be the same as or different from wires 3022, 3024, 3122, and / or 3124.

[0111] FIG. 33 shows the total peak magnetic field gradient 3310 (||B X Graph 3300 shows an example of a total peak magnetic field 3310 (e.g., a first position-measuring oscillating magnetic field gradient) at various X values, for different Y values ​​from 0 to ±10 cm in ±2.5 cm intervals, while holding Z=7.5 cm. Due to the non-uniform nature of the Z coil's magnetic field along the X axis as the Y coordinate changes, the total peak magnetic field gradient strength decreases monotonically from 37 mT / m at Y=0 to 24 mT / m at Y=±10 cm. When operated simultaneously with 30 A AC power, the first and third electromagnetic coil sets 2910, 2930 can have a monotonic X FOV 3320 of approximately 20 cm within which the magnitude of the total peak magnetic field 3310 monotonically varies (increases) to uniquely encode position relative to the X axis (e.g., first axis 2921).

[0112] 34 is a graph 3400 illustrating an example of the total peak magnetic field gradient 3410 generated simultaneously by the second and third electromagnetic coil sets 2920, 2930. Graph 3400 shows the total peak magnetic field gradient 3410 (e.g., the second position measurement oscillating magnetic field gradient) at various Y values, for different X values ​​from 0 to ±10 cm in ±2.5 cm intervals, while holding Z=7.5 cm. Due to the non-uniform nature of the Z coil's magnetic field along the Y axis as the X coordinate changes, the total peak magnetic field gradient strength decreases monotonically from 37 mT / m at X=0 to 24 mT / m at X=±10 cm, similar to graph 3300. When operated simultaneously with 30 A AC power, the second and third electromagnetic coil sets 2920, 2930 have a monotonic Y FOV 3420 of approximately 20 cm (e.g., relative to the second axis 2922) within which the magnitude of the total peak magnetic field 3400 varies (increases) monotonically to uniquely encode relative position relative to the Y axis (e.g., the second axis 2922).

[0113] FIG. 35 shows the monotonically varying total peak magnetic field gradient 3510 (||B Z 3 is a graph 3500 illustrating an example of a total magnetic field (||). A plot of each total peak magnetic field 3510 (e.g., peak magnetic field for a third position measurement) can be measured at each relative X position as a function of Z position. A plot of each total peak magnetic field 3510 can be measured using a relative Y position of 0 cm. In addition, each total peak magnetic field 3510 can be measured over 10 cm, from Z=1 cm to Z=11 cm, where Z distance is the height (e.g., relative to the third axis 2923) from the top surface of the third electromagnetic coil set 2930.

[0114] In general, the magnitude of the total peak magnetic field 3510 decreases monotonically with increasing height (Z position) from the third electromagnetic coil set 2930 (e.g., relative to the third axis 2923). In addition, the total magnetic field 3510 is linear over most of the height (Z). The inner cavity 3242 is believed to enhance the linearity of the total magnetic field 3510; without the inner cavity 3242, the total magnetic field 3510 is more exponential. The third electromagnetic coil set 2930 can have a monotonic Z FOV 3520 of approximately 10 cm (e.g., relative to the third axis 2923), within which the magnitude of the total peak magnetic field 3510 varies (decreases) monotonically to uniquely encode relative position relative to the Z axis (e.g., the third axis 2923).

[0115] The gradient strength G is 46 mT / m at X=0, reaches a maximum of 67 mT / m at X=±5 cm, and drops to 48 mT / m at X=±10 cm, thus ensuring G>30 mT / m over a 20 cm length along the X axis. An AC current of 12.5 A can be used in the third electromagnetic coil set 1030 to generate graph 3500, which produces an average magnetic field gradient efficiency of 4.3 mT / m / A.

[0116] Because the spiral winding 2932 is symmetric about the X and Y axes, the total peak magnetic field is the same when measured at a relative X position of 0 cm, relative Y positions of ±2.5 cm, ±5 cm, ±7.5 cm, and ±10 cm, and from Z=1 cm to Z=11 cm (i.e., X and Y are switched in graph 3500).

[0117] Note that graphs 3300, 3400, and 3500 show the total peak magnetic field. Although AC current is used to generate the oscillating magnetic field, only peak values ​​are used in graphs 3300, 3400, and 3500. These peak values ​​correspond to the total magnetic field generated when DC current is used to generate the oscillating magnetic field, as disclosed, for example, in U.S. Pat. No. 1,145,7835, entitled "Electromagnet Gradient Apparatus For Micro-Device Localization," which is incorporated herein by reference. The oscillating magnetic field gradient 3601 and peak value 3602 for the total peak magnetic field gradient 3603 in the Z direction are shown in graph 3600 in FIG. 36.

[0118] To perform spatial mapping using magnetic field measurements from the 3D magnetic field sensor 110, a 500 Hz AC magnetic field was characterized within the FOV of the planar gradient coil of the 3D magnetic field generator 100. However, no commercially available sensors were available that could measure 500 Hz magnetic fields with a resolution of <10 μT while maintaining a range of 10–15 mT. This posed a challenge in obtaining the desired 500 Hz magnetic field measurements using sensors with output data rates that were too low and therefore prone to aliasing of frequency components of the oscillating magnetic field. We hypothesized that the frequency-independent nature of the peak value of a sinusoidal magnetic field could be exploited to predict the peak value at 500 Hz without having to measure the entire 500 Hz signal. To achieve this, we obtained magnetic field measurements at lower frequencies and found a scaling factor or correlation coefficient that could reliably predict measurements at the desired frequency of 500 Hz.

[0119] The AK09970N sensor was selected to perform magnetic field measurements given its low-noise performance. This sensor was mounted on an automated 3D stage consisting of X, Y, and Z linear actuators positioned above stacked X, Y, and Z gradient coils. Measurements were taken from 0 to 5 cm in 1 cm increments. These measurements were performed at several low frequency values ​​ranging from 47 Hz to 251 Hz. For a given frequency, the peak magnetic field magnitude was calculated by averaging 150 measurements at each location. The peak magnetic field measurements are frequency independent; for each fixed point along the Z axis, the peak values ​​remain consistent (with some standard deviation) around the average value. The margin of error can be attributed to sensor noise of 10–20 μT. This observation provided the ability to characterize high-frequency magnetic fields (still below 1 kHz) without the need to actually generate high-frequency signals for characterization purposes. During the actual characterization phase, the sensor was mounted on the automated 3D stage and measured in a 20 × 20 × 10 cm area. 3 The sensor was moved in 1 mm increments within a FOV of 1 mm. At each step, a magnetic field measurement was taken and stored in a look-up table (LUT) for later position decoding.

[0120] The LUT can be used to determine the 3D position coordinates corresponding to the total peak magnetic field value measured by the 3D magnetic field sensor 110, for example, according to the example algorithm 3800 in FIG.

[0121] The three magnetic field vectors acquired during measurement are (i) Bxx, Bxy, Bxz (measured when the X gradient is on), (ii) Byx, Byy, Byz (measured when the Y gradient is on), and Bzx, Bzy, Bzz (measured when the Z gradient is on). These nine values ​​can be compared with the values ​​stored in the LUT during the characterization phase and used to decode the angular orientation of the 3D magnetic field sensor 110 relative to the known orientation used during characterization. The vrrotvec() function in MATLAB (registered trademark) is used to find the angle transformation between the measured magnetic field vector and the reference data set from the LUT. The vrrotvec() function returns the axis-angle representation of the rotation transformation, which can then be converted to other types such as a rotation matrix, Euler angles, or quaternion format.

[0122] 39 is a block diagram of a 3D magnetic field sensor 3910 according to another embodiment. Sensor 3910 is the same as sensor 110, except that sensor 3910 includes two semiconductor chips 3921 and 3922. Semiconductor chips 3921 and 3922 are identical, except that semiconductor chip 3922 is rotated 90 degrees relative to semiconductor chip 3921. This 90-degree rotation causes second conductive coil 112B in semiconductor chip 3921 to function as first conductive coil 112A in semiconductor chip 3922. Both semiconductor chips 3921 and 3922 include third conductive coil 112C and processing circuitry 114. Semiconductor chips 3921 and 3922 can be mounted on a common substrate or printed circuit board 3900.

[0123] In other embodiments, each conductive coil 112A-C may be formed within a respective / corresponding semiconductor chip.

[0124] 40A is a top view of a 3D magnetic field sensor 4011 attached to a catheter 4001. The 3D magnetic field sensor 4011 can be attached to the tip or other part of the catheter 4001 to measure the position of the catheter 4001 (e.g., using the 3D magnetic field generator 100) during positioning, such as during a medical procedure. The 3D magnetic field sensor 4011 can be the same as the 3D magnetic field sensor 110 or the 3D magnetic field sensor 3910.

[0125] 40B is a top view of a 3D magnetic field sensor 4012 attached to a guidewire 4020 within a sheath or cannula 4030. The 3D magnetic field sensor 4012 can be attached to a tip 4022 or other portion of the guidewire 4020 to measure the position of the guidewire 4020 (e.g., using the 3D magnetic field generator 100) during positioning, such as during a medical procedure. The 3D magnetic field sensor 4012 can be the same as the 3D magnetic field sensor 110 or the 3D magnetic field sensor 3910.

[0126] 41 is a top view of a 3D magnetic field sensor 4110 attached to an anatomical feature, such as an organ 4100 of a human or other mammal. The 3D magnetic field sensor 4110 can be used to measure the position of the anatomical feature (e.g., the organ 4100) using the 3D magnetic field generator 100. Additionally or alternatively, the relative position of the anatomical feature with respect to a medical device 4120, such as a catheter (e.g., the catheter 4001) and / or a guidewire (e.g., the guidewire 4020) that includes a 3D magnetic field sensor 4122, can be measured using the 3D magnetic field sensor 4110 and the 3D magnetic field generator 100. The 3D magnetic field sensors 4110, 4122 can be the same as the 3D magnetic field sensor 110 or the 3D magnetic field sensor 3910.

[0127] 42 is a flowchart of a method 4200 for 3D object localization using oscillating magnetic field gradients, according to one embodiment. Method 4200 can be performed using system 10.

[0128] In step 4201, a 3D magnetic field sensor is positioned within the FOV of the 3D magnetic field generator. The 3D magnetic field sensor is configured to detect an oscillating magnetic field and determine a peak value or magnitude of the oscillating magnetic field. The 3D magnetic field sensor can be the same as the 3D magnetic field sensor 110, 3910, 4110. The 3D magnetic field generator can be the same as the 3D magnetic field generator 100.

[0129] In step 4202, a 3D magnetic field generator sequentially generates oscillating magnetic field gradients for three orthogonal axes, e.g., axes 2921-2923. At least a portion of each oscillating magnetic field gradient has a peak magnetic field magnitude that varies monotonically along the respective axis, and the peak magnetic field magnitude corresponds to a field of view (FOV) for each axis. Examples of FOVs for each axis include monotonic X FOV 3320, monotonic Y FOV 3420, and monotonic Z FOV 3520.

[0130] In step 4203, the 3D magnetic field sensor measures (e.g., with each conductive coil 112) each peak voltage in turn, which corresponds to the monotonically varying peak magnetic field magnitude of each oscillating magnetic field gradient. For example, the first peak voltage corresponds to the monotonically varying peak magnetic field magnitude of the first oscillating magnetic field gradient, the second peak voltage corresponds to the monotonically varying peak magnetic field magnitude of the second oscillating magnetic field gradient, and the third peak voltage corresponds to the monotonically varying peak magnetic field magnitude of the third oscillating magnetic field gradient.

[0131] In step 4204, the respective peak voltages are used to determine the relative position of the 3D magnetic field sensor with respect to the 3D magnetic field generator. The relative position may be determined using a look-up table, a model such as a trained machine model, and / or an algorithm to determine the relative position of the 3D magnetic field sensor with respect to the FOV of the 3D magnetic field generator.

[0132] In some embodiments, a 3D magnetic field sensor takes multiple samples / measurements of each oscillating magnetic field gradient and determines statistics (e.g., mean or median) of the respective peak voltages to improve accuracy.

[0133] The 3D magnetic field sensors can determine their relative positions using circuitry on the 3D magnetic field sensors and / or program instructions stored within the 3D magnetic field sensors. Additionally or alternatively, the 3D magnetic field sensors can transmit their peak voltages to an external device (e.g., a computer such as a laptop, desktop, tablet, smartphone, or other computer) using communication circuitry on the 3D magnetic field sensors, for example, via Bluetooth, WiFi, NFC (near-field communication), cellular, backscatter, and / or other communication standards or protocols. The external device then uses the peak voltages to determine the relative position of the 3D magnetic field sensors with respect to the FOV of the 3D magnetic field generator. For example, the external device (or the 3D magnetic field sensors) can use a lookup table, a model such as a trained machine learning model, and / or an algorithm (e.g., algorithm 3800) to determine the relative position of the 3D magnetic field sensors with respect to the FOV of the 3D magnetic field generator. The relative position of the 3D magnetic field sensors can be displayed graphically, for example, on a monitor or display screen coupled to the external device.

[0134] In some embodiments, steps 4202 to 4024 may be repeated while the object is within the FOV of the 3D magnetic field generator to continuously determine the relative position of the 3D magnetic field sensor with respect to the FOV of the 3D magnetic field generator.

[0135] In some embodiments, method 4200 can be performed while the 3D magnetic field sensor is attached and / or mechanically coupled to an object to determine the relative position of the object or a particular portion of the object to which the magnetic field sensor is attached. The object can be a medical device (e.g., a catheter 4001 or a guidewire 4020), an anatomical feature of a mammal (e.g., an organ 4100), or other object.

[0136] In some embodiments, method 4200 can be performed while a first 3D magnetic field sensor is attached to a first object and a second 3D magnetic field sensor is attached to a second object to determine the relative position of the first object (e.g., of the first magnetic field sensor) with respect to the 3D magnetic field generator, the relative position of the second object (e.g., of the second magnetic field sensor), and / or the relative position of the first object (e.g., of the first magnetic sensor) with respect to the second object (e.g., the second magnetic sensor) as shown in FIG. 41 .

[0137] The present invention should not be construed as limited to the particular embodiments described above. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of ordinary skill in the art to which the present invention is directed upon review of the present disclosure. The above-described embodiments may be implemented in a variety of ways. One or more aspects and embodiments involving the execution of a process or method may utilize program instructions executable by an apparatus (e.g., a computer, processor, or other device) to perform or control the execution of the process or method.

[0138] In this regard, various inventive concepts may be embodied as a non-transitory computer-readable storage medium (or multiple non-transitory computer-readable storage media) (e.g., any suitable type of computer memory, including transient or non-transitory digital storage devices, circuitry in field programmable gate arrays or other semiconductor devices, or other tangible computer storage media) encoded with one or more programs that, when executed on one or more computers or other processors, perform one or more of the various embodiments described above. When implemented in software (e.g., as an application), this software code may be executed on any suitable processor or collection of processors, whether provided within a single computer or distributed across multiple computers.

[0139] It will be further apparent that a computer may be embodied in any of a number of forms, such as, by way of non-limiting example, a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer. In addition, a computer may be embodied in the form of devices not generally thought of as computers, but which have suitable processing capabilities, including personal digital assistants (PDAs), smartphones, or any other suitable portable or fixed electronic device.

[0140] A computer may also have one or more communications devices that may be used to interconnect the computer with one or more other devices or systems, such as a network of any suitable form, including local area networks or wide area networks, such as enterprise networks, intelligent networks (INs), or the Internet. Such networks may be based on any suitable technology and may operate according to any suitable protocol, and may include wireless networks or wired networks.

[0141] A computer may also have one or more input devices and / or one or more output devices. These devices may be used, among other things, to provide a user interface. Output devices that can be used to provide a user interface include a printer or display screen for a visual presentation of output and a speaker or other sound-generating device for an audible presentation of output. Examples of input devices that can be used for a user interface include a keyboard and pointing devices such as a mouse, touchpad, and digitizing tablet. As another example, a computer may receive input information through voice recognition or in other audible formats.

[0142] The non-transitory computer-readable medium may be portable such that the program stored on the medium can be loaded onto one or more different computers or other processors to implement various one or more of the above-described aspects. In some embodiments, the computer-readable medium may be a non-transitory medium.

[0143] The terms "program," "application," and "software" are used herein in a general sense to refer to any type of computer code or set of computer-executable instructions that can be used to program a computer or other processor to implement the various aspects described above. Additionally, it will be apparent that, according to one aspect, one or more computer programs that, when executed, perform the methods of the present application need not reside on a single computer or processor, but may be distributed in a modular manner across multiple computers or processors to implement various aspects of the present application.

[0144] Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or separated as desired.

[0145] Additionally, data structures may be stored in a computer-readable medium in any suitable format. For ease of explanation, data structures may be depicted as having fields that are related through their locations in the data structure. Such relationships may in turn be achieved by assigning storage locations for the fields to locations in the computer-readable medium that convey the relationship between the fields. However, any suitable mechanism may be used to establish relationships between information in multiple fields of a data structure, including through the use of pointers, tags, or other mechanisms that establish relationships between data elements.

[0146] Thus, the present disclosure and claims encompass new and novel improvements to existing methods and techniques, improvements not previously known or realized to achieve the beneficial results described above. Users of the above methods and systems will tangibly benefit from the functionality now enabled by the specific improvements described herein, which provide system effects and system outputs to users of the systems. It is expected that significantly improved operation can be achieved when implementing the claimed invention using the technical components recited herein.

[0147] Also, as described above, some aspects may be combined into one or more methods. The actions performed as part of a method may be ordered in any suitable manner. Thus, embodiments may be construed as performing actions in an order different from that illustrated, including performing some actions simultaneously, even if shown as sequential actions in the illustrated embodiments.

Claims

1. a semiconductor substrate; a plurality of metal layers disposed on the semiconductor substrate; a plurality of insulating layers disposed on the semiconductor substrate; a plurality of metal vias defined in the insulating layer; an on-chip electrical coil comprising the metal layer and a planar spiral formed by the metal vias, each of the insulating layers is disposed between an adjacent pair of the metal layers to form an alternating arrangement of the metal layers and the insulating layers; each of the metal vias electrically connects a respective adjacent pair of the metal layers; The planar spiral includes a plurality of interconnected loops, each of which includes two metal wires, an intra-loop column, and an inter-loop column, the two metal wires being disposed within a respective one of the metal layers, the intra-loop column electrically connecting the two metal wires of each of the loops, and the inter-loop column electrically connecting one of the two metal wires of each of the loops to one of the two metal wires of the loop following that loop. On-chip electrical coil.

2. the two metal wires of each of the loops have a respective length measured along a first axis, a respective width measured along a second axis orthogonal to the first axis, and a respective height measured along a third axis orthogonal to the first and second axes; the two metal wires in each of the loops are spatially offset from one another along the third axis; The on-chip electric coil of claim 1 , wherein the respective length of each of the metal wires is greater than the respective width.

3. 3. The on-chip electric coil of claim 2, wherein the ratio of the length to the width of each of the metal wires is from about 500:1 to about 10,000:

1.

4. The on-chip electric coil of claim 2 , wherein each of the loops extends parallel to a plane defined by the first axis and the third axis.

5. the plurality of interconnected loops includes a first loop and a second loop; The two metal wires of the second loop are disposed between the two metal wires of the first loop. The on-chip electric coil of claim 1 .

6. the two metal wires of the first loop include an upper metal wire disposed in an upper metal layer of the metal layers and a lower metal wire disposed in a lower metal layer of the metal layers; the two metal wires of the second loop include a third metal wire disposed in a third metal layer of the metal layers and a fourth metal wire disposed in a fourth metal layer of the metal layers, the third metal layer and the fourth metal layer being between the upper metal layer and the lower metal layer; The first loop includes a column within the first loop electrically connecting the upper metal layer and the lower metal layer, the column within the first loop including at least: a first metal segment of the third metal layer; a first metal segment of the fourth metal layer; a first metal via electrically connecting the upper metal wire to the first segment of the third metal layer; a second metal via electrically connecting the first segment of the third metal layer to the first metal segment of the fourth metal layer; a third metal via electrically connecting the first segment of the fourth metal layer to the lower metal wire; The first loop includes a first inter-loop column electrically connecting the upper metal wire to the fourth metal wire, the first inter-loop column including at least: a second segment of the third metal layer; a third metal via electrically connecting the upper metal wire to the second metal segment of the third metal layer; a fourth metal via electrically connecting the second metal segment of the third metal layer to the fourth metal wire. The on-chip electric coil of claim 5 .

7. the planar helix is ​​a first planar helix; the on-chip electrical coil further includes a second planar helix electrically connected to the first planar helix; the interconnected loops of the first and second planar helices are wound around an axis, and the first and second planar helices are spatially offset from one another along the axis. The on-chip electric coil of claim 1 .

8. the on-chip electrical coil includes a plurality of the planar spirals; the interconnected loops of each of the planar spirals are wound around the axis; the plurality of planar spirals are spatially offset from one another along the axis; Adjacent planar spirals are electrically connected to each other; The on-chip electric coil of claim 7.

9. further comprising a plurality of intra-helical connecting wires; each of the intra-spiral connecting wires electrically connects a first terminal and a second terminal of an adjacent one of the planar spirals, respectively; The on-chip electric coil of claim 8.

10. the axis is a first axis, the length of the on-chip electrical coil is measured along the first axis; the height of each of the planar spirals is measured along a second axis; each of the planar spirals is parallel to a plane defined by the first and second axes; the length of the on-chip electrical coil is greater than the height of each of the planar spirals; The on-chip electric coil of claim 8.

11. The on-chip electric coil of claim 10, wherein the ratio of the length of the on-chip electric coil to the height of each of the planar spirals is between about 50:1 and about 250:

1.

12. a semiconductor substrate; a plurality of metal layers disposed on the semiconductor substrate; a plurality of insulating layers disposed on the semiconductor substrate; a plurality of metal vias defined in the insulating layer; a first conductive coil having a first planar spiral formed by the metal layer and the metal via; a second conductive coil having a second planar spiral formed by at least a portion of the metal layer and at least a portion of the metal via; the metal layers are spaced apart along a first axis; each of the insulating layers is disposed between an adjacent pair of the metal layers to form an alternating arrangement of the metal layers and the insulating layers; each of the metal vias electrically connects a respective adjacent pair of the metal layers; the first planar helix includes a plurality of interconnected first loops wound about a second axis orthogonal to the first axis; the second planar helix includes a plurality of interconnected second loops wound about the second axis; On-chip magnetic sensor.

13. The on-chip magnetic sensor of claim 12 , wherein the at least a portion of the metal layer and the at least a portion of the metal via form a continuous metal structure along the second axis and along the entire length of the second planar spiral.

14. 13. The on-chip magnetic sensor of claim 12, further comprising a third conductive coil having a third planar spiral formed by the metal layer and the metal via, the third planar spiral including a plurality of interconnected third loops wound about a third axis orthogonal to the first axis and the second axis.

15. 15. The on-chip magnetic sensor of claim 14, wherein each of the interconnected first loops and each of the interconnected third loops includes a respective metal wire pair, a respective intra-loop column, and a respective inter-loop column, the respective metal wire pairs being disposed in the respective metal layers, the respective intra-loop columns electrically connecting the respective metal wire pairs of each of the interconnected first loops and each of the interconnected third loops, and the respective inter-loop columns electrically connecting one metal wire of the metal wire pair of each of the interconnected first loops to one metal wire of the metal wire pair of the interconnected first loop subsequent to the interconnected first loop and electrically connecting one metal wire of the metal wire pair of each of the interconnected third loops to one metal wire of the metal wire pair of the interconnected third loop subsequent to the interconnected third loop.

16. a semiconductor substrate; a plurality of metal layers disposed on the semiconductor substrate; a plurality of insulating layers disposed on the semiconductor substrate; a plurality of metal vias defined in the insulating layer; a first conductive coil having a plurality of first planar spirals formed by the metal layer and the metal vias; a second conductive coil having a plurality of second planar spirals formed by the metal layer and the metal vias; a third conductive coil having a third planar spiral formed by at least a portion of the metal layer and at least a portion of the metal via; each of the insulating layers is disposed between an adjacent pair of the metal layers to form an alternating arrangement of the metal layers and the insulating layers; each of the metal vias electrically connects a respective adjacent pair of the metal layers; each of the first planar spirals includes a plurality of interconnected first loops wound around a first axis, adjacent first planar spirals are electrically connected to each other; each of the second planar spirals includes a plurality of interconnected second loops wound about a second axis perpendicular to the first axis, and adjacent second planar spirals are electrically connected to each other; the third planar spiral includes a plurality of interconnected third loops wound about a third axis perpendicular to the first axis and the second axis, and the metal layers are spaced apart along the third axis. Three-dimensional on-chip magnetic sensor.

17. the first planar spirals are spatially offset from one another along the first axis; the second planar helices being spatially offset from one another along the second axis; The three-dimensional on-chip magnetic sensor according to claim 16.

18. a plurality of first intra-helical connecting wires; a plurality of second intra-helical connecting wires; each of the first intra-spiral connecting wires electrically connects a first terminal and a second terminal of an adjacent first planar spiral, respectively; each of the second intra-spiral connecting wires electrically connects a first terminal and a second terminal of an adjacent second planar spiral, respectively; The three-dimensional on-chip magnetic sensor according to claim 16.

19. A catheter attached to the three-dimensional on-chip magnetic sensor of claim 16.

20. A guide wire attached to the three-dimensional on-chip magnetic sensor of claim 16.

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