EP0443173A1 - Wideband tunable monolithic inductor - Google Patents

Wideband tunable monolithic inductor Download PDF

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Publication number
EP0443173A1
EP0443173A1 EP90124733A EP90124733A EP0443173A1 EP 0443173 A1 EP0443173 A1 EP 0443173A1 EP 90124733 A EP90124733 A EP 90124733A EP 90124733 A EP90124733 A EP 90124733A EP 0443173 A1 EP0443173 A1 EP 0443173A1
Authority
EP
European Patent Office
Prior art keywords
inductor
conical
wideband
recited
circuit board
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP90124733A
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German (de)
French (fr)
Other versions
EP0443173B1 (en
Inventor
Cornelis T. Veenendaal
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tektronix Inc
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Tektronix Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tektronix Inc filed Critical Tektronix Inc
Publication of EP0443173A1 publication Critical patent/EP0443173A1/en
Application granted granted Critical
Publication of EP0443173B1 publication Critical patent/EP0443173B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F17/00—Fixed inductances of the signal type 
    • H01F17/04—Fixed inductances of the signal type  with magnetic core
    • H01F17/045—Fixed inductances of the signal type  with magnetic core with core of cylindric geometry and coil wound along its longitudinal axis, i.e. rod or drum core
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F21/00—Variable inductances or transformers of the signal type
    • H01F21/02—Variable inductances or transformers of the signal type continuously variable, e.g. variometers
    • H01F21/06—Variable inductances or transformers of the signal type continuously variable, e.g. variometers by movement of core or part of core relative to the windings as a whole
    • H01F21/065—Measures for obtaining a desired relation between the position of the core and the inductance
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F5/00—Coils
    • H01F2005/006—Coils with conical spiral form

Definitions

  • the present invention relates to discrete inductors, and more particularly to a wideband tunable monolithic inductor having a conical construction that presents very low parasitic capacitances and, thus, a very small amount of resonances.
  • the inter-winding capacitance in conjunction with the individual inductances of each coil winding produces many resonances throughout a frequency range for the inductor, as shown on the Smith chart of Fig. 1.
  • the Smith chart is a circular plot of the impedance of a transmission line, such as is formed by an inductor, in terms of the resistive and reactive components over a frequency range of interest.
  • the loops in the Smith chart occur at frequencies where the parasitic capacitances of the inductor form resonances with the coil windings.
  • Existing inductors that operate into high frequency use the technique of circuit synthesis where a small series inductor is used to buffer out the parasitic capacitances from a large value, low frequency inductor.
  • several inductors are connected in series, each optimized for a narrow band of frequency, the series of inductors yielding an equivalent wideband inductor.
  • the present invention provides a wideband tunable monolithic inductor of conical construction having low parasitic capacitances and a very small amount of resonances.
  • a conical mandrel of a dielectric material has a slot in the tip to secure one end of an electrical wire to be wound upon the mandrel. The wire is wrapped around the mandrel in contiguous windings to achieve the desired inductance.
  • a slug may be mounted in the core of the mandrel to tune the inductance as needed.
  • a base on the mandrel provides means for mounting the inductor on a circuit board by inserting the tip of the inductor in a hole in the circuit board adjacent a lead and supporting the inductor with spacers between the base and the circuit board. Alternatively the mandrel may be removed after the coil is wound to produce an airwound, conical configuration.
  • Fig. 1 is a Smith chart for a cylindrically constructed inductor of the prior art.
  • Fig. 2 is a side plan view of a wideband tunable monolithic inductor according to the present invention mounted on a circuit board.
  • Fig. 3 is a bottom plan view of a mandrel for the wideband tunable monolithic inductor of Fig. 2.
  • Fig. 4 is a Smith chart for the wideband tunable monolithic inductor of the present invention.
  • a wideband tunable monolithic inductor 10 has a mandrel 11 with a conical section 12, a cylindrical section 14 contiguous with the conical section, and a base 16 contiguous with the cylindrical section.
  • the tip 18 of the conical section 12 has a hole or slot 20 for securing one end of a wire 22.
  • the wire 22 is wrapped around the mandrel 11 in contiguous windings around the conical section 12 and a contiguous portion of the cylindrical section 14 to achieve a desired total inductance.
  • the wire 22 is secured to the mandrel 11 by suitable means, such as gluing.
  • An axial hole 24 in the cylindrical section 14 through the base 16 is threaded to accept an appropriate slug for tuning the inductor 10 to a desired inductance, as is well known in the art.
  • the mandrel 11 is of a dielectric material, such as styrene.
  • the base 16 has holes 26 that are used in mounting the inductor 10 on a circuit board 28.
  • the inductor 10 is mounted on the circuit board 28 by inserting the tip 18 into a suitable hole 30 in the circuit board. Spacers 32 are placed between the base 16 and the circuit board 28 and suitable means, such as nuts and bolts or screws, are inserted through the base holes 26 and spacers to secure the inductor 10 to the circuit board. A short end of the wire 22 from the tip 18 is electrically connected to a conductive lead 34 on the circuit board 28, and a long end of the wire from the cylindrical section 14 is electrically connected to another conductive lead 34 by conventional means, such as soldering.
  • the conically coiled wire 22 may be removed from the mandrel 11 to form an airwound, conical inductor.
  • the shape of the coil is maintained by stiffening the coil with a suitable epoxy or glue between windings to provide a rigid form.
  • Such an airwound inductor may be attached to a base similar to the integral base 16 of the mandrel 11 by suitable means for mounting on the circuit board 28 in the same manner.
  • the conical construction presents a very small inductance and, consequently, a very small inter-winding capacitance at the tip 18, providing a high impedance at a very high frequency, such as 6-10 gigahertz.
  • a very high frequency such as 6-10 gigahertz.
  • the inductor 10 behaves like an ideal inductor, i.e., the reactive component of the impedance decreases linearly with decreasing frequency.
  • the result is a wideband inductor with very small parasitic shunt capacitances at high frequency, and hence capable of delivering a high impedance at very high frequency.
  • the upper frequency limit is infinite. But the theoretical limit is constrained by the amount of current needed for a particular circuit application which in turn determines the minimum wire diameter and smallest possible first winding.
  • Fig. 4 is a Smith chart for the inductor 10 over a range of frequencies from 45 MHz to 6 GHz.
  • the resistive component of the impedance is 230 ohms while the reactive component is -772 ohms which compares with 15 and 70 ohms for the conventional cylindrical inductor of Fig. 1 at approximately the same frequency, also indicated by marker #1.
  • the total inductance of the coil windings determines the lower cutoff frequency, and the diameter of the first coil winding, limited by the wire size, determines the highest cutoff frequency.
  • Examples of applications for the inductor 10 are bias-T and split-path amplifiers using an LC diplexer network.
  • the inductor is used to inject a DC bias signal, but at high frequencies the inductor is required to present a high impedance so that the AC signals are not degraded by the parasitic shunt capacitances of the inductor.
  • the diplexer network having an inductor and a capacitor, is used to combine/split a signal from/into high and low frequencies. If the inductor looks like a low impedance at high frequencies, then the high frequency signals, AC-coupled through the capacitor, are loaded by the conventional inductor, resulting in overall signal degradation.
  • the conical inductor 10 provides a high impedance at high frequencies so that the high frequency signals are not loaded by the inductor, improving signal performance.
  • the present invention provides a wideband tunable monolithic inductor having a conical construction to present low parasitic capacitances and provide high impedances over a wide frequency range without appreciable amounts of resonances.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Coils Or Transformers For Communication (AREA)

Abstract

A wideband tunable monolithic inductor has a conical construction that presents very low parasitic capacitances. The frequency response of the inductor is determined by the diameter of the smallest coil at the tip for high frequency cutoff and by the total inductance for low frequency cutoff.

Description

    Background of the Invention
  • The present invention relates to discrete inductors, and more particularly to a wideband tunable monolithic inductor having a conical construction that presents very low parasitic capacitances and, thus, a very small amount of resonances.
  • In a conventional, cylindrically constructed inductor the inter-winding capacitance in conjunction with the individual inductances of each coil winding produces many resonances throughout a frequency range for the inductor, as shown on the Smith chart of Fig. 1. The Smith chart is a circular plot of the impedance of a transmission line, such as is formed by an inductor, in terms of the resistive and reactive components over a frequency range of interest. The loops in the Smith chart occur at frequencies where the parasitic capacitances of the inductor form resonances with the coil windings. Existing inductors that operate into high frequency use the technique of circuit synthesis where a small series inductor is used to buffer out the parasitic capacitances from a large value, low frequency inductor. Sometimes several inductors are connected in series, each optimized for a narrow band of frequency, the series of inductors yielding an equivalent wideband inductor.
  • What is desired is a low parasitic capacitance inductor having a wideband characteristic with a very small amount of resonances.
    • Summary of the Invention
  • Accordingly the present invention provides a wideband tunable monolithic inductor of conical construction having low parasitic capacitances and a very small amount of resonances. A conical mandrel of a dielectric material has a slot in the tip to secure one end of an electrical wire to be wound upon the mandrel. The wire is wrapped around the mandrel in contiguous windings to achieve the desired inductance. A slug may be mounted in the core of the mandrel to tune the inductance as needed. Also a base on the mandrel provides means for mounting the inductor on a circuit board by inserting the tip of the inductor in a hole in the circuit board adjacent a lead and supporting the inductor with spacers between the base and the circuit board. Alternatively the mandrel may be removed after the coil is wound to produce an airwound, conical configuration.
  • The objects, advantages and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawing.
    • Brief Description of the Drawing
  • Fig. 1 is a Smith chart for a cylindrically constructed inductor of the prior art.
  • Fig. 2 is a side plan view of a wideband tunable monolithic inductor according to the present invention mounted on a circuit board.
  • Fig. 3 is a bottom plan view of a mandrel for the wideband tunable monolithic inductor of Fig. 2.
  • Fig. 4 is a Smith chart for the wideband tunable monolithic inductor of the present invention.
    • Description of the Preferred Embodiment
  • Referring now to Figs. 2 and 3 a wideband tunable monolithic inductor 10 has a mandrel 11 with a conical section 12, a cylindrical section 14 contiguous with the conical section, and a base 16 contiguous with the cylindrical section. The tip 18 of the conical section 12 has a hole or slot 20 for securing one end of a wire 22. The wire 22 is wrapped around the mandrel 11 in contiguous windings around the conical section 12 and a contiguous portion of the cylindrical section 14 to achieve a desired total inductance. The wire 22 is secured to the mandrel 11 by suitable means, such as gluing. An axial hole 24 in the cylindrical section 14 through the base 16 is threaded to accept an appropriate slug for tuning the inductor 10 to a desired inductance, as is well known in the art. The mandrel 11 is of a dielectric material, such as styrene. The base 16 has holes 26 that are used in mounting the inductor 10 on a circuit board 28.
  • The inductor 10 is mounted on the circuit board 28 by inserting the tip 18 into a suitable hole 30 in the circuit board. Spacers 32 are placed between the base 16 and the circuit board 28 and suitable means, such as nuts and bolts or screws, are inserted through the base holes 26 and spacers to secure the inductor 10 to the circuit board. A short end of the wire 22 from the tip 18 is electrically connected to a conductive lead 34 on the circuit board 28, and a long end of the wire from the cylindrical section 14 is electrically connected to another conductive lead 34 by conventional means, such as soldering.
  • Alternatively the conically coiled wire 22 may be removed from the mandrel 11 to form an airwound, conical inductor. The shape of the coil is maintained by stiffening the coil with a suitable epoxy or glue between windings to provide a rigid form. Such an airwound inductor may be attached to a base similar to the integral base 16 of the mandrel 11 by suitable means for mounting on the circuit board 28 in the same manner.
  • The conical construction presents a very small inductance and, consequently, a very small inter-winding capacitance at the tip 18, providing a high impedance at a very high frequency, such as 6-10 gigahertz. As the coil windings gradually increase in diameter, the frequency presented with a high impedance decreases. At very low frequencies the inductor 10 behaves like an ideal inductor, i.e., the reactive component of the impedance decreases linearly with decreasing frequency. The result is a wideband inductor with very small parasitic shunt capacitances at high frequency, and hence capable of delivering a high impedance at very high frequency. Theoretically with a point tip and infinitely small wire, the upper frequency limit is infinite. But the theoretical limit is constrained by the amount of current needed for a particular circuit application which in turn determines the minimum wire diameter and smallest possible first winding.
  • Fig. 4 is a Smith chart for the inductor 10 over a range of frequencies from 45 MHz to 6 GHz. At 4.124175 GHz, indicated by marker #1, the resistive component of the impedance is 230 ohms while the reactive component is -772 ohms which compares with 15 and 70 ohms for the conventional cylindrical inductor of Fig. 1 at approximately the same frequency, also indicated by marker #1. The total inductance of the coil windings determines the lower cutoff frequency, and the diameter of the first coil winding, limited by the wire size, determines the highest cutoff frequency.
  • Examples of applications for the inductor 10 are bias-T and split-path amplifiers using an LC diplexer network. In the bias-T amplifier the inductor is used to inject a DC bias signal, but at high frequencies the inductor is required to present a high impedance so that the AC signals are not degraded by the parasitic shunt capacitances of the inductor. In the split-path amplifier the diplexer network, having an inductor and a capacitor, is used to combine/split a signal from/into high and low frequencies. If the inductor looks like a low impedance at high frequencies, then the high frequency signals, AC-coupled through the capacitor, are loaded by the conventional inductor, resulting in overall signal degradation. However the conical inductor 10 provides a high impedance at high frequencies so that the high frequency signals are not loaded by the inductor, improving signal performance.
  • Thus the present invention provides a wideband tunable monolithic inductor having a conical construction to present low parasitic capacitances and provide high impedances over a wide frequency range without appreciable amounts of resonances.

Claims (7)

  1. A wideband inductor comprising:
    a conical mandrel of a dielectric material; and
    an electrically conductive wire secured at one end to the tip of the conical mandrel and wrapped around the conical mandrel to form contiguous coils of wire of increasing diameter.
  2. A wideband inductor as recited in claim 1 wherein the conical mandrel comprises:
    a conical section having means for securing the electrically conductive wire at the tip; and
    a cylindrical section contiguous with the base of and axially aligned with the conical section.
  3. A wideband inductor as recited in claim 2 wherein the conical mandrel further comprises a base section contiguous with the cylindrical section, the base section having means for securing the conical mandrel to a circuit board.
  4. A wideband inductor as recited in claim 3 wherein the securing means comprises:
    a spacer; and
    means for connecting the spacer between the base section and the circuit board to secure the wideband inductor fixedly to the circuit board.
  5. A wideband inductor as recited in claim 1 further comprising means for tuning the inductance of the wide band inductor.
  6. A wideband inductor as recited in claim 5 wherein the tuning means comprises a slug of a magnetic material adjustable within a cavity along the axis of
  7. A wideband inductor comprising an electrically conductive wire wound in a conical configuration so that each successive winding has a diameter greater that the diameter of the immediately preceding winding to reduce inter-winding parasitic capacitance.
EP19900124733 1989-12-26 1990-12-19 Wideband tunable monolithic inductor Expired - Lifetime EP0443173B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US45676389A 1989-12-26 1989-12-26
US456763 1989-12-26

Publications (2)

Publication Number Publication Date
EP0443173A1 true EP0443173A1 (en) 1991-08-28
EP0443173B1 EP0443173B1 (en) 1994-05-18

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ID=23814068

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900124733 Expired - Lifetime EP0443173B1 (en) 1989-12-26 1990-12-19 Wideband tunable monolithic inductor

Country Status (4)

Country Link
EP (1) EP0443173B1 (en)
JP (1) JPH04137507A (en)
DE (1) DE69009040T2 (en)
HK (1) HK89894A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1333454A1 (en) 2002-01-31 2003-08-06 Rohde & Schwarz GmbH & Co. KG Overvoltage protection device
US7518463B2 (en) * 2004-12-23 2009-04-14 Agilent Technologies, Inc. Circuit assembly with conical inductor
WO2013017366A3 (en) * 2011-08-04 2013-04-04 Rohde & Schwarz Gmbh & Co. Kg Over-voltage protection device having a coil assembly
CN118366772A (en) * 2024-06-17 2024-07-19 深圳市凌昱微科技有限公司 Packaging equipment and packaging method for inductance device

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4498258B2 (en) * 2005-10-13 2010-07-07 富士通オプティカルコンポーネンツ株式会社 Coil package
US8072773B2 (en) 2008-04-04 2011-12-06 John Mruz Ultra-wideband assembly system and method
JP6695136B2 (en) 2015-12-11 2020-05-20 株式会社村田製作所 Wirewound inductor

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2005203A (en) * 1932-05-04 1935-06-18 Johnson Lab Inc Variable inductance device
US2442776A (en) * 1944-11-08 1948-06-08 Thomas A Newkirk Radio-frequency choke coil
GB839901A (en) * 1957-11-21 1960-06-29 Automatic Telephone & Elect Improvements in or relating to electrical induction coils

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2005203A (en) * 1932-05-04 1935-06-18 Johnson Lab Inc Variable inductance device
US2442776A (en) * 1944-11-08 1948-06-08 Thomas A Newkirk Radio-frequency choke coil
GB839901A (en) * 1957-11-21 1960-06-29 Automatic Telephone & Elect Improvements in or relating to electrical induction coils

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 10, no. 263 (E-435)(2319) 09 September 1986, & JP-A-61 89610 (MATSUSHITA ELECTRIC IND.) 07 May 1986, *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1333454A1 (en) 2002-01-31 2003-08-06 Rohde & Schwarz GmbH & Co. KG Overvoltage protection device
US7518463B2 (en) * 2004-12-23 2009-04-14 Agilent Technologies, Inc. Circuit assembly with conical inductor
WO2013017366A3 (en) * 2011-08-04 2013-04-04 Rohde & Schwarz Gmbh & Co. Kg Over-voltage protection device having a coil assembly
US9640970B2 (en) 2011-08-04 2017-05-02 Rohde & Schwarz Gmbh & Co. Kg Over-voltage protection device having a coil assembly
CN118366772A (en) * 2024-06-17 2024-07-19 深圳市凌昱微科技有限公司 Packaging equipment and packaging method for inductance device

Also Published As

Publication number Publication date
EP0443173B1 (en) 1994-05-18
DE69009040D1 (en) 1994-06-23
JPH04137507A (en) 1992-05-12
HK89894A (en) 1994-09-09
DE69009040T2 (en) 1994-12-22

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