US3267478A - Tunable ferromagnetic rod loop antenna - Google Patents

Tunable ferromagnetic rod loop antenna Download PDF

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Publication number
US3267478A
US3267478A US252400A US25240063A US3267478A US 3267478 A US3267478 A US 3267478A US 252400 A US252400 A US 252400A US 25240063 A US25240063 A US 25240063A US 3267478 A US3267478 A US 3267478A
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US
United States
Prior art keywords
sleeve
antenna
magnetic
coupling
length
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.)
Expired - Lifetime
Application number
US252400A
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English (en)
Inventor
Schiefer Gerd
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.)
US Philips Corp
North American Philips Co Inc
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US Philips Corp
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Publication date
Application filed by US Philips Corp filed Critical US Philips Corp
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Publication of US3267478A publication Critical patent/US3267478A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H01Q7/005—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop with variable reactance for tuning the antenna
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H01Q7/06—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop with core of ferromagnetic material
    • H01Q7/08—Ferrite rod or like elongated core

Definitions

  • Magnetic antennas which comprise a cylindrical body of ferromagnetic material, for example ferrite, wherein the ratio of slenderness, i.e., the ratio between the length of the cylinder and its diameter, exceeds 5 to l.
  • the cylindrical body in these devices is also provided with a coupling winding for connecting the antenna to a radio receiver, or the like.
  • Magnetic antennas when compared with the more conventional electric dipoles, have the advantage that they are less sensitive to various radio and electrical interferences. Antennas of this type are usually mounted inside the radio receiver apparatus. However, magnetic antennas of small size have a very low radiation resistance so that difficulties arise when the antenna impedance must be matched to the impedance of the transmission line to which it is coupled or of the input stage of a radio receiver.
  • An object of this invention is to provide an improved magnetic antenna construction which provides a higher efficiency and sensitivity than conventional devices of this type.
  • Another object of this invention is to provide an improved magnetic antenna apparatus having a characteristic impedance which can be closely matched to the impedance of the transmission line to which it is coupled.
  • the antenna comprises a cylindrical body of ferromagnetic material which is surrounded by a cylindrical sheath or sleeve of electrically conductive material, for example copper.
  • This sheath is provided with a longitudinal gap across which there is connected a tuning capacitance distributed throughout its length.
  • the length of the cylindrical sheath is preferably between 0.6 5 and 0.9 times the length of the cylindrical body of ferromagnetic material.
  • FIG. 1 is an elevation view of a magnetic antenna apparatus incorporating the principles of the present invention.
  • FIG. 2 is a plan view of the novel apparatus of FIG. 1.
  • FIG. 3 illustrates another preferred embodiment of the invention.
  • FIG. 4 shows a sectional view taken along the line A-B of FIG. 3.
  • FIG. 5 is a sectional view of an alternative embodiment of the invention.
  • the magnetic antenna shown in FIGS. l and 2 comprises a cylindrical core 1 composed of a ferromagnetic material, for example a ferrite.
  • the core 1 is provided with a coupling winding 2, shown diagrammatically as having a pair of supply conductors 3 for coupling the antenna to the input stage of a radio receiver.
  • the core 1 is surrounded by a sleeve or sheath 4 of electrically conductive material, for example of copper.
  • the sleeve is also provided with a longitudinal gap extending the entire length of the sleeve.
  • Sleeve 4 is slightly shorter than core 1.
  • the opposite edges of the sleeve which form the gap 5 are capacitatively coupled with each other by means of a tuning capacitance 6 distributed over the length of the gap.
  • This capacitance may consist, for example, as is shown in FIG. 1, of a plurality of capacitors 6' equidistantly spaced.
  • Capacitance 6 preferably is given a value at which it resonates with the inductance of sleeve 4 at the midpoint of the operation wavelength range for which the antenna is intended for use. For example, if the apparatus is to be. used for the reception of the broadcast frequency modulation band which extends from 88 to 102 mc./s. the sleeve 4 and capacitors 6 are preferably tuned to approximately mc./s.
  • the ratio of the length of the ferrite core 1 to its diameter must not be too small.
  • the ratio is preferably higher than 5; the ratio 8 having been found to be a useful value in practice.
  • the length of the sleeve 4 should preferably lie between 0.65 and 0.9 times the length of the core 1. If the sleeve is longer, the receptive power or sensitivity. of the antenna decreases rapidly, since the core 1 is then effectively screened by the sleeve 4- from the radio waves.
  • the improved effect of the antenna according to the invention might be accounted for by the fact that the conductive sleeve reduces the stray flux paths by preventing magnetic lines of force from emanating laterally from the bar. Therefore, the length of these lines of force is, on the average, greater than in the absence of a sleeve, and it follows that a substantially greater percentage of the flux is confined to the bar itself.
  • the coupling winding In order to adjust the antenna impedance to the value of the transmission line impedance, the coupling winding must enclose only a part of the total magnetic flux in the sleeve. This may be achieved by providing the ferrite bar with a transverse saw cut, in which the coupling winding is accommodated.
  • FIG. 3 An advantageous embodiment is shown in FIG. 3, in which the ferrite body 1 consists of two separate portions 7 and 8, separated by an air gap 9, in which the coupling winding or pick-up coil is arranged.
  • This construction has the added advantage that by the axial displacement of the two ferrite portions 7 and 8 relative to each other, the antenna tuning may be varied within given limits.
  • FIG. 4 is a cross sectional view taken along the lines A-B of FIG. 3.
  • a pair of conductors 3 of a symmetrical transmission line are connected to points on the inner wall of the sheath 4.
  • the cross-hatchedpart in the figure indicates the flux enclosed by the coupling winding and by enlarging or reducing this part the antenna impedance can be adjusted to any desired value within limits.
  • FIG. 4 also shows how the tuning capacitance 5 may be formed by curved, opposite parts of the sheath 4. This construction has the advantage that it eliminates the need of a plurality of individual capacitors as shown in FIG. 1.
  • a particular advantage of the antenna according to the invention consists in the possibility of using an asymmetrical transmission line for coupling the antenna to the :receiver.
  • the outer sheath of a coaxial transmission line is connected to the sleeve 4 at a point lying diametrically opposite the longitudinal gap 5.
  • the inner conductor 11 is connected to a point at the inner wall of the sleeve 4.
  • the antenna impedance can be varied by varying the volume enclosed by inner conductor 11.
  • the tuning capacitance may also be formed by overlapping parts 12 and 13 of the sleeve 4, as shown in FIG 5.
  • the supply conductors of the coupling winding may be taken out of the sleeve not only laterally, but also through an axial hole in the ferrite bar.
  • a magnetic antenna for use over a predetermined radio frequency band comprising an elongated body of ferromagnetic material, a coupling winding mounted in magnetic coupling arrangement with said body, a sleeve of electrically conductive material having a longitudinal gap and arranged to surround said coupling winding and a substantial portion of said body, and means providing a tuning capacitance between the edges of said longitudinal gap.
  • a magnetic antenna for use with radio signals of a predetermined band of frequencies comprising a relatively thin elongated body of ferromagnetic material, a coupling winding mounted in magnetic coupling arrangement with said body, a sleeve of electrically conductive material having a longitudinal gap and arranged to surround said coupling winding and a portion of said body, and means providing a tuning capacitance distributed throughout the length of said gap and forming a resonant circuit with the inductance of said sleeve tuned to a given frequency within said band of signal frequencies.
  • a magnetic antenna for use over a given radio frequency band comprising a thin cylindrical body of ferromagnetic material, a coupling winding mounted in magnetic coupling arrangement with said body, a sleeve of electrically conductive material having a longitudinal gap and arranged to surround said coupling winding and a portion of said body, the length of said sleeve being between 65 and 90% Of the length of said cylindrical body,
  • a magnetic antenna comprising a thin cylindrical body of ferromagnetic material, the length of said body being at least five times its diameter, a coupling winding mounted in magnetic coupling arrangement with said body, a sleeve of electrically conductive material having a longitudinal gap and arranged to surround said coupling winding and a portion of said body, the length of said sleeve being between and of the length of said cylindrical body, and means providing a tuning capacitance between the edges of said longitudinal gap which forms a resonant circuit with the inductance of said sleeve.
  • said tuning capacitance means comprises a plurality of capacitors uniformly spaced along the length of said gap and connecting the opposed edges of said longitudinal gap so as to form a tuning capacitance uniformly distributed over the length of said gap.
  • said sleeve further comprises outwardly fianging edges along said longitudinal gap, said fianging edges coacting to form a substantially uniformly distributed tuning capacitance.
  • a magnetic antenna comprising a relatively thin elongated body of ferromagnetic material having a transverse air gap located therein, a coupling winding mounted in said air gap in magnetic coupling arrangement with said ferromagnetic body, a sleeve of electrically conductive material having a longitudinal gap and arranged to surround said coupling Winding and a portion of said body, and means providing a capacitance between the edges of said sleeve gap which forms a resonant circuit with the inductance of said sleeve.
  • a magnetic antenna for use over a given radio frequency band comprising a relatively thin cylindrical body of ferromagnetic material having a transverse air gap located therein, a coupling winding mounted in said air gap in magnetic coupling arrangement with said ferromagnetic body, a sleeve of electrically conductive material having a longitudinal gap and arranged to surround said coupling winding and a portion of said body, the length of said sleeve being between 65% and 90% of the length of said cylindrical body, and a tuning capacitance distributed throughout the length of the sleeve gap which forms a resonant circuit with the inductance of said sleeve which is tuned to a given frequency within said radio frequency and.
  • a magnetic antenna comprising a relatively thin cylindrical body of ferromagnetic material having a transverse air gap located therein, a coupling winding mounted in said air gap in magnetic coupling arrangement with said ferromagnetic body, said coupling winding comprising a single turn of electrically conductive wire having a cross sectional area enclosed by said turn which is less than the cross sectional area of said cylindrical body, a sleeve of electrically conductive material having a longitudinal gap and arranged to surround said coupling wind ing and a portion of said body, and a tuning capacitance distributed throughout the length of said sleeve gap which forms a resonant circuit with the inductance of said sleeve.
  • a magnetic antenna for use over a given radio frequency band comprising a pair of relatively thin cylindrical bodies of ferromagnetic material, said bodies being axially aligned and spaced apart to form an air gap therebetween, eenrgy coupling means mounted in magnetic coupling arrangement with at least one of said ferromagnetic bodies, a sleeve of electrically conductive material having a longitudinal gap therein and arranged to su r-.
  • said tuning capacitance forms a resonant circuit with the sleeve inductance which is tuned to a given frequency within said radio frequency band and wherein at least one of said ferromagnetic bodies is axially movable so that the antenna tuning can be varied.
  • said energy coupling means comprises a pair of electrical conductors connected to internal points on said sleeve so as to form a closed circuit with a portion of said sleeve, said closed circuit enclosing a portion of the total magnetic flux within the sleeve.
  • a magnetic antenna comprising a pair of relatively thin cylindrical bodies of ferromagnetic material, said bodies being axially aligned and spaced apart to form an air gap therebetween, energy coupling means mounted in magnetic coupling arrangement with at least one of said ferromagnetic bodies, a sleeve of electrically conductive material having a longitudinal gap therein and arranged to surround a portion of said bodies, said energy coupling means comprising a coaxial transmission line having inner and outer conductors, said outer conductor being connected approximately to the midpoint along the length of said sleeve and diametrically opposite the longitudinal gap in said sleeve, said inner conductor being connected to a point on the inner wall of said sleeve so as to form a loop with a portion of said sleeve wall, said loop enclosing a portion only of the total magnetic lines of force enclosed by said sleeve, and means providing a capacitance between the edges of said sleeve gap which forms a resonant circuit with the

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  • Coils Or Transformers For Communication (AREA)
  • Dynamo-Electric Clutches, Dynamo-Electric Brakes (AREA)
US252400A 1962-01-19 1963-01-18 Tunable ferromagnetic rod loop antenna Expired - Lifetime US3267478A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL273756 1962-01-19

Publications (1)

Publication Number Publication Date
US3267478A true US3267478A (en) 1966-08-16

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Family Applications (1)

Application Number Title Priority Date Filing Date
US252400A Expired - Lifetime US3267478A (en) 1962-01-19 1963-01-18 Tunable ferromagnetic rod loop antenna

Country Status (8)

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US (1) US3267478A (es)
AT (1) AT239863B (es)
BE (1) BE627249A (es)
DE (1) DE1287169B (es)
DK (1) DK103897C (es)
ES (1) ES284243A1 (es)
GB (1) GB1010311A (es)
NL (1) NL273756A (es)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3453634A (en) * 1966-05-17 1969-07-01 Dictaphone Corp Loopstick antennas
US3594805A (en) * 1968-03-25 1971-07-20 Pye Ltd Ferrite rod antenna with longitudinally split sleeve
US5014071A (en) * 1989-06-30 1991-05-07 Motorola, Inc. Ferrite rod antenna
US5164737A (en) * 1991-03-28 1992-11-17 Motorola, Inc. Single turn ferrite rod antenna with mounting structure
US20130169398A1 (en) * 2010-12-01 2013-07-04 Dexerials Corporation Antenna device and communication device
CN103427152A (zh) * 2013-05-15 2013-12-04 贵州泰格科技有限责任公司 一种可调电感量的谐振天线

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4407000A (en) * 1981-06-25 1983-09-27 Tdk Electronics Co., Ltd. Combined dipole and ferrite antenna

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2611867A (en) * 1946-08-31 1952-09-23 Alford Andrew Slotted winged cylindrical antenna
FR1141361A (fr) * 1954-08-31 1957-09-02 Perfectionnements au collecteur d'ondes
US2821708A (en) * 1954-06-01 1958-01-28 Bendix Aviat Corp Coupling connection for slot antenna
US2983919A (en) * 1957-10-16 1961-05-09 Rca Corp Tuning means for slot radiator

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE515657A (es) * 1951-11-23
DE1046697B (de) * 1953-09-26 1958-12-18 Heinrich Scheller Dr Ing Rahmenantenne mit stabfoermigem Kern
DE1713820U (de) * 1955-09-07 1955-12-29 Heinrich Pfitzner Ferritstabantenne.

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2611867A (en) * 1946-08-31 1952-09-23 Alford Andrew Slotted winged cylindrical antenna
US2821708A (en) * 1954-06-01 1958-01-28 Bendix Aviat Corp Coupling connection for slot antenna
FR1141361A (fr) * 1954-08-31 1957-09-02 Perfectionnements au collecteur d'ondes
US2983919A (en) * 1957-10-16 1961-05-09 Rca Corp Tuning means for slot radiator

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3453634A (en) * 1966-05-17 1969-07-01 Dictaphone Corp Loopstick antennas
US3594805A (en) * 1968-03-25 1971-07-20 Pye Ltd Ferrite rod antenna with longitudinally split sleeve
US5014071A (en) * 1989-06-30 1991-05-07 Motorola, Inc. Ferrite rod antenna
US5164737A (en) * 1991-03-28 1992-11-17 Motorola, Inc. Single turn ferrite rod antenna with mounting structure
US20130169398A1 (en) * 2010-12-01 2013-07-04 Dexerials Corporation Antenna device and communication device
US9082545B2 (en) * 2010-12-01 2015-07-14 Dexerials Corporation Antenna device and communication device
CN103427152A (zh) * 2013-05-15 2013-12-04 贵州泰格科技有限责任公司 一种可调电感量的谐振天线
CN103427152B (zh) * 2013-05-15 2016-02-17 贵州泰格科技有限责任公司 一种可调电感量的谐振天线

Also Published As

Publication number Publication date
GB1010311A (en) 1965-11-17
BE627249A (es)
NL273756A (es)
AT239863B (de) 1965-04-26
DK103897C (da) 1966-03-07
ES284243A1 (es) 1963-03-16
DE1287169B (de) 1969-01-16

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