US3594805A - Ferrite rod antenna with longitudinally split sleeve - Google Patents
Ferrite rod antenna with longitudinally split sleeve Download PDFInfo
- Publication number
- US3594805A US3594805A US807277A US3594805DA US3594805A US 3594805 A US3594805 A US 3594805A US 807277 A US807277 A US 807277A US 3594805D A US3594805D A US 3594805DA US 3594805 A US3594805 A US 3594805A
- Authority
- US
- United States
- Prior art keywords
- sleeve
- aerial
- split
- aperture
- conducting material
- 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
Links
- 229910000859 α-Fe Inorganic materials 0.000 title claims abstract description 22
- 239000004020 conductor Substances 0.000 claims abstract description 16
- 239000003990 capacitor Substances 0.000 claims description 27
- 230000008878 coupling Effects 0.000 claims description 7
- 238000010168 coupling process Methods 0.000 claims description 7
- 238000005859 coupling reaction Methods 0.000 claims description 7
- DMFGNRRURHSENX-UHFFFAOYSA-N beryllium copper Chemical compound [Be].[Cu] DMFGNRRURHSENX-UHFFFAOYSA-N 0.000 claims description 3
- 239000000463 material Substances 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 230000004323 axial length Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000009966 trimming Methods 0.000 description 1
Images
Classifications
-
- 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
- This invention relates to aerials comprising a ferrite rod disposed within a longitudinally split sleeve of elec- [52] US. Cl l. 343/746, trically conducting material and where a substantially uniform 343/787, 343/788 capacitance exists or is provided across the split. According to [5]] Int.
- the resonant frequency of the aerial can be ad- [50] Field of Search 343/787, justed by varying the inductance of the split sleeve disposed 788, 746, 748, 908 around the ferrite rod.
- the invention is particularly concerned with such aerials in which a ferrite rod is disposed within a longitudinally split 0 sleeve of electrically conducting material and where a substantially uniform capacitance exists or is provided across the split, which in conjunction with the inductance of the sleeve causes the aerial to be resonant at a required operating frequency.
- the invention provides a magnetic dipole aerial employing a ferrite rod wherein the resonant frequency of the aerial can be adjusted by varying the inductance of a split sleeve of electrically conducting material disposed around said ferrite rod.
- the invention provides a magnetic dipole aerial comprising a ferrite rod, a longitudinally split sleeve of electrically conducting material disposed around said rod over port of its length, an aperture in said sleeve, and a member of electrically conducting material in contact with the external surface of said sleeve and movable so as to cover or uncover said aperture.
- the aperture is a slot extending longitudinally of the sleeve over part of its length.
- the member may advantageously be a further sleeve which is axially slidable on the external surface of the split sleeve between positions in which it covers or uncovers the slot.
- the slot extends for about one-third of the axial length of the split sleeve, and the further sleeve is slightly longer.
- the member such as the further sleeve, may be provided with a projection to facilitate its adjustment relative to the slot or other aperture in the split sleeve.
- substantially uniformly distributed capacitance is provided across the split in the sleeve by connecting capacitor means of effectively equal capacity across the split at spaced points.
- the coupling to the aerial is effected in a capacitive manner by fonning one of the capacitor means connected across the split in the sleeve from at least two serially connected capacitors whose effective capacity is equal to that of the other capacitor means connected across the split and connecting the leads to the aerial across one of the serially connected capacitors.
- the serially connected capacitors are also of such relative values as to provide a required power match of the aerial to a load.
- F IG. 1 is a plan view of one embodiment of aerial according to one embodiment according to the invention, looking in the direction of the split in the sleeve.
- FIG. 3 illustrates a method of providing coupling to the aerial of FIG. ll.
- FlGS. l and 2 show, not to scale, an embodiment of a magnetic dipole aerial intended, for example, for use over a frequency range of approximately 142 to 152 Megacycles.
- the aerial assembly comprises a ferrite rod ll, embraced for a major part of its length by an electrically conductive cylindri' cal sleeve 2 having a longitudinal split defining a gap 3 throughout its length.
- the opposite edges of the gap 3 are capacitively connected to each other by a plurality of capacitors, such as Cll, C4 and serially connected capacitors C2 and C3, uniformly distributed over a length of the sleeve 2.
- the capacitors may be connected directly to the sleeve 2, or, as shown, be attached to lugs d formed from turned up projections at the edge of the gap 3.
- a split electrically conductive sleeve 5 of a length less than one-half the length of the sleeve 2 and slightly greater than a longitudinal slot 6 in the sleeve 2, the length of slot 6 being about one-third of the length of the cylinder 2.
- the slot 6 is diametrically opposite the gap 3, though its position is not critical. The effect of the slot is to increase the inductance of the sleeve 2.
- Minimum inductance is obtained when the slot 6 is completely masked by the sleeve 5 and maximum inductance is obtained with slot 6 completely exposed, i.e. uncovered by the sleeve 5.
- all the bridging capacitors should be approximately equal, i.e. the efiective capacity of serially connected capacitors C2 and C3 at the center of the gap 3 should be substantially equal to that of the other capacitors bridging the gap.
- the size of aerial involved at the relevant midfrequency of 147 Megacycles it has been found that capacitance provided at three points, i.e. at the center and near. each end, is adequate.
- Capacitors C2 and C3 are of such value as not only to provide an effective capacitance equal to that of each of capacitors Cl and C4 but also to provide a substantially 0ptimum power match of the aerial to a load.
- the sleeve 2 and the sleeve 5 are made from a material such as beryllium copper and preformed so that sleeve 2 firmly grips the ferrite rod 1 and the sleeve 5 is a spring fit on the sleeve 2 to give good electrical contact therewith.
- both the sleeve 2 and the sleeve 5 are preferably silver plated.
- the sleeve 2 may be locked in position on the ferrite rod 1 by known means, such as a sealing glue, as may the sleeve 5 on the sleeve 2, after adjustment of the sleeve 5 as a trimming operation, e.g. in setting up a receiver operating on a fixed frequency.
- the slot 6 is 0.7 inches long, the cylindrical sleeve 2 is 1.8 inches long and the rod 1 has a length of 2.2 inches. Movement of the sleeve 5 provides about l4 percent change in inductance and a turning range of fi Megacycles on a center frequency of 147 Megacycles. The range of adjustment of inductance with slot length is nearly linear, but the mean position lies slightly short of half the slot length from the inner closed end of the slot. For maximum control it is desirable to fit the capacitors C1 and C4 as near to the ends of the sleeve 2 as is possible.
- a mechanically strong assembly as only a single ferrite rod is used with no break at the center and the rod is supported throughout the majority of its length by the conductive split sleeve.
- a magnetic dipole aerial comprising a ferrite rod, a split sleeve of electrically conducting material disposed around said ferrite rod, an aperture in said sleeve and a member of electrically conducting material movable to cover or uncover said aperture, thereby to vary the inductance of said split sleeve to adjust the resonant frequency of the aerial.
- a magnetic dipole aerial comprising a ferrite rod, a low gitudinally split sleeve of electrically conducting material disposed around said rod over part of its length, an aperture in said sleeve, and a member of electrically conducting material in contact with the external surface of said sleeve and movable so as to cover or uncover said aperture.
Abstract
This invention relates to aerials comprising a ferrite rod disposed within a longitudinally split sleeve of electrically conducting material and where a substantially uniform capacitance exists or is provided across the split. According to this invention the resonant frequency of the aerial can be adjusted by varying the inductance of the split sleeve disposed around the ferrite rod.
Description
United States Patent 1 1 3,594,805
[72] Inventor Eric G. Chardin [56] References Cited A I N j g England UNITED STATES PATENTS P 3 3,267,478 8/1966 Schiefer '1 343/788 [221 Flcd 3 453 634 7/1969 G'lb n 343 788 45 Patented July 20,1971 e [73] A5991 E sl fi E and Primary Examiner-Eli Lieberman get At! -H I be, W th 'll & B bo' 1321 Priority Mar. 25, I968 0 com 6 [3 3] Great Britain [3 l [4,347/68 [54] FERRITE ROD ANTENNA WITH P;% F' P SLEEVE ABSTRACT: This invention relates to aerials comprising a ferrite rod disposed within a longitudinally split sleeve of elec- [52] US. Cl l. 343/746, trically conducting material and where a substantially uniform 343/787, 343/788 capacitance exists or is provided across the split. According to [5]] Int. Cl H0lq 7/08 this invention the resonant frequency of the aerial can be ad- [50] Field of Search 343/787, justed by varying the inductance of the split sleeve disposed 788, 746, 748, 908 around the ferrite rod.
FERRITE ROD ANTENNA Wl'llllll LONGHTUDHNALLY SPLllT SLEEVE The invention is particularly concerned with such aerials in which a ferrite rod is disposed within a longitudinally split 0 sleeve of electrically conducting material and where a substantially uniform capacitance exists or is provided across the split, which in conjunction with the inductance of the sleeve causes the aerial to be resonant at a required operating frequency.
From one aspect the invention provides a magnetic dipole aerial employing a ferrite rod wherein the resonant frequency of the aerial can be adjusted by varying the inductance of a split sleeve of electrically conducting material disposed around said ferrite rod.
From another aspect the invention provides a magnetic dipole aerial comprising a ferrite rod, a longitudinally split sleeve of electrically conducting material disposed around said rod over port of its length, an aperture in said sleeve, and a member of electrically conducting material in contact with the external surface of said sleeve and movable so as to cover or uncover said aperture.
Preferably the aperture is a slot extending longitudinally of the sleeve over part of its length. The member may advantageously be a further sleeve which is axially slidable on the external surface of the split sleeve between positions in which it covers or uncovers the slot.
Advantageously the slot extends for about one-third of the axial length of the split sleeve, and the further sleeve is slightly longer.
The member, such as the further sleeve, may be provided with a projection to facilitate its adjustment relative to the slot or other aperture in the split sleeve.
According to a feature of the invention, substantially uniformly distributed capacitance is provided across the split in the sleeve by connecting capacitor means of effectively equal capacity across the split at spaced points.
According to a further feature of the invention, the coupling to the aerial is effected in a capacitive manner by fonning one of the capacitor means connected across the split in the sleeve from at least two serially connected capacitors whose effective capacity is equal to that of the other capacitor means connected across the split and connecting the leads to the aerial across one of the serially connected capacitors. The serially connected capacitors are also of such relative values as to provide a required power match of the aerial to a load.
The invention will now be further described, by way of example, with reference to the accompanying drawings, in which:
F IG. 1 is a plan view of one embodiment of aerial according to one embodiment according to the invention, looking in the direction of the split in the sleeve.
FIG. 2 is a plan view of the aerial of FIG. 1, looking in a diametrically opposite direction, and
FIG. 3 illustrates a method of providing coupling to the aerial of FIG. ll.
FlGS. l and 2 show, not to scale, an embodiment of a magnetic dipole aerial intended, for example, for use over a frequency range of approximately 142 to 152 Megacycles. The aerial assembly comprises a ferrite rod ll, embraced for a major part of its length by an electrically conductive cylindri' cal sleeve 2 having a longitudinal split defining a gap 3 throughout its length. The opposite edges of the gap 3 are capacitively connected to each other by a plurality of capacitors, such as Cll, C4 and serially connected capacitors C2 and C3, uniformly distributed over a length of the sleeve 2. The capacitors may be connected directly to the sleeve 2, or, as shown, be attached to lugs d formed from turned up projections at the edge of the gap 3. Partially surrounding the cylinder 2, and a sliding fit thereon, is a split electrically conductive sleeve 5 of a length less than one-half the length of the sleeve 2 and slightly greater than a longitudinal slot 6 in the sleeve 2, the length of slot 6 being about one-third of the length of the cylinder 2. As shown the slot 6 is diametrically opposite the gap 3, though its position is not critical. The effect of the slot is to increase the inductance of the sleeve 2. A tab 7, either attached to or formed from the sleeve 5, is utilized to move the sleeve 5 axially, so as to adjust the inductance of the sleeve 2. Minimum inductance is obtained when the slot 6 is completely masked by the sleeve 5 and maximum inductance is obtained with slot 6 completely exposed, i.e. uncovered by the sleeve 5.
To maintain equal distribution of capacitance along the gap 3 in the sleeve 2, all the bridging capacitors should be approximately equal, i.e. the efiective capacity of serially connected capacitors C2 and C3 at the center of the gap 3 should be substantially equal to that of the other capacitors bridging the gap. With the size of aerial involved, at the relevant midfrequency of 147 Megacycles it has been found that capacitance provided at three points, i.e. at the center and near. each end, is adequate.
The outer surface of the sleeve 2 tends to be electrically dead and a tapping on the inductance of the cylinder is therefore not effective as a coupling means to the aerial. The coupling to the aerial is therefore made capacitive, as illustrated in FIG. 3, which shows the cylindrical sleeve 2, gap 3 and capacitors Cl to C4, with leads and 9 being taken from each terminal of capacitor C3 to form the connections for the aerial. Capacitors C2 and C3 are of such value as not only to provide an effective capacitance equal to that of each of capacitors Cl and C4 but also to provide a substantially 0ptimum power match of the aerial to a load.
Preferably the sleeve 2 and the sleeve 5 are made from a material such as beryllium copper and preformed so that sleeve 2 firmly grips the ferrite rod 1 and the sleeve 5 is a spring fit on the sleeve 2 to give good electrical contact therewith. In order to obtain a high Q factor when using such material, both the sleeve 2 and the sleeve 5 are preferably silver plated.
The sleeve 2 may be locked in position on the ferrite rod 1 by known means, such as a sealing glue, as may the sleeve 5 on the sleeve 2, after adjustment of the sleeve 5 as a trimming operation, e.g. in setting up a receiver operating on a fixed frequency.
In the embodiment described the slot 6 is 0.7 inches long, the cylindrical sleeve 2 is 1.8 inches long and the rod 1 has a length of 2.2 inches. Movement of the sleeve 5 provides about l4 percent change in inductance and a turning range of fi Megacycles on a center frequency of 147 Megacycles. The range of adjustment of inductance with slot length is nearly linear, but the mean position lies slightly short of half the slot length from the inner closed end of the slot. For maximum control it is desirable to fit the capacitors C1 and C4 as near to the ends of the sleeve 2 as is possible.
The aerial as described provides the following advantages:
1. Reduced material cost as only one accurately ground ferrite rod is required, whereas previous constructions require two such rods.
2. Easier assembly due to discarding the internal coupling loop, used in prior constructions.
3. Provision of a simple and cheap means of adjustment that requires little space.
4. A mechanically strong assembly as only a single ferrite rod is used with no break at the center and the rod is supported throughout the majority of its length by the conductive split sleeve.
The ability to vary the inductance of the aerial and hence its resonant frequency with little increase in overall size is of particular advantage in small portable radio sets designed to be carried unobtrusively on the person.
Tests on about Megacycles have shown that an aerial as described using a ferrite rod 2.2 inches long and of 0.3 inches diameter is of the order of 16 db. down in performance on a half wave dipole aerial about 36 inches in length. This degradation is offset to some extent in practice by the fact that the high Q of the magnetic aerial enables a tuned circuit employed with a dipole or quarter wave aerial to be dispensed with, so removing the insertion loss of the circuit. Also, due in part to the outer surface of the split sleeve being electrically dead the resonant frequency of the aerial is not materially affected by proximity to an object, such as the human body, as is the case for a half or quarter wave rod aerial. This characteristic is particularly important for radio sets carried on the person.
lclaim:
1. A magnetic dipole aerial comprising a ferrite rod, a split sleeve of electrically conducting material disposed around said ferrite rod, an aperture in said sleeve and a member of electrically conducting material movable to cover or uncover said aperture, thereby to vary the inductance of said split sleeve to adjust the resonant frequency of the aerial.
2. A magnetic dipole aerial comprising a ferrite rod, a low gitudinally split sleeve of electrically conducting material disposed around said rod over part of its length, an aperture in said sleeve, and a member of electrically conducting material in contact with the external surface of said sleeve and movable so as to cover or uncover said aperture.
3. An aerial as claimed in claim 2, wherein the aperture is a slot extending longitudinally of the sleeve over part of its length.
4. An aerial as claim in claim 2, wherein the member is a further sleeve which is axially slidable on the external surface of the split sleeve between a position in which it covers the aperture and a position in which it uncovers the aperture.
5. An aerial as claimed in claim 2, wherein substantially uniformly distributed capacitance is provided across the split in the sleeve by connecting capacitor means of effectively equal capacity across the split at spaced points along the sleeve.
6. An aerial as claimed in claim 5, wherein the coupling to the aerial is effected in a capacitive manner by forming one of the capacitor means connected across the split in the sleeve from at least two serially connected capacitors whose effective capacity is equal to that of the other capacitor means connected across the split and means connecting the leads to the aerial across one of the serially connected capacitors.
7. An aerial as claimed in claim 2, wherein the split sleeve and the member of electrically conducting material are made of beryllium copper.
Claims (7)
1. A magnetic dipole aerial comprising a ferrite rod, a split sleeve of electrically conducting material disposed around said ferrite rod, an aperture in said sleeve and a member of electrically conducting material movable to cover or uncover said aperture, thereby to vary the inductance of said split sleeve to adjust the resonant frequency of the aerial.
2. A magnetic dipole aerial comprising a ferrite rod, a longitudinally split sleeve of electrically conducting material disposed around said rod over part of its length, an aperture in said sleeve, and a member of electrically conducting material in contact with the external surface of said sleeve and movable so as to cover or uncover said aperture.
3. An aerial as claimed in claim 2, wherein the aperture is a slot extending longitudinally of the sleeve over part of its length.
4. An aerial as claim in claim 2, wherein the member is a further sleeve which is axially slidable on the external surface of the split sleeve between a position in which it covers the aperture and a position in which it uncovers the aperture.
5. An aerial as claimed in claim 2, wherein substantially uniformly distributed capacitance is provided across the split in the sleeve by connecting capacitor means of effectively equal capacity across the split at spaced points along the sleeve.
6. An aerial as claimed in claim 5, wherein the coupling to the aerial is effected in a capacitive manner by forming one of the capacitor means connected across the split in the sleeve from at least two serially connected capacitors whose effective capacity is equal to that of the other capacitor means connected across the split and means connecting the leads to the aerial across one of the serially connected capacitors.
7. An aerial as claimed in claim 2, wherein the split sleeve and the member of electrically conducting material are made of beryllium copper.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB04347/68A GB1207595A (en) | 1968-03-25 | 1968-03-25 | Aerials |
Publications (1)
Publication Number | Publication Date |
---|---|
US3594805A true US3594805A (en) | 1971-07-20 |
Family
ID=10039562
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US807277A Expired - Lifetime US3594805A (en) | 1968-03-25 | 1969-03-14 | Ferrite rod antenna with longitudinally split sleeve |
Country Status (3)
Country | Link |
---|---|
US (1) | US3594805A (en) |
GB (1) | GB1207595A (en) |
NL (1) | NL6904565A (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4367475A (en) * | 1979-10-30 | 1983-01-04 | Ball Corporation | Linearly polarized r.f. radiating slot |
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 |
US5561438A (en) * | 1991-11-13 | 1996-10-01 | Seiko Epson Corporation | Ferrite Antenna |
US6861992B2 (en) * | 2000-09-28 | 2005-03-01 | Hitachi Kokusai Electric Inc. | Antenna |
US20110139877A1 (en) * | 2009-12-14 | 2011-06-16 | Szakelyhidi David C | Radio Frequency Identification Tag for Use on Metal Objects |
US8350695B2 (en) | 2010-06-24 | 2013-01-08 | Lojack Operating Company, Lp | Body coupled antenna system and personal locator unit utilizing same |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2117182B (en) * | 1982-03-23 | 1985-07-31 | Multitone Electronics Plc | Aerial arrangements |
FR2707124B1 (en) * | 1993-07-01 | 1995-09-08 | Telediffusion Fse | Ferrite antenna for portable receiver. |
FR2721756B1 (en) * | 1994-06-24 | 1996-08-23 | Telediffusion Fse | Omnidirectional transmitting and receiving antenna system with angular diversity and polarization. |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3267478A (en) * | 1962-01-19 | 1966-08-16 | Philips Corp | Tunable ferromagnetic rod loop antenna |
US3453634A (en) * | 1966-05-17 | 1969-07-01 | Dictaphone Corp | Loopstick antennas |
-
1968
- 1968-03-25 GB GB04347/68A patent/GB1207595A/en not_active Expired
-
1969
- 1969-03-14 US US807277A patent/US3594805A/en not_active Expired - Lifetime
- 1969-03-25 NL NL6904565A patent/NL6904565A/xx unknown
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3267478A (en) * | 1962-01-19 | 1966-08-16 | Philips Corp | Tunable ferromagnetic rod loop antenna |
US3453634A (en) * | 1966-05-17 | 1969-07-01 | Dictaphone Corp | Loopstick antennas |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4367475A (en) * | 1979-10-30 | 1983-01-04 | Ball Corporation | Linearly polarized r.f. radiating slot |
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 |
US5561438A (en) * | 1991-11-13 | 1996-10-01 | Seiko Epson Corporation | Ferrite Antenna |
US6861992B2 (en) * | 2000-09-28 | 2005-03-01 | Hitachi Kokusai Electric Inc. | Antenna |
US20110139877A1 (en) * | 2009-12-14 | 2011-06-16 | Szakelyhidi David C | Radio Frequency Identification Tag for Use on Metal Objects |
US8350695B2 (en) | 2010-06-24 | 2013-01-08 | Lojack Operating Company, Lp | Body coupled antenna system and personal locator unit utilizing same |
Also Published As
Publication number | Publication date |
---|---|
NL6904565A (en) | 1969-09-29 |
GB1207595A (en) | 1970-10-07 |
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