CA2189239A1 - Antenna device and mobile telephone - Google Patents
Antenna device and mobile telephoneInfo
- Publication number
- CA2189239A1 CA2189239A1 CA002189239A CA2189239A CA2189239A1 CA 2189239 A1 CA2189239 A1 CA 2189239A1 CA 002189239 A CA002189239 A CA 002189239A CA 2189239 A CA2189239 A CA 2189239A CA 2189239 A1 CA2189239 A1 CA 2189239A1
- Authority
- CA
- Canada
- Prior art keywords
- loop
- antenna
- ground plane
- antenna according
- transmission line
- 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.)
- Abandoned
Links
Classifications
-
- 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
-
- 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
Landscapes
- Details Of Aerials (AREA)
- Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)
- Telephone Function (AREA)
- Support Of Aerials (AREA)
Abstract
An antenna comprises a closed loop (1) spaced above a ground plane (2). Two connec-tion points (10, 11) spaced around the loop (1) are provided for coupling to a transmission line (5). The loop (1) may have one or more extra conductive portions (11, 15, 16, 19) joined to it to alter its characteristics. The antenna is par-ticularly suitable for use in mobile telephones at frequencies of the order of 800 MHz - 900 MHz, in which application the antenna may be mounted to provide directional transmission of power away from the user. The loop may be formed on a printed circuit board.
Description
WO95130253 21 89239 E~JI~~I~ ''I
AN~INA DEVICE ~) MOBILE T~!T~T~T~IONE
The present invention relates to an antenna device for use in radio frequency communication. The antenna device of the preElent invention is particularly 5 suitable for use at higher frequencies, such as those employed in mobile t~l Prhnn~, but may be used for lower frequencies as well. The present invention also relates to a mobile telephone in~:uL~uL~ting sn i uve:d antenna .
In the prior art, a large variety of antenna systems have been employed, depending on the LLe~uell-,y employed, and the physical constraints on the antenna.
For low frequencies, a long wire or dipole is often used .
There is also known, for uge at low fre5luF~n~;Pc~
an open-loop aerial, as depicted in Fig. la in which an open loop of wire is spaced from a ground plane by insulators, with one end being capacitively tuned to ground, and the signal fed at a tap close to the other 20 end, which is shorted to ground. The circumference of the loop i5 apprn~ t-ol y one quarter of the wavelength of the signal to be transmitted or received.
This suffers from the disadvantage that complex tuning is required to achieve a desired resonant 25 frequency and; ~ '~nre. Furthermore the antenna is bulky due to the large ;nq~ tnrs required to space the antenna from the ground, to prevent breakdown of the air. It ha~ been rl~ffirlllt to use this antenna at frequencies above 100 MHz requiring specialized W095l30253 2 1 8~23~ 2 manufacturing techniques.
Another type of antenna, used f or higher frequencies, such as in portable television receivers, is a simple open-loop aerial, where the loop 5 circumference is approximately equal to the wavelength of the signal. In this case, there i8 no ground plane and the loop is normally mounted with its plane vertical. This is illustrated in Fig. lb.
For use in mobile tPl ~rhnnl-~, where the 10 frequencies are approximately 900 MHz, and the aerial must be compact, a short rubber rod with a helical winding, such as illustrated in Fig. lc, is generally used. Because it is necessary to make such an aerial compact, the aerial usually cannot be an optimum length 15 for the wavelength used, and ig therefore ;nl~ff;r;F~nt, FurthP e, the aerial radiates uniformly, 80 in a mobile telephone an appreciable amount of energy goes directly into the user.
The present invention seeks to provide a novel 20 antenna, which can be made compact, can be coupled to a variety of tr~nr~ cinn lines, and i9 generally more ef f icient than a conventional antenna of the same Ri nnr, The present invention provides an antenna device 2~ comprising an electrically conductive closed loop spaced above a ground plane, with two rnnn~oct; nn points spaced around the loop for connection to a radio-frequency transmitter or receiver.
Preferably the circumference of the loop is 30 between one half and three quarters of the desired ~ 21 89239 `
.
signal wavelength. Typically, the circumference is set at about five eighths of the wavelength, or less.
However, this may be reduced to about a third or less of the free-space wavelength if a di~ r; r: is positioned 5 between the loop and ground plane. In addition, the size depends on the arrangement used for matching the antenna to a transmission line.
The shape of the loop is preferably substantially circular, but other shapes such as squares, hexagons, 10 triangles etc. may be employed. Furthermore, the shape may be chosen to achieve a desired radiation pattern, e . g . by using irregular shapes .
The loop is preferably planar, with the plane of the loop substantially parallel to the ground plane.
When the transmission line is connecte~ directly to the loop, the two connection points are preferably spaced between 2 . 5 and 90 apart (when ~he loop is a circle~, typically 35 to 50, or about 95. In some circumstances, however, the spacing can be 120 or 20 larger, depending on the arrangement for matching the transmission line to the loop . According to the f irst aspect of the invention, the spacing is 30-150 degrees.
An advantage of the present invention is that the impedance and resonant frequency of the antenna can be 25 adjusted by varying the spacing of the loop from the ground plane, and/or by altering the dielectric material and/or by changing the circumference of ~he loop. This may simplify coupling to a transmission line. The impedance and/or resonant frequency and/or the bandwidth 30 and/or the efficiency can be adjusted by varying the position of the connection points.
A~ t) SllEET
W095/302~3 2189239 r~
The space between the loop and the ground plane could be illed with air, but preferably ;n~ c a dielectric having a higher relative permittivity, and higher breakdown voltage than air. If a dielectric is used, the overall ~ inn~ of the antenna may be reduced relative to the rli ~ n~ of an antenna with an air dielectric . The reduction in size is ~ Qr~n~l~nt on several factors ;n~ ;n~ the velocity factor (relative permittivity) of the dielectric and the ~ n~ of the antenna.
More preferably, the space between loop and the ground plane ;nr~ two r~ ct~;c8 of differing permittivities, and preferably the dielectric with the higher permittivity i5 closer to the loop. The dielectric adjacent the loop preferably has a relative permittivity of at least 2, and may be glass- f ibre board having a permittivity of appr~Y;r-tPly 5.4. The dielectric adjacent the ground plane can be air, which i9 f ound to give good r~ t; ~n ~of ~ n--y . Other dielectrics, such as PTFE or polyamide, having low relative permittivities (preferably less than about 2) may be used.
The overall spacing between the loop and the ground plane can vary, but is preferably made quite small. For use at fr~ n~ from about 800 MHz-1200 MHz, it is preferably less than 1 cm, more preferably less than 5 mm, preferably about 2 to 3.5 mm, ao that a compact aerial can be formed.
The antenna device may be formed on a double-sided printed circuit board, with one side forming the ground plane, the loop being formed on the other side, and the board serving as the dielectric. In this way, a very compact and easy to manufacture antenna device may be f ormed .
More advantageously, the antenna may comprise two pieces of printed circuit board, each comprising a substrate having an upper conductive layer --;nt~;n~
spaced apart and substantially parallel, the upper rrJnfll7rt;ve layer of the u~ L board forming the loop, and the upper rrln~llrt;ve layer of the lower printed circuit board f orming the ground plane . With this aL- _ , the space between the loop and the ground plane includes the substrate of the u~ " Et board and the air between the boards. This aILa-ly ~ is found to give good r~ t;rn efficiency.
Preferably, said two printed circuit boards are -~^;nt~;n~fl spaced apart by at leagt one spacer. This a ,, ~lly allows parameters , such as resonant frequency to be adjusted simply by varying the thickness of said at least one spacer.
The at least one spacer preferably has a small area, ed to the area of the loop, preferably no more than 109~ of the area of the loop, and preferably is not positioned adj acent a voltage m~ximum point of the loop.
As an alternative to the above argument, a subst~nt;~lly rrntinll~u~ sheet of dielectric of lower permittivity than the substrate of the uppermost board may be used as a spacer, the thickness of the spacer 30 being selected as rer~uired. For example the uppermost W095~302~3 2 1 8~239 I l . ?'~
circuit board may have a glass f ibre substrate, and the sheet may be f ormed f rom PTFE or polyamide . This CLLLCII~ , which does not require air between the boards, may produce a more rigid antenna.
As ~ npA above, the antenna may be formed on a printed circuit board. In addition to substantially rigid substrates, such as glass-fibre or SRBP, a f 1 .oY; hl 1~ gubgtrate, guch as acetate or polyethylene may be used. Such boards are commonly referred to in the art as ~'flOEi-boards", and the term printed circuit board, as used in this sper;f;r~ti~nl is ;ntl~n~ to 1_~' RS all guch variantg; the ~qq-~n~;~l requirement is that the board comprises a rrn~ r~ive ~e.g.
r -t~l 1 i qed) track on an insulating substrate.
If the printed circuit board is f 1 ~'Y; hl~, it may be more readily mounted on a 8urface which possess a degree of curvature, such as a vehicle windscreen.
In a dev~l~ J of the invention, a further loop may be spaced below the ground plane. The further ~0 loop preferably incorporates a resistance, of typically less than 100 S~. This can increase the ratio of the signal given above the ground plane to the signal given below the ground plane- This dev~ L ' of the invention incorporating a loop below the ground plane may be formed on a multi-layer printed circuit board, or on a plurality of spaced boards.
Antenna devices according to the present invention may be used over a very wide range of frequencies, by Relecting the ~1; RirnR appropriately 30 for the frequency employed. However, the antenna Wo95130253 2 l 89239 1 . .
.
device is preferably employed at frequencies above lO0 MHz up to several tens of G~z. Particularly, it may be u3ed at frequencies of around 800-1200 MXz, as used in mobile telephone systems. At such frequencies, the 5 loop may be formed on a first printed circuit board of about 2 mm thickness or less, spaced about 2 mm f rom a second circuit board ~orming the ground plane, the as~embly being about 6 mm thick or less and having sides of about 6 cm or less, to produce a very compact lO antenna.
Another advantage the present invention provides is that a substAnti~lly vertically polarised signal can be generated from a horizontally mounted planar antenna device. The r~ t;nn pattern o~ the hor;7Ont:llly 15 mounted device can be likened to that of a vertically mounted half-wave dipole.
Previously, it has been nPcP~a~ry to have a vertically protruding antenna in order to produce a vertically-polarised signal. This has many 20 disadvantages; for example, when mounted on a vehicle, a protruding aerial is conspicuous, causes a~:lu-ly--~.,.ic drag, and is prone to v~n~
The b~n-lw; ~th o~ the antenna can be altered by altering the thickness of the loop in a radial 25 direction.
According to a development of the invention, additional ron~ rt; ve portions may be attached around the circumference of the loop. These may be poPit;nnPd so as to act as tuned notch filters, to 30 reduce the antenna efficiency at selected frequencies, _ _ _ _ _ _ _ _ _ _ _ _ _, or to tune the antenna to a particular tr~nr-nl Rf~ n line .
The antenna device may be coupled to known tr~nr-r; cc; nn lines, in a variety of ways, a preferable 5 method being to connect an l1nhA 1 ~nred coaxial line directly to the two cnnn~rt; nn points, with the outer ground ~rnnnPctn~ also cnnnPrt~rl to the ground plane.
Alternatively, a h~1~nrpc7 line may simply be rnr1nPCtP~l to the two connection points ~neither of the rnnnPr~; nn 10 points being rnnnPcted directly to the ground plane).
As further alternatives, other known means of feeding an antenna may be used, in particular capacitors and/or inductors may be used to couple the antenna device to a tr~nr"~; cPinn line of a given; - ' .
1~ A preferred aLL"~ly. for coupling the antenna device to a (coaxial) line is to provide a subst~nt;~lly arcuate cnn~ rtn~ stub in the plane of the loop, outside and substantially parallel to a portion of the loop, said conductor stub having a 20 cnnnPct;nn point along its length joined to a first rnnnPrt;nn point of the loop and to the ground plane, the outer rnn~l~1rtnr of the coaxial line being rrnn~rtl~d to an end of said conductor stub, and the centre conductor of said coaxial line being connected to the 25 second connection point of the loop.
The length and th; rknPcs of said conductor stub, its spacing from the loop, and the point of joining to the loop are selected to give the desired; ~ -rP and capacitance to match the loop to the coaxial line at a 30 desired frequency. In additlon, the length of exposed _ _ _ _ _ _ . .
~ W095130253 2 1 ~q239 I~.1 .,,1!'`7''1 central conductor of the transmission line is adjusted to provide a desired reactance for matching the tr~nP~; cq; nn line to the loop . The positions of the conneetion points around the loop are also varied to obtain the desired ; _ - ' re and resonant ~1 e~uell- y .
With this arrangement, the rnnnPct;nn points are pre~erably spaced 60-120 apart. More preferably thê
connection points are apprn~r;r~-tPly goo apart, typically being spaced 70-110 apart. This may make the eharaeteristics of the loop relatively insênsitive to manufacturing tolerances in positioning of the cnnnPct; nn points .
The effective eleetrical length of the loop may be altered (shortened) by forming a short eircuit from a point on the loop to a portion of the rnnrlllrtr~ stub.
I~ the loop is formed on a printed circuit board, the conductor stub may adv~nt~r,Pn~cl y be formed on the same board.
Adv~nt~r,Pn1~qly, the tr~nr~;qq;nn line (e.g.
eoaxial eable) is cnnnPctPd (e.g. soldered) direetly to the surfaee of the loop. This avoids the need for extra rnnA11rt; ve portions around the loop which may alter its characteristies, and allows the position of the connection points to be adjusted relatively easily.
Acrording to a development of the invention, means ean be provided for varying the length of the eleetrieally eonduetive loop. T-ypically, this can be achieved by providing a non-closed loop, in which each end is connected to a joining portion comprising a 30 rnnrlllrt;ve part. The two conductive parts, optionally wog~o~ - 2 1 8 9 2 3 9 1 , subst~nt;~l ly parallel, may be joined at any of a number of places along their length, so that the total length of conductive loop is varied.
~Pn~r:llly, the r~c;ctAnre of the electrically 5 r~nAIlrt; ve cloged loop is made low, typically less than 1 ~2. This reduces resistance losses, and increases the Q f actor of the antenna . ~owever, according to another dev.-l ~, , the resistance of the loop can be increased, typically by inserting a resistor (of typically from 300 Q - 600 Q) in the loop at a joining portion, to produce a wide band antenna device, having a low Q.
According to a further development of the invention, one or more conductive loops which are 15 either greater in circumference, or (more typically) smaller in circumference than the loop of the basic antenna device may be employed. These may be co-planar with the basic antenna loop (if that loop is itself planar), or may be located above the baaic loop, or 20 more typically between the basic loop and the ground plane. These can act to alter the directional pattern of the r~A;~t;rn, and can be used to achieve greater gain or directivity.
Pref erably, where the basic antenna device is 25 formed as a loop on a printed circuit board, the additional loop or loops may be formed on the same surf ace as the basic antenna loop .
According to another aspect of the invention, one or more capacitors can be inserted in the loop 30 (connected in series). This allows a wider bandwidth ..... ...
AN~INA DEVICE ~) MOBILE T~!T~T~T~IONE
The present invention relates to an antenna device for use in radio frequency communication. The antenna device of the preElent invention is particularly 5 suitable for use at higher frequencies, such as those employed in mobile t~l Prhnn~, but may be used for lower frequencies as well. The present invention also relates to a mobile telephone in~:uL~uL~ting sn i uve:d antenna .
In the prior art, a large variety of antenna systems have been employed, depending on the LLe~uell-,y employed, and the physical constraints on the antenna.
For low frequencies, a long wire or dipole is often used .
There is also known, for uge at low fre5luF~n~;Pc~
an open-loop aerial, as depicted in Fig. la in which an open loop of wire is spaced from a ground plane by insulators, with one end being capacitively tuned to ground, and the signal fed at a tap close to the other 20 end, which is shorted to ground. The circumference of the loop i5 apprn~ t-ol y one quarter of the wavelength of the signal to be transmitted or received.
This suffers from the disadvantage that complex tuning is required to achieve a desired resonant 25 frequency and; ~ '~nre. Furthermore the antenna is bulky due to the large ;nq~ tnrs required to space the antenna from the ground, to prevent breakdown of the air. It ha~ been rl~ffirlllt to use this antenna at frequencies above 100 MHz requiring specialized W095l30253 2 1 8~23~ 2 manufacturing techniques.
Another type of antenna, used f or higher frequencies, such as in portable television receivers, is a simple open-loop aerial, where the loop 5 circumference is approximately equal to the wavelength of the signal. In this case, there i8 no ground plane and the loop is normally mounted with its plane vertical. This is illustrated in Fig. lb.
For use in mobile tPl ~rhnnl-~, where the 10 frequencies are approximately 900 MHz, and the aerial must be compact, a short rubber rod with a helical winding, such as illustrated in Fig. lc, is generally used. Because it is necessary to make such an aerial compact, the aerial usually cannot be an optimum length 15 for the wavelength used, and ig therefore ;nl~ff;r;F~nt, FurthP e, the aerial radiates uniformly, 80 in a mobile telephone an appreciable amount of energy goes directly into the user.
The present invention seeks to provide a novel 20 antenna, which can be made compact, can be coupled to a variety of tr~nr~ cinn lines, and i9 generally more ef f icient than a conventional antenna of the same Ri nnr, The present invention provides an antenna device 2~ comprising an electrically conductive closed loop spaced above a ground plane, with two rnnn~oct; nn points spaced around the loop for connection to a radio-frequency transmitter or receiver.
Preferably the circumference of the loop is 30 between one half and three quarters of the desired ~ 21 89239 `
.
signal wavelength. Typically, the circumference is set at about five eighths of the wavelength, or less.
However, this may be reduced to about a third or less of the free-space wavelength if a di~ r; r: is positioned 5 between the loop and ground plane. In addition, the size depends on the arrangement used for matching the antenna to a transmission line.
The shape of the loop is preferably substantially circular, but other shapes such as squares, hexagons, 10 triangles etc. may be employed. Furthermore, the shape may be chosen to achieve a desired radiation pattern, e . g . by using irregular shapes .
The loop is preferably planar, with the plane of the loop substantially parallel to the ground plane.
When the transmission line is connecte~ directly to the loop, the two connection points are preferably spaced between 2 . 5 and 90 apart (when ~he loop is a circle~, typically 35 to 50, or about 95. In some circumstances, however, the spacing can be 120 or 20 larger, depending on the arrangement for matching the transmission line to the loop . According to the f irst aspect of the invention, the spacing is 30-150 degrees.
An advantage of the present invention is that the impedance and resonant frequency of the antenna can be 25 adjusted by varying the spacing of the loop from the ground plane, and/or by altering the dielectric material and/or by changing the circumference of ~he loop. This may simplify coupling to a transmission line. The impedance and/or resonant frequency and/or the bandwidth 30 and/or the efficiency can be adjusted by varying the position of the connection points.
A~ t) SllEET
W095/302~3 2189239 r~
The space between the loop and the ground plane could be illed with air, but preferably ;n~ c a dielectric having a higher relative permittivity, and higher breakdown voltage than air. If a dielectric is used, the overall ~ inn~ of the antenna may be reduced relative to the rli ~ n~ of an antenna with an air dielectric . The reduction in size is ~ Qr~n~l~nt on several factors ;n~ ;n~ the velocity factor (relative permittivity) of the dielectric and the ~ n~ of the antenna.
More preferably, the space between loop and the ground plane ;nr~ two r~ ct~;c8 of differing permittivities, and preferably the dielectric with the higher permittivity i5 closer to the loop. The dielectric adjacent the loop preferably has a relative permittivity of at least 2, and may be glass- f ibre board having a permittivity of appr~Y;r-tPly 5.4. The dielectric adjacent the ground plane can be air, which i9 f ound to give good r~ t; ~n ~of ~ n--y . Other dielectrics, such as PTFE or polyamide, having low relative permittivities (preferably less than about 2) may be used.
The overall spacing between the loop and the ground plane can vary, but is preferably made quite small. For use at fr~ n~ from about 800 MHz-1200 MHz, it is preferably less than 1 cm, more preferably less than 5 mm, preferably about 2 to 3.5 mm, ao that a compact aerial can be formed.
The antenna device may be formed on a double-sided printed circuit board, with one side forming the ground plane, the loop being formed on the other side, and the board serving as the dielectric. In this way, a very compact and easy to manufacture antenna device may be f ormed .
More advantageously, the antenna may comprise two pieces of printed circuit board, each comprising a substrate having an upper conductive layer --;nt~;n~
spaced apart and substantially parallel, the upper rrJnfll7rt;ve layer of the u~ L board forming the loop, and the upper rrln~llrt;ve layer of the lower printed circuit board f orming the ground plane . With this aL- _ , the space between the loop and the ground plane includes the substrate of the u~ " Et board and the air between the boards. This aILa-ly ~ is found to give good r~ t;rn efficiency.
Preferably, said two printed circuit boards are -~^;nt~;n~fl spaced apart by at leagt one spacer. This a ,, ~lly allows parameters , such as resonant frequency to be adjusted simply by varying the thickness of said at least one spacer.
The at least one spacer preferably has a small area, ed to the area of the loop, preferably no more than 109~ of the area of the loop, and preferably is not positioned adj acent a voltage m~ximum point of the loop.
As an alternative to the above argument, a subst~nt;~lly rrntinll~u~ sheet of dielectric of lower permittivity than the substrate of the uppermost board may be used as a spacer, the thickness of the spacer 30 being selected as rer~uired. For example the uppermost W095~302~3 2 1 8~239 I l . ?'~
circuit board may have a glass f ibre substrate, and the sheet may be f ormed f rom PTFE or polyamide . This CLLLCII~ , which does not require air between the boards, may produce a more rigid antenna.
As ~ npA above, the antenna may be formed on a printed circuit board. In addition to substantially rigid substrates, such as glass-fibre or SRBP, a f 1 .oY; hl 1~ gubgtrate, guch as acetate or polyethylene may be used. Such boards are commonly referred to in the art as ~'flOEi-boards", and the term printed circuit board, as used in this sper;f;r~ti~nl is ;ntl~n~ to 1_~' RS all guch variantg; the ~qq-~n~;~l requirement is that the board comprises a rrn~ r~ive ~e.g.
r -t~l 1 i qed) track on an insulating substrate.
If the printed circuit board is f 1 ~'Y; hl~, it may be more readily mounted on a 8urface which possess a degree of curvature, such as a vehicle windscreen.
In a dev~l~ J of the invention, a further loop may be spaced below the ground plane. The further ~0 loop preferably incorporates a resistance, of typically less than 100 S~. This can increase the ratio of the signal given above the ground plane to the signal given below the ground plane- This dev~ L ' of the invention incorporating a loop below the ground plane may be formed on a multi-layer printed circuit board, or on a plurality of spaced boards.
Antenna devices according to the present invention may be used over a very wide range of frequencies, by Relecting the ~1; RirnR appropriately 30 for the frequency employed. However, the antenna Wo95130253 2 l 89239 1 . .
.
device is preferably employed at frequencies above lO0 MHz up to several tens of G~z. Particularly, it may be u3ed at frequencies of around 800-1200 MXz, as used in mobile telephone systems. At such frequencies, the 5 loop may be formed on a first printed circuit board of about 2 mm thickness or less, spaced about 2 mm f rom a second circuit board ~orming the ground plane, the as~embly being about 6 mm thick or less and having sides of about 6 cm or less, to produce a very compact lO antenna.
Another advantage the present invention provides is that a substAnti~lly vertically polarised signal can be generated from a horizontally mounted planar antenna device. The r~ t;nn pattern o~ the hor;7Ont:llly 15 mounted device can be likened to that of a vertically mounted half-wave dipole.
Previously, it has been nPcP~a~ry to have a vertically protruding antenna in order to produce a vertically-polarised signal. This has many 20 disadvantages; for example, when mounted on a vehicle, a protruding aerial is conspicuous, causes a~:lu-ly--~.,.ic drag, and is prone to v~n~
The b~n-lw; ~th o~ the antenna can be altered by altering the thickness of the loop in a radial 25 direction.
According to a development of the invention, additional ron~ rt; ve portions may be attached around the circumference of the loop. These may be poPit;nnPd so as to act as tuned notch filters, to 30 reduce the antenna efficiency at selected frequencies, _ _ _ _ _ _ _ _ _ _ _ _ _, or to tune the antenna to a particular tr~nr-nl Rf~ n line .
The antenna device may be coupled to known tr~nr-r; cc; nn lines, in a variety of ways, a preferable 5 method being to connect an l1nhA 1 ~nred coaxial line directly to the two cnnn~rt; nn points, with the outer ground ~rnnnPctn~ also cnnnPrt~rl to the ground plane.
Alternatively, a h~1~nrpc7 line may simply be rnr1nPCtP~l to the two connection points ~neither of the rnnnPr~; nn 10 points being rnnnPcted directly to the ground plane).
As further alternatives, other known means of feeding an antenna may be used, in particular capacitors and/or inductors may be used to couple the antenna device to a tr~nr"~; cPinn line of a given; - ' .
1~ A preferred aLL"~ly. for coupling the antenna device to a (coaxial) line is to provide a subst~nt;~lly arcuate cnn~ rtn~ stub in the plane of the loop, outside and substantially parallel to a portion of the loop, said conductor stub having a 20 cnnnPct;nn point along its length joined to a first rnnnPrt;nn point of the loop and to the ground plane, the outer rnn~l~1rtnr of the coaxial line being rrnn~rtl~d to an end of said conductor stub, and the centre conductor of said coaxial line being connected to the 25 second connection point of the loop.
The length and th; rknPcs of said conductor stub, its spacing from the loop, and the point of joining to the loop are selected to give the desired; ~ -rP and capacitance to match the loop to the coaxial line at a 30 desired frequency. In additlon, the length of exposed _ _ _ _ _ _ . .
~ W095130253 2 1 ~q239 I~.1 .,,1!'`7''1 central conductor of the transmission line is adjusted to provide a desired reactance for matching the tr~nP~; cq; nn line to the loop . The positions of the conneetion points around the loop are also varied to obtain the desired ; _ - ' re and resonant ~1 e~uell- y .
With this arrangement, the rnnnPct;nn points are pre~erably spaced 60-120 apart. More preferably thê
connection points are apprn~r;r~-tPly goo apart, typically being spaced 70-110 apart. This may make the eharaeteristics of the loop relatively insênsitive to manufacturing tolerances in positioning of the cnnnPct; nn points .
The effective eleetrical length of the loop may be altered (shortened) by forming a short eircuit from a point on the loop to a portion of the rnnrlllrtr~ stub.
I~ the loop is formed on a printed circuit board, the conductor stub may adv~nt~r,Pn~cl y be formed on the same board.
Adv~nt~r,Pn1~qly, the tr~nr~;qq;nn line (e.g.
eoaxial eable) is cnnnPctPd (e.g. soldered) direetly to the surfaee of the loop. This avoids the need for extra rnnA11rt; ve portions around the loop which may alter its characteristies, and allows the position of the connection points to be adjusted relatively easily.
Acrording to a development of the invention, means ean be provided for varying the length of the eleetrieally eonduetive loop. T-ypically, this can be achieved by providing a non-closed loop, in which each end is connected to a joining portion comprising a 30 rnnrlllrt;ve part. The two conductive parts, optionally wog~o~ - 2 1 8 9 2 3 9 1 , subst~nt;~l ly parallel, may be joined at any of a number of places along their length, so that the total length of conductive loop is varied.
~Pn~r:llly, the r~c;ctAnre of the electrically 5 r~nAIlrt; ve cloged loop is made low, typically less than 1 ~2. This reduces resistance losses, and increases the Q f actor of the antenna . ~owever, according to another dev.-l ~, , the resistance of the loop can be increased, typically by inserting a resistor (of typically from 300 Q - 600 Q) in the loop at a joining portion, to produce a wide band antenna device, having a low Q.
According to a further development of the invention, one or more conductive loops which are 15 either greater in circumference, or (more typically) smaller in circumference than the loop of the basic antenna device may be employed. These may be co-planar with the basic antenna loop (if that loop is itself planar), or may be located above the baaic loop, or 20 more typically between the basic loop and the ground plane. These can act to alter the directional pattern of the r~A;~t;rn, and can be used to achieve greater gain or directivity.
Pref erably, where the basic antenna device is 25 formed as a loop on a printed circuit board, the additional loop or loops may be formed on the same surf ace as the basic antenna loop .
According to another aspect of the invention, one or more capacitors can be inserted in the loop 30 (connected in series). This allows a wider bandwidth ..... ...
to be attained, and if these are inserted in a loop of irregular shape, a compact antenna device having a given directional pattern can be achieved. Typically, in an antenna device for use with signals of the 5 fr~-Pn~ R employed in mobile telephones, the capacitor, or capacitors will each have capacitance in the range of about 0 . 03-14 pF.
According to yet another aspect of the preaent invention, the antenna device of the present invention may be used to drive other antenna array systems which are otherwise ~l;ff;cl~lt to couple to a standard transmission line.
The antenna device of the present invention may be used in phased arrays, or in passive arrays.
The present invention also provides a mobile telephone incorporating such an antenna device. The antenna device can be mounted so that the ground-plane is between the user and the loop. In this way, the user may be shielded from the radiation by the ground plane, with the overall size ~:. ; n; n~ very small . It has been suggested that rAtl;Atinn from mobile t~ rhnn~
antennae can have disadvAnt~n -R effects on a user, but it has not hitherto been possible to provide a small efficient antenna device for a mobile t.~l~rh-~
which enables the user to be Rh; ~
nrl; ' ~ of the present invention will now be described, by way of example, with reference to the following drawings in which:
Figs. la-lc illustrate examples of prior art Ant~nnAF~;
WO 95130253 2 ~ 8 9 2 3 9 Fig. Z is a schematic diagram of a firat ` ~ li t of the present invention;
Fig. 3 is a plan view of a preferred: ` 'i of the present invention;
Fig. ~ i9 a side view of the ~ ' - '; of Fig .
3;
Fig. 5 ahows schematically alternative ways of coupling an antenna device of the present invention to tr~nr~i~ es;
Fig. 6 shows 8~h tic~lly an alternative ; ~i t;
Fig. 7 showg 8rh t;c~lly devPl ~ ~ of t,e invention in which di8tortion rings are present to alter th~e field pattern;
Fig. 8 shows approximate plots of field patter~s obtained in the present invention;
Figs . 9a and 9b are polar plots showing r~ t; ~n patterns obtained with the: ` o~ii of Figs. 3 and 4;
and Figs. lOa and lOb are comparative polar plots showing polar plots obtained with the co~ventional anteIma of Fig. lc.
As shown in Fig. 2 an: ' 'i ~ of the present invention comprises a loop 1, typically circular, spaced above a ground plane 2 by a dielectric 3. The loop 1 is conductive, and is typically made of copper.
The ground plane 2 i8 also conductive, and is also typically made of copper. The ground plane 2 is preferably formed as a ~ ntinll~nl~ conductive sheet, W0 9~30253 2 1 8 ~ 2 3 9 but, for example, a mesh, or other aLL~I, may be used. Differing dLLa~ P of ground planes are well known in the art, The antenna device i6 typically coupled to a 5 coaxial trAnPmi ~sinn line 5 . The central cnn~ nts~r 6 of the coaxial cable 5 is nnnn~ntprl to the loop at a cnnnPct;nn point 10, and the outer ~nn~llntive ~heath 7 is cnnn~ctp~ to the loop at a second connection point 11 spaced apart from the first ~nnn~rtinn point 10 by 10 an angle a. The angle ~ is typically 45. The second connection point 11 is also nnnnp~t~fl to the ground plane 2 . The coaxial cable has an outer; nP~ t; n~
sheath 8, and an inner dielectric sheath 9 between the central conductor 6 and outer conductive sheath 7.
The dielectric material may be, for example, PTFE, glass fibre board, S~3P, A~3S plastics, ceramics, or other suitable materials. It i8 also possible for the space~between the conductive loop and the ground plane to contain air. However, the ~; ainnP may be 20 reduced, and the maximum power transmitted increased if a suitable dielectric is chosen.
At higher frequencies, e.g. above 1 GHz, dielectric losses can become si~n;f;~-~nt~ and the material of the dielectric needs to be selected 25 appropriately. It has been found that PTFE: and ceramics materials are particularly suitable for use at higher frequencies, e.g. around 2 GHz.
The thickness of the ground plane should be sufficient to ensure low resistivity, to m;n;m;Pe 30 resistive losses. It is desirable to keep the conductor WO95/30253 2 l 8q239 i~I~v~, - . ~
th;rknPR~ small to reduce weight, and because at high frequencies the current flows mainly near the surface of the rnn~ tor. Preferably, the thi rl~nP~e i5 less than lcm, and more typically it is less than lmm, e . g .
5 formed as a r~n~ rtive copper (or silver or gold) layer on a printed circuit board.
Referring to Figs. 3 and 4, a preferred : '-'; for use in mobile tplprhrnp _ ;r~t;~n~
at a fre auency of apprt~;r-tply B00 MHz is described.
10 In this ` - ~; t, printed circuit boards are used to form the loop and ground plane: the loop 1 is formed on a printed circuit board substrate 3a which is spaced above the ground plane 2 comprising a r~nr~llrt;ve copper sheet on a circuit board substrate to leaving an air 15 gap 3b. The air gap 3b is ^-;nt~;nP~ by spacers 13a, 13b sandwiched between the substrate 3a and the ground plane 2.
The assembly is held together by a suitable known fixing means, such as adhesive (e.g. cyano-acrylate) or 20 P~tPrnAl clips. It is important that the fixing means does not a~fect the characteristics of the antenna, or that any effect is . ,~ ed for. For example, adhesive may affect the dielectric properties, or may contain moisture which is conductive. Likewise, use of 25 conductive clips may alter the antenna characteristics signif icantly .
A8 can most clearly be seen f rom Fig . 3, an arcuate conductive stub 15,19 is formed from a piece of track subst~nt;~lly parallel to a portion of the loop 3 0 1, and j oined to the loop 1 at a connection point 11 by _ _ _ .. .. . . .... . ... . .
a joining portion 16. A joint 17, which may comprise the same material as the rnn~rt;ve sheath 7 of the coaxial cable 5, is soldered to the conductive stub 15 ,19 and to the ground plane 2 . The central ron~llrtol^
5 6 of the coaxial cable 5 is soldered to the loop 1 at a connection point 10. The outer conductive sheath 7 of the cable 5 is soldered to a portion 15 of the rnn~ rt jve gtub 15,19. The other portion 19 of the stub 15 ,19 is shaped so as to match the cable to the loop at the desired resonant frequency.
The side of the antenna to which the trAnrm- ~sinn line is coupled may be varied, for example if an array of :~nt~nnF-~, ag described below, is employed.
Referring to the or;~nt~t;on of the antenna shown in Fig. 3, a second antenna may be mounted to the right of the antenna shown with its coaxial cable connected, mirror-fashion, to the left of the loop.
Matching is carried out exper;r t~l ly. The loop 1 is slightly smaller than would be required if the transmission line were connected directly to the rnnn~oct;on points, which gives the loop a slight (rilr~r; t~tive) rP~rtAnre at the resonant frequency.
The length of the arm 19 i5 then adjusted exper; ' ~1 ly to obtain the optimum (inductive) reactance, 80 that the currents flowing in the loop are substantially symmetrical, and maximum radiated f ield is obtained for a given input signal.
For use at approximately 85Q ME~z, a loop radius of about 19 mm was used, with a copper track width of 1.5 mm. The stub portion 15,19 had an overall length 1 _ _ _ _ _ _ _ _ _ _ W0 95/30253 2 ~ 8 9 2 3 9 16 of about 32 mm, formed from an arcuate portion of track having a width of 4 mm and a radius of curvature 5 of apprn~ tPly 23 mm. The width j of the joining portion 16 waa 5 mm. The overall width w of the 5 substrate 3a was 45 mm, and the overall height h was 51 mm approximate with the spacings a and b of the edge of the lip f rom the edge of the substrate being apprn~ tPly 2 mm. This was mounted on a ground plane 2 approximately 5 cm wide by 6 cm tall.
The portion of central cnn~ tnr 6 of the coaxial cable 8 exposed outside the outer sheath 7 was appro~ tPl y 15 mm long. Thiæ length was ~Pl ected to give best matching of the cable 8 to the antenna. With this aLLCIll~. t it wag found that it was not nPCP~18 1ry to couple the central rnn~llctnr 6 to the cnnnPCtinn point lO via a capacitor as in a conventional y match aL ' ~~
The substrate 3a was glass fibre circuit board, having a relative permittivity of S . 4, approximately 1.2 mm thick. The spacers 13a,13b were formed from strips of glass fibre board. To adjust the resonant frequency, for example to resonate in a different band, the thickness of the spacers 13a, 13b was altered by a small amount. For use at 835 MHz, each spacer has a thickness of approximately 1. 08 mm, and for 910 M~z, each spacer was 1.30 mm thick.
Thus in this embodiment, a small increase in the spacing of the ground plane and loop caused an increase in resonant LL~:~Ue~
1'.11 of the above 1J~L tPrs were determined W0 95/30253 2 1 8 q 2 3 ~
experi ~1 ly by trial and error. It wag found that parameter3 such as ; ~ nre and resonant f requency were relatively insensitive to gmall variations ( 5 mm or so) in the location of the connection point 10 or of the length of the portion 15 of the cnn~llrt;ve stub 15,19. This permits variation due to r-nllf~rtll~ing tolerances to be a~ ' t~.~. It was found that the dimensions of the portion 19 of the conductive stub 15,19 are relatively critical in detF~rm;n;ng resonant frequency and ~1 ;m1n~t;n~ spurious resonances.
As the angle ~ i8 reduced, the efficiency tends to drop, and as ~Y is increased, the usable bandwidth is found to decrease. Experi ~1 ly 90 is found to be optimum with the above ~; Ri-m~, and a 50 Q coaxial cable.
It was possible to shorten the effective electrical size of the antenna by short-circuiting a point on the conductive stub 19 to a point on the loop 1. Preferably said point on the loop 1 is substantially adjacent said point on the conductive stub 19 to which it is short-circuited. For example, in the ~ ; t depicted in Fig. 3, said points are located respectively on the loop 1 and on the r~n~l1lrt;ve stub 19, each being a few mm to the left of the joining portion 16.
Figs. 9 and 10, described below, show typical results nht~;n~d with the above ~ ;r ' and with a conventional antenna, in which the conv.-nt;~n~l antenna was driven at ~ higher power.
For use at lower frequencies, a larger loop is W0951302~3 2 1 8 9 2 3 q I ,~
used, and for use at higher fre~uencies, a smaller loop is used. In general, the loop circumference is typically a little over one-half of the effective wavelength employed, up to about three-~auarters of the wavelength employed. However, the precise size will depend on the d; ~1 ~octric used and the matching i~LL~ , and may be determined by trial and error.
As can be seen f rom the above .t ' - ' i , the circumference of the loop may be apprrY;r-t~ly one third of the free space wavelength.
It i8 generally found that the i, - ' t e increases as the angle tY between the n nnn~ct; nn points 10 ,11 increases . As the angle cY becomes small, the ~ff;~ n~y tends to drop, the antenna behaving like a short circuit.
Increasing the spacing between the cnn~ t ive loop l and the ground plane 2 is found to decrease the impedance of the antenna, and ~n~r=11y tends to decrease the resonant fre~uency. However, with certain arlculy~ c, an opposite effect is obtained.
Increasing the loop l circumference is found to decrease the resonant CLe~uel~y, but does not subst~nt;~11y affect the; -' ne if the same relative proportions are m~;nt~;n~
~nserting a dielectric 3,3a,3b having a higher relative permittivity between the loop and the ground plane tends to decrease the impedance, and also to decrease the resonant frequency.
The bandwidth iB de~elldellL on the above parameters, which are selected in, ' in=t;nn to obtain _ _ _ _ _ , . .. . . . _ . .. . . .. , _ W0 9~130253 2 1 8 9 2 3 9 a desired value.
Thus, the spacing of the Cnnnr~r~t i nn points 10, ll, the spacing of the loop l and the ground plane 7, the dielectric material 3,3a,3b, and the overall 5 circumference of the loop l may be altered to achieve a de6ired; ~ nce and resonant fre5~uency. The parameters are adjusted empirically while measuring voltage standing wave ratio while transmitting a signal of the desired fre~auency, and monitoring transmitted lO f ield strength until desired characteriætics are obtained, following the above general rules.
It has been found that attaching an extra conductive portion to the loop, 80 that the loop is not symmetrical alters the properties of the antenna. For 15 example, it can cause the loop to reject certain fre~uencies, and behave as a crude notch filter.
Although the antenna is preferably planar, it may be formed as a flexible structure, for example comprising one or more ~l ~-Y; hl e circuit boards . It is 20 found that mounting the antenna with a slight degree of curvature, such as that typical of a vehicle windscreen, does not substantially affect its characteristics. Thus an antenna for a vehicle windscreen may be formed as a flexible, preferably 25 self-adhesive, ~sticker~.
When mounted in a vehicle, it is found that an array of ;lntr~nnz~r~, typically 2 or 4, may give better results than a single antenna. The antennae may share a common ground plane 2, and the array is typically 30 subst~nt;;~lly planar, although it may be flexible as _ _ _ _ _ _ _ . .. .... _ _ wo gs/30253 2 1 ~ 9 2 3 9 1 1 , I ~
described above . The Ant~ ~nnA~ may be co-linear, the array forming a strip. Many aLLG.ly~ -q of signal ;nf~rg/dividers are known in the art for coupling a plurality of Antpnn~e to a single trAn~ ' q8i nn line .
5 A preferred aLLcL~y~ t of power dividing means which results in a compact antenna is to provide a strip line mounted above a ground plane, the strip line being electrically one half of the wavelength employed. Two AntPnnAP~ or further combiners in the case of more than 10 two Ant~nnA~, are coupled one to each end of the strip line, and the t~nP-; q,q; ~nn line is cnnn~cr~d to the centre. If this aLL_ _ is employed, the strip line may utilise the same ground plane 2 as the Ant F.nnA~o, In particular, the ground plane 2 may be formed as one side of a double-sided circuit board, the strip line being formed on the other side. Coaxial cable may be attached to the ends of the strip line, and rnnnect~ e~ to the Ant~.nnA.o as described previously.
20 Alternatively through-hole plating may be employed, the antenna array being formed as a multi-layer sandwich comprising ~5~ Pnt;Ally) loop, ground plane, strip line, with a through connection from the loop to the atrip line. This may result in a very compact 25 ~LL~ y . However it is found that this c~LL~ y re~uires a fair degree of trial and error to obtain the best results as the antenna characteristics can be affected by mutual coupling, and rollrl; n~ to the power dividing means . As an 30 alternative which is slightly less compact, but which _ _ . _ _ _ _ .. . . . .. .. . .
-~ WO 95/30253 2 1 ~ q 2 3 ~ n?~rl may be simpler to align, the strip line may be formed as a separate double-sided board mounted below the /n~Pnn:lP ground plane, the gtrip line facing away ~rom the antennae.
When an array of ~ntPnnAP is employed, the or;f-nt~t;nnR and/or phases of the individual i~ntFnn~P
may be chosen to provide a desired polarization pattern, e.g. a riuaSi circular polarisation. The desired pattern is obtained by trial and error, in accordance with known techniques for driving phased arrays o antennae.
As ahown s ' t;r;llly in Fig. 5a, an antenna device of the present invention can be coupled to a h;~l~ncP~ tr~qnFm;RR;nn line 26,27. The two wires 26,27 of the tr~nFm; RF; on liIle are rnnnPrtP~ via respective capacitors 28,29 to connection points 10,11 spaced around the loop. Each capacitor is chosen to match the impedance of the tr:~nrm; CR; nn line to that of the antenna using standard tPrhn;rll~PF. As discussed a}~ove, 20 the; ~dc~-e of the antenna itself can be altered to simplify matching to a transmission line of a given nre The capacitor5 would be of the order of about 10 pF for fre~uencies of the order of about 1 GHz. The loop can be cnnn~rtp~l to the ground plane 2 at a voltage minimum point by a ronn~rtrJr 20.
As shown in Fig. 5b a ~ feed may be employed, in which the central rnn~ll1rtor 6 of a coaxial cable 5 is coupled to a Cnnnpct; nn point 10 on the loop 1 via a capacitor 24. The sheath 7 is rnnn.~rtPrl to the ground plane 2, as is a further connection point 11 on the -W095130253 2 ~ 8 9 2 3 '~
loop 1.
Alternatively, as shown schematically in Fig. 5c, an h~ feed may be employed, in which the central conductor 6 of a coaxial cable 5 is coupled to the connection point 10 on the loop 1 via a capacitor 24, and also to the grounded crnnrrt inrl point 11 on the ring via a further r~r~ritnr 25.
Other known means of feeding ~ntPnn~ may be employed . In a devPl ~, of the invention, as shown schematically in Fig. 6, a cnn~lllrtive loop 1 is formed having two parallel inwardly ~t~n~l;n~ portions 21,22.
These are bridged by a connection portion 23 at a pre-determined point along their length. The advantage of this aLLCIll, is that the l~r~t;nn of the connection point 23 can be varied relatively easily. For example, the loop 1 and inwardly Pl~t~n~l;n~ portions 21,22 may be formed as copper tracks on a printed circuit board, and the rnnn~ct; nn portion 23 may be formed as a bridge after ~-nllf~rtl~ring the printed circuit board. The antenna may be coupled to a tr~n~; c~; nn line by any of the methods previously discussed.
As a further alternative, the cnnn~rtir~n portion 23 shown in Fig. 6 may be replaced by a resistance, typically having a resistance of 300 Q-600 Q to give a relatively wide band aerial . It is f ound that the resistance of the loop is increased, the rrcnn~nre becomes less sharp. It is also necessary to re-adjust the; ~ nr~ of the loop, e.g. by varying the circumf erential spacing of the rnnnl~rt; on points 10 ,11.
As shown grl- tir~lly in Fig. 7a a distortion _ _ _ _ _ .. . . , _ _ . . ... .....
W0 95/30253 2 1 8 9 2 3 ~
ring 3 0 may be included inside the antenna loop 1, to alter the field pattern of the antenna. There may be - one or several rings 3 0, and these may be located inside, or outside the antenna loop 1.
In the devPl, ~ t ghown sr~ '; r:: l ly in Fig.
7b, the distortion ring 30 may be formed as a loop having parallel inwardly ~rt~nrl;nJ portions 31,32 joined by a bridge 33. Thus, in a similar way to the ' ~ shown in Fig. 4, the overall length of the distortion rings may be altered. Importantly, a resistance may be used as the bridge 33 completing the loop 3 0 .
Fig. 8a is a sketch giving an indication of the polar diagram obtained ~rom a single loop antenna lS device of the present invention. Axis 55 represents distance in a radial direction, and axis 56 represents vertical distance, with the ground plane horizontal, and the centre of the loop lying at the intersection of the axes. As can be seen, the curve 50, which is an approximate half power envelope, has a similar shape to that ~ht~in~.~l from a half-wave vertical dipole.
In Fig. 8b, the curve 50 obtained from a simple single-loop antenna device of the present invention is shown on the same axes as the curve 51` nht:~lnf~ for an antenna device having an inner distortion ring, as shown in Fig. 7a.
In a development of the present invention, a loop, similar to that illustrated in Fig. 6 may be employed, in which the connection portion 23 is 3 0 substituted by a capacitor . There may be one or more _ _ _ _ _ _ _ .... . ., .. ... ... . ... .. _ -WO 95/3u253 2 ~ 8 9 2 3 9 ~
capacitors located around the loop. This results in a wide band antenna, whose characteristics may be altered by adjusting the value of the capacitor(s) and/or the length of the intervening r~mnprt; ~n portions .
In use, it has been found that the results obtained with an antenna device of the present invention are g~n~r~lly better than those nht~n~cl with a helical wound aerial, as illustrated in Pig. lc, as conv.ont;nn~1ly used in mobile t~l~rh~lnF~R. It was found that in places where it was not possible to obtain sat; R~Flrtory operation of a mobile telephone using a conv~nt;r~n~1 aerial, reception was made possible by substituting the conventional aerial with an antenna device of the present invention.
Furthermore, the antenna radiates preferentially in a direction away f rom the ground plane . This allows the antenna to be fitted to a mobile ti~lPrhrn~ so that in use, the preferred direction of radiation is away from the body, as demonstrated by the results r~ht:3;n~rl Fig. 9a shows the r~ t;~n pattern rh~1n~d from the above described: ~Qrl;r ' of Figs. 3 and 4 when vertically mounted and fed with a signal of -15 . 8 d~3m at 840 MHz. The centre of the graph VLLe~U'~d~i to a field strength of -30 d3~V/m, measured at 3m from the antenna, and each r~nRerllt;ve outer ring corresponds to 5 d3 greater signal strength than the previous ring.
Fig. 9b shows the corresponding pattern obtained with the same antenna mounted on a Motorola ~s "Flip phone " .
Figs. lOa and lOb show the corresponding results ~ W095/30253 25 21 8 ,239 obtained with a conv~nti~-n~l helical antenn~ when fed with a stronger signal of -7 . 6 dBm.
As will be appreciated, the antenna of the present invention can be put to a variety of uses, the 5 characteristiCs being chosen for each particular ~rrl ;C~t;~n in accordance with the general t~ h;n~q of the above description.
According to yet another aspect of the preaent invention, the antenna device of the present invention may be used to drive other antenna array systems which are otherwise ~l;ff;cl~lt to couple to a standard transmission line.
The antenna device of the present invention may be used in phased arrays, or in passive arrays.
The present invention also provides a mobile telephone incorporating such an antenna device. The antenna device can be mounted so that the ground-plane is between the user and the loop. In this way, the user may be shielded from the radiation by the ground plane, with the overall size ~:. ; n; n~ very small . It has been suggested that rAtl;Atinn from mobile t~ rhnn~
antennae can have disadvAnt~n -R effects on a user, but it has not hitherto been possible to provide a small efficient antenna device for a mobile t.~l~rh-~
which enables the user to be Rh; ~
nrl; ' ~ of the present invention will now be described, by way of example, with reference to the following drawings in which:
Figs. la-lc illustrate examples of prior art Ant~nnAF~;
WO 95130253 2 ~ 8 9 2 3 9 Fig. Z is a schematic diagram of a firat ` ~ li t of the present invention;
Fig. 3 is a plan view of a preferred: ` 'i of the present invention;
Fig. ~ i9 a side view of the ~ ' - '; of Fig .
3;
Fig. 5 ahows schematically alternative ways of coupling an antenna device of the present invention to tr~nr~i~ es;
Fig. 6 shows 8~h tic~lly an alternative ; ~i t;
Fig. 7 showg 8rh t;c~lly devPl ~ ~ of t,e invention in which di8tortion rings are present to alter th~e field pattern;
Fig. 8 shows approximate plots of field patter~s obtained in the present invention;
Figs . 9a and 9b are polar plots showing r~ t; ~n patterns obtained with the: ` o~ii of Figs. 3 and 4;
and Figs. lOa and lOb are comparative polar plots showing polar plots obtained with the co~ventional anteIma of Fig. lc.
As shown in Fig. 2 an: ' 'i ~ of the present invention comprises a loop 1, typically circular, spaced above a ground plane 2 by a dielectric 3. The loop 1 is conductive, and is typically made of copper.
The ground plane 2 i8 also conductive, and is also typically made of copper. The ground plane 2 is preferably formed as a ~ ntinll~nl~ conductive sheet, W0 9~30253 2 1 8 ~ 2 3 9 but, for example, a mesh, or other aLL~I, may be used. Differing dLLa~ P of ground planes are well known in the art, The antenna device i6 typically coupled to a 5 coaxial trAnPmi ~sinn line 5 . The central cnn~ nts~r 6 of the coaxial cable 5 is nnnn~ntprl to the loop at a cnnnPct;nn point 10, and the outer ~nn~llntive ~heath 7 is cnnn~ctp~ to the loop at a second connection point 11 spaced apart from the first ~nnn~rtinn point 10 by 10 an angle a. The angle ~ is typically 45. The second connection point 11 is also nnnnp~t~fl to the ground plane 2 . The coaxial cable has an outer; nP~ t; n~
sheath 8, and an inner dielectric sheath 9 between the central conductor 6 and outer conductive sheath 7.
The dielectric material may be, for example, PTFE, glass fibre board, S~3P, A~3S plastics, ceramics, or other suitable materials. It i8 also possible for the space~between the conductive loop and the ground plane to contain air. However, the ~; ainnP may be 20 reduced, and the maximum power transmitted increased if a suitable dielectric is chosen.
At higher frequencies, e.g. above 1 GHz, dielectric losses can become si~n;f;~-~nt~ and the material of the dielectric needs to be selected 25 appropriately. It has been found that PTFE: and ceramics materials are particularly suitable for use at higher frequencies, e.g. around 2 GHz.
The thickness of the ground plane should be sufficient to ensure low resistivity, to m;n;m;Pe 30 resistive losses. It is desirable to keep the conductor WO95/30253 2 l 8q239 i~I~v~, - . ~
th;rknPR~ small to reduce weight, and because at high frequencies the current flows mainly near the surface of the rnn~ tor. Preferably, the thi rl~nP~e i5 less than lcm, and more typically it is less than lmm, e . g .
5 formed as a r~n~ rtive copper (or silver or gold) layer on a printed circuit board.
Referring to Figs. 3 and 4, a preferred : '-'; for use in mobile tplprhrnp _ ;r~t;~n~
at a fre auency of apprt~;r-tply B00 MHz is described.
10 In this ` - ~; t, printed circuit boards are used to form the loop and ground plane: the loop 1 is formed on a printed circuit board substrate 3a which is spaced above the ground plane 2 comprising a r~nr~llrt;ve copper sheet on a circuit board substrate to leaving an air 15 gap 3b. The air gap 3b is ^-;nt~;nP~ by spacers 13a, 13b sandwiched between the substrate 3a and the ground plane 2.
The assembly is held together by a suitable known fixing means, such as adhesive (e.g. cyano-acrylate) or 20 P~tPrnAl clips. It is important that the fixing means does not a~fect the characteristics of the antenna, or that any effect is . ,~ ed for. For example, adhesive may affect the dielectric properties, or may contain moisture which is conductive. Likewise, use of 25 conductive clips may alter the antenna characteristics signif icantly .
A8 can most clearly be seen f rom Fig . 3, an arcuate conductive stub 15,19 is formed from a piece of track subst~nt;~lly parallel to a portion of the loop 3 0 1, and j oined to the loop 1 at a connection point 11 by _ _ _ .. .. . . .... . ... . .
a joining portion 16. A joint 17, which may comprise the same material as the rnn~rt;ve sheath 7 of the coaxial cable 5, is soldered to the conductive stub 15 ,19 and to the ground plane 2 . The central ron~llrtol^
5 6 of the coaxial cable 5 is soldered to the loop 1 at a connection point 10. The outer conductive sheath 7 of the cable 5 is soldered to a portion 15 of the rnn~ rt jve gtub 15,19. The other portion 19 of the stub 15 ,19 is shaped so as to match the cable to the loop at the desired resonant frequency.
The side of the antenna to which the trAnrm- ~sinn line is coupled may be varied, for example if an array of :~nt~nnF-~, ag described below, is employed.
Referring to the or;~nt~t;on of the antenna shown in Fig. 3, a second antenna may be mounted to the right of the antenna shown with its coaxial cable connected, mirror-fashion, to the left of the loop.
Matching is carried out exper;r t~l ly. The loop 1 is slightly smaller than would be required if the transmission line were connected directly to the rnnn~oct;on points, which gives the loop a slight (rilr~r; t~tive) rP~rtAnre at the resonant frequency.
The length of the arm 19 i5 then adjusted exper; ' ~1 ly to obtain the optimum (inductive) reactance, 80 that the currents flowing in the loop are substantially symmetrical, and maximum radiated f ield is obtained for a given input signal.
For use at approximately 85Q ME~z, a loop radius of about 19 mm was used, with a copper track width of 1.5 mm. The stub portion 15,19 had an overall length 1 _ _ _ _ _ _ _ _ _ _ W0 95/30253 2 ~ 8 9 2 3 9 16 of about 32 mm, formed from an arcuate portion of track having a width of 4 mm and a radius of curvature 5 of apprn~ tPly 23 mm. The width j of the joining portion 16 waa 5 mm. The overall width w of the 5 substrate 3a was 45 mm, and the overall height h was 51 mm approximate with the spacings a and b of the edge of the lip f rom the edge of the substrate being apprn~ tPly 2 mm. This was mounted on a ground plane 2 approximately 5 cm wide by 6 cm tall.
The portion of central cnn~ tnr 6 of the coaxial cable 8 exposed outside the outer sheath 7 was appro~ tPl y 15 mm long. Thiæ length was ~Pl ected to give best matching of the cable 8 to the antenna. With this aLLCIll~. t it wag found that it was not nPCP~18 1ry to couple the central rnn~llctnr 6 to the cnnnPCtinn point lO via a capacitor as in a conventional y match aL ' ~~
The substrate 3a was glass fibre circuit board, having a relative permittivity of S . 4, approximately 1.2 mm thick. The spacers 13a,13b were formed from strips of glass fibre board. To adjust the resonant frequency, for example to resonate in a different band, the thickness of the spacers 13a, 13b was altered by a small amount. For use at 835 MHz, each spacer has a thickness of approximately 1. 08 mm, and for 910 M~z, each spacer was 1.30 mm thick.
Thus in this embodiment, a small increase in the spacing of the ground plane and loop caused an increase in resonant LL~:~Ue~
1'.11 of the above 1J~L tPrs were determined W0 95/30253 2 1 8 q 2 3 ~
experi ~1 ly by trial and error. It wag found that parameter3 such as ; ~ nre and resonant f requency were relatively insensitive to gmall variations ( 5 mm or so) in the location of the connection point 10 or of the length of the portion 15 of the cnn~llrt;ve stub 15,19. This permits variation due to r-nllf~rtll~ing tolerances to be a~ ' t~.~. It was found that the dimensions of the portion 19 of the conductive stub 15,19 are relatively critical in detF~rm;n;ng resonant frequency and ~1 ;m1n~t;n~ spurious resonances.
As the angle ~ i8 reduced, the efficiency tends to drop, and as ~Y is increased, the usable bandwidth is found to decrease. Experi ~1 ly 90 is found to be optimum with the above ~; Ri-m~, and a 50 Q coaxial cable.
It was possible to shorten the effective electrical size of the antenna by short-circuiting a point on the conductive stub 19 to a point on the loop 1. Preferably said point on the loop 1 is substantially adjacent said point on the conductive stub 19 to which it is short-circuited. For example, in the ~ ; t depicted in Fig. 3, said points are located respectively on the loop 1 and on the r~n~l1lrt;ve stub 19, each being a few mm to the left of the joining portion 16.
Figs. 9 and 10, described below, show typical results nht~;n~d with the above ~ ;r ' and with a conventional antenna, in which the conv.-nt;~n~l antenna was driven at ~ higher power.
For use at lower frequencies, a larger loop is W0951302~3 2 1 8 9 2 3 q I ,~
used, and for use at higher fre~uencies, a smaller loop is used. In general, the loop circumference is typically a little over one-half of the effective wavelength employed, up to about three-~auarters of the wavelength employed. However, the precise size will depend on the d; ~1 ~octric used and the matching i~LL~ , and may be determined by trial and error.
As can be seen f rom the above .t ' - ' i , the circumference of the loop may be apprrY;r-t~ly one third of the free space wavelength.
It i8 generally found that the i, - ' t e increases as the angle tY between the n nnn~ct; nn points 10 ,11 increases . As the angle cY becomes small, the ~ff;~ n~y tends to drop, the antenna behaving like a short circuit.
Increasing the spacing between the cnn~ t ive loop l and the ground plane 2 is found to decrease the impedance of the antenna, and ~n~r=11y tends to decrease the resonant fre~uency. However, with certain arlculy~ c, an opposite effect is obtained.
Increasing the loop l circumference is found to decrease the resonant CLe~uel~y, but does not subst~nt;~11y affect the; -' ne if the same relative proportions are m~;nt~;n~
~nserting a dielectric 3,3a,3b having a higher relative permittivity between the loop and the ground plane tends to decrease the impedance, and also to decrease the resonant frequency.
The bandwidth iB de~elldellL on the above parameters, which are selected in, ' in=t;nn to obtain _ _ _ _ _ , . .. . . . _ . .. . . .. , _ W0 9~130253 2 1 8 9 2 3 9 a desired value.
Thus, the spacing of the Cnnnr~r~t i nn points 10, ll, the spacing of the loop l and the ground plane 7, the dielectric material 3,3a,3b, and the overall 5 circumference of the loop l may be altered to achieve a de6ired; ~ nce and resonant fre5~uency. The parameters are adjusted empirically while measuring voltage standing wave ratio while transmitting a signal of the desired fre~auency, and monitoring transmitted lO f ield strength until desired characteriætics are obtained, following the above general rules.
It has been found that attaching an extra conductive portion to the loop, 80 that the loop is not symmetrical alters the properties of the antenna. For 15 example, it can cause the loop to reject certain fre~uencies, and behave as a crude notch filter.
Although the antenna is preferably planar, it may be formed as a flexible structure, for example comprising one or more ~l ~-Y; hl e circuit boards . It is 20 found that mounting the antenna with a slight degree of curvature, such as that typical of a vehicle windscreen, does not substantially affect its characteristics. Thus an antenna for a vehicle windscreen may be formed as a flexible, preferably 25 self-adhesive, ~sticker~.
When mounted in a vehicle, it is found that an array of ;lntr~nnz~r~, typically 2 or 4, may give better results than a single antenna. The antennae may share a common ground plane 2, and the array is typically 30 subst~nt;;~lly planar, although it may be flexible as _ _ _ _ _ _ _ . .. .... _ _ wo gs/30253 2 1 ~ 9 2 3 9 1 1 , I ~
described above . The Ant~ ~nnA~ may be co-linear, the array forming a strip. Many aLLG.ly~ -q of signal ;nf~rg/dividers are known in the art for coupling a plurality of Antpnn~e to a single trAn~ ' q8i nn line .
5 A preferred aLLcL~y~ t of power dividing means which results in a compact antenna is to provide a strip line mounted above a ground plane, the strip line being electrically one half of the wavelength employed. Two AntPnnAP~ or further combiners in the case of more than 10 two Ant~nnA~, are coupled one to each end of the strip line, and the t~nP-; q,q; ~nn line is cnnn~cr~d to the centre. If this aLL_ _ is employed, the strip line may utilise the same ground plane 2 as the Ant F.nnA~o, In particular, the ground plane 2 may be formed as one side of a double-sided circuit board, the strip line being formed on the other side. Coaxial cable may be attached to the ends of the strip line, and rnnnect~ e~ to the Ant~.nnA.o as described previously.
20 Alternatively through-hole plating may be employed, the antenna array being formed as a multi-layer sandwich comprising ~5~ Pnt;Ally) loop, ground plane, strip line, with a through connection from the loop to the atrip line. This may result in a very compact 25 ~LL~ y . However it is found that this c~LL~ y re~uires a fair degree of trial and error to obtain the best results as the antenna characteristics can be affected by mutual coupling, and rollrl; n~ to the power dividing means . As an 30 alternative which is slightly less compact, but which _ _ . _ _ _ _ .. . . . .. .. . .
-~ WO 95/30253 2 1 ~ q 2 3 ~ n?~rl may be simpler to align, the strip line may be formed as a separate double-sided board mounted below the /n~Pnn:lP ground plane, the gtrip line facing away ~rom the antennae.
When an array of ~ntPnnAP is employed, the or;f-nt~t;nnR and/or phases of the individual i~ntFnn~P
may be chosen to provide a desired polarization pattern, e.g. a riuaSi circular polarisation. The desired pattern is obtained by trial and error, in accordance with known techniques for driving phased arrays o antennae.
As ahown s ' t;r;llly in Fig. 5a, an antenna device of the present invention can be coupled to a h;~l~ncP~ tr~qnFm;RR;nn line 26,27. The two wires 26,27 of the tr~nFm; RF; on liIle are rnnnPrtP~ via respective capacitors 28,29 to connection points 10,11 spaced around the loop. Each capacitor is chosen to match the impedance of the tr:~nrm; CR; nn line to that of the antenna using standard tPrhn;rll~PF. As discussed a}~ove, 20 the; ~dc~-e of the antenna itself can be altered to simplify matching to a transmission line of a given nre The capacitor5 would be of the order of about 10 pF for fre~uencies of the order of about 1 GHz. The loop can be cnnn~rtp~l to the ground plane 2 at a voltage minimum point by a ronn~rtrJr 20.
As shown in Fig. 5b a ~ feed may be employed, in which the central rnn~ll1rtor 6 of a coaxial cable 5 is coupled to a Cnnnpct; nn point 10 on the loop 1 via a capacitor 24. The sheath 7 is rnnn.~rtPrl to the ground plane 2, as is a further connection point 11 on the -W095130253 2 ~ 8 9 2 3 '~
loop 1.
Alternatively, as shown schematically in Fig. 5c, an h~ feed may be employed, in which the central conductor 6 of a coaxial cable 5 is coupled to the connection point 10 on the loop 1 via a capacitor 24, and also to the grounded crnnrrt inrl point 11 on the ring via a further r~r~ritnr 25.
Other known means of feeding ~ntPnn~ may be employed . In a devPl ~, of the invention, as shown schematically in Fig. 6, a cnn~lllrtive loop 1 is formed having two parallel inwardly ~t~n~l;n~ portions 21,22.
These are bridged by a connection portion 23 at a pre-determined point along their length. The advantage of this aLLCIll, is that the l~r~t;nn of the connection point 23 can be varied relatively easily. For example, the loop 1 and inwardly Pl~t~n~l;n~ portions 21,22 may be formed as copper tracks on a printed circuit board, and the rnnn~ct; nn portion 23 may be formed as a bridge after ~-nllf~rtl~ring the printed circuit board. The antenna may be coupled to a tr~n~; c~; nn line by any of the methods previously discussed.
As a further alternative, the cnnn~rtir~n portion 23 shown in Fig. 6 may be replaced by a resistance, typically having a resistance of 300 Q-600 Q to give a relatively wide band aerial . It is f ound that the resistance of the loop is increased, the rrcnn~nre becomes less sharp. It is also necessary to re-adjust the; ~ nr~ of the loop, e.g. by varying the circumf erential spacing of the rnnnl~rt; on points 10 ,11.
As shown grl- tir~lly in Fig. 7a a distortion _ _ _ _ _ .. . . , _ _ . . ... .....
W0 95/30253 2 1 8 9 2 3 ~
ring 3 0 may be included inside the antenna loop 1, to alter the field pattern of the antenna. There may be - one or several rings 3 0, and these may be located inside, or outside the antenna loop 1.
In the devPl, ~ t ghown sr~ '; r:: l ly in Fig.
7b, the distortion ring 30 may be formed as a loop having parallel inwardly ~rt~nrl;nJ portions 31,32 joined by a bridge 33. Thus, in a similar way to the ' ~ shown in Fig. 4, the overall length of the distortion rings may be altered. Importantly, a resistance may be used as the bridge 33 completing the loop 3 0 .
Fig. 8a is a sketch giving an indication of the polar diagram obtained ~rom a single loop antenna lS device of the present invention. Axis 55 represents distance in a radial direction, and axis 56 represents vertical distance, with the ground plane horizontal, and the centre of the loop lying at the intersection of the axes. As can be seen, the curve 50, which is an approximate half power envelope, has a similar shape to that ~ht~in~.~l from a half-wave vertical dipole.
In Fig. 8b, the curve 50 obtained from a simple single-loop antenna device of the present invention is shown on the same axes as the curve 51` nht:~lnf~ for an antenna device having an inner distortion ring, as shown in Fig. 7a.
In a development of the present invention, a loop, similar to that illustrated in Fig. 6 may be employed, in which the connection portion 23 is 3 0 substituted by a capacitor . There may be one or more _ _ _ _ _ _ _ .... . ., .. ... ... . ... .. _ -WO 95/3u253 2 ~ 8 9 2 3 9 ~
capacitors located around the loop. This results in a wide band antenna, whose characteristics may be altered by adjusting the value of the capacitor(s) and/or the length of the intervening r~mnprt; ~n portions .
In use, it has been found that the results obtained with an antenna device of the present invention are g~n~r~lly better than those nht~n~cl with a helical wound aerial, as illustrated in Pig. lc, as conv.ont;nn~1ly used in mobile t~l~rh~lnF~R. It was found that in places where it was not possible to obtain sat; R~Flrtory operation of a mobile telephone using a conv~nt;r~n~1 aerial, reception was made possible by substituting the conventional aerial with an antenna device of the present invention.
Furthermore, the antenna radiates preferentially in a direction away f rom the ground plane . This allows the antenna to be fitted to a mobile ti~lPrhrn~ so that in use, the preferred direction of radiation is away from the body, as demonstrated by the results r~ht:3;n~rl Fig. 9a shows the r~ t;~n pattern rh~1n~d from the above described: ~Qrl;r ' of Figs. 3 and 4 when vertically mounted and fed with a signal of -15 . 8 d~3m at 840 MHz. The centre of the graph VLLe~U'~d~i to a field strength of -30 d3~V/m, measured at 3m from the antenna, and each r~nRerllt;ve outer ring corresponds to 5 d3 greater signal strength than the previous ring.
Fig. 9b shows the corresponding pattern obtained with the same antenna mounted on a Motorola ~s "Flip phone " .
Figs. lOa and lOb show the corresponding results ~ W095/30253 25 21 8 ,239 obtained with a conv~nti~-n~l helical antenn~ when fed with a stronger signal of -7 . 6 dBm.
As will be appreciated, the antenna of the present invention can be put to a variety of uses, the 5 characteristiCs being chosen for each particular ~rrl ;C~t;~n in accordance with the general t~ h;n~q of the above description.
Claims (26)
1. An antenna comprising an electrically conductive closed loop spaced above a ground plane, characterised in that the loop has first and second connection points spaced apart 30°-150° around the loop for coupling the loop to a transmission line.
2. An antenna according to claim 1 wherein the loop is substantially planar, the plane of the loop being parallel to the ground plane.
3. An antenna according to claim 2 wherein at least the loop is formed on a printed circuit board.
4. An antenna according to claim 3 wherein said printed circuit board is rigid.
5. An antenna according to any one of claims 1-3 wherein a first dielectric layer having a higher relative permittivity than air is provided between the loop and the ground plane.
6. An antenna according to claim 5 wherein a second dielectric layer or an air space having a lower relative permittivity than said first dielectric layer is provided between the loop and the ground plane.
7. An antenna according to claim 6 wherein the first dielectric layer is adjacent the loop and the second dielectric layer or air space is adjacent the ground plane.
8. An antenna according to any one of the preceding claims wherein one of said first and second connection points is connected to the ground plane.
9. An antenna according to any one of the preceding claims comprising a further conductive portion connected to the loop.
10. An antenna according to claim 9 wherein said further conductive portion is connected to one of said first and second connection points.
11. An antenna according to claim 10 arranged for connection to a coaxial transmission line having a central conductor and an outer conductor, wherein the first connection point is arranged for connection to said central conductor, and said further conductive portion comprises a strip adjacent to the outside of a portion of the loop, said strip comprising a first arm portion arranged for connection to said outer conductor of the transmission line, a second arm portion arranged to provide a reactance to match said transmission line to the loop, and a joining portion, connected to the second connection point of the loop and to the ground plane, joining said first and second arm portions.
12. An antenna according to any one of the preceding claims wherein the loop is substantially circular.
13. An antenna according to claim 12 wherein said connection points are spaced between 60° and 120° apart.
14. An antenna according to any one of the preceding claims adapted for use at frequencing above 600 MHZ, wherein the diameter of the loop is 8cm or less.
15. An antenna according to any one of the preceding claims adapted and arranged for use in mobile telephone communications.
16. An antenna according to any one of claims 1 to 3 or 5 to 15, wherein the antenna is flexible.
17. An antenna according to any one of the preceding claims adapted and arranged for mounting on a vehicle windscreen.
18. An antenna according to any one of the preceding claims wherein the spacing between the loop and the ground plane is 1cm or less.
19. An antenna array comprising a plurality of antennae according to any one of the preceding claims.
20. An antenna array according to claim 18 comprising combining means for coupling at least two of said plurality of antennae to a single transmission line.
21. An antenna array according to claim 18 wherein said combing means comprises a conductive strip spaced below said ground plane.
22. A mobile telephone comprising an antenna according to any one of claims 1 to 16.
23. A mobile telephone according to claim 21 arranged so that in use the ground plane of the antenna is positioned between the loop and the user of the mobile telephone.
24. Use of an antenna according to any one of claims 1 to 17 in mobile telephone communications.
25. An antenna comprising an electrically conductive closed loop spaced above a ground plane, the loop having first and second connection points spaced around the loop for coupling the loop to a coaxial transmission line having a central conductor and an outer conductor, wherein the first connection point is arranged for connection to said central conductor, and a further conductive portion comprising a strip is provided adjacent the outside of a portion of the loop, the strip comprising a first arm portion arranged for connection to the outer conductor of the transmission line, a second 29a arm portion arranged to provide a reactance to match said transmission line to the loop, and a joining portion connected to the second connection point of the loop and to the ground plane, and joining said first and second arm portions.
26. A mobile telephone having an antenna comprising an electrically conductive closed loop spaced above a ground plane, the loop having first and second connection points spaced around the loop for coupling the loop to a transmission line, arranged so that in use the ground plane of the antenna is positioned between the loop and a user of the mobile telephone.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9408720.2 | 1994-05-03 | ||
| GB9408720A GB9408720D0 (en) | 1994-05-03 | 1994-05-03 | Antenna device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2189239A1 true CA2189239A1 (en) | 1995-11-09 |
Family
ID=10754467
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002189239A Abandoned CA2189239A1 (en) | 1994-05-03 | 1994-12-05 | Antenna device and mobile telephone |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0759211A1 (en) |
| JP (1) | JPH10503625A (en) |
| AU (1) | AU710351B2 (en) |
| CA (1) | CA2189239A1 (en) |
| GB (1) | GB9408720D0 (en) |
| MX (1) | MX9502036A (en) |
| WO (1) | WO1995030253A1 (en) |
| ZA (1) | ZA953554B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7400302B2 (en) * | 2006-01-30 | 2008-07-15 | Centurion Wireless Technologies, Inc. | Internal antenna for handheld mobile phones and wireless devices |
| US9641927B2 (en) * | 2015-01-12 | 2017-05-02 | Qualcomm Technologies International, Ltd. | Antennas suitable for wireless earphones |
| WO2018113927A1 (en) * | 2016-12-20 | 2018-06-28 | Sonova Ag | Bte hearing instrument comprising a loop antenna |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1387679A (en) * | 1972-11-15 | 1975-03-19 | Wallace D A R | Antenna |
| US4236160A (en) * | 1978-10-10 | 1980-11-25 | Johnson Gregory F | Loop driven element antenna system and voltage feed system |
| DE8814993U1 (en) * | 1988-01-04 | 1989-03-02 | Oppermann, Richard, 7762 Ludwigshafen, De | |
| AU7761091A (en) * | 1990-04-09 | 1991-10-30 | Adalbert Kopera | Antenna assembly |
| JPH0414304A (en) * | 1990-05-08 | 1992-01-20 | Nippon Sheet Glass Co Ltd | Stacked loop antenna |
-
1994
- 1994-05-03 GB GB9408720A patent/GB9408720D0/en active Pending
- 1994-12-05 MX MX9502036A patent/MX9502036A/en unknown
- 1994-12-05 JP JP7528041A patent/JPH10503625A/en active Pending
- 1994-12-05 AU AU11169/95A patent/AU710351B2/en not_active Expired - Fee Related
- 1994-12-05 EP EP95902234A patent/EP0759211A1/en not_active Withdrawn
- 1994-12-05 WO PCT/GB1994/002661 patent/WO1995030253A1/en not_active Application Discontinuation
- 1994-12-05 CA CA002189239A patent/CA2189239A1/en not_active Abandoned
-
1995
- 1995-05-03 ZA ZA953554A patent/ZA953554B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| AU1116995A (en) | 1995-11-29 |
| WO1995030253A1 (en) | 1995-11-09 |
| AU710351B2 (en) | 1999-09-16 |
| ZA953554B (en) | 1996-01-11 |
| JPH10503625A (en) | 1998-03-31 |
| MX9502036A (en) | 1997-02-28 |
| GB9408720D0 (en) | 1994-06-22 |
| EP0759211A1 (en) | 1997-02-26 |
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