EP2089933A1 - Multi-frequency antenna - Google Patents

Multi-frequency antenna

Info

Publication number
EP2089933A1
EP2089933A1 EP07824512A EP07824512A EP2089933A1 EP 2089933 A1 EP2089933 A1 EP 2089933A1 EP 07824512 A EP07824512 A EP 07824512A EP 07824512 A EP07824512 A EP 07824512A EP 2089933 A1 EP2089933 A1 EP 2089933A1
Authority
EP
European Patent Office
Prior art keywords
antenna
antenna according
frequency
antenna portion
conduction layer
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.)
Withdrawn
Application number
EP07824512A
Other languages
German (de)
French (fr)
Inventor
Chicot Van Niekerk
Stefan Eben Goosen
Reinart Johan Moraal
Johan Izak Jacobus Fick
Christopher Pieter Smith
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wavetrend Technologies Ltd
Original Assignee
Wavetrend Technologies Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wavetrend Technologies Ltd filed Critical Wavetrend Technologies Ltd
Publication of EP2089933A1 publication Critical patent/EP2089933A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
    • H01Q9/0421—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with a shorting wall or a shorting pin at one end of the element
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/2208—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/30—Combinations of separate antenna units operating in different wavebands and connected to a common feeder system
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
    • H01Q5/30—Arrangements for providing operation on different wavebands
    • H01Q5/307—Individual or coupled radiating elements, each element being fed in an unspecified way
    • H01Q5/342—Individual or coupled radiating elements, each element being fed in an unspecified way for different propagation modes
    • H01Q5/357—Individual or coupled radiating elements, each element being fed in an unspecified way for different propagation modes using a single feed point
    • H01Q5/364—Creating multiple current paths
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
    • H01Q9/0442—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with particular tuning means

Definitions

  • the present invention relates to multi-frequency antennas, and in particular, but not exclusively to multi-frequency patch antennas.
  • any RF system is the design of an appropriate antenna that is able to transmit and receive wireless data as required, but additionally is able to meet the specific operational requirements of the application in question.
  • the RF designer must try and select the type of antenna whose properties are most suitable for the relevant application. For example, for a mobile phone application the RF designer will typically look for a compact antenna design having low-power properties that occur when size, weight and portability are important, as they are in the wireless field.
  • antenna geometries for example the standard dipole or loop antenna configurations.
  • RFID radio frequency identification
  • an antenna possessing certain properties for example: small in size, a low profile and lightweight.
  • Such antennas can be used as transmitters, receivers or transceivers that can be easily attached to a package or other moveable asset to be tracked.
  • a patch antenna is often most suitable.
  • a patch antenna consists of a patch of metallisation overlying, yet separated from, a ground plate, by an insulating substrate.
  • the patch antenna is manufactured by etching an antenna element pattern in a metal trace that is bonded to the insulating substrate. Advantages of such antennas include.that they are easy to manufacture and mechanically rugged. Moreover, patch antennas can accommodate polarisation diversity.
  • the patch antenna has an underlying ground plate 100, a dielectric layer 140 located on the ground plate 100, a conduction layer 110 located on the dielectric layer 140, and an antenna feed point 130.
  • the patch antenna of figures 1 and 2 can be manufactured, for example using known printed circuit board (PCB) techniques.
  • the patch antenna of figures 1 and 2 has a radiation pattern in any direction above the ground plane in a hemispherical area.
  • the thickness of the dielectric layer 140 determines the separation of the conduction layer 110 from the ground plate 100, which effects the frequency range (bandwidth) of the patch antenna. Generally, the thicker the dielectric layer 140, the higher the bandwidth.
  • the physical size of the patch has an impact on the performance of the patch.
  • the physical size of the antenna has an impact on the performance of the patch.
  • the trade-off when designing such patch antennas, for a certain resonating frequency is that performance often deteriorates as the size of the patch is reduced.
  • Embodiments of the present invention seek to provide improved multi-frequency antennas.
  • SUMMARY OF THE INVENTION frequency antenna comprising: a ground layer; a conduction layer provided with a first and second elongated recess; and a dielectric layer provided between the ground layer and the conduction layer; wherein the first and second elongated recess enable the antenna to operate as a first antenna portion having a first operating frequency and a second antenna portion having a second operating frequency different from the first operating frequency.
  • One advantage of the antenna of the present invention is that it can transmit twice the information, by having two independent communications channels.
  • the second antenna portion forms part of the first antenna portion.
  • the conduction layer is electrically connected to the ground layer.
  • the conduction layer is electrically connected to the ground layer by metallic via's.
  • the antenna further comprises: a capacitive element connected to the conduction layer at a feed point edge.
  • the capacitive element comprises a plurality of capacitors.
  • the plurality of capacitors are spaced equally along the feed point edge.
  • At least one of the plurality of capacitors forms part of the first antenna portion, and at least one of the plurality of capacitors forms part of the second antenna portion and the first antenna portion.
  • the capacitive element is connected to the ground layer.
  • the capacitive element is connected to the ground layer by metallic via's.
  • the first and second elongated recesses are provided substantially parallel to each other.
  • the first and second elongated recesses are provided substantially parallel to a non-radiating edge of the conduction layer.
  • an area defined by outside edges of the conduction layer forms the first antenna portion, and an area defined between the first and second elongated recesses forms the second antenna portion.
  • the first frequency is less than the second frequency.
  • one of the first antenna portion and the second antenna portion is capable of receiving signals, and the other of the first antenna portion and the second antenna portion is capable of transmitting signals.
  • both the first antenna portion and the second antenna portion are capable of transmitting and receiving signals.
  • the first antenna portion and the second antenna portion are capable of operating simultaneously. is arranged to operate at a frequency in a range of 420 MHz to 460 MHz.
  • the first antenna portion is arranged to operate at a frequency of substantially 433 MHz
  • the second antenna portion is arranged to operate at a frequency in a range of 850 MHz to 1000 MHz.
  • the second antenna portion is arranged to operate at a frequency of substantially 915 MHz.
  • the first and second frequencies are matched to an impedance of 50 ohms.
  • the length I of the first and second elongated recesses is in a range of 21 mm to 28 mm.
  • the length I of the first and second elongated recesses is substantially 21 mm.
  • the distance ⁇ between the first and second elongated recesses is in a range of 6 mm to 24 mm. According to another embodiment of the present invention, the distance ⁇ between the first and second elongated recesses is substantially 16 mm.
  • the width t of each of the first and second elongated recesses is in a range of 1 mm to 2 mm.
  • the width t of each of the first and second elongated recesses is substantially 1 mm.
  • the width W of the conduction layer is substantially 55 mm.
  • the length L of the conduction layer is in a range of 40 mm to 50 mm.
  • the length L of the conduction layer is substantially 44 mm.
  • the dielectric layer has a thickness greater than 1.6 mm.
  • the antenna is capable of operating off a metal surface.
  • the antenna is a patch antenna.
  • the antenna is used as part of a radio frequency tracking tag.
  • the ground layer is electrically grounded.
  • the antenna is square in shape.
  • a multi- frequency antenna comprising: a ground layer; a conduction layer; and a dielectric layer provided between the ground layer and the conduction layer, wherein the antenna has a first antenna portion capable of operating at a first frequency and a
  • the first frequency is different from the second frequency.
  • the second antenna portion forms part of the first antenna portion.
  • the conduction layer is electrically connected to the ground layer.
  • the conduction layer is electrically connected to the ground layer by metallic via's.
  • the antenna further comprises: a capacitive element connected to the conduction layer at a feed point edge.
  • the capacitive element comprises a plurality of capacitors.
  • the plurality of capacitors are spaced equally along the feed point edge. According to another embodiment of the present invention, at least one of the plurality of capacitors forms part of the first antenna portion, and at least one of the plurality of capacitors forms part of the first antenna portion and the second antenna portion.
  • the capacitive element is connected to the ground layer.
  • the capacitive element is connected to the ground layer by metallic via's.
  • a method of tuning the antenna of the present invention comprising: adjusting the distance between the first and second elongated recess, wherein when the distance between the first and second elongated recess is increased the operating frequency of the second antenna portion is decreased.
  • a method of tuning the antenna of the present invention comprising: adjusting the width of the first and second elongated recess, wherein when the width of the first and second elongated recess is increased the operating frequency of the second antenna portion is decreased.
  • a method of tuning the antenna of the present invention comprising: adjusting the length of the first and second elongated recess, wherein when the length of the first and second elongated recess is increased the operating frequency of the second antenna portion is decreased.
  • Figures 1 illustrates a plan view of a known patch antenna
  • Figure 2 illustrates a side view of the patch antenna of figure 1
  • Figure 3 illustrates a perspective view of an antenna according to an embodiment of the present invention
  • Figure 4 illustrates a cut through of the antenna of figure 3 taken along line
  • Figure 5 illustrates a plot of the desired frequency response of an antenna of the present invention
  • Figure 6 illustrates an impedance graph of an antenna of the present invention; antenna of the present invention when the distance ⁇ between two elongated slots of the antenna is varied;
  • Figure 8 illustrates computed variations in an operating frequency of an antenna of the present invention when the width t of elongated slots of the antenna is varied
  • Figure 9 illustrates computed variations in an operating frequency of an antenna of the present invention when the length I of elongated slots of the antenna is varied;
  • Figure 10 illustrates a current density plot of an antenna of the present invention operating at a relatively low frequency;
  • Figure 11 illustrates a current density plot of an antenna of the present invention operating at a relatively high frequency.
  • FIG. 3 illustrates a perspective view of a patch antenna according to a preferred embodiment of the present invention.
  • the antenna is a rectangular antenna having a ground plate 300, a separating dielectric substrate 340 and a printed conduction layer 310.
  • the antenna also has two elongated slots 96 and 98 formed in the conduction layer 310.
  • the two elongated slots 96 and 98 are formed substantially parallel to the non-radiating edges 320, 390 of the conduction layer 310.
  • One edge 350 of the conduction layer 310 is electrically connected to the ground plate 300.
  • metallic via's can be placed in respective holes formed in the dielectric layer 340 to electrically connect the edge 350 of the conduction layer 310 to the ground plate 300. Electrically connecting one edge 350 of the conduction layer 310 to the ground plate 300, effectively shorts that edge ⁇ edge 350) of the antenna to ground.
  • the conduction layer 310 is connected to a plurality of capacitors 380 located along the edge 360 of the conduction layer opposite to the edge 350.
  • the capacitors 380 increase the edge capacitance of the patch antenna.
  • each individual capacitor 380 of the plurality of capacitors 380 is connected to the conduction layer 310 and to the ground plate 300.
  • the capacitors 380 can be connected to the ground plate 300 by metallic via's which are placed in respective holes 330 formed in the dielectric layer 340 to electrically connect the capacitors 380 to the ground plate 300.
  • the capacitors 380 are located along the same edge of the conduction layer 310 as the RF feed point 370 and are distributed on either side of the RF feed point 370. In one embodiment, the capacitors are spaced equally along the edge 360 of the conduction layer 310. There is more than one capacitor 380 on each side of the feed point 370 such that current is distributed uniformly along the edge 360 of the conduction layer 310. This advantageously allows an even electromagnetic field distribution for the antenna.
  • capacitors 380 in the antenna of the present invention increases the edge capacitance of the antenna, thus enabling a reduction of the physical length of the antenna. That is, by adding capacitors 380 to the antenna circuit, the physical length of the antenna can be reduced, while still maintaining operation of the antenna at a particular desired resonating frequency. As stated above, when the physical length of the antenna is reduced, the resonating frequency of the antenna is increased.
  • the use of capacitors 380 increases the edge capacitance of the antenna and decreases the resonating frequency, therefore, compensating for the increase of resonating frequency experienced when the physical length of the antenna is reduced. Consequently, the use of capacitors 380 enables the physical length of the antenna to be reduced, without the resonating frequency being increased, since the capacitors 380 make the antenna look electrically longer than it is physically.
  • capacitors 380 are described above, the present invention is not limited to the use of capacitors 380. Any means for increasing the edge capacitance of the antenna, thus enabling a reduction of the physical length of the antenna can be z ⁇ seefc
  • Figure 4 illustrates a cross section of the antenna of figure 3, in operation, taken along line AA.
  • a pair of radiating fields 86 and 88 are setup within the respective slots 96 and 98 as illustrated in Figure 4.
  • the elongated slots are formed in the conduction layer 310.
  • These elongated slot radiation fields 86, 88 result in an inner antenna portion being created, in addition to the outer antenna portion defined by the outer radiating fields 81 and 83.
  • the area defined by the external edges of the conduction layer 310 illustrated in figure 3 forms an outer antenna portion.
  • the smaller area defined between the edges of elongated slots 96, 98, which is hatched in figure 3 forms an inner antenna portion.
  • the inner antenna portion also forms part of the outer antenna portion.
  • the antenna illustrated in figure 3 creates in operation, a small inner antenna portion within the slots 96, 98; and a large outer antenna portion.
  • the inner antenna portion has length I and width ⁇ , and the outer antenna portion has length L and width W.
  • the inner antenna portion has a smaller area than the outer antenna portion. Since the inner antenna portion has a smaller area than the outer antenna portion, the inner antenna portion is capable of operating at a higher resonating frequency than the outer antenna portion.
  • the geometry of the elongated slots 96, 98 is such that electrically it is almost as if the elongated slots 96, 98 do not exist. Consequently, the entire antenna portion operates at the lower resonating frequencies.
  • the geometry of the elongated slots 96, 98 becomes relevant. Consequently, only the inner antenna portion operates at the higher resonating frequencies
  • the advantage of forming slots 96 and 98 in the conductive layer 310 is that an antenna having a smaller inner antenna portion and a larger outer antenna portion is formed.
  • the resultant multi-frequency antenna is able to operate at two different resonating frequencies.
  • the outer antenna portion operates at a first resonating frequency
  • the inner antenna portion operates at a second resonating frequency, the first resonating frequency being lower than the second resonating
  • the antenna of the present invention is capable of simultaneously operating at the first and second resonating frequencies.
  • the antenna of the present invention is capable of transmitting and receiving signals.
  • the operating frequency of the inner antenna portion could be used as the transmit frequency
  • the operating frequency of the outer antenna portion could be used as the receive frequency or vice versa. Therefore, one antenna is capable of transmitting and receiving signals at different frequencies.
  • one or both of the inner and outer antenna portions could operate as transceivers, capable of transmitting and receiving signals.
  • the antenna of the present invention can operate at any combination of two resonating frequencies, which are spaced apart in the frequency spectrum. According to a preferred embodiment, the antenna operates at the frequencies detailed below:
  • the dielectric layer 340 has a thickness greater than 1.6 mm. Furthermore, the RF feed point 370 is located at the edge 360 of the conduction layer 310.
  • the antenna illustrated in figure 3 has a rectangular shape, however, it should be appreciated that other shapes of antenna are possible, for example a square or similar shape may be utilised. Some patch antennas are circular shapes.
  • Figure 5 illustrates the frequency response of an antenna of the present invention using a simulation package.
  • the plot shows that the antenna is operating with the first frequency pair listed above, in which the first operating frequency at point 42 is 433 MHz, while the second operating frequency at point 44 is the 915 MHz.
  • the desired frequency response of the antenna was simulated using electro magnetic simulation software, for example, Sonnet, IE3D, Microware Studio, etc.
  • figure 5 shows the desired frequency response of the antenna using a relevant simulation package.
  • Figure 6 is a further representation of the same simulation of the antenna according to the preferred embodiment, but whereas figure 5 illustrates the frequency response, figure 6 illustrates an impedance graph.
  • the second phase of antenna design involves prototyping the antenna, which can be constructed for example using ordinary FR-4 PCB material.
  • the antenna is then calibrated using the principle that the smaller the antenna, the more capacitance is needed for the antenna to function at the desired resonating frequency.
  • Figures 7 to 9 illustrate how adjusting the geometry of the antenna adjusts the frequency at which the antenna works.
  • Figure 7 illustrates the frequency variation when the width ⁇ of the inner antenna portion (the distance between the elongated slots) is varied.
  • the width ⁇ is varied from 6 mm to 24 mm (14 ⁇ varies from 3 mm to 12 mm).
  • the width W of the outer antenna portion (the conduction layer 310) is fixed at 55 mm;
  • the length L of the outer antenna portion (the conduction layer 310) is fixed at 44 mm;
  • the operating frequency of the inner antenna portion decreases.
  • variations in the width ⁇ of the inner antenna portion should antenna portion should maintain operation at 433 MHz.
  • Figure 8 illustrates the frequency variation when, the width t of the elongated slots is varied.
  • the width t of the elongated slots is increased from 1 mm to 2 mm in 0.1 mm increments.
  • Figure 9 illustrates the frequency variation when the length I of the elongated slots is varied.
  • the length I of the elongated slots is increased from 22 mm to 28 mm.
  • iWherrtQsJirigtl] ⁇ inner antenna portion decreases.
  • the operating frequency of the inner antenna portion is approximately 915 MHz.
  • the operating frequency of the inner antenna portion is approximately 850 MHz.
  • the width W of the outer antenna portion (the conduction layer 310) and the length L of the outer antenna portion (the conduction layer 310) may be varied.
  • the operating frequency of the outer antenna portion will deviate from 433 MHz and the operating frequency of the inner antenna portion in theory should remain constant.
  • the antenna has an outer antenna portion width W of 55 mm; an outer antenna portion length L of 44 mm; an inner antenna portion width ⁇ of 16 mm; an elongated slot width of 1 mm; and elongated slot length I of 21 mm.
  • Figures 10 and 11 illustrate the current density distribution for an antenna of the present invention when the outer antenna portion is operating at the resonating frequency of 433 MHz, and when the inner antenna portion is operating at the resonating frequency of 915 MHz.
  • the current density distribution is increased between the slots 96, 98 which define the inner antenna, when compared to the rest of the antenna. This is because the smaller inner antenna is being used to resonate at the higher frequency of 915 MHz.
  • the length I of the elongated slots 96, 98 is significant. If the slots are too short, the antenna does not resonate effectively on the higher frequencies. However, if the slots are too long, the antenna does not resonate effectively on the lower frequencies.
  • the slots are designed so that the antenna is able to accommodate two resonating frequencies, spaced sufficiently apart, but both frequencies are still matched, preferable to an impedance of 50 ohms, so that only one feed point 370 exists.
  • An antenna according to embodiments of the present invention can be of any form provided that the elongated slots 96, 98 are positioned such that an inner and an outer antenna are formed that operate at different frequencies.
  • an antenna of the present invention can be manufactured using known PCB techniques.
  • the elongated slots can be formed for example by using chemical or copper etching.
  • the antenna of the present invention is able to operate off a metal surface. Furthermore, the antenna of the present invention is more efficient when placed on a
  • present invention has particular application in the RF tag tracking field. Specifically, containers or packages that are to be couriered or routed to a particular destination can be tracked easily, by fixing an antenna of the present invention to the metal (or other) surface of such a container. Information about the container can therefore be easily transmitted or received.

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  • Waveguide Aerials (AREA)

Abstract

The present invention relates to a multi-frequency antenna comprising: a ground layer; a conduction layer provided with a first and second elongated recess; and a dielectric layer provided between the ground layer and the conduction layer; wherein the first and second elongated recess enable the antenna to operate as a first antenna portion having a first operating frequency and a second antenna portion having a second operating frequency different from the first operating frequency.

Description

MULTI-FREQUENCY ANTENNA
FIELD OF THE INVENTION
The present invention relates to multi-frequency antennas, and in particular, but not exclusively to multi-frequency patch antennas.
BACKGROUND
"Digttatcormnτmtaatto^ transmitted between various locations around the world. In particular, the field of wireless communications has seen advances in the area of mobile phone communications and/or other wireless computer-related devices. Indeed, such has been the growth of wireless communications, specifically RF (Radio Frequency) - type wireless communications, that the frequency spectrum for transmitting radio waves is becoming increasingly crowded.
One of the most important aspects of any RF system is the design of an appropriate antenna that is able to transmit and receive wireless data as required, but additionally is able to meet the specific operational requirements of the application in question. There are a plurality of different types of antenna designs to chose from, each having their own strengths and weaknesses. The RF designer must try and select the type of antenna whose properties are most suitable for the relevant application. For example, for a mobile phone application the RF designer will typically look for a compact antenna design having low-power properties that occur when size, weight and portability are important, as they are in the wireless field.
There are a plurality of known antenna geometries, for example the standard dipole or loop antenna configurations. However, in the area of RFID (radio frequency identification) tags it is desirable to have an antenna possessing certain properties, for example: small in size, a low profile and lightweight. Such antennas can be used as transmitters, receivers or transceivers that can be easily attached to a package or other moveable asset to be tracked. For this type of application a patch antenna is often most suitable.
A patch antenna consists of a patch of metallisation overlying, yet separated from, a ground plate, by an insulating substrate. The patch antenna is manufactured by etching an antenna element pattern in a metal trace that is bonded to the insulating substrate. Advantages of such antennas include.that they are easy to manufacture and mechanically rugged. Moreover, patch antennas can accommodate polarisation diversity.
zEigutedrilltistEatesrazplaE^^ side view of the patch antenna of figure 1.
As illustrated in figures 1 and 2 the patch antenna has an underlying ground plate 100, a dielectric layer 140 located on the ground plate 100, a conduction layer 110 located on the dielectric layer 140, and an antenna feed point 130. The patch antenna of figures 1 and 2 can be manufactured, for example using known printed circuit board (PCB) techniques.
The patch antenna of figures 1 and 2 has a radiation pattern in any direction above the ground plane in a hemispherical area.
The thickness of the dielectric layer 140 determines the separation of the conduction layer 110 from the ground plate 100, which effects the frequency range (bandwidth) of the patch antenna. Generally, the thicker the dielectric layer 140, the higher the bandwidth.
In addition, the physical size of the patch has an impact on the performance of the patch. For example, there exists an inverse relationship between the physical size of the antenna and the resonating frequency of the antenna. That is, if the patch size is reduced then the resonating frequency will increase and vice versa. Accordingly, the resonating frequency at which the antenna operates increases as the antenna size is reduced. The trade-off when designing such patch antennas, for a certain resonating frequency, is that performance often deteriorates as the size of the patch is reduced. However, for RFID applications it is desirable to reduce the size of the patch antenna as far as possible while still achieving adequate performance.
Embodiments of the present invention seek to provide improved multi-frequency antennas.
SUMMARY OF THE INVENTION frequency antenna comprising: a ground layer; a conduction layer provided with a first and second elongated recess; and a dielectric layer provided between the ground layer and the conduction layer; wherein the first and second elongated recess enable the antenna to operate as a first antenna portion having a first operating frequency and a second antenna portion having a second operating frequency different from the first operating frequency.
One advantage of the antenna of the present invention is that it can transmit twice the information, by having two independent communications channels.
According to another embodiment of the present invention the second antenna portion forms part of the first antenna portion.
According to another embodiment of the present invention the conduction layer is electrically connected to the ground layer.
According to another embodiment of the present invention the conduction layer is electrically connected to the ground layer by metallic via's.
According to another embodiment of the present invention, the antenna further comprises: a capacitive element connected to the conduction layer at a feed point edge. According to another embodiment of the present invention, the capacitive element comprises a plurality of capacitors.
According to another embodiment of the present invention, the plurality of capacitors are spaced equally along the feed point edge.
According to another embodiment of the present invention, at least one of the plurality of capacitors forms part of the first antenna portion, and at least one of the plurality of capacitors forms part of the second antenna portion and the first antenna portion.
According to another embodiment of the present invention, the capacitive element is connected to the ground layer.
According to another embodiment of the present invention, the capacitive element is connected to the ground layer by metallic via's.
According to another embodiment of the present invention, the first and second elongated recesses are provided substantially parallel to each other.
According to another embodiment of the present invention, the first and second elongated recesses are provided substantially parallel to a non-radiating edge of the conduction layer.
According to another embodiment of the present invention, an area defined by outside edges of the conduction layer forms the first antenna portion, and an area defined between the first and second elongated recesses forms the second antenna portion.
According to another embodiment of the present invention, the first frequency is less than the second frequency.
According to another embodiment of the present invention, one of the first antenna portion and the second antenna portion is capable of receiving signals, and the other of the first antenna portion and the second antenna portion is capable of transmitting signals.
According to another embodiment of the present invention, both the first antenna portion and the second antenna portion are capable of transmitting and receiving signals.
According to another embodiment of the present invention, the first antenna portion and the second antenna portion are capable of operating simultaneously. is arranged to operate at a frequency in a range of 420 MHz to 460 MHz.
According to another embodiment of the present invention, the first antenna portion is arranged to operate at a frequency of substantially 433 MHz
According to another embodiment of the present invention, the second antenna portion is arranged to operate at a frequency in a range of 850 MHz to 1000 MHz.
According to another embodiment of the present invention, the second antenna portion is arranged to operate at a frequency of substantially 915 MHz.
According to another embodiment of the present invention, the first and second frequencies are matched to an impedance of 50 ohms.
According to another embodiment of the present invention, the length I of the first and second elongated recesses is in a range of 21 mm to 28 mm.
According to another embodiment of the present invention, the length I of the first and second elongated recesses is substantially 21 mm.
According to another embodiment of the present invention, the distance ω between the first and second elongated recesses is in a range of 6 mm to 24 mm. According to another embodiment of the present invention, the distance ω between the first and second elongated recesses is substantially 16 mm.
According to another embodiment of the present invention, the width t of each of the first and second elongated recesses is in a range of 1 mm to 2 mm.
According to another embodiment of the present invention, the width t of each of the first and second elongated recesses is substantially 1 mm.
According to another embodiment of the present invention, the width W of the
According to another embodiment of the present invention, the width W of the conduction layer is substantially 55 mm.
According to another embodiment of the present invention, the length L of the conduction layer is in a range of 40 mm to 50 mm.
According to another embodiment of the present invention, the length L of the conduction layer is substantially 44 mm.
According to another embodiment of the present invention, the dielectric layer has a thickness greater than 1.6 mm.
According to another embodiment of the present invention, the antenna is capable of operating off a metal surface.
According to another embodiment of the present invention, the antenna is a patch antenna.
According to another embodiment of the present invention, the antenna is used as part of a radio frequency tracking tag. According to another embodiment of the present invention, the ground layer is electrically grounded.
According to another embodiment of the present invention, the antenna is square in shape.
According to a further embodiment of the present invention there is provided a multi- frequency antenna comprising: a ground layer; a conduction layer; and a dielectric layer provided between the ground layer and the conduction layer, wherein the antenna has a first antenna portion capable of operating at a first frequency and a
According to another embodiment of the present invention, the first frequency is different from the second frequency.
According to another embodiment of the present invention, the second antenna portion forms part of the first antenna portion.
According to another embodiment of the present invention, the conduction layer is electrically connected to the ground layer.
According to another embodiment of the present invention, the conduction layer is electrically connected to the ground layer by metallic via's.
According to another embodiment of the present invention, the antenna further comprises: a capacitive element connected to the conduction layer at a feed point edge.
According to another embodiment of the present invention, the capacitive element comprises a plurality of capacitors.
According to another embodiment of the present invention, the plurality of capacitors are spaced equally along the feed point edge. According to another embodiment of the present invention, at least one of the plurality of capacitors forms part of the first antenna portion, and at least one of the plurality of capacitors forms part of the first antenna portion and the second antenna portion.
According to another embodiment of the present invention, the capacitive element is connected to the ground layer.
According to another embodiment of the present invention, the capacitive element is connected to the ground layer by metallic via's.
According to a further embodiment of the present invention there is provided a method of tuning the antenna of the present invention, comprising: adjusting the distance between the first and second elongated recess, wherein when the distance between the first and second elongated recess is increased the operating frequency of the second antenna portion is decreased.
According to a further embodiment of the present invention there is provided a method of tuning the antenna of the present invention, comprising: adjusting the width of the first and second elongated recess, wherein when the width of the first and second elongated recess is increased the operating frequency of the second antenna portion is decreased.
According to a further embodiment of the present invention there is provided a method of tuning the antenna of the present invention, comprising: adjusting the length of the first and second elongated recess, wherein when the length of the first and second elongated recess is increased the operating frequency of the second antenna portion is decreased.
DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention and as to how the same may be carried into effect reference will now be made, by way of example only, to the accompanying drawings, in which: Figures 1 illustrates a plan view of a known patch antenna; Figure 2 illustrates a side view of the patch antenna of figure 1 ; Figure 3 illustrates a perspective view of an antenna according to an embodiment of the present invention; Figure 4 illustrates a cut through of the antenna of figure 3 taken along line
AA;
Figure 5 illustrates a plot of the desired frequency response of an antenna of the present invention;
Figure 6 illustrates an impedance graph of an antenna of the present invention; antenna of the present invention when the distance ω between two elongated slots of the antenna is varied;
Figure 8 illustrates computed variations in an operating frequency of an antenna of the present invention when the width t of elongated slots of the antenna is varied;
Figure 9 illustrates computed variations in an operating frequency of an antenna of the present invention when the length I of elongated slots of the antenna is varied; Figure 10 illustrates a current density plot of an antenna of the present invention operating at a relatively low frequency; and
Figure 11 illustrates a current density plot of an antenna of the present invention operating at a relatively high frequency.
DETAILED DESCRIPTION
Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and accompanying drawings or may be learned by practice of the invention.
Figure 3 illustrates a perspective view of a patch antenna according to a preferred embodiment of the present invention. The antenna is a rectangular antenna having a ground plate 300, a separating dielectric substrate 340 and a printed conduction layer 310. The antenna also has two elongated slots 96 and 98 formed in the conduction layer 310. The two elongated slots 96 and 98 are formed substantially parallel to the non-radiating edges 320, 390 of the conduction layer 310.
One edge 350 of the conduction layer 310 is electrically connected to the ground plate 300. In one example metallic via's can be placed in respective holes formed in the dielectric layer 340 to electrically connect the edge 350 of the conduction layer 310 to the ground plate 300. Electrically connecting one edge 350 of the conduction layer 310 to the ground plate 300, effectively shorts that edge {edge 350) of the antenna to ground.
Furthermore, the conduction layer 310 is connected to a plurality of capacitors 380 located along the edge 360 of the conduction layer opposite to the edge 350. The capacitors 380 increase the edge capacitance of the patch antenna. In a preferred embodiment, each individual capacitor 380 of the plurality of capacitors 380 is connected to the conduction layer 310 and to the ground plate 300. The capacitors 380 can be connected to the ground plate 300 by metallic via's which are placed in respective holes 330 formed in the dielectric layer 340 to electrically connect the capacitors 380 to the ground plate 300.
According to the embodiment of figure 3, the capacitors 380 are located along the same edge of the conduction layer 310 as the RF feed point 370 and are distributed on either side of the RF feed point 370. In one embodiment, the capacitors are spaced equally along the edge 360 of the conduction layer 310. There is more than one capacitor 380 on each side of the feed point 370 such that current is distributed uniformly along the edge 360 of the conduction layer 310. This advantageously allows an even electromagnetic field distribution for the antenna.
The use of capacitors 380 in the antenna of the present invention increases the edge capacitance of the antenna, thus enabling a reduction of the physical length of the antenna. That is, by adding capacitors 380 to the antenna circuit, the physical length of the antenna can be reduced, while still maintaining operation of the antenna at a particular desired resonating frequency. As stated above, when the physical length of the antenna is reduced, the resonating frequency of the antenna is increased. The use of capacitors 380 increases the edge capacitance of the antenna and decreases the resonating frequency, therefore, compensating for the increase of resonating frequency experienced when the physical length of the antenna is reduced. Consequently, the use of capacitors 380 enables the physical length of the antenna to be reduced, without the resonating frequency being increased, since the capacitors 380 make the antenna look electrically longer than it is physically.
Although capacitors 380 are described above, the present invention is not limited to the use of capacitors 380. Any means for increasing the edge capacitance of the antenna, thus enabling a reduction of the physical length of the antenna can be zπseefc
Figure 4, illustrates a cross section of the antenna of figure 3, in operation, taken along line AA. A pair of radiating fields 86 and 88 are setup within the respective slots 96 and 98 as illustrated in Figure 4. The elongated slots are formed in the conduction layer 310. These elongated slot radiation fields 86, 88 result in an inner antenna portion being created, in addition to the outer antenna portion defined by the outer radiating fields 81 and 83. Namely, the area defined by the external edges of the conduction layer 310 illustrated in figure 3 forms an outer antenna portion. In addition, the smaller area defined between the edges of elongated slots 96, 98, which is hatched in figure 3, forms an inner antenna portion. In this embodiment, the inner antenna portion also forms part of the outer antenna portion.
Therefore, the antenna illustrated in figure 3 creates in operation, a small inner antenna portion within the slots 96, 98; and a large outer antenna portion. The inner antenna portion has length I and width ω, and the outer antenna portion has length L and width W. The inner antenna portion has a smaller area than the outer antenna portion. Since the inner antenna portion has a smaller area than the outer antenna portion, the inner antenna portion is capable of operating at a higher resonating frequency than the outer antenna portion.
Furthermore, at lower resonating frequencies the geometry of the elongated slots 96, 98 is such that electrically it is almost as if the elongated slots 96, 98 do not exist. Consequently, the entire antenna portion operates at the lower resonating frequencies. However, at higher resonating frequencies the geometry of the elongated slots 96, 98 becomes relevant. Consequently, only the inner antenna portion operates at the higher resonating frequencies
Thus, the advantage of forming slots 96 and 98 in the conductive layer 310 is that an antenna having a smaller inner antenna portion and a larger outer antenna portion is formed. The resultant multi-frequency antenna is able to operate at two different resonating frequencies. The outer antenna portion operates at a first resonating frequency, and the inner antenna portion operates at a second resonating frequency, the first resonating frequency being lower than the second resonating
-frequency..
In one embodiment the antenna of the present invention is capable of simultaneously operating at the first and second resonating frequencies. In another embodiment, the antenna of the present invention is capable of transmitting and receiving signals. For example, the operating frequency of the inner antenna portion could be used as the transmit frequency, and the operating frequency of the outer antenna portion could be used as the receive frequency or vice versa. Therefore, one antenna is capable of transmitting and receiving signals at different frequencies. In another embodiment, one or both of the inner and outer antenna portions could operate as transceivers, capable of transmitting and receiving signals.
The antenna of the present invention can operate at any combination of two resonating frequencies, which are spaced apart in the frequency spectrum. According to a preferred embodiment, the antenna operates at the frequencies detailed below:
1) outer antenna portion - 433 MHz, inner antenna portion - 915 MHz, or
2) outer antenna portion - 433 MHz, inner antenna portion - 868 MHz.
In one embodiment of the present invention, the dielectric layer 340 has a thickness greater than 1.6 mm. Furthermore, the RF feed point 370 is located at the edge 360 of the conduction layer 310. The antenna illustrated in figure 3 has a rectangular shape, however, it should be appreciated that other shapes of antenna are possible, for example a square or similar shape may be utilised. Some patch antennas are circular shapes.
Figure 5 illustrates the frequency response of an antenna of the present invention using a simulation package. The plot shows that the antenna is operating with the first frequency pair listed above, in which the first operating frequency at point 42 is 433 MHz, while the second operating frequency at point 44 is the 915 MHz.
The patch antenna according to an embodiment of the present invention was
In the first phase, the desired frequency response of the antenna was simulated using electro magnetic simulation software, for example, Sonnet, IE3D, Microware Studio, etc. As described previously, figure 5 shows the desired frequency response of the antenna using a relevant simulation package.
Figure 6 is a further representation of the same simulation of the antenna according to the preferred embodiment, but whereas figure 5 illustrates the frequency response, figure 6 illustrates an impedance graph.
The second phase of antenna design involves prototyping the antenna, which can be constructed for example using ordinary FR-4 PCB material. The antenna is then calibrated using the principle that the smaller the antenna, the more capacitance is needed for the antenna to function at the desired resonating frequency.
Figures 7 to 9 illustrate how adjusting the geometry of the antenna adjusts the frequency at which the antenna works.
Figure 7 illustrates the frequency variation when the width ω of the inner antenna portion (the distance between the elongated slots) is varied. The width ω is varied from 6 mm to 24 mm (14ω varies from 3 mm to 12 mm). During testing, the width W of the outer antenna portion (the conduction layer 310) is fixed at 55 mm; the length L of the outer antenna portion (the conduction layer 310) is fixed at 44 mm; the 83
length I of the elongated slots is fixed at 21 mm and the width t of the elongated slots is fixed at 1 mm.
When the width ω of the inner antenna portion is increased, the operating frequency of the inner antenna portion decreases. As can be seen from figure 7, when ω = 6 mm (34ω = 3 mm) the operating frequency of the inner antenna portion is approximately 1000 MHz. However, when ω = 24 mm (Αω = 12 mm) the operating frequency of the inner antenna portion is approximately 900 MHz.
Furthermore, in theory, variations in the width ω of the inner antenna portion should antenna portion should maintain operation at 433 MHz. In practice, as illustrated in figure 7, when ω = 6 mm (1Λω = 3 mm) the operating frequency of the outer antenna portion is approximately 460 MHz and when ω = 24 mm (ΛΛω = 12 mm) the operating frequency of the outer antenna portion is approximately 420 MHz.
Figure 8 illustrates the frequency variation when, the width t of the elongated slots is varied. The width t of the elongated slots is increased from 1 mm to 2 mm in 0.1 mm increments. During testing, the width W of the outer antenna portion (the conduction layer 310) is fixed at 55 mm; the length L of the outer antenna portion (the conduction layer 310) is fixed at 44 mm; the length I of the elongated slots is fixed at 21 mm and the width ω of the inner antenna portion is fixed at 16 mm (Vkn = 8 mm).
When the width t of the elongated slots is increased, the operating frequency of the inner antenna portion decreases. As can be seen from figure 8, when t = 1 mm, the operating frequency of the inner antenna portion is approximately 915 MHz. However, when t = 2 mm the operating frequency of the inner antenna portion is approximately 880 MHz.
As with figure 7 above, in theory, variations in the width t of the elongated slots should not materially effect the operating frequency of the outer antenna portion, the outer antenna portion should maintain operation at 433 MHz. In practice, as illustrated in figure 8, when t = 1 mm the operating frequency of the outer antenna portion is approximately 434 MHz and when t = 2 mm the" operating frequency of the outer antenna portion is approximately 430 MHz.
Figure 9 illustrates the frequency variation when the length I of the elongated slots is varied. The length I of the elongated slots is increased from 22 mm to 28 mm. During testing, the width W of the outer antenna portion (the conduction layer 310) is fixed at 55 mm; the length L of the outer antenna portion (the conduction layer 310) is fixed at 44 mm; the width t of the elongated slots is fixed at 1 mm and the width ω of the inner antenna portion is fixed at 16 mm (Αω = 8 mm).
iWherrtQsJirigtl]^^^ inner antenna portion decreases. As can be seen from figure 9, when I = 22 mm, the operating frequency of the inner antenna portion is approximately 915 MHz. However, when I = 28 mm the operating frequency of the inner antenna portion is approximately 850 MHz.
As with figures 7 and 8 above, in theory, variations in the length I of the elongated slots should not materially effect the operating frequency of the outer antenna portion, the outer antenna portion should maintain operation at 433 MHz. In practice, as illustrated in figure 9, when I = 22 mm the operating frequency of the outer antenna portion is approximately 434 MHz and when I = 28 mm the operating frequency of the outer antenna portion is approximately 420 MHz.
The deviations noted above, in the lower operating frequency of the outer antenna portion do not change significantly as the slot dimensions are altered. Consequently, operation of the outer antenna portion operating at the lower frequency is not altered significantly.
In order to change the frequency of the outer antenna portion, the width W of the outer antenna portion (the conduction layer 310) and the length L of the outer antenna portion (the conduction layer 310) may be varied. In this case the operating frequency of the outer antenna portion will deviate from 433 MHz and the operating frequency of the inner antenna portion in theory should remain constant. In a preferred embodiment of the present invention, the antenna has an outer antenna portion width W of 55 mm; an outer antenna portion length L of 44 mm; an inner antenna portion width ω of 16 mm; an elongated slot width of 1 mm; and elongated slot length I of 21 mm.
Figures 10 and 11 illustrate the current density distribution for an antenna of the present invention when the outer antenna portion is operating at the resonating frequency of 433 MHz, and when the inner antenna portion is operating at the resonating frequency of 915 MHz.
-As=ean=be-seeι^froifrfigttr:e^1:04Re=e^^ same over the entire antenna since the whole antenna is being used to resonate at the lower frequency of 433 MHz, i.e. the large outer antenna in use.
As can be seen from figure 11 the current density distribution is increased between the slots 96, 98 which define the inner antenna, when compared to the rest of the antenna. This is because the smaller inner antenna is being used to resonate at the higher frequency of 915 MHz.
Referring back to the perspective view of figure 3 it should be appreciated that the length I of the elongated slots 96, 98 is significant. If the slots are too short, the antenna does not resonate effectively on the higher frequencies. However, if the slots are too long, the antenna does not resonate effectively on the lower frequencies. The slots are designed so that the antenna is able to accommodate two resonating frequencies, spaced sufficiently apart, but both frequencies are still matched, preferable to an impedance of 50 ohms, so that only one feed point 370 exists.
It should be appreciated that the sizes of the patch antenna are variable. However, the size cannot be smaller than the size of the inner patch (i.e. whose dimensions would produce a desired higher resonating frequency), but also needs to be large enough to realise an electrically small antenna capable of resonating on the lower frequency. An antenna according to embodiments of the present invention can be of any form provided that the elongated slots 96, 98 are positioned such that an inner and an outer antenna are formed that operate at different frequencies.
Furthermore, an antenna of the present invention can be manufactured using known PCB techniques. In addition, the elongated slots can be formed for example by using chemical or copper etching.
The antenna of the present invention is able to operate off a metal surface. Furthermore, the antenna of the present invention is more efficient when placed on a
present invention has particular application in the RF tag tracking field. Specifically, containers or packages that are to be couriered or routed to a particular destination can be tracked easily, by fixing an antenna of the present invention to the metal (or other) surface of such a container. Information about the container can therefore be easily transmitted or received.
It should also be appreciated that there are plurality of different applications and fields of use for the patch antenna geometry described therein. Some of these include:
• any RF point-to-point link system;
• any RF point-to-multi-point link system;
• any RFID tag whether it is passive or an active tag;
• any RF transmitter, receiver and/or transceiver; • any sensor application with an RF link relaying data.
Those skilled in the art will appreciate that while the foregoing has described what is considered to be the best mode and, where appropriate, other modes of performing the invention, the invention should not be limited to the specific configurations and methods disclosed in this description of the preferred embodiment. Those skilled in the art will recognise that the invention has a broad range of applications in many different types of antennas, and that the embodiments may take a wide range of 2007/004283
modifications without departing from the inventive concept as defined in the appended claims.

Claims

Claims
1. A multi-frequency antenna comprising: a ground layer; a conduction layer provided with a first and second elongated recess; and a dielectric layer provided between the ground layer and the conduction layer; wherein the first and second elongated recess enable the antenna to operate as a first antenna portion having a first operating frequency and a second antenna portion having a second operating frequency different from the first operating frequency.
2. An antenna according to claim 1, wherein the second antenna portion forms part of the first antenna portion.
3. An antenna according to claim 1 or 2, wherein the conduction layer is electrically connected to the ground layer.
4. An antenna according to claim 3, wherein the conduction layer is electrically connected to the ground layer by metallic via's.
5. An antenna according to any of claims 1 to 4, further comprising: a capacitive element connected to the conduction layer at a feed point edge.
6. An antenna according to claim 5, wherein the capacitive element comprises a plurality of capacitors.
7. An antenna according to claims 6, wherein the plurality of capacitors are spaced equally along the feed point edge.
8. An antenna according to claim 6 or 7, wherein at least one of the plurality of capacitors forms part of the first antenna portion, and at least one of the plurality of capacitors forms part of the second antenna portion and the first antenna portion.
9. An antenna according to any one of claims 5 to 8, wherein the capacitive element is connected to the ground layer.
10. An antenna according to claim 9, wherein the capacitive element is connected to the ground layer by metallic via's.
11. An antenna according to any preceding claim, wherein the first and second elongated recesses are provided substantially parallel to each other.
12. An antenna according to any preceding claim, wherein the first and second elongated-recesses-are-prΘvided-substantiatiy-pafalleHo-a-norFratiiatiπg-edge'ot'the' conduction layer.
13. An antenna according to any preceding claim, wherein an area defined by outside edges of the conduction layer forms the first antenna portion, and an area defined between the first and second elongated recesses forms the second antenna portion.
14. An antenna according to any preceding claim, wherein the first frequency is less than the second frequency.
15. An antenna according to any preceding claim, wherein one of the first antenna portion and the second antenna portion is capable of receiving signals, and the other of the first antenna portion and the second antenna portion is capable of transmitting signals.
16. An antenna according to any one of claims 1 to 14, wherein both the first antenna portion and the second antenna portion are capable of transmitting and receiving signals.
17. An antenna according to any preceding claim, wherein the first antenna portion and the second antenna portion are capable of operating simultaneously.
18. An antenna according to any preceding claim, wherein the first antenna portion is arranged to operate at a frequency in a range of 420 MHz to 460 MHz.
19. An antenna according to any preceding claim, wherein the first antenna portion is arranged to operate at a frequency of substantially 433 MHz.
20. An antenna according to any preceding claim, wherein the second antenna portion is arranged to operate at a frequency in a range of 850 MHz to 1000 MHz.
21. An antenna according to any preceding claim, wherein the second antenna :pl^toidsiaϊcaιτgRcttcra^
22. An antenna according to any preceding claim, wherein the first and second frequencies are matched to an impedance of 50 ohms.
23. An antenna according to any preceding claim, wherein the length I of the first and second elongated recesses is in a range of 21 mm to 28 mm.
24. An antenna according to any preceding claim, wherein the length I of the first and second elongated recesses is substantially 21 mm.
25. An antenna according to any preceding claim, wherein the distance ω between the first and second elongated recesses is in a range of 6 mm to 24 mm.
26. An antenna according to any preceding claim, wherein the distance ω between the first and second elongated recesses is substantially 16 mm.
27. An antenna according to any preceding claim, wherein the width t of each of the first and second elongated recesses is in a range of 1 mm to 2 mm.
28. An antenna according to any preceding claim, wherein the width t of each of the first and second elongated recesses is substantially 1 mm.
29. An antenna according to any preceding claim, wherein the width W of the conduction layer is in a range of 50 mm to 60 mm.
30. An antenna according to any preceding claim, wherein the width W of the conduction layer is substantially 55 mm.
31. An antenna according to any preceding claim, wherein the length L of the conduction layer is in a range of 40 mm to 50 mm.
32. An antenna according to any preceding claim, wherein the length L of the .conduction-la-yer-is-substaFvtially-44-mm^
33. An antenna according to any preceding claim, wherein the dielectric layer has a thickness greater than 1.6 mm.
34. An antenna according to any preceding claim, wherein the antenna is capable of operating off a metal surface.
35. An antenna according to any preceding claim, wherein the antenna is a patch antenna.
36. An antenna according to any preceding claim, wherein the antenna is used as part of a radio frequency tracking tag.
37. An antenna according to any preceding claim, wherein the ground layer is electrically grounded.
38. An antenna according to any preceding claim, wherein the antenna is square in shape.
39. An multi-frequency antenna comprising: a ground layer; a conduction layer; and a dielectric layer provided between the ground layer and the conduction layer, wherein the antenna has a first antenna portion capable of operating at a first frequency and a second antenna portion capable of operating at a second frequency.
40. An antenna according to claim 39, wherein the first frequency is different from the second frequency.
41. An antenna according to claim 39 or 40, wherein the second antenna portion forms part of the first antenna portion.
42. An antenna according to any one of claims 39 to 41, wherein the conduction layer is electrically connected to the ground layer.
43. An antenna according to claim 42, wherein the conduction layer is electrically connected to the ground layer by metallic via's.
44. An antenna according to any of claims 39 to 43, further comprising: a capacitive element connected to the conduction layer at a feed point edge.
45. An antenna according to claim 44, wherein the capacitive element comprises a plurality of capacitors.
46. An antenna according to claims 45, wherein the plurality of capacitors are spaced equally along the feed point edge.
47. An antenna according to claim 45 or 46, wherein at least one of the plurality of capacitors forms part of the first antenna portion, and at least one of the plurality of capacitors forms part of the first antenna portion and the second antenna portion.
48. An antenna according to any one of claims 44 to 47, wherein the capacitive element is connected to the ground layer.
49. An antenna according to claim 48, wherein the capacitive element is connected to the ground layer by metallic via's.
50. A method of tuning the antenna of one of claims 1 to 38, comprising: adjusting the distance between the first and second elongated recess, wherein when the distance between the first and second elongated recess is increased the operating frequency of the second antenna portion is decreased.
51. A method of tuning the antenna of one of claims 1 to 38, comprising: adjusting the width of the first and second elongated recess,
the operating frequency of the second antenna portion is decreased.
52. A method of tuning the antenna of one of claims 1 to 38, comprising: adjusting the length of the first and second elongated recess, wherein when the length of the first and second elongated recess is increased the operating frequency of the second antenna portion is decreased.
53. An antenna as hereinbefore described and with reference to any one of figures 3 and 4.
EP07824512A 2006-11-10 2007-11-09 Multi-frequency antenna Withdrawn EP2089933A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB0622469.5A GB0622469D0 (en) 2006-11-10 2006-11-10 Multi-frequency antenna
PCT/GB2007/004283 WO2008056159A1 (en) 2006-11-10 2007-11-09 Multi-frequency antenna

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EP2089933A1 true EP2089933A1 (en) 2009-08-19

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WO (1) WO2008056159A1 (en)

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US9136594B2 (en) 2009-08-20 2015-09-15 Qualcomm Incorporated Compact multi-band planar inverted F antenna
US10476142B2 (en) 2016-12-21 2019-11-12 Cts Corporation Radio frequency antenna with granular or powder insulating material and method of making the same
CN209016267U (en) * 2018-11-14 2019-06-21 深圳Tcl新技术有限公司 Double frequency vertical polarized antenna and television set

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FI113212B (en) * 1997-07-08 2004-03-15 Nokia Corp Dual resonant antenna design for multiple frequency ranges
FR2772517B1 (en) * 1997-12-11 2000-01-07 Alsthom Cge Alcatel MULTIFREQUENCY ANTENNA MADE ACCORDING TO MICRO-TAPE TECHNIQUE AND DEVICE INCLUDING THIS ANTENNA
WO2000052783A1 (en) * 1999-02-27 2000-09-08 Rangestar International Corporation Broadband antenna assembly of matching circuitry and ground plane conductive radiating element
GB0105440D0 (en) * 2001-03-06 2001-04-25 Koninkl Philips Electronics Nv Antenna arrangement

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