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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
  • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
  • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
  • H01Q1/242—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use
  • H01Q1/243—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use with built-in antennas
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
  • H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
• • 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
• • 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
  • H01Q5/314—Individual or coupled radiating elements, each element being fed in an unspecified way using frequency dependent circuits or components, e.g. trap circuits or capacitors
  • H01Q5/328—Individual or coupled radiating elements, each element being fed in an unspecified way using frequency dependent circuits or components, e.g. trap circuits or capacitors between a radiating element and ground
• • 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
  • H01Q5/378—Combination of fed elements with parasitic elements

Definitions

• the invention relates to a very small-sized multiband antenna based on a dielectric antenna component.
• a dielectric substrate for the antenna's radiator is one way to implement a very small-sized antenna.
• Such antennas are of benefit to the small-sized mobile terminals with several different activities.
• the GPS positioning Global Positioning System
• Bluetooth data transfer are common activities.
• Fig. 1 shows a dielectric antenna component and a whole antenna known from the publication EP 1761971.
• the antenna component comprises an elongated substrate 1 10 and two radiating antenna elements symmetrically on its surface.
• the first antenna element 121 covers a part of the upper surface of the substrate and the first head surface of the substrate.
• the second antenna element 122 covers another part of the upper surface of the substrate and the second head surface of the substrate.
• the elements continue slightly to the lower surface of the substrate for connection of the component.
• the slot extends here diagonally from one side surface of the substrate to the other.
• the antenna component is on the circuit board PCB of a radio device with the lower surface against the circuit board.
• the first antenna element 121 connects to the antenna feed conductor 150 at the first end of the component, in a corner of its lower surface, which point is the feed point FP of the antenna.
• the first antenna element connects to the ground plane GND in the opposite corner of the lower surface at said end.
• the second antenna element 122 connects to the ground conductor 140, which is an extension of the ground plane GND, the connection being as long as the width of the lower surface.
• Both radiating elements form, together with the substrate, each other and the ground plane, a quarter-wave resonator, which resonators have the same resonance frequency.
• the antenna is tuned by shaping the ground plane and by choosing the width of the slot SLT between the elements. Reducing the width of the slot lowers the natural frequency of the antenna.
• the width and length of the ground conductor 140 affect directly the electric length of the second element and thus the natural frequency of the whole antenna, for which reason the ground conductor functions as a tuning element of the antenna.
• the distance s also has an effect on the antenna impedance, for which reason the antenna can be matched by finding the optimal distance of the ground plane from the long side of the chip component.
• the dimensions of the component of a Bluetooth antenna operating in the frequency range of 2.4 GHz can be 2x2x7 mm 3 .
• an antenna component which is in principle like the one in Fig. 1 , however with the difference that the substrate is of a basic material used in the semiconductor technique, such as gallium-arsenide. In this case a yet smaller size than the one mentioned above is achieved for the antenna.
• the semiconductor chip is so thin that it requires a sup- port layer in the antenna component.
• the antennas like the ones described above have one band, for which reason they are out of the question, when at least two separate operating bands are desired for the antenna.
• Fig. 2 shows a dielectric antenna component known from the publication EP 2022140, with which component a dualband antenna can be implemented.
• This antenna component seen from above and sideways, is presented in Fig. 2.
• Two partial antennas belong to the whole antenna with the ground arrangement.
• the first partial antenna comprises the first 221 and second 222 antenna element, and the second partial antenna comprises the third antenna element 223.
• the lower operating band of the whole antenna structure is implemented by the first partial antenna, and the upper operating band by the second partial antenna.
• the partial antennas have a united substrate 210, which is divided to the substrate of the first partial antenna, or the first partial substrate, and the substrate of the second partial antenna, or the second partial substrate.
• the partial substrates are separated from each other by three holes HL1 , HL2, HL3 extending vertically through the substrate and by the transverse groove CH on the upper and lower surfaces of the substrate at the holes.
• the first element 221 of the first partial antenna covers one portion of the upper surface of the first partial substrate and extends through said holes a bit on the side of the lower surface of the substrate to constitute a contact pad. This contact pad is the shared feed point FP of the partial antennas.
• the second antenna ele- ment 222 covers another portion of the upper surface of the first partial substrate and extends through its head surface a bit on the side of the lower surface of the substrate to constitute contact pads in the corners of the lower surface.
• the second antenna element is connected to the ground plane GND through these contact pads.
• the second radiating element is then parasitic; it gets its feed electromag- netically over the narrow slot SLT between the elements.
• the radiator of the second partial antenna, or the third antenna element 223, covers at least partly the upper surface and the outer head surface of the second partial substrate.
• the second partial antenna gets its feed galvanically through the first antenna element 221 and an intermediate conductor 232.
• the intermediate conductor is located on one side surface of the substrate 210, which is coated by conductive material so that the ends of the first and third antenna element, which are face to face, become coupled to each other.
• the intermediate conductor 232 goes round the end of said groove CH on the upper surface thus forming a U- shaped bend.
• a relatively small-sized dualband antenna can be achieved by means of the solution according to Fig. 2; the dimensions of the antenna component are e.g. 3x4x15 mm 3 .
• An object of the invention is to reduce said disadvantages related to prior art.
• An antenna according to the invention is characterized by what is set forth in the independent claim 1.
• the basic idea of the invention is as follows: An antenna component with dielectric substrate and two radiators on its surface is used, which radiators extend towards each other from the opposite ends of the substrate. At an end of the substrate, the first radiator is connected to the antenna's feed conductor and the ground. The second radiator is parasitic, and it is coupled from two points to the ground at the opposite end of the substrate. These two ground couplings take place through se- rial resonance circuits with different natural frequency to constitute two operating bands for the antenna.
• An advantage of the invention is that a dualband antenna can be implemented as very small-sized. This is due to the fact that the antenna's basic component does not have to be a dualband one, in which case it can be made very tiny. Secondly, also the structural parts of said resonance circuits are very tiny. Another advantage of the invention is that the efficiency of an antenna according to it is good in both bands, also in the band of the GPS system. This is due to the fact that the volume of the whole substrate is utilized in both operating bands. A further advan- tage of the invention is that an antenna according to it is simple and relatively cheap to produce.
• Fig. 1 presents an example of the dielectric antenna according to prior art
• Fig. 2 presents another example of the dielectric antenna according to prior art
• Fig. 3 presents the principle of the structure of the antenna according to the invention
• Fig. 4 presents the operating bands of the antenna according to Fig. 3
• Fig. 5 presents a practical example of the antenna according to the invention
• Fig. 6 presents another example of the antenna according to the invention
• Fig. 7 presents an example of the band characteristics of the antenna according to the invention.
• Fig. 8 presents an example of the efficiency of the antenna according to the invention.
• Figs. 3 and 4 show the principle of the antenna according to the invention.
• Fig. 3 and 4 show the principle of the antenna according to the invention.
• the antenna comprises two radiating elements: the basic element 321 and parasitic element 322. These elements are at least largely on the same plane so that a slot SLT remains between them, over which slot the elements have an electromagnetic coupling CPL with each other.
• the basic element 321 there is the feed point FP of the antenna, from which point it connects galvanically to the antenna port AP of the radio device through the feed conductor, and a short-circuit point SP, from which the basic element connects galvanically to the ground plane GND. Seen from the slot between the elements, the feed point and short-circuit point are located at the opposite end of the basic element.
• the parasitic element 322 is coupled to the ground plane from two points, from the first G1 and second G2 ground- ing point. Seen from the slot between the elements, these points are located at the opposite end of the parasitic element.
• the grounding couplings are reactive: between the first grounding point G1 and the ground plane there is a first resonance circuit 341 , and between the second grounding point G2 and the ground plane there is a second resonance circuit 342.
• the impedance of each resonance circuit is very low at a certain frequency. In the simplest form the resonance circuits are then serial resonance circuits like the ones in Fig.
• the first resonance circuit 341 includes in series a first capacitive element C1 and a first inductive element L1
• the second resonance circuit 342 includes in series a second capacitive element C2 and a second inductive element L2.
• the parasitic element 322 is in practice shorted to the ground plane GND from the first grounding point G1. In this case also the whole antenna is in resonance and radiates well.
• the lower operating band in Fig. 4 is located at the feed frequency f O i in question.
• the parasitic element is in practice shorted to the ground plane from the second grounding point G2.
• the whole antenna is in resonance and radiates well.
• the other operating band of the antenna the upper operating band in Fig. 4 is located at the feed frequency f O2 in question.
• the locations of the operating bands are affected, in addition to the natural frequencies of the resonance circuits, by i.a. the size of the radiating elements and the width and length of the slot between them.
• the antenna comprises the antenna component 501 , the resonance cir- cuits C51 , L51 and C52, L52 and the ground plane GND.
• the antenna is implemented on the circuit board PCB of a radio device, the ground plane being of conductive coating of the board.
• the antenna component 501 comprises a substrate 510 and two radiating elements on its surface: the basic element and parasitic ele- ment.
• the substrate has the first and second end, the first and second head surface corresponding to those ends and the upper and lower surface, the lower surface being against the circuit board PCB.
• An 'end' of the substrate and similarly of the whole antenna component means its part, which borders on its head surface and is relatively short compared with the substrate length.
• the basic element 521 covers a part of the upper surface of the substrate and the first head surface of the substrate.
• the parasitic element 522 covers another part of the upper surface of the substrate and the second head surface of the substrate.
• a slot SLT remains between the elements on the upper surface, over which slot the elements have an electromagnetic coupling with each other. The parasitic element gets its feed through this coupling, and in addition the coupling increases the electric size of the elements, when it is relatively strong.
• the basic element 521 continues through the first head surface to the lower surface of the substrate. In a corner of the lower surface at the first end of the antenna component there is the feed point FP of the antenna, from which point the basic element is connected to the antenna port of the radio device. In the second corner of the lower surface at the first end of the antenna component there is the short-circuit point SP, from which the basic element is connected to the ground plane GND.
• the parasitic element 522 continues through the second head surface to the lower surface of the substrate. In the opposite corners of the lower surface at the second end of the antenna component there are the first G1 and second G2 grounding point.
• the parasitic element is coupled from the first grounding point G1 to the ground plane GND through the first resonance circuit, which circuit includes in series the first capacitor C51 and the first coil L51.
• the parasitic element is coupled from the second grounding point G2 to the ground plane through the second resonance circuit, which circuit includes in series the second capacitor C52 and the second coil L52.
• the capacitive and inductive elements mentioned in the description of Fig. 3 are then discrete chip components in this example.
• the antenna component 501 has only one useful resonance frequency.
• the antenna is made to resonate at two intended and clearly distinct frequencies, in which case the antenna is provided with two operat- ing bands.
• the electric equivalent circuit of the antenna component and the resonance circuits constitute a wholeness, in which e.g. the capacitance values are higher than the capacitances of the capacitors C51 and C52.
• Fig. 6 presents as magnified another example of the antenna according to the invention.
• the antenna comprises a dielectric antenna component 601 with the basic and parasitic element and two serial resonance circuits C61 , L61 and C62, L62 as in Fig. 5.
• the difference in respect of Fig. 5 is that now the above-mentioned parts have been mounted on a small dielectric auxiliary board 680, which constitutes an integrated antenna module.
• This module again is mounted on the circuit board PCB of a radio device, on which the ground plane GND of the antenna is.
• the feed and short-circuit of the basic element are carried out through the vias in the auxiliary board from the certain points FP' and SP' on the circuit board PCB. Similarly the one ends of the resonance circuits are connected to the ground plane through the vias in the auxiliary board.
• the second inductive element L62 is not a discrete component but a narrow strip conductor on the surface of the auxiliary board 680. Also a discrete capacitor could be replaced by conductive coating of the dielectric board so that there would be a certain capacitance between two strip con- ductors.
• Fig. 7 presents an example of the band characteristics of an antenna according to the invention.
• the substrate of the antenna component is of ceramic material, the dielectric coefficient of which is about 35.
• the substrate's length is 3.2 mm, width 1.6 mm and height 1.1 mm.
• the distance s, or the distance of the antenna com- ponent from the ground plane in transverse direction, is 6.2 mm.
• the capacitance is 2.2 pF and the inductance is 4.3 nH
• the capacitance is 1.1 pF and the inductance about 2 nH.
• the latter is implemented by a strip conductor and the other reactances by chip components.
• the structure comprises a 2.2 pF matching capacitor between the feed point FP and the ground plane.
• the antenna has been designed for the GPS and Bluetooth systems. GPS uses a narrow band around the frequency 1575420000 Hz, and the Bluetooth band is 2400-2483.5 MHz.
• the curve shows the fluctuation of the reflection coefficient S1 1 as a function of frequency.
• the lower the reflection coefficient the better the antenna has been matched and functions as a radiator and a receiver of radiation. It is seen from the curve that the reflection coefficient is good in the middle bands, about the value - 20 dB, and also that the Bluetooth-band is wide enough.
• the impedance measurement shows that in the middle frequency of the GPS the antenna impedance is 50,2 ⁇ / -1 1 °. In the middle range of the Bluetooth band the impedance is about 53 ⁇ , changing from slightly capacitive to slightly inductive inside that range. Thus the matching is very good.
• Fig. 8 shows the efficiency of the antenna according to the invention, the reflection coefficient of which is in Fig. 7, in free space as a function of frequency.
• Curve 81 shows that around the GPS frequency the efficiency is about -2.3 dB, which is a very good value.
• Curve 82 shows that in the middle range of the Bluetooth band the efficiency is a little over -3 dB and deteriorates to the value of about -4 dB, when moving to the boundaries of the band.
• a dielectric antenna according to the invention has been described above. In details, its way of implementation can differ from those presented.
• the width and shape of the slot between the radiating elements can vary.
• the substrate of the antenna component can also be of some material used in the semiconductor technique, such as silicon or gallium arsenide. In this case the substrate becomes very thin, for which reason the radiating elements are wholly on its upper surface and the electric connections of the elements to the surroundings are made by thin wires.
• the inventive idea can be applied in different ways within the scope set by the independent claim 1.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Waveguide Aerials (AREA)

Applications Claiming Priority (2)

Publications (1)

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Cited By (1)

Citations (5)

• 2009
  • 2009-07-06 FI FI20095763A patent/FI20095763A/fi unknown
• 2010
  • 2010-06-22 WO PCT/FI2010/050533 patent/WO2011004062A1/en active Application Filing

Patent Citations (5)

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