Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
  • H01Q19/28—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using a secondary device in the form of two or more substantially straight conductive elements
  • H01Q19/30—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using a secondary device in the form of two or more substantially straight conductive elements the primary active element being centre-fed and substantially straight, e.g. Yagi antenna
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/0006—Particular feeding systems
  • H01Q21/0037—Particular feeding systems linear waveguide fed arrays
• • 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
• • 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
  • H01Q11/00—Electrically-long antennas having dimensions more than twice the shortest operating wavelength and consisting of conductive active radiating elements
  • H01Q11/02—Non-resonant antennas, e.g. travelling-wave antenna
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
  • H01Q21/061—Two dimensional planar arrays
  • H01Q21/068—Two dimensional planar arrays using parallel coplanar travelling wave or leaky wave aerial units

Definitions

• the invention relates to antenna arrays.
• the invention relates to millimetre- wave chain antenna arrays and power distribution networks for the arrays.
• Chain antennas related to grid antennas, are known to exhibit a moderate gain even with a single chain. Gain can be further increased by forming chains into an array. In a fixed- beam array, the power is distributed equally from one point into all chain elements with a feed network. Conventionally, this has been done using microstrip lines and T-junctions or Wilkinson power dividers.
• the antenna comprises a branched open microstrip feed network and a radiating structure comprising several elongated chain antenna sub- arrays arranged side-by-side and parallel to each other, thereby forming a two-dimensional antenna array.
• Each of the sub-arrays is coupled at its one end to one branch of the feed network for excitation of the sub-array. Problems with this kind of arrangement include beam tilting from the desired broadside direction and beam scanning with frequency. Also high gain is difficult to achieve due to losses in the microstrip line feed network
• one of the main challenges at millimetre-wave frequencies is to achieve high antenna gain (and efficiency) for large antenna arrays due to losses in the feed network that usually consists of microstrip lines, coplanar waveguides, striplines or other open transmission lines, like in the abovementioned publication. It is known that the feed network losses can be reduced using e.g. substrate-integrated waveguides (SIW).
• SIW substrate-integrated waveguides
• the aim is achieved by the antenna array having the features of claim 1.
• a traveling-wave antenna array comprising a feed network, a radiating structure comprising at least four elongated grid antenna sub-arrays arranged side-by-side and parallel to each other so as to form a two-dimensional antenna array, and a plurality of interface elements coupled to the grid antenna sub-arrays and to the waveguide feed network for exciting each of the grid antenna sub-arrays.
• the feed network comprises a waveguide network which is at least partly arranged below the radiating structure, and there are at least two of said interface elements for each of the elongated grid antenna sub-arrays for exciting the sub-arrays simultaneously at at least two points.
• the advantages of the present antenna array design include that total losses remain relatively low even when the antenna array is scaled up in size to a 2x4 or even larger antenna array, and high antenna gain is achieved. At the same time the whole a sub-antenna array can be efficiently excited due to the plurality of excitation points for each sub- antenna.
• the invention can be used to replace lens, reflector, horn-or other heavy and bulky directive antennas at millimetre-wave applications with low-cost directive planar array antennas.
• the invention can be used as an alternative to conventional lens or reflector antennas in millimetre-wave point-to-point radio links.
• the present design allows for exciting a large amount of antennas and is therefore scalable up in size.
• the present invention is most suitable for centimetre and millimetre wave applications at the frequency range of 3-300 GHz, in particular 30-300 GHz, but can be used also at higher frequencies.
• the proposed antenna could be used in emerging wireless millimetre-wave applications such as millimetre wave identification (MMID), Wireless high definition (HD), Wireless Personal/Local Area Networks (WPAN/WLAN) and point-to-point radio links.
• MMID millimetre wave identification
• HD Wireless high definition
• WPAN/WLAN Wireless Personal/Local Area Networks
• point-to-point radio links point-to-point radio links.
• Fig. la shows a single chain antenna.
• Fig. lb shows a "vertically" up-scaled 4-chain antenna array.
• Fig. lc shows a "vertically” and “horizontally” up-scaled 4-chain antenna array.
• Fig. 2 shows a "vertically" up-scaled 4-chain antenna array with feed network according to one embodiment of the invention.
• Fig. 3 shows a "vertically" up-scaled 8-chain antenna array with feed network according to one embodiment of the invention.
• Fig. 4 shows a "horizontally” and “vertically” up-scaled 8-chain antenna array with feed network according to one embodiment of the invention.
• Fig. 5 shows a "vertically” up-scaled 4-chain antenna array with antenna sub-arrays extending into different directions from their feed points.
• Fig. 6 shows a cross-sectional view of a SIW feed network structure integrated with a chain antenna array according to one embodiment of the invention.
• the idea of the invention is to utilize a highly-efficient antenna radiator(s) with a low-loss feeding network to obtain high efficiency for the whole antenna array.
• a chain antenna array with a SIW feed network arranged with respect to each other according to the invention is described below in detail by way of example.
• the elongated antenna sub-arrays 10 may comprise chain antennas, which typically have two symmetrically meandering conductors 11a, l ib, thus forming chain-like formation.
• the length L of each chain element is ⁇ /2 and the maximum distance D between the meanders is ⁇ , i.e. the wavelength used.
• the meanders are parallel and close to each other.
• a feed point 12 which is electrically connected to both meandering conductors 11a, 1 lb for exciting the antenna.
• Fig. lb shows a vertically expanded grid antenna having four chain antennas sub-arrays 10a- lOd according to Fig. 1 arranged in parallel side-by-side configuration. In the shown configuration, there is one feed point at each of the sub-arrays at corresponding positions of the chain.
• each of the sub-arrays lOOa-lOOd is a single continuous grid antenna section having more than one (four shown) feed points at each sub-array.
• the spacing of the feed points equals to two chain elements, but the spacing could be a multiple of two as well.
• the spacing of the feed points can be chosen freely to obtain a desired illumination profile for the antenna array. For example, more narrow spacing at the center area than at the edge could be used for targeting as lower side lobes in the radiation pattern.
• each of the sub-arrays comprises a plurality of separated chain antennas and there is at least one interface element coupled to each grid antenna section.
• This configuration is therefore similar to that shown in Fig. lc, but the chains lOOa-lOOd are not continuous but disconnected at least at some point between any two feed points.
• the number of side-by-side sub-arrays may be for example 4 - 100, in particular 4 - 24.
• the number of feed points in each sub-arrays may be for example 2 - 50, in particular 2 - 12. In one embodiment, the number of side-by-side sub-arrays is 8 or more and the number of feed points 4 or more.
• the antenna sub-arrays may be other types of meander lines or closed-loop grid antennas.
• the dielectric material of the antenna substrate can be partly removed in order to decrease the effective permittivity of the substrate to obtain wider bandwidth and higher gain for the antenna array.
• the waveguide feed network comprises an elongated interface cavity 24; 34, which is oriented at an angle, preferably perpendicularly, to the elongated grid antenna sub-arrays 20a-20d; 30a-30h.
• the waveguide feed network comprises an elongated interface cavity 24; 34, which is oriented at an angle, preferably perpendicularly, to the elongated grid antenna sub-arrays 20a-20d; 30a-30h.
• the number of interface elements and chain antennas is 8.
• Figs 2 and 3 can be easily scaled up so as to form a larger high-gain antenna array.
• This can be achieved by branching the feed network so that at least two elongated interface cavities are formed.
• Fig. 4 shows an example of such array.
• the array comprises a multiply branched feed network comprising four H-shaped portions in which the vertical branches of "H" form interface cavities each having four interface elements of the antenna chains coupled to.
• the four H- shaped portions are arranged in a 2-by-2 matrix so that an even grid of feed points to the antenna chains above the feed network is formed.
• the matrix can be also larger n-by-m matrix, where n and m are integers selected from a group of e.g., 2...100.
• Grid antenna sub-arrays are similar to each other and are located symmetrically adjacent to each other. They extend from the interface cavities (feed points) to into the same direction.
• the sub-arrays extend from the interface elements alternatingly into opposite directions. This kind of arrangement may be produced with a similar feed network as discussed above by only modification of the conductor pattern of the antenna. If the chains are extended into opposite directions, the spacing of the chains can be reduced from one wavelength into a half wavelength. A larger antenna array can be excited from a single SIW.
• the feed network and antenna pattern may be modified correspondingly. For example, it may be preferably to make an antenna where the distance between neighboring interface elements corresponds to half of the operating wavelength of the antenna array.
• the waveguide feed network is a substrate-integrated waveguide (SIW) feed network, although it can be realized by any know waveguide technology.
• SIW substrate-integrated waveguide
• An advantage of using a waveguide, in particular SIW, network is that the feed network losses are significantly reduced compared with a microstrip line or other open transmission line.
• the SlW-to-chain-antenna-array transition is implemented by providing a plurality of interface elements formed by electrically conducting probes from the antenna sub-arrays to a single SIW cavity.
• This kind of transition between the waveguide and the radiating portion of the antenna enables scaling of the structure into a large antenna array as discussed above without sacrificing too much in efficiency.
• the excitation from SIW to antenna can be done using conducting probes, as described above, or alternatively by coupling apertures in the upper conductor layer of the SIW.
• the interface elements may comprise voids or other channels allowing radiation power to pass from the feed network to the radiating structure.
• the SIW feed network and the antenna pattern may be integrated in to a single
• the substrate may be for example a low temperature co-fired ceramic (LTCC) substrate, liquid crystal polymer (LCP), or a standard printed circuit board (PCB) substrate.
• LTCC low temperature co-fired ceramic
• LCP liquid crystal polymer
• PCB standard printed circuit board
• the dielectric material inside the SIW can be partly removed in order to decrease the dielectric losses of the SIW and to improve the antenna efficiency and gain.
• the interface elements comprise probes in electrical connection with the grid antenna sub-arrays and extending into a wave-guiding cavity of the waveguide feed network for coupling to the waves in the wave-guiding cavity.
• the probes can be implemented with the same technology as used for forming the conductive boundary vias of the SIW waveguides.
• the vias can be connected to the antenna pattern by T-junctions.
• the multilayer structure comprises
• top conductor layer 63 on the waveguide portion 60 and forming a waveguide top boundary, the top and bottom conductor layers 62, 63 being connected to the boundary vias 64,
• separating layer 69 on top of the top conductor layer 63, the probe vias 67 extending also through the separating layer 69,
• conductive antenna layer 68 connected with the probe vias and patterned so as to form the radiating portion of the antenna.
• the probes are equal in lengths. According to an alternative embodiment, at least two of the probes extend to different depths into the wave-guiding cavity. This embodiment allows for modifying the amplitude distribution in the antenna array and hence the radiation pattern of the antenna. By modifying the amplitude distribution in the antenna array, the radiation pattern can be modified. Coupling strength from the SIW to the antenna is in relation to the probe depth.
• a low side-lobe level is very important.
• the low side-lobe level can be achieved by tapering the amplitude distribution in the antenna array.
• less power is delivered to the edges of the array while more power is fed to the center of the array. Therefore, in one advantageous embodiment, at least one, preferably a plurality of probes at the center of the array are longer than those more distant from the center.
• a transition from the SIW structure to a microstrip line or other transmission line known per se can be used in the array input in order to integrate the antenna with millimetre-wave circuits into a single radio module.

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• Variable-Direction Aerials And Aerial Arrays (AREA)
• Waveguide Aerials (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

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Family Applications (1)

Country Status (2)

Cited By (2)

Citations (3)

• 2012
  • 2012-03-20 FI FI20125308A patent/FI20125308A7/fi not_active Application Discontinuation
• 2013
  • 2013-03-15 WO PCT/FI2013/050303 patent/WO2013140036A1/fr not_active Ceased

Patent Citations (3)

Non-Patent Citations (3)

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