Patent Grant
10971824
This application is a § 371 National Phase of PCT/EP2017/074865, filed Sep. 29, 2017, the entirety of which is incorporated by reference and which claims priority to European Patent Application No. 16 191 928.7, filed Sep. 30, 2016.
The present application relates to antenna elements and to an array of antenna elements formed by an arrangement of antenna elements. More particularly, though not exclusively, it relates to antenna elements suitable for manufacture using surface mount soldering process techniques.
Wireless communication using radio waves as well as remote sensing using radio waves use electromagnetic waves of a dedicated frequency spectrum. For applications such as high data-rate communication or high-resolution remote sensing, electromagnetic waves of the so-called millimeter-wave frequency spectrum can be used advantageously. Whereas the term millimeter waves typically refers to frequencies in the range between 30 GHz and 300 GHz, in the context of this document the term is used for frequencies above 6 GHz, as it is sometimes done in the context of 5G, the fifth generation of mobile communication, in contrast to the classical mobile communication frequencies in the microwave range between 0.4 and 6 GHz.
Depending on assignments of regulatory bodies and technological constraints, frequencies in the so-called 60 GHz band, covering 57 GHz to 64 GHz approximately, are widely used for wireless communication with high data rate within the so-called “WiGig” standard (also known as “802.11ad” standard).
Other frequency bands and standards exist, and more are expected in the future.
Wireless communication systems, as well as many remote sensing systems, need both a transmitter and a receiver for electromagnetic waves. Both transmitter and receiver contain, at the interface between electronic circuitry and free space, an antenna in order to convert propagating electromagnetic waves from free space into guided waves—or voltages and currents—in the electronic circuitry, and vice versa. Thus, an antenna is characterized by an interface towards free space and an interface for a transmission line.
The antenna as a passive converter between the propagating electromagnetic waves from free space and the guided wave is electrically characterized by its dissipative properties (as in any passive device, some electromagnetic energy is converted to heat by conductive loss and dielectric loss) and by its behavior in the electric network. The dissipative properties are described by the term efficiency, relating the power lost to heat to the power passing through the antenna. Its frequency-dependent complex impedance describes the behavior of the antenna in the electric network best. Often relating this impedance to a typical feed transmission line characteristic impedance (of, for example, 50 Ohms), a voltage wave reflection coefficient can be defined. A small reflection coefficient means most power passes through the antenna. Thus, in a practical application, at all frequencies of operation the antenna needs to offer a small reflection coefficient to the feed power. This defines the antenna impedance bandwidth.
Other requirements for the antenna can be defined and depend on the respective application. For example, mobile user equipment for wireless communication needs antennas which are physically small, compact and of low weight. These antennas need to integrate smoothly into the wireless device. The antenna frequency bandwidth must match the application and efficiency must be high. As always, the possibility of cost effective manufacture and efficient system integration is required.
In previously disclosed literature, several circuit-board integrated antennas were proposed. Specifically, a stacked patch antenna was proposed in S. Brebels, K. Khalaf, G. Mangraviti, K. Vaesen, M. Libois, B. Parvais, V. Vidojkovic, V. Szortyka, A. Bourdoux, P. Wambacq, C. Soens, W. van Thillo, in “60-GHz CMOS TX/RX Chipset on Organic Packages with Integrated Phased-Array Antennas,” European Conference on Antennas and Propagation (EuCAP), Davos, Switzerland, April 2016; a mesh-grid patch antenna was proposed in W. Hong, K. Baek, Y. G. Kim, Y. Lee, B. Kim, “mm Wave Phased-Array with Hemispheric Coverage for 5th Generation Cellular Handsets,” European Conference on Antennas and Propagation (EuCAP), The Hague, Netherlands, April 2014; and variants of a Yagi-Uda antenna were proposed in W. Hong, S.-T. Ko, Y. Lee, K.-H. Baek, “Compact 28 GHz Antenna Array with Full Polarization Flexibility under Yaw, Pitch, Roll Motions,” European Conference on Antennas and Propagation (EuCAP), Lisbon, Portugal, April 2015.
All these antennas suffer from low efficiency (typically, roughly 50% of power passing through the antenna is converted to heat) and high cost (relatively thick circuit board material needed for the stacked patch is expensive as it is based on PTFE-based plastic, multi-layer circuit boards are expensive to manufacture, sophisticated metallic connections through the circuit board are expensive to manufacture).
The present disclosure provides an antenna element combining characteristics such as large frequency bandwidth, high efficiency, compactness, ease of integration with conventional electronic circuit and packaging technologies, and possibly low cost, for applications at millimeter-wave frequency.
The antenna element according to the present disclosure comprises a circuit board with a transmission line, the transmission line comprising at least a first conductor and a second conductor. In one embodiment, the transmission line can be a planar transmission line on the circuit board, comprising a metallic signal trace and a metallic ground trace and can connect the antenna to electronic circuitry of the transmitter or the receiver. The planar transmission line can be of well-known type, such as micro-strip line or co-planar waveguide. The characteristic impedance of the planar transmission line can be, for example, 50 Ohm.
The antenna element according to the present disclosure further comprises a separate, 3-dimensional, (in contrast to patch antennas, where additional structures are integral parts of a circuit board and considered to be essentially two-dimensional) metallic or metallized ring-shaped structure mounted on a surface of the circuit board. The cross-section of the metallic ring-shaped structure, seen parallel to the circuit board, is designed such that the electromagnetic wave of the given frequency for which the antenna element is designed can pass through it. It is possible to think of such a structure as a metal waveguide. An air-filled metal waveguide is characterized by a cutoff frequency below which wave propagation through a structure of such a cross-section is inhibited.
It should be noted that in the context of the present disclosure a structure is considered to be ring-shaped if the electromagnetic wave in the air-filled region is, considering the cross-section of the structure, encircled/surrounded by a metal conductor of any cylindrical shape, the latter comprising for instance (but not limited to) square, rectangular, circular or elliptical shape (i.e. inner and/or outer cross-section) with or without one or several protrusions called ridges.
The antenna element of the present disclosure further comprises a first galvanic contact (i.e. a direct, galvanic, metal-to-metal contact, which shows lower series impedance and thus less signal disturbance and less tolerance sensitivity than the otherwise common coupling methods like series capacitance coupling or shunt inductance coupling and which preferably is formed by a planar surface area of each of the structures joined by the contact with the space (thin layer) between the planar surface areas being filled with electrically conductive material, e. g. solder or electrically conductive adhesive) between the first conductor and a first part of the separate 3-dimensional, metallic ring-shaped structure, and a second galvanic contact between the second conductor and a second part of the separate 3-dimensional, metallic ring-shaped structure, wherein at least one of the first galvanic contact and the second galvanic contact comprises at least two essentially L-shaped sections.
Preferably, in this configuration the two galvanic contacts are connected via the ring-shaped structure but otherwise RF-decoupled from each other, i.e. galvanically separated or connected only by RF-decoupling structures like a short with a length of n*λ/4, where n is an odd integer.
Specifically, if the at least two essentially L-shaped sections of the first or second galvanic contact lie in the same plane as the other galvanic contact, such an arrangement can be realized in a single-layer technology, especially if the first or second galvanic contact is electrically connected to a ground plane located on the rear side of the substrate, i.e. the side opposite to the side on which the separate, 3-dimensional, metallic ring-shaped structure is located, by vias which run through the substrate or if the first or second galvanic contact is electrically connected to at least one ground trace located in the same plane as the respective other galvanic contact.
In this way, it can be achieved that conductors (first conductor, second conductor) apart from a ground plane of the circuit board and vertical connections (vias) lie in a single plane.
According to the terminology used in this description, a contact comprises an essentially L-shaped section if it extends over an angular section of the above-described ring-shaped structure which comprises at least 20° and less than 170° of the 360° angular extension of the ring-shaped structure.
More specifically, there can optionally/preferably be a region in which the first part of the L and the second part of the L merge orthogonally. Accordingly, such an L-shaped section can e.g. be formed by a section of a circle and its radius.
It should be noted that these L-shaped sections do not have to be separated from each other, but may be connected to each other. Specifically, there are shapes resembling the letters U or C that can be formed using two or more L-shaped sections (and eventually further sections). Likewise, it should be noted that a T-shaped section comprises an L-shaped section as defined above.
The contact sections between the transmission line(s) and the ring-shaped part need to realize/provide a smooth transition for the guidance of the electromagnetic wave and the conduction of currents and also need to prevent leakage of the electromagnetic wave, which would result in radiation in unwanted directions, in unwanted couplings and power loss. The L-shape as described above with its angular extension allows for such a smooth transition.
As a result of the above-described air-filled ring-shaped structure contacted by the galvanic contacts to the at least two conductors of the at least one transmission line in the described/claimed way, the electromagnetic wave travelling along the transmission line to the antenna element will essentially (that is, with the prevailing part of its energy) be carried in the ring-shaped structure, to finally reach the aperture and radiate. The opposite direction of energy flow will be possible in a similar manner, as the antenna is a reciprocal device.
It turns out that in such a design even though the overall size of the antenna is small (that is, not much larger than one wavelength), the transition from a planar transmission line to the ring-shaped structure can be made such that the reflection coefficient at the feeding line is very small over a wide frequency band.
In a preferred embodiment, this effect can be enhanced if at least in the area that is covered and/or surrounded by the separate metallic or metallized ring structure the side of the circuit board opposite to the side on which the separate metallic or metallized ring structure is mounted is covered by a metallic ground plane, which may be contacted to the galvanic contact between ground line conductor and separate metallic or metallized ring structure through the circuit board.
According to a preferred embodiment of the present disclosure, the antenna element is designed for a wavelength λ and the height of the separate, metallic or metallized ring-shaped structure is >λ/3. At a short distance above the circuit board, the metallic or metallized ring shaped structure ends, thereby forming a radiating aperture. The shape of the aperture and the form of the ring-shaped structure allow influencing, to some extent, the direction of radiation, described by the radiation pattern. If the overall height of the ring-shaped structure above the circuit board is rather small (less than—approximately—half of a wavelength at frequency of operation), then the maximum of radiation intensity will be directed perpendicular—or close to perpendicular—with respect to the circuit board and the size of the solid angle comprising rather strong radiation (called beamwidth) will be large. If the overall height is larger, other radiation patterns can be engineered.
According to a preferred embodiment of the present disclosure, the first galvanic contact and the second galvanic contact are arranged on (i.e. are formed in such a way that the formed galvanic contacts contact at least) opposite sides of the separate 3-dimensional, metallic or metallized ring-shaped structure.
Preferably, the first or the second galvanic contact contacts one side of the ring-shaped structure to the signal trace of the transmission line, and the second or the first galvanic contact contacts the opposite side of the ring-shaped structure to the ground trace of the transmission line.
It has been found that the performance of the antenna element benefits if the coupling between transmission line and the ring-shaped structure occurs via a galvanic contact between these components.
Specifically, this can be implemented in such a way that at least the conductors forming a signal trace (which—by their nature—interact with electromagnetic fields) joined with the ring-shaped structure by the respective galvanic contacts point away from the ring-shaped structure.
Structurally, this means that the signal trace(s) of the feed line(s) should preferably neither cross nor extend into the volume formed by the inner space of the ring-shaped structure plus its perpendicular projection to the side of the circuit board opposite to the side on which the separate metallic or metallized ring structure is mounted or, if design considerations do not permit this, it should cross or reach into said volume preferably as far away from the surface of the circuit board on which the ring-shaped structure is located as possible—e.g. on the opposite surface of the circuit board—, but at least more than ⅓ of the height of the circuit board below said surface.
One possibility to realize this involves leading the signal trace of said transmission line directly, specifically without crossing said volume, to the respective galvanic contact, but not beyond, and leading the ground trace on a metallized rear side of the circuit board (specifically using said metallized rear side as ground trace).
The metallic or metallized ring-shaped structure can include mechanical features supporting a cost-efficient assembly technology, such as mounting pins, bevel edges for improved solder flow, flat area for pick-and-place, openings for visual inspection. The metallic or metallized ring-shaped structure can also include mechanical features for achieving the required impedance bandwidth and the required radiation pattern, such as impedance steps and features to affect diffraction of fields (bevel edges, narrow slits, and corrugated surfaces).
A particularly suitable technology for cost-efficient manufacture of such rather complex ring-shaped parts is injection molding. The use of plastic injection molding with subsequent metallic plating of the molded parts, followed by surface-mount soldering them on circuit boards, is well established and very cost-efficient while maintaining a high degree of accuracy, leading to metallized structures. Metallic structures can be created by application of MIM (metal injection moulding) or PIM (powder injection moulding) techniques.
The ring-shaped structure forming the actual antenna element of the present disclosure can be molded and removed from the mold as a single part, that is, it does not have any indentations, which makes the manufacture particularly efficient.
Specifically, according to a preferred embodiment of the present disclosure the separate 3-dimensional, metallic or metallized ring-shaped structure is shaped in such a way that it bridges a gap between the first conductor and the second conductor.
In this way, creation of an electrical short can be avoided in spite of providing a closed ring shaped structure.
In order to create the possibility to perform quality control in a convenient and easy way, the separate 3-dimensional, metallic or metallized ring-shaped structure can be shaped in such a way that it comprises an opening for optical inspection of one of said galvanic contacts.
According to another preferred embodiment of the present disclosure, the separate 3-dimensional, metallic or metallized ring-shaped structure comprises at least one ridge or a pair of ridges with equal or different protrusion depth that are located opposite to each other on opposing sides of the separate 3-dimensional, metallic or metallized ring-shaped structure. The cutoff frequency of a waveguide cross-section can be reduced by this optional introduction of one or two ridges.
This embodiment can be refined further if the separate 3-dimensional, metallic or metallized ring-shaped structure comprises two pairs of ridges or single ridges wherein said pairs of ridges or single ridges are oriented orthogonally to each other in a plane parallel to the circuit board.
In a preferred embodiment, the antenna comprises two transmission lines and the respective galvanic contacts between transmission line and metallic or metallized ring-shaped structure are located on terminal sections of the respective conductors forming the signal traces, at which the terminal sections of the conductors preferably run orthogonally to each other in the plane of the circuit board. In this way, a dual polarized antenna element can be created in an easy and convenient way.
In order to facilitate easy and precise mounting of the separate 3-dimensional, metallic or metallized ring-shaped structure on the circuit board, the separate 3-dimensional, metallic or metallized ring-shaped structure preferably comprises or is preferably connected to pins. If said ring shaped structure has been formed by injection moulding techniques, injection points of the injection moulding are preferably located on said pins.
According to another preferred embodiment of the present disclosure, at least sections of the sidewalls of the separate 3-dimensional, metallic or metallized ring-shaped structure that define an opening of the separate 3-dimensional, metallic or metallized ring-shaped structure are tapered or stepped in order to improve the radiation process.
Also, it has turned out to be advantageous for the removal of unwanted sidelobes in the radiation pattern, if at least some sections of sidewalls of said separate 3-dimensional, metallic or metallized ring-shaped structure that define a radiating aperture of the antenna element have a higher thickness than the remaining parts of the separate 3-dimensional, metallic or metallized ring-shaped structure.
Another optional but advantageous possibility to achieve a reduction of unwanted sidelobes in the radiation pattern is to provide at least some sections of sidewalls of said separate 3-dimensional, metallic or metallized ring-shaped structure that define the radiating aperture of the antenna element with a corrugated surface.
If at least one suction area is provided on a surface of said separate 3-dimensional, metallic or metallized ring-shaped structure, suction-based pick and place techniques can be applied for placing and mounting of the antenna element.
According to another preferred embodiment of the present disclosure, a dielectric focusing element is located on top of the radiating aperture of the antenna element. This dielectric focusing element can, e.g., be a sphere, a cone, a rod, or a horn made of a dielectric material. Also, in order to increase focusing (or directivity) of the radiation of the antenna structure, or to reduce coupling to additional, close by antenna elements, a small dielectric lens element can be added to the top opening of the metallic ring-shaped structure.
Advantageously, the transmission line is a microstrip planar transmission line or a co-planar waveguide planar transmission line.
Several of the antenna structures according to the present disclosure can be placed close to each other on the same circuit board, thereby forming an antenna array. Antenna arrays are suitable in wireless communications to create beam forming and beam steering functionality or support so-called MIMO transmission schemes. The antenna structures can be placed with all their axes parallel to each other, or alternatively, with their axes in different directions. In the latter case, polarization-versatile or dual-polarized antenna arrays can be designed.
A prototype antenna operating in the 60 GHz band shows a measured impedance bandwidth (defined as reflection coefficient smaller than −10 dB) of 14% (55.5 GHz to 64 GHz) and a simulated radiation efficiency of more than 96% (57 GHz to 64 GHz), underlining the advantageous characteristics of the proposed antenna elements.
Next, the present application is explained in more detail using figures showing specific embodiments of the disclosure. The figures show:
On top of the circuit board a separate, 3-dimensional, metallic or metallized ring-shaped structure 130 is located on surface 102 of the circuit board 101. The ring-structure 130 has an essentially rectangular shape, but bridges gaps 111, 112 that are provided between the first conductor 110 and the second conductor 120. Furthermore, the ring-shaped structure 130 has two ridges 131, 132 each extending from the center of one of the long sides of the rectangular shape of the ring-shaped structure 130 towards the respective opposite long side. The cutoff frequency of a waveguide cross-section can be reduced by this optional introduction of one or two metallic ridges, creating a dual-ridge cross-section.
A first RF contact, which cannot be seen in the representation of
A second RF contact, which also cannot be seen in the representation of
The embodiment of the antenna element 200 shown in
It should be stressed, however, that the galvanic contacts 250, 260 between the ring-shaped structure 230, first conductor 210 and second conductor 220 are formed in the same way as described above for ring-shaped structure 130, first conductor 110 and second conductor 120 of the embodiment of
The second galvanic contact 260 is also formed between the surface of the second conductor 220 that is located on the side of the surface 202 of the circuit board 201 and a part of the bottom surface of the ring-shaped structure 230. As can be seen from
The part of the surface of the second conductor 220 that is part of
It should be noted that the cutting plane that leads to the representation of
Analyzing the part of the contact region between the ring-shaped structure 230 and the second conductor 220, which forms the section of the second galvanic contact 260 that is shown in
The first L-shaped section is located between the bottom corner of sides 240 and 237 of the ring-shaped structure 230 and one of the parallel sides of the U with protrusion formed by said surface of the second conductor 220 (because this side of the U is broader than the side 237 of the ring-shaped structure 230).
The second L-shaped section is located between the bottom corner of sides 237 and 241 of the ring-shaped structure 230 and the same parallel side of the U with protrusion formed by said surface of the second conductor 220 (again because this side of the U is broader than the side 237 of the ring-shaped structure 230).
The third L-shaped section is located between the bottom corner of side 241 and protrusion 323 of the ring-shaped structure 230 and the connecting side of the U and the protrusion extending therefrom of said surface of the second conductor 220.
Returning now to
However, the ring-shaped structure 230 additionally comprises a section that extends to a greater height relative to the surface 202 of the circuit board 201 than the ring-shaped structure 130 relative to the surface 102 of the circuit board 101. In this section, several features are integrated into the ring-shaped structure in order to optimize its performance as an antenna and tailor its radiation characteristics.
First of all, the position of section 237a of the sidewall 237, and the corresponding part of the sidewall 239, which is not visible in
Next, it should be noted that the upper sections of the sidewalls 240, 241 have a higher thickness t than the remaining parts of the ring-shaped structure 230.
Last not least, there are sections 240a, 241a of the ring-shaped structure that define the radiating aperture 280 of the antenna element 200 that have a corrugated surface.
The main difference between the antenna element 200 of
The embodiment of
Due to the dual-polarized application with two feed-lines, the circuit board 401 has not only a first conductor 410 and a second conductor 420, but also a third conductor 460 and a fourth conductor 470. The second conductor 420 and the fourth conductor 470 extend through the circuit board 401 to the rear side of the circuit board 401 which is not visible in
On top of the circuit board 401 a separate, 3-dimensional, metallic or metallized ring-shaped structure 430 with an essentially circular geometry and four ridges 431, 432, 433, 434 extending radially towards the center of said circular geometry arranged in two pairs of opposing ridges 431, 432 and 433, 434, respectively, is located on surface 402 of the circuit board 401. It should be noted that the first pair of opposing ridges 431, 432 is oriented orthogonally to the second pair of opposing ridges 433,434 in a plane parallel to the surface 402 of the circuit board 401.
The lower part of said ring-structure 430, i.e. the part that is adjacent to the circuit board and on which the galvanic contacts between conductors 410, 420, 460, 470 and ring-shaped structure 430 are created is shown in
As can be seen in
Returning to
As best seen in
As shown in
The invention provides an antenna element (100, 200, 300, 400) comprising a circuit board (101, 201, 301, 401) with a transmission line, said transmission line comprising at least a first conductor (110, 210, 310, 410) and a second conductor (120, 220, 320, 420),
a separate 3-dimensional, metallic or metallized ring-shaped structure (130, 230, 330, 430) mounted on a surface (102, 202, 302, 402) of said circuit board (101, 201, 301, 401), a first galvanic contact between said first conductor (110, 210, 310, 410) and a first part of said separate 3-dimensional, metallic ring-shaped structure (130, 230, 330, 430), and a second galvanic contact between said second conductor (120, 220, 320, 420) and a second part of said separate 3-dimensional, metallic ring-shaped structure (130, 230, 330, 430), wherein at least one of said first galvanic contact and said second galvanic contact comprises at least two essentially L-shaped sections and an antenna array (1000, 2000) comprising several such antenna elements (100, 200, 300, 400).
| Number | Date | Country | Kind |
|---|---|---|---|
| 16191928 | Sep 2016 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/074865 | 9/29/2017 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2018/060476 | 4/5/2018 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4590478 | Powers et al. | May 1986 | A |
| 6271799 | Rief et al. | Aug 2001 | B1 |
| 7088290 | Ohno | Aug 2006 | B2 |
| 8350767 | Brigham | Jan 2013 | B2 |
| 9806393 | Kildal | Oct 2017 | B2 |
| 20030132885 | Kuramoto et al. | Jul 2003 | A1 |
| 20090322636 | Brigham et al. | Dec 2009 | A1 |
| 20120032750 | Feil | Feb 2012 | A1 |
| 20130099989 | Kuramoto et al. | Apr 2013 | A1 |
| 20130241788 | Anderson et al. | Sep 2013 | A1 |
| 20140285383 | Fakharzadeh et al. | Sep 2014 | A1 |
| Number | Date | Country |
|---|---|---|
| H05273234 | Oct 1993 | JP |
| Entry |
|---|
| Hallbjörner, “Circuit board integrated patch transition between microstrip and rectangular waveguide, optimised for producibility,” IEE Proceedings: Microwaves, Antennas and Propagation, Aug. 7, 2006, IEE, Stevenage, Herts, GB, vol. 153, No. 4, pp. 330-334. |
| World Intellectual Property Organization, “International Search Report,” issued in International Patent Application No. PCT/EP2017/074865, dated Nov. 29, 2017, document of 4 pages. |
| European Patent Office, “Extended European Search Report,” issued in European Patent Application No. 16191928.7, dated Mar. 14, 2017, document of 10 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20200036104 A1 | Jan 2020 | US |
