1. Field of the Invention
The present invention concerns adaptors for use in connection with antennas and corresponding arrangements.
2. Background Art
Conventional microwave and millimeter wave radio applications are usually built of discrete passive and active components individually assembled on a common high-frequency substrate or board, resulting in a low integration level.
The performance of such a radio application, in particular at millimeter wave frequencies, is typically limited by the number of permissible consecutive interfaces or transitions between discrete components, which is a function of the quality of the above-mentioned common substrate and the capability of the interconnect technology to reproduce a predefined reflection coefficient.
In an effort to significantly reduce the overall cost of communication systems and applications, low cost key components like high gain antennas, filters, and front end modules are under development.
A key requirement for higher volume market penetration is a significant reduction of the overall costs. Typical cost drivers are the antennas, as such.
The following main features of a modern, antenna-based radio communication system may be highly desirable:
A novel approach applying a suitable integration methodology is believed to be a key factor for the successful low cost and high performance realization of the above-mentioned envisioned radio systems. It should enable millimeter wave units with minimum microwave technology used and substantially simplified assembly. Ideally, the need for an expensive high-frequency common substrate carrier could be entirely eliminated. It should also deliver both antenna and integrated waveguide transition designs that show little sensitivity to a variable package- and board-level EM environment and are easily transferable to different manufacturing and assembly setups.
It is another objective of the present invention to provide a reliable and reproducible interface to additional waveguide-based (e.g. millimeter wave) active and passive components.
It is another objective of the present invention to provide a reproducible, low loss, fully shielded test and measurement interface to a planar (e.g. millimeter wave) circuit.
The present invention is directed to constructing a suitable adaptor to be used in testing and tuning scenarios of a low cost medium gain (5-10 dBi) modular surface-mountable antenna for highly integrated radio applications and a.
The inventive surface-mountable antenna has two main functions. The first function is the function of a regular antenna for radiating and/or receiving electromagnetic energy into (out of) free space. The second function is an adaptor function where the antenna constitutes a first part of a planar-circuit-to-waveguide transition. The antenna is, hence, also called connector base or female adaptor part. As the second part of the planar-circuit-to-waveguide transition, a connector plug or male adaptor part is used. It can be repeatedly attached to the antenna, thereby creating a low loss, broadband and reproducible planar-circuit-to-waveguide transition.
The antenna presented herein is a surface mountable, quasi-planar, antenna with an integrated waveguide connector function.
According to the present invention, the main elements of the inventive antenna comprise a reflector frame and a radiating element with an at least slightly bendable cantilever interface to an active (planar) circuit. The millimeterwave waveguide antenna itself is formed by the radiating element and two cavities, namely a back reflector cavity and an open cavity. The radiating element is mounted inside the reflector frame, providing a common interface between these two cavities. The entire antenna is mounted on top of an electrically conducting plane located on a common substrate, yielding the back reflector cavity as an essentially electromagnetically shielded volume.
The inventive antenna device, which constitutes the first part of a planar-circuit-to-waveguide transition, has the following main characteristics:
The inventive adaptor, which constitutes the second part of a planar-circuit-to-waveguide transition, has the following main characteristics:
It provides for a mechanical and electromagnetic interface to a waveguide or to another component with waveguide interface, e.g. an antenna, or test and measurement equipment.
When the adaptor is connected to the antenna device, an arrangement with a fully shielded interface between a planar circuit and a waveguide, or antenna is provided.
The antenna device and the adaptor presented herein are designed to be used preferably for millimeter wave applications and communication systems. The present invention achieves a significant cost reduction by employing a modular cost effective design.
Operating at other frequency bands not being excluded, one frequency band of special interest is the worldwide license-exempt range from 57 to 66 GHz (the corresponding standardized waveguide band being V-band, 50 to 75 GHz), another commercially interesting band is the combination of 71-76 GHz and 81-86 GHz ranges (the corresponding standardized waveguide band being E-band, 60 to 90 GHz). In the first case, the antenna device should preferably cover the 57 to 66 GHz range with good matching properties and radiation efficiency, whereas in the function of a complete planar-circuit-to-waveguide transition, full V-band coverage would be desirable. In the second case, the antenna device should preferably cover the 71 to 86 GHz range, whereas in the function of a planar-circuit-to-waveguide transition, full E-band coverage would be desirable.
The invention addresses the adaptor that is designed to fit on top of the reflector frame of the antenna device, which provides for an adequate testing environment, or which can be used to connect the antenna device to a suitable other component with waveguide interface.
The antenna presented herein has the advantage of being compatible to low cost, high volume manufacturing and assembly technologies. Another advantage is the small form factor of the quasi-planar antenna and the fact that it has a chip-scale size.
Depending on the actual implementation, the antenna device is capable of supporting an input impedance bandwidth sufficiently large for Gbps wireless data communication (relative bandwidth greater than 20%).
Other advantages are obtained, namely a flat gain response with respect to frequency and a high radiation efficiency (typically above 80%). The antenna device may furthermore have a medium gain (5-10 dBi), being sufficient for near-range point-to-point communication applications.
The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part thereof, and in which there are shown by way of illustration, preferred embodiments of the invention. Such embodiments do not necessarily represent the full scope of the invention, however, and reference is therefore made to the claims herein for interpreting the scope of the invention.
The following sections describe several terms used throughout the specification and the claims to facilitate discussion of the invention.
In the following text, cast parts are discussed. According to the present invention, the term “cast part” is to be understood as parts which were either produced using an (automatic) injection molding method or a powder injection molding (PIM) process with subsequent sintering. In the first case, thermoplastics may be used, yielding the final dimensions in a 1-step process.
According to the present invention, various plastic injection molding compounds may be used in order to produce the cast parts. Some examples of suited plastics are listed in the following: PA (polyamide); POM (polyoxymethylene); PET (polyethylene terephthalate); PS (polystyrene); LCP (liquid crystal polymer); PBT (polybutylene terephthalate); ABS (acrylate-butadiene-styrene); PPE (polyphenylene ether); PP (polypropylene); PMMA (polymethylmethacrylate); PC (polycarbonate); PAS (polyaryl sulfone); PES (polyether sulfone); PEI (polyether imide); PAI (polyamide imide); PPS (polyphenylene sulfide); PVDF (polyvinylidene fluoride); PEEK (poly ether ether ketone).
Polymer blends may also be used. These are combinations of two or more miscible polymers. Blending is processing, mixing, or reacting two or more polymers to obtain improved product properties.
Modified plastics having filler particles may also be used, which makes the construction of solidly adhering non-electrode or galvanically deposited metal coatings easier. The filler particles may be made of electrically conductive metals (e.g., palladium) or of electrically non-conductive metal pigments, as used in spray lacquers for electromagnetic shielding. These metal pigments are used as a catalyst for non-electrode deposition of a metallic primer coating, which may subsequently be galvanically reinforced. The spray lacquer achieves only a limited adhesive strength, which is strongly dependent on the plastic material. By embedding the particles in the plastic compound, a significant improvement of the adhesive strength is achieved in that the particles are exposed only on the surface through a short pickling process or by laser ablation, but otherwise they remain enclosed by the plastic compound.
Another important group of modified plastics employs a combination of glass fibers and mineral or ceramic particles for adjusting the coefficient of thermal expansion (CTE) to the one of the common substrate.
Instead of plastic, metals may also be used for producing the cast parts. Aluminum is especially suitable, which may be processed in the aluminum injection molding method. Titanium or Stainless Steel can be used by employing the metal injection molding (MIM) process, which is a variant of the above-mentioned powder injection molding (PIM) process. An advantage of this approach may be the simplification or even evasion of a subsequent metal plating step.
The cast parts are distinguished in that a minimum of post-processing outlay is necessary. For this reason, the cast parts are herein also referred to as precasts or finished parts. The dimensions of the cast parts are very precise.
Reflectors which preferably have a conductive surface may be used. This conductive reflector surface may be set to ground. The reflector surface may be implemented as flat or curved. Preferably a metal surface on a common substrate serves as reflector.
Before addressing specific embodiments of the invention, some basic aspects are addressed and explained by reference to the
One key element of the present invention is the so-called surface-mountable antenna device 100, as schematically illustrated in
A first communication system 200 comprising an active device 40 and an antenna device 100, according to the present invention, is illustrated in
A second communication system 200 comprising an active device 40, an antenna device 100, and an adaptor 50, according to the present invention, is illustrated in
A third communication system 200 comprising an active device 40, an antenna device 100, an adaptor 50 and a waveguide element 400, according to the present invention, is illustrated in
A fourth communication system 200 comprising an active device 40, an antenna device 100, an adaptor 50 and an antenna 500, according to the present invention, is illustrated in
A first planar antenna device 100 is shown in
The reflector frame 10 further comprises a support structure 13 (cf.
The radiating element 20 has a planar, horizontally-oriented antenna substrate 21 with a rectangular mode conversion area 23.1 and a cantilever-shaped feedpoint section 24 protruding from the mode conversion area 23.1 (cf.
In a further improved embodiment, one or two pairs of slots 72, 73 are situated adjacent to slot 71 and are folded in order to accommodate a length of approximately half of the wavelength at the centre of the intended frequency band. Preferably, at least one short end-section of either slot 72 or 73 is running parallel and in close proximity to slot 71, thereby providing for electromagnetic coupling between 71 and 72, 73, respectively.
According to the invention, the radiating element 20 is mounted by the support structure 13 inside the interior section 16 so that the interior section 16 is divided into the above-mentioned back reflector cavity 16.1 and the open cavity 16.2 (cf.
According to the invention, the reflector frame 10 comprises metal or is at least partially metallised.
The planar antenna device 100 is by design so constructed as to be integrated onto a common substrate 30 such as a low frequency board, a printed circuit board or a similar support structure (cf.
The reflector frame 10 of the antenna device 100 has a quasi-planar layout wherein the “z-axis” dimension is much smaller than the “x-axis” and “y-axis” dimensions. The z-axis is perpendicular to the x-y-plane, and the (antenna) substrate 21 lies in the x-y plane. Preferably, the height (in z-direction) of the frame 10 is between 1 and 5 times the height of the planar circuit 40. If a planar 500 μm thick SiGe chip 40 is employed, then the height of the back reflector cavity 16.1 may also be about 500 μm.
Small differences between the height of the circuit 40 and the height D of the feedpoint section 24 (cf.
In a preferred embodiment, the reflector frame 10 comprises a support structure 13 designed to accommodate the radiating element 20, said support structure 13 matching the shape of the antenna substrate 21 of the radiating element. That is, the reflector frame 10 serves as mechanical support structure for supporting the antenna substrate 21. The reflector frame 10 is a 3D constituent of the antenna device 100 and is part of the mechanical interface M1 for mounting the entire antenna device 100 on a (common) substrate 30. The reflector frame 10 also serves as mechanical interface M2 since it is designed to receive an adaptor 50.
The dimensions of the lower cavity 16.1 of the reflector frame 10 are chosen so that the radiating element 20 can be inserted into the interior section 16 through this lower cavity 16.1. For this reason, the horizontal dimensions of the lower cavity 16.1 are somewhat larger than the horizontal dimensions of the radiating element 20, that also exhibits somewhat larger horizontal dimensions than the upper portion of the frame 10 or open cavity 16.2.
To accommodate the radiating element 20, the shape and details of which will be discussed later, one of the sidewalls 12 of the reflector frame 10 has a lateral opening 14 where a feedpoint 24 of the radiating element 20 can extend out of the reflector frame's interior section 16. In a preferred embodiment, a bendable cantilever interface (electrical interface E1 in
In a preferred embodiment, at least the sidewalls 12 of the reflector frame 10 facing the interior section 16 are metallised so that the reflector frame 10 can be used as an aperture-type antenna. For this reason, this part may be provided with a metal coating, or the cast reflector frame part may include electrically conductive particles embedded in a host material in such a way that the cast part is electrically conductive in at least the surface region. This is necessary in order to facilitate the use of the interior section 16 as an antenna aperture for the radiating element 20 and for providing a well defined, shielded enclosure in conjunction with a suitable adapter 50, as explained further below.
The reflector frame 10 enclosed by the circumferential walls 12 has two openings: an upper horizontal opening 11 and a lower horizontal opening 17 facing the metal plane 31. One can observe from
A side view of the planar antenna device 100, as mounted on the common substrate 30, can be seen in
The radiating element 20 used in the modular antenna device 100 of the present invention is depicted in
The feedpoint section 24 is meant to extend from the reflector frame 10 through the lateral opening 14 and has the role of enabling the mechanical and electrical connection (interfaces E1 and M1) of the radiating element 20 to other components via feed lines 25. The feedpoint section 24 is realized as cantilever and it may feature flip-chip contacts near its outer edge. Preferably, a bendable cantilever serves as feedpoint section 24 so as to provide a compliant interface to the planar circuit 40 (cf.
In another preferred embodiment, the entire substrate 21 (not only the cantilever part) is a flexible substrate. In this case, the reflector frame 10 provides for sufficient mechanical stability against so-called microphony (being the modulation of electrical signals by acoustically induced periodic displacements) and/or thermally induced bending or warping. The flexible substrate can be used in connection with all embodiments, too.
The electrically conducting plane 31 is part of back reflector cavity 16.1 and it may serve as ground contact. The conducting plane 31 may be either a part of the planar antenna device 100 for better reproducibility, or it may be part of substrate 30 for lower cost. If the plane 31 is part of the substrate 30, then it also serves as mechanical support for the planar antenna device 100.
An exemplary first embodiment of a communications system 200, which comprises a planar antenna device 100, as mounted on a common substrate 30, is shown in
Operating at other frequency bands not being excluded, the present invention is particularly suited to operate in the 57 to 66 GHz or the 71 to 86 GHz frequency ranges, respectively. The planar antenna device 100 at the same time is meant to be used mainly for indoor communication. Also the so-called “full-duplex” simultaneous two-way communication is possible using the planar antenna 100, provided that an additional diplexer is employed between antenna device 100 on one hand, and receive- and transmit ports of circuit(s) 40, respectively.
The radiation efficiency of the antenna device 100 may be well beyond 90%, which coincides with a low loss operation of the waveguide transition (insertion loss of a few tenths of a dB). Also by design, the device 100 is very robust, meaning it presents a low sensitivity to the manufacturing tolerances, allowing using a relatively low cost subtractive etching process instead of thin-film process that requires additive conductor formation.
The reflector frame part 10 of the present invention is designed so that an adaptor 50, as it is depicted on
This adaptor 50 is designed to be connectable to the upper horizontal opening 11 of the antenna device 100. The purpose of the adaptor 50 is to provide a possibility to connect various testing and tuning equipment to the modular antenna device 100 (e.g. via a waveguide element 400, as illustrated in
For this reason, the upper portion 52 of the adaptor 50 has a shape adapted to the particular testing or tuning equipment used. The lower portion (male portion) of the adaptor 50 has a form factor so that the male part fits into the antenna 100. The adaptor's male portion is designed so that a mechanical contact to the antenna frame 10 is provided (this mechanical connection is referred to as interface M2). Preferably, a galvanic contact is established between the parts 10 and 50 when the adaptor 50 is plugged into the antenna 100, thereby providing full electromagnetic shielding.
The body of the adaptor 50 provides for a mechanical connection to the frame 10 on one side (interface M2) and a mechanical connection (interface M3) to the (test equipment) waveguide element 400 on the other side. The body further comprises features/elements which ensure a near-field modification inside the otherwise open cavity 16.2 (interface EM2) when an electro-magnetic wave is coupled from the reflector frame 10 into the waveguide 400. At least part of the adaptor's surface is conducting. In the context of the present invention, a near-field modification shall denote a well-defined manipulation of the electromagnetic boundary conditions close to the mode conversion area 23.1 (or 23.2). It is reproducibly introduced when the adaptor 50 is engaged with the frame 10, and absent when the antenna 100 is in normal operation.
According to the present invention, the adaptor 50 provides for a waveguide transition (e.g. to a standard WR-15 waveguide in case of V-band, interface EM3) which is required for an adequate testing environment, also ensured by the robustness and tolerance insensitivity of the connection between the reflector frame 10 and the adaptor 50. In order to be able to provide the required transition, a highly efficient, high bandwidth coupling to a waveguide interface (EM3) is rendered possible by a modification of the antenna near-field.
Similarly to the reflector frame 10, the adaptor 50 may also be a (pre-) cast part, but the adaptor 50 can also be made by milling, drilling and other conventional processes. Please refer to the previous discussion about cast parts for details of the casting methods and alternatives. The cast reflector frame 10 together with the cast adaptor 50 provides for a direct connection between a planar circuit 40 and a waveguide interface. Both parts 100, 50 cooperatively provide for a desired impedance transformation.
Compatible to low cost, high volume manufacturing technologies are employed, according to the present invention, when intended to be used as transition inside a communication product or system 200, e.g. with a waveguide-based high gain antenna 500 or filter. However, their application is not a must for attaching test and measurement adapters that are needed in smaller numbers.
In
To ensure a proper mechanical alignment of the adaptor 50 and the reflector frame 10, spring contacts, surface contacts, nut/bolt connections, or the like may be employed as mechanical interface M2. The same elements may be used to provide for the electromagnetic contact (interface EM2) between the reflector frame 10 and the adaptor 50. It is conceivable to employ different elements for the mechanical and the electromagnetic connection, respectively.
In order to provide for a transition to a waveguide element 400, the adaptor 50 may comprise a standard waveguide flange (e.g. WR-15 in case of operation inside V-Band).
In a preferred embodiment, as depicted in
The planar antenna device 100 fitted with the adaptor 50 supports fully calibrated test environments suitable for manufacturers who need to test and fine-tune their equipment, namely the planar circuit 40, in a reliable and reproducible manner.
Due to the high degree of reproducibility of the antenna-to-adaptor mating, calibration kits can be defined.
Another well-known method can be applied to determine the scattering matrix of the arrangement 300 (cf.
In a preferred embodiment, the adaptor 50 and the reflector frame 10 are designed so that the adaptor 50 can be attached and detached manually. A mechanical clamping mechanism is thus preferred.
In a further embodiment, an open cavity antenna may be devised with an alternative mode conversion area 23.2 (cf.
This embodiment is characterized by the fact that the open upper cavity 16.2 (cf.
In a preferred embodiment, the aperture 81 is dimensioned for supporting only one fundamental resonant mode within the frequency range of operation.
An advantageous embodiment comprises an essentially rectangular aperture 81. The mode conversion area 23.2 takes the form of a modified E-probe. Since the height of the back reflector cavity 16.1 is given by the circuit 40 (e.g. a SiGe chip), it can not be used as a free electrical design parameter. In the 60 GHz range, the typical chip height of 500 μm represents only ca. 30% of the usual depth of the backshort section in an E-probe based planar circuit-to-waveguide transition, being approximately a quarter-wave length, see e.g. S. Hirsch, K. Duwe, and R. Judaschke “A transition from rectangular waveguide to coplanar waveguide on membrane,” Infrared and Millimeter Waves, 2000. Conference Digest. 2000 25th International Conference.
The modified E-probe is fed by a center conductor 28, which itself is fed by a feedline 25 comprised in a feedpoint section 24 in analogy to the previously described embodiment (cf.
In a preferred embodiment, a ring-shaped, electrically conductive sheet 74 is provided and is placed on the same surface of substrate 21 as the center conductor 28. It comprises an opening 83 of 2-fold mirror symmetrical shape, which lies entirely within opening 82. In analogy to the first embodiment of planar antenna device 100, multiple electrically conducting via connections 75 may be used for ensuring identical electrical potentials on sheets 26 and 74. The center conductor 28 protrudes from the electrical ground layer into the opening 82, where it takes the form of a preferably narrow strip 85 (cf.
A preferred embodiment of the mode conversion area 23.2 provides the mirror-symmetrically arranged, electrically conductive, transverse strips 88, which are connected to the sides of patch 86 and running approximately parallel to the conductor of opening 82. A distance to the edge near center conductor 28 is much smaller than to the far edge. This modification of the well-known E-probe arrangement compensates for the unusual small height of back reflector cavity 16.1, reestablishing a good and broadband impedance matching both for the antenna and waveguide transition operation mode. The arrangement with stray capacitances established by gaps 87 and 89, respectively establish a quasi-lumped element capacitive voltage divider. This simple and compact structure allows for impedance matching bandwidth sufficing for Gigabit modulated RF waveforms and for a full waveguide-band (e.g. V-band 50-75 GHz) operation of the waveguide transition i.e. test and measurement operation mode. The elimination of planar reactance matching networks in the planar feedpoint section significantly reduces the millimeter wave insertion loss.
In an advantageous embodiment of open cavity 16.2, two pedestals 15 are provided which each have the same mirror symmetry S1-S1 as the mode conversion area 23.2. They are also identical and as such establish a second, local mirror symmetry plane. The height of pedestals 15 is less or equal to the height of cavity 16.2 and their width and length are adjusted to obtain optimized broadband impedance matching properties for the antenna mode operation. It is advantageous to adjust the width of pedestals as to obtain optimized matching with a pedestal length of between 50% and 90% of the distance between the inner sidewall 12 of cavity 16.2 and the edge of aperture 81. With the help of pedestals 15, good aperture efficiency for the radiation from upper opening 11 can be achieved, i.e. a good compromise between matching bandwidth and near-uniform aperture fields can be found.
For providing a reproducible high frequency contact to an adaptor 50, at least the shielding wall 16 and the inner sidewalls 12 of upper cavity 16.2 are electrically conductive, e.g. by coating with a thin metallic layer.
In a further preferred embodiment, the front face 91 of the upper cavity 16.2 is also electrically conducting with circumferential contact to the inner sidewalls 12 and exhibits an essentially flat surface.
In
Yet another embodiment of a communication system 200 (with modified E-probe design) is shown in
According to the invention, the antenna 100 can be attached to a circuit 40 and can either be used alone, without connection to the adaptor 50, or connected to the adaptor 50.
In unconnected configuration, the antenna 100 is a low-loss, wide bandwidth, high efficiency component of a communication system 200 with medium gain, easily mounted on a standard substrate 30 and connected to a circuit 40.
In connected configuration, the waveguide interface EM3, M3 provides the possibility to add active and passive components to the circuit 40 including, but not limited to, filters, high-gain antennas and amplifier modules. The adaptor 50 preferably provides for a field modification (e.g. for suppressing unwanted resonant modes) which enables the connection of a waveguide 400 or antenna 500 to the antenna device 100.
Also in connected configuration, the waveguide interface EM3, M3 allows for a low loss, a fully shielded, reproducible test and measurement environment for the circuit 40 within the full operation bandwidth of standard waveguide components 400.
The inventive antenna device 100 and adaptor 50 are co-designed to simultaneously fulfill their specific function both in connected and in unconnected configuration.
All elements, especially the antenna device 100, are designed to be fabricated using standard, low cost materials and establish high volume manufacturing processes. Low-volume technologies, like CNC machining, are not precluded, molding is a preferred technology but for larger quantities.
As a result, a modular and very flexible solution is available that allows to build cost effective modules comprising the present antenna device 100, is adapted for test and measurement in production and design sequences. It is equally well suited to accommodate active and passive components with waveguide interfaces. A unified interface of this kind allows for further reduction the overall production cost by minimizing the number of necessary module versions, lessening the logistic efforts and increasing stock turnover.
Compared to existing solutions, the present invention significantly reduces the cost of millimeter wave transmitter and receiver circuits and modules in particular.
The following table is an integral part of the description
Number | Date | Country | Kind |
---|---|---|---|
08154524.6 | Apr 2008 | EP | regional |
This is a divisional application of U.S. patent application Ser. No. 12/988,003, filed Oct. 15, 2010 which is a U.S. National Phase of International Application No. PCT/EP2009/053428, filed Mar. 24, 2009, which are both incorporated herein by reference, and which claims priority on European patent application No. 08154524.6, filed Apr. 15, 2008, which priority claim is repeated here.