Patent Application
20190190107
The present invention relates to the field of microwave devices and more specifically to splitters or combiners of electromagnetic waves with orthogonal polarizations.
One of the methods to increase a wireless communication system throughput is the usage of two orthogonal polarizations than can be done without significant sophistication of the transceiver. This enables a simultaneous transmission and/or receipt of two data flows, each flow being carried by orthogonally polarized electromagnetic waves. The key components of such a system are dual polarized antennas and orthomode transducers, which are devices used to distinguish appropriately polarized waves from the common dual-pol antenna port. Each of single-pol waves is guided to one or more orthomode transducers ports.
Traditionally, orthomode transducers are provided on hollow metallic waveguides, and more specifically on several waveguides of rectangular cross-section which support only one polarization, and one waveguide of a round or square cross-section, which supports two types of orthogonal waves. Usually, a round or square waveguide port is connected to the dual polarized antenna. One of such orthomode transducers is disclosed in U.S. Pat. No. 6,087,908 and presented herein in
To overcome the abovementioned drawbacks of the orthomode transducer based on hollow metallic waveguides, planar orthomode transducers based on probes were recently introduced. In this case, separation of orthogonal polarizations is provided by orthogonal metal probes etched on a single or several printed circuit boards which are fixed across a round or square dual polarized waveguide. This waveguide is connected to the dual polarized antenna port. Similar orthomode transducer is disclosed in patent JPH11308004 and shown in
Technology of printed circuit boards is developed rapidly in the last decade. The printed circuit boards process for low-loss substrates which have low dielectric losses in microwave frequency range has became much cheaper than manufacturing of hollow waveguide components and, thus, more profitable in mass-production. From the technical point of view, the usage of printed circuit boards instead of waveguides allows significantly decreasing device dimensions and simplifying its integration in the transceiver's radio frequency circuit.
However, the probe based orthomode transducer implemented on the printed circuit board has several other drawbacks. These are a relatively low isolation between orthogonally polarized channels, a narrow frequency band and the need of additional quarter-wave metal backshort for the input of dual polarized waveguide.
Alternatively, an orthomode transducer can be embodied by replacement of the dual polarized waveguide (with round or square cross-section) connecting antenna output and the orthomode transducer itself with the antenna element that can be either a separate dual polarized antenna or a primary radiator element that forms the required amplitude and phase distributions to illuminate the main antenna (e.g., a lens antenna or a dish reflector antenna).
Such approach is disclosed in patent CN104752841 and shown herein in
But there are several technical drawbacks in the orthomode transducer described above and considered as the closest prior art of the present invention:
1. Lack of versatility. The usage of the primary antenna element together with the main antenna significantly decreases the variety of possible antenna designs which can be implemented together with the primary antenna element. In other words, the considered orthomode transducer does not have a commonly used dual polarized port such as, for example, a dual polarized metal waveguide. This prevents from using different antennas with the orthomode transducer and significantly limits its applications. Such approach cannot be implemented for very common horn antennas or integrated lens antennas which have waveguide feed radiator placed on the flat lens surface;
2. Narrow frequency band. As such, a resonant cavity slot antenna is a narrow conductive frame which starts to radiate at the tuning frequency that depends on the frame perimeter. That is why both the antenna and, consequently, the orthomode transducer have relatively narrow operational frequency range (4%) that has been confirmed by experimental data as presented in CN104752841;
3. Low isolation between orthogonal polarizations. An experimental orthogonal polarization isolation of the described orthomode transducer is only 22 . . . 23 dB in the operational frequency band (data also shown in CN104752841). For many wireless communication applications this isolation could be not enough;
4. High insertion loss. The considered orthomode transducer with the primary antenna element has relatively high insertion loss due to the narrow radiating slot of the resonant cavity loop frame. A narrow slot in the loop frame increases the surface current density and the electric field intensity in dielectric near to the slot. This increases the insertion loss level.
Thus, there is a need for a more universal orthomode transducer device which is applicable for connection to any dual polarized antennas with waveguide interface, that has wider passband, higher orthogonal polarization isolation, lower insertion losses and is simple and planar.
The above issues have been solved by a planar orthomode transducer comprising a substrate integrated resonator connected to two substrate integrated waveguides, wherein both the substrate integrated resonator and the substrate integrated waveguides are formed provided by a plurality of metallized via holes between two metallization layers of a printed circuit board, and wherein the planar orthomode transducer further comprises a dual polarized metal waveguide, and the substrate integrated resonator additionally comprises a slot aperture in one of the metallization layers, wherein the dual polarized metal waveguide is mounted on a surface of the printed circuit board in an area the slot aperture of the substrate integrated resonator, and the substrate integrated resonator is a resonator used for high-order orthogonal modes.
This enables, on the one hand, widening of the operating frequency band of the planar orthomode transducer, reducing of insertion losses, improvement of the polarization diversity, and, on the other hand, providing for a standard dual polarized output waveguide that serves to connect the planar orthomode transducer with antennas of various types.
Said technical effect is achieved by introducing a substrate integrated resonator that is placed in between two metallization layers of a printed circuit board and is formed by metallized via holes along the perimeter of the resonator. From two adjacent sides of the resonator, there are two substrate integrated waveguides that are connected to the substrate integrated resonator via windows in metallized via holes of the substrate integrated resonator. The resonator is the resonator of two nonfundamental (i.e., high-order) orthogonal modes of the electromagnetic field. Due to that, the resonator is excited by one of the substrate integrated waveguides, the other stays unexcited, thus there is high isolation between two orthomode transducer outputs.
There is a slot aperture of a special form in the substrate integrated resonator, represented by a slot in the top metallization layer of the printed circuit board. The excitation of the metal dual polarized waveguide is provided through this aperture. This waveguide is capable to transmit two orthogonally polarized electromagnetic waves simultaneously. Whereas each polarization corresponds to one of two nonfundamental orthogonal modes of the substrate integrated resonator. As a result, two modes in the substrate integrated resonator are excited by transmitting orthogonal waves to the planar orthomode transducer input through the dual polarized metal waveguide. Each mode excites only one of the substrate integrated output waveguides.
The widening of operating passband and the reduction of insertion losses of the planar orthomode transducer are provided by the absence of resonating elements (such as a slot loop) in the slot aperture of the substrate integrated resonator.
The improvement of the polarization diversity is provided by the use of the substrate integrated resonator of nonfundamental orthogonal modes in the structure of the planar orthomode transducer.
The planar orthomode transducer has a dual polarized metal waveguide as an input interface in its structure. This type of waveguides is a standard interface for variety of microwave devices and antennas. That makes the transducer more adapted for different applications.
In one embodiment of the present invention, the substrate integrated resonator and the substrate integrated waveguides are formed in the printed circuit board that has only one dielectric layer. In this embodiment it is possible to optimize thickness of this layer to decrease an insertion loss and to provide better impedance matching.
In another embodiment of the present invention, the substrate integrated resonator and the substrate integrated waveguides are formed provided in the multilayer printed circuit board. In this embodiment it is possible to form the resonator and the waveguides either in one dielectric layer of the printed circuit board (e.g., at the top layer) or in several layers of the board between any two metallization layers.
In a specific embodiment of the present invention, the substrate integrated resonator has one of the following shapes: square shape, round shape, cruciate shape, H-shape. This shape is formed by the plurality of metallized via holes in the printed circuit board. The shape of the resonator depends on the shape of the cross section of the dual polarized metal waveguide because in that case it is relatively simple to get good impedance matching in a wide frequency band.
In various specific embodiments of the present invention, the dual polarized metal waveguide has one of the following shapes: a square shape, a round shape, a cruciate shape, an H-shape. The variety of shapes of the planar orthomode transducer makes it universal and provides the possibility to connect the transducer to various antennas that have waveguide interface of different cross-section shapes.
In one embodiment of the present invention, the slot aperture of the substrate integrated resonator has one of the following shapes: a square shape, a round shape, a cruciate shape, an H-shape. In particular embodiments this shape is the same as a shape of the substrate integrated resonator.
In another embodiment of the present invention, the slot aperture of the substrate integrated resonator includes feeding probes. Usually such probes are projected to the slot aperture of the substrate integrated resonator. They are disposed at the top metallization layer of the printed circuit board and intended for additional impedance matching.
In other more specific embodiment of the present invention, the transducer further comprises metal ridges along the sidewalls of the dual polarized metal waveguide. Those ridges are aimed for impedance matching between the substrate integrated resonator and the dual polarized metal waveguide. In particular embodiment these metal ridges are formed along sidewalls and are smoothly tapered into the waveguide channel staring from the printed circuit board, i.e. wedge shaped.
In another embodiment of the present invention, the planar orthomode transducer has at least one additional metallized via hole between two metallization layers of the printed circuit board, this hole located inside the substrate integrated resonator. Such additional metallized via holes are aimed for tuning the structures of the orthogonal modes of the substrate integrated resonator in the areas close to the resonator feeding points to compensate for the associated discontinuities.
In a further embodiment of the presented invention, the substrate integrated resonator is connected to the substrate integrated waveguides through windows in the plurality of via holes forming substrate integrated resonator and additionally through the matching irises of the substrate integrated waveguides.
In another embodiment of the present invention, the outputs of the substrate integrated waveguide are connected to the transitions to the planar transmission line that have one of the following types: a microstrip transmission line, a strip transmission line, a coplanar transmission line, a differential transmission line. In particular embodiment, these transmission lines are connected to the contact pads of the integrated circuits of the radio frequency module of the transceiver.
In another particular embodiment of the present invention, the substrate integrated waveguides are connected to substrate integrated filters. In this case, filters are aimed for frequency duplexing of two differently polarized signals. In particular embodiment, these are frequency duplexing filters of received and transmitted signals.
In one embodiment of the present invention, the substrate integrated waveguides are connected to transitions to metal waveguides. This structure is used to connect the planar orthomode transducer with the outputs of receivers and transmitters having waveguide interface.
In another embodiment of the present invention, the planar orthomode transducer is a primary radiator of an aperture antenna. In this case, a signal is directly radiated from the dual polarized metal waveguide to the side of the aperture antenna.
In another embodiment of the present invention, the output of the dual polarized metal waveguide is connected to an antenna. In particular embodiments these can be different horn antennas, reflector antennas or integrated lens antennas.
Details, features and advantages of the present invention follow from the description given further for the claimed technical embodiment and drawings that denote the following:
There are following features denoted in the figures: 1—a substrate integrated resonator; 2—substrate integrated waveguides; 3—a slot aperture of the substrate integrated resonator; 4—feeding probes; 5—metal ridges; 6—additional metallized via holes; 7—a matching irises of the substrate integrated waveguide; 8—windows in via holes forming the substrate integrated resonator; 9—a dual polarized metal waveguide; 10—a printed circuit board.
One embodiment of the present invention of a planar orthomode transducer is shown in
A dual polarized metal waveguide (9) is mounted on a surface of the printed circuit board (10). Walls of the dual polarized metal waveguide that is disposed on the printed circuit board (10) contact the top metallization layer of the printed circuit board (10). The aperture of the dual polarized metal waveguide covers a slot aperture of the substrate integrated resonator (3) that is formed in the top metallization layer of the printed circuit board (10) and has the same square shape as the metal waveguide cross-section form. The substrate integrated waveguides (2) are connected to the substrate integrated resonator (1) through windows in via holes of the substrate integrated resonator (8) and matching irises of the substrate integrated waveguides (7). The substrate integrated waveguides (2) are disposed at two adjacent sides of the substrate integrated resonator (1), orthogonally to each other. Whereas they have such dimensions that only fundamental electromagnetic mode exists in that waveguides (fundamental mode waveguides) in the operating frequency band of the planar orthomode transducer.
In the frequency band of the planar orthogonal transducer, dimensions of the substrate integrated resonator (1) allow to provide the substrate integrated resonator (1) with the higher order of the electromagnetic modes. They are nonfundamental orthogonal modes TEM21 and TEM12.
The printed circuit board (10) of the planar orthomode transducer can comprise one or more dielectric layers. In order to change a thickness of the dielectric layer or to change the dielectric material of the printed circuit board (10) the substrate integrated resonator (1) and the substrate integrated waveguides (2) can be provided in a single dielectric layer or in several dielectric layers of the printed circuit board (10). Such flexibility allows to use the planar orthomode transducer together with any other planar devices, including a full featured transceiver module that usually requires several layers of the microwave printed circuit board.
Shapes of the substrate integrated resonator (1) and the dual polarized metal waveguide (9) can be different: square, round, cruciate, H-shape or any other shape that allows to transmit or excite two orthogonal modes. Thus, for the dual polarized metal waveguide (9) it is the main fundamental modes TEM010 and TEM100, and for the substrate integrated resonator (1) it is the nonfundamental high-order modes TEM21 and TEM12. Shapes of the substrate integrated resonator (1) and the dual polarized metal waveguide (9) can be different or the same.
To match impedances between the dual polarized waveguide (9) and the substrate integrated resonator (1) of the planar orthomode transducer according to
Shapes of the slot aperture of the substrate integrated resonator (3) can be also different. Moreover, to achieve effective matching between the substrate integrated resonator (1) and the dual polarized metal waveguide (9) the slot aperture of the substrate integrated resonator (3) can comprise feeding probes (4), especially if metal ridges (5) are used at the same time.
The planar orthomode transducer can comprise additional metalized via holes (6), which align the structure of the electromagnetic modes of the substrate integrated resonator (1) and increase the operational frequency band of the planar orthomode transducer. These additional metallized via holes (6) are provided inside the perimeter of the substrate integrated resonator (1) but outside the area of the slot aperture of the substrate integrated resonator (3) and opposite the junction points of the substrate integrated waveguides (2). Junction points brings distortions to the structure of the fields of the modes which are excited by the substrate integrated resonator (1).
There are no additional radiating elements and there is no need for additional antenna mounting elements because of using the dual polarized metal waveguide (9). It allows to provide the transducer in smaller dimensions in comparison with the prior art. Besides, the possibility to make shapes of the dual polarized metal waveguide (9) different allows the device to be adapted for different applications.
The additional metallized via holes (6) as well as matching irises of the substrate integrated waveguide (7) at the junction points of the substrate integrated waveguide and the substrate integrated resonator (1) allow to increase the polarization diversity to 30 dB and to increase the frequency band.
The disclosed planar orthomode transducer does not contain narrow radiating slots that would have high concentration of the conductive currents and high electric field intensity in the dielectric layer of the printed circuit board (10) near the slot. Besides, the area of the slot aperture of the substrate integrated resonator (3) is larger in comparison with the prior art. Considering the above the level of the insertion losses which are brought by conductive currents is lower, that means that the insertion losses of the planar orthomode transducer is lower in the operating frequency band.
The planar orthomode transducer can be used as a radiating element for dielectric or metal aperture antennas. An output of the dual polarized metal waveguide (9) can illuminate a dielectric lens or another printed circuit board comprising reradiating elements. Thus, the planar orthomode transducer can function as a primary antenna element. Besides, the output of the planar orthomode transducer can be directly connected to an antenna that has waveguide interface, e.g. a horn antenna.
The outputs of the substrate integrated waveguides can comprise transitions from the substrate integrated waveguides (2) to microstrip, coplanar, strip, differential lines to match the planar orthomode transducer and the radio frequency transceiver module.
The outputs of the substrate integrated waveguides can be directly connected to the contact pads of the radio frequency transceiver module, the pad being provided on the same printed circuit board (10) as the planar orthomode transducer by the transitions mentioned above. Thus, the planar orthomode transducer and the radio frequency transceiver module can be implemented on the common printed circuit board (10).
The substrate integrated waveguides (2) can be connected to substrate integrated filters that comprise the substrate integrated resonators and are formed by two metallization layers of the printed circuit board (10) and metallized via holes. Thus, the printed circuit board (10) of the planar orthomode transducer can comprise an integrated element that provides frequency filtering at the radio frequency module of the transceiver.
The substrate integrated waveguides (2) can be connected to the transitions from the substrate integrated waveguides to the metal waveguides. Thus, the planar orthomode transducer can be connected to the waveguide interface devices, e.g. a standard measuring equipment.
The present planar orthomode transducer operates in the following way. The fundamental (main) modes TEM100 and TEM010 of the dual polarized metal waveguide (9) excite nonfundamental orthogonal modes TEM21 and TEM12 inside the substrate integrated resonator (1). When the fundamental mode TEM100 of the dual polarized metal waveguide (9) propagates and its electric field is polarized along X axis then the nonfundamental mode is excited in the substrate integrated resonator (1).
The present invention is not limited by the specific embodiments, that are mentioned in the description for illustration and covers whole possible embodiments and alternatives that are included in the present invention by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017144118 | Dec 2017 | RU | national |
