Patent Application
20210320424
The present application for patent claims priority to European Patent Office Application Ser. No. 20168655.7, entitled “A WAVEGUIDE POLARIZER AND A CIRCULARLY POLARIZED ANTENNA” filed on Apr. 8, 2020, assigned to the assignee hereof, and expressly incorporated herein by reference.
Embodiments herein relate in general to circularly polarized antennas. In particular, embodiments herein relate to a waveguide polarizer and a circularly polarized antenna comprising a waveguide polarizer. Also, the embodiments herein also relate to a satellite arrangement comprising a waveguide polarizer or a circularly polarized antenna comprising a waveguide polarizer.
Circularly polarized (CP) antennas are one type of antennas that have a circular polarization. CP antennas are becoming a key technology for various wireless systems including, for example, satellite communications, mobile communications, global navigation satellite systems (GNSS), wireless sensors, radio frequency identification (RFID), wireless power transmission, wireless local area networks (WLAN), wireless personal area networks (WPAN), Worldwide Interoperability for Microwave Access (WiMAX) and Direct Broadcasting Service (DBS) television reception systems, etc.
Due to the features of circular polarization, CP antennas have several important advantages compared to antennas using linear polarizations. For example, a CP antenna is very effective in combating multi-path interferences or fading. The reflected radio signal from the ground or other objects will result in a reversal of polarization, that is, right-hand circular polarization (RHCP) reflections show left-hand circular polarization (LHCP). A RHCP antenna will have a rejection of a reflected signal which is LHCP, thus reducing the multi-path interferences from the reflected signals. Another advantage is that a CP antenna is able to reduce the ‘Faraday rotation’ effect due to the ionosphere making it particularly well-suited for satellite communications. Also, in space communications, CP mitigates the potential effects of changes in the relative orientation between the transmitting and receiving antennas.
In space, a satellite antenna transmits and receives modulated carrier signals within the radio frequency (RF) part of the electromagnetic spectrum. For satellite communication, the frequencies may typically range between about 0.3 GHz (VHF-band) to around 50 GHz (Q-/V-band). These frequencies represent microwaves having wavelengths ranging from 1 meter down to a few millimetres. The satellite antennas are normally customized to handle these high frequencies and small wavelengths. For example, pipe antennas for omnidirectional coverage are widely used for Telemetry, Tracking and Command (TTC) communication in satellites today.
If a pipe antenna is to radiate circular polarization, the pipe antenna is required to be excited by a feed component for generating the circular polarization. Normally, a septum polarizer is used to generate the circular polarization. However, adding a septum polarizer to a pipe antenna will also add significantly to the weight and volume of the resulting antenna assembly.
For all space applications and satellite arrangements, there is a constant need to reduce the weight and volume of all components and parts, including antennas.
It is an object of embodiments herein to enable a small and low weight circularly polarized antenna.
According to a first aspect of embodiments herein, the object is achieved by a waveguide polarizer for converting between a linearly polarized electromagnetic field in a first waveguide and a circularly polarized electromagnetic field in a second waveguide. The waveguide polarizer comprises a structure interconnecting the first and second waveguide comprising a waveguide excitation arrangement with a bifilar helical shape.
According to a second aspect of embodiments herein, the object is achieved by a circularly polarized antenna comprising a waveguide polarizer as described above.
According to a third aspect of the embodiments herein, the object is achieved by a satellite arrangement comprising a waveguide polarizer or a circularly polarized antenna as described above.
By providing a waveguide polarizer as described above, a reciprocal transition between a linearly polarized electromagnetic field in a first waveguide and a circularly polarized electromagnetic field in a second waveguide is enabled that removes the need for a septum polarizer when implementing a circularly polarized antenna. Thus, since the added weight and volume of a septum polarizer is removed, the weight and volume of the circularly polarized antenna may be significantly reduced. Hence, a small and low weight circularly polarized antenna is enabled.
Features and advantages of the embodiments will become readily apparent to those skilled in the art by the following detailed description of exemplary embodiments thereof with reference to the accompanying drawings, wherein:
The figures are schematic and simplified for clarity, and they merely show details which are essential to the understanding of the embodiments presented herein, while other details have been left out. Throughout, the same reference numerals are used for identical or corresponding parts or steps.
Furthermore, the waveguide polarizer 30 is here placed or located inside the pipe of the circularly polarized antenna 20 enabling a significantly more compact antenna assembly for the circularly polarized antenna 20. This is illustrated in
In the example shown in
In some embodiments, the structure 30, 50A, 50B may comprise two matching sections 50A, 50B. The first matching section may be a transition waveguide 50A and the second matching section may be a third waveguide 50B. The transition waveguide 50A may interconnect the first waveguide 70 with the third waveguide 50B. The transition waveguide 50A may also provide an impedance match between first waveguide 70 and the third waveguide 50B. Here, the transition waveguide 50A may be said to comprise a transmission line with a characteristic impedance and a specific length. The length of the transition waveguide 50B may typically be a quarter of a wavelength of the propagating electromagnetic field in the first waveguide 70. The third waveguide 50B may interconnect with, or form part of, the waveguide excitation arrangement with a bifilar helical shape 40A, 40B.
According to some embodiments, the waveguide excitation arrangement with a bifilar helical shape 40A, 40B, may consist of two helical filaments 40A that are connected to opposite sides of the first waveguide 70. In some embodiments, the waveguide excitation arrangement with the bifilar helical shape 40A, 40B may be galvanically connected to the first waveguide 70 on opposing sides. In some embodiments, the waveguide excitation arrangement with the bifilar helical shape 40A, 40B is galvanically connected to ridges 40B on opposing sides of the first waveguide 70. Here, it should also be understood that the bottom part of the two helical filaments 40A may form the ridges 40B on the opposing sides of the first waveguide 70. The ridges 40B may also provide matching of the bifilar helix and some mechanical advantages. In some embodiments, the two helical filaments 40A may be shorted or open at the top.
Furthermore, in some embodiments, the length of the second waveguide 80 of the waveguide polarizer 30, 60 may be adapted such that evanescent modes generated by the waveguide excitation arrangement with a bifilar helical shape 40A, 40B contribute significantly to the antenna radiation properties. This provides more degrees of freedom to optimize the design, but may be considered a more complicated case. Optionally, in some embodiments, the length of the second waveguide 80 of the waveguide polarizer 30, 60 may be adapted such that no evanescent modes generated by the waveguide excitation arrangement with a bifilar helical shape 40A, 40B contribute significantly to the antenna radiation properties. This would advantageously ensure that there is no interaction with the evanescent modes, which could be advantageous in some cases.
The description of the example embodiments provided herein have been presented for purposes of illustration. The description is not intended to be exhaustive or to limit example embodiments to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various alternatives to the provided embodiments. The examples discussed herein were chosen and described in order to explain the principles and the nature of various example embodiments and its practical application to enable one skilled in the art to utilize the example embodiments in various manners and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products. It should be appreciated that the example embodiments presented herein may be practiced in any combination with each other.
It should be noted that the word “comprising” does not necessarily exclude the presence of other elements or steps than those listed and the words “a” or “an” preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, that the example embodiments may be implemented at least in part by means of both hardware and software, and that several “means”, “units” or “devices” may be represented by the same item of hardware.
The embodiments herein are not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be construed as limiting.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20168655.7 | Apr 2020 | EP | regional |
