The present invention relates to the field of telecommunications. More specifically, this invention relates to systems and devices for providing widened crossed dipole antenna beamwidth.
The field of antenna design is continuously adapting to the needs of the telecommunications industry. For some applications, multiple port antenna systems are desirable. Similarly, other applications may require not just multiple port antennas but also antennas which can be used for both high and low band frequencies. Finally, in other applications, antennas which can achieve specific beamwidths are required.
There are currently narrow band applications for antennas with four ports that can achieve 90 degree azimuth beamwidth. It has been suggested that increasing the height of a dipole antenna will increase azimuth beamwidth. Unfortunately, this technique cannot be applied to hex-port antennas. Firstly, increasing the height of the high band dipole to achieve 85 to 90 degree beamwidth generates a strong resonance in the low band spectrum. This resonance severely degrades the low band antenna pattern. Secondly, increasing the height of the low band dipole antenna increases the depth of the antenna. Finally, increasing the height of the high band and low band dipoles increases the cost of the antenna.
In another approach, it has been suggested that an 85 to 90 degree beamwidth can be achieved by using a small reflector, proper fencing, and by stacking the antenna columns. However, this method results in multi-column antennas that are impractically tall.
There is therefore a need for systems and devices which mitigate if not overcome the shortcomings noted above.
The present invention provides systems and devices relating to dipole antennas. The beamwidth of a crossed dipole antenna is widened by providing a parasitic monopole antenna adjacent to the crossed dipole antenna. In one configuration, each arm of the crossed dipole antenna has, adjacent to it, a parasitic monopole antenna. In another configuration, the crossed dipole antenna is surrounded by a number of other crossed dipole antennas acting as parasitic monopole antenna elements. The center or primary crossed dipole antenna can be for low band signals while the secondary crossed dipole antennas are for high band signals.
In a first aspect, the present invention provides an antenna system comprising:
wherein
In another aspect, the present invention provides an antenna system comprising:
wherein
The embodiments of the present invention will now be described by reference to the following figures, in which identical reference numerals in different figures indicate identical elements and in which:
The Figures are not to scale and some features may be exaggerated or minimized to show details of particular elements while related elements may have been eliminated to prevent obscuring novel aspects. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention.
Referring to
As can be seen from
To widen the beamwidth of the dipoles in
It should be noted that the monopole antennas can be a wire or a strip floating above the reflector (see
For clarity, while
It should also be clear that, while the above discussion relates to crossed dipole antennas, the concept of broadening a dipole antenna's beamwidth through the use of parasitic monopole antennas is also applicable to single dipole antennas. Thus, dipole antennas that are not in a crossed format (i.e. non-crossed dipole antennas) may also be used with parasitic monopole antennas to result in a broadened beamwidth for the dipole antenna.
While the above discusses the use of simple parasitic monopole antennas to broaden the beamwidth of a center dipole antenna, more complex antennas, which operate as parasitic monopole antennas, can also be used. Referring to
The antenna system in
In the antenna system of
It should be clear that the terms “high band” and “low band” refer to frequency bands for the signals being received or transmitted through the antenna systems and devices discussed in this document. High band frequencies can include 1695-2690 MHz or any frequencies within this range such as 1695-2180 MHz or 1695-2360 MHz. For low band frequencies, the frequency range covers 698-960 MHz, including any narrower bands such as 698-896 MHz.
Regarding implementation details, such as dipole antenna height, high band dipole antennas used for a system which covers 1710-2360 MHz as high band frequencies and which covers 698-894 MHz as low band frequencies were configured to be 0.16λ0 tall where λ0 is the high band center frequency wavelength. It should be clear that the term “height” refers to the spacing from reflector to the center of main dipole branch. For this implementation, since the height being measured is for the high band dipole antenna, then this distance is from the reflector to the center of the high band dipole antenna. For this implementation, this height is shorter than a normal high band dipole antenna which is, generally, 0.25λ0.
It is another challenge to design high band dipole antennas which are shorter than quarter wave length, has broadband operation, and has the proper pattern specifications. Since it is the height and length of the high band lower dipole branch (the angled portion of the dipole antenna) that determines the resonance in low band frequencies, the height and length of the high band dipole antenna are reduced to move this resonance out of the low band frequencies. By doing so, the dipole resonant frequency is shifted higher than the center frequency for that dipole. However, by bringing the dipole antenna closer to ground, impedance variation is high and this makes it difficult to match impedances. By adding another parasitic above the main dipole branch with a larger length, another resonance is created in the lower part of the frequency band. For clarity, this parasitic can be seen as trace 40A in
Referring to
To accommodate the low band 90/85 beamwidth, the high band dipole height spacing from the reflector is preferably reduced to less than a quarter wavelength of the high band frequency. For clarity, this dipole height is the distance from the dipole antenna center to the reflector. By using the high band dipole and the parasitic monopole concept, the high band dipole antennas can be designed to provide 85/90 degree beamwidth for the low band signal. However, when high band columns are moved to the reflector edge or to the two sides of low band dipole antenna, the pattern is distorted at some frequencies and tilts due to the asymmetric reflector. To overcome this effect, the system illustrated in
In the system of
In one implementation of the invention, the resulting antenna system provides an 85/90 degree azimuth beamwidth for both the low band and the high band frequencies. The resulting dual broadband hex-port antenna has dual slant +/−45 degree polarization with an 85 degree beamwidth. For the primary antenna, two dipole elements are arranged in a crossed format to create dual polarization for each low frequency band. Two antenna ports cover the 698-960 MHz band and four antenna ports cover the 1710-2690 MHz band. To achieve the 85/90 degree beamwidth for the high band frequencies, each high band crossed dipole antenna (the secondary antennas) is surrounded by four shorted monopoles. To achieve the same 85/90 azimuth beamwidth for the low band frequencies, each crossed low band dipole is surrounded by four high band dipole antennas which act as parasitic monopole antenna elements. The high band dipole antennas are carefully designed to work for the high frequency band and to act as proper parasitic monopole antennas for the low frequency band. Each high band antenna element is surrounded by 4 monopole antennas with proper height to create an 85/90 degree beamwidth. There are two columns of high band antennas and one column of low band antennas in the structure in
It should be clear that the high band dipole antennas in
Referring to
It should be clear that the present invention may be used for other frequency bands. Dipole antennas, whether in a crossed configuration or not, can have their beamwidths increased by using parasitic monopole antennas. For antenna systems designed for dual-band operation, depending on the frequency bands, high band dipole antennas might not act as proper parasitic monopoles for low band frequencies. In such situations, actual parasitic monopole antennas, such as those discussed above, can be added.
A person understanding this invention may now conceive of alternative structures and embodiments or variations of the above all of which are intended to fall within the scope of the invention as defined in the claims that follow.
Filing Document | Filing Date | Country | Kind |
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PCT/CA2016/050611 | 5/31/2016 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2017/020114 | 2/9/2017 | WO | A |
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Number | Date | Country | |
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20180166782 A1 | Jun 2018 | US |
Number | Date | Country | |
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62199790 | Jul 2015 | US |