[0041] in figure 1 , 2 In the first embodiment shown in a and 2b, the dual polarization radiating element 1 is formed by two half-wave dipoles 2, and each dipole includes a conductive feeder 3. The dipole 2 is supported by a shared support 4 fixed to the reflector 5. The radiating element 1 is constructed by forming the shared support 4 into a cylindrical shape. The cylindrical support 4 thus obtained is then placed on the shared plane reflector 5 in a perpendicular manner with the plurality of radiating elements 1.
[0042] In this example embodiment, the dipole 2 is printed on the first outer surface 6 of the shared support 4. Each dipole 2 is fed by a wire 3 located on the second inner surface 7 of the support 4. Of course, it is possible to print dipoles on the inner surface and feed lines on the outer surface. The conductive feeder 3 is, for example, a “microstrip” printed directly on the support 4. This shared support 4, whose circumference is about 2 wavelengths 2λ, is made of insulating materials with a high dielectric constant (typically 2.5-4.5), a narrow thickness (typically 0.5mm-2mm) and low cost to make. Alternatively, air may also form the support, in which case the dipole and the feeding microstrip may be formed by metal plates connected by insulating elements. Each pair of dipoles 2 is fed via a coaxial cable 8 passing through the reflector 5 at a single point.
[0043] Therefore, two pairs of half-wave dipole groups at the center frequency of the operating frequency band are obtained. The distance L above the surface of the reflector 5 from the horizontal axis 9 passing through the middle of the dipole 2 is about a quarter wavelength (λ/4). The intermediate shafts 10 passing through the middle of the adjacent dipoles 2 are separated from each other by a distance D of about one-half wavelength (λ/2). The oblique axis 11 passing through the middle of each dipole 2 of the first pair is placed at an angle of 45° with respect to the longitudinal axis 12 of the reflector 5 in order to establish -45° polarization, and passing through each of the second pair The oblique axis 13 in the middle of the dipole 2 similarly establishes +45° polarization.
[0044] The transmission and reflection parameters of the two pairs of dipoles of the radiating element, measured in the 600-1100MHz frequency band, are shown in image 3 with 4 in. These results show very stable characteristics in a large frequency band.
[0045] image 3 The standing wave ratio SWR of each pair of dipoles is detected as a function of the frequency F in MHz. For the frequency domain F ranging from 650-1050 MHz, the standing wave ratio SWR is less than 1.5, that is, the bandwidth corresponds to 47% of the center frequency of the frequency band.
[0046] Figure 4 Shows the decoupling K in dB between two pairs of dipoles as a function of frequency F in MHz. For the frequency domain ranging from 650-1100MHz, the decoupling K is greater than 20dB.
[0047] Consider now Figure 5 , Which shows another embodiment of the dual-polarization radiating element 50, such as a GSM frequency operating on the 900 MHz level, so that it can form an antenna that works in a dual frequency band.
[0048] The cylindrical shape of the support 51 of the radiating element 50 leaves a large empty area 52 in its center. This free area 52 can be used to add another radiating element 53 operating at a higher frequency (DCS 1800 MHz, in this example) in the center of the radiating element 50.
[0049] The radiating element 53 may be formed by two orthogonal half-wave dipoles. This can be, for example, a radiating element belonging to the first category described above, or it can have any other shape of radiating element. The height of this radiating element 53 operating in the high frequency band is about a quarter wavelength (λ/4). Since the radiating element 53 having a high frequency band is placed above the shared reflector 54, the characteristic of its radiation pattern is maintained.
[0050] Image 6 Another embodiment of the dual-polarization radiating element 60 is shown, for example, working at a CDMA frequency of the 800 MHz level, so that an antenna working in a dual frequency band can be formed.
[0051] Because the hollow area 61 in the cylindrical middle formed by the support 62 of the radiating element 60 is very large, a radiating element 63 that operates at a lower frequency and has a larger size can be inserted therein. The diameter of the cylindrical support 62 depends on the wavelength of the center operating frequency in the highest frequency band (800 MHz in this example). The radiating element 63, whose type is called "butterfly", is formed by two dipoles crossing each other with orthogonal polarizations of ±45°. The radiating element 63 is inserted in the center of the cylindrical support 62 working in a low frequency band (for example, LTE 700MHz). Therefore, it is possible to construct an antenna that works in a dual-band at a fairly similar frequency, such as LTE 700MHz and CDMA 800MHz, and works from the dual-polarization radiating element 62. The two radiating elements 62 and 63 arranged concentrically use a shared reflector 64, and the width of the antenna can be reduced accordingly.
[0052] Figure 7 , 8 a and 8b show a dual-polarized radiating element 70 capable of operating in multiple frequency bands. The multi-band radiating element 70 is composed of a single part. All dipoles and feed lines required for the operation of the radiating element 70 are supported by the shared support 71 fixed on the shared reflector 72. This substrate 71 may have a low cost and include a reduced amount of insulating material.
[0053] In this example, the radiating element 70 is a three-band element. The four dipoles 73a...73d, 74a...74d, 75a...75d of the three groups 73, 74, 75 are printed on the first outer surface 76 of the shared support 71. Each group 73, 74, 75 corresponds to a different frequency band. Each dipole 73a...73d, 74a...74d, 75a...75d consists of a microstrip line 73e...73h, 74e printed on the relatively second lower surface 77 of the shared support 71, respectively ...74h, 75e...75h feed. The 4 dipoles of each group 73, 74, 75 are fed by exactly 2 coaxial cables 78 across the reflector 72, resulting in a total of 6 coaxial cables 78 for the triple-band dual-polarized radiating element 70 .
[0054] A single shared support 71 is formed by three different diameter cylinders, so that the parts of the support 71 of each group 73, 74, 75 form a concentric cylinder, the diameter of which depends on the wavelength of the center operating frequency of each frequency band . The length of the support 71 is calculated so that the three concentric cylinders are connected to each other by the support part 79 without a dipole. The group 73 of dipoles 73a...73d arranged outside the largest diameter cylinder operates at a lower frequency, and the group 75 of dipoles 75a...75d arranged inside the smallest diameter cylinder operates at the highest frequency. Therefore, three groups of two pairs of half-wave dipoles 73, 74, 75 are obtained, each at the center frequency of its corresponding working frequency band, such as GSM 900MHz (73), DCS 1800MHz (74) and LTE 2600MHz (75).
[0055] The distance L between the horizontal axis 80 passing through the middle of the dipoles of each group and the surface of the reflector 72 is approximately a quarter wavelength (λ/4) of the central operating frequency. The intermediate shaft 81 passing through the middle of the two adjacent dipoles is at a mutual distance of approximately one-half wavelength (λ/2) of the central operating frequency. The dipoles 73a...73d, 74a...74d, 75a...75d are arranged to establish 2 orthogonally polarized signals in each of the 3 operating frequency bands.
[0056] If necessary, the band isolation device may be printed on the inner surface 77 of the shared support 71 supporting the microstrip lines 73e...73h, 74e...74h, 75e...75h. These devices make it possible to use only 2 coaxial cables in total, ie one cable per polarization, to feed the three-band dual-polarized radiating element.
[0057] Of course, the present invention is not limited to the described embodiments, and for those skilled in the art, many variations that do not deviate from the gist of the present invention can be obtained. In particular, the above-mentioned principle for three frequency bands can be extended to design multi-band dual-polarized radiating elements that work in more than three frequency bands.
