Array antenna of wide-band and low-profile beam wireless communication base station

The present invention and its advantages will be further explained below with reference to FIG. 1 and FIG. 2.

Referring to Figure 1, the array unit of the present array antenna is a radiation patch (including excitation radiation patch and parasitic radiation patch) fed by an L-shaped excitation probe. The middle of the radiation patch is rectangular, and both ends are tapered gradual structures. Under the excitation radiation patch, two L-shaped excitation probes are used to couple and feed the two ends of the excitation radiation patch. The L-shaped excitation probe is connected to the microstrip line feed network located on the ground plane. The sheet material of the microstrip line feeder network is a polytetrafluoroethylene sheet with a dielectric constant εr=2.65 and a thickness of 1mm. The two output ports of the microstrip feed network have the same signal amplitude but opposite phase. Using double L-shaped excitation probes with constant amplitude and reverse phase excitation methods can make the current distribution on the excitation radiation patch and the parasitic radiation patch more uniform, make the E-plane pattern more symmetrical, and further improve the antenna gain. On top of the exciting radiation patch, a parasitic radiation patch that is also tapered at both ends is added. Taking into account the characteristics of the beam width and front-to-back ratio of the azimuth plane pattern, the width, length and ground height of the excitation radiation patch are respectively designed as 0.243λ0, 0.496λ0 and 0.096λ0, and the width, length and ground height of the parasitic radiation patch They are respectively 0.198λ0, 0.425λ0 and 0.17λ0, and λ0 is the free space wavelength corresponding to the center frequency. The radiation patch used in the present invention is longer than the conventional radiation patch, so the gain of the radiation patch of the present invention is higher than that of the conventional radiation patch. Changing the two ends of the radiating patch into a tapered shape not only increases the antenna gain, but also facilitates impedance matching. The size of the parasitic radiation patch is relatively smaller than the size of the excitation radiation patch. The parasitic radiation patch not only has the function of impedance adjustment, but also has the function of improving the radiation pattern.

Compared with Figure 2, this antenna includes 6 array elements, each of which is excited in the same amplitude and phase. The array spacing is 0.82λ0. If the width of the reflector is designed to be 0.55λ0, and two metal folds with a height of 0.128λ0 are added to the periphery, the beam width of the azimuth plane is close to 78° in the entire frequency band, which is about less than the specification. The value in 90±8°, it is even impossible to achieve a more accurate beam width of 90±2°. At this time, if the width of the reflector is narrowed, the beam width can be widened to approach the beam width specified in the specification, but the standing wave ratio and front-to-back ratio of the array antenna will also change at this time, deviating from the specification. The direction of the prescribed value develops. In order to broaden the beam width while keeping other characteristics unchanged, the present invention adopts a reflector plate with gap metal flanges. The width of the metal fold of the slot is 0.031λ0, the slot pitch is 0.069λ0, and the slot height is 0.128λ0. The slot is equivalent to an additional radiator that is re-excited by the excitation radiation patch and the parasitic radiation patch. The electric field of the observation point in the far area is the vector superposition of the radiation field of the slit and the radiation field of the radiation patch. Because the input impedance of the radiation patch and the slot are different, the phase of the original electric field generated by the radiation patch and the slot is also different. At the same time, the distance between the observation point in the far area and the radiation patch and the slot is also different, resulting in the difference in distance. The phase difference is also different. In this way, the field of the observation point in the far area is determined by the shape of the array unit and the shape of the reflector (including the seam hemming). Under the condition that other characteristics have met the technical specifications, the beam width can be adjusted in a small range by changing the shape of the metal flange of the slot, so that it has a more accurate beam width, while other characteristics remain almost unchanged.

The standing wave ratio measured by the entire antenna (including the microstrip feeder network) is less than 1.5 in the entire frequency band. One antenna can simultaneously cover GSM1800 (1710~1880MHz), CDMA1900 (1850~1990MHz) and ITU'sIMT-2000 (1885~ 2170MHz) frequency band, simplifies the composition of the communication system, reduces the cost, and increases the reliability of the system. The measured radiation pattern is shown in Figure 3. It can be seen that the sidelobe level is less than -10dB, and the beam width of the azimuth plane is 92±2° in the entire frequency band, which is far better than the value 92±8° specified in the technical specifications of the wireless communication base station antenna. The front-to-back ratio level of the pattern is 25dB, which meets the technical specifications of wireless communication base station antennas. The net gain of the array antenna (after deducting the feeder loss) is 15.0dBi in the entire frequency band. The above test results show the effectiveness of the array antenna design.