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设计了一款低输入阻抗的阿基米德螺旋天线。在传统阿基米德螺旋天线的始端加入宽度一定的指数螺蜷线,天线的输入阻抗得到降低,从而放松了对指数渐变微带线馈电巴仑的长度要求。该天线的输入阻抗为75Ω,这使得指数渐变微带巴仑的长度仅为22.5mm即可充分满足天线在2～10GHz频率范围内的馈电要求。天线采用深度为22.5mm(约为最大工作波长的15%)的反射背腔,测试结果表明:在2～10GHz的频率范围内,天线驻波比小于2.5,天线主辐射方向上的轴比小于4dB,方向图对称性良好。
An Archimedes spiral antenna with low input impedance is designed. The input impedance of the antenna is reduced by adding an exponential spiral coil at the beginning of the traditional Archimedes spiral antenna, thereby relaxing the length of the balun fed by the exponential gradient microstrip line. The input impedance of the antenna is 75Ω, which makes the exponential gradual change of the length of the microstrip ballast is only 22.5mm to fully meet the antenna’s feed requirement in the frequency range of 2~10GHz. The antenna uses a reflective back cavity with a depth of 22.5mm (about 15% of the maximum operating wavelength). The test results show that in the frequency range of 2 to 10GHz, the antenna standing wave ratio is less than 2.5 and the axial ratio in the main radiation direction of the antenna is less than 4dB, the symmetry of the pattern is good.