天线理论-旋转栅天线

什么是旋转栅天线

旋转栅天线是一种常用的天线，其原理是基于旋转栅的机械旋转产生电磁波，常用于VHF和UHF频段。旋转栅天线可以分为两种，水平旋转栅天线和垂直旋转栅天线。

原理

旋转栅天线的原理是利用机械旋转的圆弧形的金属片，使其在某个频率下达到共振，随着旋转栅的旋转，金属片会不断地从电源中吸取电能，进而产生电磁波辐射出去。水平旋转栅天线的金属片是沿水平方向旋转，而垂直旋转栅天线的金属片则是沿垂直方向旋转。

代码实现

旋转栅天线的代码实现比较复杂，需要进行基本的电磁学计算和机械设计计算。以下是一份常用的旋转栅天线的实现代码，供程序员参考。

import math

class RotationGateAntenna:
    def __init__(self, frequency, length_of_gate, radius_of_gate, number_of_gate):
        self.frequency = frequency
        self.length_of_gate = length_of_gate
        self.radius_of_gate = radius_of_gate
        self.number_of_gate = number_of_gate
        self.speed_of_light = 299792458
        self.pi = math.pi

    def get_wavelength(self):
        return self.speed_of_light / self.frequency

    def get_circumference_of_gate(self):
        return self.pi * self.diameter_of_gate

    def get_length_of_gate_at_frequency(self, frequency):
        wavelength = self.get_wavelength(frequency)
        return self.length_of_gate / wavelength

    def get_impedance_of_gate_at_frequency(self, frequency):
        length_of_gate_at_frequency = self.get_length_of_gate_at_frequency(frequency)
        return 60 / length_of_gate_at_frequency

    def get_gate_impedance(self):
        gate_impedance = 0
        for i in range(1, self.number_of_gate + 1):
             gate_impedance += self.get_impedance_of_gate_at_frequency(i*self.frequency)
        return gate_impedance / self.number_of_gate

    def get_gain_at_angle(self, theta):
        sine_of_theta = math.sin(theta)
        gate_impedance = self.get_gate_impedance()
        first_k_term = 2 * gate_impedance * math.pow(sine_of_theta, 2)
        second_k_term = math.pow(gate_impedance, 2) + math.pow(2 * math.pi * self.radius_of_gate, 2)
        return 4 * math.pi * self.radius_of_gate * math.sqrt(first_k_term / second_k_term)

    def get_gain(self):
        elevation_angles = [i * self.pi / 180 for i in range(-90, 91, 1)]
        gain_at_angles = [self.get_gain_at_angle(theta) for theta in elevation_angles]
        return max(gain_at_angles)

参考文献

• 旋转栅天线-百度百科
• 旋转栅天线的优化设计-知乎