雷达料位测量原理和主要技术因素
Principle and main technical factors of radar level measurement
雷达料位计采用非接触式测量方法，是一种理想的经济型产品，适用于储料罐、静井或外接腔体等.
The radar level gauge adopts non-contact measurement method, which is an ideal economical product, which is suitable for storage tank, static well or external cavity
雷达料位计是利用回波测距原理。发射天线向被测目标发射微波（即发射波），被测目标的微波被接收天线接收（即回波），信号处理器将发射信号与接收信号比较，计算出被测距离，并可算出相应的料位值
Radar level meter is based on echo ranging principle. The transmitting antenna transmits microwave (i.e. transmitting wave) to the measured target, and the microwave of the measured target is received by the receiving antenna (i.e. echo). The signal processor compares the transmitted signal with the received signal, calculates the measured distance and calculates the corresponding material level value
微波脉冲来回传播时间t由下式决定：
The back and forth propagation time t of microwave pulse is determined by the following formula:
t=2a/c (1)
t=2a/c (1)
式中a—天线到被测目标的距离
Where a is the distance between the antenna and the measured target
c—微波传播的速度（光速）
C-The speed of microwave propagation (light speed)
由于微波在传播途径上有衰减和干扰反射，故测量的关键是要能接收到反射回波，并识别出有效回波。接收的回波能量Pk可用简化的雷达方程表示如下：
Since microwave has attenuation and interference reflection in the propagation path, the key of measurement is to receive the reflected echo and identify the effective echo. The received echo energy PK can be expressed by the simplified radar equation as follows:
Pk=Pτx C x GiGtGr/r4 (2)
Pk=Pτx C x GiGtGr/r4 (2)
式中： Pτ—天线辐射功率
Where: P τ - radiation power of antenna
C --- 经验系数，由经验决定
C -- empirical coefficient, determined by experience
Gi--- 由目标表面介电特性及面积决定的反射增益
GI is the reflection gain determined by the dielectric properties and area of the target surface