📡 LEO Satellite Doppler Shift Calculator

Orbital velocity · max Doppler shift · Doppler rate · pass curve

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Inputs

Orbit

Orbital velocity
– km/s
Orbital period
– min
Max pass duration
– min

Doppler Results

Max Doppler shift
±– kHz
Peak Doppler rate (zenith)
– Hz/s
Doppler @ elevation
– kHz
Total Doppler span
– kHz

Doppler Shift vs Time (overhead pass)

Signal arrives high (approaching, +Doppler), crosses zero at closest approach, then drops (receding, −Doppler). The steepest slope at t=0 is the peak Doppler rate your receiver's tracking loop must follow.

信号到来时频率偏高(接近,+多普勒),在最近点穿过零点,随后下降(远离,−多普勒)。 t=0 处最陡的斜率就是接收机跟踪环路必须跟上的峰值多普勒变化率。

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📖 How to use

  1. Choose a preset band or enter your carrier frequency and orbit altitude.选一个预设频段,或输入载波频率和轨道高度。
  2. Read the orbital velocity, maximum Doppler shift and peak Doppler rate at the top.在上方读取轨道速度、最大多普勒频移和峰值多普勒变化率。
  3. Set the elevation angle to get the instantaneous Doppler at that point in a pass.设置仰角,得到过境中该点的瞬时多普勒。
  4. The curve shows Doppler vs time over an overhead pass — the steep slope at closest approach is the rate your tracking loop must follow.曲线是一次过顶的多普勒-时间关系——最近点处的陡峭斜率就是跟踪环路必须跟上的变化率。
  5. Remember: higher carrier frequency → larger Doppler. Size your receiver's acquisition range accordingly.记住:频率越高,多普勒越大;据此设计接收机的捕获范围。

How Doppler shift works for satellites

A LEO satellite moves fast (~7.5 km/s) relative to a ground station, so the received carrier frequency is shifted by the radial (line-of-sight) component of that velocity. As the satellite rises, it approaches you and the frequency is shifted up; at closest approach the radial velocity is zero (no shift); as it sets it recedes and the frequency shifts down.

Formulas used

Orbital velocity: v = √(μ / (Rₑ + h)), μ = 398600.4418 km³/s²

Doppler shift: Δf = −(ṙ / c) · f, where ṙ is the range rate and c is the speed of light

This calculator models a worst-case overhead (zenith) pass, where Doppler shift and Doppler rate are largest. The maximum Doppler scales linearly with carrier frequency — which is why X- and Ku-band links need far wider acquisition ranges than UHF.

All computation runs locally in your browser.

卫星多普勒频移原理

LEO 卫星相对地面站运动很快(~7.5 km/s),因此接收到的载波频率会被该速度的径向(视线方向)分量所偏移。 卫星升起、向你接近时,频率上移;在最近点径向速度为零(无偏移);卫星落下、远离时频率下移。

使用的公式

轨道速度:v = √(μ / (Rₑ + h)),μ = 398600.4418 km³/s²

多普勒频移:Δf = −(ṙ / c) · f,其中 ṙ 为距离变化率,c 为光速

本计算器按最坏情况的过顶(天顶)过境建模,此时多普勒频移与变化率最大。最大多普勒与载波频率成正比—— 这正是 X、Ku 波段链路比 UHF 需要宽得多的捕获范围的原因。

全部计算在你的浏览器本地完成。