Radar PRF & Ambiguity
The pulse repetition frequency of a pulsed radar sets a fundamental trade: a low PRF gives long unambiguous range but a low blind speed, while a high PRF does the reverse. This tool returns the maximum unambiguous range and velocity, the first blind speed, the PRI and duty cycle, and the range resolution from the pulse width — the numbers behind choosing a low-, medium- or high-PRF waveform.
Equations & Parameters ▸
\(\text{PRI}=\dfrac{1}{\text{PRF}} \qquad R_{ua}=\dfrac{c}{2\,\text{PRF}} \qquad v_{ua}=\pm\dfrac{\lambda\,\text{PRF}}{4}\)
\(v_{blind}=\dfrac{n\,\lambda\,\text{PRF}}{2} \qquad d=\dfrac{\tau}{\text{PRI}}=\tau\cdot\text{PRF} \qquad \Delta R=\dfrac{c\,\tau}{2}\)
\(v_{blind}=\dfrac{n\,\lambda\,\text{PRF}}{2} \qquad d=\dfrac{\tau}{\text{PRI}}=\tau\cdot\text{PRF} \qquad \Delta R=\dfrac{c\,\tau}{2}\)
| PRF | Pulse repetition frequency (kHz). |
| f0 | Carrier frequency (GHz), for the velocity ambiguity. |
| τ | Pulse width (µs), optional — gives duty cycle and range resolution. |
| Rua | Maximum unambiguous range — beyond it, echoes fold into the next PRI. |
| vblind | Blind speeds where the Doppler shift is a multiple of the PRF (n = 1, 2, …). |
Reference: M. I. Skolnik, Introduction to Radar Systems, 3rd ed., McGraw-Hill, 2001.
Inputs
kHz
Pulse rateGHz
For velocityµs
Duty & ΔRResults
Range
PRI—
Unambiguous range Rua—
Duty cycle—
Range resolution ΔR—
Velocity
Wavelength λ—
Unambiguous velocity vua—
First blind speed—
Diagram