FMCW Radar: Advantages and Disadvantages

This page explores the advantages and disadvantages of FMCW (Frequency Modulated Continuous Wave) Radar. It covers the benefits and drawbacks of this technology, along with a basic overview of how FMCW radar works.

What is FMCW Radar?

Introduction:

Traditional CW (Continuous Wave) or Doppler radar is effective at detecting moving objects but cannot directly measure the range or distance to the target. FMCW radar overcomes this limitation.

FMCW radar systems are capable of detecting objects, measuring their range (distance), and determining their radial velocity (speed towards or away from the radar). As the name suggests, FMCW radar transmits a continuous wave signal where the frequency is modulated (changed) over time.

In FMCW radar, the transmitter frequency is continuously varied at a known rate. The reflected signal is received and compared with the transmitted frequency at that instant. This comparison allows the radar to determine the range to the target.

Radar systems typically consist of both a transmitter and a receiver.

The FMCW radar uses the following equation to determine the range to the target:

R = Vo * Δt / 2

Where:

Δt = T * { Δf / (f2 - f1) }

And:

• Vo = Velocity of the EM wave (speed of light)
• T = Period of the frequency sweep from f1 to f2
• f1 = Minimum frequency of the sweep
• f2 = Maximum frequency of the sweep
• Δf = Difference between the transmitted and received instantaneous frequencies

FMCW radar is commonly used for:

• Determining the slant range to a target
• Measuring the height of a target (altitude)
• Determining the bearing and elevation angles of a target

Benefits or Advantages of FMCW Radar

Here are the key benefits and advantages of using FMCW Radar:

• Altimeter Applications: FMCW radar is often used as an altimeter, particularly in aircraft, to measure the height above the ground.
• Low Power Transmission: It uses relatively low power for transmission, which can be easily supplied by solid-state devices like magnetrons, BWOs (Backward Wave Oscillators), or reflex klystrons.
• Good Sensitivity and Stability: The super-heterodyne-based receiver architecture provides good sensitivity and stability.
• Higher Bandwidth: It offers a higher bandwidth compared to traditional CW radar systems.

Drawbacks or Disadvantages of FMCW Radar

While FMCW radar has many benefits, it also has some drawbacks:

• Short Range Applications: Primarily used for targets at relatively short ranges due to the lower peak output power.
• Signal Attenuation: The lower transmit power means the signal is more susceptible to attenuation (weakening) and atmospheric/channel effects before it reaches the receiver.
• Higher Cost: Generally more expensive compared to pulsed radar systems.
• Interference: Transmissions from FMCW radar can be interfered with by other nearby radio systems because of the large range of frequencies used and the low peak power of the transmitter.