RADAR: Determination of Location & Speed
As we all know, RADARs determine the location (altitude & direction) and speed of objects (targets) within its range.This article introduces the guiding principle behind acquiring this information.
RADAR is an acronym for Radio Detection And Ranging. RADAR operates by emitting continuous or pulsed radio frequency electromagnetic signal over a distance (range) and scanning for reflections/obstructions. Most of the modern RADARs use a Phased Array Antenna(a set of multiple transmitting elements) for both broadcasting and receiving the signals.
When the transmitted signals encounter an airborne obstacle, the transmitted signals get partially echoed back. The echo/signal received back by the RADR is analyzed for:
- The time elapsed between the antenna broadcasting the signal and receiving the echo
- The amplitude modulation in the echo
- Frequency of the received signal
The power of the echo received is inverselyproportional to the fourth power of the distance between the RADAR and the target.
The velocity or speed of the object is estimated by analyzing successive echo signals and applying the Doppler principle. Remember how when a train is approaching, the whistle has a higher pitch than normal?
The same principle is at play in case of RADARs as well.
- The received signal has the same frequency of that of transmitted signal
- The frequency of the received signal is greater than that of the transmitted signal
- The frequency of the received signal is lesser than that of the transmitted signal
- The target is stationary (relative to RADAR)
- Target is moving towards the RADAR
- Target is moving away from the RADAR
While the working principle seems easy, the practical implementation can be extremely challenging due to the ground realities of its applications. We’ve listed down two of the common challenges involved in the operation and success of RADARs designed for surveillance of air-borne targets.
- Clutter: Is defined as the unwanted echoes resulting from ground, buildings and atmospheric turbulences. The system has to effectively distinguish these signals from the actual target for optimal operations.
- Jamming: Many military airborne vehicles (potential targets) are capable of emitting RF signals of their own to inflict noise and false information in an attempt to disrupt the radar operation. In response, modern RADAR systems rapidly switch the transmitter frequency of RADAR signal over a spread-spectrum as a counter measure. This form of electronic counter-countermeasure(ECCM) is called frequency hopping / frequency agility.
- Stealth: The advanced military aircrafts are being enabled with ‘stealth’ capabilities that include,
- Designing the airframe to avoid sharp corners and flat surfaces and
- Using radar absorbent material:
both of which help in greatly minimizing the amount of energy reflected back to the radar.
Did you know that CoreEL has designed and developed several systems & sub-systems for RADARs?
Get in touch with us if you’d like to hear more from our engineering team.Also, explore our careers sectionfor a role with our engineering team.