How to Choose the Right Radar for Your Application

Radar is often the principal sensor for long-range/wide-area target detection. Getting the radar choice right for a project is absolutely critical; it can be the difference between "seeing" targets in time and missing them completely.

While highly specialised military requirements may limit the available options to just a handful, commercial projects typically benefit from a much wider selection of suitable models.

The selection process needs to be systematic, beginning with the application itself and moving on to performance criteria and practical realities.

 

Defining the Application and Target

The first consideration in selecting a radar is how and where it will be used, as well as the types of targets it will be looking for. These fundamentals will determine the type of radar required.

The radar must be appropriate for both its location and intended use. For instance:

 

• A coastal surveillance project looking for ships out to several miles will require a very different radar from a security project trying to detect drones or people within a kilometre.
• A radar for a sea-going vessel will have been designed to cope with the vessel's motion and salt spray.
• An air surveillance radar will be very powerful and use a specially-designed antenna, covering a large volume of airspace whilst minimising ground echoes.
• A radar designed specifically for small drone detection will likely be electronically scanned and include height measurement (3D capability).
• A perimeter security system monitoring for vehicles or intruders will need excellent ground clutter rejection and target classification capabilities.

 

Performance Requirements

Once the general radar type is established, the specific performance requirements should be considered. These needs will have a large impact on the final choice, often eliminating several options immediately.

Angular Resolution

A requirement for fine angular resolution will immediately necessitate a large antenna and/or a higher transmission frequency. For example, achieving a 1° beamwidth at X-band requires roughly a 2-metre antenna, whereas the same resolution at S-band demands approximately 7 metres.

Range Resolution

Range resolution dictates the minimum distance required between two targets positioned one behind the other (along the same radial line) for the radar to register them as two distinct echoes, rather than one merged blob. When considering a suitable radar, this metric is critical for high-traffic or complex environments. If you need to separate vessels close together in a busy channel, or resolve a small drone operating near a building, you need fine range resolution. This performance is achieved not through antenna size, but by the radar's transmitted signal properties: either a very short pulse in traditional systems, or the high bandwidth created by the changing frequency in FMCW radars, with the latter being ideal for detailed short-range work.

Detection Range vs. Tracking Range

Quoted maximum detection range depends on a target's size and reflectivity. Crucially, detection doesn't automatically mean the target can be reliably tracked.

While a target may produce a fleeting blip on a single antenna pass, reliable, continuous tracking requires the detection to meet a much higher certainty threshold. This is defined by the tracking initiation criteria; for instance, the target must be seen on "M-out-of-N" scans (e.g., a confirmed detection on 3 out of 5 consecutive antenna passes).

Because the signal return is weaker and less consistent at extreme ranges, the target can only satisfy this stringent, multi-scan rule at a shorter distance. Therefore, the Maximum Tracking Range is always considerably less than the Maximum Detection Range. This gap is what matters most when considering which radar model to choose.

Target Cross-Section Variations

The radar cross section (RCS) of a target isn't constant; it varies dramatically depending on aspect angle. A ship seen head-on presents a much smaller RCS than the same ship seen broadside. Aircraft RCS can vary by 20dB or more as they manoeuvre. This is why manufacturers' range claims need careful scrutiny; they're typically based on an assumed RCS that may not reflect your operational reality.

Update Rate

Fast-moving, highly manoeuvrable targets demand radars with fast update rates. For rotating systems, this translates directly into the antenna rotation speed (RPM). While the number of 'pings' or hits a radar puts onto a target per scan helps with initial detection quality, it is the time between scans, dictated by the spin rate, that determines whether a track can be maintained against a fast target changing direction. If the update rate is too slow, the tracking algorithm may lose the target or fail to accurately predict its next position.

Clutter Rejection

A radar's ability to detect targets depends not just on raw sensitivity, but on how effectively it can distinguish genuine targets from unwanted returns (clutter).

• Sea clutter from wave action can mask small targets in coastal and maritime applications. The severity varies with sea state and radar frequency; X-band systems see more detailed sea surface structure, which can be both an advantage (better small-target detection in calm seas) and a disadvantage (more clutter in rough conditions).
• Ground clutter from terrain, buildings, and vegetation dominates in land-based applications. Radars that incorporate Doppler processing (either pulse-Doppler or FMCW-Doppler) are much better at filtering the large clutter returns from stationary objects, buildings and terrain features.
• Weather clutter from rain, snow, and hail affects all radars but impacts higher frequencies more severely (as discussed in the frequency section below).

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About the author
Rob Helliar
Head of Customer Solutions, Cambridge Pixel