Any drone user with a military background may have wondered at times if drones show up on radar. But it’s a bit of a loaded question. The answer is, YES and NO. But the real question should be, if the radar system picks up a signal, does it recognize a drone/UAV when the radar picks up a return or blip?
Yes, drones can and do show up on Radar. Radar will pick up a drone, but it may not be able to identify that object for what it is. However, in some cases, the object may not even show up, depending on how sensitive the system is and how much radar clutter has been programmed out.
To understand how this works, we need to look at a few things.
What is Radar?
First, let’s take a look at what RADAR is. RADAR is actually an acronym for RAdio Detection And Ranging. RADAR is a multiple component system, and also there are different types of radar and different applications. Lidar for example is a type of radar that uses infrared light and lasers.
Most Radars though use Electromagnetic Radio Waves and this is the focus of the type of RADAR we’re looking at. Radar systems typically will consist of the following components:
- Transmitting antenna
- Receiving antenna
The Transmitter produces radio waves or what is referred to as Radar signals. It is these radio waves/radar signals that are then sent out from the Transmitting Antenna (can also be called Transmitting Aerial – aerial is another term for antenna).
These radio waves/radar signals are sent out in predetermined directions. When these radio waves/radar signals make contact with an object, be it a plane, drone, bird, weather – the radio waves/radar signals will usually reflect back to the Receiving Antenna/Aerial, or they can scatter.
Sometimes the radio wave is absorbed and penetrates the object it makes contact with, producing no readable return and making that object very difficult to detect, much like the Stealth aircraft is designed to do.
What happens to the radio wave/radar signal when it makes contact with an object can vary. This can depend on what the object is made of or even atmospheric conditions like fog or rain. For instance, the Stealth Aircraft was designed to be hard to detect by radar by absorbing or redirecting the radio wave/radar signal.
The principle behind this is that the radio wave/radar signal doesn’t reflect back directly to the receiving antenna/aerial. Heavy rain or thick fog could cause massive radar clutter blocking and scattering returns from more solid objects, almost as if masking them.
The radio waves that reflect back though, are able to be picked up by the receiving antenna/aerial and the receiver. It is these reflected radio waves/radar signals that are reflected back from the object it makes contact with. The processor is able to read and process the return data in some cases into an identifiable object based on the database of information it has to work with and other factors.
Limitations of Radar
There are limits to the area a Transmitting Antenna/Aerial can reach. The amount of power the antenna/aerial uses is also important to its range and depth of field.
It is due to these limitations that we get terms like “Flying under the Radar.” Most antenna arrays send out a linear path signal, depending on the wave signal range and depth. It could be possible to fly below the Radio waves/radar signals.
A RADAR may not be set to detect anything below say 400 feet, or it may be set to not detect small objects which can also be known as clutter. The processor may be set in this manner to limit the amount of clutter that is being picked up or reflected back.
Radar clutter is defined as unwanted back-scattered signals from physical objects in the natural environment like ground, sea, birds, etc.
It is these types of settings that may keep a drone from being seen or showing up on radar.
Also, RADAR antennas come in many different shapes and sizes. They have two main types based on their physical structure. The type of antenna/aerial used can make a very big difference as to the range and depth of the area they are able to cover.
The two types are Parabolic Reflector Antennas and Lens Antennas.
The Reflector-style antenna/aerial comes in a variety of sub-styles like Gregorian, Parabolic, Cassegrain, Splash Plate, Offset Feed, etc. Reflector antenna/aerials are the most commonly found and are the type you might see at an airport or being used by your local meteorologist to forecast the weather, or even aboard a sailing vessel. Range and detection vary from type to type.
Another determining factor in a RADAR system’s ability to reach out and detect objects is determined by the strength of the radio wave/radar signal being sent out and the strength of the receiver to pick up the signal. Some of the most powerful RADAR systems are used by military powers around the world.
Types of Radar
There are different types of RADAR.
First, there is Pulse Radar. This type of radar is used for detecting stationary objects. There is also a type of pulse radar called MTI Radar (Moving Target Indication Radar). MTI Radar is used to track non-stationary or moving targets.
Pulse radar transmits a pulse signal at every clock pulse with the object being read or seen between pulses. Pulse radar can use a single antenna/aerial to transmit and receive.
The next type of radar is Continuous Wave Radar. This type of radar uses Doppler Effect for detecting stationary and non-stationary objects. These types of radars are known as Unmodulated Continuous Wave Radar and Continuous Wave Radar, or more simply CW Radar or UCW Radar.
These style radars require two antenna/aerials, one to transmit and another to receive. If the CW Doppler Radar uses Frequency Modulation it would be known as FMCW (Frequency Modulation Continuous Wave Radar) sometimes referred to as CWFM (Continuous Wave Frequency Modulation). This style of radar is used most often for weather forecasting.
The last type of radar would be MTI Radar (Moving Target Indicator). This type of radar also uses the Doppler effect for distinguishing non-stationary objects from stationary objects. They are usually equipped with an Amplifier or Oscillator.
These types of radars can use a single antenna/aerial as both a transmitter and receiver with the use of a duplexer. Or MTI Radars can employ two antenna/aerials still. A duplexer allows for the signal to be transmitted and received by the same antenna/aerial. These style radars are the most frequently found.
Can Radar identify a drone?
We’ve covered what Radar is, what it does, and how it does it. To this point, we know that if an object is within the Radio wave/radar signal, then it will be detected, as long as it reflects the wave back to the receiver.
What we haven’t really covered though is if the processor will recognize the object (say, a drone). So, let’s get into that now.
What does radar actually detect? Here’s the crux of the discussion. Radar can only detect the position and speed of objects. Now if we leave it there, the answer to our question changes from yes to no. Or does it?
Whether the radar will identify a drone all comes back to the processor and its database and the settings. Would the radar be able to detect a small object the size of a bird or drone? Yes, it would.
We know that if that small object reflects the radio wave/radar signal back to the receiver, it will pick it up as an object, providing its position and speed. But we also know that radars are programmed to cut down on radar clutter. After all, every time a bird flies into the radio wave/radar signal it will show. That could be a whole lot of clutter.
So the drone could easily be cut out as just one more piece of clutter. This would mean that that drone effectively does not show up on the radar at all.
One other piece of information that does come back in the reflected radio wave or signal is the size of the reflection. More sophisticated radars can, based on this information and a database of stored radar profiles, determine to some degree the nature of the object.
So how does a Radar Operator know what he/she is seeing? That would be dependent on which radar system they are using.
Air Traffic Controllers use two radars for example.
The first is the primary radar. This radar is for basic detecting and ranging and only provides that information. The secondary radar used by Air Traffic Control is the Secondary Surveillance Radar (SSR). This Radar works with the aircraft’s transponder and provides more information to the controller than the primary radar does.
The transponder is one of the main ways for an aircraft to be identified. Another is by radio communication with the aircraft. By giving their position to the radar operator, the pilot is able to identify and position the aircraft on their radar positioning.
So, one of the main ways of identifying an object on radar is by direct contact with the craft. Another means of identifying an object is by the Radar Operator marking the take-off and following the craft from there.
Another method is by the aircraft itself, and a device called a transponder. Transponders send out a code that identifies the aircraft. This code allows the Air Traffic Controller to know which plane is which, among other information about the aircraft.
As you can see, identifying an object on radar is not as easy as just seeing that there is an object there. So yes, a radar will pick up a drone/UAV but it may not be able to identify that object for what it is. The object may not even show, depending on how sensitive the system is and how much radar clutter has been programmed out.