Radars were made to send out radio waves and use the echoes to find the range, direction, speed and size of objects. This means that their dish spins to sweep radar beams.
Keep reading on to find out more about radar dishes.
What is a Radar Dish?
A radar dish is a round, concave antenna used to detect the presence of objects by reflecting radio waves off them. They are also known as myriads or parabolic antennas depending on the size of the dish.
Large parabolic dishes are usually found mounted on towers or buildings while small ones can be placed in cars, airplanes, helicopters, ships, boats, unmanned aerial vehicles (UAV), and balloons. Along with countless uses in the military.
Why do Radars Spin?
Radar dishes spin to enable them to scan a wide area with greater focus by moving the position of the target being scanned. They also have different scanning modes that can be used depending on what they are tracking, whether stationary objects or moving ones.
In addition, spinning radar dishes allow the radar to operate in both horizontal and vertical planes at the same time while non-spinning dishes only work in one plane at once. Spinning radar dishes also ensure that during heavy weather conditions (e.g., heavy winds) when the antenna tilts over, it will always face the general direction of the target if it is spinning.
A radar dish on a tower generally spins because its orientation can be adjusted by rotating it around an axis which runs through its center, up and down or side-to-side. Some dishes are large enough to have two motors – one for changing their angle in line with the Earth’s axis (e.g., Altitude) and another motor for tilting them based on geographical location (e.g., Azimuth).
Smaller dishes are often fixed in place or may even spin on an unstable base that is controlled electronically via gyroscopes which indicate how far off horizontal they are tilted.
Why are Radar Dishes Shaped like that?
The shape of radar dishes has to do with the way waves are emitted from them. When a wave is emitted it spreads out in all directions but as it travels away from the dish, its energy decreases. More importantly, if the dish was not shaped like that then the energy would be very low at angles other than those where they hit it perpendicularly which means that less of the wave’s energy would bounce back off-targets and return to receivers.
This would make radar signals weak or even undetectable depending on how far away the target is. The curved shape redirects some of this energy towards angles where it can reflect off objects more easily making for stronger returns which allows radars to detect moving objects over greater distances.
Radar dishes are also shaped this way because it helps them focus their emitted energy into a tight beam which improves the accuracy of their measurements.
The best way to understand the shape of radar dishes is to think about how waves spread out. If you were to draw straight lines along the direction where they flow, these would show angles at which each wave-front can be found once emitted from its source. Waves are generated by vibrations so drawing lines parallel to the axis of vibration (i.e., vertical) will indicate how far apart in space objects need to be for one wave to arrive after another has left and vice versa.
Does the Size of the Radar Dish Matter?
Yes, the size of the radar dish matters. The larger or wider the dish, the more power it can handle and process.
Radar dishes need to be wide so they can both spread out the task of surveying an area and also have enough power to get a strong signal sent back. The larger the dish is, the more sensitive it becomes.
Not only that, but it becomes much easier for this type of antenna (AESA) to determine where objects are when there is less overall surface area in contact with the atmosphere. This makes these radar systems good at spotting targets that might be obscured or hard to see using other types of systems.
It also makes it very useful for boats to have a high-resolution picture of their surroundings.
What Material are Radar Dishes made of?
Radar dishes are most often made out of aluminum because it is inexpensive but also highly conductive and malleable, meaning that it can be easily shaped into many different sizes or designs. This makes it perfect for creating antennas (which require a conducting medium) that need to be strong enough to withstand wear and tear while still being lightweight enough to transport about on mountable devices like ships, planes, helicopters and more.
Copper has similar properties except it’s not as strong so it’s mostly used in smaller-sized radar dishes where its more malleable properties are needed.
Radar’s Three Different Scanning Modes
As mentioned earlier, radars can detect stationary objects as well as moving objects. They also have three different scanning modes which are pulse-Doppler, moving target indicator (MTI) and conical scan.
Pulse-Doppler radar dishes can determine the velocity of an object by recording the time it takes for a single wave to leave the transmitter, bounce off the object, return to the receiver and how this impacts its frequency. For stationary targets, pulse-Doppler dishes work just like regular non-spinning radars while for moving targets they use their Doppler shift changes in frequency measurement to calculate their speed.
Moving target indicator dishes operate similarly to regular non-spinning radars but have two antennas – one which emits microwaves and another that registers returning waves. A signal from the emitted microwaves is used to determine if a target is stationary or moving. If it bounces back at the same interval of time and has the same frequency as when it was sent, then its assumed to be stationary.
MTI radars also record more information about stationary objects such as their type (e.g., building, trees) and location (e.g., coordinates). With this additional data, they can report on what types of changes are occurring in the location of interest (e.g., deforestation) or how long these changes have been happening (e.g., five years).
Conical scanning radar dishes scan areas with a conical shape and consist of both rotating and non-rotating components. They start by rotating the dish at a slow speed and then gradually increase it. This allows them to cover wide areas without missing anything within that area. Radars with conical scanning dishes are good at detecting stationary objects as well as those which might be obscured by tall buildings, mountains or dense foliage.
Final Words
Radar dishes are an important component of any system using radio waves to detect moving objects. Their main purpose is to beam out focused energy in order to detect and track moving objects while also sending back the energy that has bounced off these same targets. Spinning enables them to scan a wide area with greater focus.
The shape of radar dishes is important because it helps them to better focus the energy they emit when in use at a specific angle. The bigger, wider and more powerful radar dishes are, the more sensitive they become to objects moving in their direction, especially when these objects are obscured or hard to get an accurate picture of.
