Antenna array

Many small antennas can work as one.

They connect to send or catch radio waves. These waves carry signals to us.

When they work together, they make a strong beam. This beam can point in one direction. It is like a bright flashlight.

Some arrays use many tiny antennas.

These can be thousands of parts. A larger array makes a narrower beam.

Some smart arrays can move the beam. A computer helps them point. They do not have to move at all.

These tools help us talk and see TV. They even help us look at space.

An antenna array is a group of antennas. They work together as one single antenna. This helps them send or catch radio waves.

Each small part is called an element. Most arrays connect many elements to one transmitter or receiver.

These elements use a trick called interference. When waves arrive at the same time, they add up. This makes the signal much stronger in one direction. This is called constructive interference. In other directions, the waves can cancel each other out. This is called destructive interference. By using this trick, an array makes a narrow beam. This beam is like a strong flashlight of radio waves.

Some arrays are very smart. A phased array uses a computer to point the beam. It can move the beam without moving the antenna. This is very useful for military radar.

Other arrays are used to study space. Scientists link large dishes together to make a giant array. This helps them see much more clearly.

An antenna array is a special group of antennas working as one. Instead of using just one piece, many small antennas called elements work together. These elements connect to a single transmitter or receiver through lines that carry power. This setup helps send or catch radio waves much better than a single antenna could. By using many elements, an array can create a narrow, strong beam of waves. This is known as high gain or directivity.

These arrays work using a clever thing called interference. When the radio waves from each element combine, they can add together or cancel out. When the waves arrive at the same time, they add up to make a stronger signal. This is called constructive interference. In other directions, the peaks of one wave might meet the valleys of another. This causes the waves to cancel each other out, which is called destructive interference. This process allows the array to focus energy into a specific direction, much like a flashlight beam.

There are many different ways to build these arrays. A broadside array sends waves out perpendicular to the flat plane of the antennas. An endfire array is a line of antennas that sends waves along the line itself. Some arrays are flat, which are called planar arrays. Others, like the Yagi-Uda antenna, use a single driven element and other parts called parasitic elements. Even large circular arrays exist, which people sometimes call "elephant cages" because of how they look.

Some arrays are very advanced and use computers to move their beams. A phased array uses a computer to control phase shifters for each element. This allows the antenna to point its beam instantly in different directions without moving the physical hardware. Military radars often use these highly sophisticated systems. Some use an Active Electronically Scanned Array, or AESA, where every element has its own module. This allows the system to send out many beams at once.

Antenna arrays are used in many parts of our world. You might see a reflective array used for UHF television antennas on a roof.

In space science, researchers use radio interferometers to link many large dishes together. This creates a massive array that can see the sky with much higher resolution. Some scientists even use Very Long Baseline Interferometry, or VLBI, to link dishes on different continents. This creates a giant virtual antenna that is thousands of miles wide.

An antenna array is a collection of multiple connected antennas that function together as a single unit. These individual antennas are known as elements. They are usually linked to a single transmitter or receiver through feedlines. These lines provide power to the elements in a specific phase relationship. By working together, an array can achieve higher gain, also called directivity. This means the antenna can produce a much narrower beam of radio waves than a single element could alone. In general, using more elements results in higher gain and a narrower beam.

The way these arrays work relies on the principle of interference. When a transmitting antenna sends out waves, the electromagnetic wave at any point is the vector sum of the waves from each element. If the currents are fed with the proper phase, the waves combine through constructive interference. In this process, the waves add together to enhance the power in a desired direction. Conversely, in directions where the waves arrive out of phase, they undergo destructive interference. This occurs when the peak of one wave meets the valley of another, causing the waves to cancel out. This mechanism creates a strong main lobe in one direction and weaker signals called sidelobes in other directions.

Arrays can be categorized by how the elements are arranged or how they radiate. A broadside array is a one or two-dimensional setup where the main lobe is emitted perpendicular to the plane of the antennas. To achieve this, the antennas must be fed in phase. An endfire array is a linear arrangement where the radiation travels along the line of the antennas. In an endfire array, the phase difference between adjacent antennas must equal their separation. There are also specialized types like the collinear array, which uses vertical dipoles in a line for high gain. Another type is the circularly-disposed antenna array (CDAA), where elements are arranged in a large circle. These large circular structures are sometimes nicknamed "elephant cages."

Some arrays are designed to be flat, which are called planar arrays. A common version is the reflective array, which places antennas in front of a metal plate or wire screen. This setup is often used for UHF television antennas. Another type is the curtain array, which consists of wire dipoles suspended in front of a vertical reflector. For smaller needs, microstrip antennas use patch antennas on a printed circuit board. These are frequently used for satellite television receiving. Even more specialized is the conformal array. These arrays are not flat but instead follow a curved surface. They are often built into the skin of aircraft or missiles to reduce aerodynamic drag.

Advanced technology has led to the development of the phased array, or electronically scanned array. In these systems, a computer controls phase shifters for each individual element. This allows the antenna to steer its radio beam electronically to any direction over a wide angle. The beam can move instantly without any physical movement of the hardware. A Passive Electronically Scanned Array (PESA) uses a single transmitter to feed all elements through these shifters. A more sophisticated version is the Active Electronically Scanned Array (AESA). In an AESA, every single element has its own dedicated transmitter or receiver module. This allows the system to radiate multiple beams at different frequencies at the same time.

Phased arrays are widely used in military radar systems. One example of a large-scale radar is the Nebo-M, a Russian mobile air defense radar. It uses 175 folded dipole antennas to create a vertical fan-shaped beam. This beam can be swept horizontally across the airspace. Beyond military use, arrays provide path diversity, also known as MIMO, which helps make communications more reliable. They are also used for radio direction finding (RDF) and for canceling interference from specific directions. These capabilities make arrays essential for modern electronic communication and surveillance.

In the field of radio astronomy, arrays reach incredible scales. Scientists use radio interferometers to link multiple large parabolic antennas together. This technique, called aperture synthesis, allows the array to have the resolution of a single antenna with a diameter equal to the distance between the elements. The most extreme version is Very Long Baseline Interferometry (VLBI). In VLBI, radio dishes located on separate continents are linked together. This creates a virtual array antenna that is thousands of miles in size, allowing for incredibly detailed observations of the universe.