Phased arrays are used in both radar and communication systems. Clearly, the first wide spread use of phased arrays was in military radar systems. Phased arrays have also been used in weather radar and for commercial air traffic control. More recently, phased arrays are finding use in communication systems such in satellites, and for ground based SATCOM for non-geostationary satellite communication.
What is a phased array? A phased array is a system that uses a multitude of individual antenna elements each with phase control. The phase control allows the antenna radiation pattern to be scanned electronically to track targets or to maintain a communications link.
The figure below shows a simplified block diagram of a phased array. It shows the T/R modules, antennas, and the beam forming network.
The ability to form multiple simultaneous beams means that the radar can simultaneously track multiple targets. This is very useful to applications such as airborne platforms where target may include other air planes, missiles, and ground targets.
To understand the usefulness of phased arrays for ground based satellite communication (SATCOM), it is helpful to first contrast it with communication to geospatial satellites. The familiar satellite television (TV) systems use reflector antennas which are aligned to the satellite and fixed in position. This is possible because the satellite is geo-stationary which means it is fixed in a particular location above the surface of the earth. For systems where the satellite is non-geostationary (which means it moves across the sky in orbit aground the earth), the ground antenna must track the position of the satellite as it passes by. In this case, the ground station can mechanically move the antenna and there are many commercial systems that use mechanical scanning. However, mechanical movement can have reliability issues, are bulky (volume), and heavy (weight). For many systems, a more attractive option is to use an electronically scanned phased array.
Another example of how phased arrays can be useful for satellite TV reception is for systems where the satellite is geo-stationary but the receiver is moving. An example is for automotive or marine applications where an automobile or ship is in motion but the satellite is fixed. The receiver must track the satellite and electronically scanned phased arrays are very attractive for this application.
Phased arrays are also useful for terrestrial communication systems such as small cell networks. The function they provide is to steer the antenna to minimize interference with nearby cell access points and they allow the antenna pattern to be dynamically modified to optimize user experience. This is important for some self-organizing networks (SON) approaches.
Phased arrays also provide the ability for terrestrial back haul networks such as point-to-point systems to be installed without the need for costly alignment procedures. Fixed beam antennas are often manually aligned so that their antenna pattern points to its connection point. Phased arrays can also benefit point-to-point systems by allowing automatic re-alignment.
Q&A on Phased Arrays
Why are Phased Arrays so Important?
Phased arrays have traditionally been used only in military systems such as radar for fighter planes and naval ships. However, they are now used or slated for use in communication systems, and consumer products.
What type of consumer products use phased arrays?
Phased arrays are planned for use in mobile phones for 60GHz high data rate communication links. They are also planned for use in satellite internet access systems.
How can MPT help with our phased array project?
MPT offers several products and services to support your phased array needs. We develop full phased array solutions for L-Band, C-Band, X-Band, Ku-Band, and Ka-Band. We also offer subsystems and components to support your phased array needs.