Phased array antennas: From military to 5G
Article By : Carolyn Mathas
Phased-array antennas are gaining traction in 5G systems, promising improved signal strength, gain, directivity and bandwidth performance.
Phased array technology is far from new. Phased-array antennas have been used for decades in a variety of military applications. Now, however, their use in 5G systems in the Band 2 frequency range is rapidly gaining traction, promising improved signal strength, gain, directivity and bandwidth performance.
A phased array uses an antenna element arrangement so that the relative phase of each element is varied to steer a radiation pattern or beam. The antennas are connected by a system of microwave transmission lines and power dividers. A phased array antenna is designed to control the direction of an emitted beam by exploiting interference between two or more radiated signals, or “beamforming.” The antenna enables beamforming by adjusting the phase difference between the driving signal sent to each emitter in the array. The number of emitters in a phased array antenna range from a handful to literally thousands.
When signals from each emitter are perfectly in phase, they interfere constructively and produce intense radiation in a specific direction. This direction is controlled by setting the phase shift between the signals transmitted to different emitters. A slight time delay between signals transmitted to successive emitters controls the phase shift. Using phase shifters enables hundreds of beams to be synthesized in phased array antennas.
Phased array antenna types include:
- Linear arrays, where array elements are placed in a straight line with a single-phase shifter. In this case, beam steering is limited to a single plane and arranging several linear arrays vertically forms a flat antenna.
- Planar arrays, where each antenna has a phase shifter. A matrix arrangement of individual antennas forms the planar arrangement, and the beam can be deflected in two planes. It requires a high number of phase shifters, however, increasing complexity and cost.
- Frequency scanning arrays, whereby its antennas do not require phase shifters. Beam steering is controlled by the transmitter’s frequency.
Figure 1 This is how phased-array antennas work in theory. Source: Analog Devices Inc.
Recently, digital beamforming supporting multiple beams simultaneously is seeing advances. Replacing existing circuitry with a wireless network provides the ability to reconfigure and add elements, operational adaptability, and ease of upgrading system performance via software. With digital beamforming, narrowband limitations are removed, allowing for wideband operation. Multiple radar, communications, and electronic warfare functions will eventually be served by a single antenna with this architecture.
Phased-array antenna applications
Within the military/space realm, phased array technology in radar applications provides greater performance and flexibility, a low profile, rapid repositioning, and ease in tracking multiple targets. For military communications, it enables simultaneous access to multiple unmanned aerial vehicles and low-earth orbit satellites while facilitating faster and cost-effective signal hand-off. Electronic warfare use cases include electronic attack and protect platforms, enabling directivity control of jamming signals and accurate hostile signal location, even in electromagnetically noisy environments. And, in space, it’s able to meet bandwidth demand in satellite applications.
Now, however, the 5G realm advances in phased array technology are front and center. A phased array antenna is critical for 5G to achieve wider bandwidths, coverage, and greater capacity in the millimeter-wave spectrum. Although millimeter-wave systems are relatively easy to deploy in short-range indoor applications, their use outdoors, however, results in propagation loss, rain fades, atmospheric absorption, and high attenuation and shadowing.
Recent semiconductor technology advancements are resulting in more cost-effective phased array technology that is being used in satellites, radar, and 5G. Starlink, for example, is a phased array antenna system that incorporates hundreds of small antennas, synchronized with picosecond precision. Adjusting for delay between antennas, a Starlink device tracks satellites across the sky without mechanical movement.
Recently, Analog Devices and Keysight Technologies have announced that they are collaborating to advance phased array technology adoption. Analog Devices’ phased array platforms are currently used to accelerate beamforming developments and Keysight provides phased array test solutions. The collaboration aims to provide a total design, test, and calibration ecosystem solution that accelerates time to market.
Figure 2 Testing and calibration is an important part of phased-array antenna technology ecosystem. Source: Keysight Technologies
Keysight says that it has brought phased array test times from minutes to seconds, claiming a 70x faster measurement speed while maintaining high accuracy. On the other hand, Analog Devices has unveiled a software reference design for its 32-element hybrid beamforming phased-array development platform along with design examples to reduce prototyping time for hybrid beam steering and system phase calibration.
Future of phased array technology
There are challenges. While today’s digital phased array radios and differential RF front-ends are improving linearity, noise, and dynamic range in the transceiver chain, they are still less efficient. 5G and beyond will require efficient wideband performance and low-complexity antenna arrays that can be executed using only one step.
Millimeter‐wave frequencies require scalability and manufacturability that is still in the works. Achieving antenna-array simplification, bringing down the cost, accomplishing efficiency gains, and adding wide‐scan features are all on the drawing board. A new-found interest and collaborative efforts are likely to spur rapid advances.
This article was originally published on Planet Analog.
Carolyn Mathas has 15 years of journalism experience, the last seven of which have been spent on the EE Times Group’s DesignLines, including PLDesignLine, Network Systems DesignLine, Mobile Handset DesignLine, and her current sites, Industrial Control DesignLine and CommsDesign. Prior to joining UBM in 2005, she was a senior editor at Lightwave Magazine and a correspondent for CleanRooms Magazine. Mathas has a BS in marketing from University of Phoenix and an MBA from New York Institute of Technology. She lives in the Sierra foothills and claims that the pine forest, snow, mountain air, bears, and power outages balance her deadline-packed high-tech career.
