Mitsubishi Electric Aims to Improve In-flight Connectivity With Electronically-steered Array Antenna and RF IC
Mitsubishi Electric has announced an RF IC and a new electronically steered radio antenna that will deliver high-speed in-flight satellite connectivity.
The use of phased arrays is ever-expanding into all radio applications including 4G and satellite communications. Mitsubishi Electric has announced a new electronically steered radio antenna that will deliver high-speed in-flight satellite connectivity.
What Is Phased-Array Technology?
Phased arrays allow users to steer radio signals using electrical signals instead of mechanically rotating a radio receiver and dish.
The structure of Mitsubishi Electric's mm-wave antenna. Image used courtesy of Mitsubishi Electric
While phased arrays are more expensive and have a restricted field of view (120°), phased arrays do not use mechanical parts, making them less prone to mechanical breakage. Their electronic steerability means that they can change their direction in milliseconds as opposed to seconds.
Traditionally, phased arrays were often limited to high-end military applications for radar, but this is beginning to change.
Phased Array and 5G
One area, in particular, that is taking advantage of phased arrays is 5G. For instance, Keysight Technologies and the University of California San Diego built the world’s longest bidirectional phased-array 60-GHz link to work toward 5G's data rates.
To increase the maximum number of clients connected to a single 5G cell while maintaining high data rates, developers are increasingly employing beamforming.
Beamforming (in contrast to massive MIMO) essentially means that the signal streamed from the cell is formed into a beam and directed to a client. By doing this, the beam can be more intense and use a large portion of the radio bandwidth without interfering with devices that aren't in the beam zone.
Using multiple phased arrays with thousands of antennas produces multiple beams, which do not interfere with each other.
The Phased Array System
One problem that traditional commercial radio systems have is that they are often bulky and consist of mechanical parts. To make matters worse, the amount of data (both in volume and rate) consumed by internet users is increasing, which puts pressure on aviation companies to have better in-flight connectivity.
To solve these two problems, Mitsubishi Electric and Japan's National Institute of Information and Communications Technology (NICT) have developed an ultrathin active electronically steered array antenna whose structure is less than 3 cm thick.
The phased array system includes an antenna element, an RF-IC, heat radiator, and sub-board designed to work on the Ka-band (27 GHz to 40 GHz). Mitsubishi claims the device can be easily installed onto the top of an aircraft.
Mitsubishi Electric's active electronically steered array antenna (AESA). Image used courtesy of Mitsubishi Electric
The use of the phased array technology means that the antenna does not need to be directly looking toward the target satellite; it instead uses beamforming technology to create a direct link and is expected to provide data rates of at least 100Mbps.
This will allow passengers to fully utilize high-speed internet services anywhere around the globe. The low-profile nature of the antenna also means that it can be fitted onto any aircraft regardless of size.
But the new phased antenna is only one half of the puzzle.
The RF IC
Mitsubishi Electric, Tohoku University, and Tohoku MicroTec Co. have also developed an RF IC to handle the radio array. The RF-IC is designed as a stack pair with two separate silicon dies that are connected to each other via 50 μm through-silicon vias.
The bottom stack of the RF IC holds the signal generator circuitry and is 750 μm thick while the top stack holds the signal control circuitry and is 50 μm thick.
Mitsubishi Electric's RF IC. Image used courtesy of Mitsubishi Electric
The RF-IC also includes high-power low-noise amplifiers for transmission/reception with the amplifiers having a power efficiency of 29.1% (conversion of DC input to RF output) and a noise figure of 1.8 dB.
Since the demands on data speeds will always increase, Mitsubishi Electric has teamed up with Tohoku University and Tohoku MicroTec Co. to develop a specialized RF IC for working with future antenna systems on the 40GHz to 75GHz radio frequencies.
Phased Arrays: A New Norm?
Phased arrays are complex in nature but provide massive benefits to radio systems.
While they do not have 360 degrees of freedom and can be expensive to implement, they are immune to mechanical failure, can sweep incredibly fast, and provide advanced beamforming techniques to increase data rates while reducing interference.
As technology continues to improve, it's possible that phased arrays will become the norm in radio technologies including internet, cellular networks, and even general radio applications.