Sub-6G and mmWave Tech Cuts Through the Haze of 5G Antenna Design
Antennas were once considered a passive element in the radio frontend. Now, just starting the 5G conversation requires active multiplexing and electronic beam steering.
Fixed frequency bands with limited bandwidth aggregation—like AM, FM, or early cellular—did not require any type of active control over antenna coupling.
But 5G is different.
Overcoming the antenna challenges associated with 5G communications requires innovation, simulation, and a deeper appreciation for fundamental RF principles. Companies looking to address these challenges might turn to several antenna solutions.
8x8 PCB-based antenna-in-package for mmWave designs. Image used courtesy of TMYTEK
While some companies are zeroing in on high-performing antennas for sub-6G (like antenna and RF developer Antenova), others are tackling the 5G mmWave bands. For instance, mmWave solution provider TMYTEK is focusing on new antenna-in-package (AiP) designs. Alternately, satellite pioneer C-Com Satellite Systems is producing a 1024-element phased-array antenna for the Ka-band.
What design challenges are these 5G antenna developers up against?
The Challenges of 5G Antenna Design
For starters, the speeds are greater, which requires wider bandwidths.
The 5G frequency operating bands for sub-6G can range from ~600 MHz (New Radio 71) up to over 5000 MHz (New Radio 79). Because the total bandwidth for each radio band varies, carrier aggregation will allow for some bandwidth flexibility.
Then, designers must deal with the coexistence of antennas on user equipment (U.E.) with frequency ranges for 5G—namely sub-6G and the Ka-band—in addition to 4G LTE, Bluetooth, Wi-Fi, and GPS.
Finally, the physical medium for RF plays a massive factor in 5G performance. Signal loss through absorption and scattering, especially at mmWave frequencies, can wreck a designer's RF link budget.
Active Antenna Solutions for the 5G Future
Despite the challenges of 5G antenna design, there are solutions available for sub-6G today and mmWaves tomorrow. Active antennas are one such solution.
Block diagram for two types of active antennas: multiplexed matching networks (left) or aperture tuning (right). Image used courtesy of DIGI International
Multiplexer matching networks are one possible innovation to overcome the difficulty of many radio frequency bands. Another possibility is direct aperture tuning of the antenna (PDF) to change the coupled frequencies.
Tuning the elements of the antenna dynamic allows for coupling at various frequencies. Image used courtesy of Peregrine Semiconductor
Sub-6G antenna technology is an extension of existing methodologies. However, mmWave technologies will require a different approach.
Overcoming mmWave Signal Fade with Phased Arrays
An ideal 4G LTE antenna would be nearly isotropic and perform well regardless of how the user holds the phone. Unfortunately, this isn’t possible for mmWave RF signals because the signal fade can be extreme and systems require high-gain antennas for both base station and U.E.
Beamforming technologies are one key solution for generating high-gain antennas. The ability to constructively generate highly directive (high-gain) antenna patterns, especially electronically-steerable patterns, will be critical to a viable RF link budget.
A 16x16 antenna array pattern using beamforming at 26 GHz. Image used courtesy of Altair
C-Com Satellite Systems recently announced good test results for its newest electronically-steerable Ka-band flat panel phased array. These modular panels are purported to grow from one percent of the antenna market today to 15 percent by 2030 according to Dr. Leslie Klein, President and CEO of C-COM Satellite Systems.
What Is an Antenna-in-Package?
Designers must get out of the air and down to the board level to deal with signal losses as well. On a PCB, loss is proportional with increasing frequency, and long traces to the antenna cannot be accommodated. AiP technology could address these losses by incorporating the antenna structures directly on a package with the radio frontend.
mmWave block diagram for a beamforming antenna array. Image used courtesy of TMYTEK
AiP technology has several design considerations to account for such as antenna type, signal feed, chipsets (beamforming, mixing, controllers), filtering, and thermal.
5G antenna design comes with a host of design challenges that are both daunting and exciting. Drawing upon fundamental design principles with innovative radio frontend design will be key to a real-time 5G future.
Are you working in 5G antenna design or application? What constraints are key to your design decisions? Let us know in the comments below.