The Role of Beamforming and AESA Antennas in SATCOM Communications - Part 3

This is part 3 of our series that explores Low Earth Orbit (LEO) satellites and their pivotal role in various sectors, including telecommunications, Earth observation, scientific research and national security. Part 1: How Modern LEO Satellite Technologies are Changing the Space Race, Part 2: Advancing Communication: The Role of LEO Satellites in the 5G Expansion

Part 2 of this series provided an introduction to how beamforming and active electronically scanned array (AESA) technologies are helping to advance satellite non-terrestrial networks (NTN). Part 3 delves into how beamforming and AESA antennas are shaping satellite communication design trends and benefiting engineers in the field.

Beamforming is a signal processing technique used in antenna arrays for directional signal transmission or reception. This technology is crucial in wireless communication systems as it improves signal power, leading to enhanced performance and efficiency.

Beamforming, along with multiple-input multiple-output (MIMO) and AESA are foundational technologies in modern wireless communication, offering significant benefits in terms of signal quality, network efficiency, and user experience. Their applications span from mobile networks and Wi-Fi to satellite communications and radar, making them a critical tool in the advancement of wireless technologies.

What is an Active Electronically Scanned Array (AESA) or Active Antenna?

An active antenna, also known as a phased array antenna, consists of multiple stationary elements fed coherently. To form an electronic beam, each element is energized by the appropriate phase, and then a beam can be formed coherently in the far field for the desired direction. It uses variable phase control at each element to scan a beam to specific angles in space, as shown in Figure 1 below. This electronic beam steering, with no moving parts, is managed by ICs at each radiating element.

Learn More

Part 1: How Modern LEO Satellite Technologies are Changing the Space Race

Part 2: Advancing Communication: The Role of LEO Satellites in the 5G Expansion

Figure 1: Simplified one-dimensional planar array antenna with a row of isotropic radiators.

Active antennas with beamforming ICs have the advantage known as a soft failure mechanism, which means that the failure of a few elements typically has little impact on overall performance. Moreover, these AESA beamforming antennas can steer beams in microseconds and support multiple, simultaneous, independently steerable beams. With no mechanical parts, they are low-profile and reliable. Additionally, they can steer nulls and have high degrees of freedom to block interferers and jammers, enabling precise radiating aperture patterns.

For most NTN communications, antennas operate at mmWave in the GHz frequency ranges, like 24, 26, 28, 37, or 39 GHz. These high frequencies have short wavelengths, allowing many antenna elements to fit into a compact, highly directive aperture, offsetting high path loss, as shown in Figure 1 above. The highly directive beams also offer spatial diversity, enabling multiple beams to reuse the same frequency spectrum, which significantly increases system capacity.

What is Beamforming?

Beamforming can be executed in an analog or digital format, depending on the system requirements. We'll dig more into the individual architecture types later.

Beamforming involves manipulating the phase and amplitude of the signal at each radiating element in the array. This technique causes signals at specific angles to experience constructive interference while others experience destructive interference. This results in the RF energy being "focused" in specific directions, creating a beam-like pattern, as shown in Figure 2. In the figure below, we can see the steered beam in the antenna array creates a main lobe at a given angle and minimizes the side lobes. Beamforming increases the signal-to-noise ratio (SNR) at the receiver end, reduces multipath fading, and minimizes interference from other directions.

Figure 2: Beamforming signal lobes using AESA antenna.

AESA antennas can steer the signal beam using either phase shifters or time-delay units (TDUs), each with its tradeoffs. For systems operating with a larger instantaneous bandwidth, TDUs may be a better choice to avoid beam distortion, known as squinting, as shown in Figure 3 below. However, for lower operating bandwidth systems, phase shifters are sufficient and are the most broadly implemented solution. Note there are also architectures that incorporate both TDU and phase shifters into the same system. This also helps reduce squinting.

Figure 3: Beam squinting/distortion.

TDUs exhibit a constant phase slope over the frequency range and, therefore, remove beam squinting effects. While phase shifters exhibit constant phases over the operating frequency range, a phase shifter setting may result in different beam steering angles for different frequencies. This is why phase shifters work best for narrower system bandwidths.

Phase shifters electrically steer a beam by approximating time delay, resulting in an optimal beam at the center frequency. However, phase shifting can cause understeering at the maximum operating frequency and oversteering at the minimum operating frequency. Phase shifter architectures are significantly more cost-effective and, thus, more commonly used.

Ultimately, both methods work, but engineers must make tradeoffs for the best implementation. First, the array size and instantaneous bandwidth requirements are evaluated to determine if phase shifters are sufficient. Second, evaluate if a hybrid solution is sufficient where phase shifters are used at the elements and TDU is implemented behind some subset of elements within a larger array. If the instantaneous bandwidth and/or array size is large enough, TDUs may be required at every antenna element.

Types of Beamforming

Hybrid beamforming combines analog and digital beamforming, a technique popular in 5G mmWave networks. It mitigates the complexity inherent to using digital beamforming and reduces the RF chain components, thereby simplifying the overall system. Below, we describe and provide examples of the three beamforming architectures.

• Analog Beamforming: Requires an RF signal adjustment at each antenna element to steer the beam in the desired direction. This is simpler, often cheaper and lower power but less flexible compared to digital beamforming.
• Digital Beamforming: Each antenna element is connected to its own digital signal processor. The beam is formed and steered by digitally manipulating the signals. This can allow for more precise control and the ability to form multiple beams simultaneously from the same array.
• Hybrid Beamforming: Combines both analog and digital techniques, often used in systems where a purely digital approach would be too costly or complex.

Figure 4: Comparison between analog, digital and hybrid beamforming architectures.

Below we provide a table to assist in differentiating the individual types of beamforming described above.

Table 1: Comparison of beamforming types.

A Brief Look at Beamforming Wireless Applications

The wireless marketplace is beginning a move towards more beamforming SATCOM applications to provide higher throughput enabled by wider bandwidth frequencies. In cellular networks, beamforming can be used to improve bandwidth efficiency and coverage by enabling base stations to focus signals on individual users, reducing interference and increasing data rates. In Wi-Fi networks, beamforming can be used to enhance signal quality and range, particularly in crowded environments with many user devices. Moreover, satellite communications, using beamforming, are shaping the coverage area of satellite signals, allowing for targeted broadcasting and communication with specific regions. In radar system applications, beamforming enhances resolution and range by focusing transmitted pulses in the direction of interest, improving the detection of objects. We will discuss some of these applications in more detail in future articles.

A Final Word

This article explored the advancements in satellite non-terrestrial networks using beamforming and AESA technologies. We discovered how beamforming enhances signal quality and efficiency by directing electromagnetic energy, which is crucial for mobile networks, Wi-Fi, and satellite communications. By using AESA antennas, phase shifters and TDUs, today's systems can offer precise and reliable beam steering to further improve network performance, signal coverage, and data throughput in SATCOM communications. Moreover, we now understand how hybrid beamforming, combining analog and digital techniques, is particularly effective in 5G mmWave networks while helping to mitigate design complexity and costs.

As all these SATCOM technologies continue to advance, they will play a pivotal role in the development of next-generation wireless communication systems, allowing us to stretch our communication boundaries further and more reliably.

Links to other parts in this series: Part 1: How Modern LEO Satellite Technologies are Changing the Space Race, Part 2: Advancing Communication: The Role of LEO Satellites in the 5G Expansion

For more on this topic and solutions, we encourage you to view these collateral pieces - our webinar Key Components for LEO Satellite Systems, our sponsored eBook RF Technology Trends for LEO Satellite Systems, and our blog on Ka-Band Satcom Trends and Power Amplification Challenges. Additionally, you can find more interesting collateral on this subject by visiting our Design Hub for a rich assortment of videos, technical articles, white papers, tools and more.

For more information on this and other Qorvo 5G and 6G base station design solutions, please visit Qorvo.com or reach out to Technical Support.

About the Authors

James Cheng, Senior Product Line Manager

James is responsible for Qorvo's Defense and Aerospace small signal product lines including modules, LNAs, mixers and drivers. James has extensive industry experience in RF and mmWave integrated circuits used in a wide range of applications such as radar, SATCOM, cellular, and connectivity. This vast experience enables him and his team to think outside-the-box and optimize RFIC solutions to help solve the toughest RF design challenges.

David Schaufer, Technical Marketing Communications Manager, MBA

David is an experienced technical communicator at Qorvo, where he serves as the public voice for the company's technical team. His diverse background in engineering design, applications engineering and marketing enables him to craft insightful technical publications aimed at helping design engineers tackle complex challenges.

Ryan Jennings, Director of SATCOM and Systems Engineering

Ryan oversees the SATCOM technology roadmap, new product development and customer support. He has over 25 years of experience in mission-critical technology for commercial, intelligence, and defense sectors. Ryan holds a B.S. in electrical engineering from the University of Kentucky, an MBA from Regis University, and several phased-array related patents.