What is Beamforming?

Beamforming is the process of forming and directing an electromagnetic beam ― as a wireless signal ― to create spatial diversity for an antenna. Beamforming revolves around creating and controlling a beam in an antenna-receiver system and directing the energy to receivers in a specific direction while preventing energy from going elsewhere.

Without beamforming, electromagnetic signals, such as radiofrequency waves, would spread out in all directions from the transmitter without any degree of control. This leads to less accuracy and a low signal-to-noise ratio at the intended receiver.

Beamforming is closely related to beam steering. While the two terms are often used interchangeably, beamforming forms a pencil-like beam and pushes the beam in a given direction, whereas beam steering continually updates the beam characteristics to follow a receiving device and respond to environmental changes.

Beamforming controls the phase and amplitude of multiple signal sources across an antenna array to create a single concentrated beam or multiple simultaneous beams.

The phase and amplitude are applied at the level of each signal stream, which could be at the individual antenna or at the point where multiple antennas combine to form subarrays.

To direct the beams, the signals radiating from the independent signal sources (antennas) are set to super-impose their radiated energy in a desired direction, which also creates nulls in other directions. Nulls develop in directions where very little energy is radiated and represent directions where receiving arrays have nearly zero sensitivity.

There are three main elements to constructing and directing a beam:

• Spatial signal processing: Analyzes the spatial characteristics and relative phases of an initial signal.
• Adapting the signal: Dynamically adjusts the gain and phase of each antenna based on the initial analysis.
• Signal combining: The signals from each antenna element are combined to create a focused beam that is directed toward the receiver. Interference in other directions can also be nulled at this stage.

Because transmitters and receivers work together, the receivers also play a role in how and when the signals are received. The receivers can be used to control the sensitivity pattern of the antenna system by delaying the individual signals that arrive at each antenna in the array. Controlling the time delay of the signal is the same as controlling its phase because the phase in the frequency domain is analogous to time delay in the time domain. Controlling the time delay/phase allows the wavefronts to be changed to a desired direction and to maximize their combination.

Alongside these, manipulating the amplitude of the received signal allows each antenna element to be controlled (to be strong or weak) to get the maximum signal possible in the directions of interest by suppressing the array pattern sidelobes to reduce energy delivered to unintended directions. This improves the signal strength and signal quality in the desired direction while reducing the signal in directions that are not of interest. This reduces the chance of an array interfering with other RF systems in transmit mode and reduces its sensitivity to other potential interference sources at different directions than the intended signal source. This is very important in big phased array setups with a large number of antennas, where multiple beams are used to track and handle multiple wireless users and communication systems.

Many beamforming techniques are used to generate, control, and direct a focused beam of energy.

Narrowband Beamforming

Narrowband beamforming is one of the simpler technologies. It uses a very specific, single frequency that provides a well-defined beam that is assumed to be the same across all antenna elements at the central frequency. It is commonly used in sonar technology and narrowband communication systems.

Wideband Beamforming

Wideband beamforming is more difficult to control, as the frequency is over a much wider band, in which a single-phase shift value would effectively blur the signal beam. The signal into the antenna needs to be adjusted for its bandwidth through changing the phase or frequency. If there are no adjustments, this can impact the effective spacing of the elements in a phased array and lead to beam squint (a phenomenon that can cause the beam to unintentionally change directions). If the bandwidth can’t be controlled on the transmitter end, a wideband signal is sent out (while aiming for the central frequency), and the downstream signal processing on the receiver end needs to compensate for the wide frequency bands. Wideband beamforming is commonly used in radar systems and MU-MIMO beamforming communication systems.

Zero Forcing Beamforming

Zero forcing beamforming revolves around null steering ― which nulls other signals to reduce interference. The null location is applied as a constraint to the beamforming conditions used to develop the appropriate beamforming channel phases, and that produces a composite signal cancellation for the null direction when the signals are combined. The null is combined into all the phase conditions applied to each element in the array. It’s commonly used to stop people from jamming global positioning signals, especially in the military and defense sectors.

Adaptive Beamforming

Adaptive beamforming enhances the transmission of a signal by dynamically adjusting the directional pattern of the phased array. It minimizes noise and maximizes the signal of interest. This beamforming technology is widely used in 5G networks. In communications that use adaptive beamforming, a standard signal is agreed upon and pilot signals are sent at regular intervals (such as every millisecond) across a wideband frequency while the receivers estimate what the channel looks like across the band.

Hybrid Beamforming

Hybrid beamforming is a combination of analog beamforming and digital beamforming. Hybrid beamforming uses both analog and digital components as part of a large array. It’s also largely used in 5G and millimeter wave (mmWave) communication systems where analog transmitters send a signal, but digital receivers process the received signal as a digital signal. Hybrid beamforming can reduce the digital processing complexity by applying analog beamforming to subarrays that "look" in constant but different locations and combine the signals to a smaller number of digital receivers. In this way, the system has a digital receiver concentrating on a specific spatial area. Hybrid beamforming methods can achieve high data rates at a lower cost and complexity than fully digital beamforming systems.

Even though beamforming is critical in many communication- and sensor-based applications, like any technology, there are advantages and disadvantages.

Benefits of Beamforming

• Provide high spatial control for directing the energy of a beam without wasting energy (i.e., energy that would be wasted in locations without a receiver).
• Enable multibeam control in phased arrays.
• Shape and direct wireless signals (radio frequency waves) precisely to enable high-speed and low-latency connectivity for different communication systems.
• Provide a way for transmitters to focus beams toward a wide range of devices, including the Internet of Things (IoT), mobile devices, and vehicles.
• Offer low detection and anti-jamming capabilities for military applications.
• Allow the frequency spectrum to be reused to form multiple beams.
• Provide resilience to individual transmitter or receiver failures with multisource array systems.

Limitations of Beamforming

• Complex systems require a lot of hardware components, including amplifiers, phase shifters, converters, and digital signal processing units.
• Beamforming technologies (particularly digital beamforming technologies) are not cheap, but the cost is coming down as hardware costs come down.
• Adaptability constraints can be problematic in changing environments.
• Advanced beamforming algorithms in digital beamforming can be computationally expensive.
• Beam squinting and self-nulling can occur during operation.

With different types of beams used today ― from light to radiofrequency and other electromagnetic waves ― there are many industries and applications where beamforming can be used.

Medical Applications

The beamforming used with magnetic resonance imaging (MRI) creates images with higher clarity due to reduced noise. In an MRI, individual transducers are located radially around the patient. The beamforming technology combines the signals from the transducers to generate a high-resolution image. By knowing the placement of all the transducers, the system can selectively interact with the imaging environment to determine which elements to include in the final image.

Aside from medical imaging, beamforming is used to treat patients with cancer. Many cancer treatments use beams of radiation (radiotherapy) that are created by phased arrays. These therapies can use multiple radiation sources in these arrays and have the particle beams converge at the tumor. This way, the narrow, focused beam can kill cancer cells while leaving the surrounding healthy cells untouched.

5G and NextG

Beamforming is used in 5G communications to focus radiofrequency waves between a base station and a mobile device. Across urban environments, there’s potential for echoes and noise due to signals bouncing off the ground and buildings, which impair the signals that the receiver must interpret. Beamforming helps focus those beams to the intended receiver regardless of the environment rather than the signals being broadcast in every direction. This also allows the frequency spectrum to be reused for multiple users and ensures high data rates and good network coverage for users.

Phased array antennas are integrated into many platforms and packages and can be used to maximize the energy directed in a specific direction. The animation above shows an HFSS software animation of dynamic beamsteering and also shows electric currents that the antenna induces onto other parts of the host package.

Optical Beamforming

Optical beamforming is used in multiplexers, where beams are formed in specific directions to undergo signal transfer and switch into a number of directions at high data rates. It’s also being used in satellite-to-ground optical communications, where the very precise control of optical beams is transmitted from a low-Earth-orbit satellite to a base station on the ground.

Phased array antennas are used increasingly in satellite communications and radar applications to reduce the need for mechanical steering while providing antenna system agility. This HFSS software simulation animation shows the radiation pattern that includes electromagnetic interaction with the host satellite vehicle.

Radar

In radar applications, beamforming focuses on a moving target and adapts/adjusts to any changes using the different antennas in an antenna array. Radar can often predict where the target will be, so the beam can be changed to different points to keep the energy on the target. Algorithms and feedback loops track the target itself using historical data on the target's likely trajectory.

Antenna beamsteering can be applied in practical applications to update the direction of signal gain to compensate for host vehicle motion. This HFSS software animation illustrates electromagnetic coupling to the antenna’s beamforming, as well as vehicle motion compensation capability.

In an ideal world, engineers would do as little physical testing as possible before the final product is realized. Simulation can help reduce the physical iteration development cycles needed by virtually simulating the antennas and the operational environment they will be used in. This allows antennas to be designed so precisely that you should have to build only one prototype ― saving time and money on failed prototypes. It also answers more questions about the design than is possible with physical testing alone.

Simulation can help to:

• Test the antenna design against the intended process technology.
• Test the potential manufacturing errors.
• Analyze how the antennas perform in real-world scenarios, including extreme environments (such as Death Valley or in space) and application scenarios (e.g., mounting the antenna on a military airplane to monitor its performance or in a city to test the coverage of wireless networks at different locations).
• Test the physics and properties of the fundamental materials under different conditions.
• Test the antenna system for graceful performance degradation in the event of individual channel failure. This helps strategize and schedule repairs to minimize impact on operational systems.

A number of Ansys tools can be used to answer these questions:

• Ansys HFSS high-frequency electromagnetic simulation software: Used to design high-frequency technologies at the device and integration level and phased arrays where all the required weights are calculated to focus a beam in a particular direction.
• Ansys Icepak electronics cooling simulation software: Designed to measure the heat convection around antenna systems and develop cooling systems for the application.
• Ansys Fluent fluid simulation software: Used to model fluid-, air-, and water-cooled systems to enable optimal operation and prevent transistors and chips from burning out.
• Ansys RF Channel Modeler high-fidelity wireless channel modeling software: Designed to combine antenna system digital twins with large-scale environment digital twins to look at how RF arrays function in real-world scenarios.

While beamforming technology today is enabling a lot of antenna systems to perform at a much higher level, advancements in digital beamforming are spearheading the next generation of communications technology.

This is because the signal is being sent to a digital format as quickly as possible, and then high-speed digital processors create multiple beams to search any desired direction. With enough baseband processing, the phase and amplitude can be applied to all users so they each have their own unique beam.

While 5G is currently benefiting from beamforming, digital beamforming will help to bring in 6G technology, more advanced radar systems, multiple-user multiple-input multiple-output (mu-MIMO) beamforming, and holographic beamforming.

If you’d like to find out how you can design more advanced antenna arrays and communication systems using different beamforming approaches, get in touch with our technical team today.

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