UESTC researchers develop a new phased array antenna for millimeter-wave communications

Over the past few decades, the explosive proliferation of smartphones, Wi-Fi, and Internet-of-Things (IoT) devices has intensified the need for additional frequency resources. The traditionally used low and medium frequency bands are now congested, as new technologies compete for limited spectrum space below 6 GHz. Accordingly, engineers have begun exploring higher frequencies when designing wireless communication systems, such as the Ka-band (26.5–40 GHz) in 5G mobile communications.

However, while these millimeter-wave (mmW) frequencies hold great promise for high-speed wireless communications, their use is hindered by significant technical challenges. These include high propagation losses, atmospheric absorption, and scattering and obstruction by non-line-of-sight obstacles, all of which limit communication distances.

Fortunately, all these hurdles can be overcome through careful antenna design, as a research team from China demonstrated in a study recently published in the Journal of Electronic Science and Technology. Led by Professor Peng Yang of the University of Electronic Science and Technology of China (UESTC), the team presented a simple yet very effective phased array antenna design capable of wireless communication at 27 GHz. Their paper was made available online on August 17, 2024, and was published in Volume 22, Issue 3 of the journal on September 1, 2024.

A phased array antenna is a sophisticated system composed of multiple individual antenna elements that work together to direct electromagnetic waves in specific directions without any physically moving components. By adjusting the relative phases of the signals fed to each element, the array can steer its beam, focus it, or shape it to achieve the desired coverage. Phased array technology is a hallmark of state-of-the-art mobile communications like 5G, and cost-effective designs that can operate in the mmW range are highly sought after.

The research team’s design consists of a 2-bit 1×8 phased array, meaning that it can change the phase of the emitted signal at each of its eight elements in four discrete steps: 0°, 90°, 180°, and 270°. This phase-shifting capability is controlled through the states of four special diodes, which are carefully integrated into each element’s printed circuit, compensating for parasitic effects and electromagnetic interference that can degrade the transmitted waves.

In addition to careful design and simulations to predict important performance parameters, the team conducted an experimental verification of the proposed phased array antenna. To this end, they fabricated a sample circuit using standard manufacturing technology and tested its transmission capabilities in an anechoic (free from echo) chamber.

The results of the experiments highlighted the exceptional performance of this relatively simple design. The antenna ports exhibited a reflection coefficient of less than −15 dBm, indicating that only a very small portion of the input signal was reflected and most of the power was effectively transmitted, a crucial parameter for minimizing power loss and maximizing radiation efficiency.

Additionally, the antenna exhibited high stability and linearity when phase shifting across the operating bandwidth, indicating that the system performs consistently and predictably. “The results verify that the test prototype has good scanning performance,” remarks Prof. Yang. A stable phase response ensures that the antenna can accurately control the direction of the radiated signal, which is needed in virtually all mobile communication applications.

Another notable aspect of the proposed design is its small circuit footprint. “Antennas used in mobile communication terminal equipment generally need to meet criteria such as low profile, lightweight design, and fast beam switching,” explains Prof. Yang. “Our design fulfills these needs with an overall array outline size of 70 mm × 33 mm with a thickness of 0.81 mm in the experimental sample.”

Overall, this study offers a highly promising and practical solution for advancing mmWave communication technology. Experimental results show that the array achieves a peak gain of 10.23 dBi and is capable of beam scanning within ±50°, further validating the antenna's performance. By combining simplicity, efficiency, and compactness, the phased array antenna designed by the UESTC research team demonstrates how the challenges of high-frequency transmission can be overcome through careful design of the antenna structure with loaded electronic components.

Reference

DOI: https://doi.org/10.1016/j.jnlest.2024.100275