Abstract
This work presents a 28-GHz Butler matrix based switched-beam antenna for fifth-generation (5G) wireless applications. It integrates a 1 × 4 microstrip antenna, a 4 × 4 Butler matrix, and a single-pole four-throw (SP4T) absorptive switch in a single planar printed circuit board and is housed in a metal enclosure. Co-integration of a packaged switch chip with the Butler matrix based switched-beam antenna greatly enhances the form factor and integration level of the entire system. A wideband two-section branch line coupler is employed to minimize the phase and magnitude errors and variations of the Butler matrix. The aluminum metal enclosure stabilizes the electrical performances, reduces the sidelobes, and improves the structural stability. The fabricated antenna with the metal enclosure assembled has a dimension of 37 × 50 × 6.2 mm3. With an RF input signal fed to the antenna’s input port through a single Ka-band connector, and the switching states chosen by 2-bit dc control voltages, the antenna successfully demonstrates four directional switched beams. The beam switching operations are verified through the over-the-air far-field measurements. The measured results show that the four beam steering directions are −43°, −17°, +10°, +34° with side lobe levels < −5.3 dB at 28 GHz. The antenna also shows reasonably wideband radiation patterns over 27–29 GHz band. The 10-dB impedance bandwidth is 25.4–27.6 GHz, while a slightly relaxed 8-dB bandwidth is 25.2–29.6 GHz. Compared to previous works, this four-directional switched-beam antenna successfully exhibits the advantages of high integration level and satisfactory performances for the 28-GHz 5G wireless applications.
Highlights
Published: 29 July 2021The millimeter-wave fifth-generation (5G) wireless communication demands high-gain directive antenna systems with a beam steering capability
This four-directional switched-beam antenna successfully exhibits the advantages of high integration level and satisfactory performances for the 28-GHz 5G wireless applications
Since this work is focused on the full integration of all the key building blocks such as the antenna elements, Butler matrix, switch, and metal enclosure, the previous works [19,20,21,22,23,24] that have demonstrated the similar integration level are chosen for comparison
Summary
The millimeter-wave (mm-wave) fifth-generation (5G) wireless communication demands high-gain directive antenna systems with a beam steering capability. Noting that a directional coupler is a key building component for the three matrices, Butler matrix requires a smaller number. Kim et al [20] were interesting because they successfully demonstrated a complete integration of switch, Butler matrix, and antenna array, but only in 1–2 GHz non-mm-wave band. Fully integrated switched-beam antenna systems in mm-wave band are not found much in literature It is because the integration design process is more complicated and relevant mm-wave switch parts are not readily available. Compared to the prior works, this work advances the integral design and fabrication technology by fully integrating the microstrip array antenna, Butler matrix, and packaged switch IC in a single planar PCB
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