A Ku-Band Circularly Polarized Leaky-Wave Antenna Loaded with Parasitic Slots

HUANG Zhiyuan; ZHANG Yunhua; ZHAO Xiaowen

doi:10.11999/JEIT250347

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HUANG Zhiyuan, ZHANG Yunhua, ZHAO Xiaowen. A Ku-Band Circularly Polarized Leaky-Wave Antenna Loaded with Parasitic Slots[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250347

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HUANG Zhiyuan, ZHANG Yunhua, ZHAO Xiaowen. A Ku-Band Circularly Polarized Leaky-Wave Antenna Loaded with Parasitic Slots[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250347

HUANG Zhiyuan, ZHANG Yunhua, ZHAO Xiaowen. A Ku-Band Circularly Polarized Leaky-Wave Antenna Loaded with Parasitic Slots[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250347

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A Ku-Band Circularly Polarized Leaky-Wave Antenna Loaded with Parasitic Slots

doi: 10.11999/JEIT250347 cstr: 32379.14.JEIT250347

1.
Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
2.
University of Chinese Academy of Sciences, Beijing 100049, China

Received Date: 2025-04-30
Rev Recd Date: 2025-09-01

Available Online: 2025-09-08

Abstract

Abstract

This paper proposes a Ku-band circularly polarized Leaky-Wave Antenna (LWA) based on a Substrate Integrated Waveguide (SIW). A parasitic slot, with the same configuration as the main radiation slot but reduced in size, is employed to address the open-stopband problem and enhance impedance matching. The radiation slot excites Circularly Polarized (CP) waves, while the parasitic slot simultaneously broadens the Axial Ratio (AR) bandwidth and suppresses the open-stopband effect. A prototype antenna is designed, fabricated, and measured. The results demonstrate that the antenna achieves a 32% 3-dB AR bandwidth from 12.6 GHz to 17.4 GHz, with CP beam scanning from −49° to +14°. The simulated and measured results are in good agreement. In addition, the realized gain remains stable across the operating band. Compared with existing works, the proposed design achieves the widest scanning range. Objective Compared with traditional phased array antennas, frequency-scanning antennas have extensive applications in both military and civilian fields owing to their advantages of low profile, low cost, and lightweight design. CP waves offer superior anti-interference performance compared with linearly polarized waves. As a representative frequency-scanning antenna, the LWA has attracted sustained global research interest. This study focuses on the investigation of a Ku-band Circularly Polarized Leaky-Wave Antenna (CP-LWA), with emphasis on wide-bandwidth and wide-scanning techniques, as well as methods for achieving circular polarization. The aim is to provide potential design concepts for next-generation mobile communication and radar system antennas. Methods The fan-shaped slot is modified based on previous work, and an additional size-reduced parasitic slot of the same shape as the main slot is introduced. The parasitic slots cancel the reflected waves generated by the main radiating slot, thereby suppressing the Open-Stop-Band (OSB) effect, and they also enlarge the effective radiating aperture, which improves radiation efficiency and impedance matching. By exploiting the metallic boundary of the conductors, the parasitic slots enhance CP performance and broaden the AR bandwidth. To validate the proposed design, an antenna consisting of 12 main slots and 11 parasitic slots is designed, simulated, and measured. Results and Discussions A prototype is designed, fabricated, and measured in a microwave anechoic chamber to validate the proposed antenna. Both simulated and measured S₁₁ values remain below −10 dB across the entire Ku-band. The measured S₁₁ is slightly higher in the low-frequency range (12–13 GHz) and slightly lower in the high-frequency range (16–18 GHz), while maintaining an overall consistent trend with the simulations, except for a frequency shift of approximately 0.2 GHz toward lower frequencies. For the AR bandwidth, the simulated and measured 3-dB AR bandwidths are 32.7% (12.8–17.8 GHz) and 32.0% (12.6–17.4 GHz), respectively. The realized gains are on average 0.6 dB lower than the simulated values across the AR bandwidth, likely due to measurement system errors and fabrication tolerances. The simulated and measured peak gains reach 14.26 dB and 13.65 dB, respectively, with maximum gain variations of 2.91 dB and 2.85 dB. The measured AR and gain results therefore show strong agreement with the simulations. The measured sidelobe level increases on average by approximately 0.85 dB. The simulated CP scanning range extends from −47° to +17°, while the measured range narrows slightly to −49° to +14°. The frequency shift of the LWA is analyzed, and based on the simulated effect of variations in ε_r on the scanning patterns, the shift toward lower frequencies is attributed to the actual dielectric constant of the substrate being smaller than the nominal value of 2.2 specified by the manufacturer. Conclusions This paper proposes a Ku-band CP-LWA based on a SIW. The antenna employs etched slots consisting of fan-shaped radiation slots and size-reduced parasitic slots. The radiation slots excite circular polarization due to their inherent geometric properties, while the parasitic slots suppress the CP effect and broaden the CP bandwidth. Measurements confirm that the proposed LWA achieves a wide 3-dB AR bandwidth of 12.6–17.4 GHz (32%) with a CP beam scanning range from −49° to +14°. Meanwhile, the antenna demonstrates stable gain performance across the entire AR bandwidth.
- Substrate Integrated Waveguide (SIW),
- Circular Polarization,
- Leaky-Wave Antenna,
- Beam Scanning

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References(19)

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