Design of a Narrowband Energy Selective Protective Antenna Integrating Electromagnetic Protection and Anti-interference Capabilities
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摘要: 基于同轴馈电的微带贴片天线结构,该文设计了一种防抗一体化功能的窄带能量选择防护天线。防抗一体化,指的是防护和抗干扰功能的一体化设计。所设计的天线可有效抑制带外干扰,同时在带内具备电磁防护能力,低场强的电磁波入射时,天线正常工作,电磁波被天线接收; 高场强的电磁波入射时,天线自适应切换为防护模式,电磁波无法被天线接收。首先,采用特征模分析法对微带贴片天线辐射单元的潜在工作模式进行分析,结合电场和磁场模式分布研究其阻抗匹配特性,从而确定同轴馈电点的最优位置。随后,通过调控介质基板的介电常数,使天线具备窄带工作特性以及优异的带外干扰抑制能力,带外干扰抑制能力可达22。1 dB以上。进一步采用介质基板上下分层与中心镂空的设计方法,围绕同轴馈电探针构建空腔结构,并集成电磁防护功能模块,结合等效电路法阐释所设计天线的工作原理。当低能电磁波入射时,二极管处于断开状态,天线维持正常工作。当高能电磁波入射时,二极管导通,天线切换至防护状态。最后,完成天线的实物制备与实验测试,实测结果表明该天线具备尺寸小、窄带工作特性以及优异的电磁防护能力,防护效能最高可达26 dB。该研究实现了能域电磁防护和频域带外抗干扰的防抗一体化设计,展现出尺寸紧凑、频带窄、防护效能高的综合优势。Abstract:
Objective With the rapid advancement of wireless communication technologies, the electromagnetic (EM) environment has become increasingly complex. Electronic information equipment is facing growing challenges from high-intensity radiation fields (HIRFs) and out-of-band interference, making the co-design of EM protection and out-of-band interference suppression for electronic information systems a critical and urgent issue. As the front-end of the radio frequency channel, antennas serve as the primary pathway for converting EM waves in free space into guided waves within microwave circuits. High-power EM waves can couple into the system through antennas, causing EM damage. Moreover, in single-frequency application scenarios, if the antenna lacks narrowband characteristics, out-of-band interference signals may also enter the system via the antenna, disrupting normal operation. Therefore, it is essential to design a narrowband energy-selective protective antenna that simultaneously achieves out-of-band interference suppression and in-band protection against strong EM threats, thereby enhancing the operational stability and environmental adaptability of electronic information equipment in complex EM environments. Methods This paper focuses on the design of a coaxial-fed microstrip patch antenna, carrying out structural design and simulation optimization based on this antenna type. In accordance with the design requirements for the specific operating frequency of 915 MHz, the antenna structure itself is endowed with both narrowband characteristics and EM protection capabilities, thereby achieving an integrated design of EM protection and anti-interference. A high dielectric constant contributes simultaneously to antenna miniaturization and narrowband operation. Therefore, a TP-2 substrate with a dielectric constant of 20 is selected in this work to achieve the desired narrowband performance. In traditional coaxial-fed microstrip patch antennas, the probe structure passes directly through the dielectric substrate and connects to the radiating patch, leaving insufficient space for integrating protective structures. To address this limitation, a design approach featuring a layered substrate with a central hollow cavity is adopted, constructing a layered-cavity protective structure that enables the antenna itself to possess energy-selective protection characteristics. Results and Discussions To verify the performance of the proposed antenna, this study carried out physical fabrication and experimental measurement ( Fig. 14 ). The measured center frequency of the antenna is 928.5 MHz, with an operating bandwidth from 927.0 MHz to 930.0 MHz. Although the measured center frequency exhibits a shift of 12.8 MHz compared to the simulated design value, the antenna still demonstrates favorable narrowband characteristics (Fig. 15 ). The measured radiation pattern agrees well with simulated results. In the Phi = 0 deg plane, the antenna exhibits stable omnidirectional radiation characteristics, with a measured maximum gain of 2.5 dBi (Figs. 11 ,16 ). The shielding effectiveness (SE) of the antenna was measured using a high-power injection test method. As the injected power increased, the radiated power grew linearly. When the injected power reached 22 dBm, the growth trend of the radiated power saturated, indicating that the diodes in the protection structure began to conduct and the energy-selection mechanism was activated. Upon further increasing the injected power, the SE gradually rose. When the injected power reached 48 dBm, the radiated power surged to the level corresponding to the original linear radiated power, and the SE dropped sharply, indicating that the diodes had broken down and the protection structure failed. In summary, the activation threshold of the antenna’s protection function is 26 dBm, and the device damage threshold is 48 dBm. Within this range, a maximum SE of 26 dB is achieved (Fig. 18 ).Conclusions Based on the structure of a coaxial-fed microstrip patch antenna, this paper designs and implements a narrowband energy-selective protective antenna with an integrated EM protection and anti-interference capabilities. The study covers the complete research process, from theoretical analysis and structural simulation optimization to physical fabrication and experimental verification. Firstly, the characteristic mode analysis (CMA) method was employed to qualitatively investigate the potential operating modes of the microstrip patch antenna. By analyzing the electric and magnetic field modal distributions, the impedance matching characteristics were examined, and the optimal position for the coaxial feed point was determined accordingly. Subsequently, the use of a high-permittivity substrate enabled both antenna miniaturization and narrowband performance, achieving an interference suppression capability (ISC) of better than 22.1 dB. Furthermore, a structural design featuring a layered substrate with a central hollow cavity was proposed, creating a cavity-based protective structure integrated into the feed probe region. An equivalent circuit model was also established to thoroughly explain the operational mechanisms of the antenna under normal and protective states. Finally, the antenna prototype was fabricated and its performance was measured. Measured results demonstrate that the antenna exhibits favorable narrowband characteristics, and its radiation pattern aligns well with simulated results, with a measured maximum gain of 2.5 dBi. Moreover, applying the reciprocity principle and using a high-power injection method for SE testing, a maximum SE of 26 dB was recorded, confirming its excellent EM protection capability. Compared with existing protective antennas, the proposed structure simultaneously achieves out-of-band interference suppression and EM protection within the antenna's own architecture, effectively advancing the integrated design of “frequency-domain interference suppression and energy-domain protection.” It should be noted that factors such as non-uniform dielectric constant of the substrate and fabrication tolerances led to a certain deviation between the measured and simulated center frequency, which reflects to some extent the sensitivity of narrowband antennas to structural parameters. In future research, the introduction of a tunable mechanism could be explored to develop a frequency-reconfigurable narrowband energy-selective protective antenna, thereby dynamically compensating for frequency deviations and enhancing design robustness and environmental adaptability. -
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