(14)
Figure 3(b) shows the susceptance of YL andYt. It can be concluded from (11) that there are two cases in which resonance occurs. The first circumstance is that the susceptance of YL equals to the negative value of the susceptance of Yt , that is whenBL =-Bt . As shown in Fig.3(b), three resonance points correspond to this case, and they aref1 , f3 andf4 respectively. Under the above resonance points, the value of the susceptance for YLcounteracts the susceptance for Yt . In the second case, the susceptance of YL equals to the susceptance of YT equals to zero, that is whenBL =Bt =0. As observed in Fig.3(b), resonance point f2 corresponds to this situation. Compared to the three resonant points in other absorbers, the proposed PIUWA has an extra resonance forBL =-Bt . It is because an impedance jump occurs when the shorter dipole and the conductor-backed vertical substrate goes through the cascaded transmission lineh2 . The impedance jump makesBL produce another negative point to cancel outBt and creates a new resonant point at the high frequency thus expanding the bandwidth of the PIUWA. As for the five resonance points of the dual polarization model in Fig.4, the addition of a resonance is due to the interaction of the two sets of resonant units on the two adjacent surfaces.
Finally, the polarization dependence and oblique incidence stability of the proposed PIUWA are investigated. The simulated PIUWA reflection coefficients at different incidence angles are shown in Fig.4. It can be seen from the figure that despite for some deteriorates at large angle incidence for the high frequencies above 20GHz, the proposed PIUWA shows a good angular stability under full-wave polarizations over an ultrawide absorption band within 45° while maintaining S11≤-10dB which means a good absorptance batter than 90%.
Conclusion: This paper introduces a novel methodology for designing an ultra-wideband circuit analog (CA) absorber. Utilizing this approach, we have designed a compact ultra-wideband absorber. The proposed PIUWA exhibits a broad absorption band ranging from 4 to 24.53GHz and maintains a small footprint of 0.10λL×0.10λL×0.11λL(where λL denotes the wavelength at the lowest absorption frequency). A prototype of the PIUWA was subsequently fabricated and tested. The experimental measurements effectively corroborated the simulated results of the designs, thereby validating our approach.
Acknowledgments: This work is supported by National Key Research and Development Program of China (No. 2020YFB1806405), National Natural Science Foundation of China (No. 12004258), Shanghai Science and Technology Innovation Action Plan (No. 21511101403) and Major Key Project of PCL (No. PCL2021A17).
Kun Xue, Yifeng Qin, Haoliang Sun and Shaohua Dong (Peng Cheng National Lab, Shenzhen, Guangdong, China ) E-mail: xuek@pcl.ac.cn, qinyf@pcl.ac.cn, sunhl@outlook.com,lightdong@yeah.net.
Hongyi Zhu (Shanghai Engineering Research Center for Broadband Technologies and Applications, Shanghai, China ) E-mail: zhuhy@pcl.ac.cn
Min Han (Academy of Military Sciences, Beijing, China ) E-mail: hanminchina@163.com.
Hongyi Zhu (Shanghai Engineering Research Center for Broadband Technologies and Applications, Shanghai, China ) E-mail: zhuhy@ pcl.ac.cn.
* Corresponding author: Min Han, Shaohua Dong