- 學位論文
考慮有限封裝模組的射頻降敏分析
RF Desense Analysis Considering Finite-Size Substrate
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摘要
有鑒於射頻模組靈敏度大約落在-60 ~ -100 dBm，全波模擬難以求解準確且耗時，本研究利用互易定理估算雜訊源對天線端埠的耦合電壓，就正問題 ( Forward Problem )，則以張量矩陣計算惠更斯等效雜訊源之作用。進而分析在受害端惠更斯觀察盒上之切線電磁場，而減少全波電磁模擬器 Ansys HFSS 在耦合路徑上，因近場不連續與網格分割大小所產生之耦合電壓誤差。由於張量矩陣包含遠場效應，因此透過遠場平面波的特性，將張量矩陣更進一步簡化，而計算時間也大幅改善以應用在FCC (Federal Communications Commission, USA)中輻射干擾(Radiated Emission)測試之環境，在近場輻射干擾中，簡化公式可用於決定天線最佳的擺放位置及旋轉角度。對於一般手持裝置如智慧型手機，則利用自動化方式在HFSS中建立偶極矩以考慮有限基板下輻射場，以考量天線位於有限大電路板的影響，同時搭配互異定理估計耦合電壓。其中探討板子寬度、凹槽位置、天線放置位置（同側或不同側）及屏蔽罩開槽方向對於耦合電壓的影響。計算結果顯示，將天線擺在不同側時，其耦合電壓改善約3-15 dB不等;改變屏蔽罩開槽方向因極化關係可改善約15dB左右;板子凹槽會使得磁場變大，造成耦合電壓上升約5 dB;再者，距離天線越遠耦合電壓不一定越小，最大可相差約10 dB。
並列摘要
Due to the sensitivity of general RF module antennas, which ranges from approximately -60dBm to -100dBm, it is hard to accurately solve and time-consuming for full-wave simulation. Therefore, this study uses the reciprocity theorem and tensor matrix to estimate the coupling voltage from the noise source to the antenna port. By leveraging plane wave characteristics in the far field, tensor matrix is further simplified, significantly improving computational efficiency. This approach is applicable to FCC Radiated Emission testing environments and helps determine optimal antenna placement and orientation in near-field interference scenarios. For handheld devices such as smartphones, an automated approach in HFSS is used to establish dipole moments to consider radiation fields under finite substrates, while estimating the coupling voltage for antennas by reciprocity theorem. The study examines the effects of board width, notch position, antenna placement and shielding slot orientation on the coupling voltage. Placing the antenna on the opposite side results in an improvement of approximately 3-15 dB in coupling voltage, while changing the orientation of the shielding slot improve around 15 dB due to polarization effects. Notches in the board increase the magnetic field, raising coupling voltage by approximately 5 dB. On a finite substrate, greater distances from the antenna do not always result in lower coupling voltage, with differences potentially reaching up to 10 dB.
參考文獻
[1] A. C. Scogna, H. Shim, J. Yu, C.-Y. Oh, S. Cheon, and N. Oh, “RFI and receiver sensitivity analysis in mobile electronic devices,” Signal Integrity J., May 2018.
[2] Q. Huang, Y. Zhong, C. Hwang, J. Fan, J. Rajagopalan, D. Pai, C. Chen, and A. Gaikwad, “Desense prediction and mitigation from DDR noise source,” in Proc. IEEE Symp. EMC & SIPI, Long Beach, CA, USA, 30 July- 3 Aug., 2018.
[3] ANSYS HFSS Help 2023 from ANSYS Inc., [online] Available: http://www.ansys.com/.
[4] G. Ramsubbaraj, L. Cheng and K. Rao, "RF desense risk prediction using EM simulation," in Proc. IEEE Symp. EMC & SIPI, Grand Rapids, MI, USA, 2023, pp. 65-69.
[5] Q. Huang and J. Fan, “Machine learning based source reconstruction for RF desense,” IEEE Trans. Electromagn. Compat., vol. 60, no. 6, pp. 1640-1647, Dec. 2018.