糖尿病已成為全球重大的公共衛生負擔，連續且準確的血糖監測對於預防急慢性併發症至關重要。現有臨床主流的侵入式量測方法易造成病患不適與感染風險，因此開發非侵入式檢測系統具有極高的臨床價值。微波感測技術因具備穿透力且不受膚色等光學因素干擾，成為極具發展潛力的非侵入式量測方案。
本研究旨在設計並分析一種共面波導（CPW）微波感測結構，探討其對不同濃度葡萄糖水溶液之電磁特徵響應。在數值模擬方法上，本研究應用現有文獻中之德拜模型（Debye model）來設定不同葡萄糖濃度的介電參數以模擬感測器之頻率響應，並結合有限差分時域法（FDTD）進行寬頻電磁場分析。為排除溶液於介電損耗峰值區間所引發之嚴重干擾，本研究建立了一套兩階段之特徵擷取流程：先於特定角頻率下定位出主模態之傳播常數，再以此傳播常數為基準擷取一維頻譜圖。透過此分析手法，客觀量化 0 mg/dL 至 16000 mg/dL 葡萄糖水溶液的色散與頻譜特徵。
模擬結果顯示，隨著葡萄糖濃度增加，整體有效介電常數之實部下降，但在主模態之低頻區段（ω≈0.3×10^11 rad/s），高濃度溶液之介電虛部則相對較高。此介電特性的改變使得微波傳輸相速度提升、共振波峰產生高頻偏移（藍移）；同時，增加的微波能量吸收與介電損耗導致了半高寬（FWHM）的展寬與整體能量耗散率（1/Q）的上升。經由線性迴歸分析證實，FWHM 與 1/Q 對應濃度之校正曲線的決定係數 R^2 分別高達 0.9995 與 0.9951。
本研究透過數值模擬與特徵擷取流程，初步驗證了共面波導結構對葡萄糖濃度變化的規律性響應。此具備高度線性之評估指標，不僅能解釋微波能量在不同濃度溶液中的耗散機制，亦可作為未來非侵入式生理微波感測系統在訊號特徵分析與濃度鑑別上之理論依據。

Diabetes mellitus has become a major global public health burden, and continuous, accurate blood glucose monitoring is crucial for preventing acute and chronic complications. The prevailing invasive measurement methods in clinical practice are prone to causing patient discomfort and risk of infection; thus, developing non-invasive detection systems holds immense clinical value. Microwave sensing technology, possessing good penetration capabilities and remaining unaffected by optical factors such as skin color, has emerged as a highly promising non-invasive measurement approach.
This study aims to design and analyze a coplanar waveguide (CPW) microwave sensing structure to investigate its electromagnetic characteristic responses to aqueous glucose solutions of varying concentrations. For the numerical simulation method, this study applies the Debye model from existing literature to set the dielectric parameters for different glucose concentrations to simulate the sensor's frequency response, combined with the finite-difference time-domain (FDTD) method for broadband electromagnetic field analysis. To eliminate severe interference caused by the solution within the dielectric loss peak interval, this study establishes a two-stage feature extraction process: first, locating the propagation constant of the dominant mode at a specific angular frequency, and then extracting the one-dimensional frequency spectrum based on this propagation constant. Through this analytical approach, the dispersion and spectral characteristics of aqueous glucose solutions ranging from 0 mg/dL to 16000 mg/dL are objectively quantified.
The simulation results indicate that as the glucose concentration increases, the real part of the overall effective permittivity decreases. However, in the low-frequency region of the primary mode (ω≈0.3×10^11 rad/s), the imaginary part of the permittivity for high-concentration solutions is relatively higher. These variations in dielectric properties lead to an increase in the microwave transmission phase velocity and a high-frequency shift (blue shift) of the resonance peak. Simultaneously, the enhanced microwave energy absorption and dielectric loss result in the broadening of the full-width at half-maximum (FWHM) and an increase in the overall energy dissipation rate (1/Q). Linear regression analysis confirms that the coefficients of determination (R^2) for the calibration curves of FWHM and 1/Q with respect to concentration are as high as 0.9995 and 0.9951, respectively.
Through numerical simulations and the feature extraction process, this study preliminarily verifies the regular response of the CPW structure to changes in glucose concentration. These highly linear evaluation indicators not only explain the dissipation mechanism of microwave energy in solutions of varying concentrations but can also serve as a theoretical basis for signal feature analysis and concentration identification in future non-invasive physiological microwave sensing systems.

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