研究目的
To design a low-cost microstrip directional coupler with high coupling for use in a Doppler motion detection sensor in the X frequency band, achieving stronger coupling and higher isolation compared to standard couplers using low-cost materials and technology.
研究成果
The proposed directional coupler achieves a coupling factor increase of about 3 dB over standard couplers with the same inter-line spacing, meeting the design specifications (C ≥ -7 dB) in the 10-11 GHz band. It offers strong coupling and high isolation, making it suitable for Doppler motion detection sensors. Future work could focus on further optimizing size and loss efficiency.
研究不足
The coupler size increases compared to standard couplers, leading to slightly higher losses (average loss efficiency of 84% vs. 88% for standard coupler). The design is specific to the X frequency band and low-cost materials, which may limit applicability to other frequency ranges or higher-performance requirements.
1：Experimental Design and Method Selection:
The design utilized an asymmetric cascade connection of two coupled line sections based on a simplified circuital model. Optimization was performed using Ansys HFSS software to compensate for losses and second-order effects.
2：Sample Selection and Data Sources:
A prototype was fabricated using a low-cost organic-ceramic laminate with specific dielectric properties (εr = 3.5, tan(δ) = 0.003), copper thickness of 35 μm, and minimum inter-line spacing of 0.15 mm.
3：5, tan(δ) = 003), copper thickness of 35 μm, and minimum inter-line spacing of 15 mm.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Materials included the laminate, copper for PCB fabrication, and SMA PCB connectors. Equipment included simulation software (Ansys HFSS) and measurement tools for frequency response analysis.
4：Experimental Procedures and Operational Workflow:
The coupler was designed with specific geometric parameters (e.g., W = 1.4 mm, S = 0.15 mm, electrical lengths optimized). A prototype was fabricated, and its performance was measured and compared to simulations and a standard coupler.
5：4 mm, S = 15 mm, electrical lengths optimized). A prototype was fabricated, and its performance was measured and compared to simulations and a standard coupler.
Data Analysis Methods:
5. Data Analysis Methods: Data were analyzed by comparing simulated and measured scattering parameters (e.g., coupling factor C, directivity, loss efficiency η) over the 10-11 GHz bandwidth using HFSS simulations and experimental measurements.
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