基于宽边耦合带状线结构, 该文设计了一种基于低温共烧陶瓷(LTCC)技术的高隔离低插损3 dB 90°电桥。该电桥使用螺旋耦合线有效地减小了器件尺寸, 同时以对称式结构建模更便于后期的优化调整。在宽边螺旋耦合带状线垂直方向引入一个伸入式可调隔离电容, 极大地提高了该电桥的隔离度, 使其可达27 dB, 且插入损耗≤0.2 dB, 较之传统的定向耦合器结构, 其在提升性能的同时大幅减小了器件尺寸。对耦合线直角拐弯处的电场强度进行分析与优化, 采用45°斜切的方式使拐角处的电场强度与直线处大致相等。对上接地金属板进行环形镂空处理, 这将改善带内的幅度平衡度。该文设计的3 dB 90°电桥通带为0.96~1.53 GHz, 插入损耗≤0.2 dB, 幅度平衡度≤±0.7 dB, 相位平衡度为90°±1°, 隔离度≥27 dB, 其具有良好的应用市场。

Based on the wide-side coupled stripline structure, a 3 dB 90° bridge with high isolation and low insertion loss based on low-temperature co-fired ceramic (LTCC) technology is designed in this paper. The spiral coupling line is used to effectively reduce the size of the bridge, and the symmetrical structure modeling is more convenient for later optimization and adjustment. By introducing an extended adjustable isolation capacitor in the vertical directions of the wide-side spiral coupling stripline, the isolation of the bridge is greatly improved, making it up to 27 dB, and the insertion loss is less than or equal to 0.2 dB. Compared with the traditional directional coupler structure, this can greatly reduce the device size while improving the performance. The electric field intensity at the right-angle corner of the coupling line is analyzed and optimized, and the electric field intensity at the corner is roughly equal to that at the straight line by adopting the 45° oblique cutting method. At the same time, the upper grounding metal plate is hollowed out annularly, which improves the amplitude balance in the band. The designed 3 dB 90° bridge has passband of 0.96-1.53 GHz, insertion loss of ≤0.2 dB, amplitude balance of ≤±0.7 dB, phase balance of 90°±1°, and isolation of ≥27 dB, which has a good prospect application in market field.