A D-band waveguide diplexer, implemented by silicon micromachining using releasable filling structure (RFS) technique to obtain high-precision geometries, is presented here for the first time. Prototype devices using this RFS technique are compared with devices using the conventional microfabrication process. The RFS technique allows etching large waveguide structures with nearly 90° sidewall angles for the 400- $\mu \text{m}$ -tall waveguides. The diplexer consists of two direct-coupled cavity six-pole bandpass filters, with the lower and the upper band at 130–134 and 141–148.5 GHz, respectively. The measured insertion loss of the two bands is 1.2 and 0.8 dB, respectively, and the measured return loss is 20 and 18 dB, respectively, across 85% of the passbands. The worst case adjacent channel rejection is better than 59 dB. The unloaded quality factors of a single cavity resonator are estimated from the measurements to reach 1400. Furthermore, for the RFS-based micromachined diplexer, an excellent agreement between measured and simulated data was observed, with a center frequency shift of only 0.8% and a bandwidth deviation of only 8%. In contrast to that, for the conventionally micromachined diplexer of this high complexity, the filter poles are not well controllable, resulting in a large center frequency shift of 3.5%, a huge bandwidth expanding of over 60%, a poor return loss of 6 and 10 dB for the lower and the upper band, respectively, and an adjacent channel rejection of only 22 dB.

中文翻译：

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使用可释放填充结构技术的硅微加工 D 波段双工器

此处首次介绍了 D 波段波导双工器，该双工器通过使用可释放填充结构 (RFS) 技术的硅微加工获得高精度几何形状。使用这种 RFS 技术的原型设备与使用传统微制造工艺的设备进行了比较。RFS 技术允许蚀刻具有近 90° 侧壁角的大波导结构，用于 400-$\mu\text{m}$ -tall 高波导。双工器由两个直接耦合的腔体六极带通滤波器组成，下频带和上频带分别为 130–134 和 141–148.5 GHz。测得的两个频段的插入损耗分别为 1.2 和 0.8 dB，在 85% 的通带上测得的回波损耗分别为 20 和 18 dB。最坏情况下相邻信道抑制优于 59 dB。单腔谐振器的空载品质因数估计达到 1400。此外，对于基于 RFS 的微机械双工器，观察到测量和模拟数据之间的极好一致性，中心频移仅为 0.8% 和带宽偏差仅为8%。相比之下，这种高复杂度的传统微机械双工器，滤波器极点可控性不好，导致中心频移大3.5%，带宽扩展超过60%，回波损耗差6和低频段和高频段分别为 10 dB，相邻信道抑制仅为 22 dB。观察到测量数据和模拟数据之间非常吻合，中心频移仅为 0.8%，带宽偏差仅为 8%。相比之下，这种高复杂度的传统微机械双工器，滤波器极点可控性不好，导致中心频移大3.5%，带宽扩展超过60%，回波损耗差6和低频段和高频段分别为 10 dB，相邻信道抑制仅为 22 dB。观察到测量数据和模拟数据之间非常吻合，中心频移仅为 0.8%，带宽偏差仅为 8%。相比之下，这种高复杂度的传统微机械双工器，滤波器极点可控性不好，导致中心频移大3.5%，带宽扩展超过60%，回波损耗差6和低频段和高频段分别为 10 dB，相邻信道抑制仅为 22 dB。