A miniaturized full-metal dual-band bandpass filter using a dual-mode circular spiral resonator (CSR) in a single metal cavity is proposed. Two spirals are combined together to form a dual-mode resonator, and the transmission zero (TZ) produced by the source–load coupling can separate the two modes and achieve the desired dual-band property. Then, a second-order dual-band filter is designed based on the dual-mode resonator, and each band can be individually synthesized, designed, and tuned to achieve the desired filtering performances. In addition, each band has TZs on both sides of the passband to achieve high selectivity. The size of the second-order dual-band filter is only $0.073\lambda _{0} \times 0.055\lambda _{0} \times 0.015\lambda _{0}$ calculated at the center frequency of the lower band. Finally, the filter is fabricated and measured, and a good agreement is achieved between the measurement and simulation.

中文翻译：

---

使用双模圆形螺旋谐振器的小型化全金属双带滤波器

提出了一种在单个金属腔中使用双模圆形螺旋谐振器 (CSR) 的小型化全金属双带带通滤波器。两个螺旋组合在一起形成双模谐振器，源-负载耦合产生的传输零 (TZ) 可以将两种模式分开并实现所需的双频带特性。然后，在双模谐振器的基础上设计了一个二阶双频带滤波器，每个频带都可以单独合成、设计和调谐，以达到所需的滤波性能。此外，每个频段的通带两侧都有 TZ，以实现高选择性。二阶双带滤波器的大小仅为 $0.073\lambda_{0}\times 0.055\lambda_{0}\times 0.015\lambda_{0}$ 在下频带的中心频率计算。最后，制作并测量滤波器，