In this Letter, a new design of dual-band patch filter is proposed with greatly improved bandwidth and miniaturised size based on one single modified circular patch resonator. In this design, a metallic via is introduced in the centre region of the patch to develop the modified resonant TM01 mode (TM′01 mode), while two types of slot perturbations are adopted to separate a pair of degenerate modes of TM11 (TM11A and TM11B) and control another pair of degenerate modes of TM21 (TM21A and TM21B), respectively. Thus, two passbands with one transmission zero (TZ) can be attained by elaborately exploring these resonant modes (the TM′01 and TM11A modes form up the lower passband while TM11B and TM11A modes constitute the upper passband, and TM21B mode is responsible for the TZ). For verification, one prototype is implemented. Results indicate that the novel dual-band filter (centred at 3.7 and 5.3 GHz) exhibits not only relative compact size (0.36 λ g × 0.36 λ g), but also much larger 3-dB fractional bandwidths (27 and 13%), nice return loss (better than 21 dB) and insertion loss (better than 1.0 dB), compared with other reported patch filters.

中文翻译：

---

基于单个圆形贴片谐振器的双频带滤波器，带宽大大提高，尺寸紧凑

在这封信中，提出了一种基于单个改进圆形贴片谐振器的双频带贴片滤波器的新设计，具有大大提高的带宽和小型化的尺寸。在该设计中，在贴片的中心区域引入金属通孔以形成改进的谐振 TM01 模式（TM'01 模式），同时采用两种类型的槽扰动来分离 TM11 的一对退化模式（TM11A 和TM11B) 并分别控制 TM21 的另一对退化模式（TM21A 和 TM21B）。因此，通过精心探索这些谐振模式，可以得到两个通带和一个传输零 (TZ)（TM'01 和 TM11A 模式构成下通带，而 TM11B 和 TM11A 模式构成上通带，TM21B 模式负责TZ)。为了验证，实现了一个原型。