The nonreciprocal bandpass filter has been achieved by utilizing the nonreciprocity characteristics of the magnetostatic surface wave (MSSW) in planar ferrite slabs. In this article, the dispersion relation, impedance, and attenuation of MSSW between the pure and metallized ferrite slabs have been analyzed and compared. Theoretical analysis indicates that the ferrite slab metallized by a thin conductive layer would introduce significant attenuation on the metallized interface, which is MSSW propagating on the isolated direction, while MSSW on the other surface is barely affected. Therefore, nonreciprocal bandpass filter with enhanced isolation can be achieved with metallized ferrite slab. Simulated S-parameters show that a notch in the isolating direction can be obtained at the passing band of the transmitting direction. Experimental results show that the nonreciprocal filter with metallized yttrium iron garnet (YIG) slab (by depositing 100- $\mathbf {nm}$ copper film) exhibits more than 10-dB higher isolation than that with pure YIG slab, while the center frequency, insertion loss, and 3-dB bandwidth maintain almost the same. The center frequency of the filter with metallized YIG slab can be tuned from 7.26 to 8.38 GHz with insertion loss of less than 3 dB, and in-band isolation of more than 30 dB as the dc bias magnetic field is increased from 1.8 to 2.3 kOe. Besides, the nonreciprocal filter has ultra-wide out-band suppression since it utilizes the narrow frequency band of MSSW. The −10-dB out-band rejection exceeds 36 GHz in the upper band and 1 MHz in the lower band.

中文翻译：

---

使用金属化铁氧体增强隔离的非互易隔离带通滤波器

非互易带通滤波器是利用平面铁氧体平板中静磁表面波 (MSSW) 的非互易特性实现的。在本文中，分析和比较了纯铁氧体板和金属化铁氧体板之间 MSSW 的色散关系、阻抗和衰减。理论分析表明，薄导电层金属化的铁氧体平板会在金属化界面上引入显着衰减，这是 MSSW 在隔离方向上传播，而另一个表面上的 MSSW 几乎不受影响。因此，可以使用金属化铁氧体板实现具有增强隔离度的非互易带通滤波器。模拟的 S 参数表明，可以在传输方向的通带处获得隔离方向的陷波。实验结果表明，金属化钇铁石榴石 (YIG) 板（通过沉积 100-$\mathbf {nm}$ 铜膜）的非互易滤波器比纯 YIG 板的隔离度高 10-dB，而中心频率、插入损耗和 3-dB 带宽几乎保持不变。带有金属化 YIG 板的滤波器的中心频率可以从 7.26 GHz 调谐到 8.38 GHz，插入损耗小于 3 dB，并且随着直流偏置磁场从 1.8 kOe 增加到 2.3 kOe，带内隔离度超过 30 dB . 此外，非互易滤波器由于利用了 MSSW 的窄频带，因此具有超宽的带外抑制。−10-dB 带外抑制在高频段超过 36 GHz，在低频段超过 1 MHz。