A high-selectivity waveguide bandpass filter with interference suppression by more than 120 dB in rejection band

The design of a 10th-order waveguide bandpass filter with an additional inductive cross-coupling between non-adjacent resonators has been proposed and studied. An inductive coupling is formed by a $U$-shaped conductor structure with grounded ends that is formed in the filter cover. This method of cross-coupling organization ensures not only the temperature stability of the characteristics, but also the manufacturability of the structure. The high selectivity of the device is achieved by both the attenuation poles located near the passband, as well as the level of suppression in the stopbands, exceeding 120 dB. The passband loss of the fabricated filter is $\sim$0.8 dB at its central frequency $f_0$ = 18.2 GHz and relative bandwidth $\Delta f/f_0$ = 1.5%. The small dimensions (135 $\times$ 30 $\times$ 10 mm) and the weight of about 200 g of the device, with simultaneously high electrical characteristics show the promise of its use, for example, in on-board and ground-based space communication systems