Balanced Dual-Channel Filter Based on Dual-Mode Dielectric Resonator

In this article, we present a balanced dual-channel filter based on dual-mode square dielectric resonator (DR) with a short end at the bottom. In this case, the resonator acquires a compact size, while it still retains a high unloaded quality factor. The electric fields of the modes are half cut like the shape of DR. According to the field distributions of the applied degenerate modes (half-TE
011
and half-TE
101
), the pair of feeding probes are placed on both sides of the DR to realize differential excitation. Compared with the single-end feeding scheme, the higher order mode adjacent to the two used modes disappears after differential feeding. This property is beneficial to alleviate the adverse effect of higher order mode on the stopband suppression of the filter. The two orthogonal modes of half-TE
011
and half-TE
101
provide the internal isolation between the two channels. Based on the above analysis, a balanced dual-channel dielectric filter is designed with the center frequency of 1.52GHz and 3dB fractional bandwidth (FBW) of 2.6% for both channels. Because the structure is completely symmetric, the Chebyshev filtering responses of the two outputs are the same, and the number of size variables is significantly reduced. The results exhibit that the balanced dual-channel filter has the features of low loss, small size and wider upper stopband suppression.