Substrate Integrated Waveguide Miniaturization Filter with Interdigital Complementary Split-ring Resonator

In this work, a size-miniaturized evanescent-mode half-mode substrate integrated waveguide (HMSIW) bandpass filter with the proposed interdigital complementary spilt-ring resonator (IDCSRR). The IDCSRR is mainly constituted by etching multiple interdigital slots on the inner metal cover of the CSRR, which can effectively enhance the product of the equivalent capacitance and inductance of the structure, and eventually achieves a much smaller resonant frequency. In such way, notable size reduction can be expected. To verify the proposed idea, a bandpass filter is desighed by utilizing the proposed IDCSRR into HMSIW section to generate evanescentmode resonant transmission. Numerical simulations results have shown that the center frequency of the proposed filter is 865 MHz, with a 1-dB bandwidth of 40 MHz, an insertion loss of 2.2 dB and a return loss over 15 dB. Moreover, as compared with the HMSIW filter with the conventional CSRR, the proposed IDCSRR-loaded HMSIW filter has exhibited a relative electrical size of 72%, which illustrates quite good potential for size miniaturization applications of substrate integrated circuits and components in radio frequency and microwave systems.