Ultra-compact half-mode substrate integrated waveguide diplexer based on evanescent-mode technique

Abstract An ultra-compact diplexer using a half-mode substrate integrated waveguide (HMSIW) structure loaded by the miniaturized metamaterial unit cell is offered in this paper. The evanescent mode technique, the half-mode technique, and the meander technique have been employed, simultaneously to miniaturize the total dimension of the proposed diplexer. In the modified metamaterial unit cell, which is called the meander complementary split-ring resonator (MCSRR) unit cell, the meander slot line is etched inside the interior space of the ring instead of the conventional slot line in the traditional complementary split-ring resonator (CSRR) unit cell. Accordingly, the electrical size of the MCSRR unit cell is smaller than the conventional CSRR unit cell with the same physical size. By loading the introduced MCSRR unit cell on the HMSIW structure, a miniaturized diplexer has been designed and simulated. To verify the performance of the proposed component, the designed HMSIW-MCSRR diplexer has been fabricated and measured. A reasonable agreement between simulated and measured results has been achieved. The fractional 3-dB bandwidths of the up and down channels are 3.3 % and 2.8 % at 2.45 GHz and 3.55 GHz, respectively. The total size of the proposed diplexer is about 0.25 λ g × 0.08 λ g .