All-resonator based LTCC diplexer using substrate-integrated-waveguides

A compact diplexer is implemented in Low-Temperature-Cofired-Ceramic (LTCC) technology and consists of six coupled substrate-integrated-waveguide (SIW) cavity resonators stacked in two layers. No transmission-line based junction is used. The couplings between the cavities are achieved through both SIW irises and slots placed in metal layers. The diplexer has two third-order filtering channels, centred at 2.7 and 3.3 GHz with 120 MHz bandwidths. The overall size of the diplexer is 27.74 mm (2.3λg at 3 GHz) × 10.4 mm (0.86λg at 3 GHz) × 0.84 mm, achieved by using an LTCC material of a high dielectric constant of 68. Simulations and measurements are in good agreement to demonstrate a compact diplexer based on an all-resonator structure using high dielectric constant LTCC material.