This paper presents a novel miniaturized metamaterial-enabled diplexer designed for Ka-band. We introduce a measurement methodology to characterize noncontiguous channels within a waveguide structure. The diplexer efficiently separates receive (17.3-20.2 GHz) and transmit (27-31 GHz) satellite communication channels utilizing an innovative design approach that integrates locally resonant metamaterials (LRMs) and an evanescent mode junction. This integration allows for high rejection and low loss in an ultra-small volume, effectively showcasing the diplexer's capabilities. The measurement techniques implemented for the proposed component employ various waveguide transitions to cover the whole frequency band (15-40 GHz) and de-embedding procedures for manual calibration of the device under test (DUT). We precisely measure the passband and stopband of both the receive and transmit channels and compare the results with simulations. The results show less than 0.7 dB insertion loss for this ultra-compact diplexer.