Recent advances in millimeter- and submillimeter-wave astronomy demand heterodyne receivers that simultaneously provide wide intermediate-frequency (IF) bandwidth and low receiver noise temperature. In this work, we present the design, fabrication, and experimental validation of a wide-IF (8–16 GHz) superconductor-insulator-superconductor (SIS) mixer for the 150 GHz band. The device employs a series array of four Nb/AlOx/Nb SIS junctions with a target RF embedding impedance near the optimum impedance of 31 Ω, and it is integrated with a pentagonal probe and a WR 6.5 waveguide for RF broadband coupling. Full-circuit simulations conducted in SuperMix were used to define the layout, and the performance of the fabricated mixer was evaluated in a 4 K test cryogenic receiver using hot/cold-load measurements over the 8–16 GHz IF band in double-sideband (DSB) mode. At a local oscillator (LO) frequency of 154 GHz, the mixer exhibits a maximum DSB conversion gain of 6 dB with a corresponding receiver noise temperature (Trx) ∼ 29 K. Across the IF band, Trx averages 43 K with a range of 25–76 K. These results establish the developed mixer as a promising candidate for next-generation wide-IF astronomical receivers.