Most applications that use waveguides are designed for a single frequency or single band of frequency, and thus the waveguide dimensions are chosen for single mode operation. In special cases where multiple frequencies across multiple bands are needed (i.e., probing the temporal response of decaying plasma using a cw source that is generated by a pulsed source), special techniques must be used in order to implement both sources into a single waveguide structure. This paper presents two types of couplers designed to implement x-band frequencies into an s-band system with a large coupling coefficient (< -10 dB) and small reflection coefficient (> -10 dB) at the design frequency of 11 GHz. Along with a discussion on the design procedure, a detailed description on the parameter optimization and initial values estimation is presented. The custom waveguide structures were tested utilizing an Agilent E8364B PNA network analyzer, and showed reasonable agreement with the simulated performance over the frequency range of interest.