In this paper, a design for a metamaterial loaded rectangular metal waveguide is investigated for applications in accelerators and as a coherent radiation sources. The loaded waveguide structure is designed to operate between 4 GHz and 6 GHz, with optimal operation at 5.47 GHz. The metallic waveguide structure is loaded with sheets of complementary split ring resonators (CSRRs), which act like narrow patterned waveguides, confining the transverse magnetic (TM) modes which gives rise to left handed behaviour. Numerical simulations of the resulting electromagnetic modes within the structure are reported and analytical calculations of the beam coupling parameters performed. A TM-like mode is identified at 5.47 GHz for a phase advance of 10◦ and through analytical analysis is shown to have an R/Q of 26.40 W and a shunt impedance of 43.76
kW and thus is suitable for applications in acceleration and Cherenkov based detectors.