Baluns with lumped parameters are compact and easily integrated, but they have limitations in terms of power handling and bandwidth. On the other hand, baluns with distributed parameters, such as coaxial baluns, are extensively utilized in the design of high-power irradiation antennas for differential feeding and impedance matching, owing to their wide bandwidth, low loss, and high power capacity. To address the engineering requirements of wideband high-power irradiation antennas in a specific experimental system, a coaxial balun with an impedance transformation ratio of 1∶2.25 loaded with a ferrite magnetic ring is designed and realised based on the coaxial balun design method with any non-integer impedance transformation ratio. Simulation and measurement results demonstrate that the balun operates within the frequency range of 0.01-1.30 GHz, with a phase imbalance within ±5° of 180° and an amplitude imbalance within ±1 dB. The insertion losses of both paths are below 1.5 dB. The electrical performance of the balun at 500 W power feed is simulated and analysed to verify its power capacity.