Low-Profile High-Power Microwave Termination With High Heat Dissipation Efficiency

In this letter, a novel high-power, low-profile microwave termination (matched load) using water as a lossy material is proposed. The electromagnetic wave (EM wave) first transitions from a rectangular waveguide (RWG) to a low-profile substrate-integrated waveguide (SIW) and then further transitions to a water medium. Utilizing the high lossy property of water for high-frequency EM waves, the EM wave energy is effectively converted into heat. Through the water circulation thermal design, the heat can be effectively released. The design combines the advantages of the SIW structure with low profile characteristics while maintaining high power capacity. It also offers benefits, such as low cost, compact structure ( $2.11\lambda _{0} \times 1.17\lambda _{0} \times 0.09\lambda _{0}$ ), simple fabrication, and ease of assembly. Measurement results show that, within the frequency range of 7.85–9.58 GHz, the return loss is better than 20 dB, with a relative bandwidth of 20%.