Abstract:      The terahertz space detection system is rapidly developing towards multi-channel, multi-band, and ultra-wideband capabilities. Therefore, a WR-4 band full-band diplexer based on the waveguide hybrid network is proposed for combined-channel pumping of local oscillator signals in dual-band solid-state systems. The diplexer utilizes the anti-reflection and high isolation coupling characteristics of the hybrid network, combined with the cascaded implementation of a high-order low-pass filter. The overall structure is robust and easy to fabricate and integrate using CNC. It mainly includes the principle design of the WR-4 full-band coverage hybrid network diplexer, discrete element device mixer, filter circuit design, and circuit synthesis and optimization of the hybrid network diplexer and its E-plane split CNC milling process. The measured performance shows that the WR-4 band diplexer can achieve full band division with two channels of 170-210 GHz and 210-260 GHz. The channel interpolation loss is as low as -1.5 dB and -1 dB, with one channel's isolation as high as 50 dB. All test results are highly consistent with the simulation data. In addition, the solid-state diplexer circuit features easy structure fabrication, system integration, channel expansion, and frequency expansion.