Terahertz communication is one of the important development directions for wireless mobile communication in the 6G era, characterized by large bandwidth and low latency, suitable for various application scenarios such as high-speed wireless backhaul and satellite communication. This paper designs a D-band (110~170 GHz) wireless communication system based on intermediate frequency synthesis, achieving D-band broadband wireless communication with a total bandwidth of (n×2) GHz by synthesizing n intermediate frequencies with a bandwidth of 2 GHz each, thereby achieving a transmission rate of over 100 Gbps. To verify the feasibility of the system, a 1/n scale-down verification was conducted on the designed n-path communication system. The results show that using a 2 GHz D-band channel bandwidth, a maximum of 11.2 Gbps air interface transmission rate and 9.4 Gbps service transmission rate can be achieved with 128-QAM (Quadrature Amplitude Modulation), proving that the n-path intermediate frequency synthesis system architecture using only one set of D-band RF front ends can achieve low-cost D-band broadband high-speed wireless communication.