Abstract : Based on the coded phase-modulated pulse compression and interval transceiver system of a novel ionospheric oblique backscattering sounding system, a VXI bus-based signal source module suitable for this system was implemented using FPGA and a digital upconverter. The design method, main logic, and timing relationships of the module are described in detail. Experiments show that the module operates reliably, with flexible operating modes and parameter adjustments, and achieves RF signals and timing control signals that meet the system requirements, satisfying the anti-interference, openness, and easy upgrade requirements of the novel ionospheric oblique backscattering sounding system. Keywords : Ionospheric oblique backscattering sounding system; VXI bus; FPGA; digital upconverter; signal source 0 Introduction The novel ionospheric oblique backscattering sounding system (IOBSS) is an ionospheric Doppler radar based on pulse compression pseudo-random code phase modulation and interval transceiver system. The radar uses a VXI bus as the system bus to meet the design requirements of modularity, standardization, and flexibility. Designing a signal source module suitable for this ionospheric detection system is crucial for the radar's operation. The signal source module is required to generate radio frequency signals and system timing control signals that meet the requirements of the radar system, and be designed as a VXI bus module. Currently, the design of VXI interface circuits mainly includes the following approaches: First, using small- to medium-scale logic devices or simple gate array logic chips (such as GAL, PAL, etc.), which have low integration, high power consumption, and poor reliability; second, using dedicated interface chips, such as Interface Tech's IT9010/IT90IOM interface chips, which have good reliability but are expensive, have long lead times, and are complex in function, requiring many additional peripheral devices to achieve good integration with the module; third, using large-scale complex programmable logic devices (CPLDs) or field-programmable gate arrays (FPGAs) to design the VXI interface circuit, which is the best choice. It can improve interface reliability, shorten the development cycle, reduce power consumption, and has advantages such as high speed, low price, and the ability to be modified at any time to adapt to different application requirements. There are two main methods for generating radar operating waveforms: one is the traditional phase-locked loop (PLL) circuit; the other is direct digital synthesis (DDS) technology. Compared with PLL, DDS has advantages such as high frequency resolution, fast frequency change speed, linear phase change, and ease of digital control, and can flexibly realize rapid changes in radar operating waveforms. [b][align=center]For more details, please click: Design of Signal Source for Ionospheric Detection System Based on VXI Bus[/align][/b]