Abstract : This paper presents a scheme for digital up-conversion of high-frequency ground wave radar based on the programmable up-converter AD9857. The scheme uses a DSP to process the digital baseband signal and control the AD9857 to complete the up-conversion, allowing real-time changes to the modulation scheme of the digital baseband signal and the radar's operating parameters. Experiments demonstrate that this design simplifies the radar architecture, enables programmability of radar operating parameters, and meets the needs of the next-generation high-frequency ground wave marine monitoring radar being developed by Wuhan University. Keywords : AD9857; digital up-conversion; high-frequency ground wave radar; DSP 0 Introduction Traditional analog radar receiving and transmitting systems cannot meet the requirements of real-time programmability and also have low technical specifications. To meet the further development of high-frequency radar, it is necessary to construct a high-frequency radar hardware platform based on software radio principles, maximizing the openness, digitalization, standardization, and programmability of this hardware platform. DSP and digital up-conversion and down-conversion technologies are key technologies for constructing a general-purpose hardware platform for high-frequency radar. The AD9857, a new high-performance orthogonal digital upconverter chip manufactured by Analog Devices, works by performing baseband signal modulation, interpolation, and D/A conversion in the digital domain, outputting a modulated analog signal to complete the digital upconversion and digital-to-analog conversion functions of the radar transmission channel. This paper designs a DSP-based digital upconversion scheme using the AD9857. This scheme generates digital baseband signals with different codes using the DSP and controls the AD9857. It features a simple structure, flexible control, conforms to the principles of software-defined radio, improves system integration and reliability, and can be well applied to general-purpose high-frequency radar hardware platforms. [b]1 System Principle 1.1 Design Scheme[/b] The radar system upconversion scheme is shown in Figure 1. The transmission uses a pseudo-random code phase modulation system with an intermediate frequency of 40.5MHz and a radar detection range of 5km. The pseudo-random code phase modulation and orthogonal decomposition are performed by a high-speed floating-point DSP, finally generating two digital baseband signals, t and Q. The upconverted signal is a narrowband signal that is filtered by a crystal filter, amplified in two stages, and then mixed to a 40.5MHz carrier frequency.