Abstract: In broadband digital receivers, the real-time processing of high-speed data streams places extremely demanding requirements on the performance of subsequent digital downconverters. Based on the polyphase filter structure, a method using multiple parallel multipliers is proposed, which greatly improves the input data stream rate and data bandwidth of the digital downconverter. Finally, simulation results are presented. Keywords : Digital downconverter; Polyphase filter; Signal processing 0 Introduction The bottleneck between the high-speed A/D required by broadband digital receiver systems and the processing capabilities of existing processors has long limited the development of real-time digitization in electronic reconnaissance, thus giving rise to research on digital downconversion technology. The digital downconverter serves as the link between the high-speed A/D converter and the subsequent digital signal processor (DSP). Therefore, the operating speed of the digital downconverter is limited by the processing speed of the DSP; simultaneously, its operating speed determines the maximum rate that the input data stream can reach, which correspondingly limits the maximum sampling rate of the ADC. Therefore, researching efficient digital downconverter structures is of great significance for broadband digital receiver systems. 1. General Structure of a Digital Down-Converter Digital down-conversion technology is the core technology of broadband digital receivers. Its main functions include three parts: First, frequency conversion, including a numerically controlled oscillator (NCO) and a digital mixer, down-converts the signal of interest to zero intermediate frequency. In broadband digital channels, the high-frequency NCO ensures the ability to extract a single carrier. Second, a low-pass filter (LPF) filters out out-of-band signals and extracts the signal of interest. Its programmable filter (FIR) can also be designed as a matched filter. Third, sampling rate conversion reduces the sampling rate to facilitate subsequent signal processing (D represents the decimator, which reduces the sampling rate of subsequent signals), as shown in Figure 1. [b][align=center]For more details, please click: Ultra-Wideband Digital Down-Converter[/align][/b]