An Improved Method for High Speed DUC in Broadband Transmitters
Xinxing Zhou, Fei Wen, Ming Yan · 2023
In the modern broadband transmitters, the sampling rate of DAC is required to be higher and higher, the bandwidth of the transmitted signal, meanwhile, is required to be wider and wider. The traditional method of the digital up conversion (DUC) is unable to meet the demand for the broadband transmission because of the limitation of the clock frequency of the field programmable gate array (FPGA). For broadband transmission applications, an improved method of high speed DUC is proposed. The interpolation filtering and direct digital synthesis (DDS) are optimized. Firstly, the mathematical model of high speed DUC is derived, and the structure of the traditional DUC is improved. The efficient and flexible structures of the interpolation filtering and DDS are designed. Secondly, the calculation method of multichannel coefficients of the interpolation filter is given. The calculation method of multichannel phase parameters of parallel DDS is also given. The hardware implementation shows that the proposed method has correct function, and can be applied to engineering conveniently. The data rate of the digital signal at intermediate frequency (IF) output from the hardware can reach 960MSps. The proposed method can realize interpolations with different multiples, and can also generate high speed local oscillator signals with different rates. It can meet the requirements of transmitting wide band and high rate signals in the modern broadband transmitters.