DDFS design using the equi-section division method for SDR transceiver

In this paper, the equi-section division method utilizing the symmetry property and amplitude approximation of a sinusoidal waveform to design a direct digital frequency synthesizer (DDFS) is proposed. Here, the sinusoidal phase of a one-quarter period is divided into equi-sections. The error value between each line segment value and the sinusoidal amplitude value is saved in a ROM to reconstruct the real sinusoidal waveform. As a result, the total compression ratio of the DDFS using the equi-section division method is superior to that of the DDFS using the basic look up table (LUT). The simulation and experimental results show that the proposed method can compress the size of the ROM effectively without affecting the spectrum performance. Therefore, the new ROM compression method can be used to generate a sinusoidal waveform, and then be applied to the software defined radio (SDR) system to complete the modulation, demodulation, upconversion, and downconversion.