ตัวสังเคราะห์ความถี่ดิจิตอลโดยตรงที่ใช้วงจรดัดรูปสามเหลี่ยมเป็นซายน์ / คณิตพงศ์ เพ็งวัน = Direct Digital Frequency Synthesizer using triangular to sine shapers / Kanitpong Pengwon
This research proposes direct digital frequency synthesizers using triangular to sine shapers. The proposed shapers are based on PMOS. Three digital-analog mixed methods are also proposed to increase the accuracy. A referent current generator is invented to provide a referent current for DAC and biasing the shapers. Due to the referent current, the effects of processed parameters, i.e. and, are removed from the synthesized signals of the DDFS. The shapers have two structures named single and dual shapers. The single shaper is actually a PMOS differential amplifier. In the DDFS that utilizes the single shaper, a DAC is used to generate a triangle whose value is corresponding to phase of. Then, the triangle is converted to sine by the shaper. Another structure, the dual shaper, is composed of a PMOS differential amplifier and PMOS squarer. In the same fashion, a DAC generates a triangle that is corresponding to. The two circuits convert the triangle into sine and cosine segments. Some current switches are employed to convey the segments for synthesizing full-period sine and cosine waveforms. The MOS square law is mainly used to design the circuits and MATLAB is also used to find optimal parameters for the circuits. The DDFS is synthesized using Level-49 MOS model and simulated by HSPICE. Due to the simulation results, the signal with SFDR of >50 dBc can be archieved. A DDFS prototype is also developed using FPGA and MOS-array. It can generate a signal with SFDR of > 40 dBc.
