Development of program controlled constant amplitude low frequency phase shifter

In order to simulate any phase-angle signal over a wide frequency range, this paper designs a DAC-based constant amplitude low-frequency phase shifter. The circuit mainly consists of three parts: a phase shift circuit with feedback, a vector attenuation circuit, and a vector synthesis circuit. The 90° phase shift is achieved by automatically adjusting the feedback-controlled variable resistance of the field-effect transistor through phase angle detection. This ensures high-precision phase shifting for different frequency occasions. The 12-bit high-precision multiplicative DAC chip is used to attain attenuation of the standard vector signal. The high stability of the DAC chip guarantees the accuracy of the target attenuation signal. To minimize errors in vector synthesis, the circuit employs highly matched network matching resistors and operational amplifiers. Experimental results demonstrate that the entire phase-shifting circuit can accomplish 360° phase shifting within the frequency range of 10Hz to 10kHz, with a phase-shifting accuracy better than ±0.1°