Research Of Direct Digital Frequency Synthesizer Base On Phase Locked Loop

This paper designs a high-precision programmable phase shift signal generator using direct digital frequency synthesis (DDS) theory, the output high frequency stability, high resolution. NC adjust the phase shift, the smallest venue and into the phase 1, phase shift range:0 359 degrees; frequency numerical adjustment, the minimum frequency step is 1HZ; output frequency:1HZ ~ 50KHZ; produce sine, square and triangle wave three waveforms. In recent years, DDS technology has come a long way, especially AD985X series of large-scale introduction of ASIC, band constantly broadening, and constantly improve the performance, function continuously improved, indicators continue to optimize the application of DDS technology and DDS both onto a new level To achieve the strict sense of the phase shift, phase shift CNC adjustment phase into the venue and other technical problems to be solved first of ail strict 2-waysynchronization signals, apparently AD9851 is difficult to competent, multi-channel signal and the phase problem of strictly almost all synchronous not be achieved. Therefore required to open up a shortcut, do this, put forward the "lock-DDS technology" program. This article describes the phase-locked loop PLL circuit design and application, including working principle and PLL circuits, PLL circuit transmission characteristics, PLL loop filter circuit design, PLL frequency of DDS technology and features to improve the synthesis. Get a very accurate signal generator programmable phase shift.