| 摘要 |
PURPOSE: To obtain a direct digital synthesizer(DDS) which is satisfactory in the deviation decomposition of frequency modulation(FM) without necessitating a complicated, expensive or slow hardware. CONSTITUTION: An initial modulation multiplied value is selected to obtain the approximate value of desired deviation. Then a clock frequency is selected to refine an FM deviation frequency to make it a desired value in substance. A carrying phase value is calculated by properly using a DDS center frequency and frequency resolution and finally the carrying phase value can be modulated by a frequency modulated value through the use of the asymmetric characteristic of a DDS demodulation source. Consequently, both strong points, the control performance of fine resolution of a standard multiplier and the speed of a binary shifter 28, are provided by modulating a clock frequency. |
