Phase Controlled Signal Source Development

The basic theories of DDS and PLL are introduced in this paper.Using the method hybrid frequency synthesis technology called "DDS+PLL",the merits of DDS such as super fine frequency resolution,high frequency accuracy can be in combination with the excellent character of narrow-band tracing filter merits of PLL.Thereby,pure spectrum character of the Phase-controlled signal source can be realized.By adopting the signal source controlled by MCU chip MSP430F2013,high performance DDS chip,labeled AD9959,is selected to generate the reference frequency, which frequency and phase can variable.The resolution of the reference frequency can reach to 0.12Hz.The PLL part transforms the output frequency of AD9959 to 8.75GHz for satisfying the requirement of the system with lower spurious and high output power using the PLL chip ADF4106 and active low-pass loop filter.The specific program of the phase-controlled signal source in 8.75GHz,the questions which must be paid much attention to in the system design and the design of DDS,PLL part are represented and analyzed in detail.Besides SPI,The hardware interface circuit of MCU and AD9959 is also introduced. At last,the Phase-controlled signal source based on the above program is developed.The required parameters can be satisfied after testing.The output frequency is 8.75GHz,the spurious is better than 50dBc,the phase noise is less than -80dBc/Hz@ 10KHz.