Design of Low Phase Noise X-Band Sweeping Frequency Source Based on DDS and PLL
Yueju Fu, Renjun Kuang, Bian Wu · 2024
This paper presents a low phase noise X-band sweeping frequency source using direct digital frequency synthesizer (DDS) to excite phase locked loop (PLL). In the scheme, DDS is used to output broadband and high-resolution sweeping signal as the reference signal of the post-stage PLL, then the loop frequency division ratio of the PLL is fixed, and finally, the X band sweeping signal is output. X band sweeping frequency source hardware PCB circuit structure adopts the idea of modular cavity design, simplifying the complexity of circuit design and reducing the interference between each module circuit. At the same time, an analog-to-digital independent LDO circuit was designed to address the external noise interference introduced by the power supply. The measure results show that the phase noise of the signal in the output frequency band of the DDS link is better than − 111.48dBc/Hz@lkHz, −118.36dBc/Hz@10kHz, the stray suppression is better than 60.2dBc, and the output power is flat in the band. It also highlights the advantage of cost-effectiveness.