Design of 40GHz Agile Frequency Synthesizer

The frequency synthesizer is a core module for achieving high-performance metrics in modern communication systems. It also finds extensive applications in equipment testing, satellite detection, and assisted driving. The primary research and development directions for frequency synthesizers are broader signal output frequency ranges, faster tuning speeds, larger power dynamic ranges, and higher spurious suppression capabilities. In response to these demands, this paper employs a structure combining DDS (Direct Digital Synthesis), PLL (Phase-Locked Loop), and frequency multipliers. By mixing the DDS and PLL signals externally, the high-speed frequency tuning capability of DDS ensures rapid tuning speed, while the frequency multipliers extend the system's frequency spectrum. Ultimately, the designed frequency synthesizer achieves an output frequency range from 1GHz to 40GHz, with output power levels covering +10dBm to -100dBm, providing a power dynamic range of 110dB. The spurious suppression exceeds 53dBc. At a carrier frequency of 10GHz, the system's phase noise at high power output is better than -95dBc/Hz@20kHz.