改进的相位噪声公式与低相位噪声振荡器设计

Modified Leeson formula and low phase noise oscillator design

由Leeson公式出发,分别考虑了谐振器有载Q与无载Q的比值、放大器增益以及回路损耗对振荡器相位噪声性能的影响.得出对应的计算公式和优化参数,并设计出X波段高Q蓝宝石低相位噪声振荡器.蓝宝石谐振器的插损为7.9dB,谐振模式为E5,1,1+δ,有载Q值为4×104,无载Q值为9×104左右,放大器增益为12dB.采用R&S的FSUP相位噪声测试仪测出偏离载频1kHz处,相位噪声优于-117dBc/Hz,载频为10.99GHz.

Leeson formula is reviewed taking into account the ratio of the loaded Q to unloaded Q, the gain of the amplifier and the loss in the oscillator loop. Three modified Leeson formulae are proposed as well as the optimum parameters needed in the oscillator design. A sapphire X band oscillator is designed. The insert loss of the sapphire resonator is 7.9 dB, the whispering gallery mode is E5,1,1＋δ, the loaded Q is 4 × 10^4, the unloaded Q is 9 × 10^4, and the gain of the amplifier is 12 dB, The phase noise measurement-FSUP from R ＆ S shows that the phase noise level is better than -117 dBc/Hz at 1 kHz offset and the carrier frequency is 10. 99 GHz.