开放的ISM波段可变频压控振荡器

摘要

Based on two-port negative resistance theory, and with active device FET of low noise figure, high input impedance and varactor diode of great varactor range. A variable frequency, low phase noise ISM band VCO is designed phase-noise LC is adopted to implement oscillation, varactor diode to expand the tuning range, lossless reciprocity network to match input and output circuits, and microstrip band-pass filter to suppress harmonic. Simulation and optimization are done on VCO circuit composed of active circuit, resonant circuit, matching network and band-pass filter of NE3512S02 FET, and experiment indicates that when the input voltage is 0.9~10 V, the output frequency range 4.5~5.3 GHz with the circuit start-up time less than 20 ns and stable amplitude, and the sensitivity tuning is 88 MHz/V, while the phase-noise being less than-108.7 dBc/Hz at 1 MHz.%选取噪声系数低、输入阻抗高的有源器件FET 和大变容范围的变容二极管，依据双端口负阻原理设计的ISM 波段压控振荡器具有可变频、低相噪的特点。采用低噪声LC 振荡，变容二极管扩大调谐范围，无耗互易网络匹配输入、输出电路，微带带通滤波器抑制谐波。对NE3512S02型场效应管有源电路、谐振回路、匹配网络及带通滤波器构成的压控振荡器电路进行仿真和优化，结果显示，当输入电压为0.9~10 V 时，电路起振时间小于20 ns，输出频率范围为4.5~5.3 GHz，振幅稳定，电路的调谐灵敏度为88 MHz/V，在频偏1 MHz 时的相位噪声低于-108 dBc/Hz。