【摘要】 通过调制VCO实现FSK调制的锁相频率合成系统,由于环路误差传递函数的高通特性会使低频调制频偏(或相偏)降低甚至消失,针对这个缺点,提出了双调制的方法,即同时对基准源和环路的VCO进行调制。在一定条件下,双调制后的频偏不受环路的影响且又能保证调制载频的高稳定度,通过计算给出了满足这种条件的关系式和实际电路的表现特征及实现方法。实验证明该方法效果显著,可实现低频至直流任意信号的调制。更多还原

【Abstract】 Because of error transfer function′s high pass property in loop circuit,frequency offset(or phase offset) would diminish even disappear in FSK modulation system of PLL synthesizer which realized by modulating VCO.This paper proposes dual-modulation to solve this problem which is the way to modulate reference source and VCO of loop circuit at the same time.Under some circumstance,frequency offset of dual-modulation would not be influenced by loop circuit.And high stability of carrier frequency would be guaranteed.Through calculation,this paper gives the formula,the character of the circuit and the way how to meet the demand above.Dual-modulation can realize modulation with any signal from low frequency to DC.And it is proved effective through experiments.更多还原