ABSTRACT

the name implies the phase locked. is basically a non-linear feedback system whose ba ic function is to track the phase of input signals (reference signal) with the phase of output signals, generally the phase locked loop is consisting of three basic building blocks i.e phase detector loop filter and voltage-controlled oscillator. The function of phase detector or phase comparator is to compare the input frequency and output frequency that comes to it from the output of voltage controlled oscillator by feedback path, the output of phase detector is proportional to the difference of input and output frequency and the output of phase detector is applied to the low pass filter and the function of low pass filter is to remove high frequency noise and creates the particular
d.c level by removing the dynamic characteristics of PLL. Dead-zone can significantly increase the phase error, which may impact the locking and can bring the system towards unlocking. Due to dead zone there will be increase in phase error due to increase in phase error there will be shift in frequency of two signals which causes distortion in phase of two signals which break the locking of two signals i.e dead zone impacts the steady state response of the system and can disrupt the system. Dead-zone may cause longer settling time of the system. at the initial stage loop response is completely unlocked after unlocking loop response is trying to lock in transient state and leading towards the steady state i.e smooth tracking. When dead occurs it disturb the system response for few cycles then it is compensated by charge pump and the phase error is diverging. Since the dead zone is very small in pico seconds which is negligible that significantly impact the locking of two signals. If it is increased even in micro or mili seconds may completely make the system unstable