Attribute of clock

Following features measure the quality of clock (Deng et al. 2020; Kim et al. 2003; Johnson et al. 1999, Kim and Kang 2002):

1. Frequency: The term frequency is related to the English word, “frequent”, which means to occur many times. Frequency is defined as the number of times a particular event occurs. There are three kinds of frequencies: temporal, spatial and angular frequency. Frequency is reciprocal of the period. Also, frequency is proportional to the inverse of time delay. Thereby, as the delay increases, the frequency decreases. So,f∝1T andf=12ntD.
2. Bandwidth: Bandwidth for any signal is defined as the difference between the upper and the lower frequency that a set of frequencies possess. There are different kinds of bandwidths like pass-​band or base-​band bandwidths. We generally define the pass-​band frequency as the difference that is present in between the cut-​off frequencies at the upper and the lower end. The amount of information is dependent upon the bandwidth that the signal possesses. Also, depending upon different bandwidths different filters are designed.
3. Operating range: It is defined as the frequency range or limits in which any circuit is operational.
4. Jitter: Any periodic waveform that deviates the zero crossings from the original idealistic points is said to be facing fluctuation shown in Figure 14.4.Figure 14.4   Jitter between input clock x₁(t) and x₂(t).
5. Skew: Generally, in most circuits, only the clock signal suffers from skew. The reason being that they travel the largest distances in any circuit and are constant throughout the circuit. Skew, therefore, is defined as different parts in the circuit receiving the same signal at different time intervals as shown in Figure 14.5. This hampers the proper functioning of the circuit on the whole.Figure 14.5   Skew generated between data and buffered clock.
6. Precision: Precision of any system is defined as ability of any system to be able to give the same unrepeated measurements after compiling to the same conditions, and they lead to the same output results as well. The precision of any system is dependent on the system’s repeatability and reproducibility.
7. Fine-​tuning: Any condition in which the parameters should be absolutely and precisely adjusted so as to agree with the output results.
8. Resolution: The capability of any system to be able to distinguish between a set of control values is defined as the resolution of the system.
9. Coarse grain delay-​: Coarse-​grain delay can be defined as the delay that is defined at irregular or harsh intervals of time. This kind of delay is not regularly spaced.
10. Fine-​grain delay: Fine-​grain delay is defined as the delay that can be defined by values occurring over a regular interval of time. The delay is of the appropriate grade.
11. Differential delay calculation: The delay lines cannot be designed for delay elements with an even number of stages because of the problem of locking. The delay elements tend to lock them at a particular value and the signal is not appropriately passed. Therefore, for such delay stages we utilize differential delay calculation, wherein, we add an additional delay element with the help of which we remove the locking error and calculate the delay.