Detailed Jitter analysis

020_jitter_sim_detailed : Detailed Jitter analysis

Requires: SmartSpice & Smartview

Minimum Versions: SMARTSPICE 4.18.16.R

This jitter analysis example demonstrates jitter performance for a discrete Colpitts Oscillator circuit due to a noisey power supply. Important SmartSpice features demonstrated in this example include the following:

  • Creating a power supply which includes both random and deterministic noise components.
  • Executing a transient analysis and extracting the JITTER metrics using a .MEASURE statement.
  • Characterizing the oscillator's jitter performance by modifying the deterministic noise amplitude through a .MODIF statement.
  • Observing the distribution effects on jitter performance as the deterministic noise exceeds the random noise.
  • Generating Fast Fourier Transforms (FFTs) to observe spectral distributions in the frequency domain at various points in the circuit.

The inputdeck shows how a nominal 6 volt DC supply is specified to include a random noise characteristic. Next, a sinusoidal source injects deterministic noise into the power supply line with an amplitude determined by the Vac parameter. The series combination of these two sources create the power supply line voltage for the oscillator circuit.

To see how the rest of the oscillator circuit responds to the presence of this power supply noise, a Timing Jitter analysis is performed for all supported metrics over at least 10,000 cycles (the .TRAN statement). Notice that the jitter analysis excludes the oscillator's initial stabilization time (the FROM and TO attributes of the .MEASURE for JITTER).

To understand the oscillator's jitter performance due to random and deterministic noise, the sinusoidal source's voltage amplitude is modified and then Timing Jitter analysis metrics are collected for each Vac value (the .MODIF statement).

The waveforms show all Timing Jitter analysis metrics versus time at each deterministic sinusoidal voltage injected on the power supply line.

The histograms show all Timing Jitter analysis distributions at each deterministic sinusoidal voltage injected on the power supply line. Notice how the period histogram morphs from a bell curve to a bathtub-shaped distribution. As expected, the cycle-to-cycle jitter remains unaffected as the deterministic noise increases.

The spectral plots illustrate the normalized spectral frequency content at each deterministic sinusoidal voltage injected on the power supply line. Notice how the FFT vector information sent to the SmartSpice output window can be suppressed (the set suppressfftoutput = true statement).