Time, Frequency & Spectrum#

Signal characterization in time and frequency domains. Rise times, jitter, clock accuracy, harmonics, bandwidth, spurs. Moving beyond “is it there?” to “what exactly is it?”

• Is this clock at the right frequency? — Frequency measurement with counters, scopes, and FFT. Crystal oscillators, PLLs, RC oscillators, and clock dividers.
• What’s the rise/fall time? — Edge speed matters for signal integrity, EMI, and logic timing. Measuring edges accurately (and knowing when the scope is the bottleneck).
• What harmonics are present? — FFT and spectrum analysis. Identifying harmonic content, switching artifacts, and unexpected frequency components.
• What’s the actual bandwidth here? — Measuring the real bandwidth of amplifiers, filters, and signal paths vs. what the datasheet claims.
• Is there jitter, and where is it from? — Timing variation on clocks and data signals. Random vs. deterministic jitter, period jitter, and cycle-to-cycle measurements.