Measurement of continuous-time ΣΔ modulators: Implications of using spectrum analyzer

In this paper, The difference between getting the output spectrum directly using spectrum analyzer and obtaining the spectrum digitally in measuring clock jitter effect on continuous-time ΣΔ modulator is analyzed. It is shown that clock jitter can be seen as input-referred or output-referred, depending on the nature of the measurement tool. Quantization noise and jitter noise are analyzed and compared graphically using a simple approach. The presented analysis is verified with system-level simulation of a 4^th order bandpass continuous-time ΣΔ modulator.