Spectrum analyzer circuits and methods are provided which implement “zero-IF” (direct conversion) or “near-zero IF” (or very low IF) architectures that enable implementation of integrated (on-chip) spectrum analyzers for measuring the frequency spectrum of internal chip signals. An integrated spectrum analyzer circuit, which includes a zero IF or near-zero IF framework, enables a low-power compact design with sufficient resolution bandwidth for on-chip implementation and diagnostics of internal chip signals.