Irregular pulse repetition time (PRT) implies irregularly sampled signals in pulse radar. Irregular PRT is intentional because it improves the radar anti-jamming performance. This radar specific case involves not only standard analysis from irregular samples but also demands additional research. The frequencies above the sampling frequency should be sought, and unwanted signals (so-called clutter) should be suppressed. The state of the art, especially the applicability of the discrete Fourier transform (DFT) and frame decomposition, is investigated. Solving for the desired frequencies and filtering the clutter are treated as the most serious of all radar specific problems.