A spectrum analyzer is described which comprises a mixer for mixing the conjugate complex input signal v* into a base band signal x, and a resolution filter for narrow-band filtering the base band signal. MEM devices, in accordance with the current invention, have one or more movable micro-structures which are preferably ribbon structures or cantilever structures configured for modulating light. When the preset end of the flip-flop receives the pulse signal, and the maintaining time of the pulse signal is maintained for a predetermine time, the flip-flop output end is set to a high voltage level. Namely, the channel filter module is activated only for the digital samples located around the known discontinuities and is deactivated for the remaining digital samples. If the fail flag is present in a chip, that chip is repaired by electrically associating the column address with redundant memory cells rather than the original memory cells.