A novel tunable microwave broadband resonator, inspired from optical laser systems, is presented. In contrast to usual harmonic resonators, the proposed device is based on broadband composite right/left handed metamaterial lines. This line, configured as a resonator, provides nonuniform spectral resonances due to the nonlinear nature of its dispersion curve. This is exploited in the impulse regime, where the input pulse spectrum is discretized inside the resonator, with different spectral separation as a function of the carrier frequency. This discretization leads to a pulse periodicity in time, with a tunable output time period. On the basis of the new broadband resonator features, a pulse rate multiplication device is proposed. This device provides an increase in the repetition rate of a periodic input pulse, with the additional advantage of repetition rate tunability.