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In this paper, two novel approaches to optically generating high-frequency chirped electrical pulses with tunable chirp rate using a tunable nonlinearly chirped fiber Bragg grating (NL-CFBG) are proposed. In the first approach, a high-frequency electrical chirped pulse is generated based on optical spectral shaping and nonlinear wavelength-to-time conversion using a tunable NL-CFBG. In the second approach, two ultrashort pulses at different wavelengths are dispersed at an NL-CFBG. The beating of the two differently dispersed pulses at a high-speed photodetector generates a chirped electrical pulse with tunable chirp rate. The NL-CFBG used in the proposed systems is produced using a simple technique based on strain-gradient beam tuning. Mathematical models to describe the chirped electrical pulse generation are developed, which are verified by numerical simulations. The first approach is also verified by a proof-of-concept experiment.