LINEAR FM CHIRP WAVEFORM FOR A LADAR TRANSCEIVER

摘要

Methods and systems for generating a high bandwidth linear FM chirp for a laser detection and ranging (LADAR) transceiver is described herein. The LADAR transceiver includes an array of laser sources 302 configured to generate a series of pulses with each pulse offset in frequency by a respective frequency offset from a previous pulse and a subsequent pulse in the series of pulses. A ladder signal 304 is generated from the series of pulses and modulated with a modulation signal 314 having a modulation bandwidth corresponding to the frequency offset between each pulse to generate the linear chirp signal 324. The linear chirp signal 324 has a chirp bandwidth corresponding to the number of laser sources in the array 302 and a modulation bandwidth of the modulation signal. The ladder signal 304 includes a plurality of steps, S1, S2, S3, S4, S5. Each of steps S1, S2, S3, S4, S5 corresponds to a pulse in the series of pulses generated by array 302. Each of steps, S1, S2, S3, S4, S5 are separated by a frequency offset X1, X2, X3, X4. The modulation bandwidth is approximately equal to the frequency offsets X1, X2, X3, X4 between each of steps S1, S2, S3, S4, S5. The modulation signal 314 may be provided as a sawtooth linear FM chirp. The modulation signal 314 is synchronized with ladder signal 304 such that the result of the modulation produces linear chirp signal 324 (e.g., contiguous single linear chirp ramp). Thus, a linear chirp signal 324 having a high bandwidth can be generated using a modulation bandwidth that is reduced or less than the chirp bandwidth of linear chirp signal 324. For example, in one embodiment, linear chirp signal 324 can be generated having a chirp bandwidth of 20 GHz using an array having 10 laser sources and a modulation signal having a modulation bandwidth of 2 GHz.