Detection Range/Spatial Resolution Enhancement of Coherent Doppler Wind Lidar Based on Improved Simplex Coding

For the first time, a correlation-free coding technique is demonstrated for improving the detection range of coherent Doppler wind Lidar (CDWL) while roughly maintaining the spatial resolution of single-bit duration. Based on the probing pulses modulated by the improved simplex codes (ISCs), backscattered echoes can be considered as the linear superposition of the Lidar responses, each of which corresponds to different detection locations. Then, the Doppler spectra/wind profile approaching the spatial resolution of a single-bit duration can be recovered after decoding, time delay compensation, and accumulation. In contrast to those coding techniques that rely on correlation, the proposed method can be unaffected by the unequal amplitudes of coded bits that are stable between pulses. Theoretically, in simulated atmospheric echoes, it is confirmed that the degraded spatial resolution caused by wide overall emitting pulses can be mitigated while the reliable detection range can be improved. Additionally, experimentally constructed coding CDWLs using 9, 16, 32, and 64-bit ISCs show improvements in detection range that are consistent with the theory.