Multiple Repetition Frequencies Research Articles

Rapid absolute distance measurement by dynamic chirped pulse interferometry

Frequency combs have given rise to revolutionary progress in a variety of applications. The absolute distance measurement by using frequency comb has been developing rapidly in recent years. In this paper, a method of rapid ranging via the dynamic chirped pulse interferometry is proposed. With the sweeping of comb spacing, the dynamic frequency offset of the sparsest stripes can be obtained in the chirped pulse interferometry, which leads to the cues about the measuring distance. The introduction of dynamic comb spacing can effectively reduce the dead zone of the optical spectrum analyzer. Based on the theory of synthetic wavelength, the multiple repetition frequency can also realize a great non-ambiguity range. In the measuring system, there is no need to lock the repetition rate any more, thereby removing the dependency of bulky phase-locking circuits, and simplifying the system. Besides, the rubidium clock brings the accurate clock reference in the system. Hence, the repetition rate and camera can perform strict synchronization. Considering the improvements of imaging frame rate and the scanning speed of repetition rates, the changed spectral interferograms can be obtained rapidly, and thus compensating for the speed deficiency of dispersive interferometry and cavity tuning. The experimental results show that elapsed time is 74.1 ms for the single time, corresponding to a data updating rate of 13.5 Hz. In a range of 20 m, the measurement uncertainty is well within 27 μm, i.e. the relative precision of 1.35 × 10<sup>–6</sup>.

Novel method for ambiguity elimination in the LFMCW radar

Abstract Aimed at solving the distance and velocity decoupling problems of a moving target in LFMCW radar signal processing, a multiple repetition frequency waveform is adopted and a Doppler frequency duster algorithm is proposed, which is capable of recovering true velocity from the coupled velocity estimation directly. For the resolution of multiple targets, a match algorithm based on mean square error is also proposed. The combination of the above two methods realizes distance and velocity decoupling of multiple moving targets. The result of simulation verifies the effectiveness of the methods, the velocity estimation performance of DFS algorithm is improved by 2.5 dB compared with Chinese remainder theorem.