Evaluation of FM pulse compression for weather radars

Accurate estimation of the average echo power received from precipitation requires a considerable number of independent echo samples to be averaged. In order to obtain independent samples precipitation particles should have enough time to move into independent positions between pulses. This implies long dwell times for accurate estimates. Consequently, scan speeds are slow. Independent estimates are also obtained from a single pulse at range intervals of half of the pulse length. Dwell time can be reduced by integrating these range samples, but this reduces range resolution as well. Pulse compression provides means of increasing range resolution much beyond the typical resolution obtainable from conventional radar. In consequence, pulse compression radar produces many independent samples from each range interval corresponding to the resolution of the shortest pulses of conventional radars. These can be averaged to obtain accurate estimates even from a single pulse, or from only a few pulses. This facilitates the use of higher scan speeds. This possibility is evaluated in connection with the University of Helsinki full coherent klystron weather radar