Content area
Full Text
ABSTRACT
Based on the measurement principles used on incoherent scatter radars, the authors have developed the Simultaneous Multiple Pulse Repetition Frequency (SMPRF) code that is intended to solve the range-Doppler dilemma and that can be used with modern magnetron radars. The working principle of the code is explained in mathematical terms and with the help of a simplified model. Results from the SMPRF and traditional fixed PRF weather radar measurements are compared, and the reasons for the differences are explained. The practical results show that the SMPRF code seems to work in the manner that is predicted by the theoretical and model calculations. The SMPRF code provides enough information to produce a high-resolution measured spectrum for each range gate. The shape of these measured spectra are seldom purely Gaussian. It is possible that more advanced raw products, other than just reflectivity, velocity, and width, can be produced with the help of these high-resolution spectra.
1. Introduction
These two equations show that as the PRF increases, the maximum velocity increases but the maximum unambiguous range decreases, and vice versa. In the literature, this phenomenon is referred to as the "range-Doppler" dilemma or the range-velocity ambiguity (e.g., Doviak and Zrnic, 1993). There have been various attempts to overcome this problem (Sirmans et al. 1976; Laird 1981; Zrnic and Mahapatra 1985; Gray et al. 1989; Sachidananda and Zrnic 1999), but these papers have only been able to provide partial solutions.
Within other fields of radio science, radar methods have been developed that are not limited by the range-Doppler dilemma. Such methods have been presented, for example, by Farley (1972), Greenwald et al. (1985), and Lehtinen and Häggström (1987) for the ionospheric radar studies. However, these solutions are not directly applicable to the weather radar case. Yet, the coding methods that are used with the ionospheric radars give the tools for a possible solution of the dilemma. A solution was suggested in the Cooperation in Science and Technology (COST) 75 final seminar (Pirttilä et al. 1999), with an example of a code that could be used in practice and a simulation-based evaluation of the performance of the code. The name of the code is Simultaneous Multiple Pulse Repetition Frequency (SMPRF) (Lehtinen 2001). The solution is based on sending...