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Previous Page: Maximum Unambiguous Velocity (V_{max}) and PRF
Doppler DilemmaBoth the R_{max} and V_{max} are dependent on the PRF. However, they do not have the same dependence. Notice in Equation (7) and Equation (9) that R_{max} has an inverse dependence on the PRF, while V_{max} has a direct dependence. An increase in the PRF will result in a decrease in R_{max} but an increase in V_{max}. Also, a decrease in the PRF will result in an increase in the R_{max} but a decrease in the V_{max}. Although a high V_{max} is desirable for obtaining quality Doppler velocity information, this comes at the expense of using a high PRF and thus a shorter unambiguous range (R_{max}). The high PRF results in a short R_{max} and increases the chance for multiple trip echoes. See Section 6-7 for the various operational PRFs and the corresponding R_{max} and V_{max} values. The dependencies that R_{max} and V_{max} have on PRF is important to WSR-88D operators because PRFs are (in some cases) editable. A low PRF is desirable for target range and power, while a high PRF is desirable for target velocity. The inability to satisfy both needs with a single PRF is known as the Doppler Dilemma. The Doppler Dilemma is addressed by the WSR-88D with algorithms that will be presented as part of Topic 3. |