The Use of Sun, Quiet Sky and Earth Noise Measurements for Determining System Parameters, with Error Analysis

摘要

The graphs of figures 4 and 5 apply the three-noise measurement scheme for determining system performance parameters, g/t, t and g. These are suitable for determining the performance, but perhaps a better method is the simple Basic program of Appendix I. The program quickly shows the specific answers for the measurements taken. The graphs are best for gaining insight about the method. One can see the way in which the performance parameters vary as the measurements vary. The program calculates the sensitivities for g/t, t_R (or t) and g to errors in the various input variables. A normalized sensitivity of 1 indicates that a small percentage error (or small dB error) in an input variable will resuk in the same percentage error (or dB error) in the performance parameter. Other values of the normalized sensitivity scale the parameters accordingly. After estimating the performance parameters, the sensitivities should be used to find the general order of magnitude of the errors. It is not generally necessary to make a statistical combination of the sensitivities. In order to compare system performance between different times, as well as to compare different systems, it is necessary to have obtained a value for the solar flux and the temperatures of the quiet sky and Earth. This requires a bit of extra effort, but allows a much more useful estimate than Sun-noise ratios. The step of computing g/t, t_R (or t) and g provides the most useful form of the answers. Finally, if the magnitude of the errors are estimated, it is possible to place statistical bounds on the performance parameters. Finally, here are some general rules for consideration: 1. Whenever taking Sun noise measurements, also take Earth noise measurements. 2. Obtain current solar flux numbers and interpolate for the frequency used. 3. Convert Sim noise into g/t values and use this as a primary measure of receiving performance. 4. Calculate the receiver and system noise temperatures. 5. Calculate the antenna gain, as it is the single parameter that relates to transmitter performance. 6. Try to estimate the errors in the measurements and parameters. 7. Keep the measurements in a notebook where they can be found when questions arise!