Probability Distribution of Received Interference Levels in the HF Band
NAVAL RESEARCH LAB WASHINGTON DC
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HF interference typically spans a wide dynamic range and often has a high density of detectable interferers. In the design and evaluation of communications systems it is often useful to be able to characterize the HF environment by means of an analytic model. Based upon a series of recent measurements of the HF environment, we have concluded that a lognormal distribution is a reasonable model of the observed HF interference. These data were collected using a wideband 2 MHz, high dynamic range spectrum analysis system, and consisted of short-term time averages of the magnitudes of FFT bin outputs spaced at 610 Hz. Spectral plots and associated probability distributions are presented spanning a frequency range from 1.5 to 19 MHz for various averaging parameters. In almost all cases, the distributions of the bin averages were found to be well modeled by the lognormal distribution for levels well above the background noise. In some cases, the fit was excellent over a 50 dB range of levels.
- Electricity and Magnetism
- Radiofrequency Wave Propagation