False Alarm Rate and False Alarm Number for Discrete and Continuous Time Sampling

A comparison of the false alarm rates and false alarm numbers for discrete and continuous time sampling is given for different noise spectrums (rectangular, Hamming, Gaussian, and cosine noise voltage spectrums) and for different sampling rates for the case of discrete time sampling. Also given is the increase in the false alarm rate when going from discrete to continuous time sampling when the detection threshold is held fixed. The amount that the threshold has to be increased for continuous sampling to achieve the same false alarm rate obtained with discrete time sampling is also given.     

Faraday Loss for L-Band Radar and Communications Systems

The mechanism of Faraday rotation as it affects radar and communication propagation has been extensively treated (1, 7). The purpose of this paper is to point out the magnitude of the effect and its possible consequences which have not been appreciated. Contrary to what many believe, the two-way Faraday rotation angle and loss can be large at L-band for ground-based, linearly polarized radar systems observing targets above the ionosphere. Similarly, the one-way Faraday rotation and loss for linearly polarized, ground-to-space pace communication links at comparable frequencies can be large. The magnitude of the rotation loss depends on the location of the radar or communication station in latitude and longitude, the condition of the ionosphere, and the elevation and azimuth angles of the target. For example, based on the total electron content in 1970 (a peak sunspot activity year) at L-band, a two-way Faraday rotation greater than 50°a loss greater than 3.8 dB is calculated to occur at 60° N, 70° W, 75 percent of the time between the hours of 10 A.M. and 4 P.M. for nine months, and 22 percent of the total time for the entire year, when looking toward the south magnetic pole at low elevation angles. For the same year this rotation and loss at 15°N, 150° is calculated to occur 48 percent of the total time when looking south at low elevation angles.