A phase modulation technique for a sevenfold statistical improvement in incoherent scatter data-taking


  • Michael P. Sulzer


A new technique for improving the quality of data in incoherent scatter measurements is described. The technique is useful under high signal to noise ratio conditions; the number of independent samples in the estimates is increased a factor of 7 by the simultaneous transmission of multiple frequencies. This either increases the time resolution by a factor of 7, or decreases the statistical errors by a factor of the square root of 7. Three important factors concerning the implementation of the technique are discussed: (1) the generation of the multiple frequencies, (2) the required frequency spacing to assure independence of the estimates, and (3) a practical technique for combining the independent estimates. A phase coded pulse is used to generate the seven frequencies with nearly equal power. Specially designed baseband filters are used to avoid distortion in the temperature and velocity measurements. Data demonstrating the improvement are presented, and the application of the technique to other radar uses, such as tracking radars, is discussed.