Study and Experimental Investigation on Sampling Rate and Aliasing in Time-Division Telemetry Systems

Abstract

A study to determine the effect of 1) data power spectrum, and 2) system design parameters on aliasing and data interpolation error has been conducted. Results are applicable to time-division multiplexed telemetry systems. In particular, the results apply to the commonly used PAM-FM, PDM-FM and PCM-FM telemetry systems and PACM-FM. Data was obtained on the basis of combined analysis and experiment with emphasis on the derivation of experimentally proven design parameters. The program consisted of three phases: 1) A study was conducted to determine typical telemetry data spectra; 2) analysis was performed to predict accuracy performance of practical data and interpolation filters using selected examples; 3) experimental tests using data spectral models were performed to derive proven interpolation accuracy performance on the basis of practical filters and design parameters. The experimental tests utilized a PAM-FM system to derive an accurate measurement of attainable performance and to indicate when other equipment factors begin to impose a limit on data recovery accuracy. Spectral models representing typical spectral data characteristics are presented. In addition, some of the more important conclusions relating to operating parameters are presented.