Phase Linearity in Telemetry Reception

Abstract

The problem of phase nonlinearities in telemetry-receiving systems is studied. The principal data-degrading effect is shown to be intermodulation distortion of FDM telemetry signals. Another form of data degradation, namely, intersymbol interference in TDM telemetry signals, is found not to be related directly to phase nonlinearities, but rather to the transient response of the receiving system. The noise-loading technique is introduced as an effective means of characterizing, analyzing and measuring intermodulation distortion. Some analytical results are cited relating the amount of intermodulation distortion to signal and receiving-system parameters. Analytical details are omitted, the emphasis being placed on interpreting the significance of the results to the telemetry systems engineer. The experimental verification of these relationships is briefly reviewed. The results are used to establish quantitative tradeoffs between the performance parameters of receiving systems. These tradeoffs are then used in formulating methods of specification and design to ensure high data quality.