Digital Baseband Signal Combining

Abstract

Unlike conventional pre- or postdetection digital signal combining approaches, the Digital Baseband Symbol Combiner (DBSC) utilizes detected baseband symbol metrics from the individual antenna-receiver system symbol synchronizers as inputs to the combining process. Additionally, symbol timing from the individual synchronizers is used to aid the DBSC perform closed-loop tracking and doppler rate compensation. The DBSC can be shown to provide an equivalent signal-to-noise ratio (SNR) improvement as the conventional approaches when the individual antenna-receiver system noise is characterized as gaussian and resulting symbol metrics are considered statistically independent. This paper discusses the theoretical approach to a proposed symbol combining technique which would provide near optimum real-time data in support of the NASA Space Shuttle Orbiter ascent-phase operations at the Merritt Island complex, Kennedy Space Center, Florida.