In recent years, many modern phased array radars are built with commercial-off-the-shelf components, and the functions of many hardware components are also re-implemented by software modules. In such systems, radar tasks could be modelled as distributed real-time tasks which require end-to-end deadline guarantees and have precedence constraints. Different from most previous work on either algorithms with restrictions in resource utilization or heuristics without analytical ways for schedulability guarantees, the objective of this paper is to propose a joint real-time scheduling algorithm for both Transmitter/Receiver and Signal Processor workloads with an analytical framework for off-line probabilistic analysis and on-line admission control. The strength of our approach is verified by analysis results and a series of experiments based on a real phased array radar for air defense frigates [6].