Stripmap SAR is a radar mode used to image terrain from an airborne platform; it does so by transmitting and receiving a series of electromagnetic pulses. Pulse interleaving attempts to execute two or more stripmap tasks simultaneously by transmitting pulses for additional tasks while waiting for the pulses from other tasks to return, where a task is simply an area on the ground to image. Other research has done this by dividing the front-end of the radar into separate sections and aiming the energy into different beams, each pointing in a different direction or devoted to a separate area to image. This thesis focuses on utilizing the same beam for pulse interleaved scheduling. This research identifies a method for creating a schedule using pulse interleaving when given a set of stripmap tasks. Scheduling is not done in real time, but is instead done before the schedule will be executed. Interleaving is performed on two tasks overlapping in execution time in the following way. The PRFs of the two tasks are altered within their allowable limits so that they match each other. Then, the sent pulses and return envelopes, the times when the pulses might return based on the aircraft's distance to the target and its dimensions, are separated temporally by adding delays to one or both of the tasks' transmitted pulses. Doing this removes the possibilities of transmitting a pulse for one task while receiving the pulse from another task, needing to transmit for two tasks at the same time, or receiving pulses from two different tasks at the same time. This process is easily extrapolated to more than two tasks which are scheduled to execute in the same block of time. To compare the results of the interleaved scheduler, several greedy algorithms in which no interleaving is permitted were also created. In every case, the interleaved scheduler outperformed the greedy algorithms. Several situations were created to imitate different flight conditions as well as radars with varying duty factor limits and output power capability. The performance of the interleaved scheduler was consistent in all situations. This research demonstrates the benefits of pulse level interleaving when scheduling multiple stripmap SAR tasks in a short period of time.
- Professor Miriam Leeser (Advisor)
- Dr. Paul Monticciolo (Advisor)
- Professor Waleed Meleis