Non-Invasive Configuration and Disturbance Observer-Based Scheme for Guidance Signal Extraction in AESA Seeker

A missile engaging a moving target requires an estimate of the missile target sight line rate for generating appropriate guidance signal to steer the missile towards the target. The estimated missile target sight line rate, which is often called the guidance signal, is obtained from an onboard seeker after signal processing and due isolation/filtering of the missile body rate. Instead of electromechanical motion of the sensing element of the seeker, modern radio frequency seekers use electronic beam steering and such seekers are strapped down with the body of the missile. As there is no mechanical isolation in a strapdown seeker, filtering of the body motion needs special techniques, which use signals from the missile mounted rate gyro. Conventionally the rate gyro signal is injected invasively in the signal processing loop for compensating the body motion. A non-invasive configuration is proposed in this work where the body motion compensation is carried out outside the signal processing loop. Additional filtering using disturbance observer is further proposed to improve the performance of the seeker. To mitigate the effects of finite resolution in the beam shifter, a digital noise mitigation scheme is also incorporated in the proposed seeker configuration. The performance of the proposed seeker configuration is evaluated for nominal and off-nominal conditions.