Disturbance Rejection Rate Analysis and Parasitical Loop Filter Design for Strap-down Seeker

In order to reduce the disturbance rejection rate of a strap-down seeker by designing a suitable parasitical loop filter, the disturbance rejection rate mechanism for a strap-down seeker was analyzed firstly. A uniform formula of the disturbance rejection rate was derived for the indirect extraction and direct extraction methods of the inertial line-of-sight (LOS) angular velocity. And its influence on the guidance loop was discussed, from which it can be found that the gyroscope and seeker played an important role on the disturbance rejection rate. Parasitical loop filters that consisted of gyroscope filter and seeker filter was designed to reduce the disturbance rejection rate by guaranteeing the consistency of the time-frequency characteristic between the signal from the seeker and the one from the gyroscope. A simulation was given to prove the validity of this loop filter and its influence on the stability of the parasitical loop.