Dithered Signal Filtering Using S-Transform

Ring Laser Gyroscopes (RLGs) are widely used in many airborne and navigation systems for accurate measurement of the true rotation of the body movement. But the RLG's suffer a serious problem at low frequencies known as Lock-in frequency. To avoid lock-in problem, the RLG is vibrated mechanically to a high frequency which is known as Dithering. In order to get the true rotation of the body the dither signal has to be removed. Three stage cascade filters have been suggested to remove the dither signal. These filters have the disadvantage that either the FIR filter length is too large or the phase characteristics are not linear. In this work Stockwell Transforms are used to remove the dither signal. A masking filter is generated and is multiplied with the S-transform plane in order to remove the unwanted frequencies. The dither signal is completely removed and the phase characteristics are found to be linear in the pass band.