Passband ripple observed in MSFVW delay lines

The long-period (100-200 MHz) ripple observed in MSFVW devices is here attributed to variation in the DC demagnetizing field across the width of the sample. Calculation shows that MSWs launched near the middle of the sample, where the field variation is weak, are brought to a focus at distances surprisingly close to the input transducer, and that ray bending is stronger outside the central half of the sample. Observation confirms the strong effect of sample width on the breadth and smoothness of the passband.