Electronically variable time delays using cascaded magnetostatic delay lines

A magnetostatic wave (MSW) variable time delay device with a phase deviation from linearity of less than 20 deg over a bandwidth of 300 MHz centered at 3 GHz has been demonstrated. The device consists of two cascaded delay lines. One delay line is biased to operate in the surface wave (MSSW) mode to provide a positive slope delay versus frequency characteristics, while the other operates in the backward volume wave (MSBVW) mode to provide a dispersive characteristic with negative slope. Both dispersions have been linearized by modifying the spacing between the propagation medium (YIG film) and the ground plane. The net device dispersion is the sum of the dispersive characteristics of the individual delay lines, and delay variability is achieved by varying the bias field of one of these components. A bias field change of 100 G will change the total delay by more than 40 ns.