Theory and design of a half-mode SIW Ferrite LTCC phase shifter

A half mode SIW based Ferrite LTCC phase shifter is presented in this work. A theoretical model to predict the phase shift in the partially magnetized state has been derived. Contrary to the bulky external magnets employed by conventional ferrite phase shifters for biasing, this design uses bias windings embedded within the ferrite substrate. This not only enables miniaturization but also reduces the required bias fields considerably by avoiding the demagnetization effect (fields lost at air-dielectric interface for external biasing schemes). The design is optimized with the aid of magnetostatic and microwave simulations which are later verified through measurements of a prototype. The fabricated phase shifter provides a differential phase shift of 110°/cm and an FoM of 55°/dB for an applied DC current of 240 mA.