A linearly dispersive magnetostatic delay line at X-band

Abstract

Experimentally verified calculations which have been performed show that the group delay versus frequency characteristic for magnetostatic forward volume waves in a YIG film of thickness t spaced an equal distance t from a ground plane can be essentially linear over a substantial frequency range. In particular, results are reported on an experimental YIG magnetostatic delay line which showed a linear delay ranging from 50 to 230 nS/cm (linearity ±3 nS/cm) over a 1 GHz bandwidth at X-band frequencies. The 20 μm thick YIG film, grown epitaxially on GGG, was spaced 20 μm above a ground plane using an alumina dielectric. The alumina was fabricated by: (a) thinning a conventional substrate by grinding and polishing; or (b) depositing Al 2 O 3 by rf sputtering. Input and output transducers were simple 5 mm long by 50 μm wide gold microstrip lines defined in 5 μm thick gold and open circuited at one end. Results obtained using a network analyzer were in close agreement with the theoretical calculation. The characteristic observed represents a potential pulse-compression factor of 230.