MSFVW beam steering and spreading over large path lengths

The propagation characterisics of magnetostatic forward volume waves (MSFVW) have been investigated in the 2–6 GHz range. The waves were propagated in 2-in. diameter YIG La-doped films of varying thickness (20, 30, 40 μm). The waves were launched by microstrip transducers on an alumina substrate. Receiver transducers were also on the substrate, but placed 1 in. away, in a semicircle with 10° between each of them. Network analyzer measurements were taken of the devices, and comparisons of output channels show that there is a wide spreading of the MSFVW beam, especially the longer wavelengths. The films also exhibited some natural beam steering. The channel which exhibited the least insertion loss was not always the channel parallel to the input. In an attempt to improve beam spreading, a Permalloy technique was used for concentrating dc fields. With this technique the main beam could be guided to either of two receiving transducers. Results have also been obtained for oblique incidence of these volume waves on a closely spaced metallized surface. Some steering effects due to boundary conditions were found. This effect may have device applications for frequency selective steering.