Magnetoelastic bandwidth compression

A bandwidth compression process is described which uses the magnetoelastic normal modes of a ferrimagnetic crystal as independent subharmonic oscillators. The critical power level and mode density for this process are discussed and dynamic range is shown to be strongly dependent upon crystal geometry. Measurements have been made on a device with a 60-MHz input frequency and a 30-MHz output frequency. Spectrograms of voice signals before and after two-to-one bandwidth compression are presented and the possibility of obtaining bandwidth expansion is discussed briefly.