Perturbation theory for multistrip acoustoelectric surface-wave amplifier

The ‘multistrip perturbation theory’ of the coupler has been extended to the multistrip amplifier. A study of the acoustoelectric gain shows that, if the number of strips per wavelength is very large, the gain becomes that predicted by Adler, but the number of strips per wavelength required to reach this condition increases drastically with the conductivity of the semiconductor; it also shows that the width of the strips on the semiconductor should be as large a fraction as possible of their period, and that, if the conductivity of the semiconductor is low and the number of strips per wavelength is small, gain can be obtained from electrons drifting at a velocity less than the sound velocity in the opposite direction to the surface wave, and, in some cases, even in the same direction.