Computer simulation of the velocity matched gate

Numerical calculations based on the coupled-wave equations have been carried out with various conditions for the operation of a velocity matched gate. The influences of velocity mismatch, impedance mismatch, and the attenuation of the modulation signal are studied. Our results show that velocity match is critical for very narrow gate. However, impedance mismatch is unimportant for the operation of such a gate. In fact, a standing wave gate can also generate short pulses provided the length of the device is much greater than the wavelength of the modulation signal. It is also shown that the side lobes of the pulses can be suppressed by tapering the coupling.