Bipolar nanosecond pulse generation using transmission lines for cell electro-manipulation

Design and operation of a pulse generator based on fast recovery diodes and shorted transmission lines are presented. The generator produces 3.5 ns wide, plusmn350 V amplitude bipolar pulses into 50-ohm load at the maximum repetition rate of 100 kHz. Short bipolar pulses are used for the studies of biological cell response to high electric fields when the net transfer of charge is undesirable. The bipolar pulse is produced from a unipolar pulse by the parallel connection of a shorted transmission line. This transmission line delays and inverts the initial pulse, so the output is the sum of the initial and the inverted and delayed pulses. Proper terminations both at the entrance and the exit of the transmission line system are essential if one is to avoid spurious pulses. If preserving the exact shape of the pulse is not necessary, a parallel L-C circuit can replace the shorted transmission line. This L-C circuit provides near Gaussian bipolar pulse shapes