velocity modulation in klystron cavity using square wave

Hi,

will the square wave at input of the klystron cavity undergo velocity modulation.... please hep...

The problem is that the square wave has to generate a voltage across the cavity gap to bunch the beam. Now if your cavity is tuned to the square wave it will sort of work, but only the components within the bandwidth of the cavity will generate any voltage across the gap and hence any bunching effect.
Frank