Measurement of Internal Reflections in Traveling-Wave Tubes Using a Millimicrosecond Pulse Radar

This paper describes a test method which enables one to locate reflections on traveling-wave tube helices and to measure the return loss of each reflection. This information is needed for traveling-wave tubes used in pulse code transmission since "echo" pulses arising from reflections can distort the meaning of the code. This test method employs millimicrosecond pulses in a radar circuit with a stroboscopic viewing system. The sensitivity of the system permits easy observation of reflections having return losses as high as 40 db. Using this method we have been able to identify two previously unsuspected sources of helix reflections.