Microwave Detection in a Thermionic Diode

A theoretical analysis of the detection of microwave energy in a thermionic diode is presented assuming a parabolic space-charge potential distribution and that the resultant field acting on the electron is the sum of the static and radio-frequency fields. It is shown that at microwave frequencies the space-charge-limited diode behaves as a velocity-modulated detector. This solution is a valid approximation for signal frequencies in excess of the electron plasma frequency at the potential minimum and for signal amplitudes less than 2Vm/d s[1+(¿2/¿2)]1/2. Here s is the diode spacing, d the potential minimum spacing, the angular frequency, Vm the potential at the minimum and ¿2=2eVm/md2.