The Production of Ultra-High-Frequency Oscillations by Means of Diodes

Abstract

The general problem of obtaining oscillations by the use of diodes with critical electron transit time is outlined, Some of the properties of a 10 em. oscillator tested experimentally are included. Extraneous losses were reduced when the oscillator was enclosed within a wave guide.T H E theory of the production of negative impedance by means of an electron discharge between two parallel planes has been known for some years.' The negative resistance appears whenever the electron transit time is approximately 1~, 2~, 3~, etc. cycles of a given high-frequency current. Using this property, Muller was able to construct tubes giving 100 em. oscillations," The operating efficiencies were quite low, and in the frequency range covered by these tubes it seems fairly conclusive that other methods of producing oscillations are more effective than the critical transit time diode. However, there is promise in the application of diode operation to much higher frequencies than those of Muller.In a diode where the electron discharge occurs between two parallel planes where one performs the function of electron emitting cathode and the other constitutes an anode biased at a positive potential, the effective impedance presented to an external source is inherently low in magnitude. This is because of the capacitance between the two planes which causes the decrease in impedance at high frequencies. For the production of oscillations, the capacitance must be combined with a resonant structure having the proper inductance to resonate at the desired frequency and having a resistance which effectively is less in magnitude than that of the electron stream. Because of the low losses thus required of the coupling or tuning circuit the properties of concentric lines and of tuned cavities offer a favorable method of attack. These structures also have the property that the impedance presented to the diode proper may be made low to match its capacitive reactance at the high frequencies desired.The two most important sources of circuit resistance are ordinary ohmic loss modified in the usual way by skin effect in the conducting 1 For numbered references see end of paper. 280

Transit-Time Effects on the Electrical Admittance of a Corona Discharge

“…Puede ser visto que la capacidad equivalente crece 50% en aproximadamente una octava. Además la conductancia puede tomar valores negativos; una característica que fue explotada en osciladores 12 . Este modelo no puede ser aplicado directamente a una descarga corona porque, a pesar de las similitudes, los procesos físicos fundamentales no son los mismos.…”

Steady-state and small signal analysis of terahertz ballistic tunnel transit-time oscillator

“…From figure 4 we can see that two obvious dynamic negative resistance windows in the terahertz range are clearly shown under each current density despite the influence of the electron dispersion nonparabolicity. The first negative window seems to have more attractive potential of application [25,26]. Since the electron tunnelling time is much shorter than the transit time, according to the operation principle of a transit-time diode, we can change the length of the transit space or use different material to control the negative window frequencies.…”

Ballistic and quasiballistic tunnel transit time oscillators for the terahertz range: Linear admittance

“…There were several successful tries at exciting high-frequency oscillations in the first ͑the lowest frequency͒ of these windows. For example, oscillations with the wavelength ϳ11.5 cm were generated 16 in vacuum diodes with thermionic electron emission.…”