High output power driving sub-harmonic mode of operation of 140 GHz Si-IMPATT

Over the past few years, a major field for application of 2 mm wave IMPATT oscillators has developed in the area of sensor systems and compact short range radars. It is therefore important to increase the output power and efficiency of IMPATT diodes at upper mm-wave frequency bands. It has been shown (Swan, 1968; Mouthaan and Rijpert, 1969; Belousov and Novozhylov, 1990) that tuning the second-harmonic mode of operation of IMPATT diodes is one possible way to increase the output power and efficiency of the diodes. The addition of a properly phased second harmonic voltage improves phasing of the RF current relative to the fundamental voltage so as to increase the negative conductance and give an increase in the output power at the fundamental frequency. However, at the mm-wave frequency band, the negative resistance of the diode at the second harmonic is about ten times less than at the fundamental frequency and its value is comparable to the value of the diode parasitic resistance. Thus, the tuned second-harmonic mode operation of the mm-wave IMPATT diodes is not as efficient as at lower frequencies. This paper presents results of investigation of 2 mm-wave Si IMPATT diodes under driving sub-harmonic mode operation. The drift-diffusion model (Belousov et al, 1979) was applied to the numerical calculation of the diode's dynamic performance.