A quasi.atntic scheme ia used to study the dynamic properties and opt.imum operation conditions of the DD X-band 1.0-Hi-Lo silicon IMPAlT diodes. The carried ionization rates in a form . = A oxp (-BIE) are assumed the scattoring-limited velocities of the oarriers and sre taken a t an operation tempornture of 150'C. for the analysis of the diode. Large signal values of admittance. efficiency, powor output and phaae relationship between the svslenche current and the oscillation voltage are calculatad a s functions of the d.c. bias current, tho r.f. voltage swing, and tho operation frequency. Current-tuning effect is inferred to play an important role in tho device design. Furthermore, efficiencies and power outputs of diodes are also calculated a s functions of the avalancha-to-drift voltage ratio V * / V o . Tho best diode we propose is 9=20.3% and P = 3 . 7 watts a t 50% modulation near I'A/VD=0.88.