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11.2GHz Dielectric Resonator Oscillator design

Question asked by erons on Feb 23, 2013
Hello all,

I am designing a DRO at 11.2 GHz for my master’s thesis.  I added capacitive feedback to the emitter of the transistor by means of a short-circuit stub to achieve negative resistance.  
I have negative resistance and an unstable transistor but when I load the transistor by adding the Dielectric resonator at the base of the transistor, and look at transient I don’t get oscillation. I expected some oscillation. I mean get some oscillation but it dies out. I attached a simulation of the transient.

After loading the transistor with the the Dielectric resonator at the base I lose most of the negative resistance. It goes from -66 to -0.6 negative resistance.

I believe this is because I don’t have a reasonable negative resistance (maybe It’s not negative enough –Im not sure). Is there a way I can further make the transistor more unstable?
I am using a  BFU710F - NXP transistor.

I have attached the simulation of negative resistance and also I have attached my transient simulation. Maybe I'm looking at this the wrong way, any advice will be appreciated. Please let me know if any misunderstanding.

This is my first time posting in a forum, so I apologize for any wrong I may have committed. 

Thank you for your time