Re： Harmonic Balance Simulation in ADS

It look O.K,
gain:
1. Look at the Gate (Without DR yet) when you tune OST at S and you might add some matching circuit at the Drain in order to have low impedance at D (You can have a parallel cap or just add Lamda/4 matching section).
2. Expext to have a negative resistance at the freq. range you need.
3. Now before you add the DR, add a TRL at the gate. As you increase the length , the S11 curve rotates around Smith Chart. Locate it to see a paralel resonant as I described befoe.
4. add the DR.

If you post a zap file of ADS files I'll find out why it doesn't work?

Cheers

Ody

Hi All!

attached is the .zap of my design. Hope someone can tell me what I did wrong :)

(NOTE: .zap renamed as .zip)

DJ: I don't quite get what you mean by parallel resonant... I set the load at the Drain to be (-Rfet/3 -jXfet) like what the texts say.... Taking the DR and looking at the gate, i have gamma = 2.5++ and DR gamma is 0.8++ so i should have osc right? The angle of the gammas are also conjugates so both amp and phase condition for osc shd be met....

Thanks in advance!

I will look at that

Hi All!

Any further suggestions? Is there something amiss in my schematic?

Thanks!

Hi All!

I ran out of time so I turned back and focused on parallel feedback DRO.

With some luck and great help from the tutorial on lumped element Osc at rfic.co.uk, I managed to see some Osc! :o Finally!

Much of my initial hiccup come from not paying enough attention and not knowing what the warning messages in the status window meant.

The parallel RLC in my 1st DRO needs to be grounded. Then things will work... :)

Now I need to make the DRO a Self-Oscillating Mixer with conversion gain. Please advice!

DJ's design steps look pretty simple. I found it's also easy to get S11>1 when the TLOC=40. But I found it's so difficult to get 'moving from the uper side of the smith chart to the lower as a function of frequency'. I was required by the HB simulator to get 'clockwise encircle around 1+j0'. I tried all the length from 10 to 360 (degree in ideal line) but can't get that.

Another mystery to me is the meaning of the Osctest imepdance. I don't understand what it physically mean. Why it was set to 1.1 ohm? Sometimes I change it and then I can get S11>1 and clockwise encircle. But I still can't see oscillation in HB.

Help please. Thanks in advance.

Soon

What is this "TL" between the resonater and the Gate?

Hi,

the DR equivalent circuit is TL - parallel RLC - TL. Check this out in uWave texts like Pozar or Gonzalez.... Or "the" DR book is Guillermo.

Khanna,A.P.S., Parallel Feedback FETDRO Using 3-Port S-Parameters,IEEE,

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