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# My ADS circuit oscillates but ha no harmonics.

#### skatefast08

##### Full Member level 3
What could I possibly be doing wrong with my harmonic simulation in ADS, when my transient has an oscillation between -500 mV to 500 mV. Shouldn't I get a harmonic magnitude at the frequency of the oscillation?

That signal may not be large enough to bring in any diode
nonlinearities, and then you would not generate those kinds
of "squaring / clipping" harmonics.

Try +/1V and see what changes.

How you have organized your HB set-up ??
Post it here.
Because HB set-up for oscillators is little bit tricky. You should define well some important HB metrics otherwise HB might not be converged or even give errors.

I actually got it to work. I guess the reason was that I put in the wrong fundamental frequency in for the harmonic balance. I put in 1 GHz, when its supposed to be around 4 and 5 GHz. Below is the 1 GHz harmonic balance simulation and the 2nd picture is the 5 GHz harmonic balance. I also don't understand how I still get an oscillator when my phase shift at 5 GHz is only 43 degrees when doing an AC simulation see 3rd image for this.

Lastly, I want to vary the frequency by varying a transmission line configuration for a resonator. how would you go about this? Also how do you get an ocillator when your phase shift is only 43 degrees?

Thanks

--- Updated ---

Note: Transistor being used is: pf_hp_ATF21170_19931015

Last edited:

Hi BigBoss, I actually used an RFC this time, used an emitter resistor to lower my amps to get 20 mA and used a 3VDC power supply. I actually get no harmonics now, since I used an RFC. I dont understand why I get a transient with about 9 GHz and I used a 9GHz fundamental frequency, but no magnitude like last time.

What is that ? 9GHz oscillator ??
I don't have time to comment this weird circuit.

Still no harmonics, but I got them oscillations going . Same circuit as before, but instead using EM simulation for the circuit board

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