Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
My Hobby Website:
Failed Harmonic Balance of Oscillator using ADS - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: Failed Harmonic Balance of Oscillator
using ADS Posted: Fri Jul 18, 2008 10:54 am
Joined: Tue Feb 27, 2007 6:16 am
I have managed to gain access to the use of the ADS simulator.
Below is an Oscillator I modified for my purposes.
Below is the results of the S parameter simulation. As you can see
it appears to oscillate at 120MHz.
Unfortunately when I
try and perform the Harmonic Balance Simulation (I wish to determine
phase noise), the simulation fails.
Does anyone have
any suggestions as to how I can correct the problem?
Regards, Darcy Randall, Perth, Western Australia
Post subject: Posted: Fri Jul
18, 2008 10:57 am
Joined: Tue Feb 27, 2007
On a last note, referring to the results figure,
whats the difference between the option of plotting analysis.sp1.s(1,1)
Darcy Randall, Perth, Western Australia
Post subject: Posted: Fri Jul 18, 2008 4:33 pm
Joined: Tue Jul 08, 2008 7:15 pm
It looks like you are trying to model a
crystal oscillator. It can be difficult for simulators to converge when
circuits have very high Q. This is because small steps in frequency
can cause large jumps in voltage and current which gives simulators
With the circuit shown, it looks like the crystal will
be inductive at resonance, and will resonate with the two series caps.
I would start by calculating an inductor that will resonate with caps,
and see if simulator converges. Modify inductor to get desired frequency.
Then insert series (Rm) with inductor, and see circuit has enough loop
gain to sustain oscillation. You may need to change ratio of caps to
improve margin. At this point, it will be likely your XO will at least
- Mark -