microwave oscillator tutorial
73 de Ulrich
Correction page 10 > Y21 Large signal calculation
page 17 > Equation
Please report errors or send questions ( within limits, please !)
Tutorial ? Are you sure ?
I have never seen a tutorial like this. Everthing is floating, where they come from, where they go ?
Fascinating. Care to comment on the two resonator approach? I have fiddled around with 2 resonators, but never felt confident enough to actually ship an oscillator with 2 pasive resonators, tightly coupled, in it. Was always worried one might drift off of the resonant frequency due to aging, contamination, etc, and give me a double humped resonance. ie. stop oscillating.
I have used two resonators where they were decoupled by the active device, such as a ceramic resonator on the base setting the frequency, and lumped element resonator in the emitter causing a phase slope in the negative resistance port--efectively multiplying the ceramic resonator's Q.
Rich
www.maguffinmicrowave.com
.This is part of a full paper,that why it may appears not easy to understand unless properly presented. The full paper will come soon in one of the IEEE journals.
The coupled printed resonators behave well, and we have shipped a few 10 000 oscillators like this .
Thanks for sharing with us this nice ideas.
Unfortunately sometimes shipping is not in concordance with reliability. I know a company that sold a million of handset PA?s, and almost all of them failed after an antenna replacement.
Regarding the aging of the resonators. Was happened in one of my old projects when I used two identical coupled resonators, and in time they starts to behave different.
Aging of resonators is like aging of humans. Is never the same.
One problem that IS for real is that sometimes the ceramic material has microcracks in it. If one resonator was microcracked, and the other was not, the microcracked one could absorb water vapor and cause some havoc. Still, it is a great electronic trick to get a higher effective Q in a resonator!
I remember a sample lot test being done on DRO pucks somewhere to find faulty ceramic batches. If the Q drops after humidity soaking, the lot is suspect.
Rich
www.maguffinmicrowave.com
Yes, the ceramic resonators make trouble, that is the reason why we uses multi layer buried resonators in a patented approach , optimized with a 3 D simulator , and other improvements as hinted in the power point presentation .
Is this really a tutorial?
Graphs sure are giving some information.
Which software you are using?
also transient simulation looks strange.
On page 14 you have said oscilaltor acting like mixer!
What if I call it modulator? this is good term than mixer.
I believe for GHz frequencies we go for HB simulation
Where are HB simulation results?
I belief mixer and modulators are interchangeable words. As CAD I have used Ansofts Serenade program, a modern HB program. However not everyone has S 25 000 available, and this approach allows the calculation from first principle to obtain useful noise results.
Yeah. The approch is good.
Few months back I saw one IEEE paper.
Where that fellow written his own algorithm/program/software for oscillaltor design.
It was preety good.
Also not every one has 50,000 S to purchase New agilent's VNA for X param measurement. :D :)
Most of the people depends on Vendor's S2P files or nonlinear model for simulation.
General comments on noise :
The early oscillator pioneers like Leeson, Driscoll, Healey III , Parker and others did their analysis based on linear assumptions, which do not get the same good results as available today. The modern methods require large signal parameters which Agilent now calls X parameters. Provided that the input parameters for the models are OK, the harmonic balance simulators can tackle this. I prefer measurements , using a network analyzer and then a set of analytic equations. The results for modern planar resonator based oscillators up to 20 GHz are much better then the conventional predictions without dealing with the conduction angle of the current and suppressing or even enhancing certain harmonics
This modern approach, heavily depending on non liner analysis and mathematics shows a further improvement, by reducing the AM to PM conversion, both modulation and conversion noise (close in and far out noises are different in their origin).
It applies both for crystal oscillators and printed resonators and other solutions. I will follow up with a series of IEEE publication and validations , but the curious readers may find the basic presentations useful.
The Design of Modern Microwave Oscillators for Wireless Applications, by Ulrich L. Rohde, Ajay K. Poddar, Georg B?ck, published by John Wiley & Sons, New York, NY, May, 2005, ISBN 0-471-72342-8.