Re: s parameter from DC
jaya000 said:
XXARGS
Thanks for ur reply!
The pages r from "J.F.White High Frequency Techniques - An Introduction to RF and Microwave" book.
Here i want to discuss more about measuring real s parameters.
I am saying real means like real car performance in the field & in ideal conditions, it differs. Then why not test S parameter in real conditions upto applications of 300Mhz or more.
To make good simulations you want smallest piece you can get from manufactory - ie ideal world - chip only, after this model of bonding, package etc. - every item outside chip represent lumped/transsmisions component and have big influence of trasistors performents outside package ie. extra inductance, capasitance etc. - special in high frequency.
in real life you can only get S-parameter for whole transtor with package in special manuafactured test fixture, advanced wide band range DC-bias network and lot of calibration to deembedd all outside infuence best as possible and only measure transistor itself without so much error.
this work need highly skilled measure engineer and take lot of time - and if high power circurit, scary ie. very easy to burning costly VNA for slightiest small misstake - most RF-power designes make self testfixture and measure itself on samples - experieced designers never trust manuafuctures data and many time also miss lot of importent information from manuafactory (for example reference planes place in measurement of S-parameters) or S-Parameter is a poor quality (mostly case...) or not take up measurement in different currents or tempeperature range.
Real condition testing means make the real sample good quality factory made PCB with actual biasing components & fit input output 50 or 75 ohm connectors as required by VNA. Then u can make different biasings as required and hv S parameters.
Many time can you buy manuafctorys reference fixture (and in old time often describe in data sheet/book so you can make one itself) but needs now close contact with manuafctorys engineers and development process with feedback in cooperation - this support is not easy to get if you work for small company and low volume customer...
many of days manuafactcorys have not longer own skilled measure group to make good public engineering data for customer - now in most case maked from consult or external companys - often in close cooperation to big EDA-companys as agilent/MWO/ansoft etc. and for this companys purpose (ie. you needs pay for model now in this companys development platform)
Can someone put some light into my thinking. I am actually as newbie to this field. hence looking for guidance from RF Gurus here.
Im also newbie - after around eigth years of RF-working in different levels
In most case, get a VNA and spectrum analyzer with tracking generator and practice many many hours in exprimentation on labb togheter with simulators... difference between experienced RF-engineer and newbie is a how many thousand hours you spend in lab and make fixtures, make filters, make couples, make calibrations, make misstake, burning components and some case burning instrument for €4000 in repair cost... books, theory, S-parameters and simulators is only a guide for your work and learning...