varactor diode model in Vco design

[lkuzu]

varactor diode

I will use AWR to design a microwave oscillator. Question is how can I get s parameters of a varactor diode? I searched google but manufacturers don't give that information. Do we have to measure varactor's s parameters ourselves? Please help.

thanks

 

[franziac]

varactor diode model

voltage capacitance graph values must be inported. there is always such a graph that shows the relationship between the voltage and capacitance.you then must set a datafile including the values of voltage at the first line and capacitance at the second. for example :

15,12.5,10,7,5.6,3,2,0 ------------------> voltage values
0,2,3.15,5,6,8,10 -------------------------> capacitance values

 

[biff44]

varactor diode vco

You know, that is a darned good question. You can assume a model of a capacitor in parallel with a resistor, where the parallel resistor is given by Q = 2ΠfRpC. But the reality is that there are parasitics, especially if you are using a packaged varactor. You will quickly find that the parasitics and the Q are real limitations if you are trying to get a wide tuning range.

They probably do not provide the Sparameters because an S parameter measurement does not have a fine enough resolution to adequately show device Q. A varactor with a Q of 100 will behave very differently than a varactor with a Q of 500, yet the S11 will look very much alike (at the edge of the chart). A lumped model might provide a better prediction of circuit performance.

Rich

 

[sunn]

varactor vco

Hi IKUZU
please refer this link regarding varactor diode model in Vco design, althought it was related ADS but I believe it could be applied to AWR as well due to generic varactor lumped model

 

[Soben]

vco varactor

voltage Vs. capacitance graph is always at low frequency where parasitics don't have an effect. When you operate at high frequencies especially at the low Bias voltages the C of the Cap will be way off from the low frequency one. If you include the inductance of the package you will get better results. Most manufacturers at least Philips and MaCom Varicaps I have used do give that kind of info