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capacitance in ads
Assuming you do not have access to the spice model otherwise things are easier.
The diode is in reverse since any diode (especially varactors) exhibit the higher capacitance range in reverse bias. Forward bias your capacitance is tinny.
Assuming your diode is a black box...
eliminate oscillation
I said to kill the gain at the unwanted frequency as a suggestion, but that does not apply in your application. It will have, if the undesired oscillation frequency, was further away from your operational frequency and you still had gain. But in your case your gain is in...
eliminate amplifier oscillation
check your bias tees decoupling...a simple test is to place your finger between the DC line and ground where your decoupling caps in the bias tee are, (press a bit hard) see if that removes the oscillation. If thats the case probably your bias tees dont work...
lump elements hybrid couplers
You can build as other people said a Lump element hybrid, at your frequency lump components will work fine.
I attach a pdf that has the equations and circuit diagram for your hybrid. Make sure when u build it u put everything symmetrical and as close as...
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...
The questionmark in the picture is at the Impedances, basically what says there, is what kind of impedance you going to present at the input output at the harmonic frequencies, that is usually 50Ω. At your fundamental frequency the example has R=10Ω, that means probably he has used a matching...
flicker noise resistor
Yes they do,
Here few papers that may be of help.
[1] S.L.Jang, "A model of I/f noise in polysilicon resistors", Solid-State Electronics, Vo1.33, No.9, pp.1155-1162, 1990.
[2]O.Roux dit Buisson and G. Monn, "Flicker Noise Characterization of Polysilicon Resistors in...
wilkinson combiner theory
You don't have any loss when you combine a signal in a Wilkinson divider (except the losses from the line attenuation). If u don't want to use a Wilkinson you can use any other type of coupler to combine powers as Rat Race, 90deg Hybrid , Lange etc. All will do the...
rf choke
For the RF choke you can use a Bias tee in microstrip. A λ/4 High Impedance Line (usually 100Ohm) with a O/C radial stub at the end centered at your frequency of operation. For reference about Bias tees check the following site: However 1.2nH will be a very short line. Play in ADS and...
I am a bit late here, but I will like to comment a bit also.
I hope rosaeidi you have told your supervisor that -190dbc/Hz at 10kHz VCO is out of question except if you invent a new technology of transistors and resonators. And dont lose your time to make the impossible.
However in a DRO I...
That is a good starting point
**broken link removed**
As a rule of thumb I will like also to add
Your DC blocks I assume are the coupling capacitors, well at the frequency of your operation chose a capacitor that its Impedance Zc=1/jωC is really small (1ohm for example ), however make sure...
eqn in ads 2008
I suppose you tried the example project MMIC_OSc.prj and Varactor_test Schematic where it has that equation.
What he does there is for a certain frequency he varies the voltage on varactor and measures the impedance from the reflection coefficient and then calculates the C...
As far as I know ADS doesn't have full behavior models for microstrip SSB like the do for microstrip or strip line, that means you have to do primary your design using ADS momentum.
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