AWR Microwave Office Elements

[Fahed]

Hi, i apologize if this is not the correct place to post this.

I am asked to simulate a VCO on Microwave Office. The exact schematic is this one:

Now the thing is, i am pretty much new to this program and i have no idea where to get the diode SMV1232 and the two transistors BF244C and BFR91A (Q1 and Q2) from. I tried searching in the program itself but nothing. Is there something i'm missing?

Thank you very much in advance

 

[BigBoss]

Those BJT components are obsolote and AWR library does not include them anymore.
You have to find SPICE models and Import them manually into AWR. SMV1232 Varicap is still available but SPICE model should be entered manually by drawing equivalent circuit.
If you're new to this software, don't start to simulate a VCO, it's really tough and needs to know some tricks and shortcuts. I do not recommend you to start from this.
Start simpler circuits to understand HB technique and some basic circuits. Look at included examples in it.

 

[Fahed]

Thank you for your reply BigBoss, unfortunately i do not have the luxury to not do this since it is a project assigned to us in an RF course i am taking.
I tried to import BFR91A SPICE.prm but i could not figure how to exactly work with it in AWR. Any guide would be helpful.
Also one more question, there are components inside AWR like SJFET and VRCTR. Would those work for this design?

 

[BigBoss]

BFR91A is still in AWR's Library, good news.

But I couldn't find SPICE model of BF244C.

 

[Fahed]

BFR91A is still in AWR's Library, good news.
View attachment 182516
But I couldn't find SPICE model of BF244C.

Oh Thanks! I found it. Regarding BF244C, can't we use another alternative?

Also excuse my ignorance but what is exactly V_varicap in the schematic and how do i do it in AWR? I tried the varactor diode but i don't know where do i exactly specify the voltage range and how to control it.

 

[D.A.(Tony)Stewart]

For the Nch JFET look around for all available, maybe it has some like
and ditto for Varicap BF244C
2N5486

 

[Fahed]

For the Nch JFET look around for all available, maybe it has some like
and ditto for Varicap BF244C
2N5486

Thanks for your reply.

I couldn't find the one you are referring to. Also what is ditto?

 

[BigBoss]

Oh Thanks! I found it. Regarding BF244C, can't we use another alternative?

Also excuse my ignorance but what is exactly V_varicap in the schematic and how do i do it in AWR? I tried the varactor diode but i don't know where do i exactly specify the voltage range and how to control it.

You have to enter manually SPICE parameters of the Varicap Diode with parasitic elements. You will have to draw a sub-circuit with them.

https://www.skyworksinc.com/-/media/SkyWorks/Documents/Products/101-200/SMV123x_Series_200058AA.pdf

 

[Fahed]

You have to enter manually SPICE parameters of the Varicap Diode with parasitic elements. You will have to draw a sub-circuit with them.

https://www.skyworksinc.com/-/media/SkyWorks/Documents/Products/101-200/SMV123x_Series_200058AA.pdf

View attachment 182517

This honestly sounds very complicated to do in the 6 days deadline our professor set with a software we are unfamiliar with. But is there any useful guides on how to manually enter parameters for elements?

 

[D.A.(Tony)Stewart]

For the Nch JFET look around for all available, maybe it has some like 2N5486


For the Varicap SMV1232 substitution your job requires reading datasheets and matching relevant specs. which in this case is the nominal C at 0V where all diodes have max. C and the nominal C at 12V where C is reduced then the ratio C(0V)/C(12V) = 5.6 with the fixed series C = 2.2 pF in parallel with 22+22pF controls the mean and spread of f by the resonant equation.

--- Updated Apr 26, 2023 ---

Then you need to learn what how Varicaps work and why better UHF specs and much higher prices $$ occur with GaAs or Gallium Arsenic and for this application maybe not use them.
This gets rather challenging to find exact substitutes but one might be https://www.mouser.ca/datasheet/2/268/mchp_s_a0011532491_1-2275113.pdf the MPV2100 which should be in that Library.

It's easy to put in model numbers, but hard to find parts that match them in stock that don't cost $25. So design is an iterative process for varicap diodes.

 

[Fahed]

For the Nch JFET look around for all available, maybe it has some like 2N5486


For the Varicap SMV1232 substitution your job requires reading datasheets and matching relevant specs. which in this case is the nominal C at 0V where all diodes have max. C and the nominal C at 12V where C is reduced then the ratio C(0V)/C(12V) = 5.6 with the fixed series C = 2.2 pF in parallel with 22+22pF controls the mean and spread of f by the resonant equation.

--- Updated Apr 26, 2023 ---

Then you need to learn what how Varicaps work and why better UHF specs and much higher prices $$ occur with GaAs or Gallium Arsenic and for this application maybe not use them.
This gets rather challenging to find exact substitutes but one might be https://www.mouser.ca/datasheet/2/268/mchp_s_a0011532491_1-2275113.pdf the MPV2100 which should be in that Library.

It's easy to put in model numbers, but hard to find parts that match them in stock that don't cost $25. So design is an iterative process for varicap diodes.

I see, thank you very much

 

[BigBoss]

This honestly sounds very complicated to do in the 6 days deadline our professor set with a software we are unfamiliar with. But is there any useful guides on how to manually enter parameters for elements?

If you have 6 days and you do still not know how to enter device parameters manually, forget about this project buddy. It's too complicated for you. I have told you before that this is an oscillator simulation and it's really very troublesome.
Couldn't your professor find a simpler entry level project for you ???

 

[Fahed]

If you have 6 days and you do still not know how to enter device parameters manually, forget about this project buddy. It's too complicated for you. I have told you before that this is an oscillator simulation and it's really very troublesome.
Couldn't your professor find a simpler entry level project for you ???

I actually did not see the third screenshot you have inserted, so all what i had was empty fields with no button to add parameters but now i get it. But yes overall its still complicated and its fair to say i am not the only one having troubles with it. All of our class is.
And no idea why he chose it, we've done VCO simulation few years ago (Not on RF) but it was on Simulink and it was simple. But this AWR program we have absolutely zero experience in and we only had one brief tutorial session on it and unfortunately learning resources about it are not of great availability.
Thanks for your help

 

[vfone]

Usually I don't do people homework, but I agree, there is not much time to learn a program as AWR, especially to add simple components to its #&$@ library.
I attach the simulation done in LTspice, at least you can understand how the circuit is working.
Also I attach the Spice models for JFET, BJT, and Varactor diode used in the simulation. In LTspice they are very easy to add to the library.

For JFET open with LTspice the file C:\Users\"your name"\AppData\Local\LTspice\lib\cmp\standard.jft and insert the model there.
For BJT open with LTspice the file C:\Users\"your name"\AppData\Local\LTspice\lib\cmp\standard.bjt and insert the model there.
For Varicap diode open with LTspice the file C:\Users\"your name"\AppData\Local\LTspice\lib\cmp\standard.dio and insert the model there.

Save each file after inserting the model, and restart LTspice.

 

[Fahed]

Usually I don't do people homework, but I agree, there is not much time to learn a program as AWR, especially to add simple components to its #&$@ library.
I attach the simulation done in LTspice, at least you can understand how the circuit is working.
Also I attach the Spice models for JFET, BJT, and Varactor diode used in the simulation. In LTspice they are very easy to add to the library.

For JFET open with LTspice the file C:\Users\"your name"\AppData\Local\LTspice\lib\cmp\standard.jft and insert the model there.
For BJT open with LTspice the file C:\Users\"your name"\AppData\Local\LTspice\lib\cmp\standard.bjt and insert the model there.
For Varicap diode open with LTspice the file C:\Users\"your name"\AppData\Local\LTspice\lib\cmp\standard.dio and insert the model there.

Save each file after inserting the model, and restart LTspice.

Thank you very much.
However, our prof is insisting on us using AWR. I actually built the circuit on AWR and modelled the Varactor, tried almost the same BJT and JFET (BF245c and BFR91A) as well as multiple BJTs/JFETs but whatever i change or try i get the output voltage to be very low (1e-17). I thought maybe i did something wrong but then found out all of my colleagues who have different VCO circuits/designs are facing the exact same problem. Maybe it is just us being unfamiliar with the software, but yeah thanks a lot for your help maybe we will try to pursue him to use a spice software instead.
I appreciate it

 

[BigBoss]

I have checked this oscillator and my conclusion is not so good in ADS.
It oscillates with ideal components without varactor diode that is replaced with a simple ideal capacitor.
Unfortunately, it stops to oscillate with varactor due to low Q factor and it's an oscillator that works with difficulties.
Practical case might of course be different but at first glance it's not very consistant.
Equivalent SPICE model of SMV1232 is not absolutely consistant. Skyworks gives different models in two datasheets. I have used Infineon varactor.

 

[vfone]

The oscillator works fine, but due to high feedback gain (compared to other oscillators), needs tuning of the feedback resistor (the one that goes to the capacitive divider).

Using two varicaps in the VCO will make the simulation running better:

https://www.mikrocontroller.net/attachment/459356/goral.pdf