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ADS or MWO: RF amplifier simulation

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atlantis7

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ads amplifier

Hi

I'm looking for some help with simulating a mosfet rf power amp with either Agilent ADS or Microwave Office. I'm an absolute beginner and just can't find enough information about how to tackle exactly this task.

What I want is to simulate the design I already have to see things like output power depending on input power and gate voltage, whether the input and output impedance matching networks are correct or not, view the output spectrum to see if the lowpass filters work correctly and probably some more things.

From the mosfet I use I have an S2P file but no Spice model.

Can anybody please help with this or link to a document somewhere that descibes it?

Regards
Martin
 

a d s amplifier

If you have only S2P model (small signal S-parameters) you cannot do the task.
 

ads amplifiers

To get the measurements you are looking for, output power and output spectum etc., you would be best using Harmonic Balance simulations. For that though you certainly need a different model for the mosfet typically a Spice model. As vfone says an s-parameter model will never work for what you want.
 

microwave office power amplifier

Thank you for the answers! This probably explains why it didn't work out, but I just didn't know as a beginner.

Is there any realistic way to build the nonlinear model of the mosfet used? It is a Mitsubishi RD15HVF1 and unfortunately such a model is nowhere to be found.

Is there any useful thing that can be done with the linear (s-parameter) model? I have drawn the schematic in AWR with the mosfet represented by the s-parameter file and playing around with what I have can only help me learn to use the software.

Thank you!

Regards
Martin
 

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If it's a High power Amp you should get the Impedance vs. Freq from the
IC maker. Conjugate Match your circuit to the Impedance and you will get better
performance. The S-Parameters are more for small signals and it's hard to
make models to simulate AMP's as they reach higher powers.
 

class c power amplifier mwo

Hello Martin,

With S-parameter file you can do Small Signal analysis,
such as S-parameters, S11, S22, S21, etc,
Input/output impedance, Gain, NF, Stability of the device based on the meared data at perticular bisa conditions...
https://www.rfcafe.com/references/a...sign-of-RF-Microwave-Amplifiers-copyright.pdf
You can design PA using S-parameters, the procedure & a article is appended below...
First-Time-Right Design Of RF/Microwave Class A Power Amplifiers UsingOnly S-Parameters

other usefull documents on PA design documents using MWO...
www.rfpoweramp.com/papers/rfpa_mwo.pdf
www.polyfet.com/HFE0503_Leong.pdf

But if you have the Spice or nonlinear model you can completely design the PA in AWR MWO...

There are Nonlinear models for Mitsubishi devices for using with MWO from Modelithics
**broken link removed**


---manju---
 

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Hi Manju

Thank you for this document which shows an example of pa-designing with only s-parameters. Unfortunately I don't have Ampsa MultiMatch... Of course I would like to design with a non-linear model, but apart from those from Modelithics (which are not the ones I need) no Mitsubishi FETs seem to have been modelled.

The reason for using this mosfet is the low price and the unconventional but practical TO-220 case, similar Polyfet devices in the lower price range are more than twice as expensive and are in an SO08 (IC) case which is much more difficult to cool.

Kind regards

Martin
 

schematics amplifier rd15hvf1

i think , u will need to use the S2P files , and do Class A amplifier , and ten uwill optimze ur circuit by try and error ,which is the hard way.

Khouly
 

rf simulation amplifier software

Can you share the details like the application , frequency range, selection of substrate, housing requirement etc.
If you do the design using S2P then the design may not validate for near saturated power
 

ads or mwo

Hi

In the meantime I have drawn the amp circuit you find below.

I need am amp which works on both 145 and 435 MHz for ham radio use, the range in between is unused. The shown circuit shows a gain (S21) which is not too bad when I simulate it in MWO, even though I changed most values to actually available values.

Now how do I go about adding VDD and VGG, and can I take their influence into account in the simulation?

I think that there should be a series capacitor in the interstage matching network which serves as a dc blocking capacitor at the same time, am I right? But as I used tools to synthesize the matching network I have no idea how to change it accordingly. Zmatch could be used to calculate another matching network, but I only know the Zin of the second mosfet but not the Zout of the first, therefore this doesn't work.

Any help appreciated... Thanks!

Kind regards

Martin
 

ads different class amplifier

the data sheet (bias of the) transistor tell you the required voltages and design the self bias circuit to meet the biasing.
Now add this matching circuitry given above. but it is noticed that the inter stage matching is done by using resistor. Try to avoid it
 

linear simulator rf microwave

Ok, I already have some bias circuitry in mind, but I didn't know if I can just add this to the circuit and rerun the simulation to see if it works. If you say yes I try it asap.

Regarding the resistor, this was added by the synthesis software, and I think it's meant to stabilize the amp. I will try to come up with another circuit without it.

Thanks!
 

using s-parameters to calculate matching networks

Hello Martin,

The device model you are using already biased & measured s-parameters & hence their is no need of BIas circuit for the simulation...
(You need to have NL model to see the effect)

Only if you want to lay down the layout of the same ckt then you need to use the
bias elements in the layout editor...

Their is a test ckt in the datsheet that shows the bias, matching network for this device...see the picture...


---manju---
 

mwo awr two stage amplifier design

Ok, this means that the linear simulation calculates with the best possible conditions, right? So that when I build the circuit the result will probably be much worse.

The example circuits in the datasheets (also for the RD15 mosfet) do not really match the intended purpose of the transistors for mobile communications, the PCBs simply get too big if you build them with all the microstrips. Probably it is possible to convert the examples to to models without microstrips, but then I don't know how to do it.

Regards
Martin
 

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