Johnny 5

Could anyone please give me some help I'm doing my final year project and I am finding it extremely difficult. The following is a copy of my control sheet for said project.


Project Title: Design of an Amplifier for GPS Receiver

Project Objective: To design a narrowband amplifier for the GPS band based on the S-parameters of the transistor and with the aid of microwave circuit simulator.


Project Marking Guidelines:


Pass: Design a lumped element amplifier circuit for the specific gain and input and output VSWR, which includes proper matching and biasing networks.
Merit 2: Investigation of possible improvements in: bandwidth, gain, VSWR and stability.
Merit 1: Transition of the lumped element amplifier into the real element counterpart with the utilization of the off shelf components.
Distinction: Transition to the distributed element amplifier.



Equipment: PC and microwave circuit simulator – Microwave Office
Components (Non Standard): None


Anyhelp would be Hugely apptreciated.
Thanks in advance,
John.

JimB

OK,

What part of the project specification don't you understand?

JimB

__________________
Experience is directly proportional to the value of the equipment ruined.

Johnny 5

To be perfectly honest I don't understand the relationship between what is being asked for. If there was a way to put it in plain english and then maybe start from the start with what would need to be done, that would be fantastic. I have picked out a transistor which I think should be ok to use.

JimB

What transistor have you selected?
What was the basis for your selection?

JimB

__________________
Experience is directly proportional to the value of the equipment ruined.

Johnny 5

It had to have a high gain and a low noise figure and work in the frequency range of 1 to 5 GHz.
I selected the Agilent Technologies ATF-35143 in a surface mount plastic package.

JimB

OK, that seems a reasonable choice.
Have you seen the application note describing a 3Ghz (ish) amplifier?
Look here:
http://literature.agilent.com/litweb...988-5040EN.pdf

At a quick guess all you need to do is adapt that for the frequency of a GPS and you are half way there.

What next?

JimB

__________________
Experience is directly proportional to the value of the equipment ruined.

Johnny 5

I'm sorry but I'm lost and I don't understand. Also how do smith charts and matching networks tie in with this?

JimB

At this point I must ask, you are doing this as a university (?) final project.
Have you not done anything on:
RF amplifier design
Impedance matching
Transmission lines
during the course?

If not, it may be a bit late now.

If I were doing this project, the steps I would take are:

Find the frequency I need to amplify.
Select a suitable transistor.
Decide the source and load impedances.
Design the bias circuit.
Design input and output matching networks (tuned circuits?) which will pass my required frequency and match the load and source impedances to the transistor.
Build and test it.
If it does not work, find out why and repeat the steps required to make it work.

JimB

__________________
Experience is directly proportional to the value of the equipment ruined.

Johnny 5

Yes, I'm embarassed to admit, I am in college and while we have covered a small amount of material on transmission lines and on Impedance matching, we've done no RF Amp design!?!?
Thank you for your help, it is very much appreciated.

JimB

So how did you get stuck with a project like this?

At first sight it should be quick and easy, just a dozen components or so.
But to get a good performance from an RF amplifier at these frequencies is not trivial.

JimB

__________________
Experience is directly proportional to the value of the equipment ruined.

Johnny 5

That's something I've been asking myself and I have yet to come up with an answer. I've just spent the last hour and a half with my project supervisor and While it was helpful I still don't fully understand. Oh well thank you again for your time and patience.