X-band 7.5-8.5GHz downconverter

[SNR]

Hello!
I the fan of meteorology. I wish to make the converter (LNB) for reception satellites оn 7,5-8,5 GHz.
The first step - calculating LNA.
I will use the transistor NE4210s01 (marking "L") in 2 stages.
How to calculate microstrip line and stubes for matching minimum noise ?

Please help me initial design.


my PCB:
NELTEC e=2.45 tgd=0.0016 h=0.787mm, Сopper 2 sides, t=0.035mm .

works program ADS2009, MWO2008.


More thanks!
Oleg

 

[Abhishekabs]

You have ADS.
So use ADS line calculator for microstrip
or use following link
http://mcalc.sourceforge.net/

& regarding matching you need to use smith chart for matching.
or use tuning mechanism in ADS, so tune the length till you get proper response.

Added after 3 minutes:

Remember your first stage decides the NF of the system, so at the input you need to play a little bit.
You may need to compramise for S11 if you want very good NF.

Refer Book by Gonzalez "microwave transistor amplifiers"

 

[vfone]

Here is an example of an 8.7GHz LNA using GaAs FETs.

For your case have to tune (using MWO or ADS) Z1 to Z13 transmission lines, to get the best performances in terms of gain, stability, and noise.

The bias lines Z7, Z8, Z9, and Z10 are quarter-wave transmission lines.

Z11, Z12, Z13, Z14 could be replaced by radial stubs.

 

[SNR]

Thanks all for answer!
I started calculating 1 transistor. Transistor Ne4210S01 not stable in 7.5-8.5GHz,
K<1.
For stable i added resistors 5,1 Ohm

After added 5.1 Ohm simulating in ADS2009 show K>1 for this band.

For condition of the minimum noise, on frequency 8GHz input
Zs=42,942+J52,701 ,
output Zl=42,692+J26,080
NFmin=0.399 db, gain =14.034 db

Next in diagrmam Smith calculating lumped elements for matching.
Simulating In MWO2008.
Refer to attached file LNA8GHz_1stag_lumped.rar

For microstrip and stubes matching I have got the values:
In attached LNA8GHz_1stag_microstr.rar

Now request to all knowing, check please all my calculations.
And as better stabilize the transistor, resistor in source, or inductance in drain?

Thank you!

Oleg,
Kiev Ukraine