Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

I need help to get the desired S-parameter for low noise amplifier

Status
Not open for further replies.

btv_murthy

Full Member level 3
Full Member level 3
Joined
Nov 29, 2011
Messages
159
Helped
9
Reputation
18
Reaction score
9
Trophy points
1,298
Location
BANGALORE
www.edaboard.com
Activity points
2,719
Dear Sir,
I designed the biasing for the low noise amplifier at Vds=3v, Ids=20mA, need to get the desired s- parameter as follows

f(GHz) s11(dB) S21(dB) S12(dB) S22(dB)
1.3 -1.83312 17.944 -23.083 -10.637

But I am obtaining the following S-parameter values

f(GHz) s11(dB) s21(dB) s12(dB) s22(dB)
1.3 -0.012809 11.721 -86.024 -2.1229

Can anybody help me to get the desired s-parameter low noise amplifier, Here with I am attaching the schematic of the lna
 

Attachments

  • lna_biasing.jpg
    lna_biasing.jpg
    30.9 KB · Views: 84

Dear Sir,
I designed the biasing for the low noise amplifier at Vds=3v, Ids=20mA, need to get the desired s- parameter as follows

f(GHz) s11(dB) S21(dB) S12(dB) S22(dB)
1.3 -1.83312 17.944 -23.083 -10.637

But I am obtaining the following S-parameter values

f(GHz) s11(dB) s21(dB) s12(dB) s22(dB)
1.3 -0.012809 11.721 -86.024 -2.1229

Can anybody help me to get the desired s-parameter low noise amplifier, Here with I am attaching the schematic of the lna

Your s11 measurement, which is a measure of the amount of energy reflected back from your input is very high. That means almost no power at 1.3 GHz is being transmitted into the amplifier. The same thing is happening with your output port, though not as badly.

The most likely design reason for the poor return loss performance is an impedance mismatch at the port. Let's assume you've intended to design your amplifier for 50 ohms. Either your cable you're using to measure your s parameters is not 50 ohms, or your amplifier ports are not 50 ohms.

Assuming your design is the issue, use your network analyzer to measure the port impedance. Make the necessary changes to your design to get the ports to match better to 50 ohms.

When you have designed a good match, your s11 will be greatly reduced, and you will see that as an increased value of s21 as well--assuming you've also improved your output port.
 

Dear Sir,
The S11 is company defined high reflected energy ,that is -1.83322. I obtained for my design is -0.01289 of the gain 11.721. what component I have to use for the input and output matching and what are the design values.
 

Dear Sir,
The S11 is company defined high reflected energy ,that is -1.83322. I obtained for my design is -0.01289 of the gain 11.721. what component I have to use for the input and output matching and what are the design values.
For the design procedure you can refer any tutorial from INTERNET. But by observing your S-parameters i can say that the input and the output ports are not matched. You can verify this by checking at what frequency does the input resonates with the values of those Inductors.
You could go for inductors because you haven't used any inductors in the input side so that remains Unmatched!!!!
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top