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.

Register Log in

Can 0.5dB S11 cause oscillation in an LNA design?

Status
Not open for further replies.
I

imado_60

Junior Member level 1
Junior Member level 1
Joined
Jun 10, 2009
Messages
19
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,281
Activity points
1,375
i am desingin an LNA at 500 MHz .. S11 is under zero for all frequencies except at 1.3 GHz it's 0.5 dB . Is there any risk of oscillation for this small value of S11 ???
 

s11 device

Hello,

You said you designed means simulated or fabricated a prototype!!!

The S11 can't be positive their may be some problem with the device model
parameter or file...

Yes, it is unstable (oscillations), plot the K or B1 stability factor plots or stability circle measurements on smith chart....
See more here **broken link removed**

Or verify the matching network & the device models...!
By the way what is your operating frequency range...!!!

---manju---
 

    I

    imado_60

    Points: 2
    Helpful Answer Positive Rating
how to use awr to simulate lna

i am simulating my LNA on ads , my operating frequency is from 300MHz to 800 MHz . 10x
 

Re: LNA S11

Hello,

I haven't used ADS, but their is a measurement...(I use AWR Microwave Office)
may be go through the tutorials or the following pdf...
https://www.sandiego.edu/~ekim/e194rfs01/ads_stability.pdf

In ADS there may be an icon for stability in S-Simulation, if it is not their you can write an equation to extract it from S-parameters
k = {1- |S11|**2 - |S22|**2 + |S11*S22 - S12*S21| **2} / {2*|S12*S21|}

See here...



---manju---
 

    I

    imado_60

    Points: 2
    Helpful Answer Positive Rating
Re: LNA S11

Hi

In ADS u have stabfact in simulation tools, use that for checking the stability
 

    I

    imado_60

    Points: 2
    Helpful Answer Positive Rating
Re: LNA S11

I was under the impression that when S11 (Input reflection coefficient )exceedes a magnitude of 1 then you possibly have an Oscillator.
 

Re: LNA S11

Its the stability factor which u should consider...
k>1 or mu>1 is the condition for stability ( No oscillations)
 

    I

    imado_60

    Points: 2
    Helpful Answer Positive Rating
Re: LNA S11

i agree with u.
|Г|>1,then the system is unstable

darcyrandall2004 said:
I was under the impression that when S11 (Input reflection coefficient )exceedes a magnitude of 1 then you possibly have an Oscillator.
Click to expand...
 

    I

    imado_60

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top