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

[SOLVED] Figure of Merit for RF frontend with AGC?

Status
Not open for further replies.
N

NBV83

Newbie level 2
Newbie level 2
Joined
Mar 11, 2011
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
Denmark
Activity points
1,297
Hi,

I'm looking for a figure of merit to be used for the design of a RF frontend with an AGC. Does anyone know how to compare these systems in terms of noise performance and dynamic range, as the AGC kinda complicates this.

I haven't been able to find this yet, in spite of reading through several articles, so I thought that I would try my luck hear at edaboard.

Any suggestions?

Thank you in advance.

/NBV83
 

Yes, AGC really complicate the RF system noise figure calculation, because the gain of each stage changes dynamically.
One thing is for sure. When the gain is lower, the noise figure is higher.
The easiest way for calculation is to make a system spread sheet (using the Friis cascaded stages equation) where to be able to vary the gain of stages and see the noise figure (of the system, or of each stage).
 
  • Like
Reactions: NBV83

    N

    NBV83

    Points: 2
    Helpful Answer Positive Rating
NBV83 said:
Hi,

I'm looking for a figure of merit to be used for the design of a RF frontend with an AGC. Does anyone know how to compare these systems in terms of noise performance and dynamic range, as the AGC kinda complicates this.

I haven't been able to find this yet, in spite of reading through several articles, so I thought that I would try my luck hear at edaboard.

Any suggestions?

Thank you in advance.

/NBV83
Click to expand...
Use all the common figure of merits (noise, gain, IP3), but you will need to do Best and worse case. Or make
graphs of each merit over the full range of the AGC. i.e. "Noise vs Attenuation of the AGC" etc...

I assume this is a specific application, and you need the AGC in the front end. And I would assume that
the performance is expected.
 
  • Like
Reactions: NBV83

    N

    NBV83

    Points: 2
    Helpful Answer Positive Rating
Any AGC makes the linear receiver chain a non-linear device. To answer your questions, you must calculate at least the two points for the lowest and highest signal input level.
For the best receiver noise, the AGC-controlled attenuator (or the variable-gain amplifier) is best located after the low-noise front-end stage. The AGC should rather compress receiver gain for higher-level input signals.
 
  • Like
Reactions: NBV83

    N

    NBV83

    Points: 2
    Helpful Answer Positive Rating
Thank you all for your answers.

I see your points, and it seems that I will have to make multiple specs for my receiver block, to encompass the performance across the dynamic range.

Partially I was hoping that there exeisted some fine way to incorporate the AGCs gain levels into a FoM, but I don't know how to do that while making the FoM to be useful. So I will do as you suggested.

Once again, thank you for the responses.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top