Problem in getting Noise Figure in ADS

[vickkey20]

I am designing the WLAN 802.11a receiver. I have simulated the individual blocks LNA,Mixer and several filters. I have been also simulated using ADS templates which are available in Design guides, where i have been replaced the inbuilt receiver with my receiver architecture.

The overall NF of the Direct Conversion Rx should be 6 dB max, but iam getting 12 dB overall.
My individual NFs are
upto mixer input 4dB
after mixer output 12.4 dB
After filter output 12.65 dB


Can anybody pls suggest me how to reduce the noise figure?

 

[khouly]

what is mixer NF ?
is it as the required specification ?

khouly

 

[mbyoussef]

Also what is the LNA gain?
How do you measure the NF of the separate blocks?

 

[vickkey20]

mixer NF is around 18 dB but it should be less than 10dB but i have still used because the gain of the LNA is higher for me.

Accordin to Frii's eq.
Rx NF=NF of LNA+(Mix. NF/gain of LNA).

I got gain of LNA(30 dB) more than required 20 dB.

I have calculated the NFs at each stage using ADS templates which are available in the Design guides.

I have replaced the inbuilt simulated Rx with my design.

so pls can u suggest me wat is the problem?

 

[khouly]

try to inset a filter just after the LNA , and check the NF now

also try to verify ur system on block diagram level "i man behavioral model

khouly

 

[mbyoussef]

Correction to your Friis equation: F = F_LNA + (F_Mixer - 1)/G_LNA

Where F is noise factor (ratio) and G is available power gain.

So is your 30dB available power gain? Do you have matching at every port?
Also your higher than required gain will improve your NF but will reduce your IIP

 

[vickkey20]

I have already inserted a channel selection filter before LNA.
Along with this filter i was getting those figures.................
I have also checked the matching at every point but it didn't helped me much................

Moreover i have one more doubt can u pls clear me................

can i use cascaded LNA's in the receiver................

 

[khouly]

yeah can cascade LNA's , but u need to check the nonlinear behavious of both LNA

can u attach ur project , so we can check it

khouly

 

[vickkey20]

Here iam attaching my project details
can u see and suggest me..............

 

[M.B.]

Hello,

This Document can help you in your simulation.

Good Work.