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Amplifier Matching problem!!!

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ahmad_abdulghany

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I was trying to match the amplifier shown below, but after matching, S11 still large!!!
I used Smith Chart utility in ADS to match.. and you will find also its results...
Same problem when Auto matching is made!! with exactly same resuls...

Where's the problem?
Can it be due to the blocking capacitor somehow?

Any comment? :(
Thanks in advance,
Ahmad,
 

Al7amdulillaah :)

I found the problem ...
I was reading Zout and matching input to its value :D

check Results after correcting it to zin(S11,PortZ1) below

My question now is, my main aim was to minimize noise figure by matching to Zopt .. when i did, S11 became -2dB!!! with NF=0.55, the current results were obtained with matching to Zin (not Zopt) and it gave NF=1.00 .. is it enough for an LNA first stage??

Can i cascade another GAIN stage and maintain NF not to increase too much?!

Thanks
Ahmad,
 

I have another question, Can someone give me effecient mixer circuit with discrete BJT transistors to generate IF of 10.7MHz of RF signal of about 100MHz?

What's better, to build the LO stand alone? or self excited mixer with LO built in?

If mixer DG in ADS will help me in such design, then please anyone send tutorial for it..

Any comments or addins will be appreciated...
Thanks alot in advance,
Ahmad,
 

AA,

Regarding the matching problem, did you try to use simulataneous noise and power match? ( using two inductors ).

Regarding the mixer, I think ( not sure ) that 1496 can operate at 100MHz +

Best Luck isA
 
Jazakom allaah khayran for your reply,
For simultieous matching, i don't know about it, if you can clarify more..
For SC1496, i used it, and i know that it's assumed (as in the datasheet) to work on 100MHz, but it didnt' :( ... much lower than it to operate !!!
so, i thought to build DISCRETE mixer..

Thanks alot for help,
And wating for more :D
Ahmad,
 

Simulatneous noise and power matching is done by using two inductors, one in the emitter and another in the base. The one in the emitter gives a real part = gm*Le/Cpi and an imaginary part that can be tuned out by the L in the base. just search on "simulatneous noise and power matching". I am also not quite sure it can be used for discrete LNAs but I think it can be used.

( Jazana we eyakom isA )
 
By the way,how can i download ADS.It seems usefull?

LT
 

If you add a microstrip line in you ADS circuit,YOU wll find that the smith match method is unright.
 

In you design project , the real PCB layout ,you need to consider the length of the microstrip line , but in your circuit you didn't consider the effect of the microstrip, if you don't consider the effect of the microstrip ,when you test the real design PCB you will find that the test result is beyond the results of your ADS simulation.so when you make a design you should add the microstrip line to simulate and network match!

Added after 3 minutes:

the microstrip
 

where can i dowload the ads!
best regards
 

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