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quasi tem-mode
The TEM mode can be found whenever there are two conductors in only 1
medium. But for the case of microstrip lines, the wave is not completely confined in the dielectric, a portion of the wave propagates in the free space, as a result a longitudenal component of th field can be...
Re: LNA stability
for springf2000, how do u automatically check the stability of the LNA using @ds.
i designed an LNA and i doubt that it oscillates at 2 GHz, how can i be sure of that?!
THANKS IN ADVANCE.
If the input reflection coefficient of a 2 port network is greater than 1, is that condition enough for me to say that the network is oscillatory or i have to check another condition like barkhausen condition to be sure that oscillations occurs ?!
Here is the situation....when i designed an LNA operating at 11.5 GHz, i found it unstable at 2 GHz, so when i tried to put a parrallel 50 ohm resistor at the gate terminal with an RFC, i expected the noise figure to degrade so much, but surprisingly, it was the same, all the difference is that...
I want to know the whole specifications of the 2 stages LNA used in the universal LNB.. All i know that the 2 stages offer about 22 to 25 dB gain, the NF of the first stage is 0.5 dB while the second one is 0.7 dB... but what about th 1-dB compression point and the IP3... does anyone have any...
i have designed 2 seperate LNA circuits, each has its own input and output matching networks, so that each circuit has its own gain and noise figure, and the 2 circuits are matched to a 50 ohm line in the input and output.
But now i want to cascade them, so can i directly do that or i have to...
filter before lna
I read in some papper that for a receiver, if a band pass filter is inserted between an antenna and an LNA, it will degrade the noise performance of that LNA.
Why is that?! ........ is there any physical explanation for that?
Thanks
s2p files for different bias
i am designing an LNA using the S2P file of the transistor @ certain gain and noise figure...but when i replaced that nonlinear model of the transistor instead of the s2p file..the whole S parameters of the transistor were changed leading to the change of the gain...
i need a famous topolgy for designing an active bias network for an LNA operating at 11.5 Ghz in an LNB ..
i found a one in Gonzales book but i need a good application note about this topology...
Another question....will the noise figure be degraded so much after biasing the transistor with this...
when i try to draw the stabilty circles for my amplifier,all of the circles in the frequeny range lie intirely inside the smith chart..this means that my amplifier is potentially unstable while i am soo sure that the amplier is unconditionaly stable and i cheked that by calculating the K...
i think that the meaning of gain here does'nt mean an amplification of ur signal...it just means that it is a gain with respect to the loss we will have in case of mismatching...if u are matching for a certain load we u will have a certain power derlivered to that load..but if it's not...
matching an LNA
i have a thought in my mind and if i am wrong i need someone to correct it for me..
i know that matching assures that there no reflections back to the source while conjugate matching assures the max. power transfere which we need in LNA to obtain max. gain. but conjugate...
Re: quarterwave tl
i think that the quarter wave transformer or quarter wave T.L is only used in matcing impedances...that if we want to match a tl of z0 to another on of z2 we have to put a quarter wave t.l inbetween which have an impedance of
z1=sqrt(z0*z2)..
u have to think of it from...
I realy have problems in some issues in the matcing networks and matching impedances..
suppose that i have a transmision line of impedance Z1 on the left hand side and i want to match it to T.L of Z2 on the R.H.S so i place a matching network inbetween to avoid any reflections back on the Z1...
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