I will try to answer on some of
1. What value of inductance I should use with power
choke inductor, refer to application circuit?
The inductor value should give you a reactance of
several hundreds ohms (at least 300 ohms) in your lowest
frequency of operation. remember that as the frequency
increases, XL increases as well.
In addition, you
should choose the inductor such that its SRF
(Self-Resonance Frequency) would be at least twice higher
than your maximal frequency of operation in order to avoid
a capacitive reactance.
How I define output M.N.? refer to application circuit?
Usually for LNA, you define the output matching
network as one for conjugate match. This is because the
input matching for noise figure degrades the return loss
at the input and reduces the overall gain (mismatch), and
as a result you loose power.
If I do a simple output conjugate matching, should I
turn on LNA, if yes, is power choke a part of matching
You should design the output matching only after
your input mtaching network is fully designed and
connected to the LNA, because the input matching network
will affect your S22. The reason for that is that the
amplifier is not unilaterlal, i.e. there is a certain
feedback from the output to the input S12.
choke (power inductor as you named it) if properly chosen,
should slightly influcnece on the output mathcing network.
Actually, it isolates between the supply voltage to the
matching network. Usually from RF signal point of view, it
only slightly increases the gain.
So your output
matching newtok should be designed to the conjugate of the
modified S22 (With the influence of the input matching
You should turn on the LNA, in order to
measure the output power.
general, when designing matching networks, pay attention
to the stability of the amplifier.
It is very
important to check that your required reflection
coefficients are located within the stable region.
can perform stability simulation or calculate K (Rollet's
Factor). For unconditional stability K>1