design Rf circuit in ADS problem

hi.
one of the most important thing to design low noise amplifier is stability.there are a lot of methods for stabilized amplifier, for example, add the resistor to drain of HEMT transistor but I can't understand why use microstrip line to connect the resistor to an amplifier? and how design microstrip length?

for clearly see an image.

I think these small line lengths represent the SMD pad/component dimensions.

This is an equivalent distributed model of a layout and interconnections of an amplifier (?) that has been stabilized by a resistor and a capacitor.So, they are simply interconnections in order to simulate that amplifier more accurately.
W,L and substrate dimensions are given, you don't need anything else..

no this is a part of LNA that simulate resistor.
is transmision line for simulate behavior of pcb pad ? so how design w,l?

all transmission line has an impedance in a specific frequency that effect on all of the circuit. how design w,l of line?

When line length is very short compared to wavelength, impedance transformation equations give Zin = Zload for any value of Zline.

As written before: these line segments are not calculated for a specific line impedance. They describe the required pad & interconnect dimensions, so they depend on your SMD footprint size.

yes, but w,l of smd foot print Will affect on impedance , noise ,gain and .... of circuit.

That's why you include it in simulation, to include these parasitic effects. But size is fixed, as required by SMD layout & routing. Anyway, good luck with your design!

申明：网友回复良莠不齐，仅供参考。如需专业帮助，请学习易迪拓培训专家讲授的ADS视频培训课程。