design Rf circuit in ADS problem

[linuscomex]

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.

 

[volker@muehlhaus]

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

 

[BigBoss]

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.

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..

 

[linuscomex]

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?

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

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

 

[volker@muehlhaus]

all transmission line has an impedance in a specific frequency that effect on all of the circuit.

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

how design w,l of line?

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.

 

[linuscomex]

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.

 

[volker@muehlhaus]

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!