role of certain elements in MACOM PCB

nsaspook

Joined Aug 27, 2009
13,406
Hello,given the macom amplifier shown below.i have two place which i am not sure about.
1. place marked as 1 in the photo looks like output pin but i am not sure why its needed?
2.in place marked 2 why there is a thick trace with a gap ?
Thanks.
https://cdn.macom.com/datasheets/CGHV1A250F.pdf


View attachment 317378
Look, read and think about what you see.

CGHV1A250F-AMP Evaluation Board Schematic Drawing
1 connector J4, voltage and the large wire loop current (clamp sensor) can be used for power sensing.

CGHV1A250F-AMP Evaluation Board Assembly Drawing
2 Trace for C18, a (looks like an option) power filter capacitor.
 

nsaspook

Joined Aug 27, 2009
13,406
Don't know for sure. Could be part of a distributed-element RF trap or filter element for the DC supply/bias lines.
1710185740919.png
https://en.wikipedia.org/wiki/Distributed-element_filter

Figure 7. Low-pass filters constructed from stubs.
Standard stubs on alternating sides of main line λ/4 apart.
Similar construction using butterfly stubs.
Various forms of stubs, respectively, doubled stubs in parallel, radial stub, butterfly stub (paralleled radial stubs), clover-leaf stub (triple paralleled radial stubs).
 
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Thread Starter

yef smith

Joined Aug 2, 2020
806
Helso Nsaspook, i think an RF noise trap means the structure is RF short.meansarc type stub becomes short at rf frequencies.
Open circuits with lambda/4 becomes short circuit..
but in the schematics are rectangles. near the arc.What do you thinkthey role are?

in the actual layout i cant see these rectangles shown in the schematics in the end.
Thanks.
1710193124407.png
1710192824227.png
 

nsaspook

Joined Aug 27, 2009
13,406
Helso Nsaspook, i think an RF noise trap means the structure is RF short.meansarc type stub becomes short at rf frequencies.
Open circuits with lambda/4 becomes short circuit..
but in the schematics are rectangles. near the arc.What do you thinkthey role are?

in the actual layout i cant see these rectangles shown in the schematics in the end.
Thanks.
View attachment 317413
View attachment 317412
Like I said, those are distributed LC elements. Their relative physical dimensions as the lengths, orientation and shaped traces are shown on the schematic as a relative mirror of what's is on the PCB.
 

Thread Starter

yef smith

Joined Aug 2, 2020
806
Hello Nsaspook , yes I understand it’s a very important point .
If we look at the schematics any block is a distributed inductor or capacitor .

suppose at the output :
What is the point of putting distributed transmission line after dc block ?
Thanks .
 

nsaspook

Joined Aug 27, 2009
13,406
Hello Nsaspook , yes I understand it’s a very important point .
If we look at the schematics any block is a distributed inductor or capacitor .

suppose at the output :
What is the point of putting distributed transmission line after dc block ?
Thanks .
Do you mean as opposed to before the DC block?
That's just normal circuit design to usually isolate DC drive and components from RF matching or tuning elements for testing or probing safety.
 

Thread Starter

yef smith

Joined Aug 2, 2020
806
Hello Nsaspook,as you can see below they start from very wide as shown in the photo below as "1" however when we reach the
capacitor the power rail gets much thinner as shown in "2".
What is the logic in doing that?
Thanks.
1710312978145.png
 

nsaspook

Joined Aug 27, 2009
13,406
Hello Nsaspook,as you can see below they start from very wide as shown in the photo below as "1" however when we reach the
capacitor the power rail gets much thinner as shown in "2".
What is the logic in doing that?
Thanks.
View attachment 317520
More interesting is what do you think the logic is for 2 because I see the same basic thinner structure on the input side. 1 is just wide trace/copper for low resistance in the DC power filter section.
 

Thread Starter

yef smith

Joined Aug 2, 2020
806
Hello Nsaspook,i think that there are places where lines are 50 ohms and lambda/4 .
given the photo below could you please say where are the 50 ohm lines an where the length sould be lambda/4?
Thanks.
1710361627545.png
 
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