Design of high power hybrid combiner

[Sarikas]

Hi,
I need to design a microstrip hybrid coupler (to be used as combiner) with power handling capacity of 160W. I have many doubts, namely:
1. how much power a conventional hybrid coupler can handle?
2. what kind of design can be used to achieve high power handling capacity?
3. how can we increase power handling capacity in a conventional hybrid coupler? Is that we need to increase the transmission line widths for that? If yes, how to decide the width for 160W ?

Please help.

 

[Joel-Tang]

My advice:

• 
  Calculate the power/heat dissipation in the isolation resistor.

• Determine if you want to design for fault conditions that direct more power to the terminating resistor.

• Consider the power handling of the transmission lines you are using.

• Consider the power dissipation in your chosen board substrate if you use one.

I do know that most high power termination resistors have parasitics you will need to tune for a better match.

I hope this helps.

Joel Richard

 

[Sarikas]

Hello Joel...

Thankx for the reply, it helped.

I am thinking of using a branch line coupler for power combining with the inputs as high as 100W. So, we can expect 200W at the output, right ?. I am using RO4350B substrate at 1.8425GHz freq. I tried using mwi software of roger. And it shows me to use the same 67mil width line for 50ohm at 200W also. Is that, a normal transmission line`s power handling capacity matters only at high freqs like some 5GHz ? and does`nt matters for my design ???

 

[Joel-Tang]

You are on the right track, but you might need to read up on basic transmission line theory to make sure you understand everything you are doing as with any RF Design, you will find yourself balancing multiple conflicting requirements. A transmission line retains its impedance over frequency.

Just make sure you design for more power capability than expected.
Skin effect plays an increasingly negative role in power handling capability at higher frequencies, but this should only affect the effectiveness of using thicker copper traces.

 

[shashy.br]

Srikas,

Use Rogers 6010.2 substrate with 25 mil thickness,

i have designed 4KW modules with this (pulsed with 2 % duty and 32uS pulse width)