RF and Microwave PCB Design - Part 5: Couplers

In this RF and Microwave PCB Design Series episode, Ben Jordan walks through the essential design steps for microstrip couplers most commonly found on microwave PCBs: The 90-degree Hybrid, the Rat-Race, and the Backward (directional) coupler.
References:
Microwaves 101 pages on Branchline Couplers: www.microwaves101.com/encyclo...
Microwaves 101 pages on Coupled Line Couplers: www.microwaves101.com/encyclo...
Previous episode, “Part 4 - Power Dividers”: • RF and Microwave PCB D...
Chapters:
00:00 Introduction to Hybrid Couplers.
08:16 Port 4 Isolation - how that works.
11:45 Applications of the 90-degree Hybrid.
16:28 Extending for broader bandwidth.
21:08 The Rat Race coupler.
28:18 Directional Coupler (Coupled-Line Coupler) Introduction
30:19 Coupling principles - Odd and Even mode impedance.
33:15 Directional Coupler Geometric Structure.
36:07 Directional Coupler Applications.
38:08 Example design walk-through at -6dB coupling.
50:30 Practical Limits of Coupler Dimensions on FR-4
51:24 Second example design at -12dB coupling.
59:19 Frequency Response of the Examples.
You can calculate impedance and dimensions using various free tools, or use the Layer Stack Manager in Altium Designer:
- QUCS (qucs.sf.net)
- AppCAD (www.broadcom.com/appcad)
- Saturn PCB Toolkit (saturnpcb.com/pcb_toolkit/)
Learn more at my.altium.com/learning/gettin...
Design PCBs with a Free Trial of Altium Designer Here: www.altium.com/yt/altium-acad...
Download CircuitMaker Here: www.altium.com/circuitmaker/d...
The Altium Academy is an online experience created to bring modern education to PCB Designers and Engineers all across the world. Here you can access a vast library of free training and educational content covering everything from basic design to advanced principles and step-by-step walkthroughs. Join industry legends as they share their career knowledge, review real-life design projects, or learn how to leverage one of Altium's leading design tools. No matter your level of experience, the Altium Academy can help you become a better Designer and Engineer!
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[@larseriksvendsen7412]

Very nice, love the practical design examples. Brings light to some of the black magic of RF.

[@abo-albraanj8273]

very nice and straight forward lecture I would recommend for any designer even with beginner level from theory to practical this people what need keep going :)

[@iniezlezyc]

Thanks a lot for the lectures Altium!

[@AltiumAcademy]

Most welcome!

[@novocaine212]

Why doesn't the same cancelling-out effect that occurs on P4 also occur on P2. In both cases, there are 2 paths from P1, one with λ/4 and one with 3λ/4. Is it because the direct route without 90° turns has significantly less energy loss from the cazse with 4 turns? Love the videos!

[@ulkie123]

Note that the lambda/4 lines of the quadrature hybrid have different line impedances. The lines between 1-2 and 3-4 have Z0/sqrt(2) impedance while the lines between 1-4 and 2-3 have Z0 impedance. Thus, P2 and P4 don't look the same seen from P1. The maths are explained in this video: kzbin.info/www/bejne/qKDcgalmZtWSmas&ab_channel=EMPossible

[@hubercats]

I have the same question as Anantha Dhruva. I.e., why are you NOT adding the contribution of the 3/4 lambda path (P1 to P4 to P3 to P2) to port 2? - Thanks! - Jim

[@sersheva]

Hi Ben!!Thank you so much for the lectures!! Could you make a video explaining the power handling of microstrip structure? How can I design looking for normal specs (frequency, bandwidth,etc) and also power handling?. Thank you a lot!!! Regards from Lima, Peru!

[@ananthadattadhruva8689]

One very big question, the input from port 1, has 2 options to come to port 4 and it gets isolated because of a 180 degree phase cancellation, the same happens at port 2, there is another path that will give a 180 degree shift that is through the port4 end towards the port3 end and to the port2, that must make port 2 also isolated!, am I thinking correctly, so can someone clarify me on that!??

[@ozzydm]

Yes. I wonder that too.

[@victordatdo9880]

Thank you very much for your lectures, details, straight, easy to understand. Could you make one video tutorial for the Power handling topic? Please help. Thank you gain.

[@MrHeatification]

Splendid really

[@rachitjoshi23]

Could you do some videos on lange couplers for balanced load modulated power amplifiers

[@dmitrydmitry629]

I think at a time 48:43 there is a typo. W should not be 1.96mm but 0.96mm.

[@spsarolkar]

When is episode 6 coming ?

[@karlyocher4360]

What is the whiteboard setup used in this video?

[@rjrodrig]

How much directivity did you get?

[@divyanaveenan]

What is the digital notepad you are using to teach us , that's connected to PC. I'm looking for something like that

[@deckhassan5819]

Thanks, I really appreciated it. Can you please tell me where I can get this blackboard? and the name of it.

[@HappyfoxBiz]

you mean the waccom?

[@ratendrak]

Hi Sir, I want to join two rf signal in to one.. can you help me with it

[@israelhershkovits5675]

HI... DO U KNOW ABOUT UNIT CALLED ' COMBINATOR ' PROBBLY FOR 50 OHM I GESS!! THE FREQUNCY BAND IS THE SECOND MATTER! PUT THESE 2 IN GOOGLE

[@fallofmanbrand]

nice video bro

[@abcdefg91111]

4:04