Video: Basics of Bias Tees - including applications and demonstration examples

[w2aew]

Bias Tees are RF components that are used whenever you need to couple a DC, power or low-speed control signal onto an RF signal path.  This video discusses the basics of Bias Tees, how they work, examples of practical construction and a few lab application examples showing them "in action".  Links for the Bias Tees used in this video, as well as a copy of the video notes are here:
https://www.minicircuits.com/pdfs/ZFBT-4R2GW+.pdf
https://www.minicircuits.com/pdfs/ZX85-12G+.pdf
http://www.dorkage.com/youtube/Basics_of_Bias_Tees.pdf

[w2aew]

bumped until i'm home.. as always... thumbs up.

I hope you enjoy it when you get home!

[LapTop006]

Great video as usual.

Happens that I need to build a custom DC blocking terminator for a project, your explanation was better than those I've seen so far, but I still need to find a deeper background to really understand value selection for DC blocks.

[w2aew]

It all depends on what frequency range you need.  The high-pass corner on the low frequency end is easy F=1/(2*pi*C*R) where R is sum of the source and load impedance.  The upper frequency will depend on capacitor selection (dielectric, physical configuration, etc.) which will determine the cap's self-resonant frequency.  For really broadband high-performance DC blocking, you might want to look at the parts from Presidio - see page 10 in this catalog:
http://www.presidiocomponents.com/catalog/RF-MW-FOBrochure6100RevI-May2018.pdf

[LapTop006]

... For really broadband high-performance DC blocking, you might want to look at the parts from Presidio - see page 10 in this catalog:
http://www.presidiocomponents.com/catalog/RF-MW-FOBrochure6100RevI-May2018.pdf

I'm rather more down to the DC end of things, some neat reading though, the SONET references do date the text rather amusingly.

[TheUnnamedNewbie]

An interesting thing is how as our target band goes up and up in frequency, the inductor becomes the easy part and the capacitor becomes an issue. The LC network can also serve as a lumped-element narrow-band matching network, and we use it on integrated circuits to tune out the gate capacitance of a MOSFET. And at some point we just give up on bias-Ts and switch to center-tapped transformers, where we use the center tap on both coils to bias the in/outputs of the system, and provide impedance matching.

Excellent video.

Seeing all those different cables - w2aew, do you make all your cables yourself?

[w2aew]

<<snip>>
Seeing all those different cables - w2aew, do you make all your cables yourself?

I only make a few - most of them are cables I've picked up over the years from a variety of places - ranging from online purchases to hamfest or flea-market finds.