"Short Length" Directional Couplers - RF Cafe Forums
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Post subject: "Short Length" Directional Couplers
postPosted: Thu Jan 01, 2004 12:02 pm
been told that the best physical length for a directional coupler is
1/4 wavelength. However, I have used many couplers that are much shorter
then 1/4 wavelength.
I have been told that this is accomplished
by balancing the even and odd mode impedances. Would it be possible
for you to tell me were I can find information about this. I do not
care if it is a website, magazine or book.
Thank you for your
time and help.
"Short Length" Directional Couplers
Unread postPosted: Fri Jan 02,
2004 3:53 pm
Welcome to forum!
There are many different techniques
to bring about the physical realization of passive couplers (i.e. Cross-Band
Couplers, Directional & Dual-Directional Couplers). In your case,
Directional Couplers with less than quarter-wavelength (<1/4 WL)
is possible and can be done dependent upon your applications. I have
recently designed 4 ports Directional Couplers with < ¼ WL at Fc
at 5.4521…GHz and other in 18.7145…GHz for low-power applications using
Microstrip technology and with internal 50 Ohm/Z terminated and other
with external 50 Ohm/Z connected to an RF Amplifier…) Sorry OEM sold
to is confidential! I also have designed substantial amount of them
at high power level for VHF (RF sample)… and GSM radio applications.
Now, there are several tradeoffs in < ¼ WL Directional Couplers design,
benefits, cost and disadvantages to be consider (i.e. bandwidths, isolation,
reverse power, directivity & power level, physical size, dielectric
substrate material, thermal issues…etc). Sometime, one can be surprised
what some old books can bring to light! Now, following are many books,
articles and software. I’m confident some of them will be of your benefits.
http://www.newwaveinstruments.com/resou ... ftware.htm
addition, I’m currently designing a micro-small Directional Couplers
Stacked Technology (DCST) and will include several ports and <1/4
WL. I will be releasing this technology on the web as soon as we finish
the legal and protection matter (patent).
I thought this might
help you at this time. Keep in touch and Good luck!