Visit RFCafe.com Thanks for visiting RFCafe.net Thanks for visiting the RF Cafe Archives Thank you for visiting RF Cafe Thank you for visiting the RF Cafe Archives!

How far can flex waveguide bend without adverse RF issues? - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues - primarily having to spend time purging garbage posts from the board. At some point I might start the RF Cafe Forums again if the phpBB software gets better at filtering spam.

Below are the old forum threads, including responses to the original posts.

-- Amateur Radio
-- Anecdotes, Gripes & Humor
-- Antennas
-- CAE, CAD, & Software
-- Circuits & Components
-- Employment & Interviews
-- Miscellany
-- Swap Shop
-- Systems
-- Test & Measurement
-- Webmaster

murraymt
 Post subject: How far can flex waveguide bend without adverse RF issues?
Posted: Mon Dec 13, 2010 11:12 am 
 
Lieutenant

Joined: Fri Dec 10, 2010 2:59 pm
Posts: 2
since I've read that wave guide bends should have a radius of greater than two wavelengths, I was wondering why the bend radius limits of wr75 and most other sizes of flexible waveguide are less than two wavelengths, and I can't find any specifications addressing this.

Shouldn't the flex waveguide bend adhere to the two wavelength radius standard?

Here I will "paste" some of the literature I've read. This literature can be found at http://www.tpub.com/content/et/14092/css/14092_78.htm and many other places. It is from the NAVY Training guide (the "figures" did not copy and paste):

Waveguide Bends The size, shape, and dielectric material of a waveguide must be constant throughout its length for energy to move from one end to the other without reflections. Any abrupt change in its size or shape can cause reflections and a loss in overall efficiency. When such a change is necessary, the bends, twists, and joints of the waveguides must meet certain conditions to prevent reflections. Waveguides maybe bent in several ways that do not cause reflections.

One way is the gradual bend shown in figure 3-48. This gradual bend is known as an E bend because it distorts the E fields. The E bend must have a radius greater than two wavelengths to prevent reflections. Figure 3-48.—Gradual E bend.

Another common bend is the gradual H bend (fig. 3-49). It is called an H bend because the H fields are distorted when a waveguide is bent in this manner. Again, the radius of the bend must be greater than two wavelengths to prevent reflections. Neither the E bend in the “a” dimension nor the H bend in the “b” dimension changes the normal mode of operation. Figure 3-49.—Gradual H bend. 3-22


 
   
 
Kirt Blattenberger
 Post subject: Re: How far can flex waveguide bend without adverse RF issue
Posted: Mon Dec 13, 2010 12:21 pm 
 
Site Admin
User avatar

Joined: Sun Aug 03, 2003 2:02 pm
Posts: 451
Location: Erie, PA
Greetings murraymt:

The rules of thumb are good for when you don't have the luxury of a manufacturer's spec to go by. If the company that makes the waveguide certifies that it will perform within some VSWR spec with a bend radius of less that two wavelengths, then I would go with that.

It's kind of like the air pressure spec printed on car tires. The tire might be stamped for 32 psi, but if your car manual says inflate to 30 psi, then that overrides the tire's broad application spec. The car engineers have designed the suspension/braking to perform maximally at their spec, not the tire company's (which is basically a rule of thumb type number for people who don't read their owner's manuals).

_________________
- Kirt Blattenberger :smt024
RF Cafe Progenitor & Webmaster


 
   
 
murraymt
 Post subject: Re: How far can flex waveguide bend without adverse RF issue
Posted: Mon Dec 13, 2010 1:02 pm 
 
Lieutenant

Joined: Fri Dec 10, 2010 2:59 pm
Posts: 2
Thank-you for the quick reply. I haven't found any specs that say it will perform within some VSWR spec with a bend radius of less that two wavelengths, or for any radius. They spec it as a mechanical tolerance which is why I asked here, I didn't know where else to get an answer. I suppose I could call various manufacturers, but it was more of a curiosity on my part.




Posted  11/12/2012
RF Stencils for Visio v3.1 by RF Cafe
RF Cascade Workbook 2018 (GS) - RF Cafe
About RF Cafe Archives
Kirt Blattenberger - RF Cafe Webmaster
Copyright: 1996 - 2024
Webmaster:
    Kirt Blattenberger,
    BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:  AirplanesAndRockets.com

spacer