Antennas for Microwave Heating

[biff44]

Anyone have any standard antenna or leaky waveguide designs they can share for microwave heating applications at either 915 or 2450 MHz? Am looking for designs that can uniformly distribute heating energy over the inside of a length (tbd) of 2 foot or bigger diameter pipe. Thanks!
Rich

http://www.MaguffinMicrowave.com

Maguffin Microwave wireless design consulting

 

[MacGyverS2000]

Can't help you on the design, but I'd be interested to know what the application is... sounds, uh, unique

Dan - Owner

http://www.Hi-TecDesigns.com

 

[VEBill]

Microwave ovens (also 2.45GHz) have the same requirement for even distribution within the chamber. They address the requirement with turntables and stirring devices. The antenna itself is just an open waveuide.

Can you tumble-dry [?] the contents by rotating the pipe?

 

[Higgler]

E plane sectoral horn would do it. Buy a waveguide to coax adapter and go to your local machine shop to have them add a flared section in the E plane out to your dimensions needed. The nice thing about your heating needs is that you can flare the horn quickly since you don't need the phase to be perfect at your pipe. Flaring it in the E plane makes the field more equal along the whole section of your pipe than flaring it in the H plane, which puts a cosine taper on the pipe.

You have to pick a frequency that matches your pipe width, what's your pipe width?

Are you going to cut a slot in a pipe and add a microwave safe window in it for the rf to propagate through, or is it plastic pipe?

kch

 

[biff44]

It is steel, and probably will be pressurized.

Thanks, I did not realize the difference in power uniformity Eplane vs Hplane horns!

Rich

http://www.MaguffinMicrowave.com

Maguffin Microwave wireless design consulting

 

[Higgler]

first thought is a bicone antenna, set inside a plastic tube of about 5" diam. x 24" long. Bicones are really wide bandwidth and placing it in a thick walled plastic tube. The tube will keep the material flowing around it away from the feed point and help to more evenly distribute heating.

Can you describe what length of this tube can be used for heating? 2 feet, 200 feet? one inch?

kch

PS: The definition of E plane sectoral or H plane sectoral is just the dimension they flare in.
The electric field taper is always;
none in the E plane (i.e. uniform)
cosine in the H plane.
E plane is the orientation of the connector/probe.