"Discover Cooking, Discuss Life."

Go Back   Discuss Cooking - Cooking Forums > The Back Porch > Off Topic Discussions
Reply
 
Thread Tools Display Modes
 
Old 04-01-2008, 10:04 AM   #1
Head Chef
 
LT72884's Avatar
 
Join Date: Aug 2007
Location: UTAH, BABY
Posts: 1,421
Physics help

Any one have a physics math background or a background with microwave engineering. I need help with my homework. I have googled but im not finding what i am looking for.

I am trying to find the difference between TE11, TM01, TE01 and TM11 modes for cylindrical waveguides. I know for my waveguide(antenna)i made, had to use the math formulas for TE11 mode but i need to know why i HAD to use TE11 and NOT any of the other modes. There is a reason why i HAD to use TE11 and not any other mode but i cant seem to find it. This is where i need the help.

thanks guys.

__________________

__________________
*A substitute for human interaction* - I really need to find a girl whos name doesnt end with .JPG
http://grillofmydreams.bluedisk.org
LT72884 is offline   Reply With Quote
Old 04-01-2008, 11:54 AM   #2
Senior Cook
 
plumies's Avatar
 
Join Date: Jan 2008
Location: Sunny San Diego
Posts: 444
Does it have anything to do with the cut-off frequencies of those modes? I'm just shooting in the dark here.
__________________

__________________
***************
CAB Cooks
plumies is offline   Reply With Quote
Old 04-01-2008, 01:11 PM   #3
Head Chef
 
LT72884's Avatar
 
Join Date: Aug 2007
Location: UTAH, BABY
Posts: 1,421
Quote:
Originally Posted by plumies View Post
Does it have anything to do with the cut-off frequencies of those modes? I'm just shooting in the dark here.
well, for me yes. because i have the formula for lower cut off but not upper.

for TE11 the formula is

Fc = 1.84(Ce) / 2(pi)b

Ce is velocity of light in a dielectric medium. 3*10^8 same as air.
b is the radius of my can in meters.

0.0389m

so i do this

Fc= 1.84*3(10^8) / 2*3.14159265*.0389

well that gives me

184000000 / .244415908 which = 752815156.3xxxxxx Hz

my professor ended up with 2253000000 Hz or 2.253Ghz

How the heck am i off so much

im not in a physics class, this is for my wireless communications class.
__________________
*A substitute for human interaction* - I really need to find a girl whos name doesnt end with .JPG
http://grillofmydreams.bluedisk.org
LT72884 is offline   Reply With Quote
Old 04-01-2008, 03:24 PM   #4
Senior Cook
 
seans_potato_business's Avatar
 
Join Date: Jan 2008
Location: Edinburgh, Scotland
Posts: 244
I'd suggest you try the Wikipedia Science Reference Desk.
__________________
We don't inherit the Earth from our parents; we borrow it from our children.
seans_potato_business is offline   Reply With Quote
Old 04-02-2008, 11:35 AM   #5
Senior Cook
 
plumies's Avatar
 
Join Date: Jan 2008
Location: Sunny San Diego
Posts: 444
Quote:
Originally Posted by LT72884 View Post
for TE11 the formula is

Fc = 1.84(Ce) / 2(pi)b

Ce is velocity of light in a dielectric medium. 3*10^8 same as air.
b is the radius of my can in meters.

0.0389m

so i do this

Fc= 1.84*3(10^8) / 2*3.14159265*.0389

well that gives me

184000000 / .244415908 which = 752815156.3xxxxxx Hz

my professor ended up with 2253000000 Hz or 2.253Ghz

How the heck am i off so much
Okay, I see where you're off. In the first part of your equation, you forgot to multiply 1.84 by 3. You only applied 10^8.

When I ran the numbers, I ended up with 2258445469 Hz.

Fc = 552000000 / .244415908 = 2258445469

My number isn't the same as your prof's but it's a bit closer.

HTH
__________________
***************
CAB Cooks
plumies is offline   Reply With Quote
Old 04-02-2008, 11:44 AM   #6
Head Chef
 
LT72884's Avatar
 
Join Date: Aug 2007
Location: UTAH, BABY
Posts: 1,421
OMG OMG OMG, i feel like a MORON. LOLOLOLHAHAHAHAHAHA. I dont know how i failed to do that. good thing im not going into math for my degree.

your number is fine. i have to round it to 2.25Ghz anyway. seriously i owe you one. the last math class i took was trig my junior year. after that i didnt continue on. I liek math but its been YEARS since i have done anything with it.

thanx.

I guess the difference between TM and TE modes are the different cut off frequencies they have. I bet TM mode wouldnt be able to capture 2.46Ghz at all.
__________________
*A substitute for human interaction* - I really need to find a girl whos name doesnt end with .JPG
http://grillofmydreams.bluedisk.org
LT72884 is offline   Reply With Quote
Old 04-02-2008, 11:48 AM   #7
Executive Chef
 
Join Date: Oct 2006
Location: New Jersey
Posts: 4,630
OMG Why did I venture in here?
__________________
Jeekinz is offline   Reply With Quote
Old 04-02-2008, 12:42 PM   #8
Master Chef
 
Chief Longwind Of The North's Avatar
 
Join Date: Aug 2004
Location: USA,Michigan
Posts: 9,229
Waveguides, mazers, RF antenna theory, and magnetrons. You bring back so many memories of Navy schools so many years back. I made it through the classes, but digital electronics is sooooo much easier. I'm glad I'm not the one in the physics and electronics classes any more. But keep on pushing through. You're doing just fine.

Seeeeeeeya; Goodweed of the North
__________________
“No amount of success outside the home can compensate for failure within the home…"

Check out my blog for the friendliest cooking instruction on the net. Go ahead. You know you want to.- http://gwnorthsfamilycookin.wordpress.com/
Chief Longwind Of The North is offline   Reply With Quote
Old 04-02-2008, 12:49 PM   #9
Executive Chef
 
YT2095's Avatar
 
Join Date: Aug 2006
Location: Just left of Europe and down a bit.
Posts: 3,875
Send a message via MSN to YT2095
and I can warm up your dinner from across the room if you`re a slow eater with MW Cannon :)

effective range 160 feet Tested!

let it not be said that I`m a less than accomodating Host when it comes to meal times (or loud music played in the middle of the night across the road!).
__________________
So long and Thanks for all the Fish ;)

YT2095 is offline   Reply With Quote
Old 04-02-2008, 12:53 PM   #10
Master Chef
 
Chief Longwind Of The North's Avatar
 
Join Date: Aug 2004
Location: USA,Michigan
Posts: 9,229
Quote:
Originally Posted by YT2095 View Post
and I can warm up your dinner from across the room if you`re a slow eater with MW Cannon :)
Are you using a parabolic antenna to focus that energy. I wouldn't want you going sterile from absorbing a bit too much RF.

Do you remember having to tune magnetron cavities with a set screw?

Seeeeeeya; Goodweed of the North
__________________

__________________
“No amount of success outside the home can compensate for failure within the home…"

Check out my blog for the friendliest cooking instruction on the net. Go ahead. You know you want to.- http://gwnorthsfamilycookin.wordpress.com/
Chief Longwind Of The North is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



» Discuss Cooking on Facebook

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 09:57 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.