For my final year undergraduate project i am designing an Antenna for Radar applications and following is a great article to understand the concept of the Balance transmission line and the Unbalanced transmission line.
http://www.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=6
Summary:
Balanced transmission line has parallel conductors which carries current which are equal in magnitude but opposite in direction. Which makes the overall electromagnetic fields the conductors induce
approximately cancel out. So the transmission lines which are balanced does not radiate any waves which makes them not a part of the antenna but a medium which assist in transferring the power back and forth of the antenna.
In contrast to the Balanced transmission line the unbalanced transmission line has parallel conductors which contains current which are not equal in magnitude. It makes the net induced electromagnetic flux non-zero making the transmission line a part of the antenna and it will radiate a portion of the power which is transmitted by the transmitter. Therefore the efficiency of the antenna will be less.
A coaxial cable's outer shield is typically connected to the ground, and if it is a solid ground connection then the voltage at the outer conductor will always be zero. That makes the center conductor carrying the net differential voltages which makes it an unbalanced transmission line.
To connect an unbalanced transmission line to a balanced system we need a component which is known as the balun. What balun does is that it converts an unbalanced circuit into a balanced circuit. Sometimes the balun is designed such a way that it acts as an impedance transformer.
Thank you.
Saturday, February 9, 2013
Thursday, February 7, 2013
HP-DV6-3122tx vga issues
These days I am facing a new issue in my laptop. That is obviously an issue related with my VGA cards. The issue is as follows,
When i switch on the laptop it boots up up until the place where the windows windows logo appear. After that, in a while, the screen goes blank. The most messed up part is that still i can hear the windows log on sounds and all. When i swipe my finger on the fingertip reader i can here the windows playing the sound which comes when we log into the user account. That means even without the VGA the laptop is working.
So by default i logged into windows using the safe mode. It worked perfectly. After i logged in i uninstalled both the VGA cards and restarted the machine to see what will happen. Then of course everything worked perfectly and windows was able to detect and install the VGA plug and play drivers.
Nevertheless, when i switch off the pc and restart it sometimes the same problem occurs. I suspect that it is something about the VGA drivers. May be my drivers are not compatible with the Windows 7 SP 1.
Who knows?
If i found any fix i will post it here.
Thank you.
Sunday, February 3, 2013
Messing with K300i
This is something I recently did with my Sony Ericsson K300i phone. Actually it was not working so i really wanted to dissemble it and see what is wrong in it. Basically i did not have any idea on how to like repair phones. Same as any ordinary person what i did was google about it. The problem with my phone was that it cannot be charged. That is even with the charger connected it cannot be used. Apparently the problem was pretty general and there were posts on soldering few jumper wires to by pass some circuitry in the phone. Which i found a bit challenging given that my soldering iron is a cheap one and it is obviously not meant to stand up to SMD soldering. :D
Nevertheless i dissembled the phone using my newly purchased tool kit which is very cheap but has around 38 different tools <GOD BLESS CHINA!!!>. :D Dissembling the phone was pretty easy, i just removed few screws and pulled the cover away. There was a good post on K300i dissembly,
After dissembling the phone i connected the charger and moved the female charger adapter connected to the phone a little bit away from the phone and it started working :D. So i used a small piece of rubber to fix the adapter in that position and assembled the phone. Now it's working again.
The problem with my phone was that since it is old and the charger adapters have been used so many times, the contacts which connects the charger to the phone were slightly disoriented. By placing the piece of rubber i could perfectly make the contacts and give life back to circuitry.
This might be useful to you if you have a similar problem.
Thank you.
Nevertheless i dissembled the phone using my newly purchased tool kit which is very cheap but has around 38 different tools <GOD BLESS CHINA!!!>. :D Dissembling the phone was pretty easy, i just removed few screws and pulled the cover away. There was a good post on K300i dissembly,
http://www.formymobile.co.uk/k300lcd.htm
After dissembling the phone i connected the charger and moved the female charger adapter connected to the phone a little bit away from the phone and it started working :D. So i used a small piece of rubber to fix the adapter in that position and assembled the phone. Now it's working again.
The problem with my phone was that since it is old and the charger adapters have been used so many times, the contacts which connects the charger to the phone were slightly disoriented. By placing the piece of rubber i could perfectly make the contacts and give life back to circuitry.
This might be useful to you if you have a similar problem.
Thank you.
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