ISRO INTERVIEW PATTERN- ON JUN 2008 At BANGALORE
The senior scientist sitting at the middle asked for the subjects i prepared most. I told Radars and Satellite communications. He fired few questions on radars and other 9 members asked one or two questions, that's all. I was mostly asked from Satellite communications. I'm keeping my fingers crossed!!!!!!!!! I just have a good feeling about this man, i just hope i make it into ISRO. Do you want more on the interview. Scroll down.
I enter the room, the main scientist calls my name and asks me to take a seat. Its a long oval shaped table with me at other end and nine scientists at other end. First he asked me about the gap after my graduation. I told him i had an offer with Infosys but didn't like the software domain. He smiles. Then he said, what did you do for a year. I said, i prepared for GATE but couldn't attend it. Next,
Scientist in the middle: which subjects you prepared most?
Me: My favourite subjects are Radars and Satellite communications.
Scientist in the middle: Out of the two, which do you prefer.
Me: Pause, Radars. http://www.TowardsJob.com
Scientist in the middle: What is meant by RADAR.
Me: Radio Detection and Ranging.
Scientist in the middle: What principle does it work on?
Me: Doppler effect. (I explain in detail about it)
Scientist in the middle: No, doppler effect can be used in RADAR but what principle does it work on.
Me: RADAR works on the principle of finding the position and velocity of target amidst clutter.
Scientist in the middle: What is clutter?
Me: Clutter is disturbance caused by land, sea, and sky clutter.
Scientist in the middle: What kind of signals can be used in RADAR.
Me: Both continuous waves and pulsed waves.
Scientist in the middle: If we use continuous waves, then receiver will run into saturation.
Me: We can use separate transmitter and receiver rather than a duplexer.
He doesn't seem impressed.
Next, he request scientist on his right, Mr. Ashok if i remember to ask me some questions.
He asks me wavelength of 300MHz wave, i request for paper. They say its available on the table. The scientist in the middle says you don't need to calculate it. I laugh and still scratch on the paper and work it out as 1 metre. Stupid of me. I could have just answered normally.
The next scientist on the right asks me some questions on satellite communications.
Scientist: What is the main difference between satellite and cellular communications.
Me: Satellite is mainly a repeater in the sky, which is basically used for long distance communications where are cellular communications use local networks to work.
Scientist: Can't we use satellite for short distance then?
Me: We can.
Scientist: Then what is the basic difference between satellite and cellular communications.
Me: I stick on the aswer that satellites are used to carry long distance traffic. He drops the question.
Scientist: What distance do the satellites use.
Me: I mistake it for delay and say that it takes about 270mS.
Scientist: No, the range?
Me: 36000 kilometers. He seems satisfied.
Scientist: Can we use LEO satellites for communications?
Scientist: Give me an example.
He nods his head in agreement.
Now, the focus on to the next scientist on his right.
Scientist: You might have heard about modulation schemes. Why are there so many modulation schemes like BPSK,QPSK, QAM etc.
Me: It depends upon the application.
Scientist: Which is used in satellite comm.
Me: BPSK is most widely used in satellite comm.
Scientist: Can't we use others? What is the difference between 8QPSK and other schemes.
Me: 8QPSK uses only 8 signal points in signal space while others use variable signal points.
Scientist: What is the difference betw. 8PSK and other schemes.