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.
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.
Honestly, i didn’t know the answer but said receiver complexity.
Scientist: Forget complexity, tell me interms of bandwidth requirement.
Then next scientist opposite to him joins him and asks the same question to me.
I just keep quiet. The scientist in the middle then interrupts and asks the next person , this time the scientist sitting opposite to the ones who asked me questions.
Scientist: You might have studied microprocessors. Tell me if i say 8 bit microprocessor, what does it mean.
Me: It signifies the length of data bus.
Scientist: Why not address bus? Okay, give me an example.
Scientist: Give me example of 16bit microprocessor.
Scientist: What is the length of address bus in 8086
Me: 16 bit,
he laughs, i say 32 bit.
The other scientist interrupts and repeats the question for me.
I say, im confused between 16 and 32 bits.
Finally, the senior scientist in the centre interrupts and says, its okay. And says thank you. All scientist nod their heads and say okay, fine, thank you.
I stand up and say that i got my seminar work. They say, we wanted project work. I say that i gave seminar on Theory of Relativity. The main scientist says, okay and after a pause says Good. I come out of the room.