Interview Questions- MBA Admissions- Job Interviews
- Electronics and Communication, Applied Electronics
• Define virtual ground
Virtual ground (sometimes called virtual earth) is an important concept found in electronic circuit designs. It identifies a point in a circuit as being held close to the circuit's ground or reference level electric potential. It is called virtual since this point does not have any real electrical connection to ground. The reference may or may not be the same as the local utility ground or earth
• Define real ground
Real ground: Voltage is a differential quantity, which appears between two points. In order to deal only with a voltage (an electrical potential) of a single point, the second point has to be connected to a reference point (ground) having usually zero voltage. This point has to have steady potential, which does not vary when the electrical sources "attack" the ground by "injecting" or "sucking" a current to/from it. Usually, the power supply terminals serve as grounds; when the internal points of compound power sources are accessible, they can also serve as real grounds
• whatis intersymbol interference ans:
In telecommunication, intersymbol interference (ISI) means a form of distortion of a signal that causes the previously transmitted symbols to have an effect on the currently received symbol. This is usually an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication less reliable. ISI is usually caused by echoes or non-linear frequency response of the channel. Ways to fight against intersymbol interference include adaptive equalization or error correcting codes (especially soft-decoding with Viterbi algorithm).
• Why crystal is a preferred clock source?
Because of high stability, large Q (Quality Factor) & the frequency that doesn’t drift with aging. Crystal is used as a clock source most of the times.
• What does Quality factor mean?
The Quality factor is also defined, as Q. So it is a number, which reflects the lossness of a circuit. Higher the Q, the lower are the losses.
• What is DTMF
Dual-tone multi-frequency signaling (DTMF) is used for telecommunication signaling over analog telephone lines in the voice-frequency band between telephone handsets and other communications devices and the switching center.
• whats channel coding theorem
Channel coding theorem says "Let a discrete memoryless scource with an alphabet p have entropy H(p) and produce symbols once every Ts seconds. "Let a memoryless channel have capacity C and be used once every Tc seconds. Then if H(p)/Ts <= C/Tc there exists a coding scheme for which the source output can be transmitted over the channel and reconstructed with very small error."
• where is channel coding theorem used
This is basically used for Error Detection.
• what is Hoffman coding
Hoffman code is a source code whose average word length approaches the fundamental limit set by the entropy of a discrete memoryless source.It is optimum in the sense that it follows Source coding very closely
• What is Time Convolution theorem
Time convolution theorem: Convolution in time domain = Multiplicaiton in Frequency domain x1(t) * x2(t) <---> X1(w) x X2(w) --
• What is Frequency Convolution theorem
"Frequency Convolution theorem :Convolution in freuqncy domain = 2pi x Multiplication in time domain X1(w) * X2(w) <---> 2pi x x1(t) x x2(t)"
