ECE :: Exam Questions Paper
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Consider an AM system using a square law detector as shown in figure.
XC(t) = AC[1 + u x (t)] cos ωct, |ux(t)| << 1
if the channel noise is AWGN with PSD of 
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In the given circuit, the switch is open for a long time. At time t = 0, the switch is closed. What are the initial and final values of voltages across the inductor?
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Consider the following statements:
In the case of space wave propagation, the signal strength at the receiver is- Directly proportional to transmitter and receiver heights.
- Inversely proportional to distance between transmitter and receiver.
- Directly proportional to frequency.
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An 8085 microprocessor is operating at 2 MHz frequency and executes the following program :
START : MOV A, B
OUT 55H
DCR B
STA 2700H
NOP
NOP
JMP START
Identify the total number of machine cycles required to execute the above program till the JMP instruction is executed for the first time. -
An 8085 executes the following instructions
2710 LXI H, 30A0H
2713 DAD H
2714 PCHL
All addresses and constants are in Hex. Let PC be the contents of the program counter and HL be the contents of the HL register pair just after executing PCHL.
Which of the following statements is correct? -
With which decoder it is possible to obtain many code conversions?
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Consider the following statements:
The klystron and travelling wave tube differ from each other,- In TWT the microwave circuit is non- resonant.
- In klystron the microwave circuit is resonant.
- TWT uses attenuator.
- The wave is TWT is a non-propagating wave.
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Consider a system whose input x and output y are related by the equation
y(t) =
x(t - t)h(2t)dt
where h(t) is shown in the graph
which of the following four properties are possessed by the system?
BIBO: Bounded input gives a bounded output
Causal: The system is causal
LP: The system is low pass
LTI: The system is linear and time invariant
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The following components are used to measure power output of a 2 kW TWT amplifier:
- TWTA
- Low pass/high pass filter
- 20 dB attenuator
- 40 dB directional complex with matched load
- Power load
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Consider the following statements regarding sources or error in a Q-meter:
- If a coil with resistance R is connected in direct measurement mode and if the residual resistance of Q-meter is 0.1 R, then the measure Q of the coil would be 1.1 times the actual Q.
- If the inductance to be measured is less than 0.1 mH, the error due to presence of residual inductance cannot be neglected.
- The presence of distributed capacitance in a coil modifies the effective Q of the coil.
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