A radar receiver has a noise figure of 10 dB at 300 K having a bandwidth of 2.5

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Question
A radar receiver has a noise figure of 10 dB at 300 K having a bandwidth of 2.5 MHz. The minimum power it can receive is
Options
A. 3.45 x 10^-15 W
B. 1.38 x 10^-15 W
C. 7.5 x 10^-15 W
D. 93.15 x 10^-15 W

Correct Answer

93.15 x 10^-15 W

Explanation

P_m = kT₀?_f(F - 1) = 93.15 x 10^-15 W.

Exam Questions Papers problems

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1. For a given voltage, four heating coils will produce maximum heat when connected
Options
A. all in parallel
B. all in series
C. with two parallel pairs in series
D. one pair in parallel with the other two in series

2. The continuous time system with impulse response h(t) = is stable, for n is even, when
Options
A. a = 0
B. a > 0
C. a < 0
D. a ? 0

3. An impulse function consist of
Options
A. pure dc
B. pure a.c
C. entire frequency range with constant phase
D. infinite bandwidth with linear phase vaariations

4. Consider Pole zero diagram as shown, If two Poles are moved in opposite direction towards ? = p/2 and -p/2, the filter will be
Options
A. change to high pass filter
B. change to Band Pass filter
C. remains same
D. change to LPF

6. Consider the probability density f(x) = ae^-b|x| where x is a random variable whose allowable values range from x = - ? to x = + ?. P(1 ? x ? 2)
Options
A.
B.
C.
D. (e^-b - e^-2b)

7. Find 'X' in the circuit below :

f₁(A, B, C, D) = ?(6, 7, 13, 14);
f₂(A, B, C, D) = ?(3, 6, 7);
f₃(A, B, C, D) = ?(5, 6, 7, 14, 15)
Options
A. p(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15)
B. 0
C. ?(14)
D. 1

8. The gradient of any scalar field always yields __________ .
Options
A. a solenoidal field
B. a conservative field
C. an irrotational field
D. none of these

9. The antenna current of an AM transmitter is 8 A, when only the carrier is sent, but it increases to 8.93 A when the carrier is modulated by a single sine wave. Determine the antenna current when the percent of modulation changes to 0.8
Options
A. 9.19 A
B. 9.91 A
C. 10.56 A
D. 8.61 A

10. Consider the signal flow graph shown in figure below. The gain is :
Options
A.
B.
C.
D.

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