ISRO Scientist or Engineer Electronics 2015

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For the following questions answer them individually
ISRO Scientist or Engineer Electronics 2015 - Question 2

A sample of Si is doped with $$10^{17}$$ donor atoms/cm$$^3$$. Considering electron mobility in the doped Si 700 cm$$^2$$/V-sec, the approximate resistivity of the doped Si is:

ISRO Scientist or Engineer Electronics 2015 - Question 12

Spectrum of a signal x(t), sampled at period T, is given by:

ISRO Scientist or Engineer Electronics 2015 - Question 18

A 70 MHz carrier is QPSK modulated by a 1.544 Mbps T1 data stream. The transmitter employs a raised-cosine filter with $$\alpha = 0.2$$ What is the transmitted bandwidth of the
signal?

ISRO Scientist or Engineer Electronics 2015 - Question 19

If two tones $$f_1$$, and $$f_2$$, are amplified by a non-linear amplifier, which frequency components would be present in output?

ISRO Scientist or Engineer Electronics 2015 - Question 24

A signal transmitted from an Earth station bounces back from a geostationary satellite, with an altitude of 35864 km from the Earth surface. The range from the Earth station is
38200 km. The round trip time is about: (excluding processing delays and assuming $$c = 3 \times 10^8  m/s$$)

ISRO Scientist or Engineer Electronics 2015 - Question 26

Which of the following is not true?

ISRO Scientist or Engineer Electronics 2015 - Question 27

The following Finite State Machine (FSM) is used to detect a particular pattern in input data stream. Whenever the pattern is matched at input, output is set to ‘l’ or else output is cleared to ‘0’. For which of the following data stream, output goes to ‘1’ twice?

ISRO Scientist or Engineer Electronics 2015 - Question 31

Consider a sequence x(n) = [2, 4, 6, 8, 0, 1, 3, 5, 7, 9]. Down-sample the sequence by 3 and then up-sample by 2. The resulting sequence is:

ISRO Scientist or Engineer Electronics 2015 - Question 33

The phase velocity of a plane wave given by $$E_x = E_o \cos(\omega t - \beta z)$$ with a frequency of 5.0 GHz and a wavelength in the material medium of 3.0 cm is:

ISRO Scientist or Engineer Electronics 2015 - Question 35

The highest frequency for which a circular coaxial transmission line having outer diameter = 3.1 mm and inner diameter = 1.3 mm can be operated in pure TEM mode (assuming free space medium between the two conductors) should be less than:

ISRO Scientist or Engineer Electronics 2015 - Question 36

In a communication system at 300 MHz, the receiving antenna gain is 8 dBi, the transmitting antenna gain is 10 dBi and the transmitting power level is 25 watts, the distance between the transmitter and the receiver is 1 km, the power received at the receiving antenna port (assuming the propagation medium is loss-less):

ISRO Scientist or Engineer Electronics 2015 - Question 37

A rectangular waveguide with air medium has dimensions a = 22.86 mm and b = 10.6 mm is fed by 3 GHz carrier from a coaxial cable, which of the following is false statement for $$TE_{01}$$ mode?

ISRO Scientist or Engineer Electronics 2015 - Question 40

Ratio of skin depths of an Electromagnetic wave inside the conductor for the corresponding frequencies at 4 GHz and 9 GHz, considering the same material properties for both the frequencies is:

ISRO Scientist or Engineer Electronics 2015 - Question 43

A lossless transmission line with characteristic impedance $$Z_0 = 50$$ ohm is 30 m long and operates at 2 MHz. Theline is shorted at the load, if the phase velocity = 0.6 times the velocity of light, the input impedance of the line is:

ISRO Scientist or Engineer Electronics 2015 - Question 45

A parabolic reflector antenna used for reception of data is 1 meter in diameter and operates at 30 GHz. The far field distance of this antenna for a quadratic phase error of 22.5 degree is:

ISRO Scientist or Engineer Electronics 2015 - Question 46

A potential field is given by $$\phi = 2 xy^2 - 3 y^2z$$. If $$\hat{x}, \hat{y}, \hat{z}$$ are the unit vectors along x, y and z directions respectively, the field intensity at (0, 1, 0) is:

ISRO Scientist or Engineer Electronics 2015 - Question 50

A plane wave $$E = 100 \sin(\omega t - 10 x) V/m$$ in a loss less medium with $$\mu = 4 \mu_o, ε = ε_o$$ strikes another medium with 90 degree angle of incidence having $$\mu = 9 \mu_o, ε = ε_o$$, the reflection co-efficient is:

ISRO Scientist or Engineer Electronics 2015 - Question 51

What is the functionality of following digital circuit? A is input data, CLK is system clock and Y is output.

ISRO Scientist or Engineer Electronics 2015 - Question 52

A lossless transmission line has the distributed circuit parameters of inductance and capacitance per meter as 625 nH/m and 64 pF/m respectively, the phase constant of the line at 100 MHz is:

ISRO Scientist or Engineer Electronics 2015 - Question 54

If n number of MOSFETs with identical W/L are connected in series, then equivalent W/L is given by:

ISRO Scientist or Engineer Electronics 2015 - Question 56

What will be the content of Accumulator, Register-B and Overflow Flag (OV) after execution of following 8051 micro-controller assembly code?
MOV A, #65h
MOV OFOh, #14h
DIV AB
DIV AB

ISRO Scientist or Engineer Electronics 2015 - Question 58

Gain and NF of a single stage amplifier is 10 dB and 3 dB respectively. When two such amplifiers cascaded then gain and NF of cascaded amplifier will be:

ISRO Scientist or Engineer Electronics 2015 - Question 66

Reason for superior high frequency performance of metal-semiconductor diode compared to p-n junction diode is:

ISRO Scientist or Engineer Electronics 2015 - Question 69

Input reflection coefficient ‘S11’ of the 2-port network for 50 Ω system is:

ISRO Scientist or Engineer Electronics 2015 - Question 70

The graph below shows operating load line and I-V characteristic of a Schottky diode at two different RF power levels. Under this bias condition RF resistance of the diode:

ISRO Scientist or Engineer Electronics 2015 - Question 71

A BJT is having common emitter current gain 100. Considering 10 V supply and $$V_{BE} = 0.7 V$$ what will be the value of $$R_C$$ and $$R_B$$ to set the quiescent point at $$I_c = 10 mA$$ and $$V_{CE} = 8 V$$

ISRO Scientist or Engineer Electronics 2015 - Question 73

A high gain MESFET packaged device of case-to-channel thermal resistance of the device is $$4.5^\circ C$$/Watt provides 8 W RF output power taking 20 W DC power. What will be the channel temperature of the device if the case temperature of the device maintained at $$55^\circ C$$?

ISRO Scientist or Engineer Electronics 2015 - Question 74

For a class-A FET power amplifier with 10 V drain supply and 2 A drain current bias providing RF load current of 1 A amplitude. What is the DC to RF efficiency for load resistance of 5 Ω?

ISRO Scientist or Engineer Electronics 2015 - Question 76

A unilateral transistor has an output impedance $$Z_{out} = (10 - j10)Ω$$. Value of the series and shunt components of the matching network for complex conjugate match at the output of the device to 50 Ω load are:

ISRO Scientist or Engineer Electronics 2015 - Question 77

Acommunication channel is having a bandwidth of 3000 Hz. The transmitted poweris such that the received Signal-to-Noise ratio is 1023. The maximum data rate that can be transmitted t error-free through the channel is:

ISRO Scientist or Engineer Electronics 2015 - Question 78

A CDMA system requires $$E_b/I_o$$, of 10 dB. Each of the transmitters in the network transmits data at the rate of 1 Kbps with a PN chip rate of 1 Mbps. The maximum number of such users that the network can support is:

ISRO Scientist or Engineer Electronics 2015 - Question 79

Laplace transform of $$e^{\theta t} \sin(\omega t)$$ is:

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