MES Jr. Grade • 2015 • Paper-III
Describe the flag registers in 8085 microprocessor.
MES Jr. Grade • 2015 • Paper-III
A rectangular waveguide has width a. Then the cutoff frequency (with corresponding wavelength λ) is
A)
a= λ/2
B)
a= λ/C
C)
a= λ/4
D)
a=2λ
For a rectangular waveguide, the cutoff condition for the dominant mode (TE10) occurs when the guide width equals half the cutoff wavelength. Hence, a = λ/2. The other options do not match the standard cutoff relation for rectangular waveguides.
MES Jr. Grade • 2015 • Paper-III
What is quantization of signals? How can the quantization error be reduced?
MES Jr. Grade • 2015 • Paper-III
8255 is a
A)
Programmable peripheral interface
B)
I/O device
C)
Memory chip
D)
None of these
Intel 8255 is the 8255 Programmable Peripheral Interface (PPI) chip used to interface input/output devices with a microprocessor. It provides programmable parallel I/O ports. It is not a memory chip, and while it is an I/O-related device, the precise and standard name is Programmable Peripheral Interface.
MES Jr. Grade • 2015 • Paper-III
The positive peak of an AM wave is 16V and the minimum value is 4V. Assuming single tone modulation, the modulation index is
A)
0.6
B)
0.25
C)
4
D)
0.36
For an AM wave, the modulation index is m = (Vmax - Vmin) / (Vmax + Vmin). Here Vmax = 16 V and Vmin = 4 V. So, m = (16 - 4) / (16 + 4) = 12 / 20 = 0.6. Hence, the correct option is (a).
MES Jr. Grade • 2015 • Paper-III
What are TE and TM modes? Why is TE called the dominant mode in rectangular waveguide?
MES Jr. Grade • 2015 • Paper-III
Which of the following parameters is negligible in transmission lines?
A)
R
B)
L
C)
C
D)
G
In transmission line modeling, the shunt conductance G represents leakage current through the insulation between conductors. For overhead transmission lines, this leakage is extremely small, so G is usually neglected. Resistance R, inductance L, and capacitance C are all significant and are included in line analysis.
MES Jr. Grade • 2015 • Paper-III
In a PCM system, if we increase the quantization levels from 2 to 8, how do the relative bandwidth requirements vary?
A)
Get doubled
B)
Get tripled
C)
Remain same
D)
Become eight times
In PCM, the number of bits per sample is n = log2(L), where L is the number of quantization levels. Increasing levels from 2 to 8 changes n from 1 bit to 3 bits. Since PCM bit rate and hence required bandwidth are proportional to the number of bits per sample, the bandwidth becomes 3 times. Therefore, the relative bandwidth requirement gets tripled. Options (a), (c), and (d) are incorrect because the increase is not by a factor of 2, unchanged, or 8 in this case.
MES Jr. Grade • 2015 • Paper-III
If a line is terminated in characteristic impedance Z0; the input impedance measured at the input will be
A)
Z0
B)
Z0 /2
C)
zero
D)
infinite
For a transmission line terminated in its characteristic impedance Z0, there is no reflection at the load. Hence the input impedance seen at the sending end equals the characteristic impedance itself, i.e., Z_in = Z0. Therefore, the correct option is (a). The other options are incorrect because Z0/2, zero, and infinite input impedance occur only under special mismatched or open/short-circuited conditions, not when the line is properly matched.
MES Jr. Grade • 2015 • Paper-III
How are instruction set of 8085 classified? Explain with example.
MES Jr. Grade • 2015 • Paper-III
In single tone AM modulation, the transmission efficiency for m=1 is
A)
33.3%
B)
50%
C)
100%
D)
16.65%
For single-tone AM, transmission efficiency is the ratio of sideband power to total transmitted power: η = m^2 / (2 + m^2). For m = 1, η = 1 / (2 + 1) = 1/3 = 33.3%. Hence the correct option is (a). Option (b) 50% is not correct for standard AM, (c) 100% is impossible in conventional AM, and (d) 16.65% is too low.
MES Jr. Grade • 2015 • Paper-III
Which signaling scheme is most affected by noise?
A)
ASK
B)
FSK
C)
PSK
D)
QAM
Amplitude Shift Keying (ASK) is most affected by noise because its information is carried in the signal amplitude. Noise commonly disturbs amplitude, so ASK is more vulnerable than FSK and PSK. QAM also uses amplitude, but in basic digital modulation comparisons, ASK is considered the most noise-sensitive scheme.
MES Jr. Grade • 2015 • Paper-III
Impedance inversion may be obtained with
A)
A short circuited stub
B)
A quarter wave line
C)
An open circuited stub
D)
A half wave line
Impedance inversion is a property of a quarter-wave transmission line. For a line of length \(\lambda/4\), the input impedance becomes \(Z_{in}=\frac{Z_0^2}{Z_L}\), so a high load impedance appears as low at the input and vice versa. This is called impedance inversion. A short-circuited or open-circuited stub can provide specific reactances, and a half-wave line repeats the load impedance, not invert it.
MES Jr. Grade • 2015 • Paper-III
Which of the following is analog in nature?
A)
PCM
B)
PWM
C)
delta modulation
D)
differential PCM
PWM (Pulse Width Modulation) is analog in nature because the information is represented by varying the width of pulses continuously according to the message signal. In contrast, PCM, delta modulation, and differential PCM are all digital pulse modulation techniques, since they encode the signal into discrete levels or binary form.
MES Jr. Grade • 2015 • Paper-III
Most electromagnetic transmission in rectangular waveguide uses
A)
TE10 mode
B)
TE01 mode
C)
TE20 mode
D)
TE11 mode
In a rectangular waveguide, the dominant mode is TE10. It has the lowest cutoff frequency, so it is the mode most commonly used for electromagnetic transmission. TE01 and TE20 have higher cutoff frequencies, and TE11 is not the dominant mode in a rectangular waveguide.
MES Jr. Grade • 2015 • Paper-III
In a Klystron amplifier the input cavity is called
A)
buncher
B)
catcher
C)
pierce gun
D)
collector
In a klystron amplifier, the input cavity is the **buncher cavity**. It modulates the velocity of the electron beam, causing electrons to bunch together. The output cavity is called the **catcher cavity**, which extracts energy from the bunched beam. A **pierce gun** is the electron gun that produces the beam, and the **collector** collects the spent electrons.
MES Jr. Grade • 2015 • Paper-III
Using suitable diagram, explain the working principle of envelope detector for demodulating AM signal.
MES Jr. Grade • 2015 • Paper-III
The maximum number of characters for variable names in C is
A)
4
B)
8
C)
12
D)
16
In many standard exam contexts, the maximum significant length of a C variable name is taken as 8 characters. Historically, older C compilers recognized only the first 8 characters of an identifier. Among the given options, 8 is the expected answer. The other options are not the standard exam answer.
MES Jr. Grade • 2015 • Paper-III
What is the need for altitude control for a satellite? Name two altitude control components in satellite communication.
MES Jr. Grade • 2015 • Paper-III
An instruction used to set the carry flag in a computer can be classified as
A)
Data transfer
B)
Arithmetic
C)
Logical
D)
Program control
An instruction that sets or manipulates the carry flag is generally treated as a program control instruction because it affects the status/control flags used for branching and decision-making. Data transfer instructions move data, arithmetic instructions perform calculations, and logical instructions perform bitwise operations. Since setting the carry flag changes processor control status rather than transferring data or doing arithmetic directly, the correct classification is program control.
MES Jr. Grade • 2015 • Paper-III
The data structure needed to convert infix notation to prefix notation is
A)
queue
B)
stack
C)
tree
D)
graph
To convert infix notation to prefix notation, a stack is used to temporarily store operators and manage precedence and associativity. This is the standard method in expression conversion algorithms. A queue is not suitable for operator precedence handling, while tree and graph are not the required linear data structures for this conversion.
MES Jr. Grade • 2015 • Paper-III
Which of the following computer memories is fastest?
A)
cache
B)
primary
C)
mass storage
D)
backup memories
Cache memory is the fastest among the given options because it is located very close to the CPU and stores frequently used data/instructions for quick access. Primary memory (RAM) is slower than cache, while mass storage (like HDD/SSD) and backup memories are much slower than both.
MES Jr. Grade • 2015 • Paper-III
Which of the following is not a negative resistance device?
A)
Gunn diode
B)
Tunnel diode
C)
Impatt diode
D)
Varactor diode
A negative resistance device exhibits a region where an increase in voltage causes a decrease in current. Gunn diode, tunnel diode, and IMPATT diode are all used as negative resistance devices in microwave circuits. A varactor diode, however, is a voltage-controlled variable capacitor used for tuning, not a negative resistance device.
MES Jr. Grade • 2015 • Paper-III
Light may be propagated along a fiber-optic cable in which of the following modes?
A)
multimode step index
B)
single-mode step index
C)
multimode graded index
D)
all of these
Light can propagate through fiber-optic cables in multiple modes depending on the fiber design: multimode step-index, single-mode step-index, and multimode graded-index. Since all three are valid propagation modes, the correct answer is 'all of these'.
MES Jr. Grade • 2015 • Paper-III
A sinusoidal voltage of 2 kV peak value is amplitude modulated to give 20% modulation. The peak value of each side band term is
A)
800V
B)
400V
C)
200V
D)
100V
For single-tone AM, the peak value of each sideband component is (mVc)/2, where m is the modulation index and Vc is the carrier peak value. Here, Vc = 2 kV = 2000 V and m = 20% = 0.2. So each sideband peak = (0.2 × 2000)/2 = 200 V. Hence, the correct option is (c).
