Communication Engineering Set 6

Answer: faraday rotation

Explaination:
generally for satellite communication circular polarization is required. the polarization received by waves from satellite is changed by faraday rotation.

Answer: resistive

Explaination:
in antenna impedance, impedance related the voltage and current at the input of the antenna. the real part of antenna impedance represents power that is either radiated away or absorbed within the antenna and the imaginary part of antenna impedance represents power that is stored in the near field of antenna. the input impedance of a lossless antenna is purely resistive.

Answer: time division multiple access

Explaination:
tdma stands for time division multiple access. it can be seen as a channel access method for shared-medium networks.

Answer: space switching

Explaination:
space switching is the used term for signals moving from one line to another.

Answer: false

Explaination:
psk stands for phase shift keying. it is a modulation scheme that conveys information by changing the phase of carrier.

Answer: time switching

Explaination:
time switching is the used term for moving pcm samples moving from one time slot to another.

Answer: false

Explaination:
a waveguide is a line through which electromagnetic waves are passed for

Answer: line of sight

Explaination:
line of sight is a line between two points. it is a straight path between a transmitting antenna and a receiving antenna.

Answer: carrier to noise ratio that exceeds a given value

Explaination:
we can measure performance of an analog microwave system by calculating the carrier to noise ratio that exceeds a given value. it gives the signal to noise ratio.

Answer: red green blue

Explaination:
rgb stands for red green blue. it is an additive color model in which red, green and blue light intensity and different shades are added together in various ways to reproduce a broad variety of colors.

Answer: 525

Explaination:
ntsc stands for national television system committee. in ntsc, it is standardized fixed that it has total 525 lines.

Answer: brightness

Explaination:
luminance refers to brightness. it is a photometric measure of luminous intensity per unit area of light travelling in a given direction.

Answer: false

Explaination:
linear modulation techniques are bandwidth efficient. they are used in wireless communication systems when there is an increasing demand to accommodate more and more users within a limited spectrum.

Answer: fsk

Explaination:
oqpsk, π/4 qpsk and bpsk are the most popular linear modulation techniques. they have very good spectral efficiency. however, fsk is an non-linear modulation technique.

Answer: phase

Explaination:
in binary phase shift keying (bpsk), the phase of a constant amplitude carrier signal is switched between two possible values m1 and m2. these two values corresponds to binary 1 and 0 respectively.

Answer: false

Explaination:
bpsk uses coherent or synchronous demodulation. it requires the information about the phase and frequency of the carrier be available at the receiver.

Answer: false

Explaination:
differential phase shift keying uses noncoherent form of phase shift keying. noncoherent form avoids the need for a coherent reference signal at the receiver.

Answer: bpsk

Explaination:
in dpsk system, input binary sequence is first differentially encoded and then modulated using a bpsk modulator. the differentially encoded sequence is generated

Answer: twice

Explaination:
quadrature phase shift keying (qpsk) has twice the bandwidth of bpsk. it is because two bits are transmitted in a single modulation symbol. the phase of the carrier takes on one of the four equally spaced values, where each value of phase corresponds to a unique pair of message bit.

Answer: same

Explaination:
the bit error probability of qpsk is identical to bpsk but twice as much data can be sent in the same bandwidth. thus, when compared to bpsk, qpsk provides twice the spectral efficiency with exactly the same efficiency.

Answer: offset quadrature phase shift keying

Explaination:
oqpsk stands for offset quadrature phase shift keying. it is a modified form of qpsk which is less susceptible to deleterious effects and supports more efficient amplification. oqpsk is sometimes also called staggered qpsk.

Answer: identical

Explaination:
the spectrum of an oqpsk signal is identical to that of qpsk signal. hence, both signals occupy the same bandwidth. the staggered alignment of the even and odd bit streams in oqpsk signal does not change the nature of spectrum.

Answer: false

Explaination:
oqpsk signal perform better than qpsk in the presence of phase jitter. it is due to the presence of noisy reference signal at the receiver.

Answer: envelope detection

Explaination:
there are various types of detection techniques used for the detection of π/4 qpsk signals. they include baseband differential detection, if differential detection and fm discriminator detection.

Answer: mpsk

Explaination:
m-ary phase shift keying (mpsk) is a combined linear and constant envelope technique. it is a part of m-ary modulation techniques. these modern modulation techniques exploit the fact that digital baseband data may be sent by varying both the envelope and phase of an rf carrier.