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Electronics Engineering Objective Questions { Digital Communication System }

232. In a PCM system, if the code word longth is increased from 6 to 8 bits, the signal to quantization noise ratio improves by the factor
A. 8/6
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233. In the output of a DM speech encoder, the consecutive pulses are of opposite polarity during time interval t1
A. the input to the modulator is essentially constant
B. the modulator is going through slope overload
C.the accumulator is in saturation the speech signal is being sampled at the Nyquist rate
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234.  A 1 kHz sinusoidal signal is ideally sampled at 1500 samples/sec and the sampled signal is passed through an ideal low-pass filter with cut-off frequency 800 Hz. The output signal has the frequency (a) zero Hz
A.1 kHz
B.0.25 kHz
C. 0.5 kHz
D.0.75 kHz
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235. The free space transmission loss depends on I. Height of Satellite 2. Downlink frequency 3. Gain of transmitting antenna 4. Gain of receiving antenna
A. 1 and 3
B. 1 and 2
C. 2 and 3
D. 3 and 4
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236. Consider a binary digital communication system with equally likely O's and I's. When binary 0 is transmitted the voltage at the detector input can lie between the levels ? 0.25 V and + 0.25 V with equal probability : when binary 1 is transmitted, the voltage at the detector can have any value between 0 and 1 V with equal probability. If the detector has a threshold of 2.0 V (i.e., if the received signal is greater than 0.2 V, the bit is taken as 1), the average bit error probability is
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237. Choose the correct one from among the alternatives A, B, C, D after matching an item from Group 1 with the most appropriate item in Group 2. 1 : FM-P : Slope overload,2: DM-Q:,3 : PSK-R: Envelope detector,4: PCM-S : Capture effect,1: Hilbert transform U : Matched filter
A. 1-1, 2-P, 3-U, 4-S
B. 1-S, 2-U, 3-P, 4-T
C. 1-S, 2-P, 3-U, 4-Q
D. 1-U, 2-R, 3-S, 4-Q
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238. A source produces binary data at the rate of 10 kbps. The binary symbols are represented as shown in the figure 11.6 given below.The source output is transmitted using two modulation schemes, namely Binary PSK (BPSK) and Quadrature PSK (QPSK). Let B1 and B2 be the bandwidth requirements of BPSK and QPSK respectively. Assuming that the bandwidth of the above rectangular pulses is 10 kHz, B1 and B2 are
A. B1 20 kHz, B2 = 20 kHz
B. B1 = 10 kHz, B2= 20 kHz
C.B1 = 20 kHz, B2= 10 kHz
D. B1 = 20 lcHz, B2= 10 kHz
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