Baseband Modulation MCQ [Free PDF] – Objective Question Answer for Baseband Modulation Quiz

Answer.2. TDM

Explanation:-

Multiplexing is the process of combining multiple signals into one signal, over a shared medium.

If the analog signals are multiplexed, then it is called analog multiplexing. Similarly, if the digital signals are multiplexed, then it is called digital multiplexing.

Types of Multiplexing:

(1) Analog Multiplexing

• Frequency Division Multiplexing
• Wavelength Division Multiplexing

(2) Digital Multiplexing

• Time Division Multiplexing
  • Synchronous TDM
  • Asynchronous TDM

Analog Multiplexing:

The signals used in analog multiplexing techniques are analog in nature. The analog signals are multiplexed according to their frequency (FDM) or wavelength (WDM).

Frequency Division Multiplexing

• • In analog multiplexing, the most used technique is Frequency Division Multiplexing (FDM).
  • This technique uses various frequencies to combine streams of data, for sending them on a communication medium, as a single signal.
  • Example − A traditional television transmitter, which sends a number of channels through a single cable uses FDM.

Wavelength Division Multiplexing

• • Wavelength Division Multiplexing (WDM) is an analog technique, in which many data streams of different wavelengths are transmitted in the light spectrum.
  • If the wavelength increases, the frequency of the signal decreases.
  • A prism, which can turn different wavelengths into a single line, can be used at the output of MUX and input of DEMUX.
  • Example − Optical fiber communications use WDM technique, to merge different wavelengths into a single light for communication.

Answer.1. 108 × 10⁶

Explanation:-

Bit rate in PCM

This indicates how many number of bits are generated by the encoder per second and it is defined as:

R_b = n/T_s = sampling rate × n bits/sec

R_b = n × f_s

Calculation:

The bandwidth of the signal is 4.5 MHz and 1024 levels.

1024 levels = 10 bits

Maximum frequency is 4.5 MHz

The bitrate is:

R_b = 10 × (1.2)(2 × 4.5 MHz)

R_b = 10 × 10.8 × 10⁶

R_b = 108 × 10⁶

Answer.1. Baseband Modulation

Explanation:-

Baseband modulation represents digital sequences by pulse waveforms that are suitable for baseband transmission. Baseband modulation waveforms are also called line codes or PCM codes.

A line code is a code used for data transmission of a digital signal over a transmission line. This process of coding is chosen so as to avoid overlap and distortion of signals such as inter-symbol interference.

Answer.2. Pulse Code Modulation

Explanation:-

In PCM, the modulating signal 1s sampled and the amplitude of each sample is rounded off to the nearest one of the finite set of allowable values, then a binary digit is generated, which is proportional to the rounded-off value, and the binary digits are transmitted.

• It is used in voice, audio, and CD recording.
• PCM system doesn’t use the previous samples in its processing of information.

Answer.4. Get almost uniform S/N ratio

Explanation:-

• Companding refers to a technique for compressing and then expanding (or decompressing) an analog or digital signal.
• For digital audio signals, companding is used in pulse code modulation (PCM)
• The process involves decreasing the number of bits used to record the strongest (loudest) signals
• In the digital file format, companding improves the signal-to-noise ratio at reduced bit rates, it gets the almost uniform signal to noise ratio

Answer.4. M-ary

Explanation:-

1. When pulse-modulation is applied to binary symbols, the resulting binary waveform is called a pulse-code modulation (PCM) waveform.
2. When pulse-modulation is applied to non-binary symbols, the resulting waveform is called an M-ary pulse- modulation waveform.
3. An M-ary transmission is a type of digital modulation where instead of transmitting one bit at a time, two or more bits are transmitted simultaneously. This type of transmission results in reduced channel bandwidth.

Answer.1. 2 times

Explanation:-

The number of levels for an n-bit PCM system is given by:

L = 2n

Also, the bandwidth of PCM is given by:

BW = nf_s

n = number of bits to encode

fs = sampling frequency

Calculation:

For n = 8, the bandwidth will be:

B.W. = 8 fs

Similarly, For n = 16, the bandwidth will be:

B.W. = 16 fs

We observe that the Bandwidth is increased by 2 times.

Answer.2. 48 dB

Explanation:-

The Signal to Noise (SNR) Ratio for a PCM system is given by:

SNR = 1.8 + 6n dB

Where ‘n’ is the number of bits per sample.

Calculation:

For n + 8 number of bits, the Signal to Noise Ratio will be:

1.8 + 6 ×(n + 8) dB

So the SNR would increase by:

1.8 + 6 × n  – [1.8 + 6 × (n + 8)]

= 48 dB

Answer.4. All of the mentioned

Explanation:-

When pulse modulation is applied to a binary symbol, the resulting binary waveform is called a PCM waveform. There are several types of PCM waveforms. In telephony applications, those waveforms are often called /line codes.

When pulse modulation is applied to a non-binary symbol, the resulting waveform is called M- ary pulse modulation waveform.

PCM waveforms fall into the four primary groups:

(i) non- return-to-zero (NRZ) PCM;

(ii) return-to-zero (RZ) PCM;

(iii) phase encoded PCM;

(iv) multilevel binary PCM.

Answer.3. 8 kHz

Explanation:-

The bandwidth of a PCM system for an encoded signal sampled at a frequency of fs is given by:

Bit rate = n fS

fS = Sampling frequency

n = number of bits used for encoding.

n is related to the number of quantization levels (L) as:

L = 2n

n = log2 L

Calculation:

the maximum frequency for the signal will be 4 kHz.

n = 10 bits, R_b = 60 Kbits/sec

Bit rate = n fS

f_s = 6 kHz

And f_m is given as 4 kHz i.e

f_s ≥ 2f_m

f_s ≥ 8 kHz

So, f_s = 6kHz leads to undersampling.

Hence, options 1 and 2 can’t be correct.

Option 4: f_s = 9 kHz leads to oversampling

Hence, option 3 is correct f_s = 8 kHz

∴ The appropriate value of the sampling frequency (fs) will be 8 kHz