Lab 1: DSBSC Exp

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Questions and Answers

What is the purpose of the Zero-Order-Hold block in the configuration?

It generates carrier signals for transmission.

It holds the last value of the signal until the next sample.

It is used to display the spectrum for continuous signals.

It converts continuous signals to discrete signals. (correct)

What should be unchecked in the Scope settings to adjust data logging?

Show Data Points

Log Simulation Time

Limit Data Points (correct)

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What is the purpose of the Spectrum Analyzer in this configuration?

To hold the amplitude of the signal constant.

To visualize the frequency spectrum of the signal. (correct)

To amplify the output signal.

To transform signals from one waveform to another.

Which waveform type is used for both the message signal and the TX carrier?

Sine Signup and view all the answers

What is the purpose of adjusting the phase shift in the PHASE SHIFTER module?

To introduce controlled phase errors for analysis Signup and view all the answers

Which of the following correctly describes the process to measure the 3-dB cutoff frequency?

Use the TTL output of the filter and divide the frequency counter reading by 100 Signup and view all the answers

What is the expected outcome when the Phase Shifter module's Phase Adjust control is set to maximize the recovered message?

The phase error is likely 0° Signup and view all the answers

What is the maximum gain setting recommended for the Tunable Low-pass Filter module in this setup?

Middle of its travel Signup and view all the answers

How can one calculate the phase difference between two carriers in this experiment?

Using the equation ∆𝜃 = ∆t × TPeriod Signup and view all the answers

What happens to the recovered message when the Phase Adjust control is set to cause the phase error to increase?

The message becomes distorted or unclear Signup and view all the answers

Which of the following best describes the Low-pass Filter's function in this experiment?

To attenuate frequencies above a specified cutoff Signup and view all the answers

During the lab work with SIMULINK, what is the focus of the DSBSC Modulation experiment?

To simulate a DSBSC modulator-demodulator Signup and view all the answers

What is the formula for the DSBSC modulated wave when the modulating wave is a single tone?

$s(t) = \frac{1}{2} A_c A_m ext{cos}(2 ext{π}(f_c - f_m)t) + \frac{1}{2} A_c A_m ext{cos}(2 ext{π}(f_c + f_m)t)$ Signup and view all the answers

What does the lower sideband (LSB) frequency in DSBSC modulation refer to?

The frequency components below the carrier frequency Signup and view all the answers

What is the transmission bandwidth of a DSBSC signal when the message signal is band-limited to 'W' Hz?

2W Hz Signup and view all the answers

Which of the following statements about DSBSC demodulation is correct?

The modulated signal should be multiplied by a signal in phase and frequency with the carrier. Signup and view all the answers

What is required in the demodulation process of DSBSC to recover the baseband signal?

Low-pass filtering after multiplication Signup and view all the answers

How is DSBSC modulation achieved mathematically?

By multiplying the message signal with the carrier signal Signup and view all the answers

What happens to the spectral components of the DSBSC modulated signal?

They are present at both frequencies surrounding the carrier Signup and view all the answers

In a DSBSC modulation, which component does the term $A_c A_m$ represent?

The amplitude of the carrier and the modulating signal Signup and view all the answers

What is the primary objective of the experiment involving DSBSC modulation and demodulation?

Implement the DSBSC modulator and demodulator using specific tools Signup and view all the answers

What is a key characteristic of Double Sideband Suppressed Carrier (DSBSC) modulation?

The carrier signal is suppressed or not transmitted Signup and view all the answers

In the context of DSBSC demodulation, what primarily influences the success of the demodulation process?

The phase relationship between the modulated signal and the carrier Signup and view all the answers

What is a common application of DSBSC modulation in telecommunication systems?

Broadcasting audio signals Signup and view all the answers

What is the effect of phase shift on DSBSC signals during modulation?

It may distort the demodulated output Signup and view all the answers

What is the primary purpose of the product demodulator in the context of DSBSC modulation?

To extract the message signal from the DSBSC wave Signup and view all the answers

What is the output of the product modulator given by the equation?

$v(t) = A^2_c cos(φ) m(t) + cos(4 heta + φ) m(t)$ Signup and view all the answers

What is the effect of setting the phase difference φ to ±90° in the demodulation process?

It causes the demodulated signal amplitude to be zero Signup and view all the answers

Which component is essential for passing the output signal to extract the desired message signal?

Low-Pass Filter Signup and view all the answers

What happens to the demodulated signal if the local oscillator signal and the carrier signal are out of phase?

The amplitude of the demodulated signal decreases Signup and view all the answers

What component is characterized by an adjustable cutoff frequency in the experimental setup?

Tunable Low-pass Filter Signup and view all the answers

Why is it important for the local oscillator and the carrier signal to be in phase during demodulation?

To achieve maximum demodulated signal amplitude Signup and view all the answers

In the equation for the product modulator output, which term represents the message signal after filtering?

$rac{A^2_c}{2} cos(φ) m(t)$ Signup and view all the answers

Study Notes

DSBSC Modulation and Demodulation

The experiment focuses on Double Sideband Suppressed-Carrier (DSBSC) modulation and demodulation.
DSBSC is a type of Amplitude Modulation (AM) where the carrier signal is suppressed, reducing power consumption.
DSBSC modulation is achieved by multiplying the message signal with a carrier signal.
The modulated signal contains two sidebands: upper sideband (USB) and lower sideband (LSB).
The transmission bandwidth for DSBSC is twice the highest frequency present in the message signal.
DSBSC demodulation is performed coherently, using a local carrier signal synchronized with the original carrier.
The demodulated signal is extracted by passing the multiplied signal through a low-pass filter.
The demodulated signal's amplitude is maximum when the local carrier is in phase with the original carrier, and zero when they are in quadrature.

Practical Implementation

The experiment utilizes the Emona Telecoms-Trainer and Simulink for practical implementations.
TIMS (Telecoms-Trainer Modules) includes components like Audio Oscillator, Multiplier, Utilities, Tunable Low-pass Filter, and Phase Shifter.
Simulink facilitates building a virtual model for DSBSC modulation and demodulation.

Effects of Phase Shift

Introducing a controlled phase error between the transmitter and receiver carrier signals impacts demodulation.
A phase error can significantly reduce the recovered message signal amplitude, especially at 90° phase difference.
Adjusting the phase shifter allows observing the effect of different phase errors on the demodulated signal.

Simulink Implementation

Simulink utilizes blocks like Sine Wave, Multiplier, Product, Scope, Spectrum Analyzer, and Zero-Order-Hold for modeling.
Message and carrier signals are sine waveforms with specific parameters specified.
The Zero-Order-Hold block is crucial for displaying the spectrum of a continuous signal within Simulink.
Scope and Spectrum Analyzer provide visual representations of the signals in time and frequency domains.

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Description

This quiz explores the concepts of Double Sideband Suppressed-Carrier (DSBSC) modulation and demodulation. It covers the principles, implementation, and practical aspects, including the use of Emona Telecoms-Trainer and Simulink. Test your understanding of the modulation techniques and their applications in telecommunications.