Question

DSB-SC signals are generated using:

• A. Diode detector
• B. Balanced modulator
• C. Envelope detector
• D. Mixer

Hint:

Important communication systems facts: \[ \text{AM generation} \rightarrow \text{Standard modulator} \] \[ \text{DSB-SC generation} \rightarrow \text{Balanced modulator} \] \[ \text{AM detection} \rightarrow \text{Envelope detector} \]

Answer 1

The Correct Option is B

Concept: DSB-SC stands for: \[ \text{Double Sideband Suppressed Carrier} \] In DSB-SC modulation:
• The carrier component is suppressed.
• Only upper and lower sidebands are transmitted.
• Power efficiency improves because carrier power is not transmitted. To generate DSB-SC signals, the modulating signal and carrier signal are multiplied together using a balanced modulator. A balanced modulator:
• Cancels the carrier component
• Produces only sideband frequencies
• Acts as a product modulator

Step 1: Understand DSB-SC modulation. The standard DSB-SC signal is: \[ s(t)=A_cm(t)\cos \omega_ct \] where:
• \(m(t)\) is message signal
• \(\cos \omega_ct\) is carrier Notice that:
• Carrier alone does not appear separately.
• Only the product term exists. Hence, carrier suppression is required.

Step 2: Analyze the balanced modulator. A balanced modulator performs multiplication of: \[ m(t)\times \cos \omega_ct \] while simultaneously cancelling the pure carrier component. Therefore:
• Upper sideband is generated
• Lower sideband is generated
• Carrier is suppressed Thus, balanced modulators are specifically designed for DSB-SC generation.

Step 3: Analyze the incorrect options.
• Diode detector is used for AM demodulation.
• Envelope detector is also used for AM detection, not DSB-SC generation.
• Mixer can perform frequency translation but balanced modulators are the standard answer for DSB-SC generation. Hence, these are incorrect choices.

Step 4: Write the final answer. Therefore, DSB-SC signals are generated using: \[ \boxed{\text{Balanced Modulator}} \] Hence, the correct option is: \[ \boxed{(B)\ \text{Balanced modulator}} \]