An audio signal is modulated by a carrier wave of 20MHz

Question:

An audio signal is modulated by a carrier wave of 20MHz such that the bandwidth required for modulation is 3kHz. Could this wave be demodulated by a diode detector which has the values of R and C as

(i) R = 1 kΩ, C = 0.01µF

(ii) R = 10 kΩ, C = 0.01µF

(iii) R = 10 kΩ, C = 0.1µF

Solution:

Carrier wave frequency, fc – 20 MHz = 20 × 106 Hz

Bandwidth = 2fm = 3 × 103 Hz

fm = 1.5 × 103 Hz

1/fc = 0.5 × 10-7

1/fm = 0.7 × 10-3

(i) 1/fc << RC < 1/fm

Therefore, it can be demodulated

(ii) 1/fc << RC << 1/fm

Therefore, it can be demodulated

(iii) 1/fc < RC

Therefore, it cannot be demodulated

Leave a comment

Close

Click here to get exam-ready with eSaral

For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.

Download Now