Solution Of Assignment 1

Communication System II (Solution of Assignment number 1) 1. A 107.6-MHz carrier is frequency modulated by a 7-kHz sine wave. The resultant FM signal has a frequency deviation of 50kHz. (a) Find the carrier swing of the FM signal. (b) Determine the highest and lowest frequencies attained by the modulating signal. (c) What is the modulation index of the FM wave? [Note: Carrier swing is double of the maximum deviation (c.s. = 2×Δf)]

Syed Muneeb Ahmed

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2. What is the modulation index of an FM signal having a carrier swing of 100 kHz when the modulating signal has a frequency of 8 kHz?

Syed Muneeb Ahmed

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3. A frequency modulated signal which is modulated by a 3-kHz sine wave reaches a maximum frequency of 100.02 MHz and minimum of 99.98 MHz (a) Determine the carrier swing. (b) Find the carrier frequency. (c) Calculate the frequency deviation of the signal. (d) What is the modulation index of the signal?

Syed Muneeb Ahmed

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4. We wish to transmit a 100-character alphanumeric message in 2 seconds, using 7-bit ASCII coding, followed by an eighth bit for error detection per character. The eighth bit is chosen so that the number of ones in the 8 bits is an even number. A multilevel PAM waveform with M=32 levels is used. (a) Calculate the effective transmitted bit rate and the symbol rate. (b) Repeat part (a) for 16-level PAM, eight-level PAM, four-level PAM, and PCM (binary) waveform.

Solution:

5. The information in an analog waveform, whose maximum frequency fm=4000Hz, is to be transmitted using a 16-level PAM system. The quantization must not exceed ±1% of the peak-to-peak analog signal. (a) What is the minimum number of bits per sample or bits per PCM word that should be used in this system? (b) What is the minimum required sampling rate, and what is the resulting bit rate? (c) What is the 16-ary PAM symbol Transmission rate?

Solution:

Syed Muneeb Ahmed

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