Principles of Communication Systems Model Question Paper 1

The standard form of amplitude modulation is given by the equation: $s(t) = A_c [1 + m(t)] imes ext{cos}(2 ext{π}f_ct)$, where $A_c$ is the carrier amplitude, $m(t)$ is the message signal, and $f_c$ is the carrier frequency. The term $A_c$ represents the carrier amplitude, $m(t)$ represents the message signal, and $f_c$ represents the carrier frequency.

DSBSC waves are generated using a Ring Modulator by multiplying the message signal by the carrier signal, resulting in the suppression of the carrier and generation of double sidebands.

The frequency content of the AM signal will include the carrier frequency at 1000 KHz, the upper sideband frequencies at 1000.3 KHz, 1000.8 KHz, and 1002 KHz, and the lower sideband frequencies at 999.7 KHz, 999.2 KHz, and 998 KHz.

<p>The VSB modulated wave is generated by suppressing one sideband and transmitting the other along with the carrier. It is demodulated by using a coherent carrier and a synchronous detector. The spectrum of VSB signals includes the carrier and a single sideband, with the other sideband suppressed.</p> Signup and view all the answers

<p>i) The sidebands of DSBSC modulated waves appearing at the two product modulator outputs are at 99.7 KHz and 100.3 KHz. ii) The pass-bands of the two BPF’s are 0 to 200 KHz and 9.8 to 10.2 MHz.</p> Signup and view all the answers

<p>The FDM transmitter combines multiple signals onto a single channel by modulating each signal with a unique carrier frequency. At the receiver, the signals are demodulated and separated using filters.</p> Signup and view all the answers

<p>Carrier frequency: 6 × 10^8 Hz, Modulating frequency: 1250 Hz, Modulation index: 5, Maximum frequency deviation: 75 kHz</p> Signup and view all the answers

<p>The expression for WBFM is given by the modulation index equation. The spectrum of WBFM contains an infinite number of sidebands due to the Bessel function expansion.</p> Signup and view all the answers

<p>i. By Carson’s rule: 150 kHz, ii. By universal curve: 240 kHz</p> Signup and view all the answers

<p>The direct method of FM generation using Hartley Oscillator involves modulating the frequency of the oscillator based on the input signal. This can be explained using the relevant frequency modulation equation and a diagram of the Hartley Oscillator.</p> Signup and view all the answers

<p>The basic block diagram of PLL includes a phase detector, a loop filter, and a voltage-controlled oscillator (VCO). The nonlinear model of PLL can be derived by considering the phase detector and the characteristics of the VCO.</p> Signup and view all the answers

<p>The Figure of Merit for an FM receiver can be derived using the equation involving the signal-to-noise ratio and the minimum detectable signal.</p> Signup and view all the answers

<p>Noise is random unwanted signals that interfere with the communication of information. Noise Equivalent Bandwidth is a measure of the effective noise bandwidth of a system, and it can be calculated using relevant equations.</p> Signup and view all the answers

<p>The FOM of single tone AM can be calculated using the equation involving the modulation index and the signal-to-noise ratio.</p> Signup and view all the answers

<p>The generation of PPM waves involves sampling the input signal and producing pulses based on the sampled values. The detection process includes demodulation and reconstruction of the original signal.</p> Signup and view all the answers

<p>The generation of PAM (Flat-top) involves sampling and quantization of the input signal, followed by the creation of flat-topped pulses. The recovery process includes low-pass filtering to reconstruct the original signal.</p> Signup and view all the answers

<p>Noise in a PPM system can lead to errors in pulse detection and timing, affecting the accuracy of information transmission.</p> Signup and view all the answers

<p>The Sampling theorem states that a continuous signal can be accurately represented by discrete samples if the sampling frequency is at least twice the signal's maximum frequency. Digitizing analog signals is necessary to enable processing, storage, and transmission of the signals using digital systems.</p> Signup and view all the answers

<p>Noise in a Pulse Position Modulation (PPM) system can cause errors in pulse detection, leading to inaccuracies in the transmission of information.</p> Signup and view all the answers

<p>The output Signal to Noise Ratio of a Quantizer can be derived using the equation involving the quantization error and the power of the input signal.</p> Signup and view all the answers

<p>A PCM system consists of a sampler, quantizer, encoder, transmission channel, decoder, and reconstruction filter. These elements work together to digitize, transmit, and reconstruct analog signals.</p> Signup and view all the answers

<p>a. Nyquist rate: 30 kHz, b. Number of bits required: 16 bits, c. Quantization step: 0.0000305 volts</p> Signup and view all the answers