Test: Communication Systems - 6 - Electronics and Communication Engineering (ECE) MCQ

Dolby system of noise reduction divides the total audio spectrum into

In a system an input resistance of 20 kΩ causes a noise voltage of 15μV. If two such input resistances each of 20 kΩ are used in parallel, the total noise voltage will be about

In the television system in India, the odd and even fields are scanned

Consider the following

1. A signal f(t) and its Hilbert transform f_h(t) have the same energy density spectrum
2. A signal f(t) and its Hilbert transform, f_h(t) have the same auto correlation function
3. A signal f(t) and its Hilbert transform are mutually orthogonal

Vidicon and plumbicon operate on the principle of

The typical squelch circuit

A TV receiver has a width of 60 cm. The aspect ratio is 4/3. The required EHT supply is about

A narrow band noise n(t) has symmetrical spectrum and has power density spectrum 0.2 x 10^-6. The power density of quadrature component is

The radio receivers mostly used now a days are

The reactance of coupling capacitors, for DC quantities, is

An AM wave is given by s(t)_AM = 20 (1 + 0.5 cos 10³t + 0.3 cos 10⁴ t cos 10⁶ t) the modulation index of the envelope is

The modulating frequency in frequency modulation is increased from 10 kHz to 30 kHz. The bandwidth is increased by

A sinusoidal signal with peak to peak amplitude of 1.536 volt is quantized into 128 levels using a mid-rise uniform quantizer. The quantization noise power is

An FM wave is made to pass through a frequency tripler. If original modulation index is m_f, the output of tripler has a modulation index equal to

A balun provides an impedance transformation of

A signal m(t) with bandwidth 500 Hz is first multiplied by a signal g(t) where . The resulting signal is then passes through an ideal low pass filter with bandwidth 1 kHz the output of the low pass filter would be

If γ = (S₀/N₀)/(S_i/N_m) where S₀ and S₁ are signal power output and signal power input and N₀ and N_m are noise power output and noise power input, the value of γ for SSB-SC and DSB-SC amplitude modulated system respectively are

Consider the draw backs

1. Slope overload
2. Serration noise
3. Granular noise

It is required to increase the maximum range of a radar by a factor of two. The peak power transmitted in the radar system has to be increased by a factor of

A source generates three symbols with probabilities 0.25, 0.25, 0.50 at a rate of 3000 symbols per second. Assuming independent generation of symbols, the most efficient source encoder would have average bit rate is as

Armstrong F.M. transmitter performs frequency multiplication in stages

The filter circuit for feeding tweeter has