GATE ECE
Communications
Analog Communication Systems
Previous Years Questions

## Marks 1

Consider an FM broadcast that employs the pre-emphasis filter with frequency response $${H_{pe}}(\omega ) = 1 + {{j\omega } \over {{\omega _0}}}$$, wh...
For a superheterodyne receiver, the intermediate frequency is 15 MHz and the local oscillator frequency is 3.5 GHz. If the frequency of the received s...
A super heterodyne receiver operates in the frequency range of 58 MHz – 68 MHz. The intermediate frequency f1F and local oscillator frequency fL0 are ...
Consider the signal $$s\left(t\right)\;=\;m\left(t\right)\;\cos\left(2{\mathrm{πf}}_\mathrm c\mathrm t\right)\;+\widehat m\left(t\right)\;\sin\left(2\... Consider an FM signal$$f\left(t\right)\;=\;\cos\left[2{\mathrm{πf}}_\mathrm c\mathrm t\;+\;{\mathrm\beta}_1\sin\;2{\mathrm{πf}}_1\mathrm t\;+\;{\math...
Consider an angle modulated signal x(t) = 6cos[2$$\mathrm\pi$$x106 t+2sin(8000$$\mathrm\pi$$t) + 4cos(8000$$\mathrm\pi$$t)] V. The average power of x(...
Consider the amplitude modulated (AM) signal $$A_c\cos\omega_ct\;+\;2\cos\omega_mt\;\cos\omega_ct$$. For demodulating the signal using envelope detect...
Which of the following analog modulation scheme requires the minimum transmitted power and minimum channel bandwidth?
An AM signal is detected using an envelope detector. The carrier frequency and modulating signal frequency are 1 MHz and 2 KHz respectively. An approp...
An AM signal and a narrow-band FM signal with identical carriers, modulating signals and modulation indices of 0.1 are added together. The resultant s...
A 1 MHz sinusoidal carrier is amplitude modulated by a symmetrical square wave of period 100 µsec. Which of the following frequencies will NOT be pres...
A modulated signal is given by, $$s\left(t\right)=m_1\left(t\right)\cos\left(2{\mathrm{πf}}_\mathrm c\mathrm t\right)\;+m_2\left(t\right)\sin\left(2{\... The image channel selectivity of super heterodyne receiver depends upon A DSB-SC signal is generated using the carrier$$\cos\left(\omega_ct\;+\;\theta\right)$$and modulating singal x(t). The envelope of the DSB-SC signal...$$v\left(t\right)\;=5\left[\cos\left(10^6\mathrm{πt}\right)\;-\;\sin\left(10^3\mathrm{πt}\right)\times\sin\left(10^6\mathrm{πt}\right)\right]$$repres... ## Marks 2 The un-modulated carrier power in an AM transmitter is 5kW. This carrier is modulated by a sinusoidal modulating signal. The maximum percentage of mod... A modulating signal given By$$x\left(t\right)=5\sin\left(4\mathrm\pi10^3\mathrm t\;-\;10\mathrm{πcos}2\mathrm\pi10^3\mathrm t\right)$$V is fed to a ... In the system shown in figure (a), m(t) is a low-pass signal with bandwidth W Hz. The frequency response of the band-pass filter H(f) is shown in figu... The signal m(t) as shown is applied both to a phase modulator (with kp as the phase constant) and a frequency modulator (with kf as the frequency cons... The signal$$\cos\;\omega_ct\;+\;0.5\;\cos\;\omega_mt\;s\mathrm{in}\;\omega_ct$$is A Hilbert transformer is a The diagonal clipping in Amplitude Demodulation (using envelope detector) can be avoided if RC time-constant of the envelope detector satisfies the fo... A device with input x(t) and output y(t) is characterized by: y(t) = x2(t). An FM signal with frequency deviation of 90 kHz and modulating signal band... A carrier is phase modulated (PM) with frequency deviation of 10 kHz by a single tone frequency of 1 kHz. If the single tone frequency is increased to... Two sinusoidal signals of same amplitude and frequencies 10 kHz and 10.1 kHz are added together. The combined signal is given to an ideal frequency de... A DSB-SC signal is to be generated with a carrier frequency fc = 1MHz using a nonlinear device with the input-output characteristic$$v_0=a_0v_i\;+\;a...
Let $$m\left(t\right)\;=\cos\left[\left(4\mathrm\pi\times10^3\right)t\right]$$ be the message signal and $$c\left(t\right)\;=5\cos\left[2\mathrm\pi\ti... Let$$m\left(t\right)\;=\cos\left[\left(4\mathrm\pi\times10^3\right)t\right]$$be the message signal and$$c\left(t\right)\;=5\cos\left[2\mathrm\pi\ti...
In an FM system, a carrier of 100 MHz is modulated by a sinusoidal signal of 5 KHz. The bandwidth by Carson’s approximation is 1 MHz. If y(t) = (modul...
Which of the following demodulator(s) can be used for demodulating the signal x(t)\;=\;5\left(1+2\;\cos200\mathrm{πt}\right)\cos\;20000\;\mathrm{πt}...
A superheterodyne radio receiver with an intermediate frequency of 455 KHz is tuned to a station operating at 1200 KHz. The associated image frequency...
The maximum power efficiency of an AM modulator is
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