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Right option is (b) Spectrum analyzer

To explain: The test instrument for producing a frequency-domain display is the spectrum analyzer. Like the OSCILLOSCOPE, the spectrum analyzer uses a cathode-ray tube for display, but the horizontal sweep AXIS is CALIBRATED in hertz and the VERTICAL axis is calibrated in VOLTS or power units or decibels.

Right option is (a) True

For explanation I would say: FOURIER analysis allows us to DETERMINE not only the SINE wave components in any complex signal but ALSO how much bandwidth a particular signal occupies. Although a sine or cosine wave at a single FREQUENCY theoretically occupies no bandwidth, complex signals obviously take up more spectrum space.

Right option is (a) True

The best explanation: A square wave is made up of a sine wave at the FUNDAMENTAL frequency of the square wave plus an infinite number of ODD harmonics. For example, if the fundamental frequency of the square wave is 1 kHz, the square wave can be SYNTHESIZED by adding the 1-kHz sine wave and harmonic sine WAVES of 3 kHz, 5 kHz, 7 kHz, 9 kHz, etc.

Correct CHOICE is (a) 14Khz

Best EXPLANATION: The frequency of 7^th harmonic sine wave = 7 x 2KHZ = 14KHz.

Correct choice is (a) Roll off

The EXPLANATION is: Roll off is also called the ATTENUATION rate, roll-off is the rate of change of amplitude with frequency in a filter. The faster the roll-off, or the higher the attenuation rate, the more selective the filter is, i.e., the better able it is to DIFFERENTIATE between two closely spaced signals, one desired and the other not.

Right answer is (C) Harmonic

Explanation: A harmonic is a SINE wave whose frequency is some integer multiple of a fundamental sine wave. The third harmonic of a 2-KHZ sine wave is a sine wave of 6 kHz.

Correct answer is (a) True

Explanation: NOTCH filters are also referred to as bandstop or band REJECT filters. Band-reject filters are used to greatly attenuate a NARROW range of frequencies around a center point. Notch filters accomplish the same purpose, but for a SINGLE FREQUENCY.

Right OPTION is (a) Low pass filter

Easiest explanation: A low-pass filter can also be implemented with an inductor and a RESISTOR. At very low frequencies, the inductor has very low reactance compared to the resistance and therefore the ATTENUATION is minimum.Thus allowing lower frequencies to pass through while attenuating higher frequency signals.The cutoff frequency is determined by using the formula FCO = R/2πL.

The correct answer is (b) High PASS filter

The explanation: An RC coupling circuit is an example of a high-pass filter because the AC component of the INPUT voltage is DEVELOPED across R and the DC voltage is BLOCKED by the series capacitor. FURTHERMORE, with higher frequencies in the AC component, more AC voltage is coupled.

Right OPTION is (d) All pass filters

Explanation: An all pass FILTER passes all frequencies equally well over its design range but has a FIXED or PREDICTABLE phase shift characteristic. Filters normally attenuate the SIGNAL applied for some values of frequency whereas an all pass filter retains the signal level at all frequencies.

The correct choice is (b) Passive FILTERS

To elaborate: Simple filters created by using resistors and CAPACITORS or inductors and capacitors are CALLED passive filters because they use passive components that do not amplify. In communication work, MANY filters are of the passive LC variety, although many other types are USED.

The correct answer is (b) 4522Ω

Explanation: Inductive REACTANCE = XL=2πfL = 2 X 3.14 x 18 x 10^6 x 40 x 10^-6 = 4522Ω.

The correct answer is (a) Increases

To explain: Inductive reactance is DIRECTLY PROPORTIONAL to the operating FREQUENCY and is given by the formulaXf= 2πfL where L is the INDUCTANCE value in Henry.

Correct answer is (d) Increases with less capacitance VALUE

To ELABORATE: The lead WIRES of capacitors behave as a complex RLC circuit and GENERATE stray capacitance. This can be reduced by shortening the length of the lead wires or using chip capacitors. HOWEVER, decreasing or increasing the value of capacitance does not affect stray capacitance.

Correct choice is (b) 700.16Ω

For EXPLANATION: Capacitative reactance =XC= 1/2πfC = 1/(2 X 3.14 x 2 x 10^6 x 100 x 10^-12) = 796.2Ω.

The correct choice is (a) True

The explanation: In an ac power supply the VOLTAGE increases and decreases with a particular frequency. During the first HALF cycle, the capacitor gets CHARGED and in the other half, it gets discharged. The same process repeats throughout the wave.

The correct ANSWER is (a) Phase of voltage leads the current

For EXPLANATION: In addition to a resistance of alternating current flow, an inductor/coil alters the phase DIFFERENCE between the current and voltage. The inductor/coil lowers the phase of the current and hence the voltage leads the current.

The CORRECT answer is (B) Phase of current leads the VOLTAGE

Explanation: In addition to resistance of alternating current FLOW, a capacitor alters the phase difference between the current and voltage. The capacitor lowers the phase of the voltage and HENCE the current leads the voltage.

Correct answer is (a) dBm

Explanation: When the gain or attenuation of a circuit is expressed in DECIBELS, implicit is a comparison between two values, the output and the input. An often USED reference level in communication is 1 MW. When a decibel value is COMPUTED by comparing a power value to 1 mW, the result is a value called the dBm. It is computed with the STANDARD power decibel formula with 1 mW as the denominator of the ratio.

The correct OPTION is (B) 64

Best EXPLANATION: DB = 20 log(5/0.003) = 20 log 1666.67 = 20 x 3.22 =64.4.

The correct ANSWER is (c) Resistance offered to ac current by coil and capacitance

To elaborate: Both coils and capacitors offer an OPPOSITION to alternating current flow known as reactance, which is expressed in ohms. LIKE resistance, reactance is an opposition that directly affects the amount of current in a CIRCUIT.

The CORRECT option is (c) 2

Best explanation: For the signal to have zero voltage LOSS gain of the attenuator, AMPLIFIER combination must be 1. Attenuation x gain =1. Gain = 1/attenuation = 1/(0.5) = 2.

The correct choice is (c) 200Ω

Explanation: ATTENUATION =R2/(R2+R1) = 0.5

R2 = (0.5 X R2) + (0.5 X R1)

(0.5 X R2) = 100Ω

R2= 100/0.5 = 200Ω.

Correct choice is (a) True

The explanation: The gain or loss of a circuit is USUALLY EXPRESSED in decibels (dB), a unit of measurement that was ORIGINALLY created as a way of EXPRESSING the hearing response of the HUMAN ear to various sound levels. A decibel is one-tenth of a bel.

The correct choice is (b) 1

For explanation: An amplifier is usually used to INCREASE the OUTPUT VOLTAGE of a SIGNAL. Since gain = output voltage/INPUT voltage and the input voltage is equal to the output voltage, the gain of the amplifier must be 1.

Right option is (b) 16.6

Easy explanation: TOTAL gain = 1.5×10^-3/30×10^-6 = 50 = STAGE 1 gain X stage 2 gain

Stage 2 gain = 50 / 3 = 16.6.

Correct answer is (d) 240

The BEST I can explain: TOTAL gain = product of individual gains = 6 x 8 X5 = 240.

Correct option is (C) 400mV

For EXPLANATION I would say: GAIN = output signal VOLTAGE / input signal voltage

Output signal amplitude = 20 x 0.02 = 400mV.

The CORRECT OPTION is (a) 14000

Best explanation: GAIN = output VOLTAGE/input voltage = 700/0.05 = 14000.

The correct answer is (b) AMPLIFIER

Easy EXPLANATION: An amplifier is a component that increases the amplitude of the input SIGNAL. The increase in amplitude is measured as gain. Gain is the RATIO of the voltage of the input signal VS output signal.