Download JNTUA B.Tech 4-2 R15 2019 July Advanced Supple 15A04804 RF Integrated Circuits Question Paper

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Code: 15A04804

B.Tech IV Year II Semester (R15) Advanced Supplementary Examinations July 2019

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RF INTEGRATED CIRCUITS

(Electronics & Communication Engineering)

Time: 3 hours Max. Marks: 70

PART - A

(Compulsory Question)

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1 Answer the following: (10 X 02 = 20 Marks)

1. Calculate the resonant frequency of a parallel RLC tank, given L = 1 nH, C = 1 pF.
2. State skin effect.
3. Write the wave equation in one space dimension.

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4. In an open-circuit time constant if R₁ = R₂ = 10 kO and C₁ = C₂ = 100 pF, what are the pole frequencies?
5. Having the noise factor, F = SNR_i / SNR_o give the expression to find noise figure.
6. Differentiate between power match and noise match.
7. In a VCO if CM change at X and Y is indistinguishable from a change in V_cont, then what will be the change in the oscillation frequency?
8. While constructing a charge-pump PLL using PFD/CP, the loop ideally forces the input phase error to zero. Justify your answer.

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9. Define fractional frequency.
10. List out some advantages of GSM radio architectures.

PART - B

(Answer all five units, 5 X 10 = 50 Marks)

UNIT - I

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3 (a) Draw the phasor diagram for a parallel RLC circuit. And derive the expression for impedance and current triangle of the circuit.

(b) Differentiate between Pi match and T match.

OR

4 Why does the skin effect occur? Mention the factors affecting skin effect in a conductor carrying a.c current.

UNIT - II

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5 An air-filled 50O coaxial line has a loaded VSWR of 3.3 at a frequency of 3 GHz. Replacing the load with a short cause the voltage minimum to move 1.0 cm towards the generator. What is the normalized load impedance?

OR

6 In the folded cascade circuit shown in figure below, all transistors have the same µCox (W/L), the same ? and I_D2 = 2I_D1. Find the gain and the output resistance of the amplifier (in terms of g_m1 and r₀₁ only).

[Image Description: A circuit diagram with transistors Q1, Q2, Q3, Q4, Q5, voltage sources VDD, VG2, VG3, VG4, and output Vas]

UNIT - III

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7 Lay out an LNA and connect its input to a pad through a metal line with the length of 200µm and width of 0.5µm. By assuming a noise figure of 2dB for the LNA and a sheet resistance of about 40 mO for the metal line determine the overall noise figure. Neglect the input-referred noise current of the LNA.

OR

8 Which device is used to convert baseband frequency to a higher IF or RF frequency for efficient transmission in transs? Explain its operation in detail.

UNIT - IV

9 (a) Which amplifier operates linearly across the full input and output range while the transistors remain ON? Explain in detail with necessary equations.

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(b) Write a brief note on resonators.

OR

10 (a) If the input frequency changes by ?, how much is the change in the phase error? Assume the loop remains lock.

UNIT - V

11 (a) During synthesizer settling, the power amplifier in a transmitter is turned OFF. Explain why?

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(b) Compute the required reference frequency and range of divide ratios for an integer-N synthesizer designed for a Bluetooth receiver for direct conversion and sliding-IF down conversion with f_LO=(2/3) f_RF.

OR

12 Explain in detail about GSM radio architectures and list out its advantages and disadvantages.

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