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IBIELE-004)
B.Tech. -VIEP -ELECTRONICS AND
COMMUNICATION ENGINEERING (BTECVI)
Term-End Examination
June, 2016
BlELE-004 Rf CIRCUITS
Time: 3 hours Maximum Marks: 70
Note: Attempt any seven questions. Missing data may be suitably assumed. All questions carry equal marks.

1. Describe the RF behaviour of passive components.

Explain the following
Chip Resistors

(ii) Chip Capacitors

(iii) Surface Mounted Inductors 4 6=10

2. What is a transmission line and what is its use in Microwave Engineering Explain various examples of transmission lines.

Starting with basic definition of Standing Wave Ratio show that it can be expressed as

SWR= 1 1 5 5=10

3. Derive the expression of 'Noise Figure' for a Two-port Network and for a Cascaded Multiport Network.

Discuss the noise models for active and passive components. 5 5=10

4. For the circuit shown in Figure assume a lossless line with Z0 75 ohm, ZG 50 ohm and ZL =40 ohm. Compute the input power and power delivered to the load. Give you answer both in W and dBm. Assume the length of the line to be y/2 with a source voltage of VG V. <img src='./qimages/11057-4.jpg'> <br><br>

5. Explain the characteristics of amplifiers.

Explain the amplifier power relations, mentioning RF source, transducer power gain, available power gain and unilateral power gain. 5 5=10

6. Discuss the stability considerations of amplifier design.

Explain large signal performance of a low noise amplifier. 5 5=10

7. Design an 18 dB single-stage ME8FET amplifier operated at 5.7 GHz. A ME8FET operated at 5.7 GHz has the following S-parameters

S11 =0.5 L
S12 0.02 L 0°
S21 =6.5 L 115°
S22 0.6 L Determine if the circuit is unconditionally stable. Find the maximum power gain under optimal choice of the reflection assuming the unilateral design (S12 0). Adjust the load reflection coefficient such that the desired gain is realized using the concept of constant gain circles. 10

8. Explain the principle of basic Oscillator Model and the role of Negative Resistance Oscillator. 5

For a 200 MHz oscillation frequency, a Colpitts BJT oscillator in Common-Emitter configuration has to be designed. For the bias point of VCE 3 V and IC 3 mA, the following circuit parameters are given at a room temperature of 25°C:
CBC =0·1 fF, rBE =2k ohm, rCE =10k ohm,CBE =100 pF. If the inductance should not exceed L3 nH, find the values for the capacitances in the feedback loop.

9. Explain the basic characteristics of mixers, by drawing its block diagram.

Differentiate between single-balanced mixer and double-balanced mixer.

Describe the frequency domain considerations of mixer design. 4 3 3=10

10. Write short notes on any two of the following: 2x5=10 LNA Power Amplifiers Frequency Synthesizers