# RTU Previous Exam Papers BE EC 5 th Semester

# Telecommunication Engineering Dec-2011

**UNIT – I**

1. (a) Prove that a finite transmission line terminated in its characteristic impedance behaves as a infinite transmission line.

(b) A transmission line has the following per unit length parameters, R – 5 Q, L = 0.1 juH» C = 300 pF, G = 0.01 mho. Calculate the propagation constant and characteristiot impedance of the line at 500 MHz, obtain the same parameters for the lossless line.

**OR**

1. (a) Impedance measurements made on a 0.25 km field quad cable at 1600 Hz under open and short circuit conditions gave Z_{oc} = 2460 Z-86.3* and Z_{gc} = 215 Z14° O results. Calculate Z_{G}, a,j3 and line parameters per unit length of line.

(b) Describe the types of losses that may occur with high frequency transmission lines. »

**UNIT – II**

2. (a) What is stubs ? Describe the single and double stubs phenomena in transmission line.

(b) A lossless transmission line with characteristic impedance 75 Q and of electrical length 0.3 X is terminated with load impedance of (40 + j20) Q. Determine the reflection coefficient of load, SWR of line and input impedance of the line.

**OR**

Derive the relationship between standing wave ratio and the reflection coefficient.

Describe the properties and application of Smith chart used in transmission line.

**UNIT – III**

3. (a) Derive the characteristic impedance and propagation constant of bridge-T phase equalizer network.

(b) Design a minimum loss attenuator to match between 70 Q and 50 Q line. Determine the value of loss produced by the network.

**OR**

(a) Design th-derived T-type low pass filter to wdrk into 16ad of 500 Q and cut-off frequency at 4 kHz and peak attenuation at 4.5 kHz.

(b) For band pass filter show that series and shunt arm resonant frequency is the geometric mean of two cut-off frequencies ‘fj’ and ‘f_{2}’ deciding pass band.

**UNIT – IV**

4. (a) Draw and explain the signalling tones used in telephone.

(b) A four wire circuit has an overall loss of 1 dB and the balance return loss at each end is 6 dB. Find, the singing point, stability margin and attenuation of talker and listener echo,

**OR**

4 (a) Draw and explain the working of electronic telephone system.

(b) Compare TDM and FDM, suggest which multiplexing system being used in general and why ?

**UNIT – V**

5 (a) Describe trunking diagram of 10,000 line exchange.

(b) Compare single stage and multistage switching network used _{;} in communication system.

**OR**

5 (a) Write short note on Stored Program Control.

(b) Describe the EPABX system used for communication system.