## Waveguide Questions for GATE EC

1) Which is the dominant mode in TM?

a)

b)

c)

d)

2) Dominant mode in Waveguides usually refers to ?

a)

b)

c)

d)

3) The cut-off wavelength of rectangular waveguide was measured to be 8 cm and 4.8 cm when excited in and modes respectively. Determine the dimensions of a waveguide

a= ______

b= ______

4) A rectangular waveguide has dimensions a=2.5 cm and b=1 cm. A microwave signal at a frequency if 8.6 GHz is to be propagated through this waveguide.Which of the following mode can exist in rectangular waveguide?

a)

b)

c)

d)

5) The modes in a rectangular waveguide are denoted by / where m and n are the Eigen

numbers along the larger and smaller dimensions of the waveguide respectively. Which one of

the following statements is TRUE?

a) The mode of the waveguide does not exist

b) The mode of the waveguide does not exist

c) The and the modes both exist and have the same cut – off frequencies

d) The and the modes both exist and have the same cut – off frequencies

6) If is the cut off wavelength of a rectangular waveguide and is a free space wavelength. Then the condition for wave propagation is

a) >

b) <

c) =

d) = 0

7)

TE(02) means the wave exists only in the Y direction. So look out for Electric field lines which are originating or ending at Y axis. In this case, options A and C are eliminated. Now we are left with option b and d.

Here as you can see, TE(02) means n=2 (Mode is 2) . So the E field equation will be of the following form

= K

Y axis range is from 0 to b.

At

y=0 and y=b, value of sin is 0.

At y=b/4, value of sin is 1

At y=3b/4, value of sin is -1

So, the correct answer is option “d” , where E field lines are pointing towards positive x axis below b/2 and towards negative x axis above b/2

…………………………………………………………………………………………………….

Answer Keys

1-d, 2-a ,3 => a=4, b=3 ,4-a,5-a, 7-d

## Lead – Lag compensator previous GATE questions

**GATE EC-2012**

The transfer function of a compensator is given by =

- is a lead compensator if

A) a=1, b=2 B) a=3,b=2 C) a=-3 b=-1 d) a=3, b=1

2. The phase of the above lead compensator is maximum at

a) b) c) d)

3) The open loop transfer function of a plant is given as G(s)=. If the plant is operated in a unity feedback configuration, then the lead compensator that can stabilize this control system is

a) 10 b) 10

c) 10 d) 2

4) The transfer function of a phase lead compensator is given by = where T>0 . The maximum phase shift produced by such compensator is(in degrees)

a) 90 b) 30 c) 45 d) 60