Question

Match List-I with List-II and select the correct answer using the code given below the lists:

List-I	List-II
a. Cavity wave meter	i. Impedance
b. VSWR meter	ii. Frequency measurements
c. Bolometer	iii. Antenna measurements
d. Fraunhofer region	iv. Microwave power measurements

1. a - iii, b - i, c - iv, d - ii
2. a - ii, b - i, c - iv, d - iii
3. a - iii, b - iv, c - i, d - ii
4. a - ii, b - iv, c - i, d - iii

Answer 1

Correct Answer - Option 2 : a - ii, b - i, c - iv, d - iii

1.Cavity Wave Meter-cavities are used in microwave circuits as circuit elements and as measuring instruments such as frequency meters. By using cavity wavemeter we can measure the frequencies. wavemeter  between generator and load. The resonant frequency of LC circuit is defined by following equation.

\({F_r} = \frac{1}{{2 \star \pi \star \sqrt {LC} }}\)

Where, F_r = Resonant frequency (H₃)

L = Inductance in Henrys

C = capacitance in farads

π = 3.1416

2.VSWR meter-In the VSWR meter slotted lines are present, By proper adjustment we can measure the Impedance.

3. Bolometer-It  is a device which is used for low Microwave power measurements. The element used in bolometer could be of positive or negative temperature coefficient. In bolometer  change in resistance is proportional to Microwave power applied for measurement. This bolometer is used in a bridge of the arms as one so that any imbalance caused, affects the output. 

4.Fraunhaufer Region- In the study of diffraction and antenna design, the near field is that part of the radiated field that is below distances shorter than the Fraunhofer distance.

Fraunhaufer distance \(\left( {dF} \right) = \frac{{2{D^2}}}{\lambda }\), where D = diameter of antenna.