While studying engineering in Electronics and Communications domain, we are sometimes desirous of working in core companies. We explore which are the companies that work in the core areas and wonder what type of questions these organizations usually ask in their written tests, interviews etc. Sometimes we get appropriate material to prepare for these companies but at many times, we don’t. So we, the VLSIFacts team, have tried to make a question bank from various sources to help you prepare for the core companies. One such company is Bharat Electronics Limited (BEL) which is a Navratna company of the Government of India. Now, let’s look at some of the questions asked in BEL in recent times:
Q-1. What is meant by noise figure? What does it signify?
A : Noise Figure or NF is defined as the ratio of output noise power to the thermal noise in the input terminal at the standard noise temperature (290 K) or simply the ratio of input SNR to output SNR. It is a measure of degradation of Signal to Noise Ratio (SNR) which is caused by the components in RF (Radio Frequency) signal chain.
Q-2. What is Standing Wave Ratio (SWR)? SWR = 1 signifies?
A : SWR is used for impedance matching of load to the characteristic impedance of a transmission line carrying RF signals. SWR=1 signifies that the load impedance is equal to the characteristic impedance of the line.
Q-3. What is Voltage Standing Wave Ratio (VSWR) and Power Standing Wave Ratio (PSWR)?
A : SWR is generally used in terms of the maximum and minimum level of AC voltages in a transmission line thus called VSWR. PSWR is the square of VSWR as power is related to the square of voltage.
Q-4. Name a component that is generally used to sample a portion of energy transmitted in a line.
A : Directional Coupler.
Q-5. What is the change in transmitted power when modulation index in AM is changed from 0 to 1?
A : The transmitted power is decreased by 50%.
Q-6. When is FM equal to AM?
A : FM (Frequency Modulation) is equivalent to AM (Amplitude Modulation) when the FM index is very less than 1.
(Continued to Part 2…)