Robert Bosch Technical Interview for ECE/EEE 2019-20

Questions

• What is CDMA?

CDMA stands for Code Division Multiple Access which uses digital format. In CDMA systems several transmissions via the radio interface take place simultaneously on the same frequency bandwidth. User data is combined at the transmitter’s side with a code, then transmitted. On air, all transmission get mixed. At the receiver’s side the same code is used as in the transmitter’s side. The code helps the receiver to filter the user information of the transmitter from incoming mixture of all transmissions on the same frequency band and same time.

• What are different categories of antenna and give an example of each?

Different categories of antenna are as follows :

1. Wire Antennas – Short Dipole Antenna
2. Microstrip Antennas – Rectangular Microstrip (Patch) Antennas
3. Reflector Antennas – Corner Reflector
4. Travelling Wave Antennas – Helical Antennas
5. Aperture Antennas – Slot Antenna
6. Other Antennas – NFC Antennas

•  What are the advantages of spread spectrum?

SPread spectrum has the following advantages :

1. No crosstalk interference.
2. Better voice quality/data integrity and less static noise.
3. Lowered susceptibility to multipath fading.
4. Inherent security.
5. Co-existence.
6. Longer operating distances.
7. Hard to detect.
8. Hard to intercept or demodulate.
9. Harder to jam than narrow bands.
10. Use of ranging and radar.

• List some advantages of GSM.

Here are some advantages of GSM :
1. GSM is mature, this maturity means a more stable network with robust features.
2. Less signal deterioration inside buildings.
3. Ability to use repeaters.
4. Talk time is generally higher in GSM phones due to pulse nature of transmission.
5. The availability of Subscriber Identity Modules allows users to switch networks and handset at will.
6. GSM covers virtually all parts of world so international roaming is not a problem.

•  Explain radio environment in building.

Building penetration : Building penetration depends on the material used for construction and architecture used. This varies building to building and is based on building construction.
Building Height Effect : The signal strength is always higher at top floor and generally floor gain height is about 2.7dB/floor which is not dependent on building construction.
Building Floor Reception : The signal isolation between floors in a multi floor building is on the average about 20dB. Within a floor of 150 * 150 feet, the propagation loss due to interior walls, depending on the wall materials is about 20 dB between the strong and the weak areas.

• For 1:2:4 ratios the weight of cement is 50 kg then how many kg are the weight of sand and aggregate?

  It is the ratio of cement:fine aggregate (i.e.sand) :coarse aggregate.

So , for the ratio 1:2:4.

If you take 50 kg of cement,

Then,

2*50 = 100kg of sand.

And

4*50 = 200kg of coarse aggregate

• Explain the concept of frequency re-use.

The whole of the geographical area is divided into hexagonal shape geometrical area called cell and each cell has its own transceiver. Each BTS (cell site) allocated a different band of frequency or a different channel. Each BTS antenna is designed in such a way that I cover cell area in which it is placed with frequency allotted without interfering other cell signals. The design process of selecting and allocating channel groups for all of the cellular base stations within the system is called frequency reuse.

• What Is a Capacitor?

A capacitor is an electrical/electronic device that can store energyin the electric field between a pair of conductors (called “plates”). The process of storing energy in the capacitor is known as “charging”, and involves electric charges of equal magnitude, but opposite polarity, building up on each plate. 
Capacitors are often used in electric and electronic circuits asenergy­storage devices. They can also be used to differentiate between high­frequency and low­frequency signals. This property makes them useful in electronic filters.

Capacitors are occasionally referred to as condensers. This term is considered archaic in English, but most other languages use a cognate of the condenser to refer to a capacitor.

• What Is Crosstalk?

Crosstalk is a form of interference caused by signals in nearby conductors. The most common example is hearing an unwanted conversation on the telephone. Crosstalk can also occur in radios, televisions, networking equipment, and even electric guitars.

• What Is Diode?

In electronics, a diode is a two­terminal device. Diodes have two active electrodes between which the signal of interest may flow, and most are used for their unidirectional current property.

• What Is Barkhausen Criteria?

Barkhausen criteria, without which you will not know which conditions, are to be satisfied with oscillations.

“Oscillations will not be sustained if, at the oscillator frequency, the magnitude of the product of the transfer gain of the amplifier and the magnitude of the feedback factor of the feedback network ( the magnitude of the loop gain ) are less than unity”.

The condition of unity loop gain ­Aβ = 1 is called the Barkhausencriterion. This condition implies that | Aβ|= 1and that the phase of – Aβ is zero.