electronics and communication technical interview questions, electronics viva questions,

Technical Interview Questions 

Electronics & Communication Engineering

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 is handover and what are its types?

• Handover in mobile communication refers to the process of transferring a call from one network cell to another without breaking the call.

There are two types of handover which are as follows :

• Hard Handoff : hard handoff is the process in which the cell connection is disconnected from the previous cell before it is made with the new one.

• Soft Handoff : It is the process in which a new connection is established first before disconnecting the old one. It is thus more efficient and smart.

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 having its own transceiver. Each BTS (cell site) allocated different band of frequency or 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 station within system is called frequency reuse.

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

Different categories of antenna are as follows :

• Traveling Wave Antennas - Helical Antennas
• Other Antennas - NFC Antennas
• Micro strip Antennas - Rectangular Micro strip (Patch) Antennas
• Reflector Antennas - Corner Reflector
• Wire Antennas - Short Dipole Antenna
• Aperture Antennas - Slot Antenna

Explain Bluetooth.

• Bluetooth is designed to be a personal area network, where participating entities are mobile and require sporadic communication with others. It is omni directional i.e. it does not have line of sight limitation like infra red does. Ericsson started the work on Bluetooth and named it after the Danish king Harold Bluetooth. Bluetooth operates in the 2.4 GHz area of spectrum and provides a range of 10 meters. It offers transfer speeds of around 720 Kbps.

What is ionospheric bending?

• When a radio wave travels into the ionospheric layer it experiences refraction due to difference in density. The density of ionospheric layer is rarer than the layer below which causes the radio wave to be bent away from the normal. Also the radio wave experiences a force from the ions in the ionospheric layer. If incident at the correct angle the radio wave is completely reflected back to the inner atmosphere due to total internal reflection. This phenomenon is called ionospheric reflection and is used in mobile communication for radio wave propagation also known as ionospheric bending of radio waves.