Monday, September 12, 2016

What is Ray Model?

Introduction Ray Model


1. Optical fiber is basically a solid glass rod. The diameter of rod is so small that it looks like a
fiber.

2. Optical fiber is a dielectric waveguide. The light travels like an electromagnetic wave inside
the waveguide. The dielectric

waveguide is different from a metallic waveguide which is used at microwave and millimeter
wave frequencies.

3. In a metallic waveguide, there is a complete shielding of electromagnetic radiation but in an
optical fiber the electromagnetic radiation is not just confined inside the fiber but also extends outside the fiber.

4. The light gets guided inside the structure, through the basic phenomenon of total internal
reflection .

5. The optical fiber consists of two concentric cylinders; the inside solid cylinder is called the
core and the surrounding

6. For the light to propagate inside the fiber through total internal reflections at core-cladding
interface, the refractive index of the core must be greater than the refractive index of the cladding. That is .

BROADBAND COMMUNICATION IMPORTANT QUESTIONS

BROADBAND COMMUNICATION QUESTION BANK


1.  (a)         
What are the advantages of optical fiber cables over the co-axial cables?    
(06)
(b)
Calculate NA, Acceptance angle and Angle of fiber with core and cladding refractive index values as n1=1.5 and n2=1.45 respectively.                                                                  
(06)
(c)
Explain the “mode theory” of optical fiber.   
(06)
2.  (a)         
What is meant by acceptance angle and acceptance cone for optical fiber? Show and explain it’s relationship to numerical aperture and refractive indices of core & cladding.
(06)
(b)
If a MMSI fiber of core radius 25 micrometer operating at 1300nm, has  core and cladding refractive index as 1.5 & 1.38 respectively; Calculate Numerical aperture, Normalized frequency, Solid acceptance angle and number of modes entering in the fiber
(06)
(c)
If the mean optical power in a 8 km long fiber at launching and output zone is 12 and 2 microwatt; determine (1) overall signal attenuation in dB and (2) when length is 10 km with the splices of 1dB attenuationeach at the interval of 1km.
(06)
3.  (a)         
What is dispersion in fiber? Explain intra-modal dispersion in details.
(08)
(b)
A SMSIfiber with core and cladding refractive indices as 1.447 and 1.442respectively is designed to operate at wavelength 1.3 micrometer. When core diameter is 7.2 micrometer; confirm that the fiber permits single mode transmission and estimate the range of wavelengths over which this will occur.           
(08)
4.  (a)         
Explain the “linear scattering losses” in fibers.
(08)
(b)
A MMSIF has NA as 0.3 and core refractive index as 1.45. The material dispersion parameter as 250 ps/nm.km makes it totally dominating intra-modular dispersion mechanism. Estimate (1) total pulse broadening/km when the fiber is used with the LED source of RMS spectral width of 50 nm, and (2) corresponding bandwidth-length product.
(08)
5.  (a)         
Explain the three transmissions windows of optical communication along with the attenuation curves for SMF.
(08)
(b)
Explain bending losses in fiber.         
(08)
6.  (a)         
Explain material absorption losses in silica fiber.
(08)

WIRELESS NETWORKS IMPORTANT QUESTIONS

WIRELESS NETWORKS QUESTION BANK


QUESTION BANK FOR WIRELESS NETWORKS :

Q.1.What are draw back of  2G  Services ? What are its silent features of 3G services that overcome the drawbacks of 2G services?
Q.2.Discuss the features of IMT2000 that have been adopted in UMTS/3G services.
Q.3.Explain the basic concept of WCDMA ?Which is a air interface of UMTS.
Q.4.Give the specification of WCDMA air interface .Also  explain how the information /message  is coded and scrambled in WCDMA
Q.5.Explain in brief the physical channels in WCDMA and the function performed by them
Q.6.Explain the transport channel in CDMA that are mapped on the physical channel.
Q.7.Draw the architecture of 3GPP RELEASE  4 distributed network architecture.
Q.8. .Draw the architecture of 3GPP RELEASE  5 All IP multimedia  network architecture.
Q.9.What is ALL IP network ? Explain its architecture  ? Explain its Advantages?
Q.10.What  is core network ?Explain its architecture ?
Q.13.Write a short note on TD-SCDMA and draw the system architecture of TD-SCDMA.

Q.14. Differentiate between the TD-SCDMA,WCDMA and CDMA 2000.

Friday, September 9, 2016

What is Satellite Communication?

Meaning of Satellite & Basic concepts:

Satellite:

"satellite is object which rotates around some body due to the effect of gravitational forces" .

OR

"A satellite is an object which has been placed into orbit by human endeavor" .


Wednesday, September 7, 2016

What is the meaning of Multiplexing ?

Multiplexing Definition and types:

Definition: Multi means 'Many', Plexing means 'having parts or units' combinely latin meaning suggest this but in reality this term is used for multiplexing of signals in telecommunications  "Multiplexing is the procedure in which numerous Data Streams, originating from diverse Sources, are joined and Transmitted over a Single Data Channel or Data Stream."

Wavelength division multiplexing (WDM)

Wavelength division multiplexing (WDM):


Wavelength division multiplexing (WDM)
Wavelength division multiplexing (WDM)

Definition: "Wavelength-division multiplexing (WDM) could be a technique of mixing multiple signals on optical device beams at varied infrared (IR) wavelengths for transmission on fiber optic media. every optical device is modulated by AN freelance set of signals. Wavelength-sensitive filters, the IR analog of visible-light color filters, square measure used at the receiving finish".

Saturday, September 3, 2016

IP Address Subnetting & CIDR


IP Address Subnetting & CIDR



IP Address Subnetting & CIDR

IP Address Subnetting & CIDR


Saturday, August 20, 2016

Content Management System

Content Management System 

Content Management System
Content Management System

Wednesday, August 17, 2016

Applications of Microwave Engineering

Applications of Microwave Engineering


The majority of today’s applications of RF and microwave technology are to wireless networking and communications systems, wireless security systems, radar systems, environmental remote sensing, and medical systems.

STAR DELTA connection Diagram and Working principle

STAR DELTA connection Diagram and Working principle

Descriptions: A Dual starter connects the motor terminals directly to the power supply. Hence, the motor is subjected to the full voltage of the power supply. Consequently, high starting current flows through the motor. This type of starting is suitable for small motors below 5 hp (3.75 kW).
Reduced-voltage starters are employed with motors above 5 hp. Although Dual motor starters are available for motors less than 150kW on 400 V and for motors less than 1 MW on 6.6 kV.
Supply reliability and reserve power generation dictates the use of reduced voltage or not to reduce the starting current of an induction motor the voltage across the motor need to be reduced. This can be done by 1. Autotransformer starter, 2. Star-delta starter or 3. Resistor starter. Now-a-days VVVF drive used extensively for speed control serves this purpose also.

Difference Between Transmission line and Waveguide

Comparison Between Transmission line and Wave guide :




Transmission line
Wave guide
Small cross-section transmission lines (like coaxial cables) can only transmit low power levels due to the relatively high fields concentrated at specific locations within the device
Metal waveguides can transmit high power levels. The fields of the propagating wave are spread more uniformly over a larger cross-sectional area than the small cross-section transmission line.
Large cross-section transmission lines can transmit high power levels.
Large cross-section (low frequency) waveguides are impractical due to large size and high cost.




Difference Between Transmission line and Waveguide

Sunday, August 14, 2016

Design and Implement of QPSK Modem Based on FPGA

 Design and Implement of QPSK Modem Based on FPGA.



Abstract :

This paper presents a method to designs QPSK modulator and demodulator of a spread spectrum system which use field programmable device. The method uses the tool of Quartus of American Altera Co. The whole system is divided into several small models based on top-down design method, and using VHDL hardware description language to design each model. 

Saturday, March 12, 2016

Comparison of wireless Access Technologies (WCDMA, HSPA, HSPA+, LTE)

WCDMA, HSPA, HSPA+, LTE



         "An information system formed by HAP (High Altitude Platform) will be a new generation-system for the wireless communications and HAPS (HAP Station) communication system combines the advantages of both terrestrial and satellite communication systems and avoids, to different extents, their disadvantages. Third generation (3G) mobile technology which is specified by the third generation partnership project (3 GPP) is definitely one of the candidates. With the success of wireless network, the IEEE 802.16 standard, with its wireless metropolitan area network (MAN) air interface appears to be a strong competitor. We provide initial practical comparison of these two technologies for HAPS Communication".



WCDMA
HSPA
HSPA+
LTE
Maximum Uplink Speed
128 Kbps
5.7 Kbps
11 Mbps
50 Mbps
Maximum Downlink Speed
14 Mbps
11 Mbps
28 Mbps
100 Mbps
Spectrum FDD
5 MHz
5 MHz
5 MHz
10 MHz
Latency Round trip
150 ms
100 ms
50 ms
10 ms
Access Method
CDMA
CDMA
CDMA
CDMA/SC FDMA











Table:  Comparison of wireless Access Technologies




Comparison of wireless Access Technologies (WCDMA, HSPA, HSPA+, LTE)
Comparison of wireless Access Technologies (WCDMA, HSPA, HSPA+, LTE)

Wednesday, December 9, 2015

Testability VLSI: Boundary scan

Testability VLSI: Boundry scan

  • Boundary scan is a test technique using scan methodology, involving digital services, digital devices, designed with shift registers (scan flip flops) placed between each devicepin and the internal logic.

  •   These shift registers can control and observe signal values present at each input and output pin and are connected together in serial fashion to form a data register chain, called boundary scan shift register with shift and update stages.

Sunday, December 6, 2015

JTAG Testability: JTAG Test Access Port Controller

JTAG Test Access Port


JTAG Testability: JTAG Test Access Port Controller
JTAG Testability: JTAG Test Access Port Controller
                                                           

The TAP is a general-purpose port that can provide access to many test support functions built into a component, including the test logic defined by this standard.