Adaptive,Ultra wideband and Tera hertz antennas

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Adaptive antennas

• Spectral efficiency:A measure of the amount of information – billable services – that carried by a wireless system per unit of spectrum

• Measured in bits/second/Hertz/cell, includes effects of• multiple access method• modulation methods• channel organization• resource reuse (code, timeslot, carrier, …)• Per-Cell” is critical• fundamental spectral efficiency limitation in most systems is

self generated interference• results for isolated base stations are not representative of

real-world

• Spectral efficiency directly affects an operator’s cost structure

• For a given service and grade of service, it determines

• required amount of spectrum (CapEx)• required number of base stations (CapEx, OpEx)• required number of sites and associated site maintenance (OpEx)

and, ultimately, consumer pricing and affordability

• Quick calculation:

ULTRA WIDE BAND ANTENNA

• Ultra-wideband is a technology for transmitting information spread over a large bandwidth (>500 MHz).

• UWB has traditional applications in non-cooperative radar imaging. Most recent applications target sensor data collection, precision locating and tracking applications.

• Ultra wideband was formerly known as "pulse radio“• It uses pulses of short duration compressed in time opposed to

traditional sinusoidal.• A significant difference between conventional radio transmissions

and UWB is that conventional systems transmit information by varying the power level, frequency, and/or phase of a sinusoidal wave.

• UWB transmissions transmit information by generating radio energy at specific time intervals and occupying a large bandwidth, thus enabling pulse-position or time modulation

Ultra wide band antennas

Introduction

• Technology for short range Wireless radio communications

• Bandwidth more than 25% of a center frequency or more than 1.5 GHz

• Different from conventional narrowband and wideband systems

Why Ultrawideband?

• Crunch in RF spectrum availability

• Variations in RF spectrum from one country to next

• Devices using RF Spectrum are more complex, cost more, and consume more power

• 3.1 -10.6 GHz assigned by FCC• 200 Mbps upto 10 meters• Limited transmit power of 41dbm/Mhz

UWB Specifications

How it works

• Generation of extremely short digital pulses in the subnanosecond range.

• Uses and extremely wide band of RF spectrum to transmit data

UWB Characteristics

• Extremely low transmission energy

• Extremely difficult to intercept

• Multipath immunity to fading

• Follows Shannon’s channel capacity theorem

Comparison with other technologies

• Faster than Bluetooth, Wi Fi• Data rate of 450Mbps instead of 1Mbps• Complementary to existing radio technologies like 802.11

UWB Applications

• Replacing IEEE 1394 cables with wireless connectivity

• No. 1 High quality wireless video

• Accurate Ranging information

• Radar and Imaging

Challenges

• Interference with other licensed bands

• Tradeoffs with noise

TERA HERTZ ANTENNA

1. There is a growing demand in wireless communications for more services such as fast access to the World Wide Web and videophones, the ability to send large documents with fast speed, which means that an increased bandwidth is required.

2. Terahertz (THz) technique is considered as one of the methods to solve this problem recently

Terahertz Generation using InN

• Objective:• Develop a compact and efficient source for pulsed

Terahertz emission• Approach• Investigate InN, which can produce THz radiation

when illuminated with short pulse from a fiber laser

Thz wave generation

1. Several techniques have been developed to generate the THz radiation. Rapid photoconductor is the most widely used method to generate THz fields nowadays.

2. It can generate ultrashort electrical signals with duration of several hundreds of femtosecond that have a

spectrum situated in the THz region.

• When the energy is input into the semiconductor, it will separate the electrons and holes. They are usually called electron-hole pairs. If a bias voltage is put on the semiconductor, the electrons and holes will flow in a certain direction and the current is produced.

• Furthermore, if the input energy changes rapidly such as a short period pulse laser, the number of the electronholes will change rapidly, the current intensity also change rapidly, therefore, the time various electric field is produced and the electromagnetic waves are generated.

• Eg. Of Tera hertz antenna:

• Photo conductive tera hertz antenna

THE END