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     Volume 1 Issue 21 | December 31, 2006 |


  
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Feature

Bluetooth Transceiver designing in IUT,
A desire to make communication wireless.

MD. Shirajum Munir Rumi

It may not be the first time, but it unquestionably is a rare endeavor to try and design a Bluetooth Transceiver in Bangladesh by five students from Islamic University of Technology (IUT), Department of Electrical and Electronic Engineering (EEE). The design includes choosing specific IC, simulating the operation by software and ensuring its operational capability in the worst possible situation.

Bluetooth technology originated in 1994 when Ericsson came up with a concept to use a wireless connection to connect items such as an ear phone and a cordless handset or a mobile phone. The idea behind Bluetooth (although it was not yet called Bluetooth) was developed further as the possibilities of interconnections with a variety of other peripherals such as computer printers, phones and more were realized. Using this technology, the possibility of quick and easy connections between electronic devices would become possible.

It was decided in order to enable the technology to move forward that it needed to be opened up as an industry standard. Accordingly, in Feb 1998, 5 companies (Ericsson, Nokia, IBM, Toshiba and Intel) formed a Special Interest Group (SIG). Three months later in May 1998 Bluetooth was publicly announced with the first specification followed by the first release of the standard in July 1999. Later more members were added to the group with four new companies Motorola, Microsoft, Lucent and 3Com joining the group. Since then more companies have joined and the specification has grown and is now used in a large variety of products. The vision behind developing this technology was to:

* Provide a Universal radio interface for ad-hoc wireless connectivity
* Interconnecting computer and peripherals, handheld devices, PDAs, cell phones replacement of costly IrDA
* Embed in other devices, goal: 5€/device (2002: 50€/USB Bluetooth)
* Communication over short range (10 m), low power consumption, license-free 2.45 GHz ISM
* Transmission of Voice and data, approx. 1 Mbit/s gross data rate

The technical specifications a designer has to keep in mind before designing a Bluetooth device are:

* It has to operate in ISM band at 2.4 GHz
* 1 MHz wide channels
* Nominal 1600 frequency hops per second
* 1 Mbit/sec raw data rate, 720 kbit/sec per channel throughput
* Maximum power of 100 mW, standard power of 1 mW
* Built in error correction, encryption, and Async/Sync connection type

The Bluetooth Transceiver design was done by a group of five 3rd year students of IUT under supervision of Mr. Rishad Ahmed Shafiq, Assistant Professor, IUT and
the Co-Supervision of Mr. Shahriar Rahman, Lecturer, IUT.

The name of the group is 'SAILORS' and it comprises of MD. Shirajum Munir Rumi, Md. Abu Naser, Md. Junayed Sarker, Md. Nizam Uddin and Raffel Jahan. For the design we have chosen the super heterodyne technique. The basic problems (Instability with high gain, increasing bandwidth, variable selectivity with frequency) in TRF (tuned radio frequency) systems led to general usage of the Super heterodyne receivers. Here the key concept was mixing frequencies or frequency conversion, which translates a signal to a higher and lower frequency, the sum and difference frequencies of the carrier and information. The lower frequency is taken which is called IF (intermediate frequency). This process to produce a difference frequency is called Super heterodyning. The basic block diagram of our total design is:

The operation mode of the transceiver is full duplex. That means it's capable of receiving and transmitting information at the same time.

 

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