The Bluetooth™

The Bluetooth™ is an interesting up-coming technology. It was originally conceived by Ericsson and has been enthusiastically ushered in and promoted to enable devices of all kinds from laptops and cell phones, to personal digital assistants and household appliances  to have the capability of communicating and interoperating with one another in the wireless medium.

The underlying concept of the Bluetooth technology remains the transparent wireless RF communication between electronic devices. This mode of communication can offer a set of advantages encompassing a viable voice/data access point, no cumbersome cabling and creation of an “as-you-please” ad hoc wireless network.

Bluetooth technology is characterized by personal connectivity of enabled devices, spontaneous creation of disposable networks and low-cost, low-power indoor wireless transmissions of short ranges supporting 721 kbps or 432.6 kbps over asynchronous and synchronous links respectively.

Essentially, the transmitter and receiver parts of the Bluetooth system use the hopping frequency scheme, thus facilitating modulation and demodulation of the baseband signal with a frequency-modulation scheme. That is, the Bluetooth conceptually connects everything wirelessly with a frequency-hopping radio link in short-range areas.

For example, a Bluetooth solution can replace the interconnecting cable across any electronic devices to be linked together for communication. Further, the Bluetooth carries a cost-attractive advantage and is expected to be the new hot-comer in the wireless technology, which may eventually replace existing wireless networking concepts, such as the RF-based WLAN (of IEEE 802.11) and/or infrared-based WLAN of IrDA (Infrared Data Association).

Though an IrDA system is not wired, it is, however, limited for use only between two devices to communicate with each other at the same time along unobstructed LoS because of the optical (IR) link adopted. The Bluetooth on the other hand, can work with more than two devices and the line-of-sight requirement is not emphasized.

Moreover, the Bluetooth technical specification is completely open, that is, no licensing fee is required for using the associated specifications by any developer and FCC regulations are just limited to ISM band constraints. As indicated before, the Bluetooth operates around 2.4 GHz radio spectrum that belongs to the Industrial, Scientific, and Medical (ISM) band.

This 2.4 GHz band is available world-wide. Specifically, a bandwidth between 2400 MHz and 2483.5 MHz is specified under FCC Part 15 regulations; and, ETS-300328 also regulates the same band. Further, Japan has also allowed the use of this band in commercial applications.

Bluetooth products are qualified through the Bluetooth Qualification Program. The specification supporting this programme lists rules for compliance, including interoperability with other Bluetooth devices from other manufacturers. Certified “Bluetooth-enable” devices must comply with this specification.

A Bluetooth system contains, in essence, a radio receiver, a link controller to connect the transreceiver to the link manager. The link manager interfaces with the application software, which talks to the host hardware layer. The antenna part performs RF-to-air interfacing in the transmit- and receive-operational phases.

Original equipment manufacturers (OEMs) can choose between a Bluetooth solution with the antenna incorporated in the package or with an antenna tailormade and located externally to the unit. In the integrated module the embedded antenna eliminates requirements for tuning and the need for an additional connection on the printed circuit board (PCB).

It is observed that a Bluetooth enabled device (such as PCMCIA devices) may be prone to ineffective radiation from the external antennas as a result of improper implementation with the antenna too proximal to the grounded metal case. Hence, the antenna considerations in Bluetooth applications need a careful design and implementation strategies.