Thoughts Decoded

BLUETOOTH is currently being introduced into several market segments, like mobile phones, headsets, PC’s etc. Bluetooth operates in the ISM-band between 2.4 GHz and 2.48 GHz and uses 80 channels, with a channel spacing of 1 MHz. Bluetooth was orginally specified in such a way that the complete system, i.e. radio and baseband, could be integrated into a single CMOS integrated circuit. This resulted in a quite poor specification for the sensitivity (-70 dBm) and output power (0 dBm, Class II) [1], [2].

In practice, it now becomes clear that systems that just meet this specification show a quite poor quality, especially for indoor voice/audio applications. There fore, the newest generation of Bluetooth BiCMOS radios show a much improved performance, with a sensitivity better than -80 dBm and output power up to +4 dBm or higher.

Another way to improve the so-called ”quality-of-service” in a Bluetooth connection is the use of antenna diversity. This technique has already been succesfully used in systems like DECT and WLAN. Originally one thought that the Bluetooth standard, which incorporates frequency hopping, was robust enough to cope with indoor fading. However, in this paper it will be shown by means of measurements supported by a theoretical model that a significant improvement in the quality of a Bluetooth connec tion can be estabished in an indoor environment. Based on these results a demonstrator radio with embedded diversity was developed.

Basic Structure of Bluetooth Antenna

Bluetooth and Infrared

The distance an infrared signal can travel varies based on the strength of the remote, but is usually less than 50 feet for household electronics.

In order for an infrared signal to be detected, there must be a direct line of sight between the transmitter (remote) and the receiver (TV).

If there is a wall or large object between them, the signal will not pass through it.
Infrared technology is what most TV remotes use. Well newer phones are taking out infrared considering Bluetooth is much more useful with a 10m radius distance.

Why Bluetooth?

Bluetooth on the other hand, uses a radio frequency, which allows transmission through walls and other objects.

The standard range of a Class 3 Bluetooth device is about 30 ft., which makes it ideal for syncing PDAs with computers, using wireless cell phone headsets, and enabling hands free cell phone use inside Bluetooth-enabled automobiles.

Because Bluetooth technology is based on a standard 2.4 GHz frequency, different Bluetooth devices can typically communicate with each other, regardless of the manufacturer.

So think Bluetooth as a single popcorn in a bowl,the popcorn is your phone and the empty area around your phone is how far it can go.

And infrared is like… kissing a person on the lips, to send a kiss from your lips must come contact with other lips.