Bluetooth/IEEE802 Integration

Suppose that, after you’ve designed an IMT2000DS phone that can also support
IMT2000TC and GSM 800, 900, 1800, the marketing team reminds you that you have to
include a Bluetooth transceiver. Bluetooth is a low-power transceiver (maximum 100
mW) that uses simple FM modulation/demodulation and frequency hopping at 1600
hops per second over 79 × 1 MHz hop frequency between 2.402 and 2.480 GHz (the
Industrial Scientific Medical, or ISM, band). Transmit power can be reduced from 100
mW (+20 dBm) to 0 dBm (1.00 mW) to -30 dBm (1μW) for very local access, such as
phone-to-ear, applications.
Early implementations of Bluetooth were typically two-chip, which provided better
sensitivity at a higher cost; however, present trends are to integrate RF and baseband
into one chip, using CMOS for the integrated device, which is low-cost but noisy. The
design challenge is to maintain receive sensitivity both in terms of device noise and
interference from other functions within the phone.
Supporting IEEE 802 wireless LAN connectivity is also possible, though not necessarily
easy or advisable. The IEEE 802 standard supports frequency hopping and
direct-sequence transceivers in the same frequency allocation as Bluetooth. Direct
sequence provides more processing gain and coherent demodulation (with 3 dB of sensitivity)
compared to the frequency hopping option, but it needs a linear IQ modulator,
automatic frequency control for I/Q spin control, and a linear power amplifier.