BCM20705 Datasheet, PDF (15/67 Pages) Cypress Semiconductor – Single-Chip Bluetooth Transceiver and Baseband Processor

BCM20705 Data Sheet
Receiver Path
Receiver Path
The receiver path uses a low IF scheme to downconvert the received signal for demodulation in the digital
demodulator and bit synchronizer. The receiver path provides a high degree of linearity, an extended dynamic
range, and high order on-chip channel filtering to ensure reliable operation in the noisy 2.4 GHz ISM band. The
front-end topology, with built-in out-of-band attenuation, enables the device to be used in most applications
without off-chip filtering. For integrated handset operation where the Bluetooth function is integrated close to the
cellular transmitter, minimal external filtering is required to eliminate the desensitization of the receiver by the
cellular transmit signal.
Digital Demodulator and Bit Synchronizer
The digital demodulator and bit synchronizer uses the low IF received signal to perform an optimal frequency
tracking and bit synchronization algorithm.
Receiver Signal Strength Indicator
The BCM20705 radio provides a Receiver Signal Strength Indicator (RSSI) signal to the baseband so that the
controller can take part in a Bluetooth power-controlled link by providing a metric of its own receiver signal
strength to determine whether the transmitter should increase or decrease its output power.
Local Oscillator Generation
Local Oscillator (LO) generation provides fast frequency hopping (1600 hops/second) across the 79 maximum
available channels. The LO generation subblock employs an architecture for high immunity to LO pulling during
PA operation. The device uses fully-integrated PLL loop filters.
Calibration
The radio transceiver features an automated calibration scheme that is fully self-contained in the radio. User
interaction is not required during normal operation or during manufacturing to provide the optimal performance.
Calibration optimizes the performance of all major blocks in the radio, including gain and phase characteristics
of filters, matching between key components, and key gain blocks. Calibration, which takes process and
temperature variations into account, occurs transparently during the settling time of the hops, adjusting for
temperature variations as the device cools and heats during normal operation.
Broadcom®
Bluetooth Transceiver and Baseband Processor
November 13, 2014 • MCS20705-DS104-R
Page 14
BROADCOM CONFIDENTIAL