Preliminary Data Sheet
6/30/09
BCM4325
Power Amplifier
The fully integrated PA provides a maximum output signal level (see Table 27: “Bluetooth Transmitter RF Specifications,”
on page 81) using a highly linearized, temperature compensated design. This provides greater flexibility in front-end
matching and filtering. Due to the linear nature of the PA combined with some integrated filtering, no external filters are
required for meeting Bluetooth and regulatory harmonic and spurious requirements. For integrated mobile handset
applications where the Bluetooth is integrated next to the cellular radio minimal external filtering can be applied to achieve
near thermal noise levels for spurious and radiated noise emissions.
The integrated power amplifier is Bluetooth Class 2 compliant and includes power control adjustment with a 28 dB range
and 4 dB nominal step size. The integrated power amplifier can be configured as a PA driver to an external power amplifier
for full Bluetooth Class 1 compliance.
RECEIVE
The receiver path uses a low-IF scheme to down convert 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 BCM4325 to be used in most applications with no 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 takes the low-IF received signal and performs an optimal frequency tracking
and bit synchronization algorithm.
Receiver Signal Strength Indicator
The radio portion of the BCM4325 provides an 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 generation provides fast frequency hopping (1600 hops/second) across the 79 maximum available
channels. The local oscillator generation subblock employs an architecture for high immunity to local oscillation pulling
during PA operation. The BCM4325 uses an internal RF and IF loop filter.
CALIBRATION
The BCM4325 radio transceiver features an automated calibration scheme that is fully self contained in the radio. No user
interaction is required during normal operation or during manufacturing to provide the optimal performance. Calibration
optimizes the performance of all the major blocks within the radio to within 2% of optimal conditions, including gain and phase
characteristics of filters, matching between key components, and key gain blocks. This takes into account process variation
and temperature variation. Calibration occurs transparently during normal operation during the settling time of the hops and
calibrates for temperature variations as the device cools and heats during normal operation in its environment.
Broadcom Corporation
Document 4325-DS04-R
Bluetooth Radio
Page 13
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