Receiver Path - LG -T500 Service Manual

3. TECHNICAL BRIEF
3.7.1 Transmitter path
This module features a fully integrated zero IF transmitter. The baseband transmitted data Is digitally
modulated in the modem block and up-converted the 2.4GHz ISM band in the Transmitter path. The
transmitter path consists of signal filtering, I/Q up-conversion, high -output power amplifier(PA), and RF
filtering. It also incorporates modulation schemes P/4-DQPSK for 2 Mbps and 8-DPSK for 3 Mbps to support
enhanced data rate.
• Digital modulator
The digital modulator performs the data modulation and filtering required for the GFSK, /4DQPSK, and 8-
DPSK signal. The fully digital modulator minimizes any frequency drift or anomalies in the modulation
characteristics of the transmitted signal and is much more Stable than direct VCO modulation schemes.
• Power Amplifier
The integrated PA for the BCM2070 is configurable for Class 2 operation, transmitting up to +4 dBm as well as
Class 1 operation and transmit power up to +12 dBm at the chip, gFSK, >2.5V supply. Due to the linear nature
of the PA, combined with some integrated filtering, no External filters are requires for meeting Bluetooth and
regulatory harmonic and spurious requirements. For integrated mobile handset applications, where
Bluetooth is integrated next to the celluar radio, minimal external filtering can be applied to achieve near
thermal noise levels for spurious and radiated noise emissions.
Using a highly linearized, temperature compensated design the PA can transmit +12 dBm for Basic rate and
+10 dBm for enhanced data rates(2 to 3 Mbps). A flexible supply voltage range Allows the PA to operate from
1.2V to 3.0V. The minimum supply voltage at VDDTF is 1.8V to achieve +10dBm of transmit power.

3.7.2 Receiver path

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 2.4GHz ISM
bnad. The front-end topology, with built-in out -of-bnad attenuation, enables the device to be used in most
applications with no off-chip Filtering.
For integrated handset operation where the Bluetooth function is integrated close to the celluar transmitter,
minimal external filtering is required to eliminate the desensitization of the receiver by the cellular transmit
signal.
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