LGE Internal Use Only
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3.1.3 GSM System Description
The E-GOLDvoice is suited for mobile stations operating in the GSM850/900/ 1800/1900 bands.
In the receiver path the antenna input signal is converted to the baseband, filtered, and then amplified
to target level by the RF transceiver chipset.
Two A-to-D converters generate two 6.5 Mbit/s data streams. The decimation and narrowband channel
filtering is done by a digital baseband filter in each path.
The DSP performs:
1. The GMSK equalization of the received baseband signal (SAIC support available)
2. Viterbi channel decoding supported by an hardware accelerator.
The recovered digital speech data is fed into the speech decoder.
The E-GOLDvoice supports fullrate, halfrate, enhanced fullrate and adaptive multirate speech CODEC
algorithms.
The generated voice signal passes through a digital voiceband filter. The resulting 4 Mbit/s data
stream is D-to-A converted by a multi-bit-oversampling converter, postfiltered, and then amplified by a
programmable gain stage.
The output buffer can drive a handset ear-piece or an external audio amplifier, an additional output
driver for external loud speaker is implemented.
In the transmit direction the differential microphone signal is fed into a programmable gain amplifier.
The prefiltered and A-to-D converted voice signal forms a 2 Mbit/s data stream. The oversampled
voice signal passes a digital decimation filter.
The E-GOLDvoice performs speech and channel encoding (including voice activity detection (VAD)
and discontinuous transmission (DTX)) and digital GMSK modulation.
In the RF transceiver part, the baseband signal modulates the RF carrier at the desired frequency in
the 850 MHz, 900 MHz, 1.8 GHz, and 1.9 GHz bands using an I/Q modulator. The E-GOLDvoice
supports dual band applications.
Finally, an RF power module amplifies the RF transmit signal at the required power level. Using
software, the E-GOLDvoice controls the gain of the power amplifier by predefined ramping curves (16
words, 11 bits).
For baseband operation, the E-GOLDvoice supports:
• Making or receiving a voice call
• Sending or receiving an SMS.
3. TECHNICAL BRIEF
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