FLY E185
Service Manual
CKT Confidential
Page 13 of 47
be input to TX mixed-signal module that contains two DAC for I/Q signal respectively.
Auxiliary Calibration Circuit - 540 kHz Sine:
By setting “1” to SGEN (Sine Tone Generation) in TX_CFG control register, the BBTX output
will become 540 kHz single sine tone, which is used for Factory Calibration scheme for Mixed
Signal Low Pass Filter Cut-off Frequency Accuracy.
GSM Encryptor:
When uplink parts of Baseband Serial Ports pass a TX symbol to GSM Encryptor, GSM Encryptor
will perform encryption on the TX symbol if set “1” to BCIEN (Baseband Ciphering Encryption)
in BFE_CON register. Otherwise, the TX symbol will be directed to GMSK modulator directly.
GMSK Modulation:
GMSK Modulator is used to convert bit stream of GSM bursts into in-phase and quadrature-phase
outputs by means of GMSK modulation scheme. It consists of a ROM table, timing control logic
and some state registers for GMSK modulation scheme. GMSK Modulator is activated when TX
dump window is opened. There is latency between assertion of TX dump window and the first
valid output of GMSK Modulator. The reason is because the bit rate of TX symbols is 270.833
KHz and the output rate of GMSK Modulator is 4.333 MHz, and therefore timing synchronization
is necessary between the two rates. Additionally, in order to prevent phase discontinuity in
between the multiple-burst Mode, the GMSK modulator will output continuous 67.7khs sine tone
outside the burst once RX DAC Enable window is still asserted. Once RX DAC Enable window is
disserted, GMSK modulator will park at DC level.
8PSK Modulation:
8PSK Modulator is used to convert bit stream of EDGE bursts into basically 8 phase I/Q pair
output by means of 8PSK modulation scheme. It consists of a ROM table, timing control logic and
some state registers for 8PSK modulation scheme. The conversion is based on 5 sequential symbol
and performed moving average form the ROM table lookup. 8PSK Modulator is activated when
TX dump window is opened. There is one clock delay between assertion of TX dump window and
the first valid output of 8PSK Modulator. The reason is because the bit rate of TX symbols is
270.833 KHz and the output rate of 8PSK Modulator is 4.333 MHz, and therefore timing
synchronization is necessary between the two rates.
