4.7.1 Transmitter: Modulator and Limited Amplifier
The GMSK modulated signal is generated in the direct modulator. That means, that the
modulators are working directly on the final output frequency. The LO frequency is divided
by 2 or 4, depending on the GSM band. There are two modulators, one for the two higher
bands and the other for the two lower bands..
The required voltages
The actual signal is fed into a limiting amplifier which also provides a signal path for the
high band and one for the low band
EGSM900 limiter enable
GSM1800 limiter enable
The next stage in the low band line-up is a TX saw filter.
In the high band no SAW filter is required.
Pin9 / EN (TXON1/D171_J14))
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Pin10 / BS (OSW1/D720_25)
ICM MP CCQ GRM