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3.2.2 GSM Transmitter
The RTR6280 transmitter outputs(HB_RF_OUT2 and LB_RF_OUT1) include on-chip output matching
inductors. 50ohm output impedance is achieved by adding a series capacitor at the output pins. The
capacitor value may be optimized for specific applications and PCB characteristics based on pass-band
symmetry about the band center frequency. The suggested circuit is shown in [Fig. 1.3].
The RTR6280 IC is able to support EGSM900 and DCS1800/PCS1900 mode transmitting. This design
guideline shows a tri-band GSM application.
Both high-band and low band outputs are followed by resistive pads to ensure that the load Presented
to the outputs remains close to 50ohm. The low-band GSM. Tx path also includes a Tx-band SAW filter
to remove noise-spurious components and noise that would be amplified by the PA and appear in the
GSM Rx band.
[Fig. 3.2.3] GSM Transmitter matching
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