Transmitter; General Description - Nokia NHL-2NA Series Troubleshooting Instructions

CCS Technical Documentation

Transmitter

General description

The transmitter chain consists of two final frequency I/Q-modulators, one for E-GSM900
and the other for the GSM1800 band, a dual power amplifier and a power control loop.
The I- and Q-signals are generated by baseband. After post filtering ( RC network) they
go into IQ-modulator in HAGAR. The LO signal for the modulator is generated by the
external VCO and is divided by 2 or by 4 depending on the system mode. There are sepa-
rate outputs one for E-GSM900 and one for GSM1800.
In the E-GSM900 branch, a SAW filter is placed before PA to attenuate unwanted signals
and wide-band noise from the HAGAR IC.
The final amplification is realized with dual band power amplifier. It has two separate
power chains one for E-GSM900 and one for GSM1800. The PA is capable of producing
in excess of 2 W ( 0 dBm input level ) in the E-GSM900 band and over 1 W ( 0 dBm input
level ) in the GSM1800 band assuming a 50 W output. The gain control range is over 45
dB to achieve the desired power levels and power ramp/decay performance.
Harmonics generated by the nonlinear PA are filtered out with filtering inside the
antenna switch -module.
Issue 1 07/02 ¤Nokia Corporation
NHL-2NA
Page 11