Product Description

Product Description
58 (98) © Nokia Corporation Draft DN991444
Nokia Proprietary and Confidential Issue 3-0 en Draft
Receiver (RX) part
The receiver (RX) part includes a common LNA, FHS and the second LO. The
RF block, two intermediate frequency blocks and AGC are separate for the main
and diversity branches.
The LNA amplifies the signal for the main RX branch and provides diversity
output for the other TRX. The diversity input from the other TRX is fed to the first
mixer of the diversity branch.
The RX paths convert the input signals from the duplex filtering module by
double down-conversion to a final intermediate frequency (IF). Analogue
filtering and an on/off type AGC are included in the first IF. The variable gain
block in the second stage prevents compression by keeping the signal level within
the dynamic range of the output A/D convertor. The signal from the A/D
converter is passed to the Enhanced Down-converter ASIC (ERXA), where
decimation and channel filtering occur. The main and diversity digital signals are
then sent to the BB for DSP processing.
The RF module includes an RX FHS phase-locked synthesizer, for either
frequency hopping between adjacent time slots or providing a fixed frequency
signal in non-hopping mode. The FHS part consists of separate VCO module and
PLL circuits. The RX FHS provides the local oscillator signal in the first down-
conversion stage of both RX chains.
The RX part also provides the local oscillator (LO) for the RX IF sections.
RF Loop part
The RF loop part provides transceiver test loop and antenna monitoring facilities.
The LED display is also included in this part.
The RF loop converts the TX RF signal down to RX frequency. The down-
converted TX signal can be selected as an incident or reflected signal to facilitate
antenna monitoring.
The down-converted signal is coupled to the input of the LNA and input to the
diversity branch mixer. The three time slot delay and BER test are performed by
the DSP SW for both GMSK and 8-PSK.
There is also a reflected power measurement circuit that raises an alarm when the
antenna connector is left open at full power.
Digital part
The digital section of the RF module include two ASICs. These interface to the
BB and provide control and reference signals to, and alarms from, the analogue
functions of the RF module. The Enhanced Up-converter ASIC (EXTA)
incorporates a DDS, generating a modulated signal for the TX. The Enhanced
Down-converter ASIC (ERXA) performs digital channel filtering and controls
AGC.