User Guide

Back-up battery interface connections and electrical characteristics
Table 21 Back-up battery connections
Pin name I/O Connection Notes
VBack -> N2200,
VBack
Back-up battery G2200 is
connected to N2200
Table 22 Back-up battery electrical characteristics
Description Parameter Min Typ Max Unit
Back-Up
Battery
Voltage
Vback 0 2.5 2.7 V
RF description
Introduction to receiver functionality
Receiver functions are implemented in an RF ASIC.
The receiver is a linear direct conversion receiver consisting of separate front ends (LNA (Low Noise Amplifier)
and demodulator) for each supported system. After the demodulators, the signal paths are combined to one
common BB path.
WCDMA receiver functionality
In the WCDMA mode, the received signal is fed from the antenna to a duplex filter. After the duplex filter the
signal goes via a balun to an LNA (Low Noise Amplifier) residing in N7500. From the LNA, the signal goes
trough a band pass filter.
After filtering, the signal goes to the down conversion mixer, which converts the signal to baseband I and Q
signals. At the BB frequency the signal is amplified, and fed to a low pass filter. The Rx channel filter must be
calibrated with an automatic routine whenever the Rx ASIC IC is changed to a phone.
In the WCDMA mode, the corner frequency of the filter is set to approximately 2.1 MHz. The filter is followed
by an AGC (Automatic Gain Control) amplifier with an adjustable gain. The signal is further amplified before
it is fed to balanced analogue IQ output pins. The analogue output pins are accompanied by reference voltage
output, which sets the DC level for the AD converter in the BB ASIC RAP.
The last stage of the RF Rx chain is an output buffer which feeds the signal and a reference voltage (VREFCM)
to the BB ASIC.
GSM receiver functionality
As GSM Rx branches are functionally identical, the following description is applicable to all of them.
The received signal goes from the GSM antenna to the antenna switch module.
The antenna switch module is followed by integrated LNAs residing in the Rx ASIC.
The LNAs are followed by demodulators which downconvert the signal to baseband I and Q signals.
After the down conversion mixer, the Rx chain is similar to the WCDMA Rx. The channel select filter is set to
115 kHz in the GSM mode.
RM-10;RM-24
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