User Guide

6015/6015i/6016i/6019i (RH-55), 6012 (RM-20)

System Module Nokia Customer Care

The receiver supports dual-band and dual-mode operation, including the 800 and

1900 MHz frequency bands for CDMA, as well as the 800 MHz band for AMPS. The

receiver is a dual-conversion, I/Q receiver. The IF and baseband I/Q are common for all

frequency bands. AMPS and CDMA share many of the blocks except for the IF and

baseband filters due to the different bandwidths. The downconversion stage for AMPS

requires less gain due to a lower A/D input voltage, which also increases the dynamic

range of the AMPS receiver.

This can be implemented by using two separate downconverters or by using a gain step

for the mixer section. The I and Q base band filters are fully-integrated, active filters

implemented in the RX IF ASIC. The AGC is implemented using a VGA and by switching

out the LNA in the front end. This provides optimal control of the dynamic range and is

necessary to meet all IMD requirements. At least one switch point is required to meet all

CDMA specifications. The AMPS signal is digitally demodulated by the DSP after being

converted to digital in the UEM. A DC offset compensation system for the I/Q path,

which is incorporated in the RX IF ASIC, is needed in both AMPS and CDMA modes.

The front-end implementation can be done using an RF ASIC that contains all necessary

amplifiers, mixers and switches. Alternatively, a less integrated solution is possible. A

switching mechanism is needed to route the outputs of the mixers to the correct IF filter.

In CDMA mode, both mixer outputs must be routed to the CDMA IF filter, while in AMPS

mode the output of the 800 MHz mixer must be routed to the AMPS IF filter.

The RX IF ASIC is named "Batman D," and is used to convert the IF down to baseband I

and Q. The ASIC contains a VGA section, IQ demodulator, baseband filters (BBFIL) for

AMPS and CDMA, switchable gain baseband amplifier (BBAMP), and an RX VHF PLL. The

I/Q BB signals are output to the UEM chip for analog-to-digital conversion and further

signal processing.