Motorola M3097 Service Manual download pdf (Page 72)

Motorola Confidential Proprietary

General Description

61

Antenna Circuit

Two RF ports are designed in this trans-

ceiver; internal antenna and external an-

tenna. An RF switch controls which antenna

path is going to be used during operation.

Since this transceiver operates in two fre-

quency bands(800MHz and 1900MHz), the

switch also controls the RF frequency paths.

Only one RF port and frequency band is used

at a time, therefore, only one RF switch con-

figuration is used while the other is

irrevelent.

RX Front End

NADC IC

The NADC/PDC ZIF/SYN is a 2.75 volt 81

pin BGA. It provides two fractional N phase

locked loops for use with external VCOs. The

transmit loop operates at 157.32 MHz in the

cellular band and 192.36 MHz in the PCS

band. The RX loop operates from 981-1006

MHz in the cellular band and from 1021-1051

MHz in the PSC band. The IC also provides

regulator and superfilter functions for its

synthesizer and the external VCOs. The IF

portion of the IC operates with an input fre-

quency of 112.32 MHz. The IC is linear up

to the I and Q outputs of the baseband fil-

ters, can operate with internal or external

AGC, and has a minimum dynamic range of

-96.5 to -5.5 dBm. Both ZIF and SYN sec-

tions of the IC contain battery saving cir-

cuitry controlled by the SPI, and activated

by an external pin.

In 800MHz mode, the receive signal is mixed

with the VCO and the result is the IF signal

which is filtered prior to entering the Cus-

tom IC.

In 1900MHz mode, the receive signal is goes

through a frequency doubler before getting

mixed with the 1900MHz receive signal. This

process allows the 1900MHz carrier fre-

quency to be removed without the need of a

second VCO.

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