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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
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 ZIF/
SYN IC.
In 1900MHz mode, the VCO signal 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.
NADC/PDC ZIF/SYN 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
Motorola Confidential Proprietary
General Description
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.
TX Operational Description
For the 800 Mhz band, the TX carrier fre-
quency is generated by mixing the main VCO
signal with the offset VCO.In analog mode,
the Offset VCO is modulated to provide FM.
In digital mode, the mixer output feeds an
IQ modulator which is bypassed in analog
mode.The signal passes through attenuators
before being fed to the driver amplifier with
bandpass filters and then it is sent to the 2
stage power amplifier. The Offset VCO, TX
mixer, IQ modulator and amplifiers are con-
tained within a custom integrated circuit.
The MerlinTX is a custom IC intended to pro-
vide IQ modulator, power control, and exciter
functions for IS-136 TDMA portable cellular
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