Service Manual

temperature.
2.3. Upconverter (U104)
Upconverters made up of a mixer part and Driver AMP part. The mixer part is used to receive
double-balanced OUT+ and OUT- of transmit AGC from baseband and mix the output of VCO (U171) with UHF
output signal, whereas the Amp part is used to buffer the output of this mixer. U105 has the operation range of
RF500MHz~1500MHz and has the conversion gain of 0 dB. In addition, the suppression of spurious signals which
are unwanted noise is about 30 dBc when being compared to RF output. The IF input signal range of the mixer is
DC~200MHz. The isolation on RF output terminal and LO signal input terminal at the IF input terminal is 30dB.
The range of LO signal that can be inputted is 300~1700MHz and power level is -6~0 dBm.
2.4. Transmit Bandpass Filter (F102, F103)
Transmit signals that have been converted from IF signals into RF signals after passing through the upconverter
U105 are inputted into the Power Amp U102 after passing once again through RF BPF F102 in order to filter out
noise signals amplified during the amplification of RF signals after going through upconverter(U105). This is carried
out in order to create power level inputted to the Power AMP via RF BPF F102. IL of two RF BPFs is 4dB as a
maximum, whereas the ripple in the passing band is 2dB(maximum). The degree of the suppression of transmit
signals on receive band is at least 20dB or greater. The maximum power that can be inputted is about 25dBm.
2.5. Power Amplifier (U102)
The power amplifier U102 that can be used in the CDMA and FM mode has linear amplification capability,
whereas in the FM mode, it has a high efficiency. For higher efficiency, it is made up of one MMIC (Monolithic
Microwave Integrated Circuit) for which RF input terminal and internal interface circuit are integrated onto one IC
after going through the AlGaAs/GaAs HBT (heterojunction bipolar transistor) process. The module of power
amplifier is made up of an output end interface circuit including this MMIC. The maximum power that can be
inputted through the input terminal is +17dBm and conversion gain is about 28dB. RF transmit signals that have
been amplified through the power amplifier are sent to the duplexer and then, sent out to the cell site through the
antenna in order to prevent any damages on circuits, that may be generated by output signals reflected from the
duplexer and re-inputted to the power amplifier output end.