Panasonic EB-G60 Service Manual page 21

The CX74017 transmitter functional block diagram is shown in Figure 5.2 The transmit (Tx) chain is based on a
translational loop architecture. The baseband information is injected within the loop therefore the output signal is phase-
modulate.
One of the advantages of this architecture is that the Transmit Intermediate Frequency (TxIF) is kept within a narrow
frequency range. This improves phase and amplitude accuracy in the
In-Phase and Quadrature (I/Q) modulator.
The CX74017 has two frequency dividers:
8 D1: set to divide by 9, 10, 11, or 12
8 D2: set to divide by 2 or 1
To minimize the range of the TxIF and the required tuning range of the UHF VCO, the D2 divider is set to /2 mode for low
band operation. Low band operation includes the EGSM. For high band operation, the D2 divider is set to /1 mode.High
band operation includes the DCS1800 .
The UHF VCO is divided by three. After this block, the VCO is multiplied by 1 for low band operation or multiplied by 2 for
high band operation. This block drives both the D1 divider, which feeds the phase detector, and a doubler stage, which
feeds the high side injection down converter 1/2 Local Oscillator (LO) mixer. The mixer mixes the transmit frequency
down to the TxIF frequency that drives the I/Q modulator. The output of the modulator is filtered externally and then fed
back into the CX74017 where it drives the D2 divider. The D2 divider feeds the other input of the phase detector, which
produces an error voltage that is externally filtered. The error voltage tunes the internal Transmit Voltage Controlled
Oscillator (TxVCO).
General
RF circuit design is built around and Skyworks CX74017 IC. Other major components include filters, power amplifiers
and the antenna subsystems.
Direct conversion is employed on both receiver bands.
The Tx VCO is on-channel in both E-GSM 900 and GSM 1800 modes of operation.
The RF LO always requires re-tuning between transmit and receive modes, as well as when monitoring adjacent cells.
Antenna
The antenna is an internal inverted F-type. It is optimized for both free space and talk positions on GSM 900 and GSM
1800 bands. The RF coaxial connector incorporates a mechanical switch for routing the RF signal to an external
antenna for car kit installations and for test purposes.
Transmit and Receive
The transmit and receive paths are covered in their own specific chapters later in this Technical Guide.
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