![Panasonic EBX70 - CELL PHONE Service Manual Download Page 13](http://html.mh-extra.com/html/panasonic/ebx70-cell-phone/ebx70-cell-phone_service-manual_261923013.webp)
TECHNICAL DESCRIPTION
PMCD030901C8
Section 4
Issue 1
Service Manual
– 11 –
Revision 0
4.1.6.
Antenna
The antenna is a fixed helical type and is designed for triple band operation (EGSM 900, GSM 1800 and GSM 1900).
4.2. Transmitter
4.2.1
Functional Description
Figure 4.3: Transmitter Block Diagram
The transceiver IC (U603) supports quadrature modulation and employs direct modulation. The I, Q signal provided from the
baseband circuits is up-converted to the transmit frequency by this modulator. The required signal path is selected
(EGSM 900 or GSM 1800 / GSM 1900). The signal level is approximately 0 dBm.
The modulated output is fed into the pre-amplifier U604 via SiCu filters FL605 and FL606. The filters suppress third order
harmonics of the modulated signals. Pre-amplifier U604 is a quad band limiter amplifier whose output signal is applied to the
dual input of the triple band power amplifier U601 via Pi attenuators. The Pi attenuators provide a better return loss and
correct input levels for U601. A 3-port EGSM SAW filter FL608 is employed at the EGSM 900 output of U604 to provide extra
filtering of transmitter noise at the bottom edge of the EGSM 900 and GSM 900 bands repectively. FL608 also acts as a balun
between the balanced output of U604 and the unbalanced input of U601.
Filtering of transmitter harmonics, most of which are from the PA, is provided by couplers U609 (EGSM 900) and U607
(GSM 1800 / GSM1900). The output from the couplers is applied to the antenna switch (front end module) FL600 which
provides a connection path via the RF test point to the external antenna.
The coupled outputs are combined at the input of U605, an Automatic Power Control (APC) IC, to control the gain and output
power of the PA. An RF detector in U605 produces a baseband output which is compared with a control signal from the logic
section to produce a control signal for the PA.
10697-1
ATTENUATOR
U604
BUFFER AMP
÷2
÷4
FL608
SAW
FILTER
FL605
FL606
APC
U605
U609
U607
FL600
SWITCH
MODULE
RF TP /
SWITCH
ANTENNA
I
Q
I
Q
U603
RF
VCO
TRIPLE BAND
TRANSCEIVER (PART)
EGSM 900
GSM 1800 / 1900
900
1800 /
1900
x2
U601
TRIPLE BAND
PA
PA RAMP
900
1800 /
1900
Summary of Contents for EBX70 - CELL PHONE
Page 80: ...LAYOUT DIAGRAMS Issue 1 Section 12 PMCD030901C8 Revision 0 78 Service Manual ...
Page 81: ......
Page 82: ...PMCDE UK030902000PJ ...