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3
RF OVERVIEW
3.1 Introduction
3.1.1 General Specifications
GD90 is a Dual Band product incorporating two switchable transceivers, one for the GSM900 band and another for the
GSM1800 (DCS1800) band. The transmit and receive bands for the mobile are given in the table below:
Other salient technical features are as follows:
3.1.2 Description of Main PCB
All components required for the RF and Logic circuits, excluding the LCD module and backlight LEDs, are contained on the
Main PCB. The Main PCB has six layers made from FR4 material (Epoxide woven glass fabric copper-clad laminate as
specified in BS4584 Part 102 and prepeg as specified in BS4584 Part 103). Top and bottom layer tracks are gold-plated to
prevent oxidisation and enable better soldering. The board thickness is 0.9 mm (± 0.1 mm).
The RF components are located on both sides of the upper area of the Main PCB. To provide RF shielding, most of one side
of the Keypad PCB comprises a printed circuit groundplane. The Main board is connected to the Keypad PCB via a 34-way
dual in-line connector. A metallised plastic chassis is used to separate the Main and the Keypad PCB's. When the chassis is
sandwiched between the Main and the Keypad PCB's, the groundplane of the Main board together with the chassis forms an
effective shielded enclosure which prevents spurious emissions. The chassis has also been designed to provide smaller walled
sections which are used to isolate sensitive RF areas such as the VCTCXO and the VCO from high level interferers such as
the PA output.
3.2 Functional Description
3.2.1 Frequency Plan
The GD90 frequency plan is shown below
.
GSM900
GSM1800
MCUK990801G8
Technical Guide
http://cxema.ru
GSM900
GSM1800
Rx Bandwidth
Tx Bandwidth
Duplex Spacing
Number of Channels
ARFCN (Channel Numbers)
1st Tx Channel
Last Tx Channel
1st Rx Channel
Last Rx Channel
Maximum Tx Power
Minimum Tx Power
Tx
GSM900
890-915
GSM1800
1710-1785
Rx
Rx 1st IF
935-960
225
1805-1880
225
Tx
Rx
890-915 MHz
935-960 MHz
1710-1785 MHz
1805-1880 MHz
GSM900
GSM1800
25
75
25
75
45
95
124
374
1-124
512-885
890.2
1710.2
914.8
1784.8
935.2
1805.2
959.8
1879.8
33.0
30.0
(Class 4) (PL5)
(Class 1) (PL0)
5.0
0.0
(PL19)
(PL15)
Tx IF
RFLO Tx
270
1160-1185
130
1580-1655
Rx 2nd IF
RFLO Rx
45
1160-1185
45
1580-1655
Section 3
– 7 –
Units
MHz
MHz
MHz
MHz
MHz
MHz
MHz
dBm
dBm
IFLO Tx
Unit
540
MHz
520
MHz
IFLO Rx
Unit
540
MHz
540
MHz
RF OVERVIEW
Issue 1
Revision 0
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