Nokia 8390 Manuales De Servicio

PAMS Technical Documentation

System Module & UI

NSB-8

Issue 1 01/02

ãNokia Corporation

Page 27

This RF module takes care of all RF functions of the engine. RF circuitry is located on one
side (B-side) of the 8-layer PWB. The PWB area for the RF circuit is about 17 cm

²

.

EMC leakage is prevented by using a metal B-shield, which screens the whole RF side of
the engine. The conductive silicon gasket is used between the PWB and the shield. The
metal B-shield is separated into three blocks. The first one includes the Voltage Con-
trolled Oscillator (VCO). The second block includes the PA, antenna switch, LNAs and RX
SAW. The last block includes the Hagar RF IC, VCO, VCTCXO, baluns and balanced filter
for RX. The blocks are divided on the basis that the attenuation between the harmonics
of the transmitter and the VCO signal (including Hagar IC) is a high (over 100dB). The
VCO and TX outputs of the Ha gar RF IC are located as far as possible from each. In order
to guard against the radiated spurious inside the blocks, the RF transmission lines are
made with striplines after PA.

The baseband circuitry is located on the A-side of the board, which is shielded with a
metallized coated frame and a ground plane of the UI-board.

The maximum height inside the B-side is 1.8 mm. Heat generated by the circuitry will be
conducted out via the PWB ground planes and metallic B-shield