Antenna Switch - NEC N8 Service Manual

RF PORTION
1. ANTENNA SWITCH AND DIPLEXER SWITCH
External
TX from 900, 1800 &1900

Antenna switch

The RF receiver 3 bands signal (GSM 925MHz – 960MHz, DCS 1805MHz – 1880 MHz
and PCS 1930MHz – 1990MHz) is input via the antenna or coaxial connector J100, The
coaxial connector has a built in mechanical switch, which is used to switch between the
antenna and auxiliary RF input. In normal status, the antenna of the HHP connected
directly to the diplexer.
L101 is employed to block the DC signal from outside. For example: static charge which
may cause harmful to the front-end amplifier or Final power amplifier.
The Diplexer of U101 splits the frequency band of signals, and the switches is used to
control all the Tx and Rx paths. This is achieved using the band selection line FEM1,
FEM2, FEM3.
The received signals passed through the band pass filters and went into receiver circuits.
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