Hisense EG59, Техническое руководство, Страница: 7 / 13

Page 7 of 13
frequency synthesized unit, receiving unit, transmitting unit.
4.1.1.2.1 Antenna unit
This unit is composed by antenna groupware, antenna switch, diplexer
and duplexer.
This antenna groupware is the transceiver of the wireless signal that is
composed by intside antenna, and could fetch up the disadvantages
such as the low efficiency and the poor radiancy direction by the high
performance match. This phone has the antenna switch, diplexer and
duplexer. The antenna switch is used as the auto-test mechanical
switch, which is located at the RF channel and parallel connected to
the antenna to reduce the 0.47dB loss during using. When producing
and testing, it is connected to the test cable. Duplexer is used to
isolate the received and transmitted signals, which can reduce the
interference.
4.1.1.2.2 Frequency-synthesized unit
QSC6085 platform has a high integration on the frequency-synthesizing
and a flexible design project, which is composed of the following circuits:
crystal oscillator (XO) 19.2MHz, Loop filter and QSC6085 power
management. Crystal oscillator (XO) is provided to TX and RX as the
fiducially source, and also is provided to QSC6085 as the clock source
buffered and filtered by inside power management.
4.1.1.2.3 Transmitting unit
Mainly the following circuits compose this unit: Tx SAW filter, Power
amplifier, burst mode/PA-ON control circuit and high power detect
circuit. CDMA 1X signal is output from QSC6085. For transmitting the
power control correctly, QSC6085 outputs TX_AGC_ADJ PDM signal to
control the output power. PDM pulse wave can realize the plus control
beyond 85dB by RC filter circuit. The frequency of the output signal is
conversed up from analog base band signal to 824MHz-849MHz mixed
by UHF_LO. Output signal go through TX SAW filter (836.5MHz+/-
12.5MHz) to power amplifier, and then output to duplexer. The duplexer
has 55dB isolation to the receiver unit.
4.1.1.2.4Receiving unit
The duplexer gets the 869MHz-894MHz signals received from the
antenna. To the transmitting loop, the duplexer has 56dB isolation, and
the insertion loss of the duplexer is 2.2dB. After entering the integrated
low noise amplifier embedded in QSC6085 chip, the low noise amplifier
has gain switch function, when there are stronger interfering signals
coming in the received band, the gain will be reduced, which will