LG ID2750, Service Manual

Page: 20 / 69

LG-ID2750
LGE
LG Electronics Inc.
18/26
[Figure 3-1] Block Diagram Of ID2750
1.2 Description of Receive Part Circuit
1.2.1 Duplexer (DP100)
The duplexer consists of the receive part bandpass filter (BPF) and the transmit part bandpass filter
(BPF) which have the function of separating transmit/receive signals in the full duplex system using
the transmit/receive common antenna. The transmit part BPF is used to suppress noises and spurious
waves entering the receive band among transmit signals in oIDer to prevent the drop in receive
sensitivity characteristics. The receive part BPF blocks the signals sent out from entering the receive
end in oIDer to improve sensitivity characteristics.
Insertion loss (IL) in the transmit band is 2.8dB (Max), whereas IL in the receive band is 2.1dB (Max).
The receive band attenuation amount of transmit filter is 51dB (Min) and the transmit band attenuation
amount of receive filter is 45dB or more (Min).
1.2.2 LNA (U104)
The RFR6122 has cellular LNA. The characteristics of Low Noise Amplifier (LNA) are low noise
figure, high gain, high intercept point and high reverse isolation. The frequency selectivity
characteristic of mobile phone is mostly determined by LNA.
Z3X-BOX.COM