LG-TM250
1.2 Description of Rx Part Circuit
1.2.1 SP3T switch(U520)
The main function of SP3T switch is to prohibit the other band signals from flowing into the one band circuit
and vice versa. RF designer can use common tri-band antenna regardless of frequency band (800, 1575 and
1900 Mhz). The specification of LG-TM250 SP3T switch is described below:
Cellular GPS PCS
Frequency Range
824 – 894 MHz
1575.42 MHz
1850 – 1990 MHz
Insertion Loss to
Common
0.6dB Max (at +25 deg)
0.7 dB Max. (at +25 deg)
0.8dB Max (at +25 deg)
Isolation
25 dB Min.
Return Loss
-15 dB Min.
Power Capacity
10 W Max.
Temperature Range
-30 to +85 deg
1.2.2 Duplexers (DP100, DP101)
The duplexer consists of the Rx bandpass filter (BPF) and the Tx BPF which has the function of separating Tx
and Rx signals in the full duplex system for using the common antenna. The Tx part BPF is used to suppress
noises and spurious out of the Tx frequency band. The Rx BPF is used to receive only Rx signal coming from
the antenna, which is usually called preselector. It’s main function is to limit the bandwidth of spectrum
reaching the LNA and mixer, attenuate receiver spurious response and suppress local oscillator energy. As a
result frequency sensitivity and selectivity of mobile phone increase. The specification of LG-TM250 duplexer
described below ;
PCS duplexer
Tx
Rx
Tx to Rx (min)
Pass Band
1850~1910 MHz
1930~1990 MHz
Insertion Loss
3.2dB max
3.7dB max
Return Loss
10dB min
10dB min
Attenuation
45dB min (1930~1990MHz)
55dB min
(1850~1910MHz)
55dB (1850~1910MHz)
46dB (1930~1990MHz)
LG Electronics Inc.
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