Only For Training And Service Purposes - LG KP330 Service Manual

3. TECHNICAL BRIEF
3.6.6 UMTS primary Rx RF filter
RF filters are located between the UMTS LNA and the mixer inputs for UMTS 2100, UMTS
1900, and UMTS 1700. Insertion loss is important, but not as critical as losses before the LNA.
The most important parameters of this component include:
Out-of-band rejection or attenuation levels, usually specified to meet these
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conditions:
Far out-of-band signals – Ranging from DC up to the first band of particular concern and
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from the last band of particular concern to beyond three times the highest pass-band
frequency.
Tx-band leakage – The transmitter channel power, although attenuated by the duplexer, still
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presents a cross-modulation threat in combination with Rx-band jammers. The RF filter must
provide rejection of this Tx-band leakage.
Other frequencies of particular concern – Bands known to include other wireless transmitters
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that may deliver significant power levels to the receiver input.
Phase and amplitude balance – The ZIF architecture requires well-balanced differential
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inputs to the RTR6285/RTR6280. This is accomplished by the RF filter, which takes a single-
ended output from the RTR6285/RTR6280 IC, and provides differential outputs having
nominal 180° phase separation. Phase and/or amplitude imbalance degrades common-mode
rejection and second-order, non-linearity so their requirements are specified jointly.
LGE Internal Use Only
KP330 Operational Description
Fig 1.6-5-2 Operating Parameter
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Only for training and service purposes