LG KS10, Руководство по обслуживанию

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- Tx-band isolation . the transmit channel power also leaks into the receiver. In this case, the leakage
is outside the receiver passband but at a relatively high level. It combines with Rx band jammers to
create cross-modulation products that fall in-band to desensitize the receiver. The required Tx-band
isolation depends on the PA channel power and Tx-band losses between the PA and LNA. Typical
duplexer Tx-band isolation value is 57 dB.
- Passband ripple . the loss of this fairly narrowband device is not flat across its passband. Passband
ripple increases the receive or transmit insertion loss at specific frequencies, creating performance
variations across the bands channels, and should be controlled.
- Return loss . minimize mismatch losses with typical return losses of 10 dB or more (VSWR <2:1).
- Power handling. high power levels in the transmit path must be accommodated without degraded
performance. The specified level depends on the operating band class and mobile station class (per
the applicable standard), as well as circuit losses and antenna EIRP. Several duplexer characteristics
depend upon its source and load impedances. QUALCOMM strongly recommends an isolator be
used between the UMTS PA and duplexer to assure proper performance.
3.5.3 UMTS Power Amplifier (U505)
The AWT6277 meets the increasing demands for higher output power in UMTS handsets. The PA
module is optimized for VREF = +2.85 V, a requirement for compatibility with the Qualcomm® 6250
chipset. The device is manufactured on an advanced InGaP HBT MMIC technology offering state-of-
the-art reliability, temperature stability, and ruggedness. Selectable bias modes that optimize efficiency
for different output power levels, and a shutdown mode with low leakage current, increase handset talk
and standby time. The self-contained 4 mm x 4 mm x 1.1 mm surface mount package incorporates
matching networks optimized for output power, efficiency, and linearity in a 50 Ω system.
3. TECHNICAL BRIEF
Figure 1.5.3-1 UMTS PA functional block diagram