RF3145PCBA-41X RFMD [RF Micro Devices], RF3145PCBA-41X Datasheet - Page 13

• Manufacturer Part Number: RF3145PCBA-41X
• Description: QUAD-BAND GSM/EDGE/GSM850/DCS/PCS POWER AMPLIFIER MODULE
• Manufacturer: RFMD [RF Micro Devices]

Overview
The RF3145 is a dual-mode, quad-band power amplifier module that is compatible with both GSM and EDGE applica-
tions. The device operates in a broad frequency range that includes the GSM850, GSM900, DCS1800, and PCS1900
frequency bands. Integrated band select, mode select, and power control features are also integrated to provide digital
control of various features.
Band select provides digital selection of the GSM850/900 or DCS1800/PCS1900 band. V
the gain in the GSM900 band. Due to gain expansion at input powers below the 1dB compression point, low gain mode
is provided to maintain the noise power performance in EDGE applications. However, this feature is not required in the
DCS1800/PCS1900 bands. Therefore, V
vided in the DCS/PCS band.)
The integrated power control feature employs an indirect closed loop method that uses collector control to regulate out-
put power. Collector control design architecture has several advantages, including simplifying the phone design, as well
as minimizing gain and linearity variation in EGDE applications. Integrated power control eliminates the need for a com-
plicated control loop design. The indirect closed loop is fully self-contained and does not require loop optimization. It can
be driven directly from the DAC output in the baseband circuit.
The RF3145 mode of operation is a function of the input power level and the V
input power is held constant in the range of +2dBm to +5dBm, and the output power is controlled using the V
The required input power for GSM/GPRS applications is typically 3dB to 4dB higher than the 1dB compression point.
GSM/GPRS applications use GMSK modulation, which is constant envelope and is not sensitive to amplitude non-linear-
ities. Therefore the power amplifier may be operated in deep class AB which offers high efficiency. However, in EDGE
applications, the 3π/8 rotated 8-PSK constellation shown in Figure 1 contains both phase and amplitude information.
Therefore, EDGE applications require a linear power amplifier to transfer EDGE modulation with minimal distortion.
Changing V
the V
ered (lower than the 1dB compression point). In EDGE applications, the V
V
this RF ramp input to the power amplifier.
Rev A4 050919
Figure 1. EDGE 3Pi/8 Rotated 8-PSK Constellation
RAMP(MAX)
RAMP
signal is lowered in EDGE applications, the voltage on the collectors of the power amplifiers will also be low-
RAMP
, and the input power is ramped to meet the EDGE burst mask. Typical EDGE systems use a VGA to provide
in linear applications will cause distortion to the EDGE modulated signal, and is not recommended. If
MODE
Theory of Operation
controls only the gain in the GSM850/900 band. (This feature is not pro-
MODE
RAMP
logic level. In GSM applications, the
input should be held constant at
MODE
provides digital control of
RF3145
RAMP
2-531
input.