RF3158 Просмотр технического описания (PDF) - RF Micro Devices
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RF3158 Datasheet PDF : 26 Pages
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RF3158
Theory of Operation
Overview
The RF3158 is designed for use as the final RF amplifier in GSM850, EGSM900, DCS and PCS handheld digital cellular equip-
ment, and other applications operating in the 824MHz to 915MHz and 1710MHz to 1910MHz bands. The RF3158 is a high
power, dual mode GSM/EDGE, power amplifier with PowerStar® integrated power control. The integrated power control cir-
cuitry provides reliable control of saturated power by a single analog voltage (VRAMP). This VRAMP can be driven directly from a
DAC output. PowerStar®'s predictable power versus VRAMP relationship allows single-point calibration in each band. Single
point calibration enables handset manufacturers to achieve simple and efficient phone calibration during production.
The RF3158 also features an integrated saturation detection circuit, which is an industry first for standard PA module prod-
ucts. The saturation detection circuit automatically monitors battery voltage and adjusts the power control loop to reduce tran-
sient spectrum degradation that would otherwise occur at low battery voltage conditions. Prior to the implementation of the
saturation detection circuit, handset designers were required to adjust the ramp voltage within the system software. RFMD's
saturation detection circuit reduces handset design time and ensures robust performance over broad operating conditions.
The design of a dual mode power amplifier module is a challenging process involving many performance tradeoffs and compro-
mises to allow it to perform well in both saturated and linear operating regions. This is most noticeable in the RF3158 GSM
efficiency. A GSM only part can have its load line (output match) adjusted for maximum efficiency. In a dual mode module, tun-
ing of the load line must be balanced between GSM efficiency and EDGE linearity. The result is slightly lower GSM efficiency
than a single mode (saturated only) power amplifier module. In addition, the RF3158 uses a special GaAs Heterojunction Bipo-
lar Transistor (HBT) process technology which is not used in the most efficient GSM only power amplifiers. The special HBT pro-
cess allows the RF3158 to provide excellent linear performance, Error Vector Magnitude (EVM), and Adjacent Channel Power
Ratio (ACPR), yet maintain competitive GSM efficiency.
Modes of Operation
The RF3158 is a dual mode saturated GSM and linear EDGE Power Amplifier. In GSM mode, the RF3158 is a traditional Power-
Star® module, which means that the output power is controlled by the VRAMP voltage. In EDGE mode, the RF3158 acts as a
gain block where the output power is controlled by the input RF power. The input RF drive level is reduced from GSM mode to
prevent saturation and limit output power. Figure 1 shows the Power Amplifier operating regions in GSM and EDGE mode.
35dBm
29dBm
P1dB
GSM
GMSK
EDGE
8-PSK
Linear Operation
Saturated Operation
Input Power
Figure 1. RF3158 Power Amplifier Operating Regions in GSM/EDGE Mode
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7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.
Rev A2 DS070615
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