RF7115 Datasheet, PDF (11/22 Pages) RF Micro Devices – QUAD-BAND GSM850/GSM900/DCS/PCS TRANSMIT MODULE

RF7115
Theory of Operation
Product Description
The RF7115 is a high-power, high-efficiency, transmit module (TXM) with fully-integrated power control functionality, har-
monic filtering, band selectivity, and TX/RX switching. The TXM is self-contained, with 50Ω I/O terminals with four RX
ports allowing true quad band operation. The power control function eliminates all power control circuitry, including direc-
tional couplers, diode detectors, and power control ASIC’s, etc. The power control capability provides 50dB continuous
control range, and 70dB total control range, using a DAC-compatible, analog voltage input. The TX Enable feature pro-
vides for PA activation (TX mode) or RX mode/Stand-by. Internal switching provides a low-loss, low-distortion path from
the Antenna port to the TX path (or RX port), while maintaining proper isolation. Integrated filtering provides ETSI com-
pliant harmonic suppression at the antenna port even under high mismatch conditions, which is important as modern
antennas today often present a load that significantly deviates from nominal impedance.
Overview
The RF7115 is a true quad-band GSM850, EGSM900, DCS1800, and PCS1900 power amplifier module with fully inte-
grated power control functionality, harmonic filtering, band selectivity and TX/RX switching. This simplifies the phone
design by eliminating the need for the complicated control loop design, harmonic filters, TX/RX switch and possible
matching components between these. The power control loop can be driven directly from the DAC output in the base-
band circuit. The module has 4 Rx ports for GSM850. EGSM900, DCS1800, and PCS1900 bands of operation. For opti-
mum performance, it is best to use Rx1 and Rx2 for low band, and Rx3 and Rx4 for high band operation. Best forward
isolation can be achieved in these states during the off mode as well. To control the mode of operation, there are four
logic control signals; TX Enable, B1, B2, and B3. Refer to truth table below for mode of operations. If control signals are
limited, eliminate the use of the standby mode and B3 may remain in the high state for all modes of operation. By also
changing the don’t care state (X) of B1 allows minimum control logic switching between on and off states.
Module Control and Antenna Switch Logic
TX_EN
B1 B2
B3
0
0
0
0
0
0
0
1
0
1
0
x
0
0
1
x
0
1
1
x
1
x
0
1
1
x
1
1
TX Module Mode
Stand by mode
RX 1
RX 2
RX 3
RX 4
TX low band (GSM850/EGSM900)
TX high band (DCS1800/PCS1900)
Rev A0 060808
11-375