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RFFM4202

DS120427

7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical

support, contact RFMD at (+1) 336-678-5570 or customerservice@rfmd.com.

Theory of Operation and Applications

Overview

The RFFM4202 is a single-chip integrated front end module (FEM) for high performance WiFi applications in the 2.4GHz to

2.5GHz ISM band. The FEM greatly reduces the number of external components minimizing footprint and assembly cost of the

overall 802.11b/g/n solution. The RFFM4202 has an integrated b/g/n power amplifier, a power Detector, and Tx filtering and

a Switch, which is capable of switching between WiFi Rx and WiFi Tx operations. The device is manufactured using InGaP HBT

and pHEMT processes on a 6mmx6mmx0.95mm Laminate package. The module meets or exceeds the RF front end needs of

the 802.11b/g/n WiFi RF systems. As the RFFM4202 is fully RF matched to 50

 internally and requires minimal external com-

ponents, it is very easy to implement on to PCB designs. To reduce the design and optimization process on the customer appli-

cation, the evaluation board layout should be copied as close as possible, in particular the ground and via configurations.

Gerber files of RFMD PCBA designs can be provided upon request. The supply voltage lines should present an RF short to the

The built-in Power Detector of the RFFM4202 can be used as power monitor in the system. All inputs and outputs are internally

matched to 50

.

Transmit Path

The RFFM4202 has a typical gain of 35dB from 2.4GHz to 2.5GHz, and delivers>27dBm typical output power in 11n HT20

MCS7 and>27.5dBm typical in 11g 54Mbps with an EVM<3%. The RFFM4202 requires a single positive of 5.0V to operate at

full specifications. The VREG pin requires a regulated supply at 2.85V to maintain nominal bias current.

Out of Band Rejection

The RFFM4202 contains a low pass filter (LPF) to attenuate the 2nd Harmonics to -40dBm/MHz (typical). Depending upon the

end-user's application, additional filters may be needed to meet the out of band rejection requirements of the system. For the

system to meet FCC' s spec, a simple LC can be used between FEM and Antenna, for impedance matching and extra Harmon-

ics attenuation to meet spec.

Receive Path

The Rx path has a 50

 single-ended port. The Receive port return loss is 9.6dB minimum. In this mode, the FEM has an inser-

tion loss of 0.8dB and 30dB (typical) isolation to Tx port.

RFFM4202 Biasing Instructions to the Eval board:

802.11b/g/n Transmit:

1. Connect the FEM to a signal generator at the input and a spectrum analyzer at the output. Set the Pin at signal generator is

at -20dBm.

3. Refer to switch operational truth table to set the control lines at the proper levels for WiFi Tx. It is recommended to maintain

at least 2.85V on VTx during Tx mode. A lower VTx voltage will enable the switch in Tx mode, but 2.85V is needed to ensure

that the switch stays in Tx mode during high power peaks. Using a VTx voltage less than 2.85V in Tx mode could result in

abnormal operation or device damage.

or the part may exceed device current limits.

drop the collector voltage significantly if long leads are used. Adjust the bias voltage to compensate.

7. Turn on RF of signal generator and gradually increase power level to the rated power. CAUTION: If the input signal exceeds

the maximum rated power, the RFFM4202 Evaluation Board can be permanently damaged.

802.11b/g/n Receive

• To receive WiFi set the switch control lines per the truth table.