Electronic Design

Wi-Fi Power Amp Maximizes Data Rate And Range

The RangeCharger SE2525L power amplifier (PA) fills a glaring void in modern WLAN-connected laptops. This PA for 802.11b and the newer 802.11g Wi-Fi transceivers includes advanced features that ensure maximum output power, minimum data errors, and higher speed over a longer distance.

The SE2525L delivers +19-dBm output with an error vector magnitude (EVM) of 3% in either the 802.11b or 802.11g modes. EVM is a phase error that occurs when the points in an I/Q constellation diagram of the modulated signal aren't where they're supposed to be. Phase noise in the voltage-controlled oscillator, some types of filtering, and nonlinearity in the PA all cause EVM. Low EVM translates into lower bit error rate (BER), lower packet error rate (PER), and greater transmission speed. Also, the device meets all Adjacent Channel Power Ratio (ACPR) requirements at +23 dBm and reduces harmonic content.

The device contains an integrated power detector that's not internally connected to the PA output (see the figure). Instead, the power detector can be connected externally through a low-cost printed-circuit directional coupler, where a small portion of the signal is tapped off and sent to the power detector. This arrangement prevents reverse power caused by antenna mismatches from getting back into the power detector, and it keeps power from being varied in the wrong direction.

The on-chip power detector and directional coupler minimize antenna mismatches, improving signal strength and range. The SE2525L achieves a match accuracy of 1 dB, compared to the traditional 4 to 5 dB of competitive PAs. It operates from 2.7 to 3.6 V dc.

The device comes in a 4- by 4-mm 16-pin LPCC package. Price is $1.59 in 10,000-unit quantities, with samples available now and full production available in November.

SiGe Semiconductor

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