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Most RF designers have faced the so-called front-end problem, which concerns the circuits that connect the antenna and the RF/baseband chip. It derives from the diverse nature of the circuits that make up the front end—the low-noise amplifier, the high-power power amplifier (PA), the transmit/receive (Tx/Rx) switch, and various impedance matching circuits and filters, each of which typically requires a costly and complex mix of individual parts from diverse sources, not to mention different process technologies.

The RF Axis RFX2401 only needs a separate band-pass filter between the RF transceiver and baseband chip and the front end.

Thanks to the extensive RF Axis patent portfolio, all that circuitry now fits inside a tiny biCMOS chip. The result is reduced complexity, shorter design time, lower manufacturing costs, and a reduced bill of materials. The RFX2401 targets Bluetooth class 1 and single-port ZigBee applications in the 2.4- to 2.5-GHz band. The RF front-end integrated circuit (RFeIC) connects directly to the single-chip wireless transceiver via a bandpass filter (Fig. 1). The only other part required is a single bypass capacitor (Fig. 2).

The transmit signal chain gain is 21 dB, and the output power for the enhanced data rate (EDR) 3-Mbit/s Bluetooth with eight-phase-shift keying (8PSK) modulation is 16 dBm. The output power for ZigBee with 250 kbits/s with offset quadrature phase-shift keying (OQPSK) modulation is 20 dBm. The receiver LNA gain is 10 dB with a noise figure of 3 dB. Tx/Rx switch insertion loss is zero. The 16-pin, quad flat no-lead (QFN) package measures 3 by 3 by 0.9 mm.

The RF Axis RFX2401/2 evaluation board only needs a single external bypass capacitor. All other front-end circuitry, including the LNA, PA, Tx/Rx switch, filter, and impedance matching circuits, are in a single biCMOS chip.

The RFX2402 is designed for wireless local-area network (WLAN) applications in 802.11n or 802.11g access points, PC cards, and other Wi-Fi products. The receive signal chain gain is 8 dB, and the transmit power output is 15 dBm using 54-Mbit/s orthogonal frequency-division multiplexing (OFDM) in 11n or 11g applications. The Tx power is 19 dBm with 802.11b applications. The RFX2405 is a dual-Rx/Tx device for combined Bluetooth/WLAN applications. A 5-GHz version is in development. The RFX2401 and RFX2402 are sampling now.