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Microwave RF Transceiver Accelerates WiMAX Development

WiMAX equipment is now being developed for consumer broadband and back-haul wireless applications. Based on the IEEE 802.16-2004 standard, WiMAX is getting easier to design every day. SiGe Semiconductor's latest WiMAX chip set should speed the creation of new set-top boxes and basestation systems (Fig. 1).

The SE7051L IF transceiver is a biCMOS device that interfaces directly with most commercially available baseband controllers (Fig. 2). It features low noise and high linearity, and it has selectable IQ or bandpass I/O interfaces. It operates from 10 to 70 MHz and requires only a single IF filter. Also included are dual IF and RF synthesizers as well as a high-speed digital variable gain control delivering 50 dB of gain control. The package is a 56-pin QFN that measures 8 by 8 mm.

Two versions of the RF transceiver are available, so designers can comply with most worldwide frequency assignments. The SE7351L covers the 3.3- to 3.7-GHz range used in Europe and some Asian areas. The SE7251L covers 2.3 to 2.7 GHz, which is used in the U.S. Both deliver the low phase noise and high linearity necessary for high-level modulation schemes like quadrature amplitude modulation (QAM) in orthogonal frequency-division multiplexing (OFDM).

The receiver has a third-order intercept figure of +5 dBm. The noise figure is less than 6 dB, including the switch and filter losses. The total RF gain is 100 dB with an automatic gain control (AGC) of 40 dB gain-control range. The transmitter section is optimized for OFDM and supports frequency-division duplex as well as time-division duplex (TDD) operation.

The RF transceivers are housed in a 40-pin QFN package measuring 6 by 6 mm. These ICs are made with gallium-arsenide (GaAs) heterojunction bipolar transistor (HBT) technology. An external power amplifier, also available from SiGe Semiconductor, is required.

The SE7380L is a GaAs pseudomorphic high-electronic-mobility technology (PHMET) single-pole, double-throw (SPDT) switch used for transmit-receive switching. It has low insertion loss and high linearity for maximum dynamic range with OFDM and high-level modulation schemes.

Samples are available now, with full production starting late this summer. The price per chip set is expected to be about $30 in volume quantities. A reference design with schematics, bill of materials, and design files is available.

SiGe Semiconductor Inc.

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