Electronic Design

WiMAX Chip Sets Address Exploding Broadband Wireless Market

WiMAX no longer means endless hype or a wireless broadband dream. Services are rolling out from companies like Clearwire and Sprint Nextel.

This means a growing number of WiMAX subscribers and the rising demand for set-top boxes, home gateways and routers, PC cards, laptops, and other devices. Multiple companies are responding to this need, like Beceem Communications and Maxim Integrated Products.

Beceem's BCS200 Wave 2-compliant chip set consists of the BCSB200 baseband IC and the BCSR200 RFIC. Together, they provide everything you need to build a WiMAX transceiver that meets IEEE 802.11e (mobile WiMAX) and Korea's WiBRO equivalent.

The set's dual receivers and single transmitter permit the implementation of a simple multiple-input/multiple-output (MIMO) arrangement that mitigates the multipath and fading so common in microwave bands. Beceem recently demonstrated an aggregate downlink and uplink throughput of 33 Mbits/s using the BCS200 chip set.

The BCSR200 direct-conversion transceiver operates from 2 to 4 GHz and can handle channel bandwidth of 5, 7, 8.75, and 10 MHz. It also supports quadrature phase-shift keying (QPSK), 16QAM (quadrature amplitude modulation), and 64QAM for both uplink and downlink. Convolutional turbo coding and standard convolutional coding are included. And, the chip provides two receive chains and one transmit chain to handle the MIMO.

The BCSB200 baseband chip is fully software programmable with scalable orthogonal frequency-division multiple access (OFDMA) physical-layer (PHY) and media-access controller (MAC) functions. The MAC facilitates various quality-of-service (QoS) classes for voice, data, or video traffic.

Support is also provided for Advanced Encryption Standard (AES) encryption and EAP-based (Extension Authentication Protocol) authentication schemes as well as IPv4 or IPv6 and header compression. The interfaces provided include 10/100 Ethernet, SDIO/SPI, USIM/UICC, USB 2.0, and Cardbus. Samples and reference design kits are available right now.

Maxim's MAX2837, a single-chip transceiver for the 2.3- to 2.7-GHZ band, is optimized for high-volume WiMAX 802.16-2004, 802.16e mobile, WiBRO, or proprietary broadband wireless applications (see the figure). This chip's zero-IF architecture is designed to save over 50% of bill-of-materials (BOM) costs over existing two-chip super-heterodyne solutions by eliminating the surface-acoustic-wave (SAW) filter and a second voltage-controlled oscillator (VCO).

Monolithic baseband filters for both transmitter and receiver are fully integrated. The MAX2837 supports up to 2048 fast Fourier transform (FFT) OFDMA for any or all versions of WiMAX, WiBRO, or future Long Term Evolution (LTE) versions of 4G cell phones. Channel bandwidths from 1.75 to 28 MHz, based on the country's regulations or the application, can be selected via the serial peripheral interface (SPI) and appropriate external programming.

The MAX2837 uses Maxim's in-house high-performance silicon-germanium (SiGe) biCMOS process. The result is a receiver with a low 2.3-dB noise figure, –11-dBm input IP3, –40-dBc integrated VCO phase noise, and 250-mW power consumption. The receiver error vector magnitude (EVM) is better than–35 dB, and sideband suppression is greater than 45 dB.

The transmitter delivers 0-dBm linear output with a 64QAM signal, greater than 45-dB sideband suppression, and better than –36-dB EVM while meeting a –70-dBr spectral mask. The high linearity of the transmitter output allows this device to be used in WiMAX micro or pico basestations in addition to subscriber customer premise equipment (CPE) or PC card devices.

The MAX2837 comes in a 6- by 6mm thin quad flat no-lead (TQFN) package and operates from a single 2.7- to 3.6-V supply. Pricing starts at $8.38 in 1000-unit lots.

Beceem Communications
Maxim Integrated Products

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