Wireless Systems Design

RFICs Find Applications Everywhere

The growth of smaller, more power-sensitive wireless-communication products has fueled the explosive development of RF integrated circuits (RFICs). Highly integrated RF components now populate ICs, replacing the hybrid circuits that used discrete semiconductor devices. As a result, RFICs can be found in applications that blanket the wireless space, ranging from cellular to wireless LANs and everything in between.

Implementing traditional RF devices on ICs presents many unique problems. These issues include the design of single-chip transceivers, active and passive devices on an IC, and power and noise considerations. To complicate matters, today's wireless engineer must be knowledgeable in the design, simulation, and layout of wireless-communication RFIC chips. Such expertise necessitates the use of sophisticated RF/microwave computer-aided-design (CAD) tool suites, such as Agilent EEsof's ADS and IC layout software and Cadence's Virtuoso. Applied Wave Research's (AWR) Microwave Office 2002 provides RFIC designers with another simulation and layout design toolset. This one includes electromagnetic (EM) analysis capabilities. For the full-chip RFIC verification of wireless applications, many designers turn to Mentor Graphic's Eldo RF simulator.

IF DIRECT CONVERSION
The development of intermediate-frequency (IF) direct-conversion technology is one of the most recent successful applications of RFICs. In this technology, RF signals are converted directly to baseband signals. Perhaps most noticeable in this arena is Parker Vision's Direct2Data (D2D) technology. This company's PV-1000Hb, for example, is a single-chip RF-transceiver IC used in 802.11 applications. The chip provides high-quality, superheterodyne-level RF-to-baseband conversions. Several other RFIC vendors provide direct-conversion or Zero IF chip sets of varying performance levels. Among these chips sets are Qualcomm's RadioOne, Analog Device's Othello, and Infineon Technologies' Single-chip Multi Advanced Radio Transceiver IC Direct Conversion, or SMARTi DC.

The convergence of various wireless networks—from both the datacom and telecom camps—has driven the need for radios that support multiple protocol standards. More often than not, this calls for RFICs that resist interference. Take the typical case of a device that simultaneously operates Bluetooth WPAN and IEEE 802.11b WLAN radios. Because both of these technologies operate in the 2.4-GHz unlicensed band, there is a significant chance of data collisions. Several manufacturers have developed RFIC chip sets that will allow these protocols to coexist in varying degrees of simultaneous operation. Examples include Mobilian's TrueRadio and Blue802, which resulted from the Intersil/Silicon Wave collaboration.

Of course, RFICs already maintained a large market share as a major component of any cellular handset. Many vendors produce RFICs that support the major 2G, 2.5G, and 3G cellular network protocols. Skyworks Solutions, which was formed out of the recent merger of Alpha Industries and Conexant Systems' wireless businesses, provides a family of RFIC subsystems for 2G and 3G Code Division Multiple Access (CDMA) digital cellular handsets.

Now, however, the success of Wi-Fi products—another name for 802.11b-compliant systems—has caught the attention of major telecom vendors and carriers. Multiband, multimode, and multi-protocol RFICs are being developed that will permit cell phones or laptop PCs to connect to either GSM/GPRS or Wi-Fi networks. For example, T-Mobile (formerly VoiceStream) is working with both Nokia and Cisco to bring network integration technology and multimode PC modem cards to market.

A space also is opening up for GPS radio ICs, now that the U.S. Federal Communications Commission (FCC) mandates e-911 capabilities in all new cell phones. Many vendors, such as Tality, Maxim, Analog Devices, Motorola, and Texas Instruments, have developed GPS RFICs. Some, like SiGe Semicon-ductor, have developed such a chip set using a silicon-germanium BiCMOS process. The company's SE4100 GPS Radio IC enables a range of wireless devices with global-positioning capabilities. They range from e-911-enabled cell phones to embedded devices in motor vehicles.

As the cellular industry moves to next-generation networks like 3G, GPS radio ICs will become even more prevalent. Motorola's Personal Communications Sector recently announced that it will integrate SiRF Technologies' GPS chip sets into its 3G devices (see figure). The SiRF radio ICs will provide European and Asian markets with location-based capabilities. RFIC technology can also be found in everything from RF power amplifiers and microelectromechanical-systems (MEMS) switches to RF-identification (RFID) systems and pagers. Obviously, the growth of wireless devices will only hasten the development of new RFIC technologies and products.

TAGS: Intersil
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