Wireless Systems Design

Transceivers Make Wireless Easy

This Transceiver Family Provides Designers With The Range, Power Consumption, And Size Options That They Need To Optimize Their Wireless Embedded Communication Applications.

The desire for wireless embedded communications is quickly gaining ground. After all, wireless technology gives users unrestricted access to different locations. At the same time, it eliminates the need for costly wiring. Consider, for example, a remote-monitoring application. In such a scenario, a wireless transceiver might be used to remotely monitor the health of a series of Xerox machines. A technician could then be notified of errors or problems on the machines without ever having stepped foot on the site. Obviously, the use of wireless technology offers a hefty slew of benefits. Yet its overall implementation is anything but easy. The engineers who want to incorporate wireless technology often find themselves in new territory. Suddenly, they have to face the unknown world of RF technology. This task can be quite daunting, to say the least.

Now, hope has come to those engineers who want access to wireless functionality, but don't have the time to become wireless or RF technology experts in the bargain. Xecom, Inc. has come to market with a family of smart wireless transceivers that promises to make wireless as easy to use as possible (FIG. 1). Best of all, the XE900S family of transceivers boasts a range of 300 to 1500 ft. In contrast, other transceivers may have limited range due to interference from obstacles like walls, machinery, and noise. Their range makes the Xecom transceivers ideal for a wide variety of point-to-point, point-to-multipoint, or peer-to-peer applications including commercial data transactions, industrial control, and factory-floor automation.

The XE900S transceiver family is comprised of three models: the XE900S-500, XE900S-10, and XE900SL10. These three variations give the system designer options in terms of communications range, power consumption, and module size (FIG. 2). Each model consists of a 900-MHz transceiver, communications controller, and embedded firmware (FIG. 3). Such integration minimizes cost, simplifies access to RF data communications, and reduces design time.

The XE900S family employs the frequency-hopped spread-spectrum (FHSS) modulation scheme. An embedded communications controller manages the modulation along with the host system interface. By using FHSS, the transceivers gain greater range and signal penetration than they would obtain with other modulation schemes. As an added benefit, each family member is FCC Part 15 certified. This aspect is crucial, as the use of an uncertified component often translates into a design-completion delay. Typically, this type of delay is caused by the need to apply patches in order to bring the circuit into FCC compliance.

UNDER THE HOOD
What differentiates each member of the XE900S family? According to the company, the answer is simple: size, output power, power consumption, range, and price. Consider, for example, the XE900S-500. It has a maximum power output of 500 mW and a range of 1500 ft. (even through obstacles). Its line-of-sight range is 20 miles. The XE900S-500 also has a maximum over-the-air data rate of 76.8 Kbps half-duplex. Its power consumption is 3.3 W, given 1000 mA at around 3.3 V and a transmit power output of 500 mW.

By comparison, the 10-mW output-power capability of the XE900S-10 and XE900SL10 provides 300 ft. of obstructed range and 2 miles of unobstructed range. Both models also flaunt an over-the-air data rate of 76.8 Kbps. Yet the XE900SL10 consumes just 165 mW, given a signal transmitting at 50 mA at around 3.3 V and 10 mW of power. All three transceiver models feature a receive sensitivity of −100 dBm provided by use of Xemics' XE1203 RF chip.

The XE900SL10 also differentiates itself from the other family members with its impressively small design. This transceiver measures just 1 in.2 Its small size and extremely low power consumption make the XE900SL10 perfect for portable and battery-powered applications.

With such a complete range of characteristics to choose from, a designer can make a transceiver selection based on what variation is best suited to a given application. The solution can then be further tailored to the application through the use of AT commands. According to Steve Clary, Xecom's Vice President of Marketing, "Parameters such as node addresses and output power can be altered as required for the application. For simple applications, six I/O lines on the XE900S connect directly to the communications controller, thereby allowing the system to operate without a host microcontroller." Additional features, such as a simple serial interface or clip-on antenna connector, further add to the XE900S family's configurability.

A STEP AHEAD
Two proprietary features set the XE900S family of wireless transceivers apart from the competition. The first feature, Count-Off, works to dramatically enhance network-information-processing efficiency through the rapid evaluation of node status. It allows the network master to retrieve the status of over 200 remote nodes in less than 10 sec. with a single broadcast command. This capability makes the family well suited for inventory monitoring or any other task that requires some level of routine function.

The other unique capability, Sensor-OnAir, eliminates the need for an application microcontroller. Instead, it utilizes the communications controller to directly manage analog inputs and digital control lines. Today, many embedded applications are used to monitor elements like pressure or temperature. In such applications, sensors are required system components. With SensorOnAir, the user has a direct connection of sensors to the wireless transceiver. In fact, each node can monitor up to six sensors. Consequently, designers will no longer need an additional controller in the circuit to handle either sensors or control lines.

The XE900S family, which includes the XE900S-500, XE900S-10, and XE900SL10 models, is available now. The XE900S-500 and XE900S-10 come in a 1.295-×-1.41-×-0.255-in. hybrid module. The XE900SL10 is packaged as a 1-×-1-×-.26-in. hybrid module. Each transceiver has an operating temperature of −40° to 85°C. In unit volumes of 50,000 or more, the XE900S-10 and the XE900SL10 sell for $19.95. The XE900S-500 sells for $39.00. Xecom also offers a development kit for the family. It has a unit price of $295.00. That kit includes two XE900S modules and development boards, an RS-232 cable, power supply, two antennas, datasheets, and instructions.

Xecom, Inc.
374 Turquoise St., Milpitas, CA 95035; (408) 942-2210, FAX: (408) 942-1346, www.xecom.com.

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