A Miniature 900 MHz Frequency-hopping Spread Spectrum Radio

World Wireless Communications Inc. (WWC)
West Valley City, UT

Wireless communications is fast becoming recognized as a flexible and reliable method for data telemetry applications. The technology offers numerous benefits over hard-wired solutions, including lower cost, less environmental impact, system protection and greater flexibility. The radios eliminate the need for miles of expensive wiring as well as the high costs of installation in new sites and retrofitting existing sites. In addition, burying cable and stringing wire are environmentally invasive and require a large investment to restore the area to its original state. Radios significantly reduce the footprint in these installations, minimizing the impact and damage to the area. Furthermore, radios allow for isolation of sensitive equipment, thereby reducing the chance of system failure due to a power surge or lightning strike, and eliminate the chance of broken connections due to damaged or severed cables. In addition, sensors and controllers are no longer tied to the location of the hard-wired terminal, offering flexibility when relocating equipment within a building or over large distances outdoors.

The recently introduced 900 SS MicroHopper™ 900 MHz frequency-hopping spread spectrum data radio provides a high performance, low cost solution to many of the described problems. This miniature radio is ideal for applications such as hand-held data collection, facility access and security systems, irrigation systems, heavy equipment and crane controllers, remote cameras and electronic signs. The MicroHopper is a miniature version of the award-winning 900 SS Hopper digital transceiver released earlier and incorporates a proprietary Secure-Sync™ coding technology that dramatically reduces the overhead inherent in other coding methods. The software adds security, increases throughput efficiency and provides faster effective communication speeds at a much lower cost.

The 900 SS MicroHopper transceiver incorporates networking features typically found only in more expensive systems. For example, it supports multiple network configurations, including point-to-point, point-to-multipoint and multipoint-to-multipoint operation with both client-server and peer-to-peer configurations. The MicroHopper transceiver extends its networking capabilities with a fully addressable guaranteed delivery mode. When operating in this mode, the receiver will confirm the successful receipt of each data packet. If the transmitter does not receive delivery confirmation within a specified time frame, it will automatically resend the data until the packet is successfully delivered. In addition, the MicroHopper radio can act as a repeater radio in the fully addressable mode, thus extending the network’s range and overcoming difficult transmission environments.

Table 1
Microhopper Specifications

Operating frequency (MHz)

902 to 928

Radio type

frequency-hopping spread spectrum digital transceivers

Modulation system

direct FM

Frequency control

PLL synthesizer, 100 kHz step size

Transport protocols

transparent or addressable (guaranteed delivery mode)


full duplex when using guaranteed delivery mode


asynchronous serial - TTL RS-232C

Channel capacity

25 channels, up to 1600 group codes

Channel spacing (kHz)


Repeating capability

user selectable up to seven radios in guaranteed delivery mode

RF data rate (max) (kbps)


Range* (m)

500 line of site

Rx sensitivity (dBm)


RF bandwidth (kHz)


System deviation (max) (kHz)


Input voltage (V DC)


Power consumption (W)


Current consumption (mA)


Output power (mW)

10, 50 and 100 (user selectable)


inlcuded in 20-pin header

Board size (")

1.750 x 2.470 x 0.375

Temperature range (°C)

-40 to +80

Antenna connector

SMA female

Antenna impedance (nom) (W)


*Range will vary depending upon antenna selection, board integration, physical environment and the OEM's device.


Users also can create multiple independent networks via group codes. Using group codes, only radios within the assigned group may communicate with one another, thus isolating other networks of MicroHoppers as well as other radios. Additional benefits and features of the MicroHopper include Windows®-based software for radio configuration, industry-standard TTL serial or RS-232 interface versions and compliance with FCC Part 15 rules for unlicensed spread spectrum communications. The unit supports interface data rates from 2400 bps to 19.2 kbps with an over-the-air rate of 20 kbps, and effective communication distances of five miles (line of sight) are possible. Table 1 lists the 900 SS MicroHopper transceiver’s general specifications.

Fig. 1 The MicroHopper transceiver's mechanical outline The 900 SS MicroHopper Developer Kit is available to aid potential users in evaluating the MicroHopper transceiver. The kit includes two 900 SS MicroHopper transceivers, two customer interface modules with RS-232 DB-9 connections, two flexible whip half-wave antennas with SMA connectors, serial cables and power supplies for both radios, a user’s guide/quick start guide and an easy-to-use Windows configuration utility.

The MicroHopper circuit assembly measures just 2.50" x 1.75", as shown in Figure 1 , and sells for less than $100 each in original equipment manufacturer (OEM) quantities. Additional information may be obtained from the company’s Web site at www.worldwireless.com.

World Wireless Communications Inc. (WWC), West Valley City, UT (801) 575-6600.