Out in Front

UHF ICs form core of simple, effective AM receivers

The 400- to 460-MHz KESTX01 and 290- to 350-MHz KESTX02 UHF transmitters from GEC Plessey use amplitude-shift-keying (ASK) modulation for a data link that spans as far as 50m. The ICs target applications such as keyless-entry systems, remote control, medical-alert pendants, and electronic tagging that need simple, low-power, wireless links. Although ASK is less effective in theory than the more sophisticated and glamorous FSK modulation, ASK is simpler to implement, often sufficiently effective, and immune to multipath fading. You can use the 14-lead ICs with any simple AM receiver, although the vendor does provide a matching KESRX01 receiver.

Each transmitter includes a VCO, PLL, and power amplifier. A 4- to 7-MHz crystal establishes the operating frequency and determines carrier accuracy and drift. You need do no manual tuning in a final design, which reduces cost and simplifies meeting regulatory and electromagnetic-compatibility requirements. These 3.5 to 6.5V ICs require less than 500 nA in power-down mode.

You can use the transmitters with a simple 28337-mm loop antenna. In addition to data sheets, the vendor supplies detailed application notes, an evaluation board, and a collection of frequently asked questions and their answers. The surface-mount plastic ICs cost $1.28 (10,000).—by Bill Schweber

GEC Plessey Semiconductors, Dedham, MA. (617) 251-0117, http://www.gpsemi.com.