Out in Front

Instruments simulate wireless transmission paths

A pair of two-channel test instruments from Telecom Analysis Systems gives designers of personal-communications services (PCS) and cellular devices a way to repeatably evaluate their products' performance in the presence of noise, multipath interference, and fading. The TAS 4500 Flex4 RF-channel emulator (from $34,950) measures the performance of a unit under test in the presence of multipath and terrain-induced fading, delay spread, and path loss. The unit, which has selectable 6- or 15-MHz bandwidth and 114-dB dynamic range, handles relative path loss as high as 50 dB and relative path delay as large as 1.6 msec. The instrument, which also performs active-terrain emulation at log-normal rates as high as 20 Hz using Rayleigh, Rician, frequency-shift, phase-shift, or Suzuki modulation, allows you to choose Jake's method or filtered-noise-emulation fading models and lets you select the fading-sequence length.

The TAS 4600 noise-and-interference emulator (from $38,950) tests cellular and PCS devices in the 800- to 1000- and 1700- to 2000-MHz bands. The unit's testing of code-division multiple-access (CDMA) devices exceeds the requirements of IS-97A and -98A standards for base-station and mobile-equipment testing. The input-power range is –10 to –70 dBm; the output-power range is 0 to 75 dB in 0.1-dB steps from a source resistance of 0.1V (optionally, 0.25V). The carrier-to-interference power ratio ranges from –20 dB to greater than +30 dB and is accurate within ±0.2 dB. The instrument, which incorporates a precision power meter for calibration, stores its own calibration constants.

You can upgrade either unit via a plug-in PCMCIA card that stores the firmware. Both instruments include RS-232C and IEEE-488 interfaces, which allow the instruments to work with the vendor's Taskit for Windows software. With the aid of this software, you can completely specify complex test sequences.—by Dan Strassberg

Telecom Analysis Systems Inc, Eatontown, NJ. (908) 544-8700, fax (908) 544-8347, 76546.2344@compuserve.com, http://www.taskit.com.