Consumer demand for broadband communications services is growing, and one of the key methods for providing such services is digital-subscriber-line (DSL) technology. In support of testing DSL systems, Noise Com (Parsippany, NJ) has developed the model UFX-9835 modem tester, which uses precisely controlled noise to emulate near-end crosstalk (NEXT) and far-end crosstalk (FEXT) for production testing of DSL modems. With the independent noise generators, the UX-9835 provides frequency coverage from 50 Hz to 2 MHz and 3-dB signal bandwidths between 3 and 5 MHz. The instrument can control noise output power from -130 to -140 dBm/Hz. Using the instrument's dual-output capability, noise can be injected to the modem test circuit for simultaneous testing of NEXT and FEXT. The two outputs are each balanced with output impedance higher than 10 kO, meeting the high-impedance crosstalk injection requirements of various T1 standards. The UFX-9835 may also be used for ADSL, HDSL, as well as xDSL modem testing. The tester features high-quality Gaussian noise outputs with peak-to-average voltage (crest factor) of larger than 5:1. (For more on broadband technologies, don't miss the Special Report in the September 2004 issue of Microwaves & RF.)

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