ULTRAWIDEBAND (UWB) communications techniques serve as examples of how RF signals and systems are becoming increasingly complex. Clearly, RF engineers need better ways of understanding RF signal behavior and multiplesignal interactions. In "UWB-WiMedia Signal Generation Using Advanced Waveform Editing Tools," Tektronix, Inc. delves into the challenges involved in generating frequency-hopping UWB signals. The 15-page application note also details the options that are available to engineers who are creating UWB-WiMedia signals using an arbitrary waveform generator (AWG).
The UWB-WiMedia approach uses a multiband orthogonal-frequency-division-multiplexing (OFDM) technique to generate test signals. This specification divides the UWB frequency spectrum into six band groups. The first four band groups consist of three bands while the fifth band group comprises two bands. The sixth band group lies within the spectrum of the first four groups.
Each band has a 528-MHz bandwidth. The physical layer utilizes OFDM technology with 122 tones in each of the 528-MHz bands. The OFDM packets are then spread using a timefrequency code. The specification defines two types of spreading: time-frequency interleaving (TFI) and fixed-frequency interleaving (FFI).
RF engineers who are working on UWB products must be able to create signals up to 5 GHz (4 Samples/cycle) in a single instrument. They also need to be able to define the amplitude of the signals in either volts or dBm. AWGs can help them achieve these goals, as they create analog waveforms from sample points. The sample points in an AWG's memory can define just about any waveform. For example, some AWGs can generate 5.8-GHz bandwidth waveforms at 20 GSamples/s.
The second half of the note is devoted to the use of RF/intermediate frequency (IF)/in-phase/ quadrature (IQ) waveform creation and editing tools to generate UWB-WiMedia signals. Such tools, when combined with an AWG, give engineers quicker and simpler ways to create intricate RF signal behaviors and interactions.
Tektronix, Inc.; 14200 SW Karl Braun Dr., P.O. Box 500, Beaverton, OR 97077; (800) 835-9433; internet: www.tektronix.com.
