Efficient use of available spectrum is a driving factor for increasingly advanced digital modulation of RF channels. Those modulation formats can be classified in numerous ways. For example, modulation can be considered as being over a single carrier or several orthogonal carriers. Either way, the intention is to carry the most information over the spectrum available in the communication channel. In the case of digital television, both approaches are used. Tektronix (Beaverton, OR) offers a primer on making measurements for Digital Video Broadcast Terrestrial (DVB-T) and Handheld (DVB-H) in its white paper, "RF Measurements in DVB-T and DVB-H."
The 40-page paper begins by examining orthogonal-frequency-division-multiplexing (OFDM) modulation with several orthogonal carriers. This type of modulation is used in a number of land-based broadcast systems including DVB-T and DVB-H. Its symbol duration is much longer than that for single-carrier modulations.
The white paper is divided into sections according to power measurements, RF channel-width measurements, continuous-signal interference, and more. It defines each type of measurement, explains its purpose, and then details how it is to be performed. Graphics are provided to further illustrate these points.
This note relies on the TR 101 290 document, which was created by the DVB Measurement Group. Specifically, the paper reviews the RF measurements that are both recommended by that document and appropriate for the use of Real Time Spectrum Analyzers. In doing so, the company shows how those measurements can be performed with existing spectrum analyzers.
Tektronix, Inc., 14200 SW Karl Braun Dr., P.O. Box 500, Beaverton, OR 97077; (800) 835-9433, Internet: www.tektronix.com