GENERAL PURPOSE Signal analyzers

Signal Analyzer R&S ® FSQ Analysis of VSB signals with the option R&S ® FSQ-K70

While QAM1) methods are gaining Expanded measurement scheme eliminates – as is capabilities typical with conventional cable televi- importance in the European TV stan- sion signals – the lower sideband, yield- The optional Vector ing a virtually Gaussian distribution of dard DVB as cable TV networks are R&S ® FSQ-K70 [2, 3] has supported the the amplitude stages in the imaginary analysis of QAM signals ever since it component (FIG 2). digitized, the US is using a digital was first introduced. It now includes a VSB demodulator, thus expanding its As usual, the unavoidable effects of non- method of vestigial sideband modu- range of applications, and offers all anal- linearities that have to be taken into ysis capabilities that are customary for account when dimensioning output lation (VSB). In the US TV standard QAM (e.g. error vector magnitude (EVM) amplifiers can be checked and optimized and eye diagram). Of course, the option by means of the AM/AM or AM/ϕM ATSC2), 8VSB [1] is used as a digital R&S ® FSQ-K70 also supports conven- conversion curves. FIG 4 shows an exam- tional measurements such as constel- ple of the measurement result for an transmission method. The option lation diagrams, modulation accuracy amplifier. tables (FIG 1) as well as statistical and R&S ® FSQ-K70 now makes measure- spectral evaluations. A new function is the measurement of parameters that are Summary ments on VSB signals possible. typical of VSB signals, such as level error of the pilot carrier. All measurement capabilities and eval- uations of the vector signal analyzer The display capabilities of the option option are also available for the digi- R&S ® FSQ-K70 make it easy to view the tal vestigial sideband modulation (VSB). relationship between two different mod- Thus, you can perform vector signal anal- ulation modes, e.g. 8VSB and 64QAM. ysis on RF, IF and baseband signals with FIGs 2 and 3 show the probability dis- a single instrument. Whether VSB in tributions at the decision points for the America or QAM in Europe, the optional two modes (compare constellation dia- Vector Signal Analyzer R&S ® FSQ-K70 grams in the upper halves of the figures). always has the demodulator you need. In the real component of both modula- tion modes (horizontal axis in each con- Since the new VSB demodulator does stellation diagram), eight amplitude not require any additional measure- More information and data sheet at www.rohde-schwarz.com stages are possible. The 64QAM scheme ment hardware, a simple update to the (search term: FSQ-K70) transmits eight amplitude stages in the latest firmware version of the R&S ® FSQ imaginary component, allowing the data is sufficient. REFERENCES rate to be doubled. In contrast, the 8VSB Jochen Pliquett [1] ”Digital Television – A Practical Guide for Engineers”. Walter Fischer, Springer Verlag 2003 [2] Signal Analyzer R&S ® FSQ – Application software for precise vector signal analy- sis. News from Rohde & Schwarz (2003) No. 178, pp 32–34 [3] Signal Analyzer R&S ® FSQ – New func- tions of the optional Vector Signal Analyzer R&S ® FSQ-K70. News from Rohde&Schwarz (2004) No. 181, pp 27–29 1) Quadrature amplitude modulation. 2) Advanced Television Systems Committee.

34 News from Rohde & Schwarz Number 184 (2004/IV) FIG 1 and modulation accuracy table for 8VSB.

FIG 3 Distribution of real and imaginary components with 64QAM.

FIG 2 Distribution of real and imaginary components with 8VSB.

FIG 4 AM/AM and AM/ϕM conversion curves of an amplifier.

35 News from Rohde & Schwarz Number 184 (2004/IV)