Agilent Measurement Journal - Issue 4 - 2008 - (Page 51)

Combining several measurements gives statistical uncertainty values for the modulation waveform. The waveforms must be aligned, correcting the phase rotation and residual frequency offset before they can be averaged. Typical measured results (three pilot tones x 10 acquisitions) for an Agilent N5182A MXG vector signal generator at 900 MHz show RMS deviations from the mean of < 0.25 percent for an average of 10 aligned traces (Figure 8). The EVM and the uncertainty of the EVM, calculated from the modulation waveform and its uncertainty, was measured as 0.41 ± 0.02 percent, which is considerably less than the typical value (0.8 percent). 1.5 1 0.5 Quadrature 0 -0.5 -1 -1.5 -1.5 -1 -0.5 0 In-phase Signal track Signal error x 100 Symbols 0.5 1 1.5 Communications is a constantly evolving ﬁeld and the supporting metrology must evolve at a similar rate. With the future rollouts of WiMAX and UWB, RF spectrum availability will move to higher frequencies and data rates. As the volume of data becomes excessive, this will provide new challenges for RF waveform metrology based on oscilloscopes. References 1. www.npl.co.uk/wireless_communications/digital_comms_ parameters 2. Agilent Application Note 1356, Designing and Testing W-CDMA User Equipment. Publication number 5980-1238EN available from www.agilent.com. 3. Agilent Application Note 1355, Designing and Testing 3GPP W-CDMA Base Transceiver Stations. Publication number 5980-1239EN available from www.agilent.com. 4. 3GPP TS 34.121 V5.6.0: Terminal conformance speciﬁcation; Radio transmission and reception (FDD). 5. Humphreys, D.A., Dickerson, R.T. 2007. Traceable Measurement of Error Vector Magnitude (EVM) in WCDMA Signals. 2007 International Waveform Diversity & Design Conference, Pisa, Italy, June 4-8, 2007: 270-274. 6. www.npl.co.uk/measurement_for_innovators/ 7. www.bristol.ac.uk/ccr/ 8. Harper, M.R., Smith, A.J.A., Basu, A., and Humphreys, D.A. 2004. Calibration of a 70 GHz Oscilloscope. CPEM 2004. London, June 27 to July 2, 2004: 530-531. 9. Paulter, N.G., Smith, A.J.A., Larson, D.R., Sounders, T.M. and Roddie, A.G. 2003. NIST-NPL interlaboratory pulse measurement intercomparison. EEE Trans. Instrum. & Meas., Vol. 52, No. 6, Dec 2003: 1825-1833. 10. Bieler, M., Seitz, S., Spitzer, M., Hein, G., Pierz, K., Seigner, U., Basu, M.A., Smith, A.J.A., and Harper, M. 2007. Rise-time calibration of 50-GHz sampling oscilloscopes: intercomparison between PTB and NPL. IEEE Trans. Instrum. & Meas., Vol. 56, No. 2, April 2007: 266-270. 11. Smith, A.J.A., Roddie, A.G., and Henderson, D. 1996. Electro-optic sampling of low temperature GaAs pulse generators for oscilloscope calibration. Optical and Quantum Electronics, 28 (1996): 933-943. “WiMAX” is a trademark of the WiMAX Forum. Figure 8. Typical W-CDMA modulation waveform results for 30 traces (red). The error between different results sets is < 0.25 percent (blue). Conclusion As test equipment and RF modulation formats become increasingly complex, it becomes more difﬁcult for instrument manufacturers to prove equipment speciﬁcations. Agilent and NPL have collaborated to develop RF waveform metrology into a powerful tool that traceably links industrially important W-CDMA test equipment to primary standards. As one example, the measured EVM performance of the Agilent N5182A MXG vector signal generator is considerably better than the typical speciﬁed value. NPL has also used these techniques to help Bristol University diagnose subtle faults in signal coding. Agilent Measurement Journal 51 http://www.npl.co.uk/wireless_communications/digital_comms_parameters http://www.npl.co.uk/wireless_communications/digital_comms_parameters http://www.agilent.com http://www.agilent.com http://www.npl.co.uk/measurement_for_innovators/ http://www.bristol.ac.uk/ccr/

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 4 - 2008

Agilent Measurement Journal - Issue 4 - 2008 Delivering Confidence through Compliance with Standards Contents Emerging Innovations Trying Early Device Implementations at the IEEE 1588 PlugFest Achieving Greater Confidence in Measurement Accuracy through Consistency in Calibration Services Overcoming the Challenges of RFID Component Testing 3GPP LTE: Introducing Single- Carrier FDMA Ensuring Reliable Operation and Performance in Converged IP Networks Testing Storage Area Networks and Devices at 8.5-Gb/s Fibre Channel Rates Choosing an Appropriate Calibration Method for Vector Network Analysis Making Traceable EVM Measurements with Digital Oscilloscopes Exploring Terahertz Measurement, Imaging and Spectroscopy: The Electromagnetic Spectrum’s Final Frontier Interpreting Quoted Specifications when Selecting Digitizers

Agilent Measurement Journal - Issue 4 - 2008

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