Agilent Measurement Journal - Issue 4 - 2008 - (Page 15)

Deﬁning the optimum test solution A swept spectrum analyzer with fast auto-tuning as well as vector signal analysis (VSA) software with spectrogram displays can easily analyze the power characteristics of complex RFID transmissions. Such an analyzer can recognize the modulation of a transient RFID signal and obtain the requested measurements of frequency, bandwidth and power (typically power versus time). One feature of particular beneﬁt, particularly in the R&D phase, is the ability to make triggered, gap-free recordings of the signals for later analysis. This combination of capabilities provides the best solution for measurements of spectrally inefﬁcient RFID modulations and their unique decoding needs. Built-in demodulation and decoding capabilities also enable measurements of transient signals by triggering on speciﬁc spectral events in a timely manner. With three-dimensional color spectrogram displays, the user can monitor the evolution of a transient signal in real time and as a trend. The automatic setting of thresholds and markers on a display trace also allows the numerical analysis of rapidly changing signals. For detailed analysis, a multi-trace display conﬁguration with “average,” “maximum hold” and “minimum hold” detectors and markers enables the identiﬁcation of signiﬁcant transient changes within speciﬁc frequency segments. Reader/tag analysis When integrating an RFID communications system, digital, baseband, IF and RF signals are present. The close proximity of the components often leads to crosstalk and the presence of unwanted signals in the output. By calculating the fast Fourier transform (FFT) of an errorvector magnitude (EVM)-versus-time trace, any deterministic components in the error trace will show up as spectra in the error-vector spectrum. The result, for example, might show a spur below the center frequency. Examining the spur’s absolute frequency and its frequency offset from the carrier will often reveal the interference source. Time-domain analysis Analysis of burst and CW signals in the time domain provides additional insights into RFID performance. Any RFID interrogator signal can be recorded in the time domain and displayed in a log-magnitude format. This is an easy way to see the power envelope of the signal. If multiple display markers are available, they can be used to measure power or voltage at an instant in time. The time axis can be conﬁgured as relative to the beginning of the acquisition record or at the trigger point. Standards compliance Examples include EPCglobal Class1-Gen2 and other ISO 18000 standards for ultra high frequency (UHF) operation, plus others such as ISO 18062 and ISO 14443 that operate in the lower high frequency (HF) range.1 Measurements typically allow manual setting of demodulation format, line coding and bit-rate control. In all cases, a ten-step process can help ensure successful digital demodulation of RFID signals. This process is based on the capabilities of the Agilent 89600 VSA software. Surveying RFID test requirements Around the world, various government agencies regulate the testing of RFID signals in terms of power, bandwidth and frequency. These regulations are intended to protect users and other devices from harmful interference, ensuring that transmitters do not cross-talk or compete with neighboring RF channels. As a result, numerous standard parameters must be tested during R&D and manufacturing processes. The three most important parameters are reader/tag analysis, time-domain analysis and standards compliance. 1. EPC is Electronic Product Code and Class1-Gen2 refers to class 1, generation 2 of the EPCglobal standard. Agilent Measurement Journal 15

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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