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Whitepapers from Keysight Technologies

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Accelerate Electromagnetic Interference Testing Using Real-Time Scan Measurement

This application note details Keysight’s Real-Time Scan (RTSC) measurement feature within the N9048B PXE EMI test receiver. The paper addresses limitations of traditional EMC testing methods – specifically gaps in data acquisition due to preselector filter switching in Time Domain Scans – which hinder accurate detection and troubleshooting of intermittent or fast transient signals. RTSC utilizes a 350 MHz FFT bandwidth for gapless signal capture, simultaneously displaying frequency, time, and spectrogram information with up to three EMI detectors. Results demonstrate that RTSC enables faster EMC debugging, allows users to analyze historical data from up to 12,000 time slices, and provides improved visualization of both broadband and narrowband signals compared to conventional methods for compliance testing against standards like CISPR, FCC, and others.

EMI Receivers
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Becoming Familiar with your Standard Oscilloscope Probe

This Keysight application note details important considerations when using oscilloscope probes, specifically focusing on high-impedance passive probes commonly paired with oscilloscopes ≤1 GHz. It explains how a standard 10:1 probe works—utilizing a 9 MΩ tip resistance and 1 MΩ input impedance to achieve attenuation—and the importance of proper compensation via an adjustable capacitor to match oscilloscope input capacitance. The paper also explores dual-attenuation ratio (1:1/10:1) probes, like the Keysight N2140A/N2142A, demonstrating that while 1:1 mode reduces noise (showing a nearly 50% reduction in measured power supply ripple), it significantly limits bandwidth to ~25 MHz. Finally, it covers probe loading effects—resistive, capacitive and inductive—and their impact on measurement accuracy, emphasizing that capacitive reactance becomes dominant at higher frequencies and can cause ringing due to LC resonance.

Oscilloscopes
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Boost EMC Test Throughput with Accelerated Time Domain Scan

This application note details Keysight’s Time Domain Scan (TDS) and Accelerated TDS capabilities implemented in the N9048B PXE EMI receiver for faster EMC testing. Conventional frequency domain scans dwell at each frequency step, whereas TDS uses Fast Fourier Transforms (FFTs) with high overlap (>90%) across wider acquisition bandwidths (1-350 MHz) to simultaneously capture emissions data – significantly reducing scan time while maintaining CISPR 16-1-1 and MIL-STD-461 compliance. Accelerated TDS further improves throughput, achieving scans in seconds that previously took hours. A CISPR Band C/D quasi-peak test, traditionally taking nine hours with a stepped scan, can be completed in approximately six seconds using Accelerated TDS on the N9048B receiver.

EMI Receivers
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EMC Pre-Compliance Fundamentals

This whitepaper details the importance of Electromagnetic Compatibility (EMC) pre-compliance testing during electronic product development. It explains how conducting internal EMI tests—both radiated and conducted emissions/immunity—can significantly reduce costs and delays associated with formal compliance certification against standards like CISPR, FCC, and EN series. The paper outlines four primary EMC test types, emphasizing that approximately 90% of testing should occur during prototyping and pilot runs rather than solely at the final compliance stage. Keysight Technologies’ equipment, including the N9010B/N9020B signal analyzers, N6141EM0E X-Series Measurement Application, and N9311X close-field probe set are presented as solutions for performing pre-compliance tests.

EMC Pre Compliance
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EMI Compliance Test vs. EMI Pre-Compliance Test

This whitepaper discusses the benefits of EMI pre-compliance testing versus full compliance testing for electronic devices. It highlights that while compliance tests (necessary for certifications like CE, FCC, and UL) are performed late in the development cycle and can be costly to fix, approximately 90% of EMC troubleshooting occurs during prototyping. Pre-compliance tests utilize tools like signal analyzers (Keysight N9010B EXA, N9020B MXA), often with near-field probes (N9311X-100) and software like the N6141C EMI Measurement Application, to identify emission sources early. While a dedicated EMI receiver is required for full compliance adhering to standards such as CISPR 16-1-1, a signal analyzer with appropriate detectors and bandwidth can effectively perform pre-compliance testing at a lower cost.

EMI/EMC IntroductionEMC Pre Compliance
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EMI Troubleshooting: The Need for Close Field Probes

This Keysight Technologies white paper addresses the practical challenges of electromagnetic interference (EMI) troubleshooting and explains how close field probes provide an efficient, targeted solution. The document centers on the Keysight N9311X-100 close field probe set, a four-probe system covering 30 MHz to 3 GHz, designed to help engineers quickly locate and diagnose EMI emissions at the component and circuit-board level before full compliance testing. Each probe in the set serves a distinct purpose: the largest (25 mm diameter) offers maximum sensitivity for measurements up to 10 cm from a unit; a medium probe (10 mm) balances sensitivity and resolution for measurements up to 3 cm; a fine-tip probe (2 mm) targets magnetic fields emitting vertically from flat PCB surfaces and can reach obstructed areas; and a specialized probe (5 mm) detects surface and circular magnetic fields on conductive paths, connectors, and cables. When combined with EMI pre-compliance software and a signal analyzer, the probe set delivers sensitivity, resolution, and spatial diversity that make it a cost-effective tool for isolating interference sources early in the design cycle.

Near Field ProbesEMC Pre Compliance
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Electromagnetic Interference Testing Using Real-Time Scan Measurement

This application note details the use of Keysight’s N9048B PXE EMI test receiver with its new Real-Time Scan (RTSC) measurement feature for improved EMC testing. Traditional time-domain scans suffer from gaps between frequency acquisitions due to preselector filter switching, potentially missing intermittent signals. RTSC overcomes this by utilizing a 350 MHz FFT bandwidth for gapless signal capture and simultaneous display of frequency, time, and spectrogram data with up to three detectors. This enables faster troubleshooting, historical data access via the SCPI protocol (up to 12,000 time slices), and features like a built-in strip chart & intuitive multi-domain visualization for both broadband and narrowband signals – improving debugging efficiency in increasingly complex wireless environments driven by 5G, IoT, and autonomous vehicles.

EMI Receivers
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Enhance EMC Testing with Digital IF

This Keysight application note details the advantages of Digital IF (Intermediate Frequency) architecture in EMC testing equipment compared to traditional analog IF designs. Analog IF systems suffer from amplitude errors due to RBW switching uncertainty (up to ±0.5 dB), gain inaccuracies (±1dB), and log amplifier non-linearity (up to ±0.85dB). Digital IF significantly reduces these uncertainties—RBW switching is <0.05dB, gain steps have near 0dB error, and display scale fidelity improves to ±0.15dB – leading to more accurate measurements as required by standards like CISPR 16-1-1. This improved accuracy translates to increased throughput during EMC testing (by reducing the need for manual peak signal adjustments) and lessened reliance on highly experienced operators while maintaining compliance with industry standards.

EMI ReceiversSpectrum Analyzer
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Equivalent Time Sampling Oscilloscope vs. Real-Time Oscilloscope

This application note from Keysight Technologies differentiates between real-time and equivalent time sampling oscilloscopes. Real-time scopes function as fast ADCs, capturing entire waveforms with sample rates up to 80 GSa/s (bandwidth extending to 63 GHz) triggered asynchronously to the input signal. Equivalent time sampling scopes, conversely, sample only once per trigger cycle with a rearm time of approximately 25 μs and require synchronous triggering; they achieve bandwidth exceeding 80GHz. The paper details acquisition methodologies for both types – real-time capture vs. incremental delay sampling - and their respective applications including bit stream analysis & eye diagram creation. Advantages highlighted include the real-time scope's ability to capture single-shot events, versus the equivalent time scope’s wider bandwidth and lower jitter.

Oscilloscopes
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Essential Capabilities of EMI Receivers

This Keysight Technologies application note details essential capabilities of EMI receivers for compliance testing with CISPR 16-1-1 and MIL-STD-461 standards. It outlines the required detectors (Peak, Quasi-peak, Average) and reference bandwidths – ranging from 200Hz to 1MHz depending on frequency bands A through E (9kHz-18GHz) for CISPR, and specific RBWs from 10Hz to 1 MHz for MIL-STD-461. Crucially, it goes beyond mandatory features, highlighting the value of limit lines with editing capabilities, correction factors for transducers, signal lists storing up to 2000 results, tools for maximizing signal capture (including linked meters and spectrum analysis), time domain scanning, and diagnostic tools like amplitude distribution function (APD) and a spectrogram. The MXE EMI receiver is presented as an example of a platform incorporating these features.

EMI Receivers
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Evaluating EMC Components with DC Bias Superimposed

This Keysight Technologies application note details a method for accurately evaluating EMC components – specifically ferrite beads – under realistic operating conditions. It addresses the increasing complexity of EMC requirements driven by faster data rates, lower voltages, and miniaturization of electronics. The paper highlights the importance of measuring impedance characteristics while applying DC bias to account for inductance saturation, demonstrated using Keysight's E5071C ENA network analyzer in conjunction with a DC power source and electronic load. Two measurement methods are discussed: reflection (one-port) and shunt/series (two-port), with preference given to S21 measurements due to lower noise floors. The note includes details on a sample VBA program for automating the process using the E5071C, the E3633A/E3634A power source, and the 3300A/E3301A electronic load.

Vector Network AnalyzersEMC components
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Evaluating Oscilloscope Bandwidths for Your Application

This application note details how to select an oscilloscope bandwidth appropriate for both digital and analog applications. It contrasts Gaussian and maximally-flat frequency responses, noting that the former allows faster rise times while the latter provides more accurate in-band signal measurement. For digital signals, the paper advocates determining the “knee” frequency (fknee) of fast edges – calculated as 0.5/rise time (10-90%) or 0.4/rise time (20-80%) – and multiplying it by a factor between 1.0 (for 20% accuracy) to 1.9 (for 3% accuracy) to determine required bandwidth. Using a 100MHz clock signal with 500ps rise times as an example, the paper demonstrates how scopes of differing bandwidths (100 MHz, 500 MHz, 1 GHz, and 2 GHz) impact measurement accuracy.

Oscilloscopes
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