Amber Precision Instruments

Whitepapers from Amber Precision Instruments

An Effective Method of Probe-calibration in Phase Resolved Near-field Scanning for EMI Application

This paper presents a time-domain broadband calibration method for E- and H-field probes used in phase-resolved near-field EMI scanning. A comb generator drives a 50Ω microstrip trace, creating known fields (simulated in CST) across 10 MHz–1 GHz in a single waveform capture. The probe factor — a complex, frequency-dependent ratio of field strength to oscilloscope voltage — is determined by referencing measured voltage to simulated fields, capturing the full probe-cable-amplifier chain in one shot. Validated against TEM cell calibration (difference under 1 dBc) and confirmed via scanning of a microstrip-copper patch test device, the method shows under 20% relative error in strong-field regions.

Near Field ScanningNear Field ProbesOscilloscopesCalibration Methods

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Broadband Phase Resolving Spectrum Analyzer Measurement for EMI Scanning Applications

Amber Precision Instruments

This conference paper presents the precursor work to the full Marathe et al. journal paper above. It introduces two hardware implementations for extracting phase from magnitude-only SA measurements between 5 and 12 GHz. Implementation I uses sum and difference measurements with two cable lengths and a 180° hybrid coupler; Implementation II replaces the expensive hybrid with three cable lengths for phase shifts. A variable attenuator with six 5 dB steps (30 dB range) ensures the reference and probe signals have comparable magnitudes for accurate phase retrieval. Phase is recovered via Nelder-Mead optimization within ±20° error, with each scan point requiring 18–24 SA sweeps. The method is practical for far-field prediction using Huygens' box methods, which are relatively insensitive to phase errors of this magnitude.

Spectrum Analyzer

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Characterization of Human Metal Model ESD Based on Radiated Susceptibility

Amber Precision Instruments

This paper investigates the radiated susceptibility of PCBs to Human Metal Model (HMM) ESD events per IEC 61000-4-2. Circuit and full-wave SPICE/CST simulation models of HMM, HBM, and TLP generators are developed and validated. The coupling mechanism between an HMM ESD generator and a 50Ω microstrip is compared with near-field TLP injection per ANSI/ESD SP14.5-2015, showing good waveform agreement. An empirical formula is derived to correlate HMM voltage settings with equivalent TLP voltage, accounting for probe factor, probe-to-signal distance, and near-field attenuation (~1/r^1.66 for TLP probes, ~1/R^1.25 for the ESD generator).

EMI / EMC SimulationEMC for PCB DesignElectrostatic Discharge (ESD)

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Near Field Probe for Detecting Resonances in EMC Application

Amber Precision Instruments

This paper proposes a novel near-field probe that integrates an electrically small metallic cone with a shielded magnetic loop to detect resonances in PCBs, cables, and structural elements. The E-field from the cone dominates coupling; S21 measurements between the two ports reveal resonant structures when S21 rises above the baseline. Validated in CST and HFSS and demonstrated on a ring microstrip test structure (resonance at ~240 MHz) and a computer motherboard (cable resonance at ~109 MHz), the probe integrates into automated scanning systems without requiring 90° rotation, enabling spatial mapping of resonance frequencies and Q-factors.

Near Field Probes

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Spectrum Analyzer Based Phase Measurement for Near-Field EMI Scanning

Amber Precision Instruments

This paper presents a fully automated, cost-effective spectrum analyzer method for phase-resolved near-field EMI scanning operating from 5–12 GHz. Using SP3T switches, phase-shift cables, and a variable attenuator, the system extracts phase from magnitude-only measurements via a Nelder-Mead optimization algorithm. Compared against VNA, oscilloscope, and CST full-wave simulation results over a 5 GHz resonant structure, the SA method achieves ±20° phase accuracy — comparable to the oscilloscope and near the VNA's ±10°. It outperforms the VNA in broadband and low-RBW scenarios, while only the oscilloscope handles transient signals.

Spectrum AnalyzerOscilloscopesVector Network Analyzers

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