Typical EMI Probe S21 5 * EMI Hx 2 mm: up to 10 GHz
What Are the Specs? 6 Log freq: Low freq with 20 dB/dec slope * EMI Hx 2 mm
What Are the Specs? 7 High freq: How high the probe measures? * EMI Hx 2 mm
What Are the Specs? 8 Unwanted field: Decoupling of unwanted components * EMI Hx 2 mm
What Are the Specs? 9 Low freq: How low the probe measures in a “practical” setup? 20 dB/dec slope 60 dB dynamic range 4 MHz
High Freq Probe 10 * EMI Hx 1 mm L: up to 20 GHz
Probe Factor 11 * EMI Hx 2 mm Probe factor: Provide probe factor SmartScan imports probe factor SmartScan measures and calculates system factor
Other Methods of Data Presentation How other people characterize their probes? How the characterization data is presented? Is their data presentation fair? 12
Example* of 10 kHz (?) to 6 GHz Probe Data Presentation 13 Let’s analyze the data! Extract * Aprel: http://media.wix.com/ugd/36d46a_46d2902bfdd24c25b401582e6a488370.pdfhttp://media.wix.com/ugd/36d46a_46d2902bfdd24c25b401582e6a488370.pdf
Is Freq Scale OK? 14 Why the freq axis of extracted data don’t match?! Let’s see! Let’s analyze the data!
Is Freq Scale OK? 15 0.99999 GHz1.3 GHz 1.1 GHz Why all ticks are equal?! Well, not a big deal. Maybe just a typo!
Lower Frequencies 16 Why all ticks are equal?! Well, not a big deal. Maybe just a typo! What happened to lower freqs?! Is it extrapolated or really measured? What is the measurement instrument setup (IF BW, span, no. of points, etc.) to measure down to 10 kHz? Is it a “practical” setup?
Plot It Differently 17 What if we plot it in a different way (log freq)? The probe is NOT purely inductive at lower freqs (as claimed). Is it probe issue? Or, measurement issue? Or, simply not extrapolated the right way? Note: Simple extrapolation (even if it is done the right way) does NOT mean probe can measure down to that freq!
How about 10 kHz to 20 GHz (?) Probe? 18 Extract Let’s analyze the data!
Flat Response (?) 19 Let’s analyze the data! The data is from -30 dB to -60 dB. Why the scale is from 0 to -180 dB?! Well, it looks better* this way! :-) *“flat response across the frequency range”
Plot It Differently 20 What if we plot it in a different way (tight scale)?
Plot It Differently 21 What if we plot it in a different way (log freq)? The lower freqs seems to be fine for this prob. The deviation might be just data extraction error.
Higher Frequencies 22 How about the higher freqs? There is about 20 dB notch @ 13 GHz! A deep notch is usually a BIG red flag for “unwanted field” coupling!
Higher Frequencies 23 The question is: How to make sure this probe measures the “desired field” up to 20 GHz (as claimed)? The “unwanted field” decoupling data of probe need to be provided. This probe is suspected to work <10 GHz, unless the rejection info is available!
10 kHz to 40 GHz Probe 24 Let’s analyze the data! Extract
Flat Response (?) 25 Let’s analyze the data! Same question: The data is from -35 dB to -55 dB. Why the scale is from 0 to -120 dB?!
Plot It Differently Single Probe Solution (?) 26 What if we plot it in a different way (tight scale and log freq)? This info is NOT sufficient to evaluate the probe up to 40 GHz! The “unwanted field” decoupling data of probe need to be provided. What does happen to lower freqs? Does this probe have sufficient sensitivity to measure down to 10 kHz?!
Another Example* of Data Presentation 27 * Detectus AB: http://www.detectus.se/products_nearfieldprobes.htmlhttp://www.detectus.se/products_nearfieldprobes.html Again, the data is from -30 dB to -60 dB. Why the scale is from 0 to -60 dB?! Without unwanted field data, there is no sufficient info to evaluate the probe. Log freq scale is required for low freq evaluation.
What to Look for in Probe Characterization Data? Unwanted field rejection data need to be provided to determine higher usable freq. Is lower usable freq achievable in a “practical” setup? Is the probe purely inductive/capacitive at lower freqs? Is the characterization structure (MSL, CPW, etc.) suitable for freq of interest? What is the measurement setup/condition? Is the scale proportional to data range? 28
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