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Using contactless probing techniques, this feature allows you to perform calibrated in-circuit voltage and current time-domain measurements under large-signal conditions, on printed-circuit boards (PCB) or on wafer, at locations which are normally unreachable using standard VNA techniques.
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Contactless loop probes @ ICE
using loop probes
for in-circuit voltage and currenttime-domain and impedance
measurements
6/2012
© NMDG
© NMDG 2012 2
Summary
Goal: accurate in-circuit measurement of time-domain voltage and current and impedance using one or more loop probes within a large-signal network analysis context at locations normally unreachable using a vector network analyzer.
Supported: Multiple probes Probing on PCB
What are the voltage and current waveforms in-between the components?
How to measure these accurately? Apply proper calibration techniquesHow to minimize their disturbance? Use loop probes
© NMDG 2012 3
Measurement using calibrated loop probe on thru
source
pulse gen
50Ωtermination
P1 P2
THRU PCB
P4synchronizer P3
cal planeP1 P2
The loop probe which was used to perform the measurements was kindly provided by Rosenberger HF-Technik
© NMDG 2012 4
Pulse measurement in 50 Ohm
measurement of pulse applied @ 700 MHz to THRUvia “Source In” @ P2 while load connected to “Source In” @ P1
measurement@ primary cal P1
measurementusing probe @ P4
measurement700 MHz .. 4.9 GHz
© NMDG 2012 5
1 2 3 4 5
29
28
27
Pulse @ thru : quantify voltage difference @ 700 MHz .. 4.9 GHz
0.5 1 1.5 2 2.5
0.25
0.2
0.15
0.1
0.05
0.05
1 2 3 4 5
0.1
0.05
0.05
0.1
1 2 3 4 5
1
0.75
0.5
0.25
0.25
0.5
0.75
1
v1(t), v4(t)V
f (GHz)
dBV
f (GHz)
f (GHz)
dB
deg
t (ns)
v1(f), v4(f)
dBV(v1(f)) - dBV(v4(f))
phase(v1(f)) - phase(v4(f))
excellent agreement between voltage measured using coupler @ P1and voltage measured by calibrated loop probe @ P4
© NMDG 2012 6
1 2 3 4 5
63.5
63
62.5
62
61.5
61
1 2 3 4 5
1
0.75
0.5
0.25
0.25
0.5
0.75
1
1 2 3 4 5
0.1
0.05
0.05
0.1
0.5 1 1.5 2 2.51
1
2
3
4
5
Pulse @ thru : quantify current difference @ 700 MHz .. 4.9 GHzexcellent agreement between current measured using coupler @ P1
and current measured by calibrated loop probe @ P4
i1(t), i4(t)mA
f (GHz)
dBA
f (GHz)
f (GHz)
dB
t (ns)
i1(f), i4(f)
dBA(i1(f)) - dBA(i4(f))
phase(i1(f)) - phase(i4(f))
deg
© NMDG 2012 7
Measurement using calibrated loop probe on FET
source 50Ωtermination
P1 P2
DUT PCB
P4synchronizer P3
cal planeP2
cal planeP1
The loop probe which was used to perform the measurements was kindly provided by Rosenberger HF-Technik
© NMDG 2012 8
E-pHEMT FET pinch-off measurement in 50 Ohm
measurement@ primary cal P2
measurementusing probe @ P4
measurement250 MHz .. 2 GHz
© NMDG 2012 9
0.5 1 1.5 2
2
1
1
2
0.5 1 1.5 2
1
0.5
0.5
1
0.5 1 1.5 2
40
30
20
10
10
1 2 3 4
3
2
1
1
2
3
E-pHEMT : quantify voltage difference @ 250 MHz .. 2 GHz
v2(t), v4(t)V
f (GHz)
dBV
f (GHz)
f (GHz)
dB
deg
t (ns)
v2(f), v4(f)
dBV(v2(f)) - dBV(v4(f))
phase(v2(f)) - phase(v4(f))
after elimination of 56.7 ps delay based on b2(f) and b4(f)
very good agreement between voltage measured using coupler @ P2and voltage measured by calibrated loop probe @ P4
© NMDG 2012 10
0.5 1 1.5 2
1
0.5
0.5
1
0.5 1 1.5 2
1
2
3
4
5
0.5 1 1.5 2
70
60
50
40
30
1 2 3 4
40
20
20
40
60
E-pHEMT : quantify current difference @ 250 MHz .. 2 GHz
i2(t), i4(t)mA
f (GHz)
dBA
f (GHz)
f (GHz)
dB
deg
t (ns)
i2(f), i4(f)
dBA(i2(f)) - dBA(i4(f))
phase(i2(f)) - phase(i4(f))
after elimination of 56.7 ps delay based on b2(f) and b4(f)
very good agreement between current measured using coupler @ P2and current measured by calibrated loop probe @ P4
© NMDG 2012 11
Including impact of loop probe during simulationProbe
including the load effect ofthe probe in the simulationto compare measurementswith simulations
v1i1
i2v2
v probe
Figure and schematic courtesy of AWR
i probe
© NMDG 2012 12
Calibration process
Step 1: perform a “standard” two-port TRL-based VNA calibration, extended with power and phase calibration to measure time-domain information
Step 2: use the calibrated system resulting from step 1 to calibrate the loop probe by positioning it above the thru or middle of the line of the TRL calibration kit and applying different terminations to the two-port VNA
Step 3: use the calibrated loop probe to measure the time-domain voltage and current (hence impedance) in-circuit
© NMDG 2012 13
Acknowledgements and References
NMDG wants to thank Rohde & Schwarz, Rosenberger HF-Technik and Prof. Dr.-Ing. Bernd Geck of the Institut für Hochfrequenztechnik und Funksysteme of the Leibniz Universität Hannover for their support
“Contactless Scattering Parameter Measurements”, Thomas Zelder and Bernd Geck, IEEE Microwave and Wireless Components Letters, Vol. 21, No. 9, September 2011
“Contactless Loop Probe”, Patent US 20110267088A1
