Using one or more high-impedance voltage probes (HIP), this feature allows you to perform calibrated in-circuit voltage 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.

1. HIP @ ICE
using high-impedance probes
for in-circuit voltage
time-domain measurements
© NMDG
2/2012

2. Summary
Goal: accurate in-circuit measurement of time-domain voltage using one or
more high-impedance probes (HIP) within a large-signal network analysis
context @ locations normally unreachable using a vector network analyzer
Supported:
● Multiple probes
● Probing on PCB
● Probing on wafer
What are the voltage waveforms in-between the components?
How to measure these accurately? Apply proper calibration techniques
How to minimize their disturbance? Use high-impedance probes
© NMDG 2012 2

3. Outline
(*)
● Calibrated measurement using “home-made” HIP and ZVxPlus
● Measurement setup
● Measurement results
● Impact of high-impedance probing
● Calibration
● Calibrated measurement using commercial Kelvin probe and real-time scope
● Measurement setup
● Measurement results
● Impact of high-impedance probing
● Calibration
(*)
R&S ZVA24 VNA with nonlinear extensions to allow time-domain measurements
© NMDG 2012 3

4. Measurement using calibrated HIP in practice (I)
Sanity check measuring the output voltage of an E-pHEMT FET
-5 dBm input @ 250 MHz, Vgs = 0.4 V, Vds = 4 V
2nd probe
probe
synchronizer P3 P1 P4 P2
source probes 50Ω
termination
2nd calibrated HIP probe allows to measure the input voltage
© NMDG 2012 4

5. Measurement using calibrated HIP in practice (II)
v2(t)
excellent agreement between output voltage (red)
measured using the TRL-calibrated coupler-based
two-port network analyzer and the voltage (green)
measured by the calibrated high-impedance probe
v2(f)
corresponding excellent agreement
of amplitude and phase in the
frequency domain
upper: coupler-based amp & phase
lower: calibrated HIP amp & phase
© NMDG 2012 5

6. Measurement using calibrated HIP in practice (III)
“a global ICE perspective”
© NMDG 2012 6

7. Impact of high-impedance probing(*)
The impedance of the probe is measured during calibration
↓
The impact of the high-impedance probe can be taken into account
| ZHIP |
f (GHz)
2600 0.5 1 1.5 2
2400 10
2200 20
2000
30
1800
40
1600
1400 50
f (GHz)
0.5 1 1.5 2 60
ZHIP (deg)
Estimated impedance of “home-made” (2k4) HIP
(*)
in fact the combination of the probe, cable and receiver input
© NMDG 2012 7

8. Including impact of high-impedance probe during simulation
Probe
i2
v2
v probe
i1
v1
including the load effect of the
probe in the simulation to
compare measurements with
Figure and schematic courtesy of AWR
simulations
© NMDG 2012 8

9. Calibration process
● Step 1: perform a “standard” one-port or two-port 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 high-
impedance probe
● Step 3: use the calibrated high-impedance probe to measure the time-
domain voltage in-circuit
© NMDG 2012 9

10. Calibration of high-impedance probe (step 2)
Different options are possible, such as :
● Starting from an absolute TRL-based two-port calibration :
● Connect the HIP to the open of the TRL calibration kit (fig. 1)
● Connect the HIP to the thru of the TRL calibration kit (fig. 2)
● Starting from an absolute on-wafer one-port calibration :
● Connect the HIP to the open of the on-wafer calibration kit
● Starting from an absolute coaxial one-port (or two-port) calibration :
● Connect the HIP to the open on a microstrip or coplanar waveguide PCB
provided by NMDG
● De-embedding information provided with PCB allows to move the absolute
calibration from the coaxial plane to the open on the PCB
fig. 1 fig. 2
© NMDG 2012 10

11. High-impedance probe calibration in practice (step 2)
Connecting the “home-made” (2k4) HIP
to the thru of the TRL calibration kit
© NMDG 2012 11

12. HIP and real-time scope : ESD (TLP) @ OnSemi
Using a calibrated Kelvin probe as part of
a transmission line pulse (TLP) system to
re-construct dynamic voltage waveforms
on low-impedance devices subjected to
high currents with a very significant
improvement in the signal-to-noise ratio
Comparing reconstructed voltage waveforms at the DUT, measured on a 7.3V
Zener diode, subjected to a 200V TLP pulse. Blue : reconstructed using data
from the directional couplers. Red : corrected data from Kelvin-probe.
Photos and figure courtesy of Renaud Gillon (OnSemi, Oudenaarde, Belgium)
© NMDG 2012 12

13. TLP measurement setup
Tek scope
DP070404
x3m cable3
200 V, 25 ns pulse
0.6 ns rise time Kelvin
cable1 cable2 probe
Werlatone vD
charge line C6493 30 dB
coupler 7.3 V Zener diode
Kelvin probe
http://www.ggb.com/10.html
© NMDG 2012 13

14. Combined impact of Kelvin probe(*), cable3 and scope
transfer function impedance
|TF| (dB) x3m / vD |Z| (Ω)
freq 2k5 (nominal)
2500
0.2 0.4 0.6 0.8 1 (GHz)
34
50:1 (nominal) 2250
2000 resonance
35
effect
1750
36 1500
1250
37 1000 freq
0.2 0.4 0.6 0.8 1 (GHz)
TF (deg) Z (deg)
4 freq
0.2 0.4 0.6 0.8 1 (GHz)
2 10
freq
20
0.2 0.4 0.6 0.8 1 (GHz)
2 30
4 40
6 50
8 60
10 excl. delay of 8.3 ns
(*)
GGB – Model 10 - 2k5
© NMDG 2012 14

15. Primary calibration of TLP system
scope
x1m x2m
vD & iD
cable1 cable2
● open
source known ● short
● match
scope DUT
● power meter
x1m x2m ● pulse gen
vD & iD
cable1 cable2
50Ω known source
termination active
DUT
in case of on-wafer the absolute calibration is performed at an “Auxiliary” coaxial calibration plane
© NMDG 2012 15

16. Additional calibration of TLP system
scope
x3m cable3
Kelvin
probe
cable1 cable2 vD
source known ● open
DUT
● Compare x3m to calibrated coupler-based vD while measuring an open
Transfer function: TF = 1 / e33 = x3m / vD
● Measure impedance of Kelvin probe during calibration (using i )
D
● Allows to take effect of finite impedance into account during simulation
© NMDG 2012 16

17. Acknowledgements and References
● NMDG wants to thank Rohde & Schwarz and OnSemi for their support
● "A new time domain waveform measurement setup to investigate internal
node voltages in MMICs",
T. Reveyrand, A. Mallet, F. Gizard, L. Lapierre, J.M. Nébus, M. Vanden Bossche
Microwave Technology and Technique Workshop, ESTEC, Noordwijk , May 2004
● "Calibrated Waveform Measurement With High-Impedance Probes",
Pavel Kabos, Howard Charles Reader, Uwe Arz and Dylan F. Williams
IEEE Transactions on Microwave Theory and Techniques,
Vol. 51, No. 2, pp. 530 - 535, February 2003
● "Multiport Investigation of the Coupling of High-Impedance Probes",
P. Kabos, U. Arz and D. F. Williams
IEEE Microwave and Wireless Components Letters,
Vol. 14, No. 11, pp. 510 - 512, November 2004
© NMDG 2012 17

18. Contact info
Want to try this capability?
Contact us
at
info@nmdg.be
© NMDG 2012 18