Technical Note
Using the Agilent Physical Layer Test System (PLTS)
For Acquiring Time Domain Data
Using:
Final Inch® Test/Eval Kit, Differential Pair - No Grounds Configuration,
QTE-DP/QSE-DP, 5mm Stack Height
(P/N FIK-QxE-04-01)
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
TABLE OF CONTENTS
Introduction .......................................................................................................... 3
Conclusions.......................................................................................................... 3
Samtec QPairs® QTE-DP/QSE-DP Final Inch® Test and Evaluation Board ....... 4
Agilent PLTS ........................................................................................................ 5
Calibration........................................................................................................ 5
TDA IConnect....................................................................................................... 5
Time Domain Comparison.................................................................................... 6
Impedance ....................................................................................................... 6
Time Domain Transmission (TDT)................................................................... 7
Frequency Domain Comparison......................................................................... 10
Insertion Loss ................................................................................................ 10
Return Loss ................................................................................................... 11
Equipment List ................................................................................................... 12
Summary............................................................................................................ 12
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:ii
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
Introduction
Measured data on passive interconnects (cables, connectors) can be acquired in either
the time domain or frequency domain. In principle, data can be transformed into the
“other” domain using Fourier transforms. There are two commercial tools currently used
by Samtec:
•
TDA Systems IConnect TDR and VNA Software (TDA)
Acquires data in the time domain using a digitizing oscilloscope (Tektronix CSA
8000 with 80E04 sampling module) and can convert to the frequency domain
•
Agilent Physical Layer Test Systems version 2.500 (PLTS)
Acquires data in the frequency domain with a vector network analyzer (Agilent
E8364B PNA series network analyzer with N4421B S-parameter test set) and
can convert to the time domain
In this report, we compare data taken using TDA and transformed into the frequency
domain with data taken in the frequency domain. We will also compare data taken with
PLTS and transformed into the time domain with data taken in the time domain.
The Device Under Test (DUT) is a Samtec QTE-DP/QSE-DP QPairs® Final Inch® Test
and Evaluation Board.
Conclusions
Correlation in the time domain between the TDA data and the transformed PLTS data
was typically within 1 ohm which is within the accuracy of the measurement equipment.
Correlation in the frequency domain between the magnitude of the PLTS data and the
transformed TDA data was <0.5 dB for insertion loss and <2dB for return loss. The
phase correlation was generally better than 5 degrees except in regions where the
phase response had greater structure.
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:3
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
Samtec QPairs® QTE-DP/QSE-DP Final Inch® Test and Evaluation Board
The Samtec QPairs® QTE-DP/QSE-DP Final Inch® Test and Evaluation Board set
(test board) consists of precision SMA launches, controlled impedance stripline traces,
and the QTE-DP/QSE-DP high speed connectors (Figure 1). The test boards allow
access to 28 different connector pins and are suitable for single ended or differential
pair testing.
For this test data, only the J7-J9 pair was used and results are for differential excitation
unless noted otherwise. Typically, the test boards are used to empirically measure the
performance of a connector or to validate electrical models developed by Samtec. For
further information refer to the following Samtec webpage:
http://www.samtec.com/signal_integrity/final_inch/test_boards.asp
Figure 1: Final Inch® QPairs® Test and Evaluation Board kit (top), QTE-DP/QSE-DP test boards
(bottom)
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:4
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
Agilent PLTS
The Agilent PLTS is broadly classified as a 4 Port Vector Network Analyzer (VNA). It
has become popular in characterizing passive interconnect structures for high speed
digital applications. Connectors, coupled stripline traces, and cable assemblies can be
characterized with the PLTS. The bandwidth used for these measurements is from 10
MHz to 20 GHz.
Calibration
Calibration of the VNA using well defined standards can be complex, but it is critical to
achieve accurate measurements. For the data presented in this report, a Short, Open,
Load, Thru (SOLT) calibration was performed prior to performing any measurements.
The calibration was from 10 MHz to 20 GHz with a step frequency of 10 MHz. Precision
2.4mm cables and a 2.4mm-3.5mm adapter connect the VNA to the test boards. As
with any measurement, it is wise to validate the calibration by measuring a known
device and verifying that the magnitude and phase response are reasonable.
TDA IConnect
TDA IConnect was used to acquire the time domain waveform from the Tektronix CSA
8000 Oscilloscope. 80E04 sampling heads were used which have an output risetime of
approximately 30 ps (10%-90%). IConnect can compute insertion loss and return loss
provided a reference waveform is obtained. The reference waveform establishes the
reference plane and can account for imperfections in the fixturing. For the return loss
computations, an open calibration standard was used. This established the reference
plane for the return loss measurement at the SMA interface at the end of the test cable.
Differential loss measurements were performed by acquiring differential waveforms from
the oscilloscope and processed within TDA using the “compute S-parameter” feature.
For the insertion loss computations, a short (~.400”) SMA female-SMA female adapter
was used. Because this barrel was used, we would expect a phase off set of
approximately 50 ps or 200 degrees at 10 GHz compared to the PLTS data.
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:5
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
Time Domain Comparison
The Agilent PLTS software has several parameters which can be adjusted that can
affect the computed time domain response from the measured frequency domain data.
For the purpose of this report, a nominal time domain window was used. This feature is
found under the “Tools” menu and adjusts the windowing filter bandwidth.
Impedance
The Agilent PLTS software will export a CSV file for T11 which is the reflected voltage
from port 1. For the data shown in Figures 6.1.1, port 1 equates to J7. To compute the
impedance profile from the reflected voltage, we use the following equation:
1+ ρ 

Z = Z 0 
 1− ρ 
where ρ is the coefficient of reflection and Z0 is the reference impedance. This
calculation was included in the Excel spreadsheet used to process the data in Figure 2
and 3.
Impedance J7 QTE-DP/QSE-DP
75
Connector and footprint
70
SMA connector interface
Impedance (ohms)
65
60
55
50
45
J7 TDR
40
J7 PLTS Nominal TD window,
20 GHz
35
30
5.5E-09
5.0E-09
4.5E-09
4.0E-09
3.5E-09
3.0E-09
2.5E-09
2.0E-09
25
time (seconds)
Figure 2: Comparison of Single-Ended Impedance Profiles
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:6
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
Differential Impedance J7-J9 QTE-DP/QSE-DP
150
140
SMA connector interface
Impedance (ohms)
130
Connector and footprint
120
110
100
90
80
J7-J9 TDR
70
J7-J9 w/ PLTS Nominal TD
window, 20GHz BW
60
5.5E-09
5.0E-09
4.5E-09
4.0E-09
3.5E-09
3.0E-09
2.5E-09
50
time (seconds)
Figure 3: Comparison of Differential Impedance Profiles
The correlation between the time domain data taken with TDA closely matches the frequency
domain data taken with the PLTS system which was transformed into the time domain.
Time Domain Transmission (TDT)
The PLTS software exports a CSV file of T21 (TDT) which can be read into Excel. To
get the time scales to line up, an offset time needs to be added to the PLTS time vector.
The PLTS software exports the TDT voltage with an amplitude of 1 volt. To get the
single-ended voltage scales to line up, the voltage vector was multiplied by a factor of
0.25 to mimic the 250 mVp step voltage used by TDA. This voltage vector factor is 0.5
for the differential data in Figure 5
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:7
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
Output Voltage J7 QTE-DP/QSE-DP
0.3
Voltage (volts)
0.25
0.2
0.15
Measured with TDA
0.1
Computed with PLTS, Nominal TD
window, 20 GHz
0.05
7.50E-09
6.50E-09
5.50E-09
4.50E-09
3.50E-09
2.50E-09
1.50E-09
0
time
Figure 4: Comparison of Single-Ended TDT Voltages
Output Voltage J7-J9 QTE-DP/QSE-DP
0.6
Voltage (volts)
0.5
0.4
0.3
0.2
Computed with PLTS, Nominal TD
window, 20 GHz
0.1
Measured with TDA
5.00E-09
4.50E-09
4.00E-09
3.50E-09
3.00E-09
2.50E-09
2.00E-09
1.50E-09
1.00E-09
0
time
Figure 5 Comparison of Differential TDT Voltages
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:8
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
The correlation between the PLTS and TDA appears to be moderate based on the
Figures 4 and 5. The differences were studied and are fundamental in nature. The
PLTS TDT does not include the effect of instrumentation cable, whereas the TDA TDT
includes the degradation associated with the lossy instrumentation cables. Improved
correlation was achieved when the instrumentation cables were shortened from 1 meter
to 6 inches.
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:9
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
Frequency Domain Comparison
Since TDA has the ability to transform data from the time domain into the frequency
domain, we can also make frequency domain comparisons.
Insertion Loss
As described in Section 5, a phase offset is introduced to the TDA data due to the use
of a SMA female-SMA female barrel in the reference measurement. The phase of this
adapter was measured to be 48 pS. This electrical length was subtracted from the TDA
data to get the phase correlation shown in Figures 6 and 7.
SE Insertion Loss - Phase
SE Insertion Loss - Magnitude
200
0
150
Phase (degrees)
Insertion Loss (dB)
-10
-20
-30
-40
PLTS - J7
-50
TDA IConnect - J7
-60
100
50
PLTS - J7
TDA IConnect - J7
0
-50
-100
-150
-200
-70
0
2
4
6
8
10
12
14
16
18
0
20
2
4
6
8
10
Freq (GHz)
Freq (GHz)
Figure6: Single-Ended Insertion Loss – Magnitude (left), Phase (right)
Differential Insertion Loss - Phase
Differential Insertion Loss - Magnitude
180
0
135
-10
90
Phase (degrees)
Insertion Loss (dB)
10
-20
-30
-40
-50
-60
PLTS - J7-J9
TDA IConnect - J7-J9
-70
45
0
PLTS - J7-J9
-45
TDA IConnect - J7-J9
-90
-135
-180
-80
0
2
4
6
8
10
12
14
16
18
20
0
2
4
6
8
10
Freq (GHz)
Freq (GHz)
Figure 7: Differential Insertion Loss – Magnitude (left), Phase (right)
Overall, the correlation between PLTS and TDA is quite good for the single-ended and
differential insertion loss. As expected, the PLTS dynamic range is greater than that
achieved with TDA.
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:10
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
Return Loss
The return loss measurements used an open circuit as a reference, so it does not have
the phase offset associated with the insertion loss measurements. Generally, the
correlation between the two sets of data is quite good with a maximum magnitude
difference of approximately 2 dB as shown in Figures 8 (left) and 9 (left). The
correlation between the phase data sets is also quite good as shown in Figures 8 (right)
and Figure 9 (right). Where the phase response has a complex response, the
correlation is not as good as shown in Figure 10.
SE Return Loss - Phase
SE Return Loss - Magnitude
180
0
135
Phase (degrees)
Return Loss (dB)
-10
-20
-30
-40
PLTS - J7
TDA IConnect - J7
-50
90
45
PLTS - J7
TDA IConnect - J7
0
-45
-90
-135
-180
-60
0
2
4
6
8
10
12
14
16
18
0
20
2
4
6
8
10
Freq (GHz)
Freq (GHz)
Figure 8: Single-Ended Return Loss – Magnitude (left), Phase (right)
Differential Return Loss - Phase
Differential Return Loss - Magnitude
180
0
-5
135
90
Phase (degrees)
Return Loss (dB)
-10
-15
-20
-25
-30
-35
PLTS - J7-J9
TDA IConnect - J7-J9
-40
45
0
PLTS - J7
TDA IConnect - J7
-45
-90
-135
-45
-50
-180
0
2
4
6
8
10
12
14
16
18
20
0
2
Freq (GHz)
4
6
8
10
Freq (GHz)
Figure 9: Differential Return Loss – Magnitude (left), Phase (right)
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:11
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved
Technical Note
Series: Final Inch® Test Kit, Differential – No Grounds Configuration, QxE-DP, 5mm Stack Height
Description: Using the Agilent PLTS For Acquiring Time Domain Data
SE Return Loss - Phase
Differential Return Loss - Phase
180
180
135
PLTS - J7
TDA IConnect - J7
90
Phase (degrees)
Phase (degrees)
135
45
0
-45
-90
-135
90
45
0
-45
PLTS - J7-J9
TDA IConnect - J7-J9
-90
-135
-180
-180
0
0.5
1
1.5
2
6
Freq (GHz)
6.5
7
7.5
8
Freq (GHz)
Figure 10: Expanded Phase Plots, Single-Ended Return Loss (left), Differential Return Loss (right)
Equipment List
Equipment List
Agilent Physical Layer Test System (PLTS)
Agilent Technologies E8364B 10 MHz - 50 GHz PNA Series Network Analyzer
Agilent Technologies N4421B 10 MHz - 50 GHz S-Parameter Test Set
Agilent Physical Layer Test System Version 2.500 (Control Software)
IConnect and MeasureXtractor (TDA)
Tektronix CSA 8000 Communication Signal Analyzer
Tektronix 80E04 Sampling Head
Time Domain Analysis Systems Inc., IConnect and MeasureXtractor (TDA) Version 3.5.0
Summary
In this report, we demonstrated that data taken in the frequency domain and postprocessed using PLTS has very reasonable correlation with data taken in the time
domain. We also showed that data taken in the time domain and post processed into
the frequency domain using TDA has very reasonable correlation with data taken in the
frequency domain. Correlation of the phase response extracted from TDA has not been
widely published which makes this report unique. Also, it was noted that TDT voltage
waveforms between PLTS and TDA are fundamentally different in that PLTS deembeds the influence of the test cables whereas TDA does not have an obvious method
for doing so.
Samtec Inc.
520 Park East Blvd.
New Albany IN 47151-1147 USA
©Samtec, Inc. 2005
WWW.SAMTEC.COM
1-800-SAMTEC-9 (US & Canada)
SIG@samtec.com
Page:12
Phone: 812-944-6733
Fax: 812-948-5047
Report Revision: 1/12/2006
All Rights Reserved