US 11,536,793 B2

9

In an embodiment, calibrating cross-frequency phases of
large-signal network analyzer measurements includes
i vy vector network analyzer 205, calibration factor
234 from signal processor 228 by transfer of digital infor-
mation; and calibrating forward digitized signal 229, reverse
digitized signal 230, or reference digitized signal 232 based
on calibration factor 234 by applying calibration factors to
digitized measurements performed by vector network ana-
lyzer 205.

In an embodiment, calibrating cross-frequency phases of
large-signal network analyzer measurements includes apply-
ing, by vector network analyzer 205, calibration factor 234
from signal processor 228 to perform frequency-point-by-
frequency-point calibration of a scattering-parameter and
power by applying calibration factors to digitized measure-
ments performed by vector network analyzer 205. Accord-
ing to an embodiment, calibration signal 219 includes a
single tone sinusoid.

In an embodiment, calibrating cross-frequency phases of
large-signal network analyzer measurements includes pro-
ducing, by signal generator 201, single tone sinusoid at each
frequency to be measured by calibration receiver 204 and
vector network analyzer 205 by programming an arbitrary
waveform generator to create single tone sinusoid.

In an embodiment, calibrating cross-frequency phases of
large-signal network analyzer measurements includes mea-
suring, by calibration receiver 204, part of a cycle, one cycle,
or more than once cycle of single tone sinusoid by using the
samplers and other hardware in an oscilloscope.

In an embodiment, calibrating cross-frequency phases of
large-signal network analyzer measurements includes m
suring, by calibration receiver 204, multitone calibration
signal 219 by using the samplers and other hardware in an
oscilloscope.

In an embodiment, calibrating cross-frequency phases of
large-signal network analyzer measurements includes com-
paring, by signal processor 228, phases of the single tone
sinusoid measured by vector network analyzer 205 and
calibration receiver 204 by comparing these phases to those
of reference multitone signal 217, such that calibration
factor 234 includes a cross-frequency phase calibration of
vector network analyzer 205 to calibration receiver 204. It is
contemplated that reference multitone signal 217 from sig-
nal generator 201 includes a plurality of unknown, stable
tones, and reference multitone signal 217 is a phase refer-
ence for signal generator 201

The process for calibrating cross-frequency phases of
large-signal network analyzer measurements also can
include performing mismatch corrections based on measure-

ments performed by vector network analyzer 205, time-base 5

correction algorithms based on measurements of synchro-
nization signal 210 by oscilloscope.

Calibration apparatus 200 and processes disclosed herein
have numerous beneficial uses, including calibrated trace-

able measurements of long modulated signals performed on.
Ac

arbitrary frequency grids. Advantageously, calibration appa-
ratus 200 overcomes limitations of technical det of
conventional compositions such as electrical comb genera-
tors. Further, calibration apparatus 200 overcomes the prob-
lems with simultaneously attaining adequate power, broad
bandwidths and closely spaced tones in the frequency
domain.

Beneficially, calibration apparatus 200 and calibrating
cross-frequency phases of large-signal network analyzer
measurements is applicable to any frequency grid that can be
generated by an AWG. The phase lock of calibration appa-
ratus 200 can be implemented at high frequencies (e.g., 10

20

&

10

GHz), lowering phase noise. The AWG can provide power
at frequencies of interest, greatly increasing the signal-to-
noise ratio compared to conventional comb-based.
approaches and lifting restrictions on the upper frequency
limit and tone spacing. Calibration apparatus 200 can be
operated at the highest frequency that can measured by a
calibrated oscilloscope, e.g., about 110 GHz. Vector network
analyzer 205 can be calibrated with single-tone signals on an
arbitrary frequency grid for more than a cycle, making them
fast and easy to measure on the sampling oscilloscope, or
multitone signals, allowing for more frequency points to be
measured before uploading new signals into the AWG.
Calibration receiver 204, e.g., the sampling oscilloscope,
can be calibrated directly with a calibrated photodiode,
eliminating comb generators from the traceability path. It is
contemplated that calibration apparatus 200 can be directly
calibrated and operated on wafer to the highest frequency at
which electro-optic sampling can be used to provide the
phase calibration as calibration receiver 204 in place of the
oscilloscope, currently about 1 THz.

Calibration apparatus 200 and processes herein unexpect-
edly diverse applications to a broad range of signals with no
restriction on the frequency grid. Moreover, calibration
apparatus 200 provides excellent dynamic range and speed

5 during the calibration process due to the high power achiev-

able in each frequency tone in calibration signal 219 and the
ability to only generate tones needed in calibration signal
219.

The articles and processes herein are illustrated further by
the following Example, which non-limiting

EXAMPLE

Large-Signal-Network-Analyzer Phase Calibration on an
Arbitrary Grid.

‘A calibration apparatus provides a practical and accurate
way of calibrating the cross-frequency phases of large-signal
network analyzer measurements on arbitrary, irregularly
spaced, and fine frequency grids. Calibration with calibra-
tion apparatus overcomes spacing and placement limitations
of the calibration frequency grids inherent in the current
approach to LSNA calibration, which uses comb generators
to calibrate the cross-frequency phases of large-signal net-
work analyzer measurements.

FIG. 4 shows the measurement apparatus during calibra-
tion. During calibration, the AWG provides sinusoids to the
LSNA at Out 1. These are used to perform the standard
frequency-point-by-frequency-point LSNA scattering-pa-
rameter and power calibrations on port 1 (P1) of the LSNA.
These sinusoids from the AWG Out 1 are also used to
provide a sinusoid at each frequency that can be measured
by both the oscilloscope and the LSNA, a process in which
the oscilloscope need only measure one cycle of the sinu-
soid. A comparison of the phases of the sinusoid measured
by the LSNA and the oscilloscope is used to transfer the
oscilloscope’s cross-frequency phase calibration to the
LSNA.

The AWG in FIG. 4 provides synchronization for the
measurement apparatus in a similar manner to. It generates
a 10 MHz or other lock signal for the VNA and the
oscilloscope trigger signal. The frequency synthesizer also
creates the precision 10 GHz IQ reference signals for
correcting for time-base-distortion for the oscilloscope using
the methods of and the clock signal for the AWG.

‘Afier calibration with the oscilloscope, power meter, and
scattering-parameter calibration standards (shown as an
open, short and load in the figure), these calibration stan-



U.S. Patent Dec. 27, 2022 Sheet 3 of 7 US 11,536,793 B2

200
201
L210 L219 M217
2IN] 205) 232
231 ‘
210 223 229
213 22 fl) Daa Y
L219 226 230
S iN
225, 227 7 ae posn >
h-210 een ee mee)
S
214~] 234
L219
204
5
233

FIG. 3


US 11,536,793 B2

1
CALIBRATION APPARATUS AND
CALIBRATING CROSS-FREQUENCY
PHA OF LARGE-SIGNAL NETWORK
ANALYZER MEASUREMENTS,

CROSS REFERENCE TO RELATED,
APPLICATIONS

‘The application claims priority to U.S. Provisional Patent
Application Ser. No. 62/988,447 filed Mar. 12, 2020, the
disclosure of which is incorporated herein by reference in its
entirety.

STATEMENT REGARDING FEDERALLY
SPONSORED RESEARCH

This invention was made with United States Government
support from the National Institute of Standards and Tech-
nology (NIST), an agency of the United States Department
of Commerce. The Government has certain rights in the
invention. Licensing inquiries may be directed to the Tech-
nology Partnerships Office, NIST, Gaithersburg, Md.,
20899; voice (301) 975-2573; email tpo@nis

BRIEF DESCRIPTION

Disclosed is a calibration apparatus for calibrating cross
frequency phases of large-signal network analyzer measure
ments, the calibration system comprising: a signal generator
that produces a calibration signal and a reference multitone
signal; a vector network analyzer in communication with the
signal generator and comprising a forward coupler, a reverse
coupler, a forward coupled receiver, a reverse coupled
receiver, and a reference receiver and that receives the
calibration signal and the reference multitone signal from
the signal generator; the forward coupler in communication
with the signal generator and that receives the calibration
signal from the signal generator and produces a forward
coupled signal from the calibration signal; the forward
coupled receiver in communication with the forward coupler
and that receives the forward coupled signal from the
forward coupler and produces a forward digitized signal
from the forward coupled signal; the reverse coupler in
communication with the signal generator and that receives
the calibration signal from the signal generator and produces
a reverse coupled signal from the calibration signal; the
reverse coupled receiver in communication with the reverse
coupler and that receives the reverse coupled signal from the

reverse coupler and produces a reverse digitized signal from s

the reverse coupled signal; the reference receiver in com-
munication with the signal generator and that receives the
reference multitone signal from the signal generator and
produces a reference digitized signal from the reference

multitone signal; a calibration receiver in communication s

with the signal generator and the vector network analyzer
and that receives the calibration signal from the vector
network analyzer and produces a digitized calibration tem-
poral signal from the calibration signal; and a signal pro-
cessor in communication with the signal generator and the
vector network analyzer and that: receives the reference
digitized signal from the reference receiver; receives the
forward digitized signal from the forward coupled receiver;
receives the reverse digitized signal from the reverse
coupled receiver; receives the digitized calibration temporal
signal from the calibration receiver; and produces a calibra-
tion factor from the reference digitized signal, the forward

2

digitized signal, the reverse digitized signal, and the digi-
tized calibration temporal signal.

Disclosed is a process for calibrating cross-frequency
phases of large-signal network analyzer measurements, the
process comprising: producing, by a signal generator, a
calibration signal and a reference multitone signal; a vector
network analyzer in communication with the signal genera-
tor and comprising a forward coupler, a reverse coupler, a
forward coupled receiver, a reverse coupled receiver, and a
reference receiver and that receives the calibration signal
and the reference multitone signal from the signal generator;
receiving, by a forward coupler of a vector network ana-
lyzer, the calibration signal from the signal generator; pro-
ducing, by the forward coupler, a forward coupled signal
from the calibration signal; receiving, by a forward coupled
receiver of the vector network analyzer, the forward coupled
signal from the forward coupler; producing, by the forward
coupled receiver, a forward digitized signal from the for-
ward coupled signal; receiving, by a reverse coupler of the
vector network analyzer, the calibration signal from the
signal generator; producing, by the reverse coupler, a reverse
coupled signal from the calibration signal; receiving, by a
reverse coupled receiver of the vector network analyzer, the
reverse coupled signal from the reverse coupler; producing,
by the reverse coupled receiver, a reverse digitized signal
from the reverse coupled signal; receiving, by a reference
receiver of the vector network analyzer, the reference mul-
titone signal from the signal generator; producing, by the
reference receiver, a reference digitized signal from the
reference multitone signal; receiving, by a calibration
receiver, the calibration signal from the vector ne
analyzer; producing, by the calibration receiver,
calibration temporal signal from the calibration signal; and
receiving, by a signal processor, the reference digitized
signal from the reference receiver: receiving, by the signal
processor, the forward digitized signal from the forward
coupled receiver; receiving, by the signal processor, the
reverse digitized signal from the reverse coupled receiver;
receiving, by the signal processor, the digitized calibration
temporal signal from the calibration receiver; and produc-
ing, by the signal processor, a calibration factor from the
reference digitized signal, the forward digitized signal, the
reverse digitized signal, and the digitized calibration tem-
poral signal to calibrate the cross-frequency phases of large-
signal network analyzer measurements.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description cannot be considered limiting
in any way. With reference to the accompanying drawings,
like elements are numbered alike.

FIG. 1 shows a calibration apparatus;

FIG. 2 shows a calibration apparatus;

FIG. 3 shows a calibration apparatus:

FIG. 4 shows a calibration apparatus, wherein after cali-
bration, the oscilloscope, power meter, and scattering-pa-
rameter calibration standards are removeable so that the
vector network analyzer can perform measurements on port
Pl;

FIG. 5 shows time-domain comparisons of an 11-tone 10
MHz multisine measured by the LSNA and oscilloscope. (a)
Signal envelope. (b) Closeup of the signal. The time-base
correction algorithm moves points off of a regular grid. (c)
The difference of the scope and LSNA measurements. (4)
Histogram of the difference of the scope and LSNA mea-
surements, with a mean of 0.2 mV and standard deviation of
1.4 mV;


U.S. Patent Dec. 27, 2022 Sheet 5 of 7 US 11,536,793 B2
0.05 * Scope Measurement
> o-- LENA Measurement
3
zg 0.00
2B
&
~0.05
o 25 50 75 100 125 = «4150
Time (ns)
f@)
0.05 *. Scope Measurement,
S =. LSNA Measurement
7
U
z 0.00
a
€
<
~0.05
0 2 4 6 8
Time (ns)
{b)
cm 9.005 &(Scope ~ LSNA}
2 Cae ee G8 RH
v
y
<
¥
é
QO H

50

100
Time (ns)

2.

se,

1000
5 750
€
— 500
3 j
250 AES
® A(Scope ~ LSN,
8 _ sions

=4

ses

Difference (mV)

i)

FIG. 5


U.S. Patent Dec. 27, 2022 Sheet 4 of 7 US 11,536,793 B2

Calibration Setup
Signal Generation

i | :
| Frequency 10 GH I ck AWG 40 Mite
_ Synthesizer Marker Out uta
Beet ———— .7
1 HH Single tone Multisine
i
Signal Measurengent a
i i |. ESNA
i Li At ma
prey to psi ~ Ag oo
: :
B [90° |: P |
| +

&
Cha Ch3 Trigger Ch?

i (2 3
Calibrated PRL Gee
| Oscilloscope |

FIG. 4


U.S. Patent

Amplitude (arb)

Amplitude (V)

Dec. 27, 2022 Sheet 7 of 7 US 11,536,793 B2

|—- awG
— LSNA

0.02

0.00

0.02

0 10 20 30 40

Time(usec)

(a)

® Scope Measurement
~~ LSNA Measurement

0 2 4 6 8 10

Time (ns)
(b)

FIG. 7


a2) United States Patent

Williams et al.

6793B2

US 11,536,793 B2
Dec. 27, 2022

USO115.

3

(10) Patent No.:
(45) Date of Patent:

G4)

(7)

(72)

(73)

(c29)

(22)
(65)

(60)

(51)

(62)

(58)

CALIBRATION APPARATUS AND
CALIBRATING CROSS-FREQUENCY
PHASES OF LARGE-SIGNAL NETWORK
ANALYZER MEASUREMENTS

Applicant: Government of the United States of
America, as represented by the
Secretary of Commerce, Gaithersburg,
MD (US)

Inventors: Dylan Forrest Williams, Boulder, CO
(US); Aric Warner Sanders,

Broomfield, CO (US)

GOVERNMENT OF THE UNITED
STATES OF AMERICA, AS
REPRESENTED BY THE
SECRETARY OF COMMERCE,
Gaithersburg, MD (US)

Assignee:

Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
U.S.C. 154(b) by 40 days.

Appl. No.: 17/193,441

Filed: Mar. 5, 2021
Prior Publication Data

US 2021/0286036 Al Sep. 16, 2021

Related U.S. Application Data

Provisional application No. 62/988,447, filed on Mar.
12, 2020.

Int. Cl.

GOIR 35/00 (2006.01)

GOIR 27/28 (2006.01)

US. CL.

CPC GOIR 35/007 (2013.01), GOIR 27/28

(2013.01)
Field of
cpc
See appli

lassification Search
GOIR 35/007; GOIR 27/28
tion file for complete search history.

(56) References Cited

U.S. PATENT DOCUMENTS

11,193,965 B2* 12/2021 Pfaffeneder .. H04B 17/309
2004/0066182 AL* 4/2004 Evers ... GOIR 23/14
324/76.23

(Continued)

OTHER PUBLICATIONS,

Remley, K.A., et al., “A Precision Millimeter-Wave Modulated-
Signal Source”, 2013 IEEE MTT-S International Microwave Sym-
posium Digest (MTT), 2013.

(Continued)

Primary Examiner — Akm Zakaria
(74) Attorney, Agent, or Firm — Office of Chief Counsel
for National Institute of Standards and Technology

(57) ABSTRACT

A calibration apparatus calibrates cross-frequency phases of
large-signal network analyzer measurements and includes: a
signal generator; a vector network analyzer that includes
couplers and receivers that receive the calibration signal and
the reference multitone signal from the signal generator; a
calibration receiver that receives a calibration signal from
the vector network analyzer and produces a digitized cali-
bration temporal signal from the calibration signal; and a
signal processor in communication with the signal generator
and the vector network analyzer and that: receives the
reference digitized signal from the reference receiver;
receives the forward digitized signal from the forward
coupled receiver; receives the reverse digitized signal from
the reverse coupled receiver; receives the digitized calibra-
tion temporal signal from the calibration receiv:
produces a calibration factor from the reference di
signal, the forward digitized signal, the reverse digitized
signal, and the digitized calibration temporal signal.

22 Claims, 7 Drawing Sheets



US 11,536,793 B2

5

synchronization signal 210 and timing signal 211; phase
shifter 213 receives synchronization signal 210 from signal
generator 201 and produces phase shifted synchronization
signal 214 from synchronization signal 210; and calibration
receiver 204 receives synchronization signal 210 and timing
signal 211 from signal generator 201, receives phase shifted
synchronization signal 214 from phase shifter 213, triggers
off of timing signal 211, and stabilizes timing based on phase
shifted synchronization signal 214 and synchronization sig-
nal 210.

Inan embodiment, calibration signal 219 includes a single
tone sinusoid. Signal generator 201 can produce single tone
sinusoid at each frequency to be measured by calibration
receiver 204 and vector network analyzer 205. According to
an embodiment, calibration receiver 204 measures a partial
cycle, one cycle, or multiple cycles of single tone sinusoid.
In an embodiment, signal processor 228 compares phases of
the single tone sinusoid measured by vector network ana-
lyzer 205 and calibration receiver 204, wherein calibration
factor 234 includes a cross-frequency phase calibration of
vector network analyzer 205 to calibration receiver 204. In
an embodiment, calibration signal 219 includes multitone
sinusoids and calibration receiver 204 can measure one or
more tones of the multitone sinusoid at once, and signal

processor 228 can compare phases of the sinusoids in the 2

single tone sinusoids measured by vector network analyzer
205 and calibration receiver 204, wherein calibration factor
234 includes a cross-frequency phase calibration of vector
network analyzer 205 to calibration receiver 204. In an
embodiment, reference multitone signal 217 from signal
generator 201 includes a plurality of unknown, stable tones,
and reference multitone signal 217 is a phase reference for
signal generator 201.

In an embodiment, with reference to FIG. 4, calibration
apparatus 200 includes a power meter, scattering-parameter
calibration standards, or a combination of these.

In an embodiment, with reference to FIG. 2, FIG. 3, and
FIG. 4, signal generator 201 produces a timing signal 211;
and calibration receiver 204 receives timing signal 211 from
signal generator 201, and triggers off of timing signal 211

In an embodiment, with re! to FIG. 1, FIG. 2, FIG.
3, and FIG. 4, vector network analyzer 205 receives cali-
bration factor 234 from signal processor 228 and calibrates
forward digitized signal 229, reverse digitized signal 230, or
reference digitized signal 232 based on calibration factor
234. According to an embodiment, vector network analyzer
205 applies calibration factor 234 from signal processor 228
to perform frequency-point-by-frequency-point calibration
of a scattering-parameter and power.

Calibration apparatus 200 can be made from various 5

components. Calibration apparatus 200 can be made from
various elements and components. Signal generator 201 can
include a device that produces electrical signals such as
synchronization signal 210, timing signal 211, reference

multitone signal 217, and calibration signal 219. Exemplary

signal generators 201 include an arbitrary waveform gen-
erator, field programmable gate array, and the like. Timing
signal 211 provides a trigger signal to calibration receiver
204 and can include an arbitrary waveform with a tailorable
magnitude, duty cycle, a frequency. Synchronization signal
210 can be phase shifted by phase shifter 213 to produce
phase shifted synchronization signal 214, wherein calibra-
tion receiver 204 stabilizes its time base based on synchro-
nization signal 210 and phase shifted synchronization signal
214. In this manner synchronization signal 210 is temporally
stable with a selected frequency such as 10 MHz. Instead of
synchronization signal 210 being produced by signal gen-

20

&

&

6

erator 201, frequency synthesizer 216 be in communication
with calibration receiver 204 and produce synchronization
signal 210.

Calibration receiver 204 receives various electrical sig-
nals such as calibration signal 219 and produces digitized
calibration temporal signal 233 from calibration signal 219.
Timing of calibration receiver 204 can be based on a time
base based on timing signal 211 or an internal time base
established from calibration signal 219. Stabilization of the
time base can be performed from synchronization signal 210
or phase shifted synchronization signal 214. In an embodi-
ment, calibration receiver 204 is an oscilloscope. Digitized
calibration temporal signal 233 includes a digized waveform
of calibration signal 219 that has an absolute time scale and
voltage scale, wherein in a graphical format digitized cali-
bration temporal signal 233 can be displayed as a graph of
absolute voltage versus time. Accordingly, digitized calibra-
tion temporal signal 233 can be compared with other signals
by signal processor 228 to produce calibration factor 234.

Vector network analyzer 205 receives calibration signal
219 and reference multitone signal 217 and produces refer-
ence digitized signal 232, forward digitized signal 229, and
reverse digitized signal 230. It is contemplated that signal
processor 228 can be separate from vector network analyzer
205, or signal processor 228 can be part of vector network
analyzer 205. Vector network analyzer 205 can include
various receivers and couplers that receive forward signals,
backward signals, and reference signals and produce wa
forms therefrom that are used in combination with di
calibration temporal signal 233 from calibration receiver
204 in calibration of vector network analyzer 205. Forward
digitized signal 229 and reverse digitized signal 230 are the
forward and backward components in the circuitry for the
waveform of calibration signal 219 while reference multi-
tone signal 217 includes multitone sinusoids. Reference
receiver 231 receives reference multitone signal 217 and
produces reference digitized signal 232 therefrom.

Signal processor 228 receives reference digitized signal
232, forward digitized signal 229, reverse digitized signal
230, and calibration factor 234 from which signal processor
228 produces calibration factor 234. Signal processor 228
can be a stand-alone or integrated computer processor that
can perform analysis according to software instructions or
integrated circuitry that performs specialized operations.
Calibration factor 234 includes numerical quantities, ana-
lytical expressions, or tabular or textual data that used to
calibrate vector network analyzer 205. calibration factor 234
can be contained in vector network analyzer 205 or com-
municated to an external device such as a storage medium or
other hardware for immediate or delayed use.

Calibration apparatus 200 can be made in various ways.
It should be appreciated that calibration apparatus 200
includes a number of optical, electrical, or mechanical
components, wherein such components can be intercon-
nected and placed in communication (e.g., optical commu-
nication, electrical communication, fluid communication,
nical communication, and the like) by physical,
1, optical, or free-space interconnects. The compo-
nents can be disposed on mounts that can be disposed on a
bulkhead for alignment or physical compartmentalization.
As a result, calibration apparatus 200 can be disposed in a
terrestrial environment or space environment

In an embodiment, a process for making calibration
apparatus 200 includes: connecting signal generator 201 in
communication with vector network analyzer 205 by coaxial
cable; connecting signal generator 201 in communication
with calibration receiver 204 by coaxial cable; connecting



US 11,536,793 B2

3

FIG. 6 shows frequency-domain comparison of the
11-tone 10 MHz multisine measured by the LSNA and
oscilloscope. (a) Fractional difference in the voltage mea-
surements. (b) Phase difference of the two measurements;
and

FIG. 7 shows time-domain comparison of an 11-tone 25
kHz multisine. (a) Temporal envelope uploaded to AWG and
measured by LSNA, offset caused by path delay. (b) Time-
domain comparison of LSNA and oscilloscope measure-
ments. The time-base correction algorithm reassigns time
points based on the 10 GHz signal from the frequency
synthesizer.

DETAILED DESCRIPTION.

A detailed description of one or more embodiments is
presented herein by way of exemplification and not limita-
tion.

Large-signal network analyzers (LSNA) add power and

ccross-frequency phase calibrations to a conventional vector- 2

network-analyzer (VNA) scattering-parameter calibration.
These calibration steps allow the LSNA to measure scatter-
ing parameters and the amplitude and phase of the forward
and backward waves at the ports of the LSNA. LSNAs find
applications in nonlinear device characterization, modu-
lated-signal characterization, and the characterization of
devices excited by modulated signals. While LSNAs are
available in both sampler-based and mixer-based architec-
tures, the mixer-based architectures are more common and
can offer higher dynamic range. LSNAs can make use of
comb generators to provide a constant set of constant-phase
reference tones for the LSNA and to calibrate the cross-
frequency phase of the LSNA. However, this may limit the
LSNA to measurements to uniform commensurate fre-
quency grids. As the frequency spacing is reduced, the total
power available in the grid is also reduced, limiting the
upper frequency limit of the LSNA calibration.
Lower-frequency pseudo-random bit sequences (PRBS)
can trigger the comb, moving energy from the harmonics of
the fundamental to a fine grid around the fundamental and a
few harmonics of that fundamental. A similar approach can
generate finely-spaced tones with a chirped input. While this
allows for finer frequency grids, these approaches may not
have flexibility in choice of the grid and can be limited in the
total number and bandwidth of frequency points over which
the LSNA can be calibrated and perform measurements.
Adding a band-pass filter and amplifier after the comb
generator may boost the power available to the LSNA over
the bandwidth of the filter and amplifier that may be useful

for band-limited signals but cannot be applied to perform

measurements on arbitrary frequency grids. A multistep
calibration that stitches multisine signals together in post-
processing may provide broadband calibrations at fine tone
spacings, but stitched multistep calibration processes can

degrade calibration accuracy, particularly when they contain

many stitched frequency bands.

It should be appreciated that a calibration apparatus and
calibrating cross-frequency phases of large-signal network
analyzer measurements described herein overcome these
limitations by using an arbitrary waveform generator
(AWG) to synchronize the measurement apparatus and
providing direct calibration of the LSNA with a calibrated
oscilloscope. This offers a practical and accurate way of
transferring oscilloscope cross-frequency phase calibrations
to LSNAs on arbitrary frequency grids, including arbitrary,
irregularly-spaced, and fine frequency grids. The calibration
apparatus and calibrating cross-frequency phases of large-

&

&

4

signal network analyzer measurements overcome spacing
and placement limitations of the calibration frequency grids
in the conventional approaches to calibration of LSNAs,
which uses comb generators to calibrate the cross-frequency
phases of large-signal network analyzer measurements.

The calibration apparatus and calibrating cross-frequency
phases of large-signal network analyzer measurements
improves synchronization of large-signal network analyzers
and transferring cross-frequency phase calibrations from a
calibrated sampling oscilloscope to the large-signal network
analyzer on an arbitrary frequency grid. Advantageously, the
calibration apparatus and calibrating cross-frequency phases
of large-signal network analyzer measurements can be
applied to measurement of modulated signals and other
waveforms on arbitrary and fine frequency grids. Further,
the calibration apparatus and calibrating cross-frequency
phases of large-signal network analyzer measurements pro-
vides measurement of complex and arbitrarily long signals
traceably with high dynamic range.

Calibration apparatus 200 calibrates cross-frequency
phases of large-signal network analyzer measurements. In
an embodiment, with reference to FIG. 1, FIG. 2, FIG. 3, and
FIG. 4, calibration apparatus 200 includes signal generator
201 that produces calibration signal 219 and reference

5 multitone signal 217: vector network analyzer 205 in com-

munication with signal generator 201 and including forward
coupler 222, reverse coupler 225, forward coupled receiver
224, reverse coupled receiver 227, and reference receiver
231 and that receives calibration signal 219 and reference
multitone signal 217 from signal generator 201; forward
coupler 222 in communication with signal generator 201 and
that receives calibration signal 219 from signal generator
201 and produces forward coupled signal 223 from calibra-
tion signal 219; forward coupled receiver 224 in communi-
cation with forward coupler 222 and that receives forward.
coupled signal 223 from forward coupler 222 and produces
forward digitized signal 229 from forward coupled signal
223; reverse coupler 225 in communication with signal
generator 201 and that receives calibration signal 219 from
signal generator 201 and produces reverse coupled signal
226 from calibration signal 219; reverse coupled receiver
227 in communication with reverse coupler 225 and that
receives reverse coupled signal 226 from reverse coupler
225 and produces reverse digitized signal 230 from reverse
coupled signal 226; reference receiver 231 in communica-
tion with signal generator 201 and that receives reference
multitone signal 217 from signal generator 201 and produces
reference digitized signal 232 from reference multitone
signal 217; calibration receiver 204 in communication with
signal generator 201 and vector network analyzer 205 and
that receives calibration signal 219 from vector network
analyzer 205 and produces digitized calibration temporal
signal 233 from calibration signal 219; and signal processor
228 in communication with vector network analyzer 205 and
calibration receiver 204 and that: receives reference digi-
tized signal 232 from reference receiver 231; receives for-
ward digitized signal 229 from forward coupled receiver
224; receives reverse digitized signal 230 from reverse
coupled receiver 227; receives digitized calibration temporal
signal 233 from calibration receiver 204; and produces
calibration factor 234 from reference digitized signal 232,
forward digitized signal 229, reverse digitized signal 230,
and digitized calibration temporal signal 233.

In an embodiment, with reference to FIG. 3 and FIG. 4,
calibration apparatus 200 includes phase shifter 213 in
communication with signal generator 201 and calibration
receiver 204, such that: signal generator 201 produces



U.S. Patent Dec. 27, 2022 Sheet 6 of 7 US 11,536,793 B2

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Frequency (GHz)

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FIG. 6


US 11,536,793 B2

U.S. Patent Dec. 27, 2022 Sheet 2 of 7
200
201
L-219 p27

21 i q 205} 332
223 229
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FIG. 2



US 11,536,793 B2

11

dards can be disconnected and the LSNA used to measure
modulated forward-wave and backward-wave signals on
port 1 of the LSNA (labeled P1 in FIG. 1). These signals on
PI can be generated by the AWG on Out 1 or externally by
other instruments or devices that are locked to the frequency
synthesizer or AWG.

During both calibration and measurement, the AWG pro-
vides a multisine reference signal on Out 2 for the LSNA
with tones at each of the frequencies of interest. This signal
serves as a phase reference for the LSNA as it makes
measurements. The purpose of this phase reference is to
provide the LSNA with a set of unknown but stable tones to
use as a reference for other signals it measures. In postpro-
cessing each phase measured by the LSNA on P1 is referred
to the fixed phase of the tone at the same frequency
generated on the AWG’s Out 2, minimizing the need accu-
racy in the LSNA’s 10 MHz reference. To minimize distor-
tion in the LSNA, we used a Schroeder multisine to keep the
peak-to-average power ratio low.

A multisine measurement provides tone spacing that
corresponds to the standard minimum spacing of available
comb generators, 10 MHz. This allows easy comparison to
the sampling oscilloscope calibrated measurements. Then,
we illustrate the method on a 25 kHz grid, which requires an
exceedingly long sampling oscilloscope measurement (40 j1s
total time) and highlights the strength of our method.

The oscilloscope was calibrated with a photodiode cali-
brated on the National Institute of Standards and Technolo-
gy’s electro-optic sampling (EOS) system. The LSNA was
calibrated as above with scattering-parameter artifacts, a
power meter, and the EOS-calibrated oscilloscope, from
which we transferred the phase calibration to the LSNA. The
apparatus measured several multisines centered at 1 GHz.

‘After completing the calibrations, we generated an
11-tone Schroeder multisine on Out 1 of the AWG and
measured that multisine with both the LSNA and the cali-
brated oscilloscope. FIG. 5 compares the direct measure-
ment of the signal with the oscilloscope after time-base and
mismatch corrections to the measurement performed by the
LSNA afier transformation to the time domain. FIG. 5(a)
shows that the two instruments measure nearly the same 100
ns long envelope. FIG. 5() shows a closeup view of the
actual signals measured by the two instruments. The two
signals overlap to such a great extent that it is almost
impossible to tell the difference in the plot. FIG. 5(c) shows
that the difference of the two measurements is small and has
no discernible structure. The histogram in FIG. 5(d) shows
the difference to be approximately Gaussian with a mean of

0.2 mV and a standard deviation of 1.4 mV, much smaller 5

than the roughly 100 mV peak-to-peak amplitude of the
signal, identical to the residual distribution of a multisine fit
of the oscilloscope and close to the 1.3 mV ms noise
specification of the manufacturer.

We examined results in the frequency domain to better s

assess the consistency of the LSNA and oscilloscope power-
meter calibrations and the accuracy of the transfer of the
oscilloscope’s cross-frequency phase calibration to the
LSNA. FIG. 6(a) shows that the fractional difference of the
forward-wave voltage measurements made by the oscillo-
scope (Asop¢) and the LSNA (Ay.sy4) are within about 2%
of each other. FIG. 6() shows that the differences in phase
measured by the LSNA and oscilloscope differ by less than
a quarter of a degree, despite that fact that the phase at each
frequency point in the calibration was calibrated separately.
These phase differences correspond to a drift of less than 1
ps in the synchronization of the measurement apparatus.

20

&

65

12

We also created an 11-tone Schroeder multisine on the
AWG with a 25 kHz tone spacing. FIG. 7(a) compares the
envelope of the signal we uploaded to the AWG and mea-
sured with the LSNA. The time offset is due to the various
hardware between the AWG’s converters and the LSNA’s
calibration reference plane at P1, This 25 kHz narrow tone
spacing resulted in a signal with a 40 ys repetition rate, too
long to measure accurately with our sampling oscilloscope.
However, because of the way that the measurement appa-
ratus is synchronized by the AWG, we were able to measure
portions of the signal with our oscilloscope and compare
those to the temporal signal reconstructed by the LSNA, as
shown in FIG. 7(6). Here again, the comparison is excellent,
even at the narrow tone spacing of this multisine.

The calibration apparatus provides a fast, accurate and
practical way of calibrating the cross-frequency phases of
LSNAs on any frequency grid that can be generated with an
AWG and measuring any repetitive communications signal
that we can create with the instrument. We used an AWG to
synchronize the measurements and then transferred the
cross-frequency phase calibration of the oscilloscope to the
LSNA. We verified the approach with two 11-tone mul-
tisines having 10 MHz and 25 kHz tone spacings, demon-
strating that we could transfer the phase calibration of the

5 oscilloscope to the LSNA over a wide range of tone spacing

to within accuracy of a fraction of a degree

While one or more embodiments have been shown and
described, modifications and substitutions may be made
thereto without departing from the spirit and scope of the
invention. Accordingly, it is to be understood that the present
invention has been described by way of illustrations and not
limitation. Embodiments herein can be used independently
or can be combined.

All ranges disclosed herein are inclusive of the endpoints,
and the endpoints are independently combinable with each
other. The ranges are continuous and thus contain every
value and subset thereof in the range. Unless otherwise
stated or contextually inapplicable, all percentages, when
expressing a quantity, are weight percentages. The suflix (8)
as used herein is intended to include both the singular and
the plural of the term that it modifies, thereby including at
east one of that term (e.g., the colorant(s) includes at least
one colorants). Option, optional, or optionally means that
the subsequently described event or circumstance can or
cannot occur, and that the description includes instances
where the event occurs and instances where it does not. As
used herein, combination is inclusive of blends, mixtures,
alloys, reaction products, collection of elements, and the
like.

As used herein, a combination thereof refers to a combi-
nation comprising at least one of the named constituents,
components, compounds, or elements, optionally together
with one or more of the same class of constituents, compo-
nents, compounds, or elements.

All references are incorporated herein by reference.

The use of the terms “a,” “an,” and “the” and similar
referents in the context of describing the invention (espe-
cially in the context of the following claims) are to be
construed to cover both the singular and the plural, unless
otherwise indicated herein or clearly contradicted by con-
text. It can further be noted that the terms first, second,
primary, secondary, and the like herein do not denote any
order, quantity, or importance, but rather are used to distin-
guish one element from another. It will also be understood.
that, although the terms first, second, etc. are, in some
instances, used herein to describe various elements, these
elements should not be limited by these terms. For example,



US 11,536,793 B2

15

receiving, by a forward coupled receiver of the vector
network analyzer, the forward coupled signal from the
forward coupler;

producing, by the forward coupled receiver, a forward
digitized signal from the forward coupled signal;

receiving, by a reverse coupler of the vector network
analyzer, the calibration signal from the signal genera-
tor;

producing, by the reverse coupler, a reverse coupled

signal from the calibration signal:

receiving, by a reverse coupled receiver of the vector
network analyzer, the reverse coupled signal from the
reverse coupler;

producing, by the reverse coupled receiver, a reverse
digitized signal from the reverse coupled signal;

receiving, by a reference receiver of the vector network
analyzer, the reference multitone signal from the signal
generator;

producing, by the reference receiver, a reference digitized

signal from the reference multitone signal:

receiving, by a calibration receiver, the calibration signal
from the vector network analyzer;

producing, by the calibration receiver, a digitized calibra-
tion temporal signal from the calibration signal; and

receiving, by a signal processor, the reference digitized
signal from the reference receiver;

receiving, by the signal processor, the forward digitized
signal from the forward coupled receiver;

receiving, by the signal processor, the reverse digitized
signal from the reverse coupled receiver;

receiving, by the signal processor, the digitized calibra-
tion temporal signal from the calibration receiver; and

producing, by the signal processor, a calibration factor
from the reference digitized signal, the forward digi-
tized signal, the reverse digitized signal, and the digi-
tized calibration temporal signal to calibrate the cross-
frequency phases of large-signal network analyzer
measurements.

13. The process of claim 12, further comprising:

producing, by the signal generator, a synchronization
signal and a timing signal;

receiving, by a phase shifter, the synchronization signal
from the signal generator;

producing, by the phase shifter, a phase shifted synchro-
nization signal from the synchronization signal;

receiving, by the calibration receiver, the synchronization
signal and the timing signal from the signal generator;

3

10

15

20

3

&

&

16

receiving, by the calibration receiver, the phase shifted
synchronization signal from the phase shifter;
triggering the calibration receiver from the timing signal;
and
stabilizing timing of the calibration receiver based on the
phase shifted synchronization signal and the synchro-
nization signal

14. The process of claim 12, further comprising calibrat-
ing: power measurement of the vector network analyzer with
‘a power meter; or scattering-parameters of the calibration
receiver with scattering-parameter calibration standards.

15. The process of claim 12, further comprising:

producing, by the signal generator, a timing signal; and

receiving, by the calibration receiver, the timing signal
from the signal generator; and

triggering the calibration receiver off of the timing signal.

16. The process of claim 12, further comprising’

receiving, by the vector network analyzer, the calibration

factor from the signal processor; and

calibrating the forward digitized signal, the reverse digi-

tized signal, or the reference digitized signal based on
the calibration factor.

17. The process of claim 16, further comprising applying,
by the vector network analyzer, the calibration factor from
the signal processor to perform  frequency-point-by-fre-
quency-point calibration of a scattering-parameter and
power.

18. The process of claim 12, wherein the calibration signal
comprises a single tone sinusoid.

19. The process of claim 18, further comprising produc-
ing, by the signal generator, the single tone sinusoid at each
frequency to be measured by the calibration receiver and the
vector network analyzer.

20. The process of claim 19, further comprising measur-
ing, by the calibration receiver, one cycle of the single tone
sinusoid,

21. The process of claim 20, comparing, by the signal
processor, phases of the single tone sinusoid measured by
the vector network analyzer and the calibration receiver,
such that the calibration factor comprises a cross-frequency
phase calibration of the vector network analyzer to the
calibration receiver.

22. The process of claim 20, wherein the reference
multitone signal from the signal generator comprises a
plurality of unknown, stable tones, and the reference mul-
titone signal is a phase reference for the signal generator.

+e eee


U.S. Patent Dec. 27, 2022 Sheet 1 of 7 US 11,536,793 B2

200
201
L219 217
205] 939
23h 2
223 229
222 224
L219 226 230
225, 227 rg brx->
Kas 234
234
219
204 5
233

FIG. 1


US 11,536,793 B2
Page 2

(56) References Cited
U.S. PATENT DOCUMENTS.

2010/0041353 A1* 2/2010 Alford HO4B 17/101

455/115.1
2017/0026137 A1* 1/2017 Hind . HO4B 17/103
2020/0103485 A1* 4/2020 Anderson . GOIR 35/00

OTHER PUBLICATIONS,

Verbeyst, F, et al., “Next-Generation Comb Generators for Accurate
Modulated Measurements”, IEEE, 2013.

Hale, PD. et al., “A Compact Millimeter-wave Comb Generator for
Calibrating Broadband Vector Receivers”, 2015 85th Microwave
Measurement Conference (ARFIG), 2015, p. 1-4

Reader, H.C., et al., “Comb-Generator Characterization”, IEEE
‘Transactions on Microwave Theory and Techniques, 2008, p. 515-
521, vol. 56 No. 2.

Aldoumani, a., et al., “Operation and Calibration of VNA-based
Large Signal RF I-V Waveform Measurements System without
using a harmonic phase reference standard”, IEEE, 2013

Zhang, Y., et al., “Dense Spectral Grid NVNA Phase Measurements
Using Vector Signal Generators”, IEEE Transactions on Instrumen-
tation and Measurement, 2014, p. 2983-2992, vol. 63 No. 12.
Zhang, Y., et al., “Characterization for Multiharmonic Intermodula-
tion Nonlinearity of RF Power Amplifiers Using a Calibrated
Nonlinear Vector Network Analyzer”, IEEE Transactions on Micro-
wave Theory and Techniques, 2016, p. 291 2-2923, vol. 64 No. 9.
Wang, C.M., et al., “Least-Squares Estimation of Time-Base Dis-
tortion of Sampling Oscilloscopes”, IEEE Transactions on Instru-
mentation and Measurement, 1999, p, 1324-1332, vol. 48 No. 6.
Wang, C.M., et al., “Sequential Estimation of Timebase Corrections
for an Arbitrarily Long Waveform”, IEEE Transactions on Instru-
‘mentation and Measurement, 2012, p. 2689-2694, vol. 61 No. 10.

* cited by examiner


US 11,536,793 B2

7

signal processor 228 in communication with calibration
receiver 204 and vector network analyzer 205 by coaxial
cable; and optionally connecting phase shifter 213 to signal
generator 201 and calibration receiver 204 by coaxial cable.

‘The process for making calibration apparatus 200 also can
include additional timing signals to improve synchroniza-
tion of signal generator 201, calibration receiver 204, and
vector network analyzer 205; or adding upconverters to
signal generator 201 to extend bandwidth.

Calibration apparatus 200 has numerous advantageous
and unexpected benefits and uses. In an embodiment, a
process for calibrating cross-frequency phases of large-
signal network analyzer measurements includes: producing,
by signal generator 201, calibration signal 219 and reference
multitone signal 217 by using an arbitrary waveform gen-
erator programmed to generate calibration signal 219 and
reference multitone signal 217; vector network analyzer 205
in communication with signal generator 201 and including
forward coupler 222, reverse coupler 225, forward coupled

receiver 224, reverse coupled receiver 227, and reference 2

receiver 231 and that receives calibration signal 219 and
reference multitone signal 217 from signal generator 201;
receiving, by forward coupler 222 of vector network ana-
lyzer 208, calibration signal 219 from signal generator 201
by using the internal couplers, mixers or IF digitizers of
vector network analyzer 205; producing, by forward coupler
222, forward coupled signal 223 from calibration signal 219
by using the internal couplers, receivers, mixers and IF
digitizers of vector network analyzer 205; receiving, by
forward coupled receiver 224 of vector network analyzer
205, forward coupled signal 223 from forward coupler 222
by using the internal couplers, receivers, mixers and IF
digitizers of vector network analyzer 205; producing, by
forward coupled receiver 224, forward digitized signal 229
from forward coupled signal 223 by using the internal
couplers, receivers, mixers and IF digitizers of vector net-
work analyzer 205: receiving, by reverse coupler 225 of
vector network analyzer 205, calibration signal 219 from
signal generator 201 by using the internal couplers, receiv-
ers, mixers and IF digitizers of vector network analyzer 205;
producing, by coupler 225, reverse coupled signal
226 from calibration signal 219 by using the internal cou-
plers, receivers, mixers and IF digitizers of vector network
analyzer 205; receiving, by reverse coupled receiver 227 of
vector network analyzer 205, reverse coupled signal 226
from reverse coupler 225 by using the internal couplers,
receivers, mixers and IF digitizers of vector network ana-
lyzer 205; producing, by reverse coupled receiver 227,
reverse digitized signal 230 from reverse coupled signal 226

by using the internal couplers, receivers, mixers and IF

digitizers of vector network analyzer 205; receiving, by
reference receiver 231 of vector network analyzer 208,
reference multitone signal 217 from signal generator 201 by
using the internal couplers, receivers, mixers and IF digi-

tizers of vector network analyzer 205 or by using just the 5

internal receivers, mixers and IF digitizers of vector network
analyzer 205 to improve
receiver 231, reference digitized signal 232 from reference
multitone signal 217 by using the internal couplers, receiv-
ers, mixers and IF digitizers of vector network analyzer 208
or by using just the internal receivers, mixers and IF
digitizers of vector network analyzer 205 to improve sensi-
tivity; receiving, by calibration receiver 204, calibration
signal 219 from vector network analyzer 205 by using the
internal couplers, receivers, mixers and IF digitizers of
vector network analyzer 208; producing, by calibration
receiver 204, digitized calibration temporal signal 233 from

5 ly;

&

&

8

calibration signal 219 by using the internal couplers, receiv-
ers, mixers and IF digitizers of vector network analyzer 205;
and receiving, by signal processor 228, reference digitized
signal 232 from reference receiver 231 by internal digital
hardware and firmware of vector network analyzer 205;
receiving, by signal processor 228, forward digitized signal
229 from forward coupled receiver 224 by internal digital
hardware and firmware of vector network analyzer 205;
receiving, by signal processor 228, reverse digitized signal
230 from reverse coupled receiver 227 by way of the internal
digital hardware and firmware of vector network analyzer
205; receiving, by signal processor 228, digitized calibration
temporal signal 233 from calibration receiver 204 by inter-
nal digital hardware and firmware of vector network ana-
r 205; and producing, by signal processor 228, calibra-
tion factor 234 from reference digitized signal 232, forward
digitized signal 229, reverse digitized signal 230, and digi-
tized calibration temporal signal 233 by internal digital
hardware and firmware of vector network analyzer 205 to
calibrate the cross-frequency phases of large-signal network
analyzer measurements.

In an embodiment, calibrating cross-frequency phases of
large-signal network analyzer measurements further
includes producing, by signal generator 201, synchroniza-
tion signal 210 and timing signal 211 by using an arbitrary
waveform generator programmed to generate synchroniza-
tion signal 210 and timing signal 211; receiving, by phase
shifter 213, synchronization signal 210 from signal genera-
tor 201 by connecting the components with coaxial cables;
producing, by phase shifter 213, phase shifted synchroniza-
tion signal 214 from synchronization signal 210 by using a
hybrid coupler or a signal splitter and different lengths of
cables on each port of the signal splitter; receiving, by
calibration receiver 204, synchronization signal 210 and
timing signal 211 from signal generator 201 by connecting
the components with a coaxial cable; receiving, by calibra-
tion receiver 204, phase shifted synchronization signal 214
from phase shifter 213 by connecting the components with
a coaxial cable; triggering calibration receiver 204 from
timing signal 211 by connecting the components with a
coaxial cable; and stabilizing timing of calibration receiver
204 based on phase shifted synchronization signal 214 and
synchronization signal 210 by signal processing software
that corrects for time-base distortion and jitter.

In an embodiment, calibrating cross-frequency phases of
large-signal network analyzer measurements includes cali-
brating: power measurement of vector network analyzer 205
with a power meter by connecting the power meter to output
port of vector network analyzer 205 and recording readings
of power from the power meter and vector network analyzer
205; or scattering-parameters of vector network analyzer
205 with scattering-parameter calibration standards by con-
necting scattering-parameter calibration standards to ports
of vector network analyzer 205 and measuring reflection and
transmission coefficients of scattering-parameters calibra-
tion standards with vector network analyzer 205.

In an embodiment, calibrating cross-frequency phases of
large-signal network analyzer measurements includes pro-
ducing, by signal generator 201, timing signal 211 by
programming an arbitrary waveform generator to create
timing signal 211; and receiving, by calibration receiver 204,
timing signal 211 from signal generator 201 by connecting
the timing signal created by an arbitrary waveform generator
with a coaxial cable to a measurement port of calibration
receiver 204: and triggering calibration receiver 204 off of
timing signal 211 by using the internal trigger circuitry of
calibration receiver 204.



US 11,536,793 B2

13
a first current could be termed a second current, and,
similarly, a second current could be termed a first current,
without departing from the scope of the various described
embodiments. The first current and the second current are
both currents, but they are not the same condition unless
explicitly stated as such.

The modifier about used in connection with a quantity is
inclusive of the stated value and has the meaning dictated by
the context (e.g., it includes the degree of error associated
with measurement of the particular quantity). The conjune-
tion or is used to link objects of a list or alternatives and is
not disjunctive; rather the elements can be used separately or
can be combined together under appropriate circumstances.

What is claimed is

1. A calibration apparatus for calibrating cross-frequency
phases of large-signal network analyzer measurements, the
calibration apparatus comprising:

a signal generator that produces a calibration signal anda. 2

reference multitone signal;

a vector network analyzer in communication with the
signal generator and comprising a forward coupler, a
reverse coupler, a forward coupled receiver, a reverse
coupled receiver, and a reference receiver and that
receives the calibration signal and the reference mul-
titone signal from the signal generator;

the forward coupler in communication with the signal
generator and that receives the calibration signal from
the signal generator and produces a forward coupled
signal from the calibration signal;

the forward coupled receiver in communication with the
forward coupler and that receives the forward coupled
signal from the forward coupler and produces a forward
digitized signal from the forward coupled signal;

the reverse coupler in communication with the signal
generator and that receives the calibration signal from
the signal generator and produces a reverse coupled
signal from the calibration signal;

the reverse coupled receiver in communication with the
reverse coupler and that receives the reverse coupled
signal from the reverse coupler and produces a reverse

ed signal from the reverse coupled signal;

the reference receiver in communication with the signal

generator and that receives the reference multitone

signal from the signal generator and produces a refer-
ence digitized signal from the reference multitone
signal;

calibration receiver in communication with the signal

generator and the vector network analyzer and that

receives the calibration signal from the vector network
analyzer and produces a digitized calibration temporal
signal from the calibration signal; and

signal processor in communication with the vector

network analyzer and the calibration receiver and that:

receives the reference digitized signal from the refer-
ence receiver

receives the forward digitized signal from the forward
coupled receiver:

receives the reverse digitized signal from the reverse
coupled receiver;

receives the digitized calibration temporal signal from
the calibration receiver; and

produces a calibration factor from the reference digi-
tized signal, the forward digitized signal, the reverse
digitized signal, and the digitized calibration tempo-
ral signal.

2

10

3

0

38

4

0

45

50

35

0

65

14

2. The calibration apparatus of claim 1, further compris-

ing a phase shifter in communication with the signal gen-
erator and the calibration receiver, such that:

the signal generator produces a synchronization signal
and a timing signal;

the phase shifter receives the synchronization signal from
the signal generator and produces a phase shifted
synchronization signal from the synchronization signal;
and

the calibration receiver receives the synchronization sig-
nal and the timing signal from the signal generator,
receives the phase shifted synchronization signal from
the phase shifter, triggers off of the timing signal, and
stabilizes timing based on the phase shifted synchro-
nization signal and the synchronization signal.

3. The calibration apparatus of claim 1, further compris-

ing a power meter, scattering-parameter calibration stan-
dards, or a combination of these.

4. The calibration apparatus of claim 1, wherein the signal

generator produces a timing signal; and

the calibration receiver receives the timing signal from the
signal generator, and triggers off of the timing signal.
5. The calibration apparatus of claim 1, wherein the vector

network analyzer receives the calibration factor from the
signal processor and calibrates the forward digitized signal,
the reverse digitized signal, or the reference digitized signal
based on the calibration factor.

6. The calibration apparatus of claim 5, wherein the vector

network analyzer applies the calibration factor from the
signal processor to perform frequency-point-by-frequency-
point calibration of a scattering-parameter and power.

7. The calibration apparatus of claim 1, wherein the

calibration signal comprises a single tone sinusoid,

8. The calibration apparatus of claim 7, wherein the signal

generator produces the single tone sinusoid at each fre-
quency to be measured by the calibration receiver and the
vector network analyzer.

9. The calibration apparatus of claim 8, wherein the

calibration receiver measures one cycle of the single tone
sinusoid

10. The calibration apparatus of claim 9, wherein the

signal processor compares phases of the single tone sinusoid
measured by the vector network analyzer and the calibration
receiver, such that the calibration factor comprises a cross-
frequency phase calibration of the vector network analyzer
to the calibration receiver.

11. The calibration apparatus of claim 9, wherein the

reference multitone signal from the signal generator com-
prises a plurality of unknown, stable tones, and the reference
multitone signal is a phase reference for the signal generator.

12. A process for calibrating cross-frequency phases of

large-signal network analyzer measurements, the process
comprising:

producing, by a signal generator, a calibration signal and
a reference multitone signal;

a vector network analyzer in communication with the
signal generator and comprising a forward coupler, a
reverse coupler, a forward coupled receiver, a reverse
coupled receiver, and a reference receiver and that
receives the calibration signal and the reference mul-
titone signal from the signal generator;

receiving, by a forward coupler of a vector network
analyzer, the calibration signal from the signal genera-
tor;

producing, by the forward coupler, a forward coupled
signal from the calibration signal;