Frequently Asked Questions
Company Overview
Spectro Product Line
Technology
Spectro VNA Pro
Spectro VNA
Spectro VSA
Spectro Scope
Company Overview
Who is Constant Wave?
Constant Wave, Inc. is a premier provider of measurement analysis software
for use in the electronics and communications industries. Constant Wave develops, markets, and
sells the Spectro family of products, which analyze data from Vector Network Analyzers (VNAs),
Vector Signal Analyzers (VSAs), and Oscilloscopes. The company was founded in 2008 and is located
in Colorado Springs, Colorado.
Who are Constant Wave’s customers?
R&D and test engineers involved in the design, manufacture and maintenance
of a range of digital, RF and microwave components or systems, and linear and non-linear devices,
such as:
- Mobile phones and devices
- Complex communication systems
- Cables, connectors, switches, filters and antennas
- Amplifiers, mixers and oscillators used with complex modulated signals
What are the application and measurement areas for Constant Wave products?
They include:
- Cellular Communications
- Device characterization and device de-embedding
- Electronics
- Radar
- Radio/Satellite Communications
- Signal Analysis
- Signal Integrity
- Spectrum Management
- WLAN
Spectro Product Line
Do the products run a PC?
Yes. Constant Wave’s line of Spectro software run on Windows-based
PCs and instruments, including: Windows 7, Vista and XP operating systems.
Do the products run directly on instruments (e.g., VNA, VSA, or Oscilloscope)?
Yes. The Spectro family of products can run on a Windows-based instrument (XP, Vista, and 7).
While most modern instruments have a large display integrated into the product, the
high-resolution spectrograms rendered by the Spectro products are best displayed on a
larger screen (10” diagonal or greater).
Are demo copies of the product available?
Yes. Demo copies of all of Constant Wave’s products are available for
a free 30-day trial. The demos are full-featured versions of the products. Contact Constant Wave by
e-mail at sales@constantwave.com or by phone at
(719) 331-2442 to request a demo copy of any of the products.
How do I activate my product?
A license is required to use Constant Wave products. An activation code
must be entered. The code is supplied when the product is purchased, or when a demo subscription
is started. The code is entered into the “Activation Code” window after the software has been
installed on a target PC or Windows-based instrument.
Technology
What is a spectrogram?
A time domain plot will display "when" something happened, but it won't
display "what" happened. A frequency domain plot will display "what" the signal looks like, but
it won't display when it occurred. In order to see the full picture, what is happening and when
it is happening, it is necessary to view the signal in joint time-frequency space, i.e., a
spectrogram. A spectrogram is a time and/or frequency-varying spectral image. Constant Wave
spectrograms display the magnitude of a signal as a function of both time and frequency simultaneously.
In the case of Constant Wave’s analysis software, the most common
format is a three-dimensional graph including time and frequency. The third dimension, indicating
the magnitude of a particular frequency or S-parameter response at a particular time, is represented
by the intensity or color of each point in the image. The color indicates the magnitude of the waveform,
with warmer colors indicating higher magnitude (red and orange) and cooler colors indicating lower
magnitude (blue, purple, and black).
My instrument provides spectrograms, how is Constant Wave’s different?
Instruments, such as VSAs, often provide spectrograms in conventional
“waterfall displays.” The Spectro line of products from Constant Wave provides higher resolution
spectrograms with complex data (time, frequency, magnitude, phase, real and imaginary values). The
product utilizes the time-frequency display as a workspace where any data fragment is selectable and
viewable for detailed analysis.
How does the spectrogram operate as a workspace?
Spectrograms produced by Constant Wave’s software products are more than just
an interesting, colorful display. They are a useful tool for the display and analysis of device
characteristics and signal waveforms.
Constant Wave has greatly enhanced spectrogram utility through improvements
in the resolution of the images produced by its software. Each data point within a spectrogram
represents complex values of time, frequency, magnitude, phase, real and imaginary values. A variety
of post-processing tools allow detailed analysis of any data fragment within the joint time-frequency
space. Sections of the spectrogram can be selected and isolated for more in-depth analysis.
What is joint time-frequency processing?
Joint time-frequency processing is the core of Constant Wave’s analysis
products. Frequency domain and time domain views are two extremes. In the frequency domain, there
is no notion of time. In the time domain, there is no notion of frequency. A simultaneous display
of time and frequency information is accomplished with the appropriate transform of the original
measured data. The result is a unique spectrographic view of measured data, presenting the characteristics
of device performance in both the time domain and frequency domain concurrently.
How does joint time-frequency processing apply to signal analysis?
Joint time-frequency processing is typically seen on Vector Signal Analyzers in
the form of spectrograms. The most common implementation has frequency on the horizontal scale and
time on the vertical scale. Color is used to indicate the signal magnitude at a moment in time, at a
frequency. Constant Wave’s implementation yields extremely high resolution spectrograms which reveals
the fine detail of signal behavior. This enhanced image quality helps the user see aspects of signal
behavior which are impossible to see with other views of the data, or are not well resolved using
lower resolution implementations of spectrogram generation.
In addition to high resolution imagery, Constant Wave’s spectrograms introduce
the concept of the image as a workspace. More than just a display, various post-processing tools can
be applied to the spectrogram to extract further information from the data. Of particular value is the
ability to extract the signal from rectangular regions of the joint time-frequency space. This processing
behaves much like cutting out a signal in time and in frequency. The closest analogy from traditional
signal processing would be a filter with extremely fast roll-off in frequency, being applied to a limited
range in time. Because of the properties of joint time-frequency processing, this filtering can be done
without mathematical distortion.
How does joint time-frequency processing apply to device characterization?
Joint time-frequency processing in the form of spectrograms is commonly applied
to signals. Constant Wave applies this powerful data visualization tool to the S-parameters of a device.
A VNA measures the device S-parameters and Spectro VNA processes the data to produce joint time-frequency
representations of the data. These device spectrograms are very compact representations which reveal
device performance in a way that simple frequency domain or time domain plots cannot. Normal VNA time
domain processing is very useful for separating the different propagation paths through the measured
device, however, it does not show the frequency behavior of each of those paths. Joint time-frequency
processing separates the propagation paths and reveals the frequency response for each of those paths.
A spectrogram for an S-parameter has time on the horizontal axis and frequency
on the vertical axis. The color represents the magnitude (in dB) of the S-parameter, at a moment in time,
at a frequency. Although the magnitude is used to color the plot, the entire joint time-frequency space
is complex valued. This allows powerful post-processing tools to be applied to the spectrogram to extract
different aspects of the measured network’s behavior. Selection of fragments of the joint time-frequency
space can be used much like gating in traditional VNA time domain analysis, but without the mathematical
distortions which accompany that type of processing.
What is Time Domain Substitution?
Time Domain Substitution (TDS) is a new methodology for de-embedding S-parameter
device characteristics measured using a Vector Network Analyzer (VNA). TDS is based on a new understanding
of time domain processing for VNAs.
Until now, the understanding of the utility of time domain processing with VNAs
has been as an analogy to Time Domain Reflectometry (TDR). This understanding has led to qualitative
uses of time domain processing. For example, a discontinuity in a transmission line could be characterized
as inductive or capacitive, but the actual value of inductance or capacitance could not be determined.
The key understanding for using VNA time domain processing as a quantitative
tool is that time domain processing characterizes paths rather than discontinuities. Time domain
processing for VNAs is not a characterization of discontinuities, as implied by the analogy with TDR,
but, rather a characterization of propagation paths. With this different view, a significant VNA
measurement problem can be solved.
What are the measurement capabilities of TDS?
Time Domain Substitution is helpful for removing the effects of PC boards
or other circuit elements that lie between the calibration reference plane of a VNA and the DUT.
By doing so, engineers can easily characterize a range of embedded devices.
TDS can be used to make one and two-port measurements. It can also be
applied to n-port devices. A particular advantage for characterizing multi-port devices is that
TDS does not require port-to-port standards in order to de-embed multi-port measurements.
How can I get more information about Time Domain Substitution and Joint Time-Frequency Processing?
There are several white papers available on the Constant Wave website
describing joint time-frequency processing and analysis, Time Domain Substitution and product
applications. Links to the white papers can be found on the product pages of the website, the
Library menu of the website, and the Help menu in the products.
Spectro VNA Pro
What are the differences between Spectro VNA Pro and Spectro VNA?
Spectro VNA allows engineers to easily observe device S-parameters
in the frequency domain, time domain, or in the joint time-frequency domain. Spectro VNA Pro
adds the ability to characterize the performance of embedded devices using Time Domain Substitution.
Which instruments does the product work with?
Spectro VNA Pro is compatible with most s1p, s2p, s3p, and
s4p files. Spectro VNA Pro can also access data files directly from the instrument.
VNA instrument interfaces supported include:
- Agilent ENA, PNA, and PNA-X
- Anritsu 37000
- Rohde & Schwarz ZVA and ZVB
Why should Spectro VNA Pro be part of an overall measurement solution?
Use of Spectro VNA Pro simplifies the characterization of embedded
devices on a PC board. Measurements are simple to set-up and execute, requiring only a
VNA, port cables, a coax calibration kit or module, and the ability to create a single
standard (short) at the DUT.
For multi-port devices, measurements take less time. Engineers have
greater control over their measurement environment. In many cases, the costs and complexity
associated with probing stations or external board characterizations can be eliminated.
What customer problems does Spectro VNA Pro solve?
A common measurement problem involving Vector Network Analyzers
(VNAs) involves projecting the measurement accuracy from a reference plane, established
through calibration, to another location (the DUT).
Moving the reference plane may be necessary because it may not
be convenient, or even possible, to perform a calibration at the desired location (the DUT).
This might result from a lack of appropriate calibration standards or, perhaps, from a lack of
suitability of the desired location for the insertion of multiple calibration standards.
A common approach to this problem is to use some type of methodology
to extend the reference plane. Constant Wave’s approach, called Time Domain Substitution,
produces results which rival full calibration accuracy at the DUT.
How is TDS de-embedding different from conventional techniques?
When using Port Extension, the location of the reference plane is
moved by mathematically removing a length of transmission line from the measured S-parameters.
If the mathematic model represents a lossless transmission line, only the phase of the
S-parameters is affected. If the transmission line is lossy, both the magnitude and
phase are affected.
When using Frequency Gated by Time, one reflection in the time
domain is selected using a gate function. This gate suppresses all parts of the time
domain response which are not within the gate. A frequency domain response is created
from just the part of the time domain within the gate. The result is a frequency domain
response free from the effects of multiple reflections.
However, intervening elements between the calibration reference
plane and the element chosen by gating can alter the apparent frequency domain response of
the gated discontinuity. A new approach to address this problem, called Time Domain
Substitution, has been introduced by Constant Wave. Like Frequency Gated by Time,
this method uses time domain processing.
The frequency domain responses measured by a VNA are what is
more generally known as transfer functions. The time domain responses computed from
these transfer functions are more generally known as impulse response functions. The
Frequency Gated by Time responses computed by selecting a portion of the impulse
response functions and transforming back to the frequency domain are, again, transfer
functions. However, these transfer functions are based on only a portion of the total
impulse response of the DUT. By careful selection of which parts of the impulse response
are used in the computation of the transfer function, the transfer function for different
propagation paths within the device under test can be determined.
What are the benefits of Spectro VNA Pro?
For a variety of applications, the cost of a total VNA-based
test solution can be significantly reduced. The use of Spectro VNA Pro with a VNA can eliminate
the need for expensive accessories, such as probing stations, probes and custom calibration standards.
For designers who rely on external PC board characterizations to determine
device performance, the number of board turns can be reduced significantly or eliminated.
For R&D and test engineers, the time to insight can be decreased
significantly. Device characterization is much less complex, as the number of discrete measurements
is reduced. In addition, the use of high-definition spectrograms can reveal issues associated with
device performance more quickly.
Calibration measurements that are relatively simple and straight forward
in a coaxial environment are difficult when devices are mounted directly on a PC board. Using Time
Domain Substitution, Spectro VNA Pro provides a simple, yet powerful, method for de-embedding devices
mounted on a PC board.
Spectro VNA
What are the benefits of Spectro VNA?
For R&D and test engineers, the time to insight can be decreased
significantly. Device characterization is much less complex, as the number of discrete
measurements is reduced. In addition, the use of high-definition spectrograms can reveal issues
associated with device performance more quickly.
Which instruments does the product work with?
Spectro VNA Pro is compatible with most s1p, s2p, s3p and s4p files.
Spectro VNA Pro can also access data files directly from the instrument. VNA instrument
interfaces supported include:
- Agilent ENA, PNA, and PNA-X
- Anritsu 37000
- Rohde & Schwarz ZVA and ZVB
Spectro VSA
What are the benefits of Spectro VSA?
Constant Wave’s unique spectrographic analysis presents the characteristics of
signals in both the time domain and frequency domain simultaneously. Unlike traditional VSA display
methods, which can mask response characteristics, Spectro VSA allows selection and observation of
the response of the device at any specific time or frequency.
With Spectro VSA, engineers can:
- Produce high-quality spectrogram images generated with “High Definition” signal processing.
- Visualize signal characteristics in three dimensions – time, frequency and amplitude.
- Drill down into trouble spots, extracting IQ signals from any fragment of time-frequency space.
- Find which signal characteristics are causing spectral regrowth problems.
- Save time and money by identifying signal problems quickly.
Which instruments does the product work with?
Spectro VSA is compatible with most IQ txt files including Tektronix
.tiq files. Spectro VSA can also access data files directly from the instrument. VSA instrument
interfaces supported include the Agilent EXA and MXA
Spectro Scope
What are the benefits of Spectro Scope?
For R&D and test engineers, the time to insight can be decreased
significantly. Spectro Scope allows users to investigate spectral events clearly, with
extraordinary detail. Knowing when unusual signal discontinuities are occurring can save
debugging time. In addition, various post-processing tools allow engineers to select any
fragment of time-frequency for detailed analysis, without distortion.
With Spectro Scope, engineers can:
- Produce high-quality spectrogram images generated with “High Definition” waveform processing.
- Visualize waveform characteristics in three dimensions – time, frequency and amplitude.
- Find which waveform irregularities are causing problems.
- Drill down into trouble spots, extracting waveforms from any fragment of time-frequency space.
- Save time and money by identifying design or system problems quickly.
Which instruments does the product work with?
Spectro Scope is compatible with most data files in text.csv or WAV formats.
Spectro Scope can also access data files directly from the instrument. Oscilloscope instrument
interfaces supported include:
- Agilent Infiniium family
- Tektronix DPO 7000-series
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