Migrating from Scalar to Vector
Network Analyzer Systems
A New Standard for Low-cost Basic RF Network Analysis
In the fast-paced world of RF manufacturing test, it is important to stay current and competitive.
The popularity of scalar analyzers for network analysis measurements has declined greatly over the past ten years, as the usage of low-cost, accurate, and easy-to-use vector network analyzers (VNAs) has dramatically increased. With the advent of lower-cost VNAs, the economic benefits of a scalar solution have diminished.
The majority of scalar network analyzer users have already begun migrating to high-performance, low-cost network analyzers such as Keysight Technologies, Inc’s ENA, ENA-L, and PNA-L network analyzers. Now is the time to consider a test migration path.
Historical advantages of scalar analyzers
Scalar analyzers have been very popular for making basic RF and microwave measurements for many years. Scalar analyzers combine a simple measurement configuration with basic scalar measurements to provide fast, economical scalar measurements on a variety of RF and microwave devices.
Scalar analyzers have been used to measure gain and gain flatness of amplifiers, filter responses, return loss, and mixer conversion loss. For these basic measurements a scalar analyzer has been a simple, basic, and cost-effective measurement solution.
Today’s advantages of vector network analyzers - more measurements and better accuracy
The demand for new types of measurements and improved test performance has accelerated the need for higher performance measurements, which has driven the advancement of VNAs, both in capabilities as well as driving the price point of vector analyzers down. Today, VNAs provide significantly greater measurement capabilities and accuracies than are available from scalar measurement solutions.
VNAs measure amplitude and phase response, which allows vector error correction techniques to be used for calibration, removing systematic measurement errors, and providing greater measurement accuracy. Phase measurements also provide additional information about the devices, characterizing the complex impedance of the device as well as the group delay response.
The ability to measure phase allows for more complete characterization of devices, as well as more accurate measurements. Additionally, VNAs utilize a tuned receiver approach, as opposed to a broadband detector used by scalar analyzers, and this provides greater dynamic range, and eliminates false measurement responses due to extraneous signals such as source harmonics.
VNAs also utilize modern data archiving techniques, making it very easy to store, retrieve, and print a data trace using the modern Windows capabilities of vector network analyzers.
While VNAs have many advanced measurement capabilities, they also have the ability to make basic measurements similar to a scalar analyzer. A VNA can perform a trace normalization or simple response calibration, without using a calibration kit, providing measurement capabilities similar to a scalar analyzer. Unlike scalar network analyzers a VNA system offers greater than 100 dB of dynamic range.
Clearly the advantages of the vector network analyzer have driven the migration from scalar analyzer systems to vector systems.
Take a look at a price comparison
Did you know you can buy a 50 GHz VNA for about the same price as a 50 GHz scalar analyzer system?
In the past, one of the basic advantages of scalar analyzers was their ability to make basic microwave measurements with a lower initial capital investment in the measurement system. With the evolution and advancements in vector analyzers, the price advantage of scalar analyzers has diminished. The table below illustrates the comparative prices between a VNA system and a scalar analyzer system by frequency ranges.
For RF frequencies below 3 GHz, a VNA costs only 40-50% of a comparable scalar analyzer system. The cost of a vector and scalar system are approximately equivalent for a 6 GHz measurement system. A 20 GHz vector measurement system is 1.5 times the cost of a scalar system, while a 40 GHz system is approximately 1.3 times the cost, and a 50 GHz vector system is only 1.1 times the cost of a scalar system. For millimeter-wave frequencies above 67 GHz in waveguide bands, scalar measurement systems still have a price advantage.
Scalar analyzers have been used for many years to make basic network analyzer measurements on a variety of RF and microwave components. Shown here are some of the more common devices measured by scalar analyzers, and the equivalent configurations, features, and capabilities available from various recommended replacement VNAs.
Scalar analyzers have been used for many years to make basic measurements on amplifiers. Common measurements performed with scalar analyzers are gain, gain flatness, gain compression, return loss and/or VSWR, reverse isolation, and absolute power measurements. The calibration of a scalar analyzer system utilizes a short, open, and thru connection.
The averaging of the short and open response provides normalization for the reflection frequency response. The thru characterizes the transmission frequency response of the measurement system.
Systematic errors due to directivity, source and load match are present in both the calibration and measurement of the amplifier, and are not removed by the open, short, and load calibration of the scalar analyzer, and thus contribute to measurement uncertainty when measured with a scalar analyzer.
VNAs have become quite popular for measuring amplifiers for many reasons. Vector analyzers have built-in RF sources, signal separation devices, and detectors, which greatly simplify the measurement configuration and the measurements.
Vector analyzers can measure magnitude and phase responses, allowing systematic errors of source match, load match, and directivity to be completely characterized and mathematically removed from the measurement, greatly reducing the measurement uncertainty, and improving the measurement accuracy.
Additionally, the ability to measure the phase response of an amplifier allows the VNA to measure S-parameters to characterize the complex impedance of the amplifier, and measure group delay and deviation from linear phase contributed by the amplifier. For all these reasons, VNAs have become the preferred instrumentation system for complete and accurate characterization of amplifiers.
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