Multiport and Multi-site Test Optimization Techniques
Show Description
With the trend towards adding more ports on components, accurate and fast multiport network analysis is required. Optimizing your vector network analyzer (VNA) configuration is critical to minimizing manufacturing cost-oftest. This application note provides an overview of multiport and multi-site test capabilities, how different multiport test solutions compare, and what considerations need to be made when configuring a multi-site test station.
Overview
Driving down the cost-of-test is the key challenge in high-volume component manufacturing. With the trend towards adding more ports on components, accurate and fast multiport network analysis is required. Minimizing operator intervention, as well as reducing connection and calibration times affects measurement throughput. Optimizing your vector network analyzer (VNA) configuration is critical to minimizing cost-of-test.
Modern instruments such as a multiport VNA using a PXI platform with state-of-the-art functions and capabilities are needed to improve the measurement throughput of high-volume production testing. Keysight’s PXI VNA introduces many new capabilities that improve throughput while offering more flexible test configurations than conventional benchtop solutions. For multiport applications, the PXI VNA offers a true multiport capability that allows test engineers to configure up to a 50-port VNA in a single PXI chassis. In addition, it enables multi-site or parallel testing in a reconfigurable form factor that is smaller than many conventional VNA box instruments.
This application note provides an overview of both multiport and multi-site capabilities. What are the different types of multiport test solutions and how do they compare? When configuring a multi-site test station, what considerations need to be made, and what may affect your overall throughput? Throughout the application note, the PXI VNA is introduced along with techniques for optimizing your test station.
Table of Contents
The Expanding Need for Multiport Testing
Types of multiport solutions
Comparing multiport solutions
Multiport calibration
Multi-Site Techniques to Improve Throughput
Considerations when configuring multi-site solutions
Multi-display / multi-user
Optimizing multiport testing with multi-site techniques
The Expanding Need for Multiport Testing
In the early days of network analysis, all measurements were focused on 2-port S-parameters. As the capabilities of VNAs expanded, the ability to test power splitters, mixers, differential devices, and more led to the evolution of the 4-port VNA. Multiport is now considered to be any device that requires more than 4 ports for network analysis.
Today, many components include multiple functions integrated into a single component. The number of ports on these components continues to expand and increase in complexity. Examples include RF front-end module (FEM) that supports multi-band operations in smartphones, multiple-input / multiple-output (MIMO) antennas, and passive interconnect products for high-speed digital applications such as RF connectors or cable assemblies.
While some multiport devices may be tested only as a series of 2-port measurements, many applications require a more thorough multiport characterization of their devices. For example, you may need to make multiple transmission and reflection measurements for 5G Massive MIMO antennas with a high degree of accuracy. Or you may need to quickly evaluate multiple functions on your devices such as S-parameters, noise figure, IMD, and harmonics. With an increasing number of measurement parameters for multiport devices, minimizing total test time is desired by high-volume manufacturers.
Types of multiport solutions
Various multiport measurement solutions are available depending on your performance needs, throughput requirements, and budget.
Simple switching test sets
In the early days, component manufacturers already had either a 2-port or 4-port VNA, so it became a logical next step to add a series of signal routing switches to handle devices with more than 4-ports. As such, the native mode measurements of the VNA are sufficient and all that is required is RF switching to route the VNA ports to the various port pairs of the DUT.
This type of multiport solution uses 2-port measurements for each path from the common port so a 2-port VNA with one common port and one switch port can make all the required measurements. These are sometimes known as switching test sets or simple switch trees.
Switching test sets contain only RF switches formed in a matrix to provide the needed measurement paths. Figure 2 shows an example solution and block diagram of a simple switch tree test set. These test sets are typically constructed from either 1x2 RF switches or 1x4 to 1x6 RF switches. The 1x2 RF switches are sometimes used as some versions provide for an RF load on the unused ports. The 1x4 or 1x6 are typically mechanical switches and may not load the unused ports. If a multiport device has a path response between two ports that depends on the load match of a third port, the switch matrix must provide a load on the unused port. Larger switch configurations that have loads are often not available above 40 GHz, so 1x2 matrix arrays are used. Electronic 1x2 switches are available over a wide range of frequencies, but there are few electronic switches with higher port counts, so electronically switched test sets are typically configured from 1x2 RF switches.
