RF Component & Device Test Series: How Are RF Passive Devices Tested

RF passive components are used in virtually every RF assembly and system for communications, sensing, and test and measurement applications. Hence, testing RF passives is critical to all applications. RF passives testing may be for characterization, quality control/verification, or maintenance/troubleshooting depending on the use case of the RF passive and if it is under development, in production, or fielded.

The size, operating frequencies, and interface dictate many of the test parameters to consider when testing RF passives. Some RF passives can readily be tested using coaxial interconnect and a vector network analyzer (VNA), while others may need more rigorous testing at higher power levels or are configured in such a way to may VNA testing challenging.

Common RF Passive Components

• Attenuators
• Equalizers
• Directional couplers
• Hybrid couplers
• Power dividers/combiners
• Circulators/isolators
• Coaxial Assemblies, connectors, and adapters
• Terminations
• Passive Filters (reflective or absorptive)
• Antennas
• Waveguides
• Manual Switches
• Resistors
• Capacitors
• Inductors
• Transformers
• Conductors
• Dielectrics

Generally speaking, an RF passive can be tested by simplifying energizing the device through its ports and measuring the power that escapes, or passes through, the device. This essentially what a VNA does, but this may also be done with a signal generator and power meter if greater error margins are acceptable. In some cases it is desirable to test a RF passive at the power levels it is intended to operate at, in this case a VNA is generally not the appropriate tool, and signal generators, amplifiers, and power meters attached to couplers may be used to protect the sensitive measurement electronics from high signal powers.

RF passives may have one to many ports, depending on the type of device and configuration. For instance, a single antenna or antenna element typically has a single port, while a power divider/combiner or filter may have any number of ports to the practical limit of the fabrication technology (commonly topping out at 1+32 ports, but a greater number is possible). With VNA testing, each port would ideally be connected to a port of a VNA, but practical limits of VNA ports mean that precision terminations may be used instead to enable multiport VNA testing beyond the port count of a given machine. Though this method is typically less accurate than a precision multiport VNA, the cost and accessibility of such VNAs may limit their use cases for some applications.

For very large RF passives, test equipment may require adapters that enable precision interconnect between the test instrument connector ports and the RF passives. Similarly, adapters and probes may be used when testing RF passives that are too small or complex making attaching coaxial or waveguide connectors less desirable. In these cases another type of transmission line may be preferable, such as a planar transmission line or RF probe transmission line, such as a ground-signal-ground probe.

Learn more about Pasternack’s expansive line of RF/Microwave test hardware and systems by following these links:

• Pasternack VNA Calibration Kits
• Pasternack Phase Stable (VNA) Coaxial Cables
• Pasternack Cable Generic Test Cable Assemblies
• Pasternack Skew Matched Pair Coaxial Cable
• Pasternack Precision Coaxial Adapters
• Pasternack In-series and Between-series Adapters
• Pasternack RF Coaxial Probe