RF cable assembly and device test series: how to test RF passive devices

Almost all RF coaxial cable assemblies and systems use RF passive components for communication, sensing, and test and measurement applications. Therefore, testing RF passive devices is essential for all applications. Radio frequency passive device testing may be used for characterization, quality control/verification, or maintenance/troubleshooting, depending on how the radio frequency passive device is used and whether it is being developed, produced, or put into use.

The size, operating frequency and interface determine many test parameters to be considered when testing RF passive devices. Some RF passive devices can be easily tested using coaxial interconnects and vector network analyzers test cable(VNA test cable), while other RF passive devices may need to undergo more rigorous testing at higher power levels, or may be challenging VNA test mode is configured.

Common RF passive components

• Attenuators • Equalizers • Directional couplers • Hybrid couplers • Power splitters/combiners • Circulators/isolators • Coaxial components, connectors and adapters • Terminals • Passive filters (reflective or absorptive) • Antennas • Waveguides • Manual switches • Resistors • Capacitors • Inductors • Transformers • Conductors • Dielectrics

Generally speaking, radio frequency passive devices can be measured by simplifying powering the device through the device port and measuring the power that escapes or passes through the device. This is essentially the job of the VNA test cable, but if a larger error range can be accepted, a signal generator and power meter can also be used. In some cases, it is necessary to test the RF passive equipment at the expected operating power level. In this case, the VNA test cable is usually not a suitable tool. You can use the signal generator, amplifier and power meter connected to the coupler to perform the test. To protect sensitive measurement electronics from high signal power.

RF passive devices may have one to multiple ports, depending on the type and configuration of the device. For example, a single antenna or antenna element usually has a single port, while a power splitter/combiner or filter may have any number of ports to reach the practical limit of the manufacturing technology (usually the limit is reached at 1 + 32 ports, but also There may be a larger value). When using VNA test cable, ideally, each port should be connected to a VNA port, but the actual limit of VNA test cable ports means that precision termination can be used to enable multi-port VNA testing, not the number of ports for a given machine . Although this method is generally not as accurate as a precision multi-port VNA, the cost and accessibility of a precision multi-port VNA may limit its use in certain applications.

For very large RF passive devices, the test equipment may require an adapter to achieve precise interconnection between the test instrument connector port and the RF passive device. Similarly, when testing a radio frequency passive device that is too small or too complex and the connection of coaxial or waveguide connectors is not ideal, adapters and probes may be used. In these cases, another type of transmission line may be preferable, such as a planar transmission line or a rf test probe transmission line, such as a ground signal-ground probe.