RF Test Equipment Series: RF Test Probes & Antennas

RF Test Equipment Series: RF Test Probes & Antennas

RF Test Equipment Series: RF Test Probes & Antennas

Outside of coaxial and waveguide interconnect, there are two other main methods of interacting with DUT during RF/microwave/millimeter-wave testing. These methods include surface probes that connect to component leads or microstrip pads, and antennas design for test purposes. Test probes and antennas are used for very different types of testing, but both are crucial in the characterization, compliance, and quality testing of RF devices and components.

RF Test Probes

Testing probes generally consist of either waveguide or coaxial connectors that are adapted to a probe pin pattern. There are several types of probe pattern, including a single pin, ground/signal, ground/signal/ground, coaxial pins, and others. The purpose of these pins is to connect with a component/device test points or pin pads located on a semiconductor wafer, chip surface, or PCB surface. Probes are often used in cases where placing coaxial or waveguide connectors on a surface or component/device is infeasible due to a reduction in performance, cost, or space constraints.

One of the most common uses of RF test probes is with wafer-level testing of components and devices that operate to high frequencies. In some cases, there are RF test probes that are used to test millimeter-wave circuits that operate to a maximum of hundreds of gigahertz. There are also several types of RF test probes that can be soldered or otherwise mechanically attached to a test surface, typically a PCB. These are generally only used when this type of high quality and cost interconnect is strictly necessary, as they generally can’t be rescued without sacrificing interconnect quality.

RF test probes are often used with probing devices that use high calibre positioning mechanics or electronics to allow for small adjustments in probe x, y, z, and sometimes additional axis. Some simple mechanical test probe positioners merely hold the probe in place while testing is being undergone, while more sophisticated probe positioners with robotic features can be programmed to automatically position a probe for high-volume testing applications.

RF Test Antennas

RF test antennas are used when over-the-air (OTA) testing is necessary. This is commonly done with communications standards and electromagnetic compliance (EMC) standards testing. In these test cases the DUT is often placed either in an open-air test range (OATR) with low electromagnetic interference or within an anechoic chamber built for the purpose. These antennas often must meet exact performance descriptions according to the standards. This includes exact gain, directivity, SWR, and positioning requirements.

However, there are also other cases where OTA testing is also useful. These applications include in-house testing to confirm performance and operation during prototyping, with radar, and with devices mounted on platforms, such as with ground vehicles and aircraft. As the type of antenna used for this testing depends on the system being tested, a variety of antenna types are used. These types include conical/horn waveguide, broadband waveguide, omnidirectional waveguide/coaxial, Yagi coaxial, and other antenna types.

Useful Probes and Antennas Links

Courtesy of Pasternack

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