Coaxial Probes and Cable Mounted Probes Overview

During the prototyping and testing of RF devices, many times it is necessary to test at non-port locations of the circuit to optimize the design or troubleshoot problems.probe test system However, testing at higher frequencies is an even greater challenge because the lack of impedance matching between the RF transmission line and the voltage probe can lead to large deviations in results when using conventional voltage probes.

Therefore, RF test probes must have an impedance that matches the test point. It is common practice to solder RF coaxial cables (pigtails) to test points pre-planned in the design. This helps to ensure adequate impedance matching and the test point can be selected in an area that has less impact on the overall design performance. Other methods include soldering dedicated RF probes to custom pads or lead designs to reduce intrusive probing.RF probes High-performance test equipment suppliers can provide specialized probes up to millimeter-wave frequencies. However, these probes are typically more expensive at the end and do not provide continuous access to the circuitry that makes up the component. As a result, they are limited in high-volume test applications or troubleshooting applications, and are better suited for prototyping and R&D.

Other available options include wafer probe stations and matching pogo-pin probes, or other flexible probes. Since the calibration card is ideally calibrated at the test point (close to the exact probe location), the probes bring minimal impact while still providing the highest fidelity configuration.

A more recent option is the use of coaxial RF cable-mounted probes, which combine the features of probe station accuracy and repeatability with the accessibility of specialized probes. These probes have edges similar to those of a probe table probe fixture - ground-signal-ground (GSG) or ground-signal (GS) - with a pogo-pin probe on one end and a typical coaxial connector on the other. These new probes are capable of reaching 40 GHz with return loss better than 10 dB. pogo-pin probes are available in the range of 800 µm to 1500 µm, and these probes are typically terminated with either a 3.5 mm female or 2.92 mm female coaxial connector. As with the probe bench, a pad port can be designed to minimize impact in a particular test area, or the probes can be placed on terminals or microstrip transmission lines close to the component.

Cable mounted probes can be used either manually or with a multi-axis probe positioner.probe card Unlike typical probe stations, these probes are large enough for the operator to use manually and are very reliable. The probe positioners provide greater positional accuracy and repeatability and can be placed by themselves for easy testing. Unlike probe stations, coaxial cable-mounted probes and positioners can be used as network analyzers, signal generators, spectrum analyzers, oscilloscopes, and other accessories for RF/microwave, millimeter-wave, and high-speed digital applications on an engineer or technician's typical test bench. Cable-mounted RF probes have a small footprint, are non-damaging, and have a non-intrusive design for testing in high-density applications such as antenna arrays, metamaterials, fractal antennas, microstrip transmission lines, compact assemblies, and printed circuit boards with tiny surface-mounted packaging components.