RF Test Equipment Series: Cable/Antenna Analyzer 101
Many types of RF test equipment are designed specifically to be used in high accuracy and repeatability test bench applications. These instruments include many spectrum analyzers, network analyzers, signal generators, oscilloscopes, though there are certainly portable and headless (PC-driven) varieties of this equipment out there. However, for technicians and installers, the broad capabilities, complexity, and cost of these traditional instruments aren’t necessary in the field.
Hence, there are several types of portable and application specific RF test equipment options, such as cable analyzers and antenna analyzers. Typically, cable and antenna analyzers support a feature set which is specifically geared toward providing specific measurements rapidly, and are most often contained in a small handheld instrument package. Some of these devices are as specific as to only provide a single function, while more complicated versions may provide enhanced calibration features, power metering, touch screens, large data storage, standards based pass/fail metrics, and more.
Cable and Antenna Analyzer Features & Applications
- * Precision return loss vs. frequency
- * Return loss vs. distance
- * Voltage standing wave ratio (VSWR)
- * Cable loss
- * Distance-to-fault (DTF) measurements
- * Time-domain Reflectometry (TDR) functions
- * Resistive, capacitive, and inductance characteristics of a load
- * Impedance matching
- * Component testing
- * Coaxial cable parameter measurement
- * Cutting coaxial cable at precise electrical lengths
- * Receiver calibration
- * Sensitivity testing
- * Signal tracing
There are a variety of types of cable and antenna analyzers. Some are purpose built for a single application, such as an antenna bridge, while others function as complete single-port analyzers. Typically, modern cable and antenna analyzers include a generator, receiver, and analysis circuitry that is commonly capable of performing Time-domain Reflectometry. With cable reflections measured as a function of time, with some knowledge of the cable material properties and the propagation of the wavefront through the cable, cable and antenna analyzers can present a plot of impedance over distance. This is a useful function for finding faults, tuning, and otherwise optimizing a cable and antenna installation.
For example, a cable and antenna analyzer can be used to determine if there is a fault in a cable by measuring the impedance through the coaxial cable feed line and antenna. In this example, the “good” cable would appear consistently around 50 Ohms, where any fault or poor impedance matching would present a spike or dip from 50 Ohms at a certain distance. Hence, a faulty connector or damaged section of cable/antenna can be replaced.
Much like other RF test equipment, the ports found on cable and antenna analyzers are typically fixed coaxial connectors that may require adapters and couplers. In some cases, an attenuator or coupler may be useful during testing to protect the device from a powerful transmitter.
Pasternack In-series and Between-series Adapters
Pasternack Inline Attenuators
Pasternack RF Couplers