Techniques for Advanced Cable Testing
应用文章
When the purpose of the transmission line is to interconnect devices and distribute signals, the physical geometries of the conductors and dielectric properties of the supporting material will be uniform across the length of the line. When a change occurs in these characteristics, such as point of contact between two different lines or damage along the line, these discontinuities may result in signal reflection and higher line attenuation. Characterizing and troubleshooting transmission lines and systems require measuring the performance in both the frequency domain and time domain. Frequency domain measurements are typically used to verify the RF performance over the specified frequency range of interest. Time domain and distance domain measurements are typically used to physically locate discontinuities along the line. Figure 1a and Figure 1b show typical frequency domain and time domain measurements using Keysight’s FieldFox handheld analyzer. Figure 1a shows the measured amplitude and phase response for the reflected (S11) signal over a range of 12 GHz. In this case, the device under test (DUT) is a short length of coaxial cable terminated with a short. Figure 1b shows the measured input impedance of the same cable/short as a function of time.