PRE>Some typical measurements of cables are return loss, VSWR, attenuation, cross talk, and impedance. Return loss: Return loss is the -20 log magnitude of the reflection coefficient and is a direct measurement on network analyzers. SRL (structural return loss) is a mathematical algorithm computed from the reflection coefficient data which can locate periodic cable faults. SRL is available on the 871X family as part of the fault location option. VSWR: VSWR is also computed from the reflection coefficient data. Impedance using TDR methods: This technique involved the generation of a voltage step in time that was propagated down a transmission line. A reflection from an impedance was detected on an oscilloscope and, by measuring the ratio of the input voltage to thereflected voltage, the impedance of simplediscontinuities was calculated. While the traditional TDR was useful as a qualitativetool, the following limitations listed affect its accuracy and utility: Limited rise time, Sampling scope sync jitter, Poor signal to noise ratio, Large step voltage could damage active devices, DC path needed In the early 70's, it was shown that the Fourier Transform of the network reflection coefficient as a function of frequency is the reflection coefficicent as a function of time. Using data measured by a network analyzer in the frequency domain, the response of a network to step and impulse time stimuli can be calculated and displayed as a function of time. This gives traditional TDR capability in reflection and transmission and adds measurement potential in frequency band limited networks. The time domain option is required to get time domain capability in a network analyzer. In the reflection mode a network analyzer measures reflection coefficient as a function of frequency. The reflection coefficient can be viewed as the transfer function relating the incident voltage and reflected voltage. An inverse transform converts the reflection coefficient to a function of time (the impulse response). Step and impulse responses can be calculated by convolving the input step or pulse with this reflection coefficent impulse response. In the transmission mode a network analyzer measures the transfer function of a two port device as a function of frequency. An inverse transform converts the transfer function to the impulse response of the two port device. Step and impulse responses can be calculated by convolving the input step or pulse with the impulse response. Input impedance using a network analyzer: A network analyzer measures the input impedance at its test port. This is not in general the characteristic impedance of the cable. If the cable is long electrically then the input impedance is the characteristic impedance of the cable. An electrically long cable is defined to be a cable for which little reflection is seen from the far end due to the attenuation in the cable. Impedance using an LCR meter: For low frequencies characteristic impedance can be measured by using the so called "open short" method. The open and short circuit impedance is measured on the longest piece of cable that can still be considered a lumped element, usually one tenth of a wavelength. The characteristic impedance is then given by the square root of the product of the two measurements. The drawback of this technique is accuracy. The open and short circuit measurements may be beyond the reasonable accuracy range of the network analyzer. A better method is to measure the open and short circuit impedance using an impedance analyzer that uses a current voltage technique and can therefore measure a wide range of impedance. Attenuation: Attenuation is measured as two port with the source on P1 and the receiver on P2. Crosstalk: Cross talk is measured as two port with the source driving the aggressor cable and the victim cable connected to P2. Revision 2.0 01/24/2000