Co-Axial Cable Insertion And Return Loss Measurement Co-axial Cable Insertion and Return Loss Measurement Contents 1. What is return loss 2. Equipment required to measure return-loss of a co-axial cable 3. Measurement of Co-axial cable losses a. Insertion loss measurement b. Return loss measurement 4. The relation between VSWR and Return Loss(Conversion formulas) 5. Glossary of terms 6. References
1. What is Return Loss: Return loss is a measure of VSWR (Voltage Standing Wave Ratio), expressed in decibels (db). The return-loss is caused due to impedance mismatch between two or more circuits. For a simple cable assembly, there will be a mismatch where the connector is mated with the cable. There may be an impedance mismatch caused by nick or cuts in a cable. At microwave frequencies, the material properties as well as the dimensions of the cable or connector plays important role in determining the impedance match or mismatch. A high value of return-loss denotes better quality of the system under test (or device under test). For example, a cable with a return loss of 21 db is better than another similar cable with a return loss of 14 db, and so on.
2.Equipment required to measure return-loss of a co-axial cable: A co-axial cable is chosen to measure the return-loss for study purpose. Typically, for a device or a system, return-loss is measured at the input or at the output. The following equipment are used to measure the return loss of a co-axial cable at microwave frequencies: i. Frequency source ii. Network Analyzer (either a scalar network analyzer or a vector network analyzer) iii. Detector with calibration source. iv. Reflection bridge v. Co-axial Short vi. Cable under test (this could be any device under test) vii. A 10dB attenuator (optional, but recommended).
3.The Measurement of Co-axial cable losses: The measurement process consists of calibrating the test set-up for insertion and return-loss. If you have dual channel network analyzer, both insertion and return losses can be measured simultaneously. You can also measure insertion and return losses separately as is done here. 3.a Insertion loss Measurement: Step 1. Set the sweep source to the required frequency range. Make sure that the output of the sweep source is within the desired amplitude limits, otherwise, it may saturate the detector head and any measurements Convert web pages and HTML files to PDF in your applications with the Pdfcrowd HTML to PDF API
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