Anritsu S251C manual Information Required for a Line Sweep, Measurements

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Chapter 4 Measurements

The performance of a transmission feed line system may be affected by excessive signal re- flection and cable loss. Signal reflection occurs when the RF signal reflects back due to an impedance mismatch or change in impedance caused by excessive kinking or bending of the transmission line. Cable loss is caused by attenuation of the signal as it passes through the transmission line and connectors.

To verify the performance of the transmission feed line system and analyze these problems, three types of line sweeps are required:

Return Loss Measurement￿Measures the reflected power of the system in decibels (dB). This measurement can also be taken in the Voltage Standing Wave Ratio (VSWR) mode, which is the ratio of the transmitted power to the reflected power. However, the return loss measurement is typically used for most field applications.

Insertion Loss Measurement￿Measures the energy absorbed, or lost, by the transmission line in dB/ft or dB/meter. Different transmission lines have different losses, and the loss is frequency and distance specific. The higher the frequency or longer the distance, the greater the loss.

Distance-To-Fault (DTF) Measurement￿Reveals the precise fault location of compo- nents in the transmission line system. This test helps to identify specific problems in the system, such as connector transitions, jumpers, kinks in the cable or moisture intrusion.

The different measurements are defined as:

Return Loss - System Sweep￿A measurement made when the antenna is connected at the end of the transmission line. This measurement provides an analysis of how the various components of the system are interacting and provides an aggregate return loss of the entire system.

Distance To Fault - Load Sweep￿A measurement made with the antenna disconnected and replaced with a 50￿ precision load at the end of the transmission line. This measure- ment allows analysis of the various components of the transmission feed line system in the DTF mode.

Cable Loss - Insertion Loss Sweep￿A measurement made when a short is connected at the end of the transmission line. This condition allows analysis of the signal loss through the transmission line and identifies the problems in the system. High insertion loss in the feed line or jumpers can contribute to poor system performance and loss of coverage.

This whole process of measurements and testing the transmission line system is called Line Sweeping.

Information Required for a Line Sweep

The following information must be determined before attempting a line sweep measure- ment:

￿System Frequency Range, to set the sweep frequency

￿Cable Type, to set the cable characteristics for DTF measurements

￿Distance of the Cable Run, to set the distance for DTF measurements

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Contents Site Master Model S251C Antenna Cable Analyzer Page Warranty Page Table of Contents Cable & Antenna Analysis Iii/iv Description Standard AccessoriesIntroduction Options Optional AccessoriesPerformance Specifications Description Site Master Performance Specifications 2 ESD Precautions Preventive MaintenanceAnnual Verification Anritsu Service Centers Chapter Functions and Operations Test Connector PanelActive Function Block Soft Keys Front Panel OverviewMode Function Hard KeysClear Keypad Hard KeysAuto MODE=FREQ FREQ/DIST Softkeys Soft KeysMODE=DTF FREQ/DIST Softkeys Functions and Operations Amplitude MODE=POWER Monitor Softkeys Power Monitor Menu OptionMODE=RF Source Softkeys RF Source MenuLimit Segment 1 Segment SYS Self Test SymbolsSelf Test Errors Error CodesERRORD2 Range ErrorsCharging the Battery in the Optional Charger Battery InformationCharging a New Battery Charging the Battery in the Site MasterBattery Life Battery Charge IndicatorImportant Battery Information Chapter Getting Started Power On ProcedureCalibration Select the Frequency or DistanceCalibration Calibration Procedure Single PortRF in Test Port RF OUT Test Port Calibration Procedure Dual PortSave and Recall a Display Setting the ScaleSave and Recall a Setup Recalling a Display Changing the Display Language Set the Distance and Cable TypeChanging the Units Printing a Screen PrintingPrinter Printer Switch SettingsUsing the Site Master Soft Carrying Case Using the Soft Carrying CaseLine Sweep Fundamentals One Port MeasurementsMeasurements Information Required for a Line SweepSystem Return Loss Measurement Typical Line Sweep Test Procedures2is an example of a typical system return loss trace Insertion Loss Measurement Procedure Cable Loss ModeType Attenuation dB/ft Length ft = Loss dB Procedure Return Loss Mode Procedure DTF-Return Loss Mode Distance-To-Fault DTF Transmission Line TestProcedure DTF-SWR Mode Antenna Subsystem Return Loss Test Vswr Introduction Two Port MeasurementsTMA-S TMA MeasurementsTMA Gain Measurement After Calibration TMA-DD 12. TMA-DD Gain Measurement TMA-D 14. TMA-D Gain Measurement 15. System Isolation Antenna to Antenna IsolationAntenna-to-Antenna Isolation Measurement Quency settings for common systems21/4-22 System Requirements FeaturesCommunication Port Setting InstallationDownloading Traces from the Site Master Using Software ToolsInterface Cable Installation Plot Properties Plot CaptureSaving Traces Trace Overlay or Plot OverlaySaving a Plot to a Spreadsheet Custom Cable ListPrinting Formats Creating a DatabaseAppendix a Reference Data Coaxial Cable Technical DataAppendix a Reference Data A-4 Examples Appendix B WindowingAppendix B Windowing B-4
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