SNWA014 November   2023 LMH2110

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Log Detector System
    1. 2.1 Block Diagram
    2. 2.2 Output Swing Derivation
    3. 2.3 Simulation Results
  6. 3Power Detector – LMH2110
    1. 3.1 Description
    2. 3.2 Log Conformance
    3. 3.3 Calibration
  7. 4Additional Approaches
    1. 4.1 External ADC Approach
    2. 4.2 Single-Ended Approach
  8. 5Summary
  9. 6References

Abstract

An impedance discontinuity between a RF transmission line and any load, such as an antenna can cause power to be reflected back into the transmission line. This leads to deterioration of the transmission line insulation, transmitter, antenna and quality of transmission. Voltage Standing Wave Ratio or VSWR, is a metric to analyze the quality of transmission & used to keep track of the competence and robustness of transmission.

This application note describes the process of measuring VSWR and demonstrates VSWR measuement with a log detector using Texas Instruments' LMH2110. A fully differential amplifier, THS4561 is used to pre-condition the output of the LMH2110 for a stand-alone ADC or integrated ADC in a microprocessor or FPGA, where the VSWR can be calculated.