RF Range Calculator

by <a href="http://community.silabs.com/t5/Welcome-and-Announcements/Community-Ranking-System-and-Recognition-Program/m-p/140490#U140490"><font color="#000000"><font size="2">Hero Employee</font></font> </a> dasimon on ‎05-02-2017 09:19 AM

Silicon Labs provides an RF range calculator for customers to help estimating the actual range for their wireless applications:

 

http://www.silabs.com/documents/public/software/RF-Range-Calculator.zip


The range depends on the following parameters:

  • Conducted TX output power: the power driven to the antenna input [dBm]
  • TX antenna gain [dBi]
  • Conducted receiver sensitivity [dBm]
  • RX antenna gain [dBi]
  • Frequency [MHz]
  • Propagation factor (depends on the environment):
    - n = 2 for ideal free space propagation
    - n = 2.8-3 for typical line of sight propagation
    - n = 4 for outdoor wet soil
    - For multi-path propagation (indoor or outdoor with several buildings/objects) “n” can vary between 4 and 6 based on the actual environment

The range calculator provides 3 options for TX:

  • Use published TX EIRP for radios and antennas (for Si4x2x only)
  • Direct entry of TX EIRP [dBm]
  • Direct entry of conducted TX output power [dBm] and antenna gain [dBi]

The possible options for RX are the following:

  • Use published RX sensitivity for radios and antennas (for Si4x2x only)
  • Direct entry of RX sensitivity [mV/m]
  • Direct entry of conducted RX sensitivity [dBm] and antenna gain [dBi]

A typical range calculation is shown below.

 

Excel_spreadsheet.png

 

The calculation uses an output power of 13dBm and a receiver sensitivity of -100dBm. Assuming 0dBi antenna gain for both TX and RX, the typical line of sight range at 868MHz is ~1000m.

 

Note: The calculation provides a good approximation on the expected range, however the range strongly depends on the propagation factor (environment). Using a propagation factor value of 4 (typical for indoor environment) results ~150m range if all other parameters remain the same as in the above example.