Effective Isotropic Sensitivity
Understanding EIS
EIS provides a complete system-level sensitivity specification that includes both the receiver and antenna performance. It directly indicates the weakest free-space signal that the system can detect.
EIS Calculation
Example: 5G base station at 3.5 GHz
Receiver sensitivity: -100 dBm
Antenna gain: 23 dBi (64 element array)
EIS = -100 - 23 = -123 dBm
This means the base station can detect a signal
with free-space power density of -123 dBm.
EIS Applications
- 3GPP specifications: Base station EIS requirements for each band and bandwidth.
- Handset testing: OTA (Over-The-Air) testing measures total radiated sensitivity, similar to EIS.
- Satellite terminals: G/T (gain-to-noise temperature ratio) is a related sensitivity metric.
Frequently Asked Questions
What is EIS?
EIS is the minimum free-space signal power that produces acceptable quality. EIS = receiver sensitivity - antenna gain. It is the receive counterpart of EIRP and gives a complete system-level sensitivity specification.
How is EIS related to G/T?
Both express system sensitivity. G/T = antenna gain / system noise temperature (in dB/K). EIS = sensitivity - antenna gain (in dBm). G/T is preferred for satellite systems; EIS for cellular. They convey similar information differently.
What EIS is needed for 5G?
3GPP specifies EIS requirements per band and bandwidth. For FR1 (sub-6 GHz): EIS around -95 to -110 dBm depending on bandwidth. For FR2 (mmWave): EIS around -85 to -95 dBm. Lower EIS = better sensitivity.