What is Total Isotropic Sensitivity (TIS)?

Total Isotropic Sensitivity (TIS) is the average sensitivity of a receiving antenna or system when measured across 3-dimensional space. TIS is usually measured in an antenna test range or anechoic chamber. It is calculated by measuring the receive sensitivity of the system over all possible angles, directions and both vertical & horizontal polarizations. The measured sensitivity over each angle is called the effective isotropic power (EIS) of the antenna in that direction. All of these EIS values are measured over many angles and the average is calculated. As a result, TIS is a spherical or 3D measurement that is expressed in terms of Watts (W) or dBm (on a logarithmic scale).

TIS is not only measured for the antenna but the receiver and antenna system as a whole. It is dependent on the receiver’s sensitivity (without the antenna), the antenna and its efficiency and various self-interference factors.

TIS would be equal to the receiver’s sensitivity if an isotropic (ideal) antenna is used, but when using a real antenna the TIS is less than the receiver’s sensitivity depending on the antenna efficiency. Hence, TIS expresses the actual receiver sensitivity of the device under working conditions and is a more reliable parameter to compare RF devices and circuitry.

TIS is the measured sensitivity of the complete receiving system. This makes it a characteristic of not only the antenna but also the receiver and the connection between the receiver and the antenna. Since most wireless devices use the same antenna for both transmitting and receiving, self-interference factors can cause the overall receiver sensitivity to reduce. These type of factors are included in to the calculation of the Total Isotropic Sensitivity (TIS).

The measurement of TIS is has been standardized for cellular/mobile and WLAN transmitters by CTIA Certification, a division of CTIA - The Wireless Association.  For this reason, most receiver systems, especially cellular devices have their TIS values specified rather than antenna efficiency.