On the User Equipment Antenna Performance

In this paper the explicit (“obvious”) relation between mean effective gain of an antenna and its radiation efficiency has been pointed out. Introduction The user equipment (UE) is a vital element in UMTS networks which performance has a critical bearing on the overall system performance. In fact UE exhibiting poor performance will have a negative effect on the link quality, giving rise not only to isolated unsatisfied users but the performance of the whole network will be affected [1]. And the antenna is certainly one of the components of the UE. Measuring it performance has conventionally been focused on the antenna itself detached from the real context in which the UE is intended to work. However, it is well known that wireless communications takes place in highly multipath environments and close to the user’s body and surrounding objects, where the polarization and spatial distribution of the transmitted and received electromagnetic waves varies in space and time subjected to different propagation mechanisms that make the link communication quality very sensitive to these factors. A comprehensive measure of the antenna performance should therefore consider all those aspects as well. Hence, the better the antenna will “match” the spatial and polarization properties of the radio channel and lower the losses are the better will be the communication link quality and consequently, the more satisfied the users will be. Several parameters may be used to quantify the performance of UE with the antenna e.g. radiation efficiency, total radiated power (TRP), mean effective gain (MEG) and it variations. However, it seems that there is still little understanding about their relevance to the system performance and how they actually relate to each other. Therefore our aim is to provide a brief explanation of these figures of merit of the antenna performance in order to devise a reliable yet simple test method that ensures the quality of UE exposed to UMTS cellular networks. Antenna Efficiency (Radiation Efficiency or Total Radiated Power Gain) Antenna efficiency or radiation efficiency is defined as the ratio of the power radiated into space to the net power accepted from the connected transmitter [2], ( ) ( ) ( ) π φ θ φ θ φ θ 4 , , ∫ Ω + = = d G G P P e