Direct Measurement of Small Antenna Radiation Efficiency by Calorimetric Method

Abstract

A novel method for radiation efficiency measurement of small-size radiators such as mobile phones and other handheld wireless devices is presented. The method is based on the accurate determination of the power which is dissipated in the antenna under test using a calorimetric approach. The principle of the method, some of its variants, and the experimental setup are described. Application of the method is demonstrated for several test objects with different efficiencies. Accuracy is validated by comparison of calorimetric radiation efficiency against numerical estimates and independent measurements using the reflection efficiency method, a generalized variant of the Wheeler cap method, whose basic limitations are briefly discussed. Due to the calorimetric principle employed in the proposed new method, it qualifies equally well as a highly accurate reference method for radiation efficiency measurements and as a low-cost alternative to three-dimensional pattern integration and Wheeler cap type efficiency estimates.

An Envelope Correlation Formula for(N,N)MIMO Antenna Arrays Using Input Scattering Parameters, and Including Power Losses

“…The results have shown close agreement between this method and the full computation using the far field pattern data. Several practical methods exist, for example, radiometer [20,21], random field [22], and reverberation chamber [23], for direct measurement of the radiation efficiency of passive International Journal of Antennas and Propagation 7 antennas. These can be used for multiport structures and can provide independent checks of the diagonal terms in (12).…”

Design of Cavity-Backed Bow-Tie Antenna with Matching Layer for Human Body Application

“…There was a somewhat large discrepancy between the simulation and measurement of the radiation efficiency. It is known that the numerical simulation often over-estimates the radiation efficiency [20,21]. The radiation efficiency in the measurement was obtained from the relationship between the gain and directivity, whereas the simulated one was based on the ratio of the total radiated power to the accepted power by the antenna.…”

Input impedance measurements of cell phone antennas using backscattering modulation

“…The antenna isolated from its environment behaves in a different way due to current interaction with cell phone casing or due to the presence of other materials (as substrates or the human body). An important effort has been done on the characterization of radiation characteristics (efficiency, radiation pattern and Total Radiated Power) of cell phones under realistic operational situations using an anechoic chamber [1], a reverberation chamber [2] or by calorimetric method [3], but there is not a similar work on the correct characterization of its input impedance using indirect Sparameters measurements. In this way it will be suitable to use a measurement procedure able to be integrated in the antenna structure having as a goal to be able to measure the antenna input impedance under its final conditions.…”