RESUMEN
The effect of a user's proximity on wireless device performance is critical to test the device under realistic conditions. In this work, we propose and demonstrate an improved uncertainty estimation method for antenna efficiency measurements in a reverberation chamber. The improved method separately computes uncertainties due to the effects of chamber loading by a phantom and the effects of antenna mismatch introduced by this phantom, illustrating the sensitivity of uncertainty to close-proximity user effects. We demonstrate that, while the impact of the phantom may be significant on antenna efficiency, and, it has some influence on the uncertainty in the measurement, its impact on overall uncertainty may be insignificant. This is demonstrated using the two-antenna method in the presence of a phantom close to the antenna under test. We illustrate the method by summarizing the antenna efficiencies with their uncertainties and the impact of the phantom for important communication bands. Due to the large effect of the user on antenna performance, this type of measurement and its uncertainty evaluation is a valuable way to characterize antenna efficiency including user effects.
RESUMEN
Beyond fifth generation (5G) communication systems aim towards data rates in the tera bits per second range, with improved and flexible coverage options, introducing many new technological challenges in the fields of network architecture, signal pro- cessing, and radio frequency front-ends. One option is to move towards cell-free, or distributed massive Multiple-Input Multiple-Output (MIMO) network architectures and highly integrated front-end solutions. This paper presents an outlook on be- yond 5G distributed massive MIMO communication systems, the signal processing, characterisation and simulation challenges, and an overview of the state of the art in millimetre wave antennas and electronics.
RESUMEN
Biological studies and clinical trials show that addition of hyperthermia stimulates conventional cancer treatment modalities and significantly improves treatment outcome. This supra-additive stimulation can be optimized by adaptive hyperthermia to counteract strong and dynamic thermoregulation. The only clinically proven method for the 3D non-invasive temperature monitoring required is by magnetic resonance (MR) temperature imaging, but the currently available set of MR compatible hyperthermia applicators lack the degree of heat control required. In this work, we present the design and validation of a high-frequency (433 MHz ISM band) printed circuit board antenna with a very low MR-footprint. This design is ideally suited for use in a range of hyperthermia applicator configurations. Experiments emulating the clinical situation show excellent matching properties of the antenna over a 7.2% bandwidth (S 11 < -15 dB). Its strongly directional radiation properties minimize inter-element coupling for typical array configurations (S 21 < -23 dB). MR imaging distortion by the antenna was found negligible and MR temperature imaging in a homogeneous muscle phantom was highly correlated with gold-standard probe measurements (root mean square error: RMSE = 0.51 °C and R 2 = 0.99). This work paves the way for tailored MR imaging guided hyperthermia devices ranging from single antenna or incoherent antenna-arrays, to real-time adaptive hyperthermia with phased-arrays.