Clutter Effect Investigation on Co-Polarized Chipless RFID Tags and Mitigation Using Cross-Polarized Tags, Analytical Model, Simulation, and Measurement.

Chipless radio frequency identification (RFID) technology is expected to replace barcode technology due to its ability to read in non-line-of-sight (NLOS) situations, long reading range, and low cost. Currently, there is extensive research being conducted on frequency-coded (FC) co-polarized radar cross-section (RCS)-based tags, which are widely used. However, detecting co-polarized chipless RFID tags in cluttered environments is still a challenge, as confirmed by measuring two co-polarized tags in front of a perfect metal reflector (30.

Indoor Large-Scale MIMO-Based RSSI Localization with Low-Complexity RFID Infrastructure.

Indoor localization based on unsynchronized, low-complexity, passive radio frequency identification (RFID) using the received signal strength indicator (RSSI) has a wide potential for a variety of internet of things (IoTs) applications due to their energy-harvesting capabilities and low complexity. However, conventional RSSI-based algorithms present inaccurate ranging, especially in indoor environments, mainly because of the multipath randomness effect. In this work, we propose RSSI-based localization with low-complexity, passive RFID infrastructure utilizing the potential benefits of large-scale MIMO technology operated in the millimeter-wave band, which offers channel hardening, in order to alleviate the effect of small-scale fading.

A 32-channel parallel transmit system add-on for 7T MRI.

Purpose: A 32-channel parallel transmit (pTx) add-on for 7 Tesla whole-body imaging is presented. First results are shown for phantom and in-vivo imaging.

Methods: The add-on system consists of a large number of hardware components, including modulators, amplifiers, SAR supervision, peripheral devices, a control computer, and an integrated 32-channel transmit/receive body array.

Field Distribution and Coupling Investigation of an Eight-Channel RF Coil Consisting of Different Dipole Coil Elements for 7 T MRI.

In this contribution, we investigate the [Formula: see text] distribution and coupling characteristics of a multichannel radio frequency (RF) coil consisting of different dipole coil elements for 7 T MRI, and explore the feasibility to achieve a compromise between field distribution and decoupling by combining different coil elements. Two types of dipole elements are considered here: the meander dipole element with a chip-capacitor-based connection to the RF shield which achieves a sufficient decoupling between the neighboring elements; and the open-ended meander dipole element which exhibits a broader magnetic field distribution. By nesting the open-ended dipole elements in between the ones with end-capacitors, the [Formula: see text] distribution, in terms of field penetration depth and homogeneity, is improved in comparison to the dipole coil consisting only of the elements with end-capacitors, and at the same time, the adjacent elements are less coupled to each other in comparison to the dipole coil consisting only of the open-ended elements.

Mitigation of B1(+) inhomogeneity on single-channel transmit systems with TIAMO.

In magnetic resonance imaging, there has been a constant drive to higher static magnetic field strengths (B0) to achieve a higher signal-to-noise ratio and new or enhanced contrasts. In today's high-field systems, severe problems regarding the homogeneity of the transmission field are encountered. Recently, an acquisition scheme called Time-Interleaved Acquisition of Modes has been proposed to tackle the inhomogeneity problems in high-field magnetic resonance imaging.

Variable power combiner for RF mode shimming in 7-T MR imaging.

This contribution discusses the utilization of RF power in an MRI system with RF mode shimming which enables the superposition of circularly polarized modes of a transmit RF coil array driven by a Butler matrix. Since the required power for the individual modes can vary widely, mode-shimming can result in a significant underutilization of the total available RF power. A variable power combiner (VPC) is proposed to improve the power utilization: it can be realized as a reconfiguration of the MRI transmit system by the inclusion of one additional matrix network which receives the power from all transmit amplifiers at its input ports and provides any desired (combined) power distribution at its output ports by controlling the phase and amplitude of the amplifiers' input signals.

Microstrip Butler matrix design and realization for 7 T MRI.

This article presents the design and realization of 8 × 8 and 16 × 16 Butler matrices for 7 T MRI systems. With the focus on low insertion loss and high amplitude/phase accuracy, the microstrip line integration technology (microwave-integrated circuit) was chosen for the realization. Laminate material of high permittivity (ε(r) = 11) and large thickness (h = 3.