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The contribution of this work is to propose a novel circulator design using the substrate‐integrated coaxial line (SICL) structure. Conventionally, the circulator is composed of three‐dimensional waveguide components, and, in contrast, the proposed SICL circulator allows the 3‐D waveguide circulator to be built in a planar form using the printed circuit board (PCB) technology. The proposed SICL circulator is composed of three substrates with two parallel signal strips embedded in the central SICL tunnel. For better impedance matching, a widened section is inserted in each uniform feedline, and the Y‐junction joint on the bottom surface of the middle substrate is connected with three stubs and is loaded with a circular disk on the top surface of the middle substrate. A bandpass filter (BPF) can be embedded in each circulator's branch to improve signal selectivity and the out‐of‐band isolation. Experiments are conducted to verify the circuit design. Agreements are observed between the measured and simulated data. [ABSTRACT FROM AUTHOR]

In this paper, a wideband directional coupler is proposed for high‐power applications, which is composed of a transformer and lumped elements. The introduction of the transformer greatly improves the directivity of the coupler. The measurement results demonstrate that the proposed design has an excellent return loss (>17 dB), small insertion loss (<0.4 dB), and high directivity (>22) over a wide frequency band (10–350 MHz). Meanwhile, it can achieve a flat coupling level of 32 dB with the imbalance less than 0.5 dB. [ABSTRACT FROM AUTHOR]

Two screen printing inks were developed for the low-temperature fabrication of printed and flexible thick film negative temperature coefficient thermistors able to operate at room temperature. The first of the two screen printing inks developed utilised cobalt ferrite (CoFe2O4) as the temperature sensing material with the second ink incorporating manganese ferrite (MnFe2O4). These were then screen printed onto lithographically printed silver interdigitated electrodes with a 200 µm track and gap using a synthetic paper (Teslin) as the substrate. The inks required a 10 min curing step at 80°C. Pre-annealing of the ferrite powders before ink formulation enabled the avoidance of high-temperature processing post-fabrication typically required in industrial thermistor production. The printed thermistors were tested at a controlled constant humidity between 15 and 50°C. Both materials demonstrated typical natural logarithmic responses with high linearity and sensitivity. [ABSTRACT FROM AUTHOR]

Easy‐to‐technology voltage‐controlled non‐reciprocal three‐layer ferrite/wire grating/varactor‐loaded copper strip metastructure of two configurations differing in layer arrangement is proposed and tested in external static magnetic field in a rectangular waveguide at 3–6 GHz. Retuning range with 20 dB isolation is 1.5 GHz, i.e. 35%. Propagation direction switching with 18 and 16 dB isolation is observed at fixed frequency; corresponding direct transmission values are −4 and −8 dB in the matching absence. [ABSTRACT FROM AUTHOR]

An optimised design of a radio frequency energy harvesting antenna is presented. The antenna is based on a compact ferrite rod which, together with the electronics, can directly replace batteries in suitable applications. The antenna is optimised such that the energy available for the applications is maximised, while considering constraints such as the device geometry and the Q‐factor. That the antenna can power a wireless sensor node is shown from the ambient medium wave transmissions. [ABSTRACT FROM AUTHOR]

DC–DC converting circuit with ferrite core inductor has many advantages in circuit design of implantable neurostimulation devices such as deep brain stimulation device. However, it may be problematic under MRI because of the saturation of the ferrite core of the inductor which would lead to dramatic decline of inductance. To address this issue, the influence of the ferrite core inductor saturation on the circuit functionality of the stimulator is systematically analysed. It was revealed that under proper conditions, it was possible to maintain the normal stimulation output even if the ferrite core saturated. The results were validated by simulation and experiment and the circuit design criteria were derived. [ABSTRACT FROM AUTHOR]