Steady-state (SRMC) and time-resolved microwave photoconductivity (TRMC) are key techniques used to perform the contact-less determination of carrier density, transport, trapping, and recombination parameters in charge transport materials such as organic semiconductors and dyes, inorganic semiconductors, and metal−insulator composites, which find use in conductive inks, thin film transistors, lightemitting diodes, photocatalysts, and photovoltaics. We present the theory, design, simulation, and fabrication of a planar microwave ring resonator operating at 5.25 GHz with a quality factor of 224, to perform SRMC and TRMC measurements. Our method consists of measuring the resonance frequency (f 0 ) and Q-factor of the microwave resonator with the sample to be probed placed in a defined sensitive region of the resonator where the microwave field is highly concentrated. We also provide proof of concept measurements of the time-resolved microwave photoresponse of anatase-phase TiO 2 nanotube array membranes (TNTAMs) using the planar microstrip resonator. An unusual observation was the persistence of charged pair states in TNTAMs for several hours at room temperature under ambient conditions. Fast (120−220 s), slow (1300−2850 s), and very slow (6−26 h) components were extracted from the long-lived photoconductive decays of TNTAMs in response to 365, 250, and 405 nm illumination and assigned to various trap-mediated processes in TiO 2 nanotubes.

A novel approach with a new configuration is introduced to design an ultra-wideband (UWB) band-pass filter (BPF) that demonstrates double/single notch-bands using micro-strip transmission lines without using any via-hole. The proposed approach is established using two parallel stepped-impedance resonators (SIR) that provide two paths with different electrical lengths. The mechanism of realising notch-bands within the pass-band of the UWB BPF is developed based on the waves' cancellation theory. To realise single or double notch-bands (DNBs) within the pass-band of a UWB BPF, the conventional tri-section stepped-impedance resonator (TSSIR) is adopted and its fundamental and first spurious resonance frequencies are chosen either to be suppressed or supported. New parallel dual-section T-shaped and TSSIRs are proposed, optimised and fabricated to provide single and DNBss, respectively. The proposed concept avoids using via holes, which is conventionally used in notch filters. In addition, a size reduction of about 75% is reported in comparison with the conventional BPF with a single notch-band accompanied by two transmission zeroes at the lower and upper stop-bands. Moreover, our proposed DNBs BPF demonstrates a comparable performance while being smaller in size (up to a 12.6% size reduction) to that of the latest UWB BPF design that used complicated and expensive multilayer liquid crystal polymer (LCP) technology.

No abstract

No abstract

After analyzing MDA current distributions, it is observed that those along the meander parallel conductors basically do not exhibit a 180°diphase. Furthermore, MDA collinear elements can be described as transmission lines with variable characteristic impedance. Thus, a full TLM reformulation can be performed to model the voltage at MDA feed and calculate its resonant frequency. The equation provided involves all the geometrical antenna parameters. Therefore, either a synthesis of a MDA from its resonance frequency or MDA analysis for resonance estimation can be performed. The relative error falls below 7.8% in the prototypes under study. The MDA resonant frequency reduction factor can be estimated from the model mainly by the number of meanders without the need for simulations. It is demonstrated that further predictable antenna tuning can be achieved either by meander dimension adjusting or by meander drifting along the MDA, which cannot be explained by other models in the literature. Furthermore, the model shows that meanders closer to antenna edges are more size-reduction efficient than those closer to the antenna feed. Therefore, it makes MDA be more easily matched to compact and low profile application circuits.