In this letter, a dual‐wideband band pass filter (DW‐BPF) using cross‐stub stepped impedance resonator (CS‐SIR) was simulated, fabricated, and measured accordingly. The CS‐SIR was used to replace the conventional half‐wavelength open stub resonators. Compare to the conventional resonator, the CS‐SIR resonator has a wider fractional bandwidth and ease of fabrication. Furthermore, the DB‐BPF was fabricated on microstrip with ɛr = 4.4, h = 0.8 mm, and tan δ = 0.0265. The DW‐BPF with CS‐SIR achieves transmission‐coefficients/fractional‐bandwidth of 0.22 dB/94.19% and 1.87 dB/33.52% at 1.14 GHz and 2.31 GHz, respectively. In order to reduce the filter size, a folded CS‐SIR (FCS‐SIR) was also proposed. As a result, this BPF size was reduced to 53%, with the BPF size of 0.30 λG2 and 0.14 λG2 for DW‐BPF with CS‐SIR and DW‐BPF with folded CS‐SIR, respectively. The λG is the wavelength at the first frequency. Further, the DW‐BPF with FCS‐SIR achieves transmission coefficients/fractional bandwidth of 0.19 dB/89.08% and 1.29 dB/31.90% at 1.21 GHz and 2.41 GHz, respectively. Measured results are in a very good agreement with the simulated results.
A bandpass filter based on square open loop resonator is designed at 2.45 GHz. To enhance the filter selectivity around the pass band two transmission zeros are introduced and also additional tranmission zeros inserted apart from the pass and to guarantee the rej ection there. This six pole filter with four transmission zeros is implemented in microstrip technology. The simulation and measurement results show a very well reflection characteristics, whereas they show relative big insertion loss of about 3.6 dB in simulation and 6.3 dB in measurement. The bandwidth obtained by simulation and measurement is about 72 to 86 MHz. Moreover we see a shift of measurement againts the simulation result, which probably due to mechanical tolerances and tolerances of the relative permittivity of the subtsrate used.
A hepta-band bandpass filter (HB-BPF) based on folded cross-loaded stepped impedance resonator (SIR) was investigated. A cross-loaded SIR microstrip structure was arranged to produce several transmission zeros. In order to reduce the filter size, a folded cross-loaded SIR was proposed. The HB-BPF was designed on FR4 microstrip substrate with ε r = 4.4, thickness h = 0.8 mm, and tan δ = 0.0265. This HB-BPF achieves transmission coefficients of 0.
Experiments with pulsed radio frequency fields have shown influence on the low-frequency behavior of lipid bilayer membranes. In this paper, we present an electromagnetic and thermal analysis of the used exposure device to clarify whether the observed effects have a thermal cause and to determine the fields at the lipid bilayer. In order to model the very thin lipid bilayer (about 5 nm) accurately, the electromagnetic analysis is broken into several steps employing the finite difference time domain technique and a finite element/boundary element hybrid approach. Based on the obtained power loss due to the electromagnetic fields, the temperature change is calculated using the finite element method for the solution of the heat conduction equation. Both, the electromagnetic and the thermal analysis are performed for a variety of material parameters of the exposure device. The electromagnetic analysis shows that the exposure device is capable of producing voltages on the order of 1 mV across the lipid bilayer. The combined electromagnetic and thermal calculations reveal that the temperature oscillations due to the pulsed radio frequency fields are too small to directly influence the low-frequency behavior of the lipid bilayer.
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