The ADI-FDTD can be used for efficient and stable electromagnetic modeling of the VLSI circuit as the time step is not restricted by the CFL stability condition. However, when the Berenger's PML is implemented in the ADI-FDTD method, this scheme will lead to late-time instability. In this article, we propose the modified PML conductivity profile to improve the stability of the ADI-FDTD with PML absorber. The multilevel crossover in VLSI circuit and RF inductor are studied. Compared to the conventional FDTD simulation, a significant reduction in calculation time can be achieved. Although the PML performance will be affected by the modified PML conductivity profile, it can be found that the simulation results are matched quite well with the reference results. The modified scheme can provide an efficient and accurate electromagnetic simulation method for VLSI circuits.
Abstract-The frequency response characteristics of a basic microstrip lowpass filter improved using H-shaped defected ground structures are presented. The proposed defected ground structures behave as a resonant element at high frequency and thus eliminate the stopband frequencies to achieve wide stopband rejection. The 3 dB cutoff frequency of the filter is 1.935 GHz. Due to the defects etched in the ground plane of the basic structure, the harmonic rejection is improved from 5th to 10th order along with low insertion loss and voltage standing wave ratio together with good selectivity. The compact filter has a size of 0.0338λ 2 g , with λ g = 85.18 mm being the guided wavelength at the cutoff frequency. The characteristics of the lowpass filter are verified through simulation and measurement. Consistent and stable results are obtained.
A compact planar elliptic function lowpass filter with sharp roll-off at 20 dB attenuation level and wide stopband using microstrip stepped-impedance polygonal patch resonators is developed and investigated. Electromagnetic simulation is used to optimize the performance of the filter. The filter using cascaded multiple patch resonators provides a very sharp attenuation near cutoff frequency with a high stopband suppression level. The rejection bandwidth is enhanced by introducing additional transmission zeroes and the results are validated by the experiment. The filter has a compact size of 17.6 mm 3 12.2 mm. V C 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:133-136, 2016; View this article online at wileyonlinelibrary.com.
for both TE and TM polarization provides very stable resonant frequency, that is, 8.8 GHz. For TE and TM mode of normal incidence, the results showed that measured 210 dB bandwidth for 90% power absorption and 220 dB bandwidth for 99% are 2.08 and 0.6 GHz at the resonant frequency, respectively. Additionally, the measured result shows good agreement with those of the simulated one. The results implicitly mean that the proposed design holds a highly stable frequency response for oblique angular incidence for both TE and TM modes of polarization.
CONCLUSIONIn this letter, we proposed and fabricated the transparent EM absorber with frequency selective pattern as a circuit analogue, which has the frequency stability for different incidence angles and polarizations and wide absorption bandwidth. Simulation was performed using commercial EM software to obtain the reflection loss of the structure and then the measurement results of the fabricated one were compared. It was observed that the design provides stable absorbing characteristics for polarization and different angles of incidence as well as wide absorption bandwidth as expected.
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