WuSeong Lee

A dual-band bandpass filter using a dual-mode ring resonator with two short-circuited stubs

In this paper, a high selective dual-band bandpass filter using a dual-mode ring resonator with angle perturbation and two short-circuited stubs is proposed. For dual-mode resonance, the ring resonator is directly connected with nonorthogonal feed-line via coupling capacitors. And two different short-circuited stubs are simultaneously placed at two corners along the symmetric plane of the ring resonator. These two stubs make it possible to provide a transmission zero near the lower second passband edge. The proposed dual-band filter was fabricated. As a result of measurement, it exhibits center frequency (fractional bandwidth) of 2.3 (15.8%) and 4.9 GHz (25.7%) with insertion loss of 0.74 dB and 0.56 dB, respectively. So, the proposed filter has attractive features of low insertion loss and wide bandwidth compared to other dual-band filters. Thus, it should be well suited not only for wideband WLAN applications but also for any other communication systems.

Reduction of Numerical Dispersion Error in 3-D ADI-MRTD Method With the Coarse Mesh

In order to reduce the numerical dispersion in three-dimensional alternating-direction implicit multiresolution time-domain scheme, a correction procedure is introduced. The numerical dispersion relation and the anisotropic correction parameters are considered. The reduction of the numerical dispersion is investigated for single frequency problem and wide-band simulation with the coarse mesh.

An Improved Split-Step Method in Scaling Function Based MRTD

A split-step method with four sub-steps is applied to the multiresolution time-domain scheme and combined with the dispersion-error control parameters. From the discussed numerical dispersion, it is obvious that the phase velocity an- isotropic error and absolute error of the introduced method are much lower than alternating direction implicit and the original split-step MRTD method. The results show that this method can use three times the time step of the original SS-MRTD method.

A compact and wide stop-band low-pass filter using a wire wound chip-inductor

In this paper, an elliptic-function low-pass filter using a wire wound chip inductor is proposed. To reduce the filter size and to realize the sharp roll-off skirt characteristic, the wire wound chip inductor, which has the large inductance with small size, is employed. The proposed low-pass filter has wide stop-band with three attenuation poles. The two of them are generated by the gap capacitance of the symmetrical open ended stubs, and the other is created by self resonant frequency of the wire wound chip inductor. The three attenuation poles are designed to suppress 2nd, 3rd, and 4th harmonics. The fabricated LPF exhibits 3-dB cutoff frequency of 930 MHz, insertion loss below 0.07 dB and stop-band from 1.48 to 9.10 GHz below the rejection level of 20 dB.

A Three-Dimensional Locally One-Dimensional Multiresolution Time-Domain Method Using Daubechies Scaling Function

A three-dimensional locally one-dimensional multiresolution time-domain(LOD-MRTD) method is introduced and unconditional stability is proved analytically. The updating formulations have fewer terms on the right-hand side than those of an alternating direction implicit MRTD(ADI-MRTD). The validation of the method is presented using the resonance frequency problem of an empty cavity. The reduction of the numerical dispersion technique is also combined with the proposed method. The numerical examples show that the combined method can improve the accuracy significantly.

Analysis of Periodic Stepped Impedance Ring Resonator by the Effect of Step Perturbation and Application of Dual-Mode Bandpass Filter

Dual-mode bandpass filter was designed by using periodic stepped impedance ring resonator with step perturbation. The periodic stepped impedance ring resonator has the effects of size reduction and harmonic suppression by changing characteristic impedance ratio. The perturbation for dual-mode generation was also easily controlled by characteristic impedance ratio, and the variation of dual-mode resonant frequencies and attenuation pole frequencies were analyzed by the effect of step perturbation. Chip capacitors were used for input/output coupling, and the variation of center frequency by the coupling capacitance and step perturbation was also considered. From the results, two types of 2 GHz dual-mode bandpass filter were fabricated in size of , those have different attenuation poles and bandwidths. The measured results of proposed bandpass filters showed a good agreement with the calculated estimations, and those have insertion loss of 2.52, 0.52 dB and 3 dB bandwidth of 4.03, 15.02 %, respectively.

Time Domain Scheme Based on Positive Sampling Basis Associated with Coifman Scaling Function

In order to simplify the Coifman scaling function based S-MRTD scheme for electromagnetic field problems, we develop the update formulations based on the positive sampling basis. We show the approximate interpolation property of the positive sampling basis associated with Coifman scaling function exactly. That makes the implementation of boundary condition, inhomogeneous media interface, and the total field computation simple. Actually the time domain scheme introduced in this paper has the merits of Coifman scaling function based S-MRTD and is simpler to formulate than S-MRTD. The some numerical results are provided to validate this work. The numerical results also validate the sampling property of Coifman scaling function.