• Journal of Navigation and Port Research
• /
• v.30 no.7
• /
• pp.607-610
• /
• 2006

A new compact microstrip low-pass filter and its equivalent-circuit model are developed. The philosophy of the structure behind this novel microstrip low-pass filter is simple as it is composed of a pair of symmetrical parallel coupled-line and an open-stub. With this configuration, a finite attenuation pole near the stopband cutoff frequency is available and adjustable by simply tuning the circuit parameters. Furthermore, the rejection bandwidth of this type of low-pass filter can be extended. In order to validate the feasibility of the proposed design method, a low-pass filter based on a microstrip structure is designed, fabricated, and measured. Experimental results agree very well with the simulation and analytical results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.12
• /
• pp.1333-1338
• /
• 2008

In this paper, RF varactor diode are applied to the design of miniaturized and tunable bandstop filter. The proposed bandstop filter is based on a Defected Ground Structure(DGS) section topology. The designed tunable bandstop filter can achieve a significant size reduction by with loading capacitance component of varactor diode. It is observed from the measured results that the proposed tunable bandstop filter shows a wide tuning range of 42.9 % from 1.01 GHz to 1.99 GHz. The rejection level in the stopband is higher as the number of DGS section increases. In case of the proposed tunable bandstop filter with two DGS sections, the rejection level of the filter is better than 20 dB in the stopband during the tuning. In this case, the maximum insertion loss in the lower passband is 0.5 dB.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.2C
• /
• pp.213-221
• /
• 2004

A new method for design of two-channel finite-impulse response(FIR) quadrature mirror-image filter(QMF) banks with low reconstruction delay using weighting function is proposed. The weighting function used in this paper is calculated from the previous updated filter coefficients vector which is adjusted from iteration to iteration in the design of QMF banks. In this paper, passband and stopband edge frequency are used in design of QMF banks with low delay characteristic in time domain instead of specific frequency interval where the artifacts occur in conventional design method. The investigation of specific frequency interval where artifacts occur can not be required by using passband and stopband edge frequency. Some comparisons of performance are made with other existing design method to demonstrate the proposed method for QMF bank design. and it was observed that the proposed method using the weighted function and passband and stopband edge frequency improves the peak reconstruction error by 0.001 [dB], the peak-to-peak passband ripple by 0.003[dB], SNR with a white noise by 7[dB] and SNR with a step input by 32[dB], but with a reduction of the computational efficiency because of updating the weighting function over the conventional method in Ref [11].

• The Journal of the Acoustical Society of Korea
• /
• v.19 no.5
• /
• pp.79-83
• /
• 2000

When passband ripple α/sub p/ and stopband attenuation α/sub s/ at the w/sub s/ where the stopband begins are specified in filter design, △α/sub s/ usually exceeds the specification by △α/sub s/ due to the necessity that the order n of the filter function be an integer. In this paper, we apply a trade-off method to remove the excess stopband attenuation △α/sub s/ for reducing the value of pole-Q and improving the characteristics of the Chebyshev filter function. We also apply the trade-off method of pole-Q reduction to the modified Chebyshev function, and then the 4 types of function have been analyzed to compare in frequency and time domain characteristics. The trade-off method reduces the pole-Q which influences the filter characteristics to maximum 49.6% without increase of the order n. Thus implies that they have the improved characteristics such as the reduced passband ripple and flatter delay characteristics as compared Chebyshev filter function before trade-off. And the unit step response shows shorter delay time and settling time in time domain performance.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.11 no.4
• /
• pp.1-8
• /
• 2011

In this paper, a microstrip bandpass filter(BPF) with 3 dB bandwidth of more than 50 % at center frequency of 30 GHz was implemented. The implemented BPF is to be used as ASK(Amplitude Shift Keying) transmission and reception filters in IF band for THz transmitter and receiver capable of 10 Gb/s wireless data transmission. The microstrip BPF with ultra-wideband characteristics was implemented using a stepped-impedance lowpass filter(LPF) and a composite quarter-wave short stubs where the LPF is functioning as attenuating the upper stopband and quarter-wave short stubs is functioning as attenuating the lower stopband. The measured results are as follows; the insertion loss is 0.65 dB at 30 GHz, the stopband characteristics are -10 dB and -16 dB at 10 GHz and 50 GHz, respectively, and the passband flatness is ${\pm}0.5$ dB at 20~40 GHz.

• Journal of Navigation and Port Research
• /
• v.30 no.5 s.111
• /
• pp.331-334
• /
• 2006

In this paper, we designed and fabricated the lowpass filter with the wide stopband characteristics using microp- strip line. Adding the $\lambda_g/4$ open stub at the input and output ports, we developed the L-C ladder type lowpass filter using the open stub which has wide stopband characteristics. In order to reduce the entire size qf this filter, the high impedance microstrip lines were made with the meander structure. The lowpass filter was fabricated with the cutoff frequency 2.3 GHz and its measured frequency responses agree well with the simulation results.

• Proceedings of the Optical Society of Korea Conference
• /
• 1990.02a
• /
• pp.252-256
• /
• 1990

In this paper, we proposed E-plane structures to obtain the high insertion loss at stopband and show that T-equivalent and K-inverter of Triple E-plane structures are better than those of All-Metal Insert E-plane structures. To show the characteristics first order bandpass filter are designed and tested at X band.

• Journal of electromagnetic engineering and science
• /
• v.1 no.2
• /
• pp.156-160
• /
• 2001

Very convenient equivalent circuits fur the design of bandpass filters with an attenuation pole in the lower or upper stopband are provided together with necessary closed-form solutions. The proposed approach gives us much flexibility and simplifies the design of inserting attenuation poles.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.44 no.3
• /
• pp.105-112
• /
• 2007

In general, the earlier methods for the design of MAXFLAT FIR filters have existent problems due to the approximation algorithms used to approach MAXFLAT(maximally flat) response in the passband and the stopband.. The proposed approach advanced by using of MAXSHCUT(maximally sharp cutoff) condition in this paper clearly overcomes these problems. In this approach, we use a key parameter represented with filter-order and cutoff-frequency parameters for obtaining the lowpass filters with the MAXFLAT and MAXSHCUT characteristics in the frequency domain. Consequently, this design technique leads to new MAXFLAT and MAXSHCUT FIR digital filter, which can achieve sharp-cutoff responses with the stopband attenuation exceeding 100 dB almost everywhere.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.2
• /
• pp.653-658
• /
• 2015

This paper deals with an efficient optimization design method of a compact ultra wideband (UWB) filter which can improve the characteristics of the filter. The Evolution Strategy (ES) algorithm is adopted for the optimization and modified to suppress the ripple by inserting an additional step to the ES scheme. The algorithm has the ability to control the ripple of an insertion loss in a passband as a modified approach. During the modified ES, a structure of initial shape is changed a lot, while includes the stepped impedance (SI) and the composite right/left handed transmission line (CRLH-TL). And an optimized filter satisfies the UWB specifications on the stopband and passband with an acceptable insertion loss. The filter achieves a much developed shape, the size of $15{\times}14mm$, the 3dB bandwidth from 2.7 to 10.8GHz, the flat insertion-loss less than 1dB, the wide stopband with 12~20GHz, and an acceptable return loss.