• Journal of Power Electronics
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• 제19권1호
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• pp.44-57
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• 2019

Recently, the use of LLCL filters for grid inverters has been suggested to give better harmonic attenuation than the commonly used L and LCL filters, particularly around the switching frequency. Nevertheless, this filter is mainly designed for constant switching frequency pulse width modulation (CSF PWM) methods. In variable switching frequency PWM (VSF PWM), the harmonic components are distributed across a wide frequency band which complicates the use of a high order filter, including LCL and LLCL filters. Recently, a confined band variable switching frequency (CB-VSF) PWM method has been proposed and demonstrated to be superior to the conventional constant switching frequency (CSF) PWM in terms of switching losses. However, the applicability of LLCL filters for this type of CB-VSF PWM has not been discussed. In this paper, the authors study the suitability of an LLCL filter for CB-VSF PWM and propose design guidelines for the filter parameters. Using simulation and experimental results, it is demonstrated that the effectiveness of an LLCL filter with CB-VSF PWM depends on the parameters of the filters as well as the designed variable frequency band of the PWM. Simulation results confirm the performance of the suggested LLCL design, which is further validated using a lab scale prototype.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제12권5호
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• pp.815-820
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• 2008

Recently the frequency assignment and the technical specifications of UWB systems for communications are completed. Therefore many UWB systems have been developed. In our country $3.1{\sim}4.8GHz$ and $7.2{\sim}10.2GHz$ are assigned for UWB systems for communications. When we consider RF technologies and the easy implementation of UWB systems, UWB systems used in the low band are more developed than high band systems. In this paper we design and implement a BPF for low band UWB systems by means of considering the easy implementation of UWB systems. The designed and implemented BPFs are low band filter and low band channel filters. The measured results of the low band filter show that the filter has 21.85dB and 17.91dB attenuation at 3.1GHz and 4.8GHz, 1.53GHz of -10dB bandwidth and 2dB of insertion loss. Low band can be divided into 3 channels with 500MHz of the channel bandwidth. The channel filter for channel number 1 has the characteristics of 24.85dB attenuation at 3.1GHz, 0.61GHz of -10dB bandwidth and 1.87dB of insertion loss. The filter for channel 3 in low band has 19.2dB of attenuation at 4.8GHz, 0.49GHz of -10dB bandwidth and 2.49dB of insertion loss.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제25권3호
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• pp.376-379
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• 2014

In this paper, we designed more improving a dual-band power amplifier than the transceiver of RFID reader that operates at 910 MHz and 2.45 GHz. A dual-band power amplifier has two circuits. One matching circuit is composed lumped element in the band of 910 MHz. The other matching circuit using distributed element in the high band of 2.45 GHz. So, this dual-band power amplifier works as Band Rejection Filter in the band of 910 MHz but in the high band of 2.45 GHz works as Band Pass Filter. Therefore, this is composed a microstrip transmission line. A power amplifier is showed gains of 8 dB output power at 910 MHz and 1.5 dB output power at 2.45 GHz. If input power is 10 dBm, both of bands output 20 dBm.

• The Journal of the Korea institute of electronic communication sciences
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• 제10권9호
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• pp.1033-1038
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• 2015

Complementary Filter is commonly used in signal processing method for real-time position measurement. Butterworth filter characteristic has a uniform gain in the pass band, the blocking band has a good blocking characteristics. Therefore, we propose a method of designing a complementary filter having a characteristic of Butterworth filter characteristic. By setting the appropriate filter coefficients in the simulation it appears to improve the performance of the filter. In the experiment it shows a real-time signal processing is possible by using the calculated filter coefficients in the simulation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• 제54권9호
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• pp.570-576
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• 2005

In FIR (Finite Impulse Response) filter applications, Nth-band FIR digital filters are known to be important due to their reduced computational requirements. The conventional methods for designing FIR filters use iterative approaches such as the well-known Parks-Mcclellan algorithm. the Parks-Mcclellan algorithm is also used to design Nth-band FIR digital filters. But a disadvantage of the Parks-McClellan algorithm Is that it needs a good amount of design time. This paper describes a direct design method for third-band FIR Filters using Chebyshev polynomial, which provide a reduction in design time over indirect methods such as the Parks-McClellan algorithm. The response of the resulting filter is equi-ripple in passband. The proposed method of design produces a passband response that is equi-ripple to within a minuscule error, compare to that of the Parks-McClellan algorithm.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• 제11권3호
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• pp.313-318
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• 2018

A coaxial band rejection filter is designed and fabricated for a beam interacting cavity. The proposed filter has a quarter wavelength choke for the dominant mode of the cavity. The equivalent circuit of the coaxial band rejection filter is presented and the ABCD parameter os each part is derived to obtain the ABCD parameter of the entire filter. The scattering matrix was obtained from the ABCD matrix and the was simulated by MATLAB using the obtained scattering matrix. The coaxial band rejection filter structure was simulated using HFSS, and the results confirmed the simulation using the equivalent circuit was useful. The designed coaxial band rejection filter was fabricated with 6-1/8 flange. The fabricated filter was measured using a transition from 6-1/8 flange to N-type flange. The insertion loss of the fabricated filter is greater than 25 dB in the dominant mode of the cavity and less than 0.25 dB in the first higher order mode. The measurement results are in good agreement with the simulated results and meet the design specification.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.193-196
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• 2000

A new type low-pass filter design method based on a coupled line and transmission line theory is proposed to suppress harmonics by attenuation poles in the stop band. The design formula are derived using the equivalent circuit of a coupled transmission line. The new low-pass filter structure is shown to have attractive properties such as compact size, wide stop band range and low insertion loss. The seventh-order low-pass filter designed by present method has a cutoff frequency of 0.9 CHz with a 0.01 dB ripple level. The coupled line type low-pass filter with strip line configuration was fabricated by using a high-temperature superconducting (HTS : YBa$_2$Cu$_3$O$_{7-{\delta}}$ thin film on MgO(100) substrate. Since the HTS coupled tine type low-pass filter was proposed with five attenuation poles in stop band such as 1.8, 2.5, 4, 5.5, 6.2 GHz. The fabricated low-pass filter has improved the attenuation characteristics up to seven times of the cutoff frequency.

• ETRI Journal
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• 제30권5호
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• pp.735-737
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• 2008

We propose a novel spatial multi-band-stop filter using modified multiple loop array elements to block electromagnetic waves or signals of mobile phones in public facilities. It operates at the following frequency bands: Korean cellular (824 MHz to 894 MHz), Personal Communication Service (PCS) (1.75 GHz to 1.87 GHz), and IMT-2000 (1.92 GHz to 2.17 GHz). Two frequency selective surfaces with modified multiple-loop elements are printed on the top and bottom of a pair-glass pane, which is a pair of glass panes with an air gap between them. A modified multiple-loop element with a meander line is used to make the size of the filter compact. The simulated and measured results show good agreement, which confirms the usefulness of the proposed tri-band spatial filter.

• Journal of the Korean Institute of Telematics and Electronics
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• 제25권7호
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• pp.826-835
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• 1988

In this paper, we analyze the generation of an image pyramid as a 2-dimensional decimation-interpolation process, and suggest a performance index of FIR filter for decimation and interpolation filter. Until now, most deciamtion and interpolation filters are designed via the approximation of the impulse response of an ideal filter. In this paper, however, we propose a new performance index that minimizes the maximum frequency-weighted mean square error between the desired and the generated interpolated signal, and propose an optimal half-band filter based on the proposed performance index as an example. Some simulation results with real images show that the proposed optimal half-band filter yields a higher PSNR as well as the more preferable image quality, in comparison with other currently used filters with the same computational complexity.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제11권8호
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• pp.1472-1477
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• 2007

Users are offered by the multimedia service of various information on current information-oriented society. The digitize became essential that process of various data is not to selected. Also, Filter technology is required to use the lacking frequency resources efficiently. This paper designs FIR digital band-pass filter of the voice band by narrow band pass filter md verify the characteristics of filter to use by the DSP practice SET.