• Journal of electromagnetic engineering and science
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• v.4 no.3
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• pp.113-118
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• 2004

As an application of ring filters, a new and simple method to determine an inherent-ring-resonance frequency is introduced. The ring filter consists of a ring and two short stubs. They are connected at 90$^{\circ}$ and 270$^{\circ}$ points of the ring and the ring filter may be seen in such way that two filters are connected in parallel. Therefore, if the two powers of the two filters are out-of-phase at the output, the power excited at the input can not be delivered. That can be done by making difference in length of the two short stubs, and when a certain condition is satisfied, a frequency exists where all the excited power is reflected. That is the very inherent-ring-resonance frequency. In the lossless case, the return loss with the condition reaches 0 dB at the inherent-ring-resonance frequency but does not with conductor, dielectric losses and so on. Therefore, the effective loss tangent at a frequency of interest may be obtained correctly. To verify the method, two ring filters have been fabricated in microstrip lines and the measured results show good agreement with the predicted ones.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1549-1551
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• 1998

We have designed and developed narrow bandpass multipole filters for satellite communication using $YBa_2Cu_3O_{7-x}$(YBCO) thin films on MgO substrates. The superconducting film used in this study was prepared by laser ablation on one side polished MgO (100) substrates. A Nd:YAG laser was used to fabricate YBCO thin films. The wave length of the laser was 355 nm. The laser beam was focused onto a YBCO target rotating linearly to avoid deep craters that may eject macroscopic YBCO particles. The YBCO films were grown at $750^{\circ}C$ in the oxygen partial pressure of 200 mTorr. The deposited YBCO thin films were patterned by conventional wet-etching method. The transition temperatures of YBCO thin films were 85 - 88 K and the film thicknesses were about 5,000 $\AA$. By comparing the performances of normal-metal filters and YBCO filters, we observed that superconducting YBCO multipole filters have been showed superior performances at 77 K.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.819-826
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• 2002

In this paper, the performance of Au / $Ba_{0.5}Sr_{0.5}TiO_3$ (BST) / Magnesium oxide (MgO) two-layered electrically tunable band-pass Filters (BPFs) is demonstrated. The devices consist of microstrip, coplanar waveguide (CPW), and conductor-backed coplanar waveguide (CBCPW) structures. These BST thin film band-pass filters have been designed by the 2.5 D field simulator, IE3D, Zeland Inc., and fabricated by thin film process. The simulation results, using the 2-pole microstrip, CPW, and CBCPW band-pass filters, show the center frequencies of 5.89 GHz, 5.88 GHz, and 5.69 GHz, and the corresponding insertion losses are 2.67 dB, 1.14 dB, and 1.60 dB, with 3 %, 9 %, and 7 % bandwidth, respectively. The measurement results show the center frequencies of 6.4 GHz, 6.14 GHz, and 6.04 GHz, and their corresponding insertion losses are 6 dB, 4.41 dB, and 5.41 dB, respectively, without any bias voltage. With the bias voltage of 40 V, the center frequencies for the band-pass filters are measured to be 6.61 GHz, 6.31 GHz, and 6.21 GHz, and their insertion losses are observed to be 7.33 dB, 5.83 dB, and 6.83 dB, respectively. From the experiment, the tuning range for the band-pass filters are determined as about 3 % ~ 8 %.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.5
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• pp.442-451
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• 1997

We described a miniaturization of microstrip filters by the exact synthesis. With the exact synthesis, we can design completely new circuits physically realizable. The complex procedure for the network synthesis could be reduced by using computer software. It is a new design procedure ensuring the creation of optimum networks which have minimum number of elements. The exact synthesis gives more possibilities to make wideband filters which require bandwidth of 50~100 %. S-plane Bandpass prototypes are made with non-redundant filter synthesis technique that has transmission zero locations at required frequencies. Because this method uses the transmission lines which lengths are ${\lambda}$/4 at the stopband center frequency, we can reduce the size of the filter dramatically.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.7
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• pp.1255-1260
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• 2009

Microstrip interdigital filter is designed with the width and length of a resonator, the gap distance between resonators and the location of a tap. When designing filters, it is a benefit to design with few design parameters comparing to many design parameters. In this paper we design and implement two microstrip interdigital filters operating in the UWB(Ultra Wide-Band) frequency band, one using a fixed width of a resonator and the other using a different width of resonators. The test results of the implemented filters show that the low-band high filter with a fixed width has the insertion loss of 1.49dB, -10dB band width of 720MHz, -35.7dBattenuation at 4.8GHzand below -13dB of S11. The filter with a different width of resonators has the insertion loss of 1.6dB, -10dBbandwidth of 1.63GHz and below-8dBof S11.

• Progress in Superconductivity
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• v.4 no.2
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• pp.132-136
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• 2003

Extremely selective high temperature superconducting (HTS) band -pass filters were developed for the base transceiver station applications of Digital Cellular communication Service (DCS). The filters have a bandwidth of 25 MHz at a center frequency of 834 MHz. There are 12 resonators which have spiral-meander microstrip-line structures in order to reduce far-field radiations with a reasonable tunability. As a result, the size of filters is 5 mm $\times$ 17 mm $\times$ 41 mm. Device characteristics exhibited a low insertion loss of -0.4 dB with a -0.2 dB ripple and a return loss better than -10 dB in the pass-band at 65 K. The out-of-band signals were attenuated better than 60 dB about 3.5 MHz from the lower band edge, and 3.8 MHz from the higher band edge.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.697-706
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• 2000

In this paper, new bandpass filters that are composed of microstrip ring resonators with the center frequency of 5.775 GHz and the bandwidth of 100 MHz are presented. For the suppression of the unnecessary harmonics, lowpass filters are inserted into the feedlines and ring resonator itself, respectively These bandpass filters show good microwave characteristics with the harmonic suppression ratio of about 39 dB and 35 dB, respectively. Also, the varactor-tuned microstip ring bandpass filter with harmonic suppression is suggested and the tuning bandwidth of more than 450 MHz is obtained.

• ETRI Journal
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• v.29 no.4
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• pp.533-535
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• 2007

For the purpose of decreasing intermodulation distortion, a new multi-harmonic suppression band-pass filter based on a microstrip radial stub is studied. Compared with traditional resonator filters, the new filter can suppress the second, third, and even fourth harmonics directly. The dimension of the filter is about $0.3\;{\lambda}_{g^0}{\times}0.13\;{\lambda}_{g^0}$ (${\lambda}_{g^0}$ is the guiding wavelength at the resonant frequency). Only one gap was introduced, so lower insertion loss can be obtained. Basic agreement between the measured and simulated results has been achieved.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.67-68
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• 2006

A suspended microstrip line structure over mushroom-like SMPs is designed and is applied to a dual-frequency and dual-polarization microstrip patch antenna. This structure has a distinctive and sharp rejection band and provides near 0 dB insertion loss outside the rejection band. Applying the structure to the conventional DFDP antenna enhanced the isolation between the two ports more than 20 dB. The structure is expected to have a wide range of applications in antennas and filters due to its compactness and integrability in circuits.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.7
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• pp.395-400
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• 2004

In this paper, the four-pole elliptic function microstrip filter at 2.4GHz band with fractional bandwidth of 4% is realized using compact miniaturized hairpin resonators. The parallel algorithm FDTD method is used to analyze S-parameter of hairpin resonator filter more accurately, and to calculate the electric coupling and magnetic coupling among the hairpin resonators. Absorbing boundary conditions for mesh termination used Sulivan's simplified PML and the FDTD code was paralleled by MPI for IBM SP2 which had enhanced calculation speed. The experimental measurements are performed by HP8720D vector network analyzer. Measured results on fabricated hairpin type cross coupled bandpass filters show good agreements with theoretic results.