• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.187-195
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• 1999

A series feedback DRO operating at 3.2 GHz applicable to the spectrum analyzer as the second local oscillator, is designed and fabricated. We can obtain a low noise by utilizing the small signal S-parameter of the transistor and adjusting the reflection coefficient from the coupling coefficient between dielectric resonator and microstrip line. The results show that output power is 10.50 dBm, a stable low phase noise is -116 dBc/Hz at a 10 kHz offset frequency and a harmonic characteristic is 19.33 dBc.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.24-28
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• 2016

This study presents a conductivity measurement technique that is applicable at radio frequencies (RF). Of particular interest is the measurement of the RF conductivity of a flexible Zell fabric, which is often used to implement wearable antennas on clothes. First, the transmission coefficient is measured using a planar microstrip ring resonator, where the ring is made of a Zell fabric. Then, the fabric's conductivity is determined by comparing the measured transmission coefficient to a set of simulation data. Specifically, a MATLAB-based root-searching algorithm is used to find the minimum of an error function composed of measured and simulation data. Several error functions have been tested, and the results showed that an error function employing only the magnitude of the transmission coefficient was the best for determining the conductivity. The effectiveness of this technique is verified by the measurement of a known copper foil before characterizing the Zell fabric. The conductivity of the Zell fabric at 2 GHz appears to be within the order of $10^4S/m$, which is lower than the DC conductivity of $5{\times}10^5S/m$.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.1
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• pp.245-252
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• 2018

In this paper, the dual band circular polarization patch antenna was designed by using band rejection characteristics of CSRR structure for geostationary satellites. A quadrangular CSRR structure was etched on the ground at the rear of the patch antenna's feed to obtain band rejection characteristics in between the receiving frequency band(1525~1559MHz) and transmission band(1626.5~1660.5MHz), and the corner of the patch antenna was truncated to enable circular polarization. It was confirmed that the resonant frequency of the patch antenna differs according to the size anc location of the CSRR and cirular polarization characteristics with simulation and measurement results. Measurement results shows the gain of about 0.2dB and 1.5dB in the TX and RX band.

• ETRI Journal
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• v.32 no.1
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• pp.112-119
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• 2010

We present a useful design for a free access mat which supports two frequency bands of 2.4 GHz and 5 GHz. The free access mat is a sheet-shaped waveguide which consists of a tightly coupled double-layered microstrip resonator array. It provides easy access for devices in short-range wireless communications. Interference is a common problem with conventional applications which use free space transmission. Our proposed wireless access system uses a subsidiary waveguide, the free access mat. Wireless devices are proximately coupled to the free access mat through which the coupled electromagnetic (EM) wave transmits. The arrival domain of the EM wave of an application is therefore limited to an area close to the free access mat. Wireless devices can be coupled to the free access mat at an arbitrary position without contact. We previously presented a free access mat for a single frequency band. This paper presents a free access mat for the two frequency bands of 2.4 GHz and 5 GHz. The free access mat uses a ring patch resonator array which is easily excited by typical antennas and is resistant to interference. These characteristics are demonstrated by numerical simulation and confirmed by experiment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.252-257
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• 2011

A compact microstrip dual-band bandpass filter with controllable bandwidth for each passband is proposed. Each passband is independently designed using two different dual-mode resonators. The proposed dual-band bandpass filter has three transmission zeros. Two transmission zeros are generated by each dual-mode resonator. An additional transmission zero is generated by input/output port coupling. The dual-band bandpass filter application is designed for 2.4/5.7 GHz WLAN. Experimental results are presented to validate theory.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.641-646
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• 2004

We report the changes of the microwave reflection coefficients S$_{11}$ of copper(II)-phthalocyanine (CuPc) thin films by using a near-field microwave microscope(NSMM) in order to understand the phase transition of CuPc. For a NSMM system, a high-quality microstrip resonator coupled with a dielectric resonator was used. CuPc thin films were prepared on the pre-heated glass substrates using a thermal evaporation method. The reflection coefficients S$_{11}$ of CuPc thin films were changed by the dependence on the substrate pre-heating temperatures. By comparing reflection coefficient S$_{11}$ and crystal structures, we found the phase transition of CuPc thin films from $\alpha$-phase to $\beta$-phase at the substrate heating temperature 200 $^{\circ}C$./TEX>.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.559-562
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• 2004

The $high-T_c$ Superconducting(HTS) antenna which consists of "H" type resonator has the benefits for the miniaturization of antenna in comparison with the microstrip antenna of the similar dimension. To fabricate the "H" type antenna HTS $YBa_2Cu_3O_{7-x}$(YBCO) thin films were deposited on MgO substrates using rf-magnetron sputtering. Standard etching processes were performed for the patterning of the "H" type antenna. For comparison between normal conducting antennas and superconducting antennas, the gold antennas with the same dimension were also fabricated. An aperture coupling was used for impedance matching between $50\Omega$ feed line and HTS radiating patch. The diverse experimental results were reported in terms of the resonant frequency, the return loss and the characteristics impedance. The "H" type superconducting antenna showed the performance of 1.36 in SWR, 24 % in efficiency, and 14.6 dB in the return loss superior to the normal conducting counterpart.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.3
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• pp.427-432
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• 2017

This study describes the design and implementation of SHF band Downconverter Digital Satellite Communication. The SHF band Downconverter unit consists of PLDRO and Frequency converter. In Frequency converter, microstrip BPF and LPF designed through the pre EM simulation are implemented to minimize the unwanted spurious in Frequency converter. Through the pre-simulation analysis of space environment, the possibility of and minimized about the malfunction of equipment and we designed a reliable SHF band Downconverter through simulation for a TID according to the vibration generated during the launch and space radiation environment, and compared pre-simulation of main performance results to test results about main performances of SHF band Downconverter after production.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.1
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• pp.20-26
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• 2003

This paper presents hairpin-comb bandpass filter using ground aperture. Hairpin-comb resonator maintains the weak coupling though the space between two resonators is very small. This has the good merit that the entire filter size is small for narrowband bandpass filter. The coupling between two hairpin-comb resonators so very weak that can't be applicable to general microstrip. We compensate the coupling by using ground aperture. It makes the hairpin-comb filter possible that can be applicable to general microstrip. Also it has the good merit which adjusts the bandwidth by changing the size of aperture without changing the space. In this paper, we fabricate the bandpass filter, which has 1.78 GHz center frequency and 62 MHz (3.5%) fractional bandwidth.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.721-724
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• 2001

In this paper, we present the effect the length the MSL(Microstrip Line) on the oscillation characteristic of the fabricated VCOs(Voltage Controlled Oscillator) designed and analyzed by RF circuit simulator Serenade(ANSOFT Co.) and fabricated by screen printing method on the alumina substrate. We have fabricated VCOs with 3 different MSL length and each MSL length of the VCO is 140mi1, 280mil and 560mi1. The oscillation frequency of each sample(VCO) was tuned to UHF band(750MHz∼900MHz) varying the capacitance. The experimental result shows the phase noise -82∼-97[dBc/Hz] at a 50 [kHz] offset frequency, the pushing figure 94∼318[kHz] at 3${\pm}$0.15[V] and the harmonics 13∼21 [dBc] between MSL length 140mi1s and 560mi1. The frequency and output variation width are 779∼898[MHz], -36∼-33[dBm] at MSL length 140mi1; 818∼836[MHz], -27.19∼-27.06[dBm] at 280mi1;751.54∼751.198[MHz],-33.44∼ -33.31[dBm] at 560mi1. we examined 3 VCOs oscillation characteristic difference through comparison with phase noise, oscillation power and frequency by control voltage change, harmonics and pushing figure for each sample.