• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.10
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• pp.1166-1172
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• 2012

In this paper, by using a commercial EM simulator, we could obtain the array manifold which are phase responses of an array antenna for the incident plane wave and then verified the effectiveness of methodology after comparing with the measurement. The result shows that the array manifold can be calculated including not only the phase response of the ideal point sources but also the influences of the mutual coupling between antennas and the installed platform. Also it can exclude the interference of strong broadcasting signal and the disturbance of the multipath in the calibration process. Finally, to predict the performances of direction finding systems, a novel method using both the EM simulation-based receiving signal and the sparsely sampled array manifold with the parabolic estimation is proposed. This method can be utilized in the various fields of direction-finding since it shows the superior predictive performance even in low SNR conditions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.556-561
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• 2008

The characteristics of microwave reflectometry, which is based on the technologies of FM radar and is applied as a non-invasive method to examine the properties including density distribution of inhomogeneous media, is investigated. The microwave reflectometry system requires not only an optimized system hardware but as well as the understanding of system response from the media under test in order to provide the system solution describing the object under test quantitatively. The introduction of microwave reflectometry especially in the area of applied plasma physics has been relatively new and the number of usage is found to be increasing gradually. The experimental method to characterize the microwave system as a device to examine the properties of plasma is explained. The microwave reflectometry signals consist of the cutoff signals which originate from the region where most of the reflected power comes from and the scattered signals which result as an interaction of the microwave and the density perturbations. This paper describes the experimental results of the scattered signal from the microwave reflectometry, such as the wavenumber dependence and the sensitivity on density perturbation, and the comparison of the characteristics with those from the numerical simulations and those from the cutoff signals.

• Journal of Sensor Science and Technology
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• v.5 no.1
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• pp.43-50
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• 1996

This paper presents a manufacture of the multiple subjects biotelemetry system using custom CMOS IC fabricated $1.5{\mu}m$ n-well process technology. The implantable circuits of the system except sensor interface circuits including FM transmitter are fabricated on a single chip with the sire of $4{\times}4mm^{2}$. It is possible to assemble the implantable system in a hybrid package as small as $3{\times}3{\times}2.5cm$ by using this chip, It's main function is to enable continuous measurement simultaneously up to 7-channel physiological signals from the selected one among 8 subjects. Another features of this system are to enable continuous measurement of physiological signals, and to accomplish ON/OFF switching of an implanted battery by subject selection signal with command signal from the external circuit. If this system is coupled with another appropriate sensors in medical field, various physiological parameters such as pressure, pH and temperature are to be measured effectively in the near future.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1074-1080
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• 2013

The low phase noise and wideband frequency synthesizer has been designed by using YTO. Offset PLL structure is used for reducing a division ratio of feedback loop. The phase noise modeling is applied to optimize loop filter of PLL and YTO module. And DDS is used as reference signal of frequency synthesizer for fine resolution. The fabricated wideband frequency synthesizer has the output frequency of 3.2 GHz to 6.8 GHz, phase noise of -107 dBc/Hz at 10 kHz offset from the carrier and frequency resolution of 1 Hz. The measured phase noise is well agreed with the simulated one.

• International Journal of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.58-63
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• 2017

The sound we hear is transmitted through the atmosphere. However, both the sound we want to hear and the surrounding sound are mixed, and noise is generated, and the sound is not clearly transmitted due to factors such as distance. In particular, in closed spaces like buildings, it is often difficult to hear sounds from outside because of the sound of reflection. People with hearing impairments, such as the elderly and the deaf, have a hard time hearing the sounds they want to hear. Thus, we are developing a hearing aid that can detect radio waves. To this end, we propose the development of a hearing aid that uses FM radio and Bluetooth. These devices are expected to be useful not only for the elderly and the deaf but also in situations where information is transmitted to a large number of people, such as students and tourists, in a large space. The main purpose of this device is to enable users to hear sound correctly without blind spots.

• Progress in Superconductivity
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• v.6 no.1
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• pp.19-23
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• 2004

YBCO do superconducting quantum interference device (SQUID) magnetometers based on bicrystal Josephson junctions on 10 mm ${\times}$ 10 mm $SrTiO_3$ substrates have been fabricated. The pickup coil of the device was designed to have 16 parallel loops with 50-fm-wide lines. We could obtain optimised direct coupled YBCO SQUID magnetometer design with field sensitivity $B_{N}$ $\Phi$/ of $4.5 nT/\Phi_{0}$ and magnetic field noise $B_{N}$ of about $22 fT/Hz^{1}$2/ with an I/f corner frequency of 2 Hz measured inside a magnetically shielded room. Preliminary results of magnetocardiograph measurement using the HTS SQUID magnetometers show signal to noise ratio of about 110, which is comparable to the quality of a commercial MCG system based on Nb-SQUIDs.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.2
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• pp.100-106
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• 2016

Spectrum sensing is an integral part of cognitive radio, which seeks to address the perceived spectrum scarcity that is caused by inefficient utilization of the available spectrum. In this paper, a spectrum sensing system using energy detection for analog TV and FM broadcast transmitters as well as modified Integrated Services Digital Broadcasting Terrestrial (ISDB-T) signals is implemented on a software-defined radio platform using GNU' Not Unix (GNU) radio and the N200 Universal Software Radio Peripheral (USRP). Real-time implementation and experimental tests were conducted in Metro Cebu, a highly urbanized area in the southern part of the Philippines. Extensive tests and measurements were necessary to determine spectrum availability, particularly in the TV band. This is in support of the Philippine government' efforts to provide internet connectivity to rural areas. Experimental results have so far met IEEE 802.22 requirements for energy detection spectrum sensing. The designed system detected signals at -114 dBm within a sensing time of 100 ms. Furthermore, the required $P_d({\geq}90)$ and $P_{fa}({\leq}10)$ of the standard were also achieved with different thresholds for various signal sources representing primary users.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.178-180
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• 2012

본 논문에서는 유럽의 디지털 라디오 전송 규격인 DRM(Digital Radio Mondiale)의 Band II 대역 전송 모드인 모드 E의 전송률 향상 기법을 제안한다. DRM 모드 E는 FM 방송과의 동시방송 등의 문제를 고려하여 100kHz 대역폭에서 186kbps의 전송률을 제공한다. 하지만, 이 전송률은 모바일TV 등 멀티미디어 서비스를 제공하기 위해서는 부족하기 때문에 전송률의 향상이 요구된다. 논문에 제안된 전송률 향상기법은 기존의 DRM 모드에 변조방식 및 부호방식을 추가하는 방식으로 최대 350kbps의 전송률 제공이 가능하며, FAC(Fast Access Channel)의 예약필드에 신규 방식에 대한 정보를 전송함으로써 기존 시스템과 호환성을 유지할 수 있다. 모의실험 결과에서, AWGN(Additive White Gaussian Noise) 채널의 비트오류율 le-4를 기준으로 223kbps의 전송을 위해서는 13dB의 SNR(Signal-to-Noise Ratio)이 요구되며, 351kbps의 전송률 제공을 위해서는 약 18dB의 SNR이 요구됨을 확인할 수 있다. 또한, 다중경로 페이딩 채널환경에서 부호율이 1/2인 경우에는 이동속도보다는 지연확산이 성능에 영향을 주지만, 부호율이 1/2 보다 크며 150Km/h이상 증가하면 오류마루가 발생함을 확인할 수 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.754-756
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• 2013

The modern Electronic Warfare Receivers are required to the current radar technologies like the Low Probability of Intercept(LPI) radars to avoid detection. LPI radars have features of intra-pulse modulation differ from existing radar signals. This features require counterworks such as signal confirmation and identification. Hence this paper presents a study on intra-pulse modulation recognition. The proposed method automatically recognizes intra-pulse modulation types such as LFM and NLFM using classifiers extracted from the features of each intra-pulse modulation. Several simulations are also conducted and the simulation results indicate the performance of the given method.

• Journal of Advanced Navigation Technology
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• v.21 no.6
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• pp.554-560
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• 2017

Accurate altimetry is required for the reliable flight control of drones or unmanned air vehicles (UAVs), and the radar altimeter is commonly used owing to its accuracy for the ground level. Due to the limitation for size, weight and power consumption, the frequency modulated continuous wave (FMCW) radar is appropriate for drone because it has lower complexity than that of pulse Doppler (PD) radar. Especially, fast-ramp FMCW radar, which transmits linear FM signal during very short period, is generally utilized, because it is robust for the ego-motion of drone. Therefore, we present the design and implementation results of the radar signal processor (RSP) for fast-ramp FMCW radar system. The proposed RSP was designed with Verilog-HDL and implemented with Altera Cyclone-IV FPGA device. Implementation results show that the proposed RSP includes 27,523 logic elements, 15,798 registers and memory of 138Kbits and can measure the altimeter at the rate of 100Hz with the operating frequency of 50MHz.