• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.2
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• pp.204-212
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• 2015

Harmonic effects in a wideband stepped frequency radar(650 MHz~4.5 GHz) have been analyzed. As a result of numerical analysis and simulation, when the second harmonic exists in each frequency, a time-domain result represents an additional object which does not exist but looks to be located at a distance of twice the original object distance. The second harmonics can be removed effectively by low pass filters because there are no other signals between DC and a fundamental signal. In this paper, the harmonic problem can be solved by removing the second harmonics of 650 MHz to 4.5 GHz wideband fundamental signal with two switches and four low pass filters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.5
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• pp.435-444
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• 2015

This paper specifies on a virtual array design of a 77 GHz vehicle radar for detecting a moving target at a time division transmit and a near range. The virtual array designed reduces a hardware complexity, weight and price. However, a synthesized beam of the virtual array has a high side lobe by a phase distortion of receive signals when the moving target is detected at the time division transmit. For this, a subarray receive signal with a same phase is used and the side lobe of the synthesized beam is suppressed above at least 10 dB. Also the virtual array has a beam distortion by a spherical wave when the vehicle radar operates at near range. So a boresight receive signal of each target range is compensated at each receive signal. Therefore the synthesized beam with compensation recovers a normal main lobe and improves the side lobe about 10~15 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1168-1177
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• 2004

This paper presents the characteristics of the electromagnetically coupled small broadband disk-loaded monopole antenna with multiple shorting pins. The electromagnetically coupled monopole antenna can achieve broad bandwidth by controlling resonant frequency of the rectangular disk-loaded monopole and a probe with the spiral strip line monopole. The number and arrangement of the shorting pin affect the capacitance of the disk. The variation of the capacitance changes resonant frequency of the antenna, and therefore, its electrical sizes and frequency bandwidth are also affected. The antenna with three shorting pins has a volume of $0.094\lambda_0{\times}0.094\lambda_0{\times}0.094\lambda_0$ in electrical length and the frequency bandwidth of $26.8\%\;for\;VSWR\leq2$ with the center frequency at 2.556 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.9
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• pp.777-782
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• 2015

In this paper, the compact CPW-fed antenna with triple folded patch for dual-band WLAN applications is proposed. As the conventional double inverted-L antenna is changed into the C-shaped patch and double inverted-L antenna, the antenna overcomes the narrow-band characteristics according to the miniaturization of the antenna. The proposed antenna with the size of only $16.5mm{\times}29.5mm{\times}1.0mm$ is designed and fabricated by optimized parameters to be operated at 2.4 GHz band and 5 GHz band. The antenna is fabricated into FR-4 substrate with thickness of 1.0 mm. We confirm that it is operated as antenna for WLAN applications by obtaining the measured return loss level of < -10 dB at dual-band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.7
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• pp.606-612
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• 2015

This paper proposes a new design of a dual-band orthogonal-polarization microstrip antenna for V2N(Vehicle to Nomadic Device) communication system. The proposed antenna consists of a perpendicular feeding structure for utilizing orthogonal linear polarizations and an microstrip radiator which loaded by close-looped H-shape slot for obtaining dual-band operation. Due to the geometrically different loading effect of the close-looped H-shape slot for each feeding location, the orthogonally linear polarization at dual-band operation of the proposed antenna can be successfully achieved. The proposed antenna theoretically and experimentally demonstrates the vertical linear polarization at the operating frequency of 1.8 GHz and the horizontal linear polarization at the operating frequency of 2.4 GHz, respectively. The simulation and measurement results of the implemented antenna have been in good agreement with the reflection coefficients, radiation patterns, and realized antenna gains.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.10
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• pp.1151-1156
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• 2012

In this paper, the baseband filter is proposed in order to maintain a constant sensitivity regardless of distances for 77 GHz automotive radar system. Using existing DCOC loop circuit can remove DC offset and also cancel differences of received power depending on the distance. Measured results show that the maximum gain is 51 dB and high pass cutoff frequency can be tuned from 5 kHz to 15 kHz. The slope of high pass filter can be tuned from -10 to -40 dB/decade for the distance compensation. The measured NF and IIP3 are 26 dB and +4.5 dBm with 4.3 mA at 1.0 V supply voltage, respectively. The fabricated die size $500{\mu}m{\times}1,050{\mu}m$ excluding the in/out pads.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.8
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• pp.740-747
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• 2015

Recently, mobile communication systems using the millimeter-wave frequency band have been proposed, and the importance of efficient compensation of the nonlinearity caused by 60 GHz high-power amplifiers(HPAs) is increasing. In this paper, we propose a predistorter structure based on multiple coefficient sets which are separately used to different ranges of input power values. These ranges correspond to varying levels of nonlinearity characteristics. The structure is applied to the 60 GHz HPA FMM5715X and the performance of correcting the nonlinearity of LTE signals is evaluated. Evaluation results using a hardware testbed demonstrate that the proposed predistorter structure achieves the maximum of 6 dB gain over the conventional method in terms of the adjacent channel leakage ratio(ACLR).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.24-29
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• 2015

In this paper, we propose a method of isolation improvement for broadband antennas using a high-permeability substrate. The substrate is applied for a planar monopole antenna based on near-field analysis to maintain radiation characteristics at its operating frequency while improving isolation by minimizing mutual coupling with nearby antennas at other frequency bands. To verify isolation improvement, we compare performance variations of $S_{21}$ according to the existence of the substrate using the proposed antenna and a reference antenna whose operating frequency is 2 GHz. As a result, the radiation characteristics are maintained, and $S_{21}$ performance is improved by more than 5~10 dB in the frequency band of greater than 2 GHz, which demonstrates the isolation can be improved by using the high-permeability substrate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.17-24
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• 2008

This paper deals with a millimeter wave source which is utilizing sub-harmonic injection-synchronization technique. A 8.7GHz oscillator with MES-FET is fabricated, and is driven as a harmonic output oscillator at 17.4GHz by means of sub-harmonic injection-synchronization. The oscillator operates as a multiplier as well as oscillator in this system. Adopting this technique, we can obtain a high stable, high frequency millimeter wave source even though self-oscillating frequency of an oscillator is relatively low. In the experiments, the range of injection-synchronization is about 26MHz and is proportional to the input sub-harmonic power. From the spectrum analysis of the 2nd harmonic output. we blow that the phase noise of the harmonic oscillator is remarkably decreased.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.763-770
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• 2021

In this paper, in order to exclude the influence of BAN(Body Area Network) signals operating in the ISM band, the design and optimization process of an on-body microstrip patch antenna operating at 4.567 GHz is presented. The antenna for the monitoring of the lower legs with cancellous osteoporosis is designed to be lightweight and compact with improved return loss and bandwidth. The structure around the applied lower leg consisted of a five-layer dielectric plane. Taking into account losses, the complex dielectric constant of each layer is calculated using multi Cole-Cole model parameters, whereas a unipolar model is used for normal or osteoporotic cancellous bones. The return loss of the coaxial feed antenna on the phantom is -67.26 dB at 4.567 GHz, and in the case of osteoporosis, at the same frequency the return loss difference is 35.88 dB, and the resonance frequency difference is about 7 MHz.