In this thesis, We researched on the characteristics of optical tunable filter that selects the channel by the wavelength changes of transmission spectrum when we apply outer physical quantities on a fiber bragg grating by using Fabry-Perot Interformer's operational principle.

A compact microstrip band-selective filter for ultra-wideband (UWB) radio system is proposed. The filter combines the traditional short-circuited stub highpass filter and coupled resonator bandstop filter on both sides of the mitered 50-ohm microstrip line. To realize the pseudo-highpass filtering characteristic over UWB frequency band (3.1 GHz to 10.6 GHz), a distributed highpass filter scheme is adopted. Three coupled resonators are utilized to obtain the band stop function at the desired frequency band. By meandering the coupled resonators, there is 29% reduction in footprint compared to the traditional bandstop filter using L-shaped resonators. The measured results show that the filter has a wide passband of 146.7 % (2.1 GHz to 10.15 GHz) with low insertion loss and the stop band of 7.42 % (5.32 GHz to 5.73 GHz) for 3-dB bandwidth. The measured group delay is less than 0.7 ns within the passband except the rejection band.

Many mobile communication systems require bandpass filter with sharp skirt characteristics and consequently a filter was formed by more order. It needs to improve flatness in passband. In this paper, amplitude equalizer was used to improve the flatness of passband. We modified Chebyshev prototype filter by use of network synthesis and computed the prototype elements for Shaping filter. We designed and realized a 13-order combline bandpass filter and 4-order amplitude equalizer with coaxial dielectric resonators at WiBro band. The measured results show $\pm$0.82 dB amplitude difference in passband, 6 dB improved flatness.

This paper presents a improvement equivalent circuit model for Miniaturized LTCC bandpass filter with two transmission zeros using feed-back capacitor. The bandpass filter equivalent circuit is evaluated by parallel network analysis. Besides, the filter is modeled by proposed passive element modeling algorithm in previous work. Compared to the equivalent circuit of established paper that is configured by excepted capacitance between ground plate and signal plate, this model can include that. The result, the LTCC bandpass filter reduce layers and the size is more smaller.

An airborne radar is an essential aviation electronic system of the helicopter to perform various missions in all-weather environments. This paper presents the results of the design and implementation of the airborne pulse doppler radar signal processor using high multi-DSP for the multi-function radar capability such as short-range, midium-range, and long-range depending on the mission of the vehicle. Particularly, the radar signal processor is developed using two DSP boards in parallel for the various radar signal processing algorithm. The key algorithms include LFM chirp waveform-based pulse compression, MTI clutter filter, MTD processor, adaptive CFAR, and clutter map. Especially airborne moving clutter Doppler spectrum compensation algorithm such as TACCAR is implemented for the multi-mode airborne radar system. The test results shows the good Doppler spectral separation for the clutter and the moving target in the flight test environment using helicopter.

본 논문에서는 right/left-handed특성을 이용한 8 포트 동위상 전력분배기를 제안한다. 이 전력분배기는 사용되는 전송선의 전기적 길이에 상관없이 동위상 분배가 가능하기 때문에 전력 분배기의 크기를 크게 줄일 수 있다. 전력분배기에 사용되는 전송선의 길이가 짧을수록 광대역 특성을 보이며 분배기의 크기는 줄어든다.

In this paper, a simulator for radar performance evaluation in a far-field test range is proposed, which can forecast maximum detection range, minimum detection range, number of test trials, resolution (range, azimuth, elevation) with input parameters before radar performance test and process results after. The proposed simulator is designed by Microsoft Foundation Class (MFC) of VC++ 6.0.

A broadband DC to 40 GHz 5-bit MMIC digital attenuator has been developed. The ultra broadband attenuator has been achieved by newly inserted the transmission lines in conventional Switched-T attenuator and the optimization of the transmission line parameters. Momentum was employed in design for an accurate performance prediction at high frequencies and Monte Carlo analysis was applied to verify performance stability against the MMIC process variation. The attenuator has been fabricated with 0.15 $\mu$m GaAs pHEMT process. This attenuator has 1 dB resolution and 23 dB dynamic range. High attenuation accuracy has been achieved over all attenuation range and full 40 GHz bandwidth with the reference state insertion loss of less than 6 dB at 20 GHz. The input and output return losses of the attenuator are better than 14 dB over all attenuation states and frequencies.

This paper make an analysis of UWB Communication System. In case endoscope, medical equipment, is applied to UWB, We could study through body-channel that frequency transmitted of received signal is differ from wireless in the existing air. It suggested TR-UWB form, non-coherent received method in dispersion-medium like humans bodies by accomplishing ability analysis of BPM, TR, BER of Differential, UWB Communication modulation and demodulation form.

In this paper we implemented the algorithm of methodology for calculation of spectrum requirements and analyzed the influence of traffic distribution ratio among radio access technology groups, spectral efficiency, and flexible spectrum usage margin on spectrum requirements for future development of IMT-2000 and systems beyond IMT-2000

In spite of many advantages of OFDM, a major drawback for implementation is a non-linear distortion in the HPA due to a high PAPR problem. In this paper, the Complementary Clipping Transform technique (CCT) for the PAPR reduction of OFDM system is analyzed for the QPSK and QAM mapping data. BER performance and PSD in front of HPA and after HPA are analytically demonstrated.

In this paper, Coplanar Waveguide(CPW) low-pass filter with the spurious-reduced is designed by using Defected Ground Structures(DGS). Two different LPF unit cells and DGS pattern are combined to reduce the spurious. In comparison to a conventional step impedance LPF, the size of proposed LPF as 17.2mm*6.8mm is several times smaller. The simulation and measurements confirm that spurious characteristics is presented less than -30dB($S_{21}$) to three times cut off frequency.

The High Peak to Average Power Ratio (PAPR) could be a severe Problem in OFDM performance since it causes the significant distortion to the transmitting signal through a nonlinear device such as High Power Amplifier (HPA). In this paper, the performance of Peak cancellation method according to the HPA characteristic is comparatively analyzed with the clipping and windowing methods. The BER performances and the out-band power spectrums are demonstrated in detail.

In this paper, Compact Microstrip Resonants Cell(CMRC) have been employed to suppress IMD(Intermodulation Distortion) of the 3-Way Doherty amplifier. This method can not only improve the linearly and the efficiency but also is simpler, smaller and more inexpensive than existing linearly methods; (for example Harmonic feedback, Back off, Feed-forward, Predistortion and so on.) Also, the proposed 3-way Doherty amplifier using only one divider has been reduced size of existing 3-Way Doherty amplifier. As a result, the proposed Doherty amplifier using CMRC and only one divider has been improved for the IMD$_3$ by 4.474dBc, and the PAE by 9.199%, respectively.

In this paper, we present an efficiency extension of Doherty power amplifier using LDMOS FET devices with different peak output powers and an unequal power divider. The amplifier is designed by using a MRF21045 with P1 dB of 45 W as the main amplifier biased for Class-AB operation and a MRF21090 with P1 dB of 90 W as the peaking amplifier biased for Class-C operation. The input power is divided into a 1:1.5 power ratio between the main and peaking amplifier. The simulated results of the proposed Doherty amplifier shows an efficiency improvement of approximately 19 % in comparison to the class-AB amplifier at an output power of 42.5 dBm. The fabricated Doherty amplifier obtained a PAE of 33.68 % at 9 dB backed off from P1 dB of 51.5 dBm.

High-efficiency switched-mode circuits such as the class-E amplifier are well-known in the MHz frequency range. The class-E amplifier is a type of switching mode amplifier offering very high efficiency approaching 100%. In this paper of the class-E amplifier by using pHEMT device, the design has been done theoretically and experimentally, with simulation by using the harmonic balance method using circuit simulator. The amplifier using microstrip circuit and the pHEMT demonstrate 66% power-added- efficiency (PAE) at 2.4GHz with 17.6dBm of output power.

In this paper, describes the design and performance of a 1.5 kW solid-state pulsed power amplifier, operating over 2.7-2.9 GHz at a duty of 10% and with a pulse width of 100 us for radar application. The solid-state pulsed power amplifier configures a series of 8-stage cascaded power amplifier with different RF output power levels. Low loss Wilkinson combiners are used to combine output powers of six 300W high power solid state modules. Tests show peak output power of 1.61 kW, corresponding to PAE of 26.2% over 2.7-2.9 GHz with pulse width of 100 us and a PRF of 1 kHz.

This paper proposes a linearization method that is to control the operating point of a class AB amplifier according to its output power. The proposed linearization method is presented in this paper and the performance test results using two-tone signal are presented also.

This paper presents a new microwave oscillator incorporating a corrugated coplanar waveguide (CCPW) electromagnetic bandgap (EBG) structure as its terminating resonance component. The use of a compact CCPW EBG structure was effective in reducing the phase noise and improving the harmonic characteristics of the microwave oscillator circuit without additional backside processing and drastic size increment. The fully planar CCPW oscillator oscillating at the frequency of 5.41 GHz showed a phase noise characteristic of -90.7 dBc/Hz at 100kHz offset and a second harmonic suppression of 42.67 dB.

This paper describes the design and fabrication of synchronous clock recovery module for S-DMB Gap Filler. Using the 2.304MHz TTL signal from gap filler tuner, clock recovery module with 10MHz output frequency including holdover function is designed. The measured performance of the clock recovery module shows a stability of less than 0.01ppm, 29 sec stability time, 10 sec holdover time, and maximum -113dBc/Hz@100Hz phase noise.

The isolation performance of the S-band single-pole single-throw (SPST) monolithic microwave integrated circuit (MMIC) switch with two different RF-interconnection approaches, microstrip and grounded coplanar waveguide (GCPW) lines, are investigated. On-to-off isolation is improved by 5.8 dB with the GCPW design compared with the microstrip design and additional improvement of 6.9dB is obtained with the coplanar wire-bond interconnection (CWBI) at 3.4 GHz. The measured insertion loss and third-order inter-modulation distortion (IMD3) are less than 2.43 dB over 2.5 CHz $\sim$ 4 GHz and greater than 64 dBc.

A c-band microwave radiometer receiver for river mouth water temperature remote sensing was designed and implemented The developed receiver operated at 5.1GHz frequency with 70MHz bandwidth. It had high gain of 50dB and low noise figure of 2dB. Also we executed efficiency evaluation about detection capability of the receiver with noise source similar input signal. The experiment results showed that the c-band receiver successfully detected the antenna temperature range from 193K to 300K.

The High Rate Wireless Personal Area Networks (WPAN) is mainly targeted to consumer electronics and portable communication devices which need high rates and QoS. To achieve these goals, the WPAN provides data rates up to 1Gbps and adopts a Time Division Multiple Access (TDMA) MAC protocol. Since IEEE 802.15.3 MAC is based on TDMA scheme, it has good performance in dealing with real traffics. But it does not give better results for dynamic traffic. For dynamic traffic, IEEE 802.15.3 MAC needs a kind of request and response policy that brings about the degradation of performance in order to adapt to network changes. To overcome this problem and enhance the data throughput, this paper proposes a superframe structure which uses the Enhanced Contention Access Period (ECAP) to transmit data during sleep-CTA in PM mode.

This paper suggests an efficient method of protection ratio calculation and shows some calculated results applicable to frequency coordination in microwave relay system networks, and the net filter discrimination (NFD) associated with Tx spectrum mask and overall Rx filter characteristics has been examined to obtain the adjacent channel protection ratio. The protection ratio comprises several factors such as C/N of modulation scheme, noise-to-interference ratio, multiple interference allowance, fade margins of multi-path and rain attenuation, and NFD. According to computed results for 6.7 GHz, 64-QAM, and 60 km at BER $10^{-6}$, fade margin and co-channel protection ratio are 41.1 and 75.2 dB, respectively, In addition, NFD for channel bandwidth of 40 MHz reveals 28.9 dB at the first adjacent channel, which results in adjacent channel protection ratio of 46.3 dB. The proposed method provides some merits of an easy calculation, systematic extension, and applying the same concept to frequency coordination in millimeter wave relay system networks.

UWB is the most spotlighted wireless technology that transmits data at very high rates using low power over a wide spectrum of frequency band. UWB technology makes it possible to transmit data at rate over 100Mbps within 10 meters. To preserve important header information, MB-OFDM UWB adopts Reed-Solomon(23,17) code. In receiver, RS decoder needs high speed and low latency using efficient hardware. In this paper, we suggest the architecture of RS decoder for MB-OFDM UWB. We adopts Modified-Euclidean algorithm for key equation solver block which is most complex in area. We suggest pipelined processing cell for this block and show the detailed architecture of syndrome, Chien search and Forney algorithm block. At last, we show the hardware implementation results of RS decoder for ASIC implementation.

A frequency synthesizer of 10 GHz $\sim$ 11 GHz for FMCW radar is designed and implemented by the form of indirect frequency synthesizer of a single loop structure. The synthesizer uses a high speed digital PLL chip. It is difficult to divide directly by using a program counter of PLL chip because the output frequency of VCO is 10 GHz $\sim$ 11 GHz, so we lower the frequency to 625 MHz $\sim$ 687.5 MHz by using a prescaler, and then divide the frequency by the program counter. The output frequency sweep of VCO from 10 GHz to 11 GHz is measured.

The objective of this study is to estimate RF signal strength over sea and land surfaces. For this work we calculated scattering by land with DEM(Digital Elevation Model) and sea surface with RMS surface height. and we selected two area inland and sea shore as RX point. And for each area, we get VV-pol and HH-pol characteristic of scattering at 2.2GHz.

The DC power-bus' resonance is frequently attributed to EMI sources in the PCBs. Subsequently, it will ruin the digital signal integrity within one system or between adjacent systems in the form of conducted or radiated emission. Hence, since it is of importance to examine the PCB's emission, this paper sheds a light on the radiated emission from the power-bus with regards to its resonance modes. A full-wave analysis method is used to calculate the impedance and radiated electric fields and is validated by physics and an EM analysis tool.

This paper concerns an efficient iterative approach for eliminating coherent interference signals in linearly constrained adaptive arrays. The Alternate Mainbeam Nulling Algorithm[1] is implemented iteratively to find an optimum weight vector. The convergence parameters in the unit gain and null constraints are calculated using steepest descent method with gradient estimation. The nulling performance of the proposed method is compared with that of conventional ones. It is shown that the proposed method performs better than conventional ones when the power of the coherent signals is large compared with a desired signal. Also, it performs consistently well for more number of interferences.

In this paper, we have analyzed the effects of interference from HAPS ground stations to P-MP FWA base station and to P-MP FWA terminal station using more detail parameters such as a new interference model, a realistic HAPS scenario, practical antenna patterns for both the HAPS system and FWA systems. The analysis results show that, in the case of interference from HAPS GSs into a P-MP BS, compatibility of the two systems can be obtained by using a sectored BS antenna with the boresight directed away from the nadir However, in the case of interference from HAPS GSs into a P-MP TS, the two systems cannot operate effectively in the same band unless the separation distance is guranteed and/or some form of interference mitigation technique is employed such as dynamic channel allocation.

Attenuation in vegetation is important, for both terrestrial and earth-space systems. However, the wide range of conditions and types of foliage makes it difficult to develop a generalized prediction procedure. Currently, there is also a lack of suitably prediction model and measured experimental data for vegetation loss. So in this paper, vegetation loss data for four different tree-species, including Dawn-redwood tree, Plane tree, Pine tree and Fir tree are obtained by measurement in the frequency range of 1.0 $\sim$ 6.0 GHz. The through or scattered component is calculated using a model based upon the theory of RET(Radiative Energy Transfer) and RET modeling parameters are extracted from the measured data.

본 논문에서는 시간영역 유한차분법(FDTD: Finite-Difference Time-Domain Method)과 설계민감도법(Design Sensitivity Analysis)을 이용하여 유전체 산란체(Dielectric Scatterer)를 복원하기 위한 역산란문제(Inverse Scattering의 새로운 해석기법을 제안하였다. 이때 복원의 빠른 수렴을 위하여 도함수를 이용한 설계민감도법을 도입하였고 본 연구에서는 시간영역 유한차분법으로부터 직접 설계민감도 수식을 도출하였다. 계산의 효율성을 위하여 보조변수법(Adjoint Variable Method)을 도입하여 보조변수 방정식을 도출하고 최적화 알고리듬으로 최대경사도법을 이용하여 반복적인 추정을 통하여 유전체를 복원하였다. 본 연구의 타당성의 보이기 위하여 2차원 $TM^2$에서의 유전체 복원 사례를 제시한다.

중첩 T블록 방법을 이용하여 네모난 금속 홈에 평면파가 입사되는 경우의 해석적인 산란해를 구한다. 여러 개의 금속 홈이 있는 경우에도 각 영역을 세부 영역으로 나누어 수치효율을 증대시킨다. 최종 산란해가 빠른 적분식을 가진 간단한 닫힌 해로 표시된다.

In this paper, optical noise is reduced using a differential detector in an 1.3$\mu$m optical wireless system which is more safe for human eye than 0.8$\mu$m optical wireless systems. The differential detector is composed of a InGaAs photodiode and a Si photodiode. This is a very simple and cost effective method to reduce the noise interference from incandescent lamps.

A two dimensional (2-D) finite-difference time-domain (FDTD) method based on a novel finite difference scheme is developed to eliminate the numerical dispersion errors. In this paper, numerical dispersion and stability analysis of the new scheme are given, which show that the proposed method is nearly dispersionless, and stable for a larger time step than the standard FDTD method.

In this dissertation, a temperature characteristics of the LDMOS is proposed by the method of changing the gate voltage to find the optimum points when the IMD characteristics is changed by the atmosphere temperature. Experimental results have good agreement with the ADS simulation about the 3rd and 5th IMD when the gate voltage is changed with the fixed temperature.

A low-cost, high-performance 40 Gb/s clock recovery module using a phase-locked loop(PLL) for a 40 Gb/s optical receiver has been designed and implemented. It consists of a clock recovery circuit, a RF mixer and frequency discriminator for phase/frequency detection, a DR-VCO, a phase shifter, and a hold circuit. The recovered 40 GHz clock is synchronized with a stable 10 GHz DR-VCO. The clock stability and jitter characteristics of the implemented PLL-based clock recovery module has shown to significantly improve the performance of the conventional open-loop type clock recovery module with DR filter. The measured peak-to-peak RMS jitter is about 230 fs. When input signal is dropped, the 40 GHz clock is generated continuously by hold circuit. The implemented clock recovery module can be used as a low-cost and high-performance receiver module for 40 Gb/s commercial optical network.

In this paper, we analyzed the signal distortion incorporating meander-shaped transmission line on PCB in broadband frequency range, up to 50GHz. This broadband characteristic provides reasonable analysis of digital pulse having very short rising time. Simulation results reveal suppression characteristic at multiband which is dependent on only the width of meander arm. This width of arm also can be adjusted using different permittivity because it provides different effective wave-length. It is found that the suppression characteristic shows sharpness with as a function of the number of arms. However, these characteristics shown limitation for microstrip line structure rather than for stripline structure, so we can avoid these unwanted phenomena using stripline structure.

In this paper, a planar half-circle shape ultra-wideband(UWB) antenna fed by CPW is designed, fabricated and measured for UWB communications. Within the UWB band(3.1 GHz $\sim$ 10.6 GHz), 5.15 GHz $\sim$ 5.825 GHz frequency band is used by IEEE 802.lla WLAN applications. It may be necessary to notch out this band to avoid interference with IEEE 802.lla WLAN. Therefore, we have proposed three kinds of UWB antennas having a notch function, such as a rectangular slot, a hat-shaped slot, a circle-shaped slot. The notch frequency of the proposed antenna can be adjusted by controlling the slot length or slot width. From the measured results, the proposed antennas show a good gain flatness except the IEEE 802.lla WLAN frequency band and have a reasonable agreement with simulated results.

In this paper, we have designed, fabricated and measured a compact rectangular mono-cone antenna for ultra-wideband applications. The proposed antenna covers the entire UWB band (3.1 GHz $\sim$ 10.6GHz). The measured bandwidth is 8.2 GHz from 2.8GHz to 11 GHz for ${\mid}S_{11}{\mid}{\leq}-10dB$. From the measured results, the proposed antenna shows a good characteristics (linear phase, omni-directional pattern and very low gain variation) for UWB applications. Also, the measured results have a reasonable agreement with the simulated results.

In this paper describes novel m antenna using aperture matched type slot structure. It substitutes edge diffractions by curved-surface diffractions which have a tendency to provide an undisturbed energy flow across the junction, around the curved surface, and into free-space. The proposed antenna is composed of a CPW feed structure, exponential tapered slot and the curved sectional at the edge. experimental resulte show that aperture matched type slot improve the performance of the UWB antenna.

In this paper, We have designed, fabricated and measured a stacked planar antenna for Ultra-Wideband communication. Radiation parts of the antenna have exponential curve and fed by strip feeding network. We have used the HFSS of Ansoft to simulate the antenna. It was designed to work on a substrate Teflon of thickness 1.575mm and relative permittivity 3.2. The proposed antenna covered the entire UWB band( 3.1GHz $\sim$ 10.6GHz ) for S11$\leq$l0dB. Also the proposed antenna show a good characteristics, linear phase, omni -directional pattern lot UWB applications. Besides the measured results have a reasonable agreement with the simulated results.

The proposed Triple-band Compact Chip Antenna using Coupled Meander line and stacked meander Structure for Mobile RFID/PCS/WiBro. The proposed antenna is designed to operate at 900, 1800, and 2350 MHz, and is realized by parasitic coupled and stacked a meander line. Meander lines are using extend length of effective current path more than monopole and contribute miniaturization. The coupled meander line controls the excitations of the Mobile RFID and PCS, stacked meander line controls the excitation of the WiBro. The proposed antenna size is $11mm\times22.5mm\times1mm$. The antenna supports 900MHz, 1800MHz and 2350MHz operations simultaneously with bandwidths of 33MHz, 230MHz and 100MHz, respectively. The proposed antenna gains are result of simulation to be -0.8dBi, 3dBi and 3.8dBi, respectively.

In this paper, Dual-polarized Tx/Rx antenna for RFID reader is designed and fabricated to apply to RFID reader. Each feeding network of Tx/Rx is designed to improve the port-isolation and cross-polarization, and sequential rotation feeding scheme has been applied to increase of axial ratio bandwidth. Measured results show that 2.35dBi of antenna gain in 900MHz$\sim$928MHz, 150MHz of 3dB axial ratio bandwidth, -38dB$\sim$-40dB of port-isolation, and -30dB$\sim$-40dB of cross-polarization.

This paper presents a dual band circularly polarized microstrip patch antenna. The antenna consists of two corner truncated patches implemented in one plane and single feed point. The input signal is directly excited to the patch 2 and the patch 1 is fed from patch 2 by coupling between two patches. The antenna is operated at 900 MHz and 2.45 GHz bands and has the right hand circularly polarized radiation pattern at all. The measured gains of the antenna are 2.95 dBic at 900 MHz band and 4.6 dBic at 2.45 GHz band.

본 논문에서는 UHF 대역 수동형 RFID 태그 안테나의 최적 설계에 필요한 요소들과 전파 음영 문제를 최소화 할 수 있는 다중 리더 안테나 방식에 대하여 분석하였다. 또한, 칩 설계시 RCS 특성이 우수한 칩 임피던스 범위를 설정해 보았으며, 등방성 방사패턴을 갖는 태그 안테나의 필요성과 설계 예를 보였다.

In this paper, small sized half-wavelength circular loop antenna which attached beneath a visor of helmet is designed and fabricated at the resonant frequency of 449MHz. To reduce the size of the antenna, double series-shorted stubs are inserted inside the loop for practical use of a vacant space of loop inside. Also, It is designed for the printed type to install the helmet easily. The size of antenna on helmet is reduced to 87.75%(diameter : 70mm, height :.36mm) compare with general type antenna(diameter : 200mm height 101mm). The return loss, -10dB bandwidth and gain are -13.2dB, 17.6MHz(3.9%), and -1.78dBd. And, radiation pattern is omni-directional pattern at H-plane. Therefore, it can be seen that the half-wavelength circular loop antenna using double series-shorted stubs is proper structure for the miniaturization and the installed antenna of the helmet.

This paper presents the design of a novel small and wide band planar inverted F-antenna which simultaneously covers GSM900/GPS/DCS1800/DCS1900/DMB service. The proposed antenna consisting of a main patch with rectangular slit, strip 1 and strip 2, occupied the total volume of.$15\times36\times6mm^3$. A very wide impedance bandwidth characteristic was achieved by optimizing both the distance between the feed line and short strip and the length of rectangular slit on the main patch. The commercial electromagnetic software, CST Microwave Studio, is used to design the structure. The maximum gains at the frequencies of 900, 1575, 1800, 1900, and 2600 MHz were 2.07, 1.07, 1.69 and 0.55, -1.99 dBi, respectively. The overall shape of the radiation patterns is suitable for mobile communication application.

In this paper, we verify that the bandwidth of the optimized disk-loaded monopole antenna with electromagnetically coupled feed obtained using a genetic algorithm is broader than the theoretical bandwidth limit of 2/Q by simulation as well as by measurement. The measured bandwidth of the optimized antenna (kr : 0.599) is about 42% from 380 MHz to 580 MHz (VSWR<5.8). The efficiency measurement of the antenna is over 90% for the frequency band of operation.

In this paper, a novel compact microstrip-fed antenna with band-rejection characteristic for wideband applications is proposed. By cutting an L-shaped notch on the radiation patch, the wideband property for the proposed antenna is achieved. In addition, a C-shaped slot is introduced to obtain the band rejection operation of the antenna. The antenna, with very small size of $15.5\times21 mm^2$ including the ground plane, operates over 3.08 to 10.97 GHz and has the rejection band of 5.03 to 5.91 GHz for $S_{11}$ < -10 dB.

In this paper, four-element MIMO(Multi-Input Multi-Output) antenna operating at 5.2GHz and 5.8GHz is proposed. Each antenna element is fabricated by using inverted-L type and the isolation characteristic among antenna elements is adjusted by the distance between radiation element and ground. The designed array antenna has the impedance bandwidth at 5.15$\sim$5.35 and 5.725$\sim$5.825GHz for VSWR$\leq$3 and the isolation characteristic less than -20dB at same frequency.

The characteristics of the tag antenna are influenced much with the change of the electrical properties of its substrate material, conducting metal-line and the surrounding environments. In this paper, we study the characteristics of tag antenna according to the electrical variations of those substrate materials, metal-line and the surrounding environmental conditions.

We investigated the impedance matching characteristics of UHF-band RFID tag antenna and tag chip for increased reading range. A voltage multiplier designed using 0.4 $\mu$m zero-$V_T$ MOSFET showed that DC output voltage of about 2 V can be obtained using standard CMOS process. The input impedance of the voltage multiplier was examined to achieve impedance matching to the RFID tag antenna using analytical and numerical approaches. The input impedance of the voltage multiplier could be varied in a wide range by selecting the size of MOSFET and the number of multiplying stages, and thus can be impedance matched to a tag antenna in presence of other tag circuit blocks. A meander line inductively-coupled RFID tag antenna operating at UHF band also shows the feasibility of impedance matching to tile RFID tag chip.

This paper presents the characteristics of antenna factors for sleeve dipole antennas with a broad bandwidth. The coupled integral equations for the unknown current distributions on each elements are derived and solved by applying Galerkin's method of moments. The flatness of antenna factor is considered. with variation of the length and number of sleeve elements.

Two planar inverted-F antenna (PIFA) arrays are proposed as an alternative model to generate input and radiation characteristics of two orthogonal oriented circular loops, which has polarization diversity, but inherent mechanical instability of two orthogonal loops, in particular, in installation and operation conditions. Two $1\times2$ PIFA sub-arrays are orthogonally placed on a ground plane and two different feeding networks are applied to control horizontal and vertical radiation current flows for each sub-array, respectively. Equivalence of scattering parameters and radiation patterns between two antennas are validated by the available commercial simulator.

This paper presents the design of linear and circular polarization baseball- shaped circular microstrip antenna (BCMA) with 3-dimensional structure using perturbation effect to reduce its size, which runs at 1.575GHz frequency bandwidth. As a result, the size of linear polarized antenna could be reduced up to 23.7% in patch diameter and 41.8% in its area. Linear polarized antenna has -26.04dB of return loss, 69MHz(4.38%) of -l0dB bandwidth, 4.51dBd of gain, and its -3dB beamwidth are 99$^{\circ}$ in E-plane, 83$^{\circ}$ in H-plane. Circular polarized antenna has -17.43dB of return loss, 113.7MHz(7.2%) of -l0dB bandwidth, 2dBd of gain, 2dB of axial ratio and its -3dB beamwidth are 87$^{\circ}$, 86$^{\circ}$ x-axis polarized, 80$^{\circ}$, 84$^{\circ}$ y-axis polarized. It has 82mm of diameter, which is 28.5% of linear polarized CMPA. Therefore, in this paper we verified that baseball-shaped 3-dimensional structure of circular microstrip patch antenna applied with perturbation effect is appropriate for miniaturization.

Right hand circularly polarized Ka band microstrip patch array antenna was designed, manufacture and measurement were carried out. In order to lower axial ratio performance sequential rotation array technique was used. With mono-pulse feed There are sum and delta channel. Waveguide to microstrip transition was used. The 512 array antenna was performed which axial ratio is about 1.ldB in the half power beam width and also 1.ldB at the normal direction. Directivity gain of designed antenna is 32dB.

In this paper, a CPW-fed monopole antenna using inverted L-type DGS structures is proposed and investigated experimentally. The proposed antenna is fabricated into FR4 substrate with dielectric constant($\varepsilon$r=4.5). Measured results show that the impedance bandwidth, determined from 10-dB return loss, for frequencies between 5.7250Hz-5.825CHz under the condition of VSWR$\leqq$2 is about 540MHg.

In this paper, the broadband FCMA(Folded Cross Monopole Antenna), which is the cross monopole antenna with the folded element, is presented. To investigate the broadband characteristics of FCMA the VSWR, the gain, and the radiation pattern are calculated in frequency between 1.75 GHz and 2.655 GHz. From the calculated result, it is shown that the presented folded cross monopole antenna has a excellent band characteristics than the existing cross monopole antenna. The presented antenna is conformed as a broadband antenna which can be used for the indoor antenna of PCS, WCDMA, Wibro, and satellite DMB band.

In this paper, an active antenna for terrestrial DMB(Digital Multimedia Broadcasting) repeater is designed. This active antenna is consist of receiving antenna and LNA(Low Noise Amplifier), A receiving antenna fed by using a microstrip line and radiation part is designed with rectangular spiral structure. An receiving antenna with frequency range of 162$\sim$212MHz, gain of -10dBi and LNA with gain of 20dBi, noise figure of 2.2 at frequency range for T-DMB are achieved.

Synthetic Aperture Radars(SAR) are used mainly for high-resolution imaging of the terrain. This paper describes the 16$\times$16 array antenna designed for an X-band, automobile-based SAR(AutoSAR) system. This antenna has the structure of several layers such as radome, radiators, slots, feed network, and honeycomb cores. Each layer is adhesively bonded to meet different combination of structural and electrical design requirements. Using the Strip-Slot-Foam-Inverted-Patch(SSFIP) structure and dogbone slots, a wide bandwidth and a structural hardness were achieved. Measurement results were compared with simulation results. It was observed that the SAR antenna had a bandwidth of 1.7 GHz, side-lobe levels of less than -20 dB, half-power beamwidth of 5$^{\circ}$, and gains of 25.0 dBi. The observed results show that the designed array antenna is suitable for the broadband AutoSAR system.

The paper describes a meander antenna using magneto-dielectric composite for 433.92 MHz band. The antenna with magneto-dielectric material in this paper is suggested for miniaturization of antenna size. The return loss of meander antenna is achieved by optimizing the permittivity, $\varepsilon_r$=1.71-j0.004 and permeability, $\mu_r$=2.39+j2.58. Over all dimension of the antenna is $51\times11\times1.6mm$. The return loss and gain are -41 dB, -5dBi, respectively at 433.92 MHz.

In this paper, the characteristics of linealy bent wire antennas are first analyzed for shortening straight wire antennas. The results are appropriately applied to the design of the integrated zigzag dipole antenna. Since the integration give rise to discontinuities due to line width, the integrated parasitics are properly attached to both sides of substrate for improving the antenna gain and return loss. The design results are verified with experiments.

본 논문에서는 셀룰라 통신대역, WiBro 통신과 WLAN(IEEE802.llb/g)통신, 5GHz대역 WLAN(IEEE802.lla) 통신에 사용될 삼중대역 평면형 모노폴 안테나를 설계하였다. 안테나의 크기를 줄이기 위해 저역과 중역 방사소자를 구부리고, 필요한 대역폭을 얻기 위해 방사소자 폭을 증가시켜 여러가지 형태의 안테나를 설계하고 실험적으로 고찰하였다. 제작된 안테나의 방사특성(대역폭과 방사패턴)은 HFSS로 계산된 것과 유사한 특성을 가지고 안테나 크기는 11% 감소되고 대역폭은 800MHz대역에서 30%$\sim$40% 증가되었다.

Radiation properties of flush mounted circular patch antenna are investigated. The patch is fed axis-symmetrically by a coaxial cable. Rigorous analysis is given using integral transform and mode matching techniques. The presented method accommodates radiating patch, and integrated matching sections and band pass filter.

Scan Element Pattern(SEP) and Scan Impedance(SI) concepts are used to analyze the characteristics of open-ended waveguide array, which is the representative phased array antenna element in C-band and X-band. Transmit SEP's are calculated for 15$\sim$15 subarray and SI's are obtained by applying periodic boundary conditions for a unit cell of the given array condition. CST's MWS and Ansoft's HFSS are utilized for each analysis. Some relations are reviewed between the two results, which are based on mutual coupling effects. For validation purpose, an 8$\sim$8 subarray is constructed and tested. Transmit SEP measured in MTG's far-field range shows good agreement with the calculated transmit SEP.

There have been many researches on the antenna performance degradation with the presence of the human body around the antenna structure to accomodate personal communication service [1][2]. To better understand the human body effects on the antenna resonance, radiation pattern, and input impedance, simulation was carried out with changing of the distance between antenna and lossy material. Effects on the antenna performance by the surrounding materials are also important in the case of the RFID system. It is desirable that the tag antennas for RFID system must reveal isotropic radiation pattern as well as attain the good impedance matching. In this paper, we investigated the antenna resonance and input impedance characteristic when there exist a lossy material sphere near various types of antenna at 900 MHz. In short antenna resonance was mostly affected by lossy material in the case of a rectangular loop antenna, and impedance variation was smallest in the case of a halfwave dipole.

In the synthesis of the continuously distributed line source antennas with arbitrary patterns, the formulas of Taylor sum pattern and Bayliss difference pattern have been mainly used. In this paper, an optimization scheme is newly presented to directly synthesize the desired difference patterns from Taylor line source formula, and then the distributions are numerically adapted to the specified difference patterns by using an appropriate iterative sampling method.

In this paper, a modified multimode hem antenna is designed to have 142 mm horn aperture radius and 921 mm length in order to be safe under 100 MW peak pulse power at 3 cm wave length through breakdown phenomenon study that threshold field strengths for the air breakdown phenomena is decided to be 3.78 MV/m. The proposed antenna is measured gain over 27 dBi and the -25 dB beam width of 29$^{\circ}$ in vertical plane.

In this paper, we made a Singly Fed patch which is the fittest at the feeding part. And we found out return loss and radiation pattern about dielectric rod array antenna which has six's passive element to shape FTEP(Flat-topped element pattern) after we analyzed the characters of singly dielectric rod antenna. We show the conclusion that has the optimum return loss and more flat radiation pattern.

This paper presents the design and fabrication of a cost effective and broad band 8$\times$8 stacked patch array antenna which are backed by a metal cavity operating at 400Hz based on 4 layers LTCC technology. Gain of antenna can be enhanced by using a metal cavity, which can be easily implemented by using LTCC substrates and vias. The broadband performance can be obtained by varying the dimension of patch and the number of layers. Furthermore, to keep the feeding network as smal1 as possible and reduce radiation from feeding network a mirrored patch orientation and embedded micro strip line are adopted, The fabricated antenna is $40\times45\times0.4$ $mm^3$in size. It shows gain 20.4dBi, beam width 10.7deg and impedance bandwidth of l0dE return loss 3.35GHz (40.9$\sim$44.25 GHz), which is about 8% of a center frequency.

In this paper, We studied an antenna for the wireless home network service. From the structural modification of patch and ground plane, we made a reverse heart shape radiated pattern of antenna which is suited to wireless home network service. As a result, bandwidth between maximum gains is 110 degree, and the difference of downward direction gain from maximum gain have become -3.6dB. Installing the antenna on the ceiling, horizontal plane of the inner home will be formed the uniform electromagnetic environment. Accordingly, stable reception level acquisition and outdoor radiated suppression could be possible.

If obstacle in GIS(Gas Insulted Switchgear), its affects are great are on the community and it is consequently demanded lots of difficulties to recover and repair. Accordingly, diagnosis techniques, that are able to prevent from accidents before they happen by providing more stable and highly reliable power effectively and finding sign of the accidents is very important A novel UHF(Ultra High Frequency)-microstrip antenna is presented. The measured impedance bandwidth of the proposed antenna is from 0.5[GHz] to 15[GHz] with the stop band from 0.5[GHz] to 10.7 [GHz] for VSWR<2. Form results of this study, The antenna is will play an important role for the sensor for insulation diagnosis system by UHF method of real site GIS and power equipment using SF$_6$ gas.

In this paper, we studied a new concept of wireless LAN service. Current service for wireless LAN has some weak points such as occuring a frequency shadowed area, high cost for setting a number of APs, electromagnetic interference by means of a large output transmission and weak security issues. To reduce those problems, we proposed setting antennas which are from one AP for each rooms, and designed a suitable antenna. After that we measured a PMA(Propagation Measurement & Analysis). Experimental results showed that a new concept of wireless LAN service is excellent to resolve interference and weak security issues by minimizing external propagation of a building.

본 연구에서는 미약무선국의 전계강도(기술기준)에 대한 현재 각국의 동향과 그 기준치를 연구 분석하고, 파악함과 동시에, 또한, 전자파적합등록에서 제시하고 있는 각국의 전계강도 기준치와 연계하여 이에 적합한 국내의 비허가 무선기기(미약무선기기)의 실질적인 도입 가능한 전계강도의 기준치를 제시함을 목적으로 한다. 여기에서 제시한 전계강도 허용치를 바탕으로, 미약무선기기의 보급과 발전에 기여할 것으로 예상되며 국내통신시장은 물론 국제통신시장에서 경쟁력을 갖출 수 있을 것으로 예상된다.

본 논문에서는, PIFA 끝 부분을 접은 DMB 차량용 폴디드 PIFA를 제안한다. PIFA의 단락스트립 반대편 끝 부분을 접음으로써 1/4 파장이 아닌 1/10 파장에서 공진 주파수가 형성된다. 이는 PIFA에 비해 60 % 정도의 안테나 크기 축소 효과를 가진다. 또한 기생패치를 사용했을 때 폴디드 PIFA는 대역폭이 늘어난다. 따라서 제안된 안테나는 차량용 지상파 Digital Multimedia Broadcasting (DMB) 안테나로 응용이 가능하다.

The GFSK Transceiver of 400MHz ISM band for data communication is designed and fabricated. To reduce the occupied bandwidth of transmitted signal, the GFSK modulation is selected. The measured results of fabricated transceiver show the data rate of 2400bps at 8.5kHz bandwidth, frequency deviation of less than $\pm$3kHz, sensitivity of -111dBm, SNR of 21.58dB. The fabricated transceiver is satisfied with the regulation of radio wave and has the good performance. This transceiver is well suited for data communication of 400MHz ISM band.

본 논문에서는 최근 CISPR(국제무선장해 특별위원회: International Special Committee on Radio Interference)에서 논의된 1 GHz 이상 주파수 대역의 방사 장해 전자파 측정을 위한 시험방법에 대해서 설명하고, 측정 안테나의 $\theta_{3dB}$ 특성에 따른 w(측정 범위)에 대해 설명하였다. 또한 1 GHz 이상 주파수 대역에서의 측정법 및 한계치에 대한 IEC 규격 개정 상황을 설명하였다.

To construct an anechoic chamber for EMI test satisfying some international standards, it has been recognized that the absorption characteristics of the EM wave absorber must have more than 20 dB over the frequency band from 30 MHz to 18 GHz. In this paper, an EM wave absorber with super wide-band frequency characteristics was proposed and designed in order to satisfy the above requirements by using the EMCM[1]. As a result, the proposed absorber has absorption characteristics more than 20 dB over the frequency band from 30 MHz to more than 20 GHz.

X-ray is currently most effective method in detecting small malignant breast tumors but has the several problems due to suppressing breast, ionizing radiation and not detecting small cancer. In this paper, a new method is proposed by using dielectric characteristics of pathological tissues and time delay of backscattered response. We have developed a detection algorithm and verified it by numerical simulation and measurement for a prototype system. For a prototype system, we have fabricated experimental model(artificial breast with a cancer) and UWB(ultra-wideband) antenna. The results of the measurement simulation show an excellent detection capability of a cancer tissue. It is found that a good UWB antenna is a key element of such detection system. Further study is ongoing to develop a commercial system.

A variety of wireless devices are commercially available now. Most of studies, however, have been directed to the biological effects of mobile-phone EMF. In this study, dosimetric analysis for wireless devices of head-mounted display type and a wristwatch type were made to investigate possible biological effects of these devices. SAR (Specific Absorption Rate) distributions were calculated using FDTD (Finite Difference Time Domain) method, for adult human models such as standard Korean human model and VHP(Visible Human Project) model, as well as scaled models. Measurements were also performed for SAM phantom wearing a simplified prototype for a wireless device for validation of the simulation results. It has been found that children are more vulnerable to such exposure, and these devices could cause some biological effects for relatively lower power compared to conventional mobile pones.

This paper investigates how the PCB power-bus structure's characteristics are influenced by the loading of decoupling capacitors that are placed close to vias, on purpose or not. It is worthwhile to see the correlated effects of the aforementioned lumped elements in that when they inevitably share one DC power-bus they will result in positive or negative changes in the PCB EMC design. The EM fields and impedance profiles are rigously calculated on the PCB power-bus cases loaded with the above components and their effects will be given to bring better PCB EMC countermeasures.

This paper presents the reduction methods of penetrated electromagnetic fields through a narrow slot aperture in a planar conducting screen of infinite extent. When a plane wave is excited to the narrow slot, the aperture electric field is controlled by the resistive sheets loaded on the slot. The magnitude of penetrated electromagnetic fields through a narrow slot is controlled by electric field distributions on the slot aperture. The results show that the magnitude of the penetrated electromagnetic field can be effectively reduced by the resistive sheets on the slot aperture.

This paper deals with the measurement and analysis of radio characteristic of 424 MHz for using the automation of transmission and supply of electric power, ana automatic meter reading(AMR). Normally radio propagation characteristic is the base of system design, performance evaluation and choice of position of the base station in wireless communication. It is the most accurate way to design a base station through practical measurements, but it costs much time, money and engineers. So, we developed 424 MHz short range wave propagation model for AMR service.

The SAR measurement system with stationary probes, presented in this paper, can calculate area SAR value based ell the measured 9 electric field data. By converting obtained area SAR to the volume SAR, the results can be acquired in a few seconds. The system can be very useful tool in the stages of handset development for mobile communication as well as in the handset production line because of its rapid SAR measurement. The system showed good linearity characteristics at 835 MHz of 10 $\sim$ 27 dBm input power range.