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This study aims to investigate and assess salivary biomarkers and microbial profiles as a means of diagnosing periodontitis. A total of 121 subjects were included: 28 periodontally healthy subjects, 24 with Stage I periodontitis, 24 with Stage II, 23 with Stage III, and 22 with Stage IV. Salivary proteins (including active matrix metalloproteinase-8 (MMP-8), pro-MMP-8, total MMP-8, C-reactive protein, secretory immunoglobulin A) and planktonic bacteria (including Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas nigrescens, Parvimonas micra, Campylobacter rectus, Eubacterium nodatum, Eikenella corrodens, Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis, and Actinomyces viscosus) were measured from salivary samples. The performance of the diagnostic models was assessed by receiver operating characteristics (ROCs) and area under the ROC curve (AUC) analysis. The diagnostic models were constructed based on the subjects&rsquo, proteins and/or microbial profiles, resulting in two potential diagnosis models that achieved better diagnostic powers, with an AUC value &gt, 0.750 for the diagnosis of Stages II, III, and IV periodontitis (Model PA-I, AUC: 0.796, sensitivity: 0.754, specificity: 0.712) and for the diagnosis of Stages III and IV periodontitis (Model PA-II, AUC: 0.796, sensitivity: 0.756, specificity: 0.868). This study can contribute to screening for periodontitis based on salivary biomarkers.

Low-frequency noise (1/f noise) has been analyzed to characterize the amorphous/crystalline silicon heterojunction diodes with passivation layer of a-Si:H (p–i–n), Al2O3 (p–Al2O3–n), and ZnO (p–ZnO–n) and without passivation (p–n). Four types of diodes show high ideality factors and the dependence of the reverse leakage current on the electric field shows that the diodes commonly follow the Poole–Frenkel model, which is field-assisted thermionic emission from the traps in the materials. However, the conduction mechanism in the reverse bias can be more easily clarified from the bias dependence of the 1/f noise. That is, the p–i–n and p–n diodes are affected by the diffusion current mechanism, and the p–Al2O3–n and p–ZnO–n diodes with an inferior interface are affected by the generation–recombination current mechanism. This indicates that the p–i–n and p–n diodes have a better interface quality than the p–Al2O3–n and the p–ZnO–n. These results show that the 1/f noise measurement can be a useful and more sensitive method to estimate the interface quality of heterojunction diodes.

This paper presents a beamforming-based Korea LoRa band (i.e. 920 - 925MHz) wireless power transmitter and receiver chain for IoT/M2M applications. To complete wireless power harvesting, major key elements are: First one is a 6-bit active phase shifter to improve directivity between sensor-node and master-node using beamforming. The other one is an RF to DC converter to rectify RF and achieve the battery charging voltage. To reduce a phase error of active phase shifter because an IQ phase imbalance, an IQ phase calibration technique that maintaining the 1 of Q-factor is used. In addition, to improve the RF power harvesting distance, the rectifier is designed with a resonating single to differential (S2D) matching network for getting higher DC voltage than the RF input peak voltage. As the Q-factor of active phase shifter maintains 0.98 - 1.03, the maximum phase error is approximately 1.5deg for -10 to 100 temperature. The minimum input power that can be harvested is about -13dBm from EIRP 26dBm, 915MHz. The minimum output voltage of the boosted rectifier is 0.8V from -13dBm input. The RF to DC converter output voltage range is 3.0 to 5.5V. The maximum RF to DC power conversion efficiency is about 55% from 4 to 6dBm input.

This paper present a 5.9 GHz dedicated short range communication (DSRC) transmitter for wireless vehicular communication that satisfies specification of IEEE 802.11p standard mask c. The proposed transmitter consists of programmable gain amplifier (PGA), up-conversion mixer, drive amplifier, and synthesizer. Passive mixer, push-pull local oscillator (LO) buffer, and intermodulation distortion (IMD) canceller are applied to achieve high linearity and low power consumption. The transmitter is designed and fabricated on CMOS 0.18 μm process. The total power consumption is 63 mA at 1.8 V. A phase noise of synthesizer is −109.4 dBc/Hz at 1MHz offset. The transmitter total noise figure (NF) and adjacent channel leakage ratio (ACLR) are 14.2 dB and − 53.6 dBc, respectively.

In this study, an n-ZnO/p-Si heterojunction diode with embedded Ag nanoparticles was fabricated to investigate the possible improvement of light trapping via the surface plasmon resonance effect for solar cell applications. The Ag nanoparticles were fabricated by the physical sputtering method. The acquired current-voltage curves and optical absorption spectra demonstrated that the application of Ag nanoparticles in the n-ZnO/p-Si interface increased the photo current, particularly in specific wavelength regions. The results indicate that the enhancement of the photo current was caused by the surface plasmon resonance effect generated by the Ag nanoparticles. In addition, minority carrier lifetime measurements showed that the recombination losses caused by the Ag nanoparticles were negligible. These results suggest that the embedding of Ag nanoparticles is a powerful method to improve the performance of n-ZnO/p-Si heterojunction solar cells.

The performance of concrete structure decreases with change in time and the external environment . In order to reinforce the structure, the research about new material development and application of newly developed materials are widely conducted. In the case of composite FRP, it received good attention in the academia due to its high intensity-weight ratio, excellent corrosion resistency as well as good workability. When applying at the construction field, however, the utilization of FRP did not increase as much due to lack of reliability and design standard. Current study investigated the material characteristics during the temperature change at high temperature and the structural behavior from restraint effect for GFRP reinforcing materials. Two experimental variables were set in this study: GFRP reinforcements due to tensile properties of temperature and restraint compression effects. Three concrete specimen were selected for each set temperatures..For this reason, as a variable to experiment with the effects confined compression concrete members value and tensile properties with temperature reinforcement GFRP, experiment produced three pieces each for each set temperature, the concrete specimen, which is confined in the GFRP was selected each I did. For the temperature change during the experiment, the concrete specimen were mounted in order to expose to experimental high temperature for certain period of time. For compression performance evaluation, reinforcement effect from horizontal constraint of the fiber were measured using an Universal Material Testing Machine (UTM). Finally, this study revealed that the binding characteristics of GFRP materials from temperature change decreased. Also, this study showed that the maximum compression intensity decreased as the temperature increased up to 150℃ in the constraints ability of the GFRP reinforcements during the horizontal constraint of concrete.

A compact bandpass filter (BPF) using a very short capacitively coupled resonator exhibits wide-stopband characteristics. It is based on two

This paper presents load modulator based on the six-port modulator. To allow arbitrary load impedances to be used, a new circuit architecture with a technique to design the high resolution impedance is proposed and implemented. A theoretical model of the proposed modulator is derived. A 0.13-µm CMOS modulator utilizing MOSFET for impedance generation is designed and fabricated for a center frequency of 1.84 GHz for MIMO system. Measurements show good modulation properties when a 64 quadrature amplitude modulation signal is generated.

As increasing number of large-size earthquake around Korean peninsula, many interests have been focused to the earthquake strengthening of existing structures. Fiber reinforced plastic composite material is one of strengthening material widely used to increase seismic performance of structures. It should have high stiffness as well as large ductility to provide best strengthening result. Thus selection of stiffener and fiber in composite is of important. In this study, the optimal combination of fiber and stiffener is selected with variety of tensile tests. In order to investigate performance of chosen composite material, several finite element analyses are performed with proposed FRP composite material for existing RC columns. It is discussed that the seismic performance of strengthened columns through the load-displacement relationship. It is shown that the proposed composite material can increase the strength as well as ductility of exiting RC columns.

A broadband suspended substrate filter is proposed and implemented using dual-mode resonator aiming at transmitting the signals in the passband of 10–18 GHz. It is composed of two quarter-wavelength resonators and inductor. The inductor is a short-circuited stub. After optimization of this filter, a good bandpass behavior with 10 transmission poles is theoretically realized and experimentally confirmed. Within the whole BPF passband, the return loss is found better than 10 dB, and the insertion loss is less than 1.9 dB. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26070

The latest study for formulation of finite element method and computation techniques has progressed widely. The classical method in the formulation of frame elements for geometrically nonlinear analysis derives the geometric stiffness directly from the governing differential equation for bending with axial force. From the computational viewpoint of this paper, the most common approach is the finite element method. Commonly, the formulation of frame elements for geometrically nonlinear structures is based on appropriate interpolation functions for the transverse and axial displacements of the member. The formulation of flexibility-based elements, on the other hand, is based on interpolation functions for the internal forces. In this paper, a new method is used to suppose that interpolation functions for the displacements from the curvatures is Lagrangian interpolation. This paper derives flexibility matrix from that displacement functions and is considered the application of it. Using the flexibility matrix, this paper apply the program considered geometrically nonlinear analysis to common problems.

This study is to develop nonlinear analysis algorithm for transfer matrix method, which can be applied to continuous beam analysis. Gauss-Lobatto integral rule is adopted and the transfer matrix is derived from stiffness matrix. In the transfer matrix method, the system equation has a constant number of unknowns regardless of number of D.O.F. Therefore, the transfer matrix method has computational efficiencies not only in linear elastic analysis but also in nonlinear analysis. To verify the developed method, the analysis results of several examples are compared with commercial code in moment-curvature, moment-displacement and load-displacement relation.

A CMOS transceiver is designed and fabricated for implantable cardioverter telemetry service. For the image rejection, a complex filter is used in the receiver instead of the conventional image rejection mixer type. Low power consumption is essential for the implantable medical service, thus the RF blocks such as the low noise amplifier, voltage controlled oscillator, and frequency synthesizer are designed by focusing on the low power operation. The transceiver is implemented in 0.18-µm CMOS process, and operates with a single 1.8-V supply. The sensitivity is −85 dBm. The phase noise characteristic of frequency synthesizer is −87 dBc/Hz at 10 kHz offset frequency. Maximum output power of the transmitter is −2.8 dBm. The transceiver achieves 500 kbps maximum data rate with 22 mW power consumption. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2580–2582, 2014

The purpose of this thesis is to analyze and test hypotheses that the internet shopping customer`s satisfaction would be differences between customer`s lifestyle and a type of buying product characteristics. In addition, this study tested differences between lifestyle groups and product type in terms of customer`s transaction continuity. In result, we find that there are significant differences of customer`s satisfaction and customer`s continuity in terms of the lifestyle, but not in the product types. This study provide useful informations on market segmentation strategy to the firms which had been doing on-line shopping and will help them minimize the possible risks when firms enter into internet shopping market.

A chromel-alumel thermoelectric flow sensor using thermal isolation membrane was fabricated. Temperature coefficient of resistance of thin film Pt-heater was about , and Seebeck coefficient of chromel-alumel thermocouple was about . The sensor showed that thermoelectric voltage decreased as thermal conductivity of gas increased, and -flow sensitivity increased as heater voltage increased or the distance between heater and thermocouple decreased. When heater voltage was about 2.5 V, -flow sensitivity and thermal response time of the sensor were about and 0.18 sec., respectively. Linear range in flow sensitivity of the flow sensor was wider than that of Bi-Sb flow sensor.

NiCr-heaters with three different thicknesses ranging from 400 nm to 800 nm were fabricated and their characteristics were compared for the purpose of developing a chromel-alumel multijunction thermal converter for low input voltage with low frequency. The thermoelectric effect-induced AC-DC voltage transfer difference of the thermal converter with a built-in NiCr-heater of 400 nm-thickness was in the DC reversing frequency of with appling and the difference was increased to in the frequency of , when both thermoelectric effects and frequency effects were considered, showing the thermal converter would be suitable for the low input voltage application with low frequency.

A planar Bi-Sb multijunction thermal converter was fabricated on the LPCVD Si/sub 3/N/sub 4//SiO/sub 2//Si/sub 3/N/sub 4/-diaphragm, prepared by silicon bulk micromachining, which thermally isolated a bifilar Pt- or NiCr-heater and the hot junctions of a Bi-Sb thermopile from the silicon substrate. The voltage responsivity, the ac-dc transfer difference, and the fluctuations of the output thermoelectric voltage and heater resistance were discussed to investigate the design factors of a thermal converter. The respective voltage responsivities in air and in a vacuum of the thermal converter with a built-in NiCr-heater were about 14.0 mV/mW and 54.0 mV/mW. The ac-dc voltage and the current transfer differences in air were about /spl plusmn/0.60 ppm and /spl plusmn/0.11 ppm in the dc reversing frequency range from 10 Hz to 10 kHz. They are sufficiently small to be used as practical ac standards. Compared to the thermal converter with a built-in Pt-heater, the thermal converter with a built-in NiCr-heater demonstrated a higher voltage responsivity and smaller ac-dc transfer differences, while exhibiting slightly larger fluctuations in output thermoelectric voltage and in heater resistance.

Discovery of biomarkers in peripheral blood is a crucial step toward the early diagnosis and repetitive monitoring of treatment response for Alzheimer's disease (AD). Metabolomics is a promising technology that can identify unbiased biomark- ers. To explore potential blood biomarkers for AD via metabolic profiling with high-resolution magic angle spinning nuclear magnetic resonance techniques, we identified changes in peripheral blood metabolomic profiles in response to amyloid- (A)- induced neuroinflammation and co-treatment with gallate, a phytochemical known to have anti-neuroinflammatory properties. Alzheimer's-like (AL) model mice were produced by intracerebroventricular infusion of A and compared with normal control mice with infusion of vehicle. AL mice were treated with either gallate (treated AL mice) or vehicle (untreated AL mice). Metabolomic analyses of both whole blood and plasma showed a clear separation between untreated AL mice and the other two groups, with levels of several metabolites involved in energy metabolism, including pyruvate and creatine, being signifi- cantly reduced in untreated AL mice compared with control and treated AL mice. Gallate treatment suppressed A-induced overproduction of the inflammatory cytokine tumor necrosis factor- in the hippocampus and normalized plasma levels of the affected metabolites. These results suggest that plasma levels of several metabolites could be indicative of both brain pathology and therapeutic responses, supporting the possibility of a close relationship between central neuroinflammation and systemic metabolic disturbance. These findings also suggest the potential of NMR-based metabolomics as a method to identify novel plasma biomarkers for AD, which could be confirmed by future translational research with human patients.

This paper presents the first experimental results of a piezoresistive silicon accelerometer with eight beams fabricated by a unique silicon micromachining technique using selective porous-silicon etching. This technique is capable of precisely constructing a microstructure without any lateral etching or undercutting. By the use of this eight-beam structure, the mechanical strength of the accelerometer can be highly improved due to smaller shear stress. The lower sensitivity of the sensor can be simply solved by combining the four output signals of the half-bridge. The effectiveness of the sensor is confirmed through an experiment in which the accelerometer is characterized.

A metabolomic analysis was performed to examine the postharvest processing of Astragalus membranaceus roots with a focus on the peeling procedure using (1)H NMR and UPLC-MS analyses. Principal component analysis (PCA) score plots from the (1)H NMR and UPLC-MS data showed clear separation between peeled and unpeeled Astragalus roots. Peeled roots exhibited significant losses of several primary metabolites, including acetate, alanine, arginine, caprate, fumarate, glutamate, histidine, N-acetylaspartate, malate, proline, sucrose, trigonelline, and valine. In contrast, the peeled roots contained higher levels of asparagine, aspartate, and xylose, which are xylem-related compounds, and formate, which is produced in response to wound stress incurred during postharvest processing. In addition, the levels of isoflavonoids and astragalosides were significantly reduced in peeled Astragalus root. These results demonstrate that metabolite profiling based on a combination of (1)H NMR and UPLC-MS analyses can be used to evaluate peeling procedures used in the postharvest processing of herbal medicines.

High-fat diets (HFD) and high-carbohydrate diets (HCD)-induced obesity through different pathways, but the metabolic differences between these diets are not fully understood. Therefore, we applied proton nuclear magnetic resonance (H-1 NMR)-based metabolomics to compare the metabolic patterns between C57BL/6 mice fed HCD and those fed HID. Principal component analysis derived from H-1 NMR spectra of urine showed a clear separation between the HCD and HFD groups. Based on the changes in urinary metabolites, the slow rate of weight gain in mice fed the HCD related to activation of the tricarboxylic acid cycle (resulting in increased levels of citrate and succinate in HCD mice), while the HFD affected nicotinamide metabolism (increased levels of 1-methylnicotineamide, nicotinamide-N-oxide in HID mice), which leads to systemic oxidative stress. In addition, perturbation of gut microflora metabolism was also related to different metabolic patterns of those two diets. These findings demonstrate that H-1 NMR-based metabolomics can identify diet-dependent perturbations in biological pathways. [BMB Reports 2012; 45(7): 419-424]

To test the hypothesis that urinary metabolites characterizing heart failure (HF) are associated with the magnitude of echocardiographic measurements and ultimately the severity of HF.Patients with systolic HF (n=46) and control subjects (n=32) participated in this study. Patients with type 2 diabetes mellitus were excluded. Echocardiographic measurements were performed, and selected urinary metabolites were quantified.Urinary levels of acetate (p0.05), acetone (p0.01), cytosine (p0.001), methylmalonate (p0.001), and phenylacetylglycine (p0.01) were significantly higher, while 1-methylnicotinamide (p0.05) were significantly lower in HF patients than in controls. There were significant differences in E/E' (p0.05), urinary levels of acetate (p0.005), acetoacetate (p0.05), acetone (p0.05) and ketones (p0.01) according to the New York Heart Association (NYHA) classification in HF patients. Multiple linear regression analysis revealed that urinary ketones were found to be independent factors for both left ventricular ejection fraction and E/E' after adjusting for confounders.Our results showed that urinary levels of ketone bodies are associated with the magnitude of echocardiographic parameters.

This paper presents a low-power front-ended 24 GHz receiver resistive mixer and buffer amp, which were fabricated using 0.13 μm RF CMOS technology for application to automotive radar. For resistive receiver mixer, single-ended resistive mixer was designed for high linearity characteristic and low power consumption. According to measured results, the proposed resistive mixer showed an improved linearity and low power consumption characteristic. At 24 GHz, the resistive receiver mixer showed a conversion loss of −9 dB and an input 1-dB gain compression point of −1 dBm at a low bias voltage of 0.3 V. The buffer amplifier showed a gain of 4.5 dB at 24 GHz.

This paper investigates the effect of acoustic stimulation on natural convection heat transfer in micro-scale fin structures. Enhancement of heat transfer from electronic components enclosed within compact geometries is a key goal in thermal management. Among the techniques to enhance heat transfer, extended surface is a simple approach to achieve the goal. However, micro scale fin heat sinks have little effect on natural convection heat transfer. Previous work has shown that heat transfer via flow-induced vibration in a micro fin array can be enhanced, but only in a forced convection scheme with high flow rates. Acoustic stimulation has also been investigated in boiling and we extend this method of stimulation to enhance gaseous natural convection. The acoustic stimulation is generated using a speaker placed close to the micro fin array device. Waves of varying amplitude and frequency are generated and device surface temperatures recorded along with the speaker velocities, measured using Laser Doppler Velocimetry. The results obtained suggest that natural convection heat transfer can be enhanced using acoustic stimulation in micro-scale fin structures where the fins contribute negligible effect on overall heat transfer, and the enhancement varies with fin geometries. The results indicate that gaseous natural convection is feasible as a thermal management scheme in micro fin structures for low heat flux applications. Future works will be devoted to finding the resonance frequency of natural convection in micro-scale fin structures that can enhance heat transfer dramatically with little additional power consumption.

A low-power CMOS on-off keying (OOK) transmitter employing a triangular pulse shaping scheme is presented. The proposed pulse shaping circuit is based on a current-reused common-source stage, whose gain is controlled by modulating the gate-source voltage in a triangular form. The triangular control signal is generated by an opamp-based integrator. The proposed pulse shaping scheme can effectively support variable data rate. A 3.5-GHz OOK transmitter circuit adopting the proposed pulse shaping scheme is designed in a 0.13 μm CMOS process. It successfully modulates digital data from 100 kbps to 10 Mbps and delivers an output power of +2.5 dBm. The total current consumption is 4.17 mA from a 1.2 V supply voltage, of which only 0.57 mA is dissipated at the transmitter core excluding the output buffer.

A novel broadband suspended substrate filter is proposed and implemented using dual-mode resonator aiming at transmitting the signals in the passband of 10-18 GHz. It is composed of two quarter-wavelength resonators and inductor. The inductor is a short-circuited stub. After optimization of this filter, a good bandpass behavior with ten transmission poles is theoretically realized and experimentally confirmed. Within the whole BPF passband, the return loss is found better than 10 dB, and the insertion loss is less than 1.9 dB.

A novel broadband suspended substrate filter is proposed and implemented using a shielded suspended substrate stripline (SSL), aiming at transmitting the signals in the passband of 6-10 GHz. It is composed of two quarter-wavelength resonators and K-inverter. The K-inverter is composed of two short-circuited stubs. After optimization of this filter, a good bandpass behavior with ten transmission poles is theoretically realized and experimentally confirmed. Within the whole BPF passband, the return loss is found better than 14 dB, and the insertion loss is less than 1.9 dB.

In this paper, we propose a frequency synthesizer for dual-band repeater. The dual-band RF technology for applications to the wireless repeater for CDMA and WCDMA mobile communications has been developed. The dual-band frequency synthesizer consisted of dual-band VCO and dual-band PLL IC. The main technological efforts for the dual-band a frequency synthesizer is to suppress the intermodulation distortion by applying the miniatured LTCC bandpass filter using the slow wave characteristics.

In this paper, the RF-ID tag for container management has been designed, fabricated and analyzed. The active RF-ID tag consists of Rx part, Tx part and planar inverted-F antenna (PIFA). We suggest an active RF-ID tag for container management. Also, planar inverted-F antenna useful in metal container is suggested. We have designed the RF-ID tag using EM and circuit simulation tools. According to the measured results, the transmitting power of RF-ID tag was 10mW. The frequency deviation is /spl plusmn/ 50kHz and data rate is 27.7 kbps.

In this paper, the dual-band PLL module for K-PCS and IMT-2000 mobile communications has been developed. The dual-band PLL module consisted of dual-band VCO, PLL IC and compact multi-layer bandpass filter. The main technological efforts for the dual-band PLL module is to suppress the intermodulation signals by applying the miniature LTCC filter using the slow wave characteristics.

In this paper, the SMD isolator for IMT-2000 handset is designed, fabricated and analyzed. We have designed the SMD isolator using EM simulation tool. Electrical results have improved in comparison with a conventional model. It provides an insertion loss of 0.3 dB at 1.95GHz and an isolation of 21.5 dB or more over a frequency range of 1.92 through 1.98 GHz. The dimension of the isolator is 4/spl times/4/spl times/1.8 mm.

The modulation frequency affects the asymmetric intermodulation distortion (IMD) products of a RF power amplifier. This effect reduces IMD cancellation performance of power amplifiers in connection with predistortion linearization. A phase extraction method to determine phase difference between upper and lower 3/sup rd/ order IMD products and a phase compensation circuit using an envelope injection technique is proposed. The experimental results demonstrate a significant improvement in the 3/sup rd/ order IMD cancellation performance.

This paper presents the first experimental results of a piezoresistive silicon accelerometer with eight beams fabricated by a unique silicon micromachining technique using selective porous silicon etching. This technique is capable of precisely constructing a microstructure without any lateral etching or undercutting. By the use of eight-beam structure, the mechanical strength of the accelerometer can be highly improved due to smaller shear stress. The lower sensitivity of the sensor can be simply solved by combining four output signals of half-bridge. The effectiveness of the sensor is confirmed through an experiment in which the accelerometer is characterized.

Lateral-type polysilicon field emission triode, consisting of two symmetric gate tips aligned by an angle of 70/spl deg/ with respect to the sharp cathode tips was fabricated by using local oxidation of polysilicon (LOCOS) process. The fabricated device has the electrical characteristics of a low turn-on voltage of 13 V and the emission anode current of 150 /spl mu/A/50tips at V/sub AC/ = 50 V and V/sub GC/ = open. After high field activation treatment, the turn-on voltage was down to 2 V and the emission current increased up to 525 /spl mu/A/50tips at V/sub AC/ = 50 V and V/sub GC/ = open. Furthermore, the emission current versus gate biases indicated a dramatic change of emission currents from gate tip-end resulting in an interesting operational behavior.

In this paper, an FG-CPW (Finite-Ground Coplanar Waveguide) balanced diode mixer is presented. Frequency bandwidth is selected for a C-band, which is 5.72/spl sim/5.82 GHz for RF, 5.58/spl sim/5.68 GHz for LO, and 140 MHz for IF signals. A rat-race hybrid is designed for the accomplishment of single balanced type mixers. A low pass filter (LPF) with CPW structure is used for good conversion loss and unwanted harmonics suppression. When an LO signal with the power of 4 dBm at 5.635 GHz is injected, a conversion loss of 6.2 dB is obtained for the mixer. Also, LO to RF and LO to IF isolation of 30 dB and 40 dB are obtained, respectively. This mixer can be used in wireless LAN applications.

The most serious limitation hindering the wider application of microstrip antenna technology is the narrow bandwidth of the basic element. For this reason, many elements with enhanced bandwidth have been investigated. This paper presents measured results for an under-coupled microstrip patch antenna with the improved bandwidth. The impedance was matched by an open-circuit tuning stub connected in shunt with the feed line.

This paper presents the feedforward linear power amplifier (LPA) using error feedback technique to satisfy requirements of personal communications system (PCS) applications as well as GSM system. The proposed linear power amplifier is applied to feedforward technique combined with error feedback technique which has no main signal loss unlike typical feedback technique. In this case, the ultra reduction of intermodulation distortions (IMD) can be achieved. To verify ultra performance of the proposed LPA, it is designed, fabricated and measured. Two-tone signals at 1.85 GHz and 1.85125 GHz with a dBm/tone from synthesizers are injected into the LPA. The main power amplifier with gain of 30 dB and an average power of 10 W was fabricated. The proposed LPA could reduce more than 35 dB. The total IMD is more than -70 dBc.

A simple technique to reduce the overall dimension of a microstrip antenna with a partially filled dielectric substrate is proposed. The miniaturized microstrip antenna for a repeater system in a mobile communication cellular band (824 MHz-894MHz) is designed with the proposed technique, and commercialized with low cost, light weight, and small size. The proposed method will be more attractive for a light-weight, small-size, and low-cost microstrip array.

This paper describes a compact two-stage hybrid power amplifier for 5.8 GHz-band Wireless Local Area Network (WLAN) applications. The amplifier has been fabricated on high dielectric semiconductor wafer, and then the amplifier has small dimension compared with the conventional hybrid circuits. To fabricate the amplifier, the mask pattern is produced using electron beam lithography. Then the FET, capacitors and resistors are combined with the microstrip line pattern by silver epoxy. The size of the two-stage amplifier is measured to be 2.1 cm/spl times/1.4 cm.