• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.21 no.1
• /
• pp.107-114
• /
• 2021

In this paper, a planar transistor oscillator for X-band using a newly proposed L-shaped monopole slot resonator is proposed. For planar design, an L-shaped monopole slot with an open-end is used as a resonator for a transistor oscillator. As a result of the simulated design of the resonator in three stages, a high Q value of 1169.84 and a high insertion loss of 49.934 dB were identified. The results of the final design and manufactured oscillator measurements confirmed that the oscillation output is greater than 7 dBm and has good phase noise characteristics of -58 dBc/Hz at 100 kHz offset. The proposed oscillator is planar and has the advantage of being directly applicable to microwave integrated circuit technology. It also has the advantage of being able to reduce its size as it can only be implemented in microstrip form without additional devices such as metal cavities and tuning screws in 3D structures, as in the case of a DRO (dielectric resonance oscillator).

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.22 no.6
• /
• pp.149-154
• /
• 2022

Due to high power capabilities and high linearity of GaN devices, GaN Low-Noise Amplifiers (LNAs) without a limiter can be implemented in order to improve noise figure and reduce chip area in radar receivers. In this paper, a GaN LNA is presented for Ka-band radar receivers. The designed LNA was realized in a 150-nm GaN HEMT process and measurement results show that the voltage gain of >23 dB and the noise figure of <6.5 dB including packaging loss in the target frequency range. Under the high-power stress test, measured gain and noise figure of the GaN LNA is degraded after the first stress test, but no more degradation is observed under multiple stress tests. Through post-stress noise and s-parameter measurements, we verified that the GaN LNA is resilient to pulsed input power of ~40 dBm.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.13 no.6
• /
• pp.521-528
• /
• 1988

Into the telecommunications industry, which had been monopolistic, a few advanced countries introduced competition through 70's and 80's. And this trend is going on worldwide. The introduction of competition into the industry is made mainly in the long distance, international and enhanced market. This liberalisation results from the fundamental change of the cost function. Suggesting that the cost comprises of that of the facility sector and that of the operation sector there exists the economies of scale in the facility sector in general. The major ground for the monopolistic industrial structure in the past was the natural monopoly depending on the economies of scale. But the rapid advance of the technology by a large margin. This decrease has resulted in the change of the cost function. That is while there exists the economies of scale in the smaller production scale, the average cost increases beyond a certain scale. This means that the natural monopoly collapsed, and that the competitive structure is more efficient than the monopolistic structure. But, because there exists economies of scale in the smaller scale, the desirable number of players, which could result in efficient industry structure depends on the market size. Such correlation between technological level market size and the degree of regulation is found in the case of U.S.A., Japan and U.K., where deregulation policy of the telecommunications market has already been carried out. In U.S.A., which has the largest market and the highest technological level the degree of regulation is lowest. Also in the order of Japan and U.K. the regulation is severer. Japan and U.K. are likely to liberalize still more, as the technology advances and the market grows. This article is just the beginning of the research, and this hypothesis requires more detailed research.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.7 s.98
• /
• pp.753-759
• /
• 2005

In this paper, we have developed a new type of single balanced mixer with the RF MEMS $180^{\circ}$ hybrid coupler using surface micromachining technology. The $180^{\circ}$ hybrid coupler in this mixer is composed of the dielectric-supported air gapped microstriplines(DAMLs) which have signal line with $10{\mu}m$ height to reduce substrate dielectric loss and dielectric posts with size of $20{\mu}m{\times}20{\mu}m$ to elevate the signal line on air with stability At LO power of 7.2 dBm, the conversion loss was 15.5 dB f3r RF frequency or 57 GHz and RF power of -15 dBm. Also, we obtained the good RF to LO isolation of -40 dB at LO frequency of 58 GHz and LO power of 7.2 dBm. The main advantage of this type of mixer is that we are able to reduce the size of the chips due to integrating the MEMS passive components.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.11
• /
• pp.635-639
• /
• 2016

In the devices used in the microwave frequency band, the gain decreases as the frequency increases due to the parasitic component. To compensate for these characteristics, a linear gain equalizer with an opposite slope is needed in wideband systems, such as those used for electronic warfare. In this study, a linear gain equalizer that can be used in the 18 ~ 40GHz band is designed and fabricated. Circuit design and momentum design (optimizations) were carried out to reduce the errors between design and manufacturing. A thin film process is used to minimize the parasitic components within the implementation frequency band. A sheet resistance of 100 ohm/square was employed to minimize the wavelength variation due to the length of the thin film resistor. This linear gain equalizer is a structure that combines a quarter wavelength-resonator on a series microstrip line with a resistor. All three 1/4 wavelength short resonators were used. The fabricated linear gain equalizer has a loss of more than -5dB at 40GHz and a 6dB slope in the 18 ~ 40GHz band. By using the manufactured gain equalizer in a multi-stage connected device such as an electronic warfare receiver, the gain flatness degradation with increasing frequency can be reduced.

• Journal of Navigation and Port Research
• /
• v.28 no.3
• /
• pp.213-219
• /
• 2004

In this paper, a LNA(Low Noise Amplifier) has been developed, which is operating at L-band i.e., 1452∼1492 MHz for satellite DAB(Digital Audio Brcadcasting) receiver. The LNA is designed to improve input and output reflection coefficient and VSWR(Voltage Standing Wave Ratio) by balanced amplifier. The LNA consists of low noise amplification stage and gain amplification stage, which make a using of GaAs FET ATF-10136 and VNA-25 respectively, and is fabricated by hybrid method. To supply most suitable voltage and current, active bias circuit is designed Active biasing offers the advantage that variations in $V_P$ and $I_{DSS}$ will not necessitate a change in either the source or drain resistor value for a given bias condition. The active bias network automatically sets $V_{gs}$ for the desired drain voltage and drain current. The LNA is fabricated on FR-4 substrate with RF circuit and bias circuit, and integrated in aluminum housing. As a reults, the characteristics of the LNA implemented more than 32 dB in gain. 0.2 dB in gain flatness. lower than 0.95 dB in noise figure, 1.28 and 1.43 each input and output VSWR, and -13 dBm in $P_{1dB}$.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.5
• /
• pp.40-45
• /
• 2008

In this paper, a microstrip linear tapered slot antenna is designed. A tapered slot antenna(TSA) has many advantages such as low profile, low weight, easy fabrication, and compatibility with monolithic microwave integrated circuits(MMIC). In addition, it has demonstrated multi octave bandwidth, moderately high gain, and symmetrical E- and H-plane beam patterns. A feed network is implemented with transition between a microstrip and a slot line for the microstrip linear tapered slot antenna. The transition is consist of two sides. One side has a microstrip line, the other side has a slot line. The dimensions of the microstrip and slot line are ${\lambda}_m/4$ and ${\lambda}_s/4$ at the center of the cross section of the microstrip and slot line. In order to get broad bandwidth antenna characteristics, the tapered length is chosen as $4{\lambda}_o$ and termination width is chosen as $1.75{\lambda}_o$. Experimental results show that the microstrip tapered slot antenna has symmetrical E- and H-plane beam patterns with around 5GHz of bandwidth at center frequency of 5.0GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.3
• /
• pp.389-398
• /
• 2011

In this paper, the design and fabrication of a transmit/receive(T/R) module for Ka-band phased array radar is presented. A 5bit digital phase shifter and digital attenuator were used in common for both transmitter and receiver considering unique Ka-band characteristic. The circulator was excluded in the T/R module and was placed outside T/R module. The transmitting power per element antenna is designed to be about 1 W and the noise figure is designed to be below 8 dB. The designed T/R module RF part has a compact size of $5\;mm{\times}4\;mm{\times}57\;mm$. In order to implement the T/R module, MMICs used in T/R module was separately assessed before assembly of the designed T/R module. The transmitter of the fabricated T/R module shows about 1 W at 5 dBm unit module input power and the receiver shows a gain of about 20 dB and a noise figure of below 8 dB as expected in the design stage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.30 no.4
• /
• pp.282-285
• /
• 2019

A 100-nm gate-length metamorphic high electron mobility transistor(mHEMT) with a T-shaped gate was fabricated using a two-step gate recess and characterized for DC and microwave performance. The mHEMT device exhibited DC output characteristics having drain current($I_{dss}$), an extrinsic transconductance($g_m$) of 1,090 mS/mm and a threshold voltage($V_{th}$) of -0.65 V. The $f_T$ and $f_{max}$ obtained for the 100-nm mHEMT device were 190 and 260 GHz, respectively. The developed mHEMT will be applied in fabricating W-band monolithic microwave integrated circuits(MMICs).