• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.10 s.352
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• pp.90-97
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• 2006

We report our research work on the millimeter-wave broadband amplifier integrating the shunt peaking technology with the cascode configuration. The millimeter-wave broadband cascode amplifier on MIMIC technology was designed and fabricated using $0.1{\mu}m\;{\Gamma}-gate$ GaAs PHEMT, CPW, and passive library. The fabricated PHEMT has shown a transconductance of 346.3 mS/mm, a current gain cut off frequency ($f_T$) of 113 GHz, and a maximum oscillation frequency ($f_{max}$) of 180 GHz. To prevent oscillation of designed cascode amplifier, a parallel resistor and capacitor were connected to drain of common-gate device. For expansion of the bandwidth and flatness of the gain, we inserted the short stub into bias circuits and the compensation transmission line between common-source device and common-gate device, and then their lengths were optimized. Also, the input and output stages were designed using the matching method to obtain the broadband characteristic. From the measurement, we could confirm to extend bandwidth and flat gain by integrating the shunt peaking technology with the cascode configuration. The cascode amplifier shows the broadband characteristic from 19 GHz to 53.5 GHz. Also, the average gain of this amplifier is about 6.5 dB over the bandwidth.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.9
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• pp.13-19
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• 1998

It was shown that the bandwidth of T-shaped microstripline fed slot antenna is wider than many of the conventional feeding structures. In this paper, we proposed a new method of enhancing the bandwidth of T-shaped microstripline fed slot antenna with a shunt open stub, and analyzed this antenna by using the FDTD method. We have computed waves and electric field distribution in the time domain, and VSWR, input impedance and radiation pattern in the frequency domaim by Fourier transforming the time domain results. It was found that the bandwidth of this antenna depend on the position(L$_1$) and length(L$_2$) of a shunt open stub. When these parameters are L$_1$=30 mm and L$_2$=33mm, we obtained the maximum bandwidth at the center frequency of 2.3 GHz. From the computed results, the optimum antenna is designed and fabricated. The fractional bandwidth of this antenna was 53.9 %. The measured results were in relatively good accordance with computed values.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.852-857
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• 2011

In this paper, the application of a variable characteristic impedance transmission line that can be used to design a dual-band bandpass filter(BPF) is presented. The proposed filter offers a fixed first frequency passband and a controllable second passband. The tuning of the second passband is achieved by varying the characteristic impedance of and open shunt stub line in a stub loaded resonator(SLR) with the help of a defected ground structure(DGS) transmission line and varactor diodes. In order to validate the proposed structure, a two stage dual-band BPF with three transmission zeros was implemeted and experimentally verified based on its theoretical predictions and simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.72-73
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• 2016

In this paper, we studied a method for miniaturizing a broadband stacked patch antenna structure which is widely used for bandwidth improvement. Main patch is a rectangular microstrip patch antenna fed by a 50-ohm microstrip line, and a parasitic patch is laid above the main patch. The size of the main patch is designed to be resonated near the center frequency of the desired frequency band. Then parasitic patch longer than main patch is placed above the main patch. The distance between two patches might be adjusted so as to achieve impedance matching using a shunt open stub. The shunt matching stub is inserted underneath the parasitic patch and so it does not require additional space, which enables the proposed antenna structure to be advantageous in miniaturizing antenna. The effects of the various parameters on the antenna performance are examined, and we introduced the design procedure for the proposed antenna to operate in the frequency range of 2.3-2.7 GHz.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.159-163
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• 2016

In this paper, a frequency tunable double band-stop resonator (BSR) with voltage control by varactor diodes is suggested. It makes use of a half-wavelength shunt stub as its conventional basic structure, which is replaced by the distributed LC block. Taking advantage of the nonlinear relationship between the frequency and electrical length of the distributed LC block, a dual-band device can be designed easily. With two varactor diodes, the stop-band of the resonator can be easily tuned by controlling the electrical length of the resonator structure. The measurement results show the tuning ranges of the two operating frequencies to be 1.82 GHz to 2.03 GHz and 2.81 GHz to 3.03 GHz, respectively. The entire size of the resonator is $10mm{\times}11mm$, which is very compact.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.4
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• pp.1-10
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• 1993

This paper presents the designing/manufacturing scheme of the diplexer for satellite transponder which is composed of 2-channel bandpass filters, coupled with E-plane T-junction, having symmetrical waveguide E-plane step discontinuity structures. The 2-channel bandpass filters of the diplexer are designed by the scheme of connecting ${\lambda}_{g}$/2 shunt stub to the waveguide E-plane, playing the role of heat sinks without attaching a special heat sinks and to give the profitable productivity and allow the low-cost manufacturing at mass production, tuning screws are eliminated which have been used to compensate the operating characteristics of manufactured filters. The 2 channel bandpass filters of manufactured 14/12 GHz diplexer for domestic Ku-band satellite transponder have the return loss of 25 dB, insertion loss of 0.3 dB in passband, and below-50 dB of stopband characteristics (T$_{x}$ : f$_{o}{\pm}$250 MHz, R$_{x}$ : f$_{o}{\pm}$220 MHz) at room temperature.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.594-602
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• 2005

In this paper, a new type of 5-pole low pass filter(LPF) having defected ground structure(DGS) and very wide transmission line elements is proposed. The previously presented design method of 3-stage LPF using DGS is generalized to design N-pole LPFs for $N\geq5$. As an example, a 5-pole LPF having DGS is designed and measured. The accurate curve-fitting method to determine the series inductors in the prototype filter, and ultimately the size of DGS is described. The proposed 5-pole LPF has transmission line elements with a very low impedance to realize the required shunt capacitance instead of open stubs. Therefore, open stub. Therefore, open stub, Tee-junction, Cross-junction, and high impedance line are not required for the proposed LPF, while they all have been essential in conventional LPFs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.912-918
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• 2011

In this paper, a composite right-/left-handed(CRLH) rectangular waveguide satisfying a balanced condition above the cut-off frequency is presented. The proposed structure consists of one shorted stub and two twisted H-plane irises which produce an effectively negative permeability and permittivity, respectively. The CRLH structure can independently control the series and shunt resonance frequencies of a CRLH transmission line which determine the left-handed(LH) and right-handed(RH) bands due to a minimized coupling between a shorted stub and twisted H-plane irises. Thus, the design of the CRLH waveguide satisfying a balanced condition is possible. To analyze the CRLH structure, a crossly connected equivalent circuit is derived. The simulated and measured results confirm that the proposed CRLH waveguide has a transmission property without a band gap among the LH and RH bands.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.3
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• pp.467-474
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• 2019

In this paper, we studied a method for a broadband stacked patch antenna structure which is widely used for bandwidth improvement. The characteristics according to the distance between the two patches were analyzed and the impedance matching was optimized by connecting parallel open stubs to the main patch feed line. The shunt matching stub is inserted underneath the parasitic patch and so it does not require additional space, which enables the proposed antenna structure to be advantageous in miniaturizing antenna. The effects of the various parameters on the antenna performance are examined, and we introduced the design procedure for the proposed antenna to operate in the frequency range of 2.3~2.7GHz. Experimental results show that the bandwidth of the proposed antenna is about 480MHz with 2.27~2.75GHz bandwidth. And the antenna gain was 5.8dBi at 2.3GHz and 7.8dBi at 2.6GHz within the bandwidth.

• Journal of Digital Convergence
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• v.12 no.4
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• pp.343-348
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• 2014

This paper suggested a theoretical approach and an implementation for the design of an unequal Wilkinson power divider with a high dividing ratio operating at two-frequencies. The T-section transmission lines and the two-section of Monzon's theory are proposed to operate a dual-band application. To achieve the high dividing ratio divider, the high impedance line using a T-shaped structure and low impedance lines with periodic shunt open stubs are implemented. For the validation of this divider, a dual-band power divider with a high dividing ratio of 5 is simulated and measured at 1 GHz and 2 GHz. The measured performances of the divider are in good agreements with simulation results.