Ki-Jun Son

A study on RF characteristics of polyether sulfone substrate for application to flexible mobile communication device

In this work, coplanar waveguide was fabricated on flexible PES substrate, and their RF loss characteristics were extracted using transmission line theory. Concretely, several Q-factors of the coplanar waveguides were extracted using transmission line theory. Firstly, QL was characterized using the equivalent RLGC circuit. According to measured result, the QL was 25.7 at 49.8 GHz. Q-factor was also extracted from a resonant tank built using a one-quarter of a wavelength long line at the resonance frequency f0. According to the measured result, the Q-factor measured from one port open stub resonant circuit was 38.3 at a resonance frequency of 49.8 GHz, which was much higher than the open stub on silicon substrate.

Basic Study on RF Characteristics of Thin-Film Transmission Line Employing ML/CPW Composite Structure on Silicon Substrate and Its Application to a Highly Miniaturized Impedance Transformer

A thin-film transmission line (TFTL) employing a microstrip line/coplanar waveguide (ML/CPW) was fabricated on a silicon substrate for application to a miniaturized on-chip RF component, and the RF characteristics of the device with the proposed structure were investigated. The TFTL employing a ML/CPW composite structure exhibited a shorter wavelength than that of a conventional coplanar waveguide and that of a thin-film microstrip line. When the TFTL with the proposed structure was fabricated to have a length of λ/8, it showed a loss of less than 1.12 dB at up to 30 GHz. The improvement in the periodic capacitance of the TFTL caused for the propagation constant, β, and the effective permittivity, eeff, to have values higher than those of a device with only a conventional coplanar waveguide and a thin film microstrip line. The TFTL with the proposed structure showed a β of 0.53~2.96 rad/mm and an eeff of 22.3~25.3 when operating from 5 to 30 GHz. A highly miniaturized impedance transformer was fabricated on a silicon substrate using the proposed TFTL for application to a low-impedance transformation for broadband. The size of the impedance transformer was 0.01 mm2, which is only 1.04% of the size of a transformer fabricated using a conventional coplanar waveguide on a silicon substrate. The impedance transformer showed excellent RF performance for broadband.

A study on bandwidth of meander line employing periodic ground structure for application to miniaturization of RF components on GaAs MMIC

In this work, the meander line employing periodic ground structure (MLEPGS) was fabricated on GaAs substrate for application to a miniaturization of RF components on MMIC, and its bandwidth characteristics were thoroughly investigated. According to measured results, the MLEPGS exhibited the wavelength much shorter than conventional meander line. Concretely, the wavelength of the MLEPGS with T of 20 μm was 1.19 mm at 5 GHz, which was 16 % of the conventional meander line. We also studied the bandwidth of the passband and stopband of the MLEPGS. According to the result, the MLEPGS could be employed for application to a miniaturized RF components up to Ka band. Above results indicate that the MLEPGS is a promising candidate for application to a miniaturization of RF components in microwave range.

A basic study on RF characteristics of inverted comb-type capacitive transmission line structure on MMIC

In this work, the inverted comb-type capacitive transmission line (ICCTL) structure on GaAs monolithic microwave integrated circuit (MMIC) was proposed and its RF characteristics were investigated for application to a development of miniaturized on-chip passive components. According to the results, the ICCTL structure showed short wavelength characteristic due to an enhancement of its periodic capacitance. Concretely, the wavelength of the ICCTL structure was only 11.85% of conventional microstrip line on MMIC. The insertion loss of the ICCTL with a length of λ/8 was less than 0.36 dB up to 6 GHz, which was comparable to conventional microstrip line. Attenuation constant α and propagation constant β were also extracted using transmission line theory. According to the results, the ICCTL structure showed attenuation constant α lower than 1.06 Np/mm up to 10 GHz, and propagation constant β of 0.254 ~ 4.14 rad/mm from 0.5 to 10 GHz.

A highly miniaturized amplifier MMIC for application to a marine disaster early warning system

In this work, a highly miniaturized amplifier MMIC (Monolithic Microwave Integrated Circuit) was developed for application to a marine disaster warning system. According to measured results, the proposed amplifier MMIC showed good RF characteristics in a wide frequency range. Concretely, the Proposed amplifier MMIC showed a gain of 20 ±2 dB between 17 GHz and 27 GHz. The measured Pout was 17.79 dBm at 25 GHz. The measured P1dB of the amplifier MMIC exhibited the value of 15±2.5 dBm between 17 GHz and 27 GHz.