Sumin Yun

Bioresorbable Electronic Stent Integrated with Therapeutic Nanoparticles for Endovascular Diseases

Implantable endovascular devices such as bare metal, drug eluting, and bioresorbable stents have transformed interventional care by providing continuous structural and mechanical support to many peripheral, neural, and coronary arteries affected by blockage. Although effective in achieving immediate restoration of blood flow, the long-term re-endothelialization and inflammation induced by mechanical stents are difficult to diagnose or treat. Here we present nanomaterial designs and integration strategies for the bioresorbable electronic stent with drug-infused functionalized nanoparticles to enable flow sensing, temperature monitoring, data storage, wireless power/data transmission, inflammation suppression, localized drug delivery, and hyperthermia therapy. In vivo and ex vivo animal experiments as well as in vitro cell studies demonstrate the previously unrecognized potential for bioresorbable electronic implants coupled with bioinert therapeutic nanoparticles in the endovascular system.

Bandwidth Enhancement of Cavity-Backed Slot Antenna Using a Via-Hole Above the Slot

A novel technique for the bandwidth enhancement of a cavity-backed slot antenna is presented. A via-hole located above the slot creates an additional resonance at a higher frequency by shortening the effective length of the slot. The location of the via-hole can be changed to determine the second resonance frequency of the antenna. With proper placement of the via-hole, the bandwidth of cavity-backed slot antenna can be increased. The fabricated antenna has a 60% wider bandwidth than a cavity-backed slot antenna without a via-hole. The proposed antenna maintains high radiation efficiency and gain, which are characteristics of a conventional cavity-backed slot antenna. The proposed technique is especially useful for enhancing the bandwidth of a cavity-backed slot antenna in a limited area.

Outer-Wall Loop Antenna for Ultrawideband Capsule Endoscope System

The capsule endoscopy system has been used to obtain an image from the inside of the human digestive tract. To acquire high-resolution images, a loop antenna with ultrawide bandwidth is proposed. It is part of the outer wall of the capsule, thus decreasing volume and increasing performance, and uses a meandered line for resonance in an electrically small area. The proposed antenna makes maximal use of the capsules outer surface, enabling the antenna to be larger than inner antennas. The measured result shows that the gain of the proposed antenna is higher than that of inner antennas. Return loss and radiation pattern are investigated through simulation and measurement, showing that the proposed antenna has an ultrawide bandwidth of 260 MHz (from 370 to 630 MHz) for VSWR <; 2 and an omnidirectional radiation pattern. Using identical antenna pairs in the equivalent body phantom fluid, antenna efficiency is measured to 43.7% (-3.6 dB).

A Design of a High-Speed and High-Efficiency Capsule Endoscopy System

This paper presents a high-speed and high-efficiency capsule endoscopy system. Both a transmitter and a receiver were optimized for its application through an analysis of the human body channel. ON-OFF keying modulation is utilized to achieve low power consumption of the in-body transmitter. A low drop output regulator is adopted to prevent performance degradation in the event of a voltage drop in the battery. The receiver adopts superheterodyne structure to obtain high sensitivity, considering the link budget from the previous analysis. The receiver and transmitter were fabricated using the CMOS 0.13-μm process. The output power of the transmitter is -1.6 dB·m and its efficiency is 27.7%. The minimum sensitivity of the receiver is -80 dB·m at a bit error ratio (BER) of 3 × 10 . An outer wall loop antenna is adopted for the capsule system to ensure a small size. The integrated system is evaluated using a liquid human phantom and a living pig, resulting in clean captured images.

Bandwidth and Efficiency Enhancement of Cavity-Backed Slot Antenna Using a Substrate Removal

A technique for enhancement of bandwidth and efficiency of a cavity-backed slot antenna is proposed. The bandwidth of the cavity-backed slot antenna depends on the Q of the slot and the cavity. The proposed technique removes the substrate under the slot to decrease the capacitance of the slot. Because a half-wavelength slot is considered a parallel resonant circuit at resonant frequency, lowered capacitance increases the bandwidth of the antenna. Antenna efficiency also can be enhanced by the proposed technique. The dielectric loss, which is produced by the E-field across the slot, is effectively decreased by removing the substrate under the slot. Various simulation results of demonstration of the proposed technique are given. The proposed antenna, which was fabricated on a 2-mm-height FR-4 substrate, shows 6.2% higher antenna efficiency and 24% wider bandwidth compared to the conventional cavity-backed slot antenna, which has a whole substrate. The proposed technique is effective in enhancing the efficiency and bandwidth of a cavity-backed slot antenna.

Low-Power CMOS Super-Regenerative Receiver With a Digitally Self-Quenching Loop

A 500 MHz super-regenerative receiver (SRR) with a digitally self-quenching loop (DSQL) is designed for low-power/high-data-rate applications. The DSQL replaces the envelope detector used in a conventional SRR and minimizes the overall power consumption by generating a self-quench signal digitally for a super-regenerative oscillator. The receiver is fabricated using a 0.13 μm CMOS process. The chip size is 0.7 mm2 and the minimum energy usage is 0.09 nJ/b with a supply voltage of 1 V at a data rate of 10 Mbps. The measured sensitivity is - 76 dBm.

Folded Cavity-Backed Crossed-Slot Antenna

A folded, cavity-backed crossed-slot antenna is proposed for antenna miniaturization. The cavity dimensions of a conventional cavity-backed crossed-slot antenna are about a half-guided-wavelength along each side, which is unsuitable in many applications like a handheld device or body area network (BAN). To reduce the size of the cavity, a folded cavity is proposed in this letter. The center plate that divides the cavity into the upper cavity and the lower cavity increases the effective length inside the cavity. Compared to the conventional cavity-backed crossed-slot antenna, a 72.8% size reduction can be achieved using the proposed structure. The proposed antenna also has circular polarization and wideband characteristics, which are the main advantages of a cavity-backed crossed-slot antenna. The proposed technique is especially useful for reducing the lateral dimensions of the cavity.

Mutual coupling analysis of antennas in layered media through equivalent sources for wireless power transfer

Summary form only given. In recent years, wireless power transfer has received much attention and been widely studied. Wireless power transfer has many applications. For example, there are the systems that transfer energy wirelessly to an electric car, sensors buried in a wall, devices beyond a wall, and devices in the ground. The one of the modeling method for such systems is to assume that antennas are in layered media and solve the mutual coupling between antennas. In this work, we propose the method for calculating the Z-parameter between antennas in layered media and the maximum power transfer efficiency of a wireless power transfer system. According to spherical wave theory (R. J. Pirkl, IEEE Trans. Antennas Propag., vol. 60, no. 12, pp. 5654-5662), the S-parameter between two antennas in arbitrary environments can be calculated using the generalized scattering matrix of an antenna. When we calculate the S-parameter using this method, the specified antenna structures are not needed. A canonical minimum scattering (CMS) antenna is an antenna that does not scatter electromagnetic fields when its feeding ports are open-circuited. Many antennas that are small relative to the wavelength can be considered CMS antennas. Therefore, we can assume that antennas are CMS antennas when we analyze wireless power transfer. The generalized scattering matrix of a CMS antenna can be determined solely from the radiation pattern and radiation efficiency. Therefore, the maximum power transfer efficiency of a wireless power transfer system depends on only the radiation pattern and radiation efficiency of CMS antennas. Let the antenna structures in two wireless power transfer systems be different. If the radiation pattern and radiation efficiency of the antennas in the two wireless power transfer system are identical, the maximum power transfer efficiency of the two wireless power transfer system are the same because the S-parameter of the two systems are the same. Therefore, we can change the original antenna structures to the current distributions that have the same modal transmitting pattern as the original antennas to calculate the maximum power transfer efficiency. To analyze wireless power transfer, we change the original antenna structures in layered media to simple equivalent sources. The Z-parameter between antennas can be determined from equivalent sources using the induced EMF method. From the Z-parameter, we can investigate the characteristics of wireless power transfer.

Matnetic tripolarizaiton antenna for DSRC applications

A magnetic tripolarization antenna is proposed for DSRC (Dedicated Short Range Communication) applications. A conventional patch antenna, which is usually used to generate the horizontal polarization, is modified to generate the perpendicular polarizations by including the ring slots. The opposite currents flowing the upper and under conductors generate loop current. For the horizontal polarization ZOR (Zeroth Order Resonance) loop antenna is included in the proposed structure. The uniform current of the ZOR loop antenna effectively generates the horizontal polarization. The simulated result shows that the proposed antenna has -10 dB impedance bandwidths from 5.85 to 5.94 GHz, which is appropriate for DSRC applications. The isolation between ports is higher than 25 dB over DSRC bandwidth. The proposed antenna has a size of 32 × 32 × 1.57 mm3.

Reconfigurable shorted patch antenna using via-hole connection control

Patch antennas that have many attractive features like low-profile, planar surface are widely used in Wireless Body Area Network applications. As the patch antenna has a ground structure behind the patch, its radiation efficiency is higher than the antennas without ground structure in on-body environment.