This paper presents a tri-state single-pole double-throw (SPDT) switch for X-band applications. The proposed tri-state SPDT switch uses three PIN diodes to switch among three states; two 1:1 modes and one 1:2 mode. In the 1:1 mode, the input power is only delivered to one of the output ports, but in the 1:2 mode, the input power is distributed evenly to the output ports. The proposed concept provides excellent impedance matching in all three states. Proof of concept is experimentally verified using an X-band prototype. The insertion loss is around 2.0dB with better than 18-dB isolation in the case of two 1:1 modes. For 1:2 mode, the insertion loss is around 1.9dB, around 2dB deviates from the ideal 3-dB power splitting.

This study proposes an amplified-spontaneous-emission feedback circuit (ASEFC) technique. The proposed technique is the first to employ signal wavelengths of an erbium-doped fiber as the input light. Consequently, the signal wavelength and dynamic range characteristics of the ASEFC were experimentally clarified. The technique demonstrated successful operation in a wide wavelength range of 1530-1560nm, and at a low input power level of approximately -5.2dBm. We successfully measured a small loss variation of a variable optical attenuator in a 50km remote fiber-optic sensing configuration using the proposed ASEFC technique and achieved improved optical power resolutions of less than 0.17mdB.

The LDO regulator and ESD protection circuit are essential circuit configurations for stable voltage provision and high reliability at the IC level. This paper proposes an LDO regulator with a built-in silicon controlled rectifier (SCR) based electrostatic discharge (ESD) protection circuit that can provide optimized voltage for low voltage applications. The proposed LDO regulator can skillfully control the output voltage by forming additional current discharge and supply paths through the dynamic current driving structure. In addition, in this paper, the high reliability of the IC was verified by intentionally exposing it to ESD situations depending on the presence or absence of the ESD protection circuit of the LDO regulator. It was confirmed that the proposed LDO regulator designed in a 0.13µm BCD process was kept an undershoot voltage of 23mV and an overshoot voltage of 21mV for a load current of 300mA. As a result, the proposed LDO regulator with built-in ESD protection circuit was secured high reliability of LDO regulator from ESD situation as well as low peak voltage due to load current.

This research focuses on the design of a super wideband (SWB) antenna and its two-port multiple input multiple output (MIMO) configurations. The antenna is designed to cover the wideband spectrum ranging from 1.42GHz to 40GHz, with the additional feature of tri-notch band functionality. The respective band spectrums of 3.5GHz, 5.8GHz, and 10.5GHz, which are worldwide assigned for 5th generation (5G), sub-6-GHz applications, Wireless local area network (WLAN), Industrial Science and Medical (ISM) applications and X-band are notched utilizing different shapes of slots. The SWB is achieved by converting a broadband circular monopole into an asymmetric semicircular monopole offering wideband, which is then modified by implementing the tapered line feed techniques. Furthermore, to reduce the mutual coupling among the MIMO elements, a T-shaped open-ended stub is loaded between them and optimized to achieve a low mutual coupling of ≤-20dB. Along with that, various MIMO performance parameters are studied and their comparison with the measured results is compared. Lastly, a comparison table is produced to indicate the competence of the suggested work in comparison to the state-of-the-art, which strengthens the provided conclusions.

This paper proposes an effective model predictive current control (E-MPCC) method for grid-connected quasi-Z-source T-Type inverter (QZSTI), which has a purpose of neutral voltage balance and eliminates the weight factor. The inductance current and capacitance voltage are controlled simultaneously using an enhanced sliding mode control technique to prevent the weight component in the cost function. Additionally, a sector selection approach that is accurate and efficient is suggested, avoiding the need for numerous calculations to perform each optimization individually. Results from simulations and experiments support the efficacy and supremacy of this approach.

The negative chirp operation of a hybrid modulation laser diode (HMLD) was numerically analyzed during operation with 25-Gbit/s non-return-to-zero (NRZ) dynamic signals. We confirmed that the dispersion tolerance of the 25-Gbit/s optical signal generated from the HMLD could be increased dramatically by introducing time delay to the modulation signals applied to the gain and intra-cavity loss modulation sections. These results suggest a unique approach for dispersion-tolerant directly modulated semiconductor lasers.

Electrically small antennas usually exhibit limited bandwidth and reduced efficiency. The aperture tuning technique offers a means to achieve broad frequency characteristics for such antennas. However, determining the optimal positioning of the tuning element can be challenging. Consequently, a novel wideband tuning method based on characteristic mode analysis is introduced. According to the analysis of modal significance and characteristic current distribution of the small loop antenna, a small slot is created at the location where the current of the primary resonant mode is strongest. Two varactors are then inserted in parallel within the slot and adjusted by using bias voltage. This method enables the originally narrowband resonant antenna to attain an ultra-wideband tuning capability. Experimental results confirm the feasibility and effectiveness of the method, revealing a relative tuning ultra-wideband bandwidth (VSWR < 3) is 53.6% (103MHz to 178.5MHz) and the gain is about -3.9to -1.8dBi within the bandwidth, Furthermore, the minimum electrical size is only 0.086λ.

For the optical particle inspection systems for unpatterned wafers, it is required to reduce inspection-accuracy variation in the wafer and increase inspection throughput. In this system, a laser beam is irradiated in a spiral shape by rotating and moving the wafer, and defect particles are detected based on the intensity of their scattered light. In this study, we propose a multi-stage optically variable attenuator system and its control method to achieve a constant laser-energy density on the wafer and high-speed inspection simultaneously.