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Wireless communication technologies are expected to become essential in future self-driving vehicles. This study presents an antenna for vehicle wireless communication with a bandwidth of 75 MHz at a Wireless Access in Vehicular Environment frequency of 5.885 GHz. To compensate for the backward link path loss from the vehicle interior and passengers, the antenna is designed to have asymmetric gains of 0 and 6 dBi at 0° and 180°, respectively. The antenna is validated through an outdoor road test. We measured the received continuous-wave (CW) power, received signal strength indicator, and packet-delivered ratio (PDR) of the digital signal under vehicle-to-vehicle communication mode. Similar power is received in both the backward and forward scenarios. The forward and backward PDR are also similar.

This paper discusses the characteristics and effects of dielectric inner-supports on discone antenna for broadband RF test chamber, and the verification has been performed by simulation. Several design parameters such as the thickness of the gap support, the position of the side support, and the thickness of the side support has been analyzed. The thickness of the gap support affected the reflection coefficient. An effect of the offset of the side support from the center was slight below 3 GHz and significant above 3 GHz. The thickness of the side support did not affect the reflection coefficient or the gain much. The performance of the fabricated discone antenna was in good agreement with the simulated results. This investigation of a dielectric support effects could be used to design a commercial discone antenna for broadband RF test chamber, focusing on electrical performance and mechanical stability.

This paper proposes a reconfigurable microstrip diplexer, also known as a switchplexer, for use with single-switch operation of frequency band and output path. The proposed switchplexer is composed of a rectangular ring resonator and a switch on a shorting pin, which is inserted between the ring resonator and the ground plane. The rotated main current distributions occurring at different switch statuses provide the diplexer’s different operating bands and different output ports. The performance of the simply designed switchplexer is successfully demonstrated via simulation and measurement.

Communication between moving vehicles is very important for safety. In this paper, a bidirectional antenna that can be installed inside a vehicle is proposed and tested in a real vehicular environment at 5.8 GHz. The forward link and backward link seated by two persons and three persons were compared in terms of received RF power and the peak-to-average power ratio (PAR). It was found that, even with three persons, the power link fulfilled the communication requirements using the proposed antenna.

Terahertz (THz) detectors have been extensively studied for various applications such as security, wireless communication, and medical imaging. In case of metal-insulator-metal (MIM) tunnel junction THz detector, a small junction area is desirable because the detector response time can be shortened by reducing it. An edge metal-semiconductor-metal (EMSM) junction has been developed with a small junction area controlled precisely by the thicknesses of metal and semiconductor films. The voltage response of the EMSM THz detector shows the clear dependence on the polarization angle of incident THz wave and the responsivity is found to be very high (~2,169 V/W) at 0.4 THz without any antenna and signal amplifier. The EMSM junction structure can be a new and efficient way of fabricating the nonlinear device THz detector with high cut-off frequency relying on extremely small junction area.

This paper presents a novel frequency-tunable open-ring microstrip antenna for radiated-power measurements in a real environment. In order to elevate the probing up to a few tens of meters, the antenna must have light-weight, narrow-bandwidth, and broad side-beam characteristics. An open-ring microstrip antenna is a good candidate for satisfying these requirements. Varactors are attached to tune the operation frequency, but the conventional position, which is in the vicinity of the ring-opening, shows a much lower gain and poor cross-polarization level. This paper proposes a superior position for the varactors, which is the upper-edge of the left and right sides of the ring. The reflection coefficient (S11) in the simulation and experiment demonstrated that the resonant frequency can be increased by increasing the supply voltage. The proposed tunable antenna can be utilized in the probing apparatus to measure the radiated power.

A single-layer polarization-switchable frequency-band-fixed microstrip square-ring antenna was developed. The copolar plane of the radiation pattern was reconfigured with a single-switch, but the resonant frequencies were identical. A microstrip square-ring antenna was adopted, and the lateral and vertical widths of the microstrip ring were tuned to agree the resonant frequencies of the unloaded or loaded antenna. A single-layer dielectric substrate was used instead of a latest three-layer configuration. Antenna impedance was optimized to a value between those of the loaded and unloaded antennas. The proposed antenna exhibited single-switch polarization–reconfiguration on a single-layer substrate, and could thus be used in mobile communications and microwave imaging systems. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1874–1879, 2014

This article proposes a reconfigurable microstrip antenna that changes its polarization with only a single switch at a single frequency band. The antenna consists primarily of a square ring and a square patch, with a foam layer. When the connection status between the square ring and the ground is changed between shorted and open status, the linear polarizations are switched. The resonant frequency of the antenna using a single switch reported previously has been shifted, but the proposed antenna in this article exhibits a fixed resonant frequency. The design principle is as follows: The square-ring printed on the dielectric substrate has inherent narrow bandwidth, but we found that its polarization-switching characteristics existed over the broad band. The square patch is placed above the square ring, and it provides a broad bandwidth while maintaining polarization diversity. The performance of the antenna is successfully demonstrated via simulation and measurement. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:57–60, 2014

In this article, we describe a frequency-tunability procedure for a waveguide single-pole bandpass filter adopting a split-ring resonator (SRR). The tuning procedure is, in this article, achieved by inserting a metal or ferrite tuning screw, depending on the desired tuning direction. The screw plays a role in the adjustment of the magnetic field passing through the center of the SRR. The discrepancy between the proposed waveguide filter and the evanescent-mode filter has been included. The aperture size of the waveguide filter is decreased by about 70% in comparison with conventional waveguides. The wide tuning bandwidths and lower insertion losses obtained by both simulation and measurement confirm the validity of the proposed technique. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1649–1653, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27618

This letter reports a miniaturized, multiband patch antenna capable of detecting thee frequencies in conjunction with CMOS array detector element for real-time multi-frequency imaging in terahertz (THz)-band.Multi-frequency operation is desirable for THz CMOS camera design, which is achieved by using stubs and slot-type split ring resonator on the patch antenna connected to the on-chip CMOS detector. The proposed antenna is designed at three-bands of 218, 338, and 400 GHz corresponding to the atmospheric transmission windows. And the performance of the multiband THz antenna is successfully demonstrated using the finite-difference time-domain method. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2012

This letter proposes an open-ended waveguide antenna with a single split-ring resonator. In contrast to the waveguide antennas incorporating multiple rings reported in a previous study, which exhibited narrow bandwidth, the proposed antenna uses only one ring to achieve broader bandwidth while keeping the aperture small. A single ring has a relatively low quality factor compared to multiple rings. The simulated and measured fractional bandwidth was 4.13% and 4.03%, respectively, which is much broader than the fractional bandwidth of about 1% demonstrated in a previous study. This simple technique can be used in many applications that require small apertures including near-field probes and array elements.

We propose a frequency-tunable waveguide antenna with a size-reduced aperture. Up to now, waveguide antennas with split-ring resonators have exhibited narrow-frequency bandwidths. To expand the operating frequency band, the resonant frequency of a split-ring resonator is tuned by adjusting the capacitance of the gap. A capacitor-loaded split-ring resonator is simulated and experimentally tested to validate its performance, and a varactor-loaded split-ring resonator is then investigated. The effective capacitance of the varactor-loaded split-ring resonator is changed by varying the external dc voltage. The tunable frequency range extends from 1.96 to 2.36 GHz (a fractional frequency range of 18.5%). The simulations and experiments yield good results for the reflection coefficient, radiation pattern, and gain. The proposed antenna retains the 70% aperture reduction of previously developed split-ring-resonator-loaded waveguide antennas.

This article presents the design and fabrication of a quad-band spiral-shaped monopole antenna for application in a GPS (1575 ± 10 MHz)/DCS (1710–1880 MHz)/PCS (1850–1990 MHz) with a UMTS (1920–2170 MHz) band. To obtain sufficient bandwidth in VSWR < 2, an air layer is inserted between the ground plane and the substrate. A spiral-shaped monopole antenna that has a quad-band characteristic is used. Important design parameters are the spiral radiator gap's width and length, the air-gap's height, and the feed point's position. From these optimized parameters, a spiral-shaped monopole antenna is fabricated and measured. The measured results of the fabricated antenna are obtained from all bands at 940 MHz bandwidths in VSWR < 2 referenced to the center frequency, and the individual gain at 2.2 dBi, 2.5 dBi, 2.6 dBi, and 2.6 dBi. The experimental 3 dB beam width is shown to be broad across the pass band in the E-plane, and 74°, 68°, 64°, and 60°, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2860–2863, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23810

We report the experiments of plasmonic terahertz (THz) wave detector based on silicon field-effect transistors (FETs) in the nonresonant sub-THz (0.2 THz) regime. The detector responsivity (RV) as a function of gate voltage has been successfully controlled by the radiation power in agreement with the plasma wave detection theory. To investigate the effects of the overdamped charge asymmetry on RV, FET structure with the asymmetric source and drain area under the gate has been proposed. The enhanced RV according to the increase of asymmetry ratio between source and drain region has been confirmed experimentally.

In this letter, we report the experimental demonstrations of the enhanced responsivity in Si metal-oxide-semiconductor (MOS) FET-based plasmonic THz detector [2, 3] with asymmetric source and drain region considering the device width variations.

We report the experiments of a plasmonic terahertz (THz) wave detector based on silicon (Si) field-effect transistors (FETs) in the nonresonant sub-THz (0.2 THz) regime. To investigate the effects of the overdamped charge asymmetry on responsivity (R V), a FET structure with the asymmetric source and drain area under the gate has been proposed. R V as a function of gate voltage in Si FET-based detectors integrated with an antenna has been successfully enhanced by the asymmetry ratio (ηa = W D/W S) of gate-overlapped drain width (W D) to source width (W S) in agreement with the nonresonant quasi-plasma wave detection theory. The experimentally measured photoresponse has been enhanced by about 36.2 times on average from various samples according to the 10-fold increase in ηa. The effect of the integrated bow-tie antenna on the performance enhancement has also been estimated as 60-fold at the maximum incident angle for the polarized THz wave source.

This paper reports a miniaturized patch antenna capable of detecting multi-frequencies in conjunction with CMOS detector arrays for real-time imaging in THz-band. The proposed antenna is designed at three-bands of 218, 338 and 400 GHz corresponding to the atmospheric transmission windows. And the performance of the triple-band THz antenna is demonstrated using the finite-difference time-domain method.

A sub-terahertz gyrotron, employed with a compact cryogen-free magnet, is developed to be used as an illumination source of the active T-ray imaging system for food inspection in real time. Details of the gyrotron development, as well as some preliminary results of real-time T-ray imaging of foreign bodies hidden in food, will be presented.

A sub-terahertz gyrotron is designed to be used as a radiation source of an active real-time imaging system for food safety inspection. The gyrotron employed with compact cryogen-free magnet, is expected to produce 10 W-level in continuous wave at 408 GHz. Details of the gyrotron design as well as the concept and configuration for the real-time imaging system will be discussed.

In this letter, a novel antenna with a miniaturized aperture is proposed. The substrate including a split-ring resonator array is inserted into a size-reduced open-ended waveguide. For a low return loss and high radiation efficiency, the ring arrangement is optimized, and a stepped transition using H-plane discontinuity is proposed. The proposed antenna achieves a 70% aperture reduction compared to a conventional standard waveguide antenna of WR-187 (47.6 mm22.2 mm). The return loss drops significantly at three frequencies, and a reasonable gain is achieved. The aperture-miniaturized antenna can be used in many antenna applications such as near-field measurement.

A single-layer polarization-switchable frequency-bandfixed microstrip square-ring antenna was developed. The copolar plane of the radiation pattern was reconfigured with a single-switch, but the resonant frequencies were identical. A microstrip square-ring antenna was adopted, and the lateral and vertical widths of the microstrip ring were tuned to agree the resonant frequencies of the unloaded or loaded antenna. A single-layer dielectric substrate was used instead of a latest three-layer configuration. Antenna impedance was optimized to a value between those of the loaded and unloaded antennas. The proposed antenna exhibited single-switch polarization–reconfiguration on a single-layer substrate, and could thus be used in mobile communications and microwave imaging systems. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1874–1879, 2014

We report the first implementation of a modeling and simulation environment for the plasmonic terahertz (THz) detector based on the silicon (Si) field-effect transistor (FET) with a technology computer-aided-design (TCAD) platform. The nonresonant plasmonic behavior has been modeled by introducing a quasi-plasma electron box as a two-dimensional electron gas (2DEG) in the channel region. The alternate-current (AC) signal as an incoming THz wave radiation successfully induced a direct-current (DC) drain-to-source voltage as a detection signal in the broadband sub-THz frequency regime. The simulated dependences of photoinduced DC detection signals on structural parameters such as gate length and dielectric thickness confirmed the operation principle of the nonresonant plasmonic THz detector in the Si FET structure. We evaluated the design specifications of THz detectors considering both responsivity and noise equivalent power (NEP) as the typical performance metrics. The proposed methodologies provide the physical design platform for developing novel plasmonic THz detectors operating in the nonresonant detection mode.