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A compact spiral stripline-loaded monopole antenna with a vertical ground plane
Khang Nguyen, Truong,Lee, Keekeun,Choo, Hosung,Park, Ikmo Wiley Subscription Services, Inc., A Wiley Company 2008 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.50 No.1
<P>In this letter, we propose a compact spiral stripline-loaded monopole antenna on a vertical ground plane. The measured results show that the antenna has a fractional bandwidth of 12.1% for a voltage standing wave ratio (VSWR) less than 2 at the center frequency of 1.10 GHz, as well as a good omni-directional radiation pattern. The small size of 0.04 λ<SUB>o</SUB> × 0.04 λ<SUB>o</SUB> × 0.04 λ<SUB>o</SUB> makes it promising for use as an internal antenna in mobile handsets. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 250–252, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23043</P>
Multiband Dual Spiral Stripline-Loaded Monopole Antenna
Truong Khang Nguyen,Byoungchul Kim,Hosung Choo,Ikmo Park IEEE 2009 IEEE antennas and wireless propagation letters Vol.8 No.-
<P>We propose a multiband antenna that exhibits a dual coupling characteristic and dual frequency operation using a dual spiral stripline-loaded monopole in conjunction with L-shaped slots in a ground plane. The slots allow the upper part of the ground plane to function as an additional monopole that resonates in concordance with the existing resonances of the upper and lower spiral stripline monopoles. As a result, the impedance band- widths are greatly enhanced while maintaining relatively good omnidirectional radiation characteristics. The proposed antenna occupies a volume of 36 times 7 times 10<SUP>2</SUP> mm<SUP>3</SUP> including the ground plane, and the measured impedance bandwidths with VSWR < 2 simultaneously cover CDMA, GSM900, DCS1800, PCS1900, UMTS, IMT-2000, and WiMAX2350 bands. We describe the detailed antenna structure and present measurement results.</P>
Photoconductive dipole antennas for efficient terahertz receiver
Nguyen, Truong Khang,Kim, Won Tae,Kang, Bong Joo,Bark, Hyeon Sang,Kim, Kangho,Lee, Jaejin,Park, Ikmo,Jeon, Tae-In,Rotermund, Fabian Elsevier 2017 OPTICS COMMUNICATIONS - Vol.383 No.-
<P><B>Abstract</B></P> <P>We designed various photoconductive antennas applicable to efficient terahertz (THz) receivers and experimentally investigated their detection characteristics. Three different antennas based on Grischkowsky (H-), I-, and bowtie shapes were fabricated on a 1.2-μm-thick low-temperature GaAs layer that was grown on a semi-insulating GaAs substrate and subsequently attached to extended hemispherical silicon lenses. The experimental results showed different characteristics for detection responsivity and agreed well with the theoretical prediction. Measurements of the peak-to-peak amplitudes of the detected THz photocurrent were approximately 67, 42, and 59nA for the H-shaped, I-shaped, and bowtie-shaped antennas, respectively. The I- and bowtie-shaped antennas provided higher THz detection sensitivities than the H-shaped antenna in the low-frequency region, i.e., below 0.6THz. At a frequency of 0.2THz, the I- and bowtie-shaped antennas offered an approximately 3.6-fold and 6-fold enhancement, respectively, in THz detection sensitivity compared to the H-shaped antenna. The bowtie-shaped antenna produced better peak amplitude and a wider spectral bandwidth than the I-shaped antenna. The observed detection peak frequencies of the I-shaped and bowtie-shaped antennas possessing very long dipole arms indicate that the lowest limit of the frequency detected in a typical THz-TDS using a GaAs photoconductive antenna as emitter/detector is around 0.2THz.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We analysis, design, and characterization of three prototypes of photoconductive antennas namely Grischkowsky (H-shaped dipole) (Auston switch dipole), an I-shaped (stripline dipole), and a bowtie photoconductive antenna. </LI> <LI> A 'hybrid' numerical and analytical procedure for estimating the currents induced on the antenna and in the gap, when operating in the reception, is also discussed. The experimental results, which was obtained by a THz time-domain spectroscopy system, show different spectral detection responsivity and agree with the theoretical prediction. </LI> <LI> The experimental results show that the I-shaped and bowtie-shaped antennas could detect THz signals at low-frequency regions below 0.6 THz with a much higher sensitivity than the H-shaped antenna. Therefore, these two antennas could be promising for the sensitive room-temperature detection of THz radiation in the low THz frequency region or in THz wireless communication systems. </LI> <LI> The observed detection peak frequencies of the I-shaped and bowtie-shaped antennas possessing very long dipole arms indicate that the lowest limit of the frequency detected in a typical THz-TDS using a GaAs photoconductive antenna as emitter/detector is around 0.2 THz which has not been stated elsewhere. </LI> <LI> This study provides a good recommendation in THz output power improvement by tuning the frequency response of the antenna toward the frequency response of the photoconductive material for an enhanced coupling of THz radiation to antenna. </LI> </UL> </P>
A traveling-wave stripline dipole antenna on a substrate lens at terahertz frequency
Truong Khang Nguyen,이상민,박익모 한국물리학회 2014 Current Applied Physics Vol.14 No.8
In this paper, a study of a stripline dipole antenna on a substrate lens used as a photoconductive detector in a terahertz system is presented. The traveling-wave behavior of the stripline dipole and the influence of the substrate lens are investigated over a broad frequency range up to 5.0 THz. The numerical results show that the lens shape represented by the ratio of the extension length to the lens radius plays an important role in maximizing the antenna gain and radiation spectral bandwidth. The gain response exhibited an increased level of sensitivity to the lens shape as the lens size increased, and this is particularly important in optimizing large substrate lenses. Improvements in the gain level over the entire frequency range of interest were observed as the lens diameter increased. This study provides helpful guidelines in choosing and optimizing a substrate lens designed for a terahertz photoconductive antenna, which is particularly useful for specific applications requiring a miniaturized photoconductive antenna design.
Design of a Low-Profile, High-Gain Fabry-Perot Cavity Antenna for Ku-Band Applications
Truong Khang Nguyen,Ikmo Park 한국전자파학회JEES 2014 Journal of Electromagnetic Engineering and Science Vol.14 No.3
A Fabry-Perot resonator cavity antenna for Ku-band application is presented in this paper. The Fabry-Perot cavity is formed by a ground plane and a frequency selective surface (FSS) made of a circular hole array. The cavity resonance is excited by a single-feed microstrip patch located inside the cavity. The measured results show that the proposed antenna has an impedance bandwidth of approximately 13% (VSWR≤2) and a 3-dB gain bandwidth of approximately 7%. The antenna produces a maximum gain of 18.5 dBi and good radiation patterns over the entire 3-dB gain bandwidth. The antenna’s very thin profile, high directivity, and single excitation feed make it promising for use in wireless and satellite communication applications in a Ku-band frequency.
Truong Khang Nguyen,Bao Quoc Ta,박익모 한국물리학회 2015 Current Applied Physics Vol.15 No.9
This paper presents an optimum design of a substrate-integrated cavity-type antenna for use in the terahertz frequency range. The antenna was designed with a frequency-selective surface (FSS) and a planar feeding structure that are both patterned on a high-permittivity gallium-arsenide substrate. The FSS, printed on the bottom side of the substrate, is made of a circular hole array that acts as a partially reflecting mirror. Meanwhile, the planar feeding structure, printed on the top side of the substrate, is a center-fed, open-ended slotline whose ground plane acts as a perfect reflective mirror; thus, it forms a FabryePerot resonator. The optimized antenna produced a maximum boresight gain of 14.3 dBi, a radiation efficiency of 62%, and side-lobe levels of -15.1 dB and -15.0 dB for the E- and H-planes, respectively, at a resonance frequency of 320 GHz. The proposed design exhibits compactness, planarity, and light weight compared with the substrate lens-coupled antenna design.
Design of a Substrate-Integrated Fabry-Pérot Cavity Antenna for<i>K</i>-Band Applications
Nguyen, Truong Khang,Park, Ikmo Hindawi Limited 2015 International journal of antennas and propagation Vol.2015 No.-
<P>This paper presents the design of a planar, low-profile, high-gain, substrate-integrated Fabry-Pérot cavity antenna for<I>K</I>-band applications. The antenna consists of a frequency selective surface (FSS) and a planar feeding structure, which are both lithographically patterned on a high-permittivity substrate. The FSS is made of a circular hole array that acts as a partially reflecting mirror. The planar feeding structure is a wideband leaky-wave slit dipole fed by a coplanar waveguide whose ground plane acts as a perfect reflective mirror. The measured results show that the proposed antenna has an impedance bandwidth of more than 8% (VSWR ≤ 2), a maximum gain of 13.1 dBi, and a 3 dB gain bandwidth of approximately 1.3% at a resonance frequency of around 21.6 GHz. The proposed antenna features low-profile, easy integration into circuit boards, mechanical robustness, and excellent cost-effective mass production suitability.</P>