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Biomedical imaging is an essential tool for investigating biological responses in vivo. Among the several imaging techniques, optical imaging systems with multispectral analysis of nanoparticles have been widely investigated due to their ability to distinguish the substances in biological tissues in vivo. This review article focus on multispectral optical imaging techniques that can provide molecular functional information. We summarize the basic principle of the spectral unmixing technique that enables the delineation of optical chromophores. Then, we explore the principle, typical system configuration, and biomedical applications of the representative optical imaging techniques, which are fluorescence imaging, two-photon microscopy, and photoacoustic imaging. The results in the recent studies show the great potential of the multispectral analysis techniques for monitoring responses of biological systems in vivo.

Background Regeneration of defective neurons in central nervous system is a highlighted issue for neurodegenerative disease treatment. Various tissue engineering approaches have focused on neuritogenesis to achieve the regeneration of damaged neuronal cells because damaged neurons often fail to achieve spontaneous restoration of neonatal neurites. Meanwhile, owing to the demand for a better diagnosis, studies of super-resolution imaging techniques in fluorescence microscopy have triggered the technological development to surpass the classical resolution dictated by the optical diffraction limit for precise observations of neuronal behaviors. Herein, the multifunctional nanodiamonds (NDs) as neuritogenesis promoters and super-resolution imaging probes were studied. Methods To investigate the neuritogenesis-inducing capability of NDs, ND-containing growing medium and differentiation medium were added to the HT-22 hippocampal neuronal cells and incubated for 10 d. In vitro and ex vivo images were visualized through custom-built two-photon microscopy using NDs as imaging probes and the direct stochastic optical reconstruction microscopy (dSTORM) process was performed for the super-resolution reconstruction owing to the photoblinking properties of NDs. Moreover, ex vivo imaging of the mouse brain was performed 24 h after the intravenous injection of NDs. Results NDs were endocytosed by the cells and promoted spontaneous neuritogenesis without any differentiation factors, where NDs exhibited no significant toxicity with their outstanding biocompatibility. The images of ND-endocytosed cells were reconstructed into super-resolution images through dSTORM, thereby addressing the problem of image distortion due to nano-sized particles, including size expansion and the challenge in distinguishing the nearby located particles. Furthermore, the ex vivo images of NDs in mouse brain confirmed that NDs could penetrate the blood–brain barrier (BBB) and retain their photoblinking property for dSTORM application. Conclusions It was demonstrated that the NDs are capable of dSTORM super-resolution imaging, neuritogenic facilitation, and BBB penetration, suggesting their remarkable potential in biological applications.

We propose line-field white light interferometry using a tunable-path-difference source, improving imaging performance. By simultaneously acquiring signals along the line, the system has higher imaging speed and stability for a wide field of view imaging.

In this study, an active mode-locked tunable pulsed laser (AML-TPL) is proposed to excite picosecond pulsed light with a rapid wavelength tunability of approximately 800 nm for multiphoton microscopy. The AML-TPL is schematically based on a fiber-cavity semiconductor optical amplifier (SOA) configuration to implement a robust and align-free pulsed light source with a duration of 1.6 ps, a repetition rate of 27.9271 MHz, and average output power of over 600 mW. A custom-built multiphoton imaging system was also built to demonstrate the imaging performance of the proposed AML-TPL by comparing with the commercial Ti:Sapphire femtosecond laser. Two-photon excited fluorescence images were successfully acquired using a human breast cancer cell line (MDA-MB-231) stained with acridine orange.

A new method of sidelobe level (SLL) reduction for a substrate integrated waveguide (SIW) slot array antenna is presented. In this method, amplitude distribution is assigned to the slots by tapering the SIW width. The SIW with tapered width can be efficiently manufactured by varying the position of the side-wall vias. In this letter, the new method is verified on a 12-element SIW slot array antenna operating at 94 GHz to achieve SLL around –30 dB. The antenna design procedure as well as simulation and measurement results are presented.

At millimetre-wave frequencies, the discrepancy between simulation and measurement comes from the relative permittivity tolerance and fabrication tolerance. This discrepancy can mainly cause resonant frequency shift. A tunable waveguide-to-microstrip transition for the W-band antenna is proposed to overcome this discrepancy. A typical transition consists of a microstrip probe on a substrate and a waveguide back short in a fixed structure. The tunability has been designed by making a movable back short through WR-10 waveguide. This design can change the back-short distance mechanically to tune resonant frequency. The tunability of this design has been verified with a W-band substrate integrated waveguide (SIW) slot array radar antenna.

This paper presents a multi-input multi-output (MIMO) radar with simultaneously transmitted orthogonal waveforms. The radar operates in W-band, 93.5–94.5 GHz, with frequency-modulated continuous wave (FMCW) signals. The radar is designed to be capable of simultaneous transmission rather than switching transmit channels. A suitable orthogonal waveform transmission method for the FMCW radar is selected and reflected in the transceiver design. The radar consists of a transceiver, antennas, and a signal processor. The design and specifications of each module are described in detail. The transceiver consists of two transmitting channels and two receiving channels. The transmitter is designed to have high transmit power aiming at the detection and imaging of objects with small radar cross section, up to 100–150-m range. A compact horn antenna and two-channel analog-to-digital converter with a high sampling rate are designed and fabricated. The performance of each module is measured and evaluated. The performance of the radar is tested through experiments. The MIMO capability of the radar was verified through the acquisition of the range profiles with respect to four distinct signal paths by distinguishing the simultaneously transmitted orthogonal signals. The experimental results verified that the specification of the radar system is feasible for high-resolution imaging applications.

In this letter, a tunable protection switch device using open stubs for $X$ -band low-noise amplifiers (LNAs) is proposed. The protection switch is implemented using p-i-n diodes. As the parasitic inductance in the p-i-n diodes may degrade the protection performance, tunable open stubs are attached to these diodes to obtain a grounding effect. The performance is optimized for the desired frequency band by adjusting the lengths of the microstrip line open stubs. The designed LNA protection switch is fabricated and measured, and sufficient isolation is obtained for a 200 MHz operating band. The proposed protection switch is suitable for solid-state power amplifier radars in which the LNAs need to be protected from relatively long pulses.

A new method for suppressing surface waves on a millimetre-wave microstrip array antenna is presented. A 10 × 2 patch array antenna is designed at 77 GHz for W-band radar applications. Complementary split ring resonator (CSRR) has been designed at 77 GHz, etched on the antenna ground plane. Simulation and experimental results are compared in terms of the gain and the side lobe level with and without CSRR. CSRR between series patch antenna array could suppress surface waves effectively so that this approach enhances the gain and reduces the side lobe level. The measured gain improvement in the antenna with CSRR is 2.5 dB. The side lobe level of the antenna with CSRR is reduced up to 3.5 dB lower than antenna without CSRR.

This paper presents a new approach to analyzing a Rotman lens for imaging applications. The optical transfer function (OTF) is used to analyze the imaging capability of a Rotman lens. The variations in optical transfer function and the image pattern were calculated with variations in the design parameters due to beam-port spacing, antenna spacing, array size, and so on. As a result, it was found that the cutoff frequency corresponds to the array size in ?, and the resolution is the inverse of the cutoff frequency. The beam-port spacing should be narrow enough to avoid aliasing. For a typical design in which the antenna spacing is ?/2 and the scanning angle is from ?45° to 45°, the number of beam ports should be ?/2 times greater than the number of array ports to avoid aliasing, and the antenna spacing should be less than 0.707? to avoid grating lobes. For the first time, a Rotman lens has been analyzed in terms of the optical transfer function. As a result, important criteria for designing a Rotman lens are presented for imaging applications. This analysis will provide guidance to the design and estimation of a focal-plane antenna array, as well as a Rotman lens for imaging and sensing applications.

A compact microwave radiator is proposed for the treatment of a superficial tumor in a noninvasive hyperthermia application. The proposed radiator is designed to simplify treatment of relatively small tumors by reducing the physical size of the radiator. The proposed radiator is reduced to a size of 27.2×27.2 mm 2 , which corresponds to 0.038 λ×0.038 λ at 433 MHz, so as to induce the optimal heating area for approximately 30-mm tumors, and is studied using a phantom as a model to analyze the thermal characteristics for the human body. The concept of effective treatment area (ETA) is defined in this letter in order to evaluate the area that can be sufficiently heated. The specific absorption rate (SAR) and temperature are uniformly formed on the phantom surface with a symmetrical and circular-shaped distribution. An ETA ratio of 91.6% is achieved for the measurements, corresponding to a 30.4-mm diameter, and the temperature increase required for tumor necrosis is achieved.

Peanut allergy is IgE-mediated type-I hypersensitivity, and T helper 2 cytokines are central to those pathogenesis. We investigated the effects of the administration of chitin and chitosan on peanut-induced hypersensitivities in mouse food allergy models. Chitin and chitosan protected mice against peanut-induced anaphylaxis reactions, and the peanut-specific IgE production decreased by up to 47% with the administration of β-chitosan. The levels of IL-5, IL-13, and IL-10 were significantly suppressed in all groups (α-chitin≥β-chitin≥β-chitosan). These results suggested that the administration of chitin and chitosan from by-products of food processing are beneficial for the prevention of food allergies.

This paper introduces a new design for a Rotman lens that has been proposed to minimize its size and provide a suitable design for a compact beamforming system. The size reduction is realized by minimizing the length of the transition structures, which are positioned between the lens body and the connecting lines. The proposed structure is much shorter than a conventional transition structure, which is a tapered line in general. As a result, a 45% size reduction can be achieved by using the proposed transition structure, compared to a typical Rotman lens with linearly tapered lines. Therefore, the proposed Rotman lens will be suitable for compact beamforming systems.

In this paper, two types of microstrip array antenna for radars operating at 77 GHz are presented. The first type of array antenna is 10×4 elements rectangular patch array antenna with overall size of 20.43mm×7.83 mm. Unit element of this antenna type is a rectangular patch. Series-fed column of 10 unit elements are arranged into 10 × 4 arrays by implementing simple power divider structure. The second type of antenna is 12 × 4 elements leaf array antenna with overall size of 16.72mm×10.75 mm. Unit element of the second antenna type is a rectangular patch that is inclined 45° from the microstrip line axis. Twelve patches are arranged on both sides of the microstrip line and are connected directly at their corners. One additional patch at the end of the structure acts as a matching element. Array consisting of 12×4 unit elements are created by implementing simple power divider structure. Both types of antenna are combined with different types of waveguide-to-microstrip transition consist of two metal layers printed on a single dielectric substrate. The waveguide-to-microstrip transitions are fed by WR10 standard waveguide. The performances of both antennas are verified via simulations and measurements. The rectangular patch array antenna has 19.8 dB gain and 20° × 10° beam width at 77 GHz, while the leaf array antenna has 19.6 dB gain and 19° × 11.6° beam width at 77 GHz. Both types of antenna can be further developed as a reference for designing antenna for radar systems operating at higher frequencies, such as 94 GHz.

This paper presents a new design to realize a compact Rotman lens-fed antenna array. The lens-fed antenna has the form of two layers, which is a new approach to reducing the size of the Rotman lens. The approach is demonstrated at 24 GHz aiming for an automotive sensing radar. The lens consists of a top metal layer, a dielectric, a common ground, a dielectric, and a bottom metal layer, in sequential order. The layout of the lens body is placed on the bottom layer and the antennas are placed on the top layer. Both of them are electrically connected through slot transitions. This two-layer structure reduces not only the total size of the lens, but also the loss of the delay lines because the lines can be designed to be as short and straight as possible. The two-layer Rotman lens-fed antenna array is measured in terms of scattering parameters and beam patterns. From the scattering parameters, the power efficiencies of the beam port 1, 2, and 3 at 24 GHz are obtained as 32.3%, 48.5%, and 50.8%, respectively. The measured beam patterns show that the beam directions are -28.1°, -14.9°, 0°, 15.5°, and 28.6° and the beamwidths are 13.4°, 13.2°, 12.8°, 13.5°, and 13.0°. The measurements confirm that the compact two-layer Rotman lens has been successfully demonstrated.

An asymmetric ground Rotman lens is presented in this letter. A new design of a Rotman lens is proposed to accommodate a whole beamforming system by providing separate ground layers for antennas and circuits. The lens has three dielectric layers and four metallic layers. The prototype of the lens consists of seven array ports, five beam ports, and six dummy ports. The measured return losses show that all the beam ports are matched to better than 12 dB in the band of interest from 23 to 25 GHz. The radiation patterns were measured in a near field measurement system. It shows that the beam directions are $-25^{\circ}$ , $-13.6^{\circ}$ , 0.2 $^{\circ}$ , 12.4 $^{\circ}$ , and 24.5 $^{\circ}$ , respectively and the beam widths are 14 $^{\circ}$ , 13.8 $^{\circ}$ , 13 $^{\circ}$ , 13.4 $^{\circ}$ , and 14.1 $^{\circ}$ , respectively. These results are in good agreement with the simulation. Thus, it is verified that the asymmetric ground lens is one of the best solutions for a compact beamforming system.

Wafer-scale beamforming lenses for future IEEE802.15.3c 60 GHz WPAN applications are presented. An on-wafer fabrication is of particular interest because a beamforming lens can be fabricated with sub-circuits in a single process. It means that the beamforming lens system would be compact, reliable, and cost-effective. The Rotman lens and the Rotman lens with antenna arrays were fabricated on a high-resistivity silicon (HRS) wafer in a semiconductor process, which is a preliminary research to check the feasibility of a Rotman lens for a chip scale packaging. In the case of the Rotman lens only, the efficiency is in the range from 50% to 70% depending on which beam port is excited. Assuming that the lens is coupled with ideal isotropic antennas, the synthesized beam patterns from the S-parameters shows that the beam directions are -29.3°, -15.1°, 0.2°, 15.2°, and 29.5 °, and the beam widths are 15.37°, 15.62°, 15.46°, 15.51°, and 15.63°, respectively. In the case of the Rotman lens with antenna array, the patterns were measured by using on-wafer measurement setup. It shows that the beam directions are -26.6°, -21.8°, 0°, 21.8°, and 26.6° . These results are in good agreement with the calculated results from ray-optic. Thus, it is verified that the lens antenna implemented on a wafer can be feasible for the system-in-package (SiP) and wafer-level package technologies.

We propose a dual-band antenna using a crooked U-slot with radial stub feeding. This antenna has a simpler topology than other antennas designed for realizing dual-band characteristics. In addition, the proposed antenna adjusts to desired frequencies easily. The crooked U-slot made on the bottom layer provides the advantage of making impedance matching possible over a wide band at the low frequency, while the radial stub is used for feeding and also for providing additional resonance at the high frequency. The operating frequencies of the proposed antenna are chosen as 2.4 and 5.2 GHz, obtained by optimizing the physical dimensions of the crooked U-slot and radial stub. Measured results of return loss show -26.2 and -12.2 dB at 2.4 and 5.2 GHz, respectively. Measured gain is 0.47 and -1.97 dBi at 2.4 and 5.2 GHz, respectively.

outphasing class-E power amplifier using composite right/left-handed transmission lines(CRLH-TL) is proposed at 2.4 GHz. The power combiner including CRLH-TL is designed to suppress the second and third harmonics to increase linearity and the output problem of the conventional outphasing amplifier is also solved by the proposed outphasing amplifier. So the P AE is improved. The measured maximum output power at the fundamental frequency shows 31.8 dBm, whereas the PAE shows 50 % with 14 dBm input power excited. The IMD3 is improved by 5 dB compared to that of conventional outphasing amplifier.

This paper presents full-scale laboratory tests on a monolithic and spliced simply supported precast box girder. The main objective of the paper is to investigate the static behavior of a prestressed concrete (PSC) girder that has been spliced with precast box segments. A 20 m full-scale spliced PSC girder was fabricated and tested to compare its static performance against a monolithically fabricated girder. The monolithic girder has the same geometric and material properties as the spliced girder. Static characteristics of the spliced girder are presented, including the internal strain, deflection, interface behavior, neutral axis position, and crack patterns. The results were compared to those obtained from a monolithic girder. It is shown that the spliced girder provides static performance comparable to that of a monolithic girder in the elastic range. No joint failure was observed in the spliced girder up to the final load stage.

A concurrent dual-band class-E power amplifier using composite right/left-handed transmission lines (CRLH TLs) is proposed. Dual-mode operation is achieved by using the frequency offset and nonlinear phase slope of CRLH TLs for the matching network of power amplifiers. The frequency ratio of two operating frequencies is not necessarily an integer. Two operating frequencies are chosen as 836 MHz and 1.95 GHz for simulation. Three methods for designing a CRLH TL power amplifier are proposed. The measured results based on one method show that output powers of 22.4 and 22.2 dBm were obtained at 800 MHz and 1.70 GHz, respectively. In terms of maximum power-added efficiency, we obtained 42.5% and 42.6% at 800 MHz and 1.70 GHz, respectively.

Ring resonators have been widely used for various applications. Dual-mode ring resonators have also been investigated due to their applicability to multifrequency mode requirement. In this paper, dual-mode ring resonators using a branch line are designed along with a systematic approach. Triple-mode branch-line ring resonators are also designed adding two branch lines to the ring resonator. Adding more branch lines, multimode resonators can be realized based on the design procedure developed here. The location of the branch lines determines the additional resonant frequencies other than the fundamental resonant frequency generated by the enclosing ring. Furthermore, half-ring resonators working at 2.5 GHz are proposed for suppressing multiple harmonics (second and third harmonics) and providing size reduction with employment of various physical configurations. Equalizing the even- and odd-mode phase delays, harmonics are suppressed effectively in the design of half-ring resonators. Double half-ring resonators with a long opening gap are investigated to continuously decrease the resonant frequency. An open-loop structure provides flexible design and lowers the resonant frequency. Two dual-mode ring resonators and one triple-mode ring resonator are simulated and fabricated along with three different half-ring resonators

This letter describes a design of an internal quad-band antenna resonating at cellular (824~894 MHz), DCS/PCS (1710~1880 MHz/1850~1990 MHz), and WiBro (wireless broadband Internet, 2300~2390 MHzs) system band by inserting the spiral slits corresponding to the resonant frequencies. In order to accomplish this goal, double-spiral structures are suggested and analyzed by using a commercially available software package based on the finite-difference time-domain (FDTD) algorithm and basic equation for fundamental resonant frequency. In addition to that, the experimental results are compared with the predicted data obtained from the software package, CST MW Studio by considering the criterion of VSWR as 3:1. The proposed antenna and substrate are so small that they can be mounted and packaged in mobile phones. The measured radiation patterns are in good agreement with simulated results

Vascular smooth muscle contraction is mediated by activation of extracellular signal-regulated kinase (ERK) 1/2, an isoform of mitogen-activated protein kinase (MAPK). However, the role of stress-activated protein kinase/c-Jun N-terminal kinase (JNK) in vascular smooth muscle contraction has not been defined. We investigated the role of JNK in the contractile response to norepinephrine (NE) in rat aortic smooth muscle. NE evoked contraction in a dose-dependent manner, and this effect was inhibited by the JNK inhibitor SP600125. NE increased the phosphorylation of JNK, which was greater in aortic smooth muscle from hypertensive rats than from normotensive rats. NE-induced JNK phosphorylation was significantly inhibited by SP600125 and the conventional-type PKC (cPKC) inhibitor Gö6976, but not by the Rho kinase inhibitor Y27632 or the phosphatidylinositol 3-kinase inhibitor LY294002. Thymeleatoxin, a selective activator of cPKC, increased JNK phosphorylation, which was inhibited by Gö6976. SP600125 attenuated the phosphorylation of caldesmon, an actin-binding protein whose phosphorylation is increased by NE. These results show that JNK contributes to NE-mediated contraction through phosphorylation of caldesmon in rat aortic smooth muscle, and that this effect is regulated by the PKC pathway, especially cPKC. Keywords:: c-Jun N-terminal kinase, mitogen-activated protein kinase, vascular smooth muscle contraction, caldesmon, hypertension

A new form of a Rotman lens is proposed for microwave/millimeter-wave applications such as a collision-avoidance radar. The proposed lens can be described as a dielectric slab fed by slot lines. The new form is expected to show lower loss and lower mutual coupling than the conventional Rotman lenses fabricated with conducting plates at millimeter-wave frequency. Taking the field distribution inside the dielectric slab into account, the TE/sub 0/ mode was chosen to excite the dielectric slab lens. The dielectric Rotman lens consists of a dielectric slab, tapered slot structure, and the transitions between the antipodal slots and microstrip lines for subminiature A connectors. The conventional design equations have been modified for use in designing the dielectric slab Rotman lens with a high dielectric material. A prototype was implemented with nine beam ports and nine array ports. Measurements from 10 to 20 GHz show that mutual coupling can be lowered at higher frequency. The obtained efficiency of the dielectric slab lens system is approximately 30%. The efficiency of the lens is comparable to that of the conducting plate lenses even though there is a spillover loss from the dielectric slab.

The role of mitogen-activated protein kinase (MAPK) in increased basal tone –spontaneous resistance in vascular muscle strips– was clarified in aortic smooth muscle from deoxycorticosterone acetate (DOCA)-salt hypertensive rats. The MAPK/extracellular signal-regulated protein kinase (ERK) kinase inhibitor, PD098059 (2′-amino-3′-methoxyflavone), significantly inhibited basal tone in a dose-dependent manner. The basal level of ERK1/2 activation was inhibited by PD098059 and was significantly greater in hypertensive rats than in sham-operated rats. In contrast, inhibition with PD098059 was not observed in sham-operated rats. GF109203X (2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)maleimide), an inhibitor of protein kinase C (PKC), decreased both basal tone and ERK1/2 activity in the hypertensive rats. In contrast, Y27632 ((R)-(+)-trans-N-(4-Pyridyl)-4-(1-aminoethyl)cyclohexanecarboxamide) and verapamil, inhibitors of Rho kinase and voltage-dependent Ca2+ channels, respectively, significantly inhibited basal tone but not ERK1/2 activity. Thus, basal vascular tone is elevated by the altered activation of MAPK in DOCA-salt hypertensive rats, and this is regulated by PKC, but not by Rho or intracellular Ca2+.

We determined the contribution of the Rho family of low molecular GTP-binding proteins to phorbol ester-induced contraction in swine pulmonary artery smooth muscle. In Ca2+-free medium containing 1 mM EGTA, 12-deoxyphorbol 13-isobutyrate (DPB, 1 microM), a protein kinase C (PKC) activator, elicited sustained contractions, which were not inhibited by treatment with verapamil, a voltage-dependent Ca2+ channel antagonist, and Y27632, a Rho-associated kinase inhibitor. Immunoblot analysis showed three PKC isoforms (alpha, epsilon, and zeta) and two Rho GTPases (RhoA and Cdc42) in both cytosolic and the membrane fractions from quiescent strips. DPB (1 microM) significantly induced PKCalpha and epsilon to translocate from the cytosolic to the membrane fraction in Ca2+-free medium. DPB also elicited the translocation of Cdc42, but not RhoA to the membrane fraction. Similarly, in the experiment for measurement of Rho GTPase activity by pull-down assay, DPB (1 microM) significantly increased the activity of Cdc42 in Ca2+-free medium. Norepinephrine (NE, 10 microM) stimulated the redistribution of RhoA from the cytosolic to the membrane fraction in swine pulmonary artery smooth muscle. In contrast, NE did not alter the subcellular distributions of Cdc42 and the PKC isoforms. These results indicate that phorbol ester evokes PKC-mediated Ca2+-independent contraction via a Rho GTPase pathway, especially Cdc42, in smooth muscle from swine pulmonary arteries.

This paper presents a new analysis of a Rotman lens as an imaging processor. The modulation transfer function (MTF) has been calculated with the variation in the beam port spacing. The cutoff frequency is equal to the array size in λ. The beam port spacing should be narrow enough to avoid the aliasing.

The penetration enhancement of non-invasive microwave hyperthermia applicator is presented. The 915 MHz branched dipole element used for planar array. The E-field from the single element determines the input phase and power of array applicator. The SAR ratio between surface and target depth is dominant for temperature distribution. The 5 cm effective treatment depth is achieved with 3-dimensional temperature simulation.

This letter presents a novel dual-band balun using the branch-line configuration. We establish design equations for dual-band balun based on the even-odd mode method. The proposed circuit operates at 2.45 GHz and 5.25 GHz. The single-ended power is divided differentially at the balanced ports. The insertion losses (S21 and S31) show around −2.7 dB to −4.3 dB at the two different frequencies. The phase difference between the balanced ports shows maximum 3° deviation from 180°. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 642–644, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24996

In this letter, the design procedure and electrical performance of a dual band (2.4/5.8GHz) printed dipole antenna using spiral structure are proposed and investigated. For the first time, a dual band printed dipole antenna with spiral configuration is proposed. In addition, a matching method by adjusting the transmission line width, and a new bandwidth broadening method varying the distance between the top and bottom spirals are reported. The operating frequencies of the proposed antenna are 2.4GHz and 5.8GHz which cover WLAN system. The proposed antenna achieves a good matching using tapered transmission lines for the top and bottom spirals. The desired resonant frequencies are obtained by adjusting the number of turns of the spirals. The bandwidth is optimized by varying the distance between the top and bottom spirals. A relative position of the bottom spiral plays an important role in achieving a bandwidth in terms of 10-dB return loss.

A new form of a Rotman lens has been proposed for applications above 10 GHz, such as a collision avoidance radar. The proposed lens can be described as a dielectric slab fed by slot lines. The new form is expected to show lower loss and lower mutual coupling than the conventional Rotman lenses at higher frequency than 10 GHz. The prototype was implemented with nine beam ports and nine array ports. The measurements show that the mutual coupling can be lowered at higher frequency, and that the efficiency of the dielectric slab lens of about 30% can be obtained. We conclude that the dielectric lens is comparable to the conducting plate lens even though a spillover loss is presumed at frequency of the implementation.

As the design and fabrication of high-frequency microwave components are developed, many applications are recently proposed in millimeter-wave band. The applications are communications, imaging, sensing, and RF power delivering in which new conceptual approaches, retrodirective or phase conjugating array, have been also considered. One of emerging technologies is a passive millimeter-wave (PMMW) imaging system [1]. The key aspect of the PMMW imaging system is its penetration capability. Different from the optical imaging system, the PMMW imaging system can form images in low-visibility conditions such as night, foggy weather, clouds, and even though cloths. This characteristic is useful for many applications in both commercial and military areas.

This paper presents a balanced K-band (18 to 27 GHz) Self-Oscillating Mixer (SOM) with 0.18µm CMOS technology. The proposed SOM employs a push-push configuration for the oscillating function which is designed to operate at K-band. Using the push-push configuration, a K-band frequency of 22.57 GHz is achieved. The proposed SOM uses an RF frequency of 23GHz, and generates a self-oscillation frequency of 11.28 GHz, a push-push frequency of 22.57 GHz and an IF frequency of 386.3 MHz from a 1.8 V power supply. The proposed SOM has an output power of −46 dBm (Pin = −40 dBm) at IF frequency, the gain of −6 dB and the P1dB of −15 dBm.

A Ka-band cross-coupled push-push LC Voltage Controlled Oscillator (VCO) with a novel feedback configuration is proposed to improve the phase noise performance. The main idea of the proposed novel feedback configuration is to increase negative conductance and cancel the loss conductance of LC tank. Conductance of LC tank decreases Q-value. Therefore, decreased total conductance increases Q-value in LC tank, which improves phase noise performance of the proposed VCO. The VCO is simulated in 0.18 µm CMOS technology with 1.8 V voltage supplied. The output power is −7.95 dBm at 24GHz. The phase noise shows about −111.0 dBc/Hz at 1 MHz offset frequency. The tuning range is observed about 2.29 GHz from 22.5 GHz to 24.79 GHz.

Down conversion mixer converts the high frequency RF signal to the low frequency signal. In this work, a 24GHz dual-gate mixer using sub harmonic is proposed to eliminate the DC offset and to achieve the high LO-RF isolation. The main idea of the proposed mixer is to achieve the sufficient conversion gain and isolation using the proposed LO sub-harmonic structure, also to reduce the required supply voltage using dual-gate mixer with appropriate bias point. It is fabricated using CMOS 0.18 µm technology. With an RF input signal at 24GHz, and an LO signal at 11.7GHz, an intermediate frequency of 600MHz is produced. We obtained under 8.3mW power consumption and 10dB conversion gain. Also, we obtained upper 54dB RF-LO isolation.

As the development for Terahertz (THz) system is highly demanded, the detecting antenna requires a very high input impedance for a good matching with the photomixer. The detecting antenna is connected to the photomixer, requiring very high input impedance, so that the impedance matching between these two elements is significantly important. We propose a Log-Periodic antenna for high input impedance which operates in the sub-THz frequency range. The proposed antenna achieves a high input impedance of approximately 1000Ω at the resonant frequency of 72 GHz.

We report a millimeter wave super lens based on the left-handed metamaterial using split-ring resonator (SRR) and complementary SRR (CSRR). The millimeter wave cannot propagate far away due to short wavelength. Therefore, the system for THz or millimeter wave band demands the lens to obtain strong focused signal from weak waves caused by scattering in atmospheric environment. The proposed left-handed metamaterial (LHM) lens based on SRR and CSRR can be designed by scanning the focal point of flat LHM lens in the region under detection and screening directly the field intensity distribution of backscattered millimeter wave refocused by the flat LHM lens. The simulation results confirm that this lens exhibits a focus with strong E-field distribution.