A technique for converting a wide-band coplanar waveguide fed antenna to UWB by positioning slots in the modified ground plane (MGP) adjacent to the feed is proposed in this paper. The slots can be symmetrically or asymmetrically positioned for optimum performance. One slot pair is initially positioned through parametric analysis in the modified ground plane at an equal distance from the feed end for the maximum achievable impedance bandwidth. The second slot pair is similarly positioned, optimising the antenna for ultra wideband operation. Two CPW fed antenna geometries are experimented using the technique, one unique and the other, a generic circular monopole. Both antennas have MGP and are fabricated on an FR4 substrate. The analysis and simulation have been done in FEM based High Frequency Structure Simulator (HFSS). The performance of the two antennas is measured with a Vector Network Analyzer ‘Agilent PNAE8362B'. The impedance bandwidth and radiation pattern validate the performance of the antennas for ultra wideband applications. The experimentally obtained bandwidth precisely covers UWB, and principal patterns are uniform throughout the band.
In this paper, we propose a novel interconnection technique for a flip-chip quad flat no-lead (FC QFN) package which can decrease the amount of the transmission line (TL) phase shift. The RF die inputs and outputs (I/O) are connected to the package lead fingers by a small size, 1000 μm length, microstrip line having a gap capacitor consisting of staked plates (fingers) where the space in between is filled by a ceramic material of 10.2 dielectric constant value. This technique can reduce the effect of transmission line inductance and makes the novel package interconnection behaving as a composite left right handed (CLRH) TL; hence, one can set the TL phase shift to zero degree at the desired operating frequency band (i.e. S-band) by just tuning geometrical and/or physical interconnection structure parameters.
Nonlinear characteristics of semiconductor devices play a key role in the performances of circuits, but their modelling is still a big challenge in circuit simulations nowadays. This paper explores modelling nonlinear characteristics of circuits containing semiconductor devices by presenting a modified physically based simulation method. A p-i-n diode microstrip circuit is taken as a sample, and its nonlinear characteristics, such as the power limiting, bistability, and forward recovery characteristics, are simulated and analysed. The applied method demonstrates its good capability and accuracy of modelling the nonlinear characteristics in the simulation, and moreover clarifies the underlying physical mechanisms. In contrast, the Advanced Design System (ADS) software, a popular circuit simulation program based on the equivalent circuit model, fails to reveal some of those nonlinear characteristics.
Based on metamaterials and compressive sensing theory, we design a single pixel millimeter-wave fast imaging system by a 1D aperture array. The aperture array is realized by a column of complementary electric-lc (cELC) units etched on amicrostrip transmission line. Each cELC unit resonates at a different frequency, where the energy is coupled from the aperture to free space. A sequence of random field patterns can be obtained by controlling geometric parameters of each cELCunit. We use the frequency as the index of measurement matrix which well satisfies the restricted isometry property (RIP) and is well suited for compressive sensing (CS). A prototype of CS imaging system operatingatKa-band (27-40 GHz) is fabricated which can detect a 5 cm * 5 cm object precisely at a distance of 50 cm.
An extremely wideband photonic crystal antenna is proposed with a very compact size of 16.6 x 26.6 x 0.9mm3. The double-layer materials of silicon and glass are selected as the antenna substrate. The band gap performance of photonic crystals can decrease electromagnetic wave absorption of silicon substrate, restrain surface wave loss of antenna, and increase electromagnetic wave space radiation. Hence the periodical photonic crystal with square lattices is applied in upper silicon substrate. The glass substrate not only decreases effective dielectric constant of antenna, but also supports silicon substrate with photonic crystal. MEMS processes are used to realize photonic crystal antenna with plenty tiny through-holes. The simulated and measured results demonstrate that photonic crystal can effectively expand the working bandwidth of base antenna.
A compact directional MIMO antenna operating in 2.4 and 5 GHz wireless local area network (WLAN) bands is presented. The compactness of the proposed multiple-input multiple-output (MIMO) antenna can be attained through using miniaturized antenna elements and meanwhile employing an extremely narrow edge-to-edge inter-element space (3 mm). Two novel miniaturized planar inverted-F antenna (PIFA) elements which share a common ground are designed, and each element has a dimension of 31 mm × 17 mm and a profile of 4.2 mm. By etching three slots on the ground, the port isolation can be significantly enhanced, which can even reach a maximum of 54 dB at 2.45 GHz. A desirable directional radiation pattern is obtained, and the calculated envelope correlation coefficient is better than 0.01.
This paper presents the development and design of flexible and conformal printed monopoles antennas. The main objective is to control the level of radiation in broadside antenna from zero to a maximum by changing the curvature of printed board. Two printed antennas types are considered: thin wire and disk monopole. Furthermore, with the curving radius R increasing, the classical null on the broadside radiation pattern disappears gradually for both wire and disk. Increasing the curvature radius of conformal flexible antenna, and keeping all other parameter's value, wire monopole antenna becomes mismatched while the disk monopole antenna remains matched for all radius of curvature. The simulated results of various monopoles are compared successfully with measurements.
This study proposes an anti-jamming scheme for linear frequency modulated (LFM) radars to combat smart noise jamming, which is a newly proposed pattern that is very effective against LFM radars. First, by utilizing the smeared spectrum technique, the chirp rates of the target return and jamming signal can be changed. The target return and jamming signal then exhibit different characteristics after the application of matched filters. Finally, the true target can be distinguished from the smart noise jamming, which is suppressed by the reconstruction and subtraction in the receiving signal. Numerical experiments demonstrate the feasibility and practicability of the proposed anti-jamming device, which is also verified as having a superior performance over existing jamming suppression schemes.
Light sheet microscope is a versatile imaging tool for high imaging speed and signal to noise ratio (SNR). In this type of system, the illumination is perpendicular to the direction of detection. Due to its structural feature of perpendicular detection, the SNR is comparable to total internal reflection fluorescence (TIRF) microscopy. Therefore, the perpendicular detection system is of great application prospect. In this paper, we develope a compact optical perpendicular detection system, which can not only be utilized to measure fluorescence with high SNR, but also capture a fluorescent image of flow fluorophore.
In this paper, a simple broadband circular polarization (CP) V-shaped slot antenna is developed. The CP antenna consists of Z-shaped feedline with a stub and a patch, and symmetrically etched two rightangled V-shaped slots (an open slot and a closed slot) along the center line. The stub is introduced for multi-resonances to obtain broadband. The broad CP and impedance bandwidths overlap by the symmetrically etched right-angled V-shaped closed slot along the center line and the Z-shaped feedline placed in a proper position. The measured results show that the proposed antenna has a broad overlapped 3-dB axial ratio (AR) bandwidth and -10 dB impedance bandwidth of 71% (2.19-4.6 GHz).
A new miniaturized microstrip branch-line coupler with good harmonic suppression is proposed in this paper. The new structure has two significant advantages, which not only effectively reduces the occupied area to 20.4% of the conventional branch-line coupler at 0.96 GHz, but also has high 6th harmonic suppression performance. The measured results indicate that a bandwidth of more than 120 MHz has been achieved while the phase difference between S21 and S31 is within 90° ± 1°. The measured bandwidth of |S21| and |S31| within 3 ± 0.3 dB are 145 MHz and 150 MHz, respectively. Furthermore, the measured insertion loss is comparable to that of a conventional branch-line coupler. The new coupler can be easily implemented by using the standard printed-circuit-board etching processes and is very useful for wireless communication systems.
A low-cost wideband textile antenna based on the substrate integrated waveguide (SIW) technology is proposed, and a pure copper taffeta fabric etched on a woolen felt substrate is used to realize the presented antenna. The impedance matching frequency band for the designed structure is from 2.27 GHz to 3.61 GHz, which is significantly improved compared with previous studies. The operational principle of the proposedquasi-Yagi textile antenna is also described in this paper. The antenna is fabricated and measured, and a good agreement is achieved between the simulation and experimental results. The designed antenna has themaximum gain and efficiency of 4.2dB and 84%, respectively. According to its compactness, low-cost and low-weight specifications, the proposed antenna is a good candidate for being utilizedin wearable communication devices.
This paper presents the design and implementation of dual-band filters. The proposed method works well for dual-band filters with asymmetric dual-passband, high selectivity, and pre-assigned in-band return loss levels (e.g. equal or un-equal at two frequency bands). To verify the design concept, a prototype dual-band filter using combline coaxial cavity-type resonators was designed, fabricated and tested. Good agreement has been achieved among the theoretical synthesis results, simulation results and measurement results.
A low profile dual-polarized omnidirectional antenna with an overall height of 80 mm is presented in this paper for broadband indoor distributed antenna system (IDAS). The proposed antenna consists of an improved discone antenna for vertical polarization (VP) and a printed dipole array with five pairs of dipoles for horizontal polarization (HP). The VP element is a combination of three radiation patches, a cone-shaped feeding structure, a circular shorted loading patch and a coupling ring. By loading the coupling patch and coupling ring over the top and at the bottom of the radiation patches, the bandwidth for VP is significantly enlarged while the antenna height is reduced. Simulated and measured results indicate that the operating bands of 0.86-5.62 GHz for VP and 1.62-2.71 for HP are realized. Omnidirectional radiation patterns in horizontal plane for HP and VP, good port isolation of greater than 26 dB, low cross polarization level, and stable gain (2.6-5.6 dBi for VP and 2.8-4.2 dBi for HP) are achieved during the operating bands, which demonstrate the proposed antenna can be widely used for broadband IDAS.
A slotted meander line printed monopole antenna for low frequency applications at 878 MHz is presented. The operating frequency of the conventional printed monopole antenna is greatly reduced by the presence of the slots and meander line which lead to the reduction of the antenna size. The size reduction up to 70% compared to the conventional reference antenna is achieved in this study. The antenna has a simple structure and small antenna size of 46.8 mm × 74 mm or 0.137λ0 x 0.217λ0. The antenna has been fabricated on a low-cost FR4 substrate and measured to validate the simulation performances. Measured results display that the proposed antenna produces omnidirectional radiation pattern of impedance bandwidth of 48.83 MHz and the maximum gain of -1.18 dBi.
A printed loop antenna with a circularly polarized beam parallel with its plane is proposed. The proposed quadrangle loop antenna is fed with microstrip line at one of its corners. The microstrip line part and loop part provide vertical polarization and horizontal polarization, respectively. The proposed antenna is simple in structure and can be easily integrated with other microwave components on the same substrate. Simulated results show that the proposed antenna has a wide impedance bandwidth (|S11| < −10 dB) and wide 3-dB AR bandwidth ranging from 8.0 to 10.5 GHz (27%). A prototype of the proposed antenna is fabricated and tested. The measured and simulated results have good agreement.
In this paper, a second-order decoupling design using a resonator and an interdigital capacitor is proposed for an MIMO antenna pair in mobile terminals. The proposed antenna pair consists of an interdigital capacitor and an open loop resonator. By properly combining the responses of the resonator and interdigital capacitor, a second-order decoupling performance can be achieved. Meanwhile, isolation between the two antennas is increased by at least 15 dB within the frequency band of interest, from -5 dB to -20 dB. Moreover, the decoupled antenna pair maintains good impedance matching performance from 2.4 GHz to 2.5 GHz. The proposed decoupled antenna pair and its coupled counterpart have been fabricated and measured. The measured results agree with the simulation ones. The proposed MIMO antenna pair is an eligible candidate for Wi-Fi MIMO applications in the 2.4 GHz band.
This paper presents a C-band wide stopband bandpass filter (BPF) using quarter mode substrate integrated waveguide (QMSIW) cavities. The BPF is simply constructed by combining S-shaped slot and L-shaped slot loaded quarter-mode substrate integrated waveguide. A special negative coupling scheme with symmetrical S-shaped slots on the top and bottom metal planes connected by metallic vias is developed. The proposed structure provides more design flexibility in arranging the pitch of vias owing to the extended slot length. The filter has fractional bandwidth of 25% at center frequency of 5.5 GHz with return loss better than 24 dB and insertion loss less than 1.1 dB. Moreover, its first spurious response occurs at 22.5 GHz (about four times the central frequency), exhibiting an extremely wide stopband performance. An experimental SIW filter was fabricated, and good agreement was achieved between the simulated and measured results.
An asymmetric stepped-impedance ring resonator (ASIRR) is proposed for the design of a triple-bandpass filter. This resonator is applied to creat the former two passbands by utilizing a stepped-impedance circular ring and the third passband by introducing two asymmetric coupling structures. It is found that the S-parameter performance can be improved by adding a pair of shorted and open stubs, the second passband and the stopbands on both sides of the third passband can be tuned by adjusting the length of open stubs. A prototype filter operating at 1.04, 3.52 and 5.57 GHz is designed, fabricated, and measured with the corresponding fractional bandwidths of 23.1%, 7.4%, and 4.1%. Good agreements between the simulated and measured results are achieved for the ASIRR filter. Also, four transmission zeros are generated.
Magnetic induction tomography has been under consideration for imaging electrical conductivity distributions within the human body. Multi-coil systems are most commonly employed for this task, requiring a numerical solution of Maxwell's equations at each position of the coil array. An alternative uses a single coil placed near the conductive target while measuring coil self-impedance changes (``coil loss'') at a number of unique locations. Recently, a closed-form solution of Maxwell's equations, in the form of a 3D convolution integral, was found for a single coil consisting of concentric circular loops that relates impedance change to an arbitrary conductivity. Its development required spatially uniform permittivity and permeability, yet showed quantitative agreement with experiment. Here, we provide a much more critical test of the convolution integral in experiments that allow large permittivity changes over coil dimensions. Loss is measured while the coil is placed at known positions relative to plastic columns of variable diameter which are filled with salt solutions of varying conductivity. In all cases, coil loss varies linearly with conductivity and with zero intercept. Quantitative agreement is observed only when column diameter is greater than or equal to coil diameter. Because of linearity, the convolution integral is useful for image reconstruction, though contrast could be either reduced or enhanced in those circumstances when relative permittivity change exceeds ~70.
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