In this paper, we report a new design of a compact antenna based on the use of split ring resonator (SRR). The designed antenna consists of two SRRs, with the same geometrical parameters, printed symmetrically on both sides of the dielectric substrate. Excitation of the SRR element is performed by adequately placing the access microstrip lines with respect to the confinement plane of the split rings. The resonance frequency of the antenna is essentially defined by geometrical parameters of the SRR, which makes it suitable for a broad range of applications spanning from mobile terminals to WLAN and WPAN systems. The final result is low profile, and can be easily integrated with other RF front-end circuits in a PCB.
A novel S-shaped electromagnetic band gap (EBG) middling bandwidth bandpass filter based on substrate integrated waveguide (SIW) was proposed. The filter was designed based on the band-stop characteristics of EBG by etching different dimensional S-shaped on the surface of substrate integrated waveguide. The bandpass filter with a center frequency at 7.765 GHz and relative fractional bandwidth 7.31% shows good bandpass characteristics with frequency band between 7.38~7.94 GHz, while the insertion loss is less than 1.6 dB and achieve middling bandwidth in SIW by EBG and has the advantage of bandpass, low insertion loss, compacted and good selectivity etc. The good agreement between the measured results and the simulated results demonstrates that the design of this proposed filter is effective.
A compact Ka-band broadband waveguide-based traveling-wave spatial power combiner is presented. The low loss micro-strip probes are symmetrically inserted into both broadwalls of waveguide, quadrupling the coupling ways but the insertion loss increases little. The measured 16 dB return-loss bandwidth of the eight-way back-to-back structure is from 30 GHz to 39.4 GHz (more than 25%) and the insertion loss is less than 1 dB, which predicts the power-combining efficiency is higher than 90%. Ka
In this paper, we propose and develop a novel reconfigurable bandpass filter based on microstrip LC resonators. The equivalent circuit model of the proposed filter is presented. The filter can be reconfigured by tuning the capacitance of the microstrip LC resonators. A reconfigurable bandpass filter based on semiconductor varactor diode loaded microstrip LC resonators with a tuning range of 2.496 GHz to 2.937 GHz, and a fractional bandwidth of 6.3% to 8.2% is demonstrated, and the measured insertion loss is 1.7 dB to 3.8 dB. The out-band rejection is better than 25 dB up to 10 GHz.
A probe-fed circularly polarized microstrip patch antenna is presented. By stacking a sot-ring a proper distance above the patch, traveling current along the periphery of the slot-ring is formed. The axial-ratio bandwidth is optimized by varying the size of the slot-ring and the size of the ground plane. Through this simple method, 3-dB axial-ratio bandwidth of 9.8% centered at 915 MHz is achieved for RFID use.
In this article, a fractal-based composite right/left-handed transmission line (TL) is proposed, and its applications in miniaturized negative-order resonant (NOR) antennas are investigated. The TL unit-cell is constructed by etching a Hilbert-fractal slot on the surface of a substrate integrated waveguide structure. The dispersion analysis shows that the proposed TL can be used to design miniaturized NOR antennas. Then, two fractal-based NOR antennas are designed and fabricated. According to the measured results, the electrical sizes of the fabricated open-ended and short-ended antennas are 75.8% and 74.6% smaller than those of the reported counterparts, respectively. In addition, compared with the microstrip patch antennas, the fabricated antennas exhibit similar gain level and radiation patterns, but have a much smaller electrical size.
In this paper a multisphere particle method is developed to estimate the solution of the Poisson's equation with Neumann boundary conditions describing the neuronal human brain activity. The partial differential equations governing the relationships between neural current sources and the data produced by neuroimaging technique, are able to compute the scalp potential and magnetic field distributions generated by the neural activity. A numerical approach is proposed with current dipoles as current sources and going on in the computation by avoiding the mesh construction. The current dipoles are into an homogeneous spherical domain modeling the head and the computational approach is extended to multilayered configuration with different conductivities. A good agreement of the numerical results is shown compared for the first time with the analytical ones.
A novel circularly polarized cavity-backed antenna (CBA) excited by crossed bowtie dipoles is presented in this paper. It is fed by a transition from a microstrip line to double-slot lines. The crossed dipoles consist of a top-loaded triangular and a filleted rhombic to achieve the required input impedance relations for circularly polarized radiation. After optimization, a simulated 3-dB axial-ratio bandwidth of 50% and a broadside gain in a range of 7 to 9 dBi are achieved while the standing wave ratio is kept below 2.
We propose a new architecture for array antennas able to achieve a high-gain performance by using a low number of elements and uniform-amplitude excitations. The solution is realized through a fast and deterministic design technique able to accurately emulate, by exploiting only the feeds' dimensions as degrees of freedom of the synthesis, `ideal' continuous aperture sources fulfilling at best the assigned directivity requirements. The given theory is supported by numerical examples concerning the synthesis of isophoric direct radiating arrays devoted to a multibeam coverage of Europe from a geostationary satellite.
This paper presents a novel waveguide band pass filter using Sierpinski fractal-shaped irises. The bandwidth of the proposed filter is more than 5.5 times in comparison to similar waveguide filter with rectangular shape iris. The offered filter is designed and simulated using Ansoft HFSS and then fabricated. The results show less than 0.5 dB insertion loss and return loss better than 13 dB in operation frequency band for the proposed filter.
Through exploring the relationship between the Q-factor and the normalized electric field strength of a reverberation chamber, this contribution proposes a new kind of methods for the Q-factor estimation, which can simplify the procedure of measuring Q-factor in experiment and raise the e±ciency of calculating Q-factor by simulation. Firstly, the method is validated using measured electric field, then it is verified using data from RC's simulation by FDTD. Satisfactory agreements confirm this kind of methods could act as a reliable tool in evaluating Q-factor by both experimental measurement and numerical simulation.
Inhomogeneous anisotropic cloaks can be approximated by more realizable homogeneous and isotropic material layers at the expense of their bandwidth and angular dependence. Aiming at applications to a monostatic Radar, we propose a scheme to design broadband cylindrical cloaks with minimized backscattering RCS. The cloak is composed of a few layers of concentric magnetic materials, with optimized parameters using a genetic algorithm (GA). We also examine extensively the parameters in the optimization, including the initial population and the relationship of required discretization with the operation frequency. It has been demonstrated that, through a proper designed optimization, the bandwidth can exceed 80% for non-dispersive cloaks and 4% for dispersive cloaks.
Nowadays, there is expanding interest in planar compact microstrip filters applied in microwave wireless system nowadays. The compact microstrip resonant cell (CMRC) and spiral compact microstrip resonant cell (SCMRC) are more and more popular in filter design due to their slow-wave and band-stop effects. In this paper, a novel double-folded SCMRC (DSCMRC) is proposed, analyzed and measured, which turns out to have more compact dimensions and distinctly broader stopband than CMRC and SCMRC. Furthermore, an improved DSCMRC circuit with two parallel open-ended stubs that are added into the DSCMRC structure is presented, which could introduce more transmission zeros in the stopband for better out-of-band rejection than the original DSCMRC. The measured results show the excellent performance of the improved DSCMRC circuit structure. Finally, a novel low-pass filter incorporating two improved DSCMRC in series is simulated and measured, which proves to have an excellent performance of out-of-band rejection up to 25 GHz with a really compact circuit size.
In this paper, two slots which connect with waveguides and a microwave network are studied by using multi-modes technique. A TE incident plane wave is assumed. The moment method is employed to solve the problem. And the mode and triangular functions are used as basic and test functions. A different HM-pattern is obtained. It is found that the microwave network greatly affects the HM-pattern.
A new printed monopole antenna configuration, asymmetric inverted cone ring monopole antenna, is proposed. The proposed antenna which has the size of 23.6 mm x 40 mm, is fabricated on a low-cost FR4 substrate that has the relative permittivity (εr) of 4.4 and substrate thickness of 1.6 mm to operate in the UWB band (3.1 GHz to 10.6 GHz) released by Federal Communications Commission (FCC) in 2002. It gives an ultra-wide impedance bandwidth of VSWR ≤ 2 from 2.9 GHz to 35 GHz (169.4%) for numerical result and from 3.1 GHz to 31.1 GHz (163.74%) for experimental result. Moreover, it exhibits omni-directional radiation patterns with acceptable gain across the whole operation band, which meets the requirements of UWB applications. The parameters which affect the performance of the antenna characteristics are investigated in this paper. The simulated results have a good agreement with the measured ones, and the proposed antenna shows that it is a very good candidate for UWB operations.
A microstrip line fed dual band-reject ultra wideband antenna with sharp band edge frequency of 3.1-10.6 GHz is presented. The antenna consists of a rectangular patch on the front side and a partial ground plane at the rear. A step is cut on the bottom edge of the patch for impedance matching. A split ring slot etched on the radiating patch rejects WiMAX (3.3-3.75 GHz) band, and a pair of inverted S-shaped slot in the partial ground plane rejects WLAN (5-6 GHz) band. In order to eliminate the radiation outside the FCC specified 3.1-10.6 GHz band, a rectangular slot is etched on the ground plane below the feed line. The antenna exhibits UWB band width of 109% except for the notch band. The radiation characteristics are consistent throughout the band. The performance of the antenna is analyzed both in the frequency domain and time domain to assess its suitability for ultra wideband communication. Pulse distortion of the antenna is investigated for both Rayleigh and Gaussian source pulse excitation.
A broadband dual-feed dual-polarized microstrip antenna with low cross polarization and high isolation is presented. The dual-orthogonal linearly polarized mode is excited by two different feed mechanisms from a single circular radiating patch. One of the two modes is excited by a pair of L-shaped probes with a 180° phase differences, and the other is excited by an H-shaped aperture. The proposed design has a very simple antenna structure with a wide input impedance bandwidth (23.25% for Port1 and 35% for Port2) and also its two input port isolation is found to be as low as -40 dB. Measured results of the fabricated antenna prototypes are also carried out to verify the simulation analysis.
An ultra-wideband (UWB) printed antenna fed by balanced microstrip is proposed. This antenna is in the structure of symmetrical dipoles, each of which consists of 3 semicircular metal patches. The antenna has been simulated by CST MICROWAVE STUDIO® software and tested. Both the simulation and experimental results indicate that the proposed antenna obtains an ultra-wide bandwidth of 2.8-16.3 GHz, when VSWR is less than 2. The experimental results of the directional diagrams indicate that the proposed antenna acquires a balance feed within the whole working band. The analysis of the surface current on the radiators indicates that the proposed antenna has a radiation mode of standing wave current in low frequency and traveling wave current in high frequency. The length of the antenna on polarization direction is 0.315 times of the maximum working wavelength, which shows that the antenna is well miniaturized.
The use of Artificial Magnetic Conductor (AMC) as a reflector in a printed antenna is known to improve the antenna's radiation characteristics. This work investigates the implementation of AMC as a reflector on a wideband planar monopole antenna. The investigation is confined to a basic square unit cell of AMC with four possible variations. The AMC structures are constructed with square cells which have either similar square cells or a Perfect Electric Conductor (PEC) as the back plane. These same structures are also fabricated with vias. The impedance bandwidth, gain and power pattern are simulated and measured over the measured -10 dB impedance bandwidth of 3 GHz to 10 GHz. The outcome of the investigation is that, for the antenna element and AMC structures considered in this study, a gain enhancement of up to 6 dB can be achieved with the AMC structures. In addition, introduction of vias is observed not to influence gain, though it improves cross-polarization levels by 3 dB to 5 dB for AMC constructed of squares backed by PEC.
In order to gain consistent focusing quality all over the imaging region for wide-beam wide-swath airborne synthetic aperture radar (SAR), higher motion compensation (MoCo) accuracy at the edge of the swath is needed. In this letter, an improved MoCo approach is proposed, and its performance is validated by using simulated data, as well as real data collected by a P-band SAR system.