This letter presents an omnidirectional printed dipole antenna array with a wide bandwidth. The array is composed of four dipole units etched on a thin substrate, which is simple in structure and easy to be processed. By modifying the triangle-shaped radiation dipole units and gradually increasing the width of microstrip feeding transmission line, the performance of the dipole antenna array is greatly improved. Simulation results show that this omnidirectional antenna has a peak gain greater than 7.39 dBi, and the impedance bandwidth is 16% (VSWR<1.6), ranging from 2.3 to 2.7 GHz.
In this paper, design of a profiled conical horn using piecewise biarc hermite polynomial interpolation is proposed. In order to improve the performance of the horn, a novel concept of `targeting the Region of Interest (RoI)' is used. The target specifications are decided based on the applicability of the horn in a reflectometry system for plasma diagnostics (D-band). Apart from the design details, the simulated results of the proposed horn are covered.
A balanced-to-balanced (BTB) bandpass filter (BPF) with an ultra-wide upper stopband is proposed in this letter. The proposed BPF is fed by balanced stepped-impedance microstrip-to-slotline transition structures. Good differential-mode (DM) transmission and common-mode (CM) suppression can be achieved intrinsically. To achieve good quality in DM passband and out-of-band suppression, a pair of dual-mode resonators has been designed and adopted. Meanwhile, the proposed balanced BPF exhibits an ultra-wide upper stopband of 162.7%. In order to verify the feasibility of the design method, a balanced BPF with a centre frequency of 1.57 GHz has been fabricated and measured. Measured results indicate that the designed filter achieves an out-of-band rejection better than 15 dB from 1.85 to 18 GHz, and the insertion loss (IL) inside the passband less than 1.4 dB. A good agreement between the simulation and measurement results demonstrates the validity of the design.
Leaky-wave radiations are usually generated by leaking the electromagnetic energy gradually over a structure. By using the coupling effect and leaky-wave properties, this paper designs a novel 1-D frequency scanning antenna array. The antenna is intended for the direct imaging radar sensors. The simulated results show that the scanning angle can stay in the range from -60˚ to 30˚. The proposed 1-D antenna array was manufactured, and the measured results are consistent with the simulated ones.
Phonon-polariton is the coupled excitation between optical phonon and photon. The remarkable frequency vs. wavevector dispersion relation of phonon-polariton contributes to important technological applications such as tunable terahertz radiation sources and basic materials science to clarify the terahertz dynamics of condensed matter such as lattice instability in ferroelectrics. This paper studies the broadband dispersion relation of phonon-polariton between 10 cm-1 and 1200 cm-1 in uniaxial ferroeletric crystals, LiNbO3 (LN) and LiTaO3 (LT) with polar trigonal system on the basis of the observed results using THz-Raman spectroscopy, THz time domain spectroscopy, and far-infrared spectroscopy. The dispersion on the lowest-frequency TO mode with A1(z) symmetry of LN and LT crystals, which are assigned as ferroelectric soft modes, is discussed.
A high-order (HO) finite-difference time-domain (FDTD) method with exponential time differencing (ETD) algorithm is proposed to model electromagnetic wave propagation in Debye dispersive material in this paper. The proposed method introduces an auxiliary difference equation (ADE) technique which establishes the relationship between the electric displacement vector and electric field intensity with a differential equation in Debye dispersive media. The ETD algorithm is applied to the displacement vector and auxiliary difference variable in time domain, and the fourth-order central-difference discretization is used in space domain. One example with plane wave propagation in a Debye dispersive media is calculated. Compared with the conventional ETD-FDTD method, the results from our proposed method show its accuracy and efficiency for Debye dispersive media simulation.
A method is proposed for a half-mode substrate integrated waveguide (HMSIW) bandpass filter (BPF) to obtain dual-band below the cutoff frequency. Complementary split-ring resonators (CSRRs) and microstrip open-stubs are integrated on the top of an HMSIW cavity. The structure produces two center frequencies both below the cutoff frequency of the originalHMSIW without increasing the cavity size. Results indicate that the center frequencies are 2.95 GHz and 3.99 GHz, and 3 dBfractional bandwidths (FBWs) are 9.1% and 4.6%, respectively. There is a transmission zero between the two frequencies, which enhances the out-of-band suppression performance. The measured results are in good agreement with the simulated ones. This new combination not only obtains two usable passbands below the cutoff frequency, but also makes the filter more compact. The filter has some practical and application significance.
A circularly polarized (CP) antenna with simple feeding network for ultra-high-frequency (UHF) radio-frequency identification (RFID) reader application is presented in this letter. The proposed antenna consists of a slot loop etched on the ground and a simple feeding network using bended microstrip lines. And the two parts of the antenna are printed on either sides of a thin substrate, thus a low-profile antenna is obtained. The slot loop is meandered based on the first-order Minkowski fractal technique for antenna size reduction. To generate circularly polarized radiation, two branches of the feeding network are designed to be orthorhombic with 90° phase difference. The antenna is simulated and practically fabricated with a compact size of 80×80×1.6 mm3. The 10-dB impedance bandwidth and 3-dB axial-ratio (AR) bandwidth are measured to be 50 MHz (0.896-0.946 GHz) and 12 MHz (0.916-0.928 GHz), respectively. The measured peak gain exhibits stable value of 3 dBi over the impedance bandwidth. Furthermore, a wide 3-dB beamwidth of 120° is achieved for the proposed antenna. Based on the above, this antenna is well suited for applications in UHF RFID handheld readers.
This paper presents the design and fabrication of an antenna based on Substrate Integrated Waveguide (SIW) for intersatellite crosslinks in C-band. The entire antenna consists of two elements of SIW slots array that is fed by a hybrid 3 dB directional coupler. The entire SIW slot array antenna is circularly polarized (CP), and each element has four longitudinal slots. The element's effective field matching is realized with a microstrip to SIW transition. The antenna design has been evaluated with its return loss, gain plot, and radiation pattern characteristics to validate the fabricated antenna. The fabricated prototype antenna radiates a left-handed circularly polarized (LHCP) electromagnetic wave with the peak gain of 5 dB and offers approximately 2% AR bandwidth around 5 GHz.
In this study, a varactor-loaded slotted ground structure is investigated and utilized to construct a new tunable common-mode (CM) suppression filter for differential signals. A four-port distributed equivalent circuit model is developed for interpreting the working mechanism of CM signal suppression. It is found that the proposed simple structure is capable of tunable CM suppression with a wide frequency tuning range. The parameter selection and design principle are also given. Finally, the design theory is well vindicated by a common-mode filter using three periodic varactorloaded slots. Simulated and measured results, showing good agreement, exhibit a tuning range from 0.80 to 2.10 GHz, corresponding to the fractional tuning range of 89.7% and more than 30 dB CM rejection level.
This paper presents a narrow-band bandpass filter (NBBPF) using three cylindrical dielectric resonators (CDRs) placed on three rectangular metallic cavities (RMCs). Two U-shaped planar resonators located between RMCs are used to realize narrow-band response effectively. The 3 dB fractional bandwidth (FBW) of the proposed filter is 0.275%. The filter is designed for X-band (9.85 GHz), with 20 MHz bandwidth for radar, satellite, and medical accelerators applications. High Q-factor (Q-factor = 400) and low fabrication cost are other advantages of the proposed design. The proposed NBBPF was fabricated, and its performance was measured to verify the design. Good agreement between the measured and simulated data is obtained.
This letter presents a broadband circularly polarized (CP) crossed dipole antenna with wide axial ratio (AR) beamwidth. The antenna consists of a crossed dipole fed by two baluns, a wideband feed network and a cylindrical metallic cavity. To broaden the beamwidth, circular arms are introduced. Meanwhile, the metallic cavity is utilized to broaden the AR beamwidth. Measurements show that the antenna has an impedance bandwidth of 70.6% (1.87-3.91 GHz) for voltage standing wave ratio (VSWR) ≤ 2 and a 3-dB AR bandwidth of 62.4% (1.92-3.66 GHz). In addition, the 3-dB AR beamwidth of the antenna is larger than 100°, and the gain varies from 4 dBic to 6 dBic over the whole CP operation bandwidth. Owing to the high-gain and wideband operation, the proposed CP antenna is potentially capable for satellite applications and high-gain applications.
A modified Gysel power divider with arbitrary power dividing ratio is proposed in this letter. The power dividing ratio of the proposed circuit is determined by both the electrical lengths and characteristic impedances of transmission lines. The proposed circuit is analyzed based on transmission line theory, and design equations are derived. For verification, two prototypes operating at 2 GHz with power dividing ratios of 1:1 and 4:1 are designed, fabricated and measured, respectively. The measured results are in good agreements with the simulated ones.
In this article, a couple of monopole line-fed UWB antennas with different configurations are presented. Antenna shapes include a big circle overlapped with four small circles, and a two overlapped circles in the horizontal direction. Configurations include single element antenna, single element antenna with dual band reject filters, and polarization diversity antenna version. Measurements show that all antennas work well within almost the whole UWB. The polarization diversity version has a practical port isolation (S12 and S21) better than -15 dB, an Envelope Correlation Coefficient lower than 0.019 and a diversity gain higher than 9.96 dB.
An ultra compact microstrip wideband bandpass filter (BPF) using a quadmode stub-loaded resonator is presented in this letter. The resonant characteristics of the quadmode resonator are explored by adopting odd- and even-mode analysis. The four resonant frequencies of this resonator can be controlled independently. For demonstration purpose, a wideband BPF is designed, fabricated and measured. The measured results are in good agreement with the full-wave simulation results. The realized wideband filter exhibits a 3 dB fractional bandwidth (FBW) of 45% with good in-band filtering performance and sharp out-of-band rejection skirt.
European smart energy meter applications operate over a smart grid network. These applications operate over ISM frequency bands. The proposed dual-band printed monopole antenna provides a solution to smart energy meter applications. The surface dimension of the planar monopole antenna is 45 x 17 mm2. The antenna has strips fabricated on a standard cost-effective FR-4 substrate of thickness 1.6 mm for achieving dual-mode resonance at 868 MHz and 2.4 GHz. The proposed monopole antenna has operating impedance bandwidth of 2.89% and 2.78% for the first and second resonances, respectively. The gain of the presented antenna is in order of 1.18 dBi for lower resonant mode and 2.1 dBi for the higher resonant mode. The antenna resonates in the frequency range which is also useful in smart RFID tags for device identification operating over smart grid. In addition, the antenna can be utilized for the devices functional in Low Rate Wireless Personal Area Networks (LR-WPAN) and WiFi-based smart applications.
Earlier, we considered the use of the apparatus of fractional derivatives to solve the two-dimensional problem of diffraction of a plane wave on an impedance strip. We introduced the concept of a ``fractional strip''. A ``fractional strip'' is understood as a strip on the surface, which is subject to fractional boundary conditions (FBC). The problem under consideration on the basis of various methods has been studied quite well. As a rule, this problem is studied on the basis of numerical methods. The proposed approach, as will be shown below, makes it possible to obtain an analytical solution of the problem for values of fractional order v = 0.5 and for fractional values of the interval v∈[0,1], the general solution needs to be investigated numerically.
A compact wideband bandpass filter (BPF) based on half-mode substrate integrated waveguide (HMSIW) is proposed in this paper. The proposed BPF is achieved by etching a couple of S-shaped complementary spiral resonators (S-CSRs) on the top layer of HMSIW cavity to achieve a wide passband as well as generate two transmission zeros in the vicinity of the passband respectively to improve the selectivity. In addition, compared with a conventional CSRs-loaded HMSIW structure, the proposed S-CSRs-loaded HMSIW makes the overall size of the filter largely reduced with the same electrical length. Among the HMSIW structures ever reported, the proposed S-CSRs are the first time to be introduced into HMSIW. To validate its practicability, a compact wideband HMSIW BPF loaded with S-SCRs has been designed and implemented through the PCB process. The measured and simulated S-parameters of the filter are presented to show the proposed filter's predicted performance, and good agreements is obtained between them. This result demonstrates that the newly proposed HMSIW structure loaded with S-CSRs is an excellent candidate for compact filters.
A simplified design of substrate integrated waveguide (SIW) is proposed here. The requirement of side walls using via which is quite cumbersome in the manufacturing process is eliminated in this structure. The design is based on producing an imaginary electric boundary by exciting the SIW using differential feed. It behaves as a pair of half mode substrate integrated waveguides (HMSIWs) sharing a common electric boundary. The new structure gives similar characteristics of the conventional SIW in terms of cutoff frequency, stopband rejection and operating bandwidth.
When a narrow straight slot is etched obliquely in the upper metallic strip of a microstrip line, a bandstop response can be observed from the terminations of the microstrip line. The whole circuit behaves as a single-stage bandstop filter, of which the center operation frequency and the fractional bandwidth can be adjusted by changing the length and the inclined angle of the slot, almost independently. Parametric studies are made to demonstrate the filtering performance, via numerical simulations. An LC equivalent circuit model is given to explain the bandstop behavior, shows its potential use in high order filter design. Samples are designed, fabricated and measured for verification, the experiment results show that the filters have good bandstop performance. It can be used as an alternative or complementary candidate for the traditional spur-line bandstop filter.