Based on convoluted interwoven element, a miniaturized frequency selective surface (FSS) with stable band-stop response is proposed in the paper. By extending the four dipoles into the adjacent elements, the equivalent inductance and capacitance are increased, and therefore the proposed FSS realizes promising miniaturization characteristics. The simulation results indicate that the resonant frequency is 1.19GHz, and the dimension is only 0.027λ0. Compared to traditional crossed elements, the size is reduced by 94.6%. Besides, the FSS has excellent angle-stability under both TE and TM waves. Finally, the proposed FSS is fabricated and measured, and the experiment results prove the satisfactory consistency with the simulation results.
In this paper, a compact ultra-wideband bandpass filter using a back to back Coplanar Waveguide (CPW)-to-microstrip transition structure is proposed. Compared with traditional ultra-wideband bandpass filters using hybrid structures, the proposed filter has a sharper selectivity because of two transmission zeros located at the lower and upper edges of the passband, respectively, generated by a modified T-shaped stub. Moreover, to further improve its out-of-band performance open stubs are introduced to produce extra transmission zeros at high frequency. A prototype of the proposed filter is fabricated and measured. The results show that the proposed filter achieves a bandwidth of 133% from 2.4 to 11.9 GHz, and the selectivity (skirt factor) is optimized from 50% to 92% compared to a former ultra-wideband (UWB) bandpass filter (BPF) with a similar structure. Besides, the proposed filter can offer some other advantages such as good return loss, low insertion loss, stable group delay, and compact size (16×7.55mm2). This filter can be a good candidate for UWB applications.
In this article, a compact ultra-wideband (UWB) band-pass filter (BPF) with wide upper stopband is presented. The filter is designed with a UWB response from 3.2 GHz to 10.8 GHz with low insertion loss of 0.9 dB and less than 0.19 dB at the center frequency (6.67 GHz). The filter is also designed with a broad upper stopband with high rejection level of 20 dB. The group delay is flat with maximum of 0.4 ns. The proposed UWB filter is constructed by using a pair of parallel coupled lines and two ring resonators. In this design, the ring resonators provide two new excited modes to widen the desired UWB passband and also create two tunable transmission zeros to achieve a wide stopband. Good agreement is observed between simulated and measured performances of the UWB filter.
A varactor-tuned microstrip bandpass filter (BPF) with independently tunable center frequency and bandwidth is proposed in this paper. The proposed BPF with a simple configuration is composed of a half-wavelength transmission line with both ends short-ended and a T-shaped transmission line. Meanwhile, two varactors are inserted symmetrically in the middle section of the half-wavelength transmission line to adjust the resonant frequency. The T-shaped transmission line is connected to the half-wavelength transmission line by a lumped capacitor. In addition, two inductors loaded symmetrically in the feed line are employed to control the coupling coefficient. It is convenient to adjust the frequency and bandwidth of the filter independently by using only three varactors, which simplifies the circuit structure greatly. The predicted results on S parameters are compared with the measured ones, and a reasonable agreement is achieved.
In this paper an ultra-wide bandwidth double-layered Vivaldi antenna (DLVA) integrated in Radome housing is proposed. First the conventional Vivaldi antenna is designed with bandwidth extended from 1.8 to 6 GHz at VSWR (3:1). Then for wider bandwidth, two slots are etched in the antenna ground plane to extend the antenna bandwidth from 1.7 to 9 GHz. For more improvement in antenna bandwidth, circular slots as electromagnetic band-gap structure (EBG) are etched to further extend the antenna bandwidth from 1.45 to 10 GHz. For gain enhancement double layers of Vivaldi antenna ground plane are designed with the same feeding line to reach 29 dBi peak. High frequency structure simulator (HFSS) ANSYS is used to design to simulated all the design steps. The proposed antenna is fabricated and measured. Finally, DLVA is integrated inside the Radome to improve the antenna gain and protect the proposed antenna from environmental factors. The antenna is fabricated and tested, and a good agreement between simulated and measured results is found.
A novel microstrip-to-CPW resonator is presented, which can be employed to design bandwidth-tunable bandpass filter. The tri-mode resonator is composed of a dual-mode microstrip resonator and a CPW stub printed on a single piece of substrate. Two varactors embedded in the resonator are utilized to adjust the frequencies of the first and third resonant modes independently, thus flexible bandwidth control can be achieved. For demonstration, a prototypical filter is implemented with fixed center frequency of 1.72 GHz and 9.3%-32.6% fractional bandwidth (FBW) tuning range. Good agreement is obtained between the simulated and experimental results.
The existing target localization algorithms almost cannot be used to near-field target localization in Multiple-Input Multiple-Output (MIMO) radar, and this paper presents a novel method. This algorithm uses Chan algorithm to obtain initial estimate of the targets. Then we define a new residual matrix and use the weighted least square (WLS) method to get a more accurate positioning result. The Fuzzy C-Means (FCM)algorithm is introduced to get more stable and accurate estimation. Furthermore, this algorithm achieves accurate positioning of the MIMO radar demonstrated by simulations.
A compact polarization diversity ultra-wideband (UWB) antenna with size 32×32 mm2 is presented in this paper. The proposed antenna consists of a linear tapered slot (LTS) ground, two orthogonal micro-strip feed lines and a floating fork-shaped decoupling structure located diagonally across the two orthogonal microstrip feed lines. The ground is in one side of the substrate, and the feed lines and the decoupling structure are in the other side. In addition, two rectangular slots are made in both the ground and feed lines to widen impedance bandwidth. Simulated and measured results indicate that the band covers from 3.1 to 12GHz with S11<-10dB and S12<-15dB.
A novel microstrip triplexer with a common crossed resonator and some uniform impedance resonators (UIR) is proposed in this paper. The crossed resonator is theoretically analyzed and proved to be able to resonate at three different frequencies. By using the crossed resonator as the common resonator, a compact structure can be gained as no extra matching network is needed, and the number of the resonator can be reduced effectively. Moreover, a wide stopband is obtained by setting the crossed resonator and UIRs working at the same fundamental frequencies but different higher order resonant frequencies. To demonstrate the design procedure, a triplexer with a third order Chebyshev response in each channel is fabricated and measured. The measured result is in good agreement with the simulated one, showing an attenuation of 20 dB up to 8 times the first channel frequency.
By attention to price of microwave components and need to use of them in many applications, the creation of an integrated component which can incorporate the performances of several components in one structure is a necessity. Therefore, in this paper a novel symmetric six-ports multi-functional microwave component is designed and realized. The proposed component consists of two modified half mode substrates integrated waveguide couplers which are joined and a slot which is attained from joined two mentioned couplers. Despite the slot prevents the exciting of higher order modes in proposed component, it divides signal in two parts by exciting middle SIW ports. By exciting each of the ports as input, the component can act as an equal and an unequal 90-degree couplers or power dividers. The proposed component with mentioned conditions covers 23.5% frequency bandwidth with maximum magnitude and phase error of ±0.7 dB and ±0.63 degree, respectively.
A novel substrate integrated waveguide (SIW) planar diplexer with very extremely high isolation is presented. It is formed by two quarter mode substrate integrated waveguide (QMSIW) cavity resonators which are designed individually and combined through a T-juction. The diplexer channels are 13% and 15% relative bandwidths at 2.35 GHz and 3.5 GHz, respectively. Inband return losses are better than 22 dB and 25 dB, and the insertion losses are 0.8 dB and 0.5 dB, in the lower and higher channels. The isolation between the two channels is lower than -42 dB, indicating enough isolation between the two channels. The measured results of the fabricated diplexer agree well with the simulated ones.
This paper presents a novel, Genetic Algorithm (GA) optimized X-band absorber using metamaterials. The unit cell of this structure consists of several square patches, each having a dimension of 2.5 mm x 2.5 mm. Their positions are optimized using the GA such that the X-band absorption is maximized. Simulation results and the subsequent experimental validation affirm that the structure offers absorption of 97% from 10.42 GHz to 11.98 GHz and absorption of 90% over the entire X-band from 8 GHz to 9 GHz and also from 9.35 GHz to 12 GHz, with peak absorption of 99.95% at 10.52 GHz. The results are compared with the existing ones, to demonstrate the superiority of the proposed design.
A filtering antenna based on a dumbbell-shaped resonator is proposed, fabricated and measured. A Γ-shaped antenna and the proposed dumbbell-shaped resonator are used and integrated to be a filtering antenna. The Γ-shaped antenna which acts as a radiator is excited by a coupled line. Measured results show that the filtering antenna achieves an impedance bandwidth of 6.7% at a reflection coefficient |S11| < -10dB and has a gain of 1.35 dBi. Moreover, a radiation zero occurs at 3.1GHz. Compared with the characteristics of fundamental Γ-shaped antenna, the design of the dumbbell resonator has little impact on antenna's radiation patterns. In addition, to explain the mechanism of filtering antenna, the analysis of surface current distribution on patch is given. The size of filtering antenna is 0.33λ0×0.17λ0 (λ0 is the free-space wavelength at 2.45 GHz). Compared to other recent works, a simpler structure and more compact size are the key features. Owing to the operating bandwidth and the characteristic of filtering, the proposed antenna can be used in modern wireless communications systems.
In this article, a novel design of butterfly-shaped compact and small size microstrip antenna is proposed. The radiating structure consists of four circular discs in coalesced form and fed with coaxial probe. The initial antenna resonates at 9.64 GHz with impedance bandwidth of 11.41%. The resonance frequency is further reduced to 8.12 GHz with bandwidth 10.10%, when a rectangular slot is incorporated in the initial patch. Finally, two parallel slots are embedded in the initial patch which improves the antenna bandwidth up to 21.50% (6.02-7.47 GHz). The gain and efficiency of this antenna are above 8.80 dBi and 90% respectively across the entire operating band. Radiation pattern is calculated at lower end (6.02 GHz), upper end (7.47 GHz) and centre frequency (6.75 GHz) of operating band. The proposed antenna is fabricated, and measured results are validated with the simulated ones.
A novel circularly polarised antenna with wide 3 dB axial-ratio beamwidth (ARBW) and half power beamwidth (HPBW) is proposed in this letter. By using two pairs of tilted dipoles, the ARBW of the antenna is significantly enhanced to about 160° and 162° in the XZ- and YZ-planes, respectively. Meanwhile, its HPBW is also broadened to above 116° in the dual planes. A prototype is manufactured and measured to validate the method. The measured results show that |S11|<-10 dB reaches about 38.8% (1.37 GHz-2.03 GHz), and the AR at broadside bandwidth is 14% (1.51 GHz-1.74 GHz). The gain of the antenna also keeps above 4.19 dBic. Meanwhile, acceptable agreements can be obtained between the simulated and measured results. As such, the proposed CP antenna with wide beamwidth can be used in various navigation systems.
In this paper, a novel planar monopole ultra-wideband (UWB) antenna with quad notched bands is investigated. The proposed antenna is composed of a circular-shaped radiating element, a 50 Ω microstrip feed line, a quad-mode stepped impedance resonator (SIR), and a partially truncated ground plane. By coupling a quad-mode SIR with an additional outer line beside the microstrip feedline, band-rejected filtering properties around C-band (5.2/5.8 GHz) WLAN bands, and X-band (8.5/10.5 GHz) satellite communication bands are generated. The measurement of voltage standing wave ratio (VSWR) is in agreement with simulation. The results show that the proposed antenna not only retains an ultrawide bandwidth but also owns quad band-rejections capability. The UWB antenna demonstrates omnidirectional radiation patterns across nearly the whole operating bandwidth that is suitable for UWB applications.
In this letter, a compact second-order mixed coupling bandpass filter (BPF) with one controllable transmission zero (TZ) near the passband edge is presented using multilayer substrate integrated waveguide (SIW). Two arranged circular SIW resonators can be vertically coupled via the circular apertures etched on the middle metal layer while preserving a compact physical size compared with the conventional horizontally coupled filter made of the single layer. The mixed electric and magnetic coupling can be introduced by two etched circular apertures. And one controllable TZ can be created in the lower stopband for the magnetic-dominant or in the upper stopband for the electric-dominant. To demonstrate the proposed design method, a multilayer SIW BPF for WLAN application has been designed and fabricated, and the measured results show good agreement with the simulated ones.
In this paper, a merged characteristic basis function method (MCBFM) is proposed to analyze the electromagnetic scattering characteristics from conducting targets. A merged characteristic basis function (M-CBF) is newly defined in the MCBFM. Considering the mutual interaction of surrounding blocks, the M-CBF is generated by merging the conventional secondary characteristic basis functions (SCBFs) and the high order characteristic basis functions (HO-CBFs) of each block in the conventional primary characteristic basis function (PCBF). Thus, the true current distribution of the targets is approached by using a single M-CBF reducing the number of CBFs when the incident plane waves (PWs) are certain. The numerical results of a PEC hexahedron demonstrate that the proposed MCBFM improves the accuracy without increasing the number of PWs and the CBFs compared to the improved primary CBFM (IP-CBFM). The results also demonstrate that the MCBFM is capable of effectively reducing the CPU time by 63.38% without losing any accuracy compared to the conventional characteristic basis function method (CBFM). Other results of a PEC cylinder demonstrate that when a considerable computational accuracy is required, the efficiency of the proposed MCBFM is the highest among these three methods.
The proposed filter satisfies the Federal Communications Commission ultra-wideband (FCC-UWB) specifications, and also creates and controls sharp rejection notch-bands within the filter's passband in order to provide interference immunity from unwanted radio signals, such as wireless local area networks (WLAN) and worldwide interoperability for microwave access (WIMAX) that cohabit within the UWB spectrum. This filter is based on CRLH concept consisting of an asymmetric transmission line unit cell with a short circuited inductive stub to realize high performance in an operation band from 3.1 to 10.6 GHz with a very compact size of 16.4mm × 5.0 mm. The main advantage of the proposed filter is that four notch frequencies are tuned in the UWB frequency band. The notch frequencies of the filter can be changed by increasing the length of the coupling stub which is controlled by using switching matrix equipment (Mini Circuit) instead of PIN diodes. To validate the design theory, a microstrip UWB BPF with four notch bands centered at frequencies 6.18, 5.9, 5.7, and 5.5GHz is designed and fabricated.
In this letter, a new coplanar waveguide (CPW)-fed monopole antenna with equilateral-triangular shape is presented and experimentally investigated. The structure under study generates three different center frequencies corresponding to the lower, middle, and upper bands for Wireless Local Area Networks (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed antenna is analyzed using the Computer Simulation Technology (CST) Software. To validate the simulation results, an experimental prototype of the proposed design is fabricated, tested and measured. The experimental results show a good agreement with the simulated ones.
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