A compact four-element multiple-input-and-multiple-output (MIMO) antenna system is proposed based on substrate-integrated-waveguide (SIW) cavities. By bisecting a square SIW cavity, two rectangle half-mode cavities with opened edges are formed. They are arranged side by side sharing a row of metallic vias. Then two narrow T-shaped slots are etched along symmetry planes to divide these two cavities into four quarter-mode sub-cavities. Excited by feeding ports, four antenna elements with compact size are constructed, which radiate incident wave through opened cavity edges and etched slots. Moreover, antenna isolation can be easily improved by adjusting slot length though these elements interconnect. A prototype with the cavity size of 0.22λ0 × 0.86λ0 has been fabricated. The fabricated MIMO antenna system exhibits the center frequency of 3.51 GHz, port isolation of 14 dB, envelope correlation coefficient of 0.03, peak gain of 4.9 dBi, and high efficiency of 77.4%. The compact size and effective isolation improvement make the proposed design attractive for practical applications.
Based on a novel right-angled triangle artificial line, a branch-line coupler is designed in this letter. The measured results indicate that the proposed branch-line operates at 0.975 GHz with a stopband bandwidth more than 15fc. Here, fc is the center frequency of the coupler. Importantly, the suppression levels in the stopband are better than 15 dB. Besides, its occupied size is about 23.18×22.5 mm2, which is only 16.5% of a traditional one at the same operating band. In practice, the proposed branch-line coupler can be used in compact systems which require good high-order harmonic suppression.
A new design of a printed Yagi-Uda antenna is presented. The main idea to be directive and large bandwidth is to replace the driver element associated with its reflector by a directional curved disk monopole, and the directors by flat disks monopole. It requires the use of a ground plane to simplify feeding. The study of configuration of the dimensions, the number and the dispositions of the directors elements allows a return loss less than -10 dB over 20% bandwidth centered at 5 GHz. Also, a high gain of 13 dBi is obtained with a maximum radiation direction at 26° elevation from the azimuth due to a limitation of the ground plane. This gain remains superior to 10 dBi over the bandwidth. The simulation results are in good agreement with the measurements for return losses, radiation patterns, and gain.
This paper presents the first coupled-line coupler that provides independent power division ratios at dual bands. In contrast with previous dual-band coupled-line couplers, the power division ratios k2(f2) and k2(f2) at each band (f1 and f2) can be independently controlled in order to satisfy the requirements of various communication protocols at different bands. Moreover, it has a compact size due to the usage of coupled lines rather than transmission lines. Explicit design equations and design guide of the coupler are provided. In this letter, one prototype of the proposed coupler is simulated, fabricated, and measured. It provides power division ratios k2(f1)=4 dB at f1=1 GHz and k2(f2)=8 dB at f2=2.4 GHz. The measured result agrees well with the simulation.
The goal of this paper is to design a dual band antenna for the integration of LTE-R 700-MHz band along with 5G (3.5 GHz) band applications for future advanced railway communication. A design study of the dual band antenna is proposed and discussed in detail. An ellipse-shaped ring patch is designed for the LTR-R 700-MHz band, and the 5G (3.5 GHz) band is added by keeping the circular patch in proximity to the feed line of the antenna to make it a stacked antenna configuration. Circular patches with varying dimensions are used to increase the bandwidth at 3.5-GHz band. The antenna has a size of 180 mm x 60 mm and is fabricated on an FR4 substrate with dielectric constant 4.4 (tanδ = 0.025). The observed bandwidth is approximately 100 MHz and 500 MHz for each frequency band respectively.
Graphite receives tremendous attentions as filler for conducting composite due to its low cost and high electrical conductivities. In this work we use polyvinylidene fluoride (PVDF) as insulating matrix and graphite (Gr) as a filler to develop conducting composite films using solvent casting technique. The dielectric properties of the developed PVDF-Gr films were analysed for the frequency range of 100 kHz to 10 MHz. The morphology of the obtained films was investigated by scanning electron microscopy. The EMI shielding properties of the PVDF-Gr composite films were evaluated theoretically using ɛ′, tan δ, and σ in the desired radio frequency region. Mechanical strength of the films was tested by universal testing machine. Due to advantages such as light weight, flexibility, and low cost the developed film with the thickness of ~0.15 mm had very good potential to be used for fabricating electromagnetic compatible electronic devices.
In this paper, a center-fed substrate integrated waveguide (SIW) inclined slot array antenna is designed for a one-dimensional active phased array. A novel coaxial-to-SIW transition is employed to realize the central feed for enhancing bandwidth. The antenna prototype printed onto a single-layer Rogers 5870 is composed of 32×16 inclined slots working at Ku-band. As shown in measured result, the bandwidth with return loss < -10 dB is from 16.6 to 17.1 GHz, and the sidelobe levels of arrays are below -24.8 dB at 16.8 GHz in H planes. The measured gain is 31.8 dB at 16.8 GHz with the aperture efficiency of 65%. The active phased array is assembled by an antenna and 32 Tx/Rx modules, and the measured results show that the main lobe can obtain a wide-angle scanning from -45 to 45 degrees in E planes. The antenna array is suitable for low profile small active phased array radars and communication systems that require spatial wide-angle scanning.
An optimized dual-bandnotched antenna for Ultra-Wide Bandapplications, using the Genetic Algorithm (GA), is presented. By optimizing a Defected Ground Structure (DGS) in the ground plane of the UWB antenna, two notches are created at the desired frequency bands of 3.5 GHz and 5.8 GHz, respectively. A good agreement between the measurement and simulation results is observed. The optimized DGS shows good performance and accuracy compared to conventional approaches.
A new approach to design a microstrip ultra-wideband (UWB) bandpass filter (BPF) with quad sharply notched bands and good selectivity is proposed using quad parallel defected microstrip structures (PDMSs). The initial UWB BPF comprises interdigital coupled lines and an E-shaped multiple-mode resonator (EMMR) to achieve two transmission zeros on both sides of the passband thus to improve skirt selectivity. Then, four PDMSs are introduced, which have the properties of achieving four band-notched characteristics and provide high degree of adjusting freedom. To validate the design theory, a new microstrip UWB BPF with four notched bands respectively centered at 5.3, 5.9, 6.4, and 7.4 GHz is designed and fabricated. Both simulation and experimental results are provided with good agreement. The designed methodology is very efficient and useful for filter synthesis though the design principle is simple.
The extending applications for mobile computing have experienced immense progress over the previous decade. However, this has ultimately influenced the shortage of bandwidth. Therefore, to fulfill the consumers' demand, inexpensive antennas need to be uniquely designed for the next/fifth generation (5G) frequency spectrum. Consequently, this paper presents a novel antenna composed of inductors (L) or capacitors (C) on an air-substrate. Zinc (Zn) and copper (Cu) materials are utilized to fabricate the lumped LC resonator prototype. The effects of antenna's and substrate's thickness on resonant frequency or bandwidth have been studied. The finalized configuration engaged 1113 sq. mm area and operated at 28 GHz with approximately 3 GHz bandwidth. At resonant frequency, the system demonstrates peak gain and efficiency values of 10.6 dBi and 91%, respectively. The core objective of this paper is to report an antenna featuring simple and economical design along with premium results for 5G mobile terminals.
This paper investigates the joint direction of departure (DOD) and the direction of arrival (DOA) estimation of coherent targets in bistatic multiple-input multiple-output (MIMO) radar under the presence of spatially correlated noise. Based on electromagnetic vector sensors at both transmitter and receiver of MIMO radar, a preprocessing method, namely polarization difference smoothing, is proposed to remove the coherence between targets and to suppress the spatially correlated noise. Then DOD and DOA are estimated using the ESPRIT method. Further, this paper develops a simple approach for pair-matching between the estimated DODs and DOAs. Simulation results are compared with the receive polarization smoothing and transmit-receive polarization smoothing methods available in literature. Results show that the proposed approach improves the performance significantly.
We propose a new method to match diplexer channels with a common port in which a π-shaped strip conductor is used as a matching circuit. The applicability of the method is illustrated by simulating and fabricating a microstrip diplexer for GPS/GLONASS applications. The central frequencies of the channels are 1.234 GHz and 1.597 GHz, and their fractional bandwidths are 6.8% and 7.3%, respectively; minimum insertion losses are 1.05 dB and 1.08 dB. The main advantage of the diplexer is its compact size: 16.8 mm × 11.0 mm × 6.4 mm in housing. Using 1D models and a quasi-TEM approach, the frequency-dependent coupling coefficients between the matching circuit and input resonators of the channels are calculated, and the influence of the matching circuit's geometrical parameters on its coupling with diplexer channels is studied.
The scattering of a transverse magnetic plane wave by a conducting cylinder partially buried in a dielectric half-space is solved by an aperture method. A system of coupled integral equations for the current induced on the cylinder and the scattered electric field at the dielectric interface are formulated from field equivalence principles. The scattered tangential electric field at interface is negligible at some distance from the cylinder location. Hence, for a sufficiently wide interface truncation, the coupled integral equations can be easily solved numerically by the Method of Moments. Data for the cylinder current, the scattered electric field at interface and the far-zone field are shown for cases of interest.
A novel dual-frequency antenna with horizontally polarized (HP) omnidirectional radiation is presented in this paper. The antenna consists of four printed arched dipoles, four planar baluns and a four-way power splitter. The balun as well as the power splitter works as the feed network. By loading a transmission line resonator (TLR) as the near-field coupling parasitic element, the dual-frequency characteristics can be realized. After the design principle is stated, a sample antenna is manufactured and measured to prove the predicted performance of the proposed antenna. The measured results agree well with the predicted ones.
An approach to synthesizing wideband ultraminiaturised-element frequency selective surface (UMEFSS) based on interlocked 2.5-dimensional (2.5D) structures is proposed. Ultra-miniaturisation and wide stopband response can be realized due to compactly staggered arrangement of 2.5D elements. The element size of the proposed UMEFSS is reduced to 0.033λ0×0.033λ0, and fractional bandwidth attains 99.8%. Stable response is achieved under oblique incidence at different polarisations. The results show a satisfactory consistency between full-wave simulations and experiments.
A compact circularly polarized microstrip ring antenna is presented for Global Navigation Satellite systems (GNSS) application in this paper. The antenna consists of a ring-shaped slotted ground and a radiation patch which is fed by a T-like coupling feedline. The radiation patch is a square ring strip embedded within two inverted L-shaped strips and a rectangular strip. The overall size of the proposed antenna is 0.38×0.38×0.038λg3 (λg is the guide wavelength at the frequency of 1575 MHz). The measured -15 dB |S11| bandwidth, 3 dB axial ratio (AR) bandwidth, and gain bandwidth of larger than 5 dBi are in the frequency range of 1552-1623 MHz, which can fully cover the operating frequency band of BDS B1, GPS L1, and GLONASS L1.
In order to obtain the carrier frequency (CF) and direction-of-arrival (DOA) estimation, a uniform linear array (ULA)-based modulated wideband converter (MWC) discrete compressed sampling (CS) digital receiver system is proposed. It can achieve sub-Nyquist sampling, save the storage space and specially obtain the CF and DOA estimation by processing the CS data directly. However, the existing method for this system needs more branches to get better performance. In this paper, a compressed uniform linear array (CULA)-based MWC discrete CS digital receiver system is proposed. First, a compression matrix is used to reduce the number of branches behind the antennas. Then, the MWC discrete CS structure is used to reduce the data volume. Finally, the multiple signal classification (MUSIC) algorithm is used to jointly estimate the CF and DOA by processing the CS data directly. The simulation results validate the effectiveness of the proposed system and the proposed method for the joint CF and DOA estimation.
A wideband low-profile dual-polarized antenna based on the use of an artificial magnetic conductor (AMC) reflector is proposed. The AMC reflector consists of 9×9 square patches. In order to obtain wide impedance and gain bandwidths, the antenna consists of four printed dipoles: two dipoles are used as a radiator of horizontal polarization, and two dipoles are used as a radiator of vertical polarization. A simple excitation scheme without balun is used for dipoles feeding. A low profile of 0.068λL is realized (λL is the wavelength at the lowest operating frequency). Simulation and measurement results show that the proposed antenna has a 40% impedance bandwidth, a 40% 3-dB gain bandwidth, and a port isolation of less than -30 dB.
This article proposes an advanced methodology to deal with the complexity of composite materials modeling up to 60 GHz. For radiofrequency (RF) requirements, it has been demonstrated that the distribution of conductive inclusions plays a major role. Since their locations are intrinsically subject to uncertain assumptions, the Monte Carlo (MC) technique is considered as a golden standard. Unfortunately, the computational costs involved by coupling full-wave electromagnetic (EM) simulations and MC remains prohibitive. The aim of this proposal is to demonstrate the interest of stochastic reduced order method (SROM) to tackle computational constraints, jointly with the statistical precision needed for a realistic description of RF composites.
This paper presents the design of a 3.8 ~ 8.0 GHz wide-band quadrature coupler on a multi-layer package substrate. The asymmetric coupled-line 3-dB quadrature coupler has been designed on a four-layer microwave substrate, with a 10-mil thick top layer of Roger's RO4350B substrate press-joined to a 20-mil thick bottom layer of RO4350B, through 4-mil thick bond-ply material RO4450B. In the proposed design, the second and third metal layers are used as coupling layers, while the fourth (bottom) layer provides four signal pads and one large ground pad for connection with the test circuit. The mutual coupling is achieved through the overlay of coupled lines. Four VIA holes are used for signal transition from coupling layers to the bottom-layer pads. The SMD package quadrature coupler provides the ease of integration with other microwave circuits. The quadrature coupler chip size is 4.0 mm x 8.0 mm x 0.9 mm. The measurement results show a close resemblance to the EM-simulation results. The measured results depict reasonably flat 3-dB coupling and quadrature phase difference. The amplitude imbalance remains within 1.0 dB, while the phase imbalance always remains much less than 3.0 degrees. The return loss and isolation are better than 13 dB, throughout the whole frequency band. The proposed design is quick and simple. The manufacturing process is also cost-effective. To the best of the author's knowledge, these measured performance parameters in 71% fractional bandwidth associated with the compact size of the self-packaged device are better than those of the earlier published 4-layer design schemes of wideband quadrature couplers.