This paper presents 2-way Power Divider (PD) for Ultra-Wideband (UWB) applications. The proposed power divider is realized using two cascaded sections of Wilkinson Power Divider (WPD) of equal characteristic impedances and unequal electrical lengths with inserted open stub to improve matching, isolation and to broaden the bandwidth. It is proved analytically using the ``Even Odd Mode'' analysis method and the ABCD matrix to obtain exact closed-form design equations. A detailed design methodology is introduced to facilitate the implementation without needing CAD optimization. To verify the proposed design methodology, a 2-way power divider is designed, fabricated on a Rogers RT/Duroid 5880 substrate and compared to other published 2-way microstrip power dividers. Measured data show good agreement with Electromagnetic (EM)-Circuit Co-Simulation, which proves the design equations and methodology. The proposed planar 2-way PD achieves an isolation ≥ 13.5 dB, input return loss ≥10 dB, output return loss ≥14.5 dB and exceeded insertion loss ≤ 0.9 dB (over the -3 dB splitting ratio) through the whole UWB range from 3.1 GHz to 10.6 GHz. Furthermore, it has a compact area of 22 mm × 15 mm, which provides 50% enhancement over similar microstrip PD circuits while achieving better isolation and matching.
In this paper, a single layer 4×4 U-slot patch antenna array based on differential feed was developed to achieve a wide bandwidth and low cross polarization with a simple feeding network. A U-slot was cut on a radiation patch to realize a wideband performance, and a microstrip-line fed structure was adopted to make the patch and feed network placed in a single layer. In order to reduce extra cross-polarization level in the H-plane caused by cutting U-slot, differential feed is adopted, which also makes it easily integrated with differential devices (such as differential amplifier) directly without baluns. A single layer U-slot patch array based on differential feed and an array having the same structure but based on normal feed were made and compared with each other. The designed differentially-fed patch array has more than 12% measured impedance bandwidth and stable gain at 18-19 dBi across the operating band from 5.2 to 5.88 GHz. The measured result shows that a better asymmetry of radiation pattern in the E-plane and a lower than -40 dB cross-polarization level in the H-plane can be achieved compared with normally-feed array.
Integral equation domain decomposition method (IE-DDM) with an efficient higher-order method for the analysis of electromagnetic scattering from arbitrary three-dimensional conducting objects in a half-space is conducted in this letter. The original objects are decomposed into several closed subdomains. Due to the flexibility of DDM, it allows different basis functions and fast solvers to be used in different subdomains based on the property of each subdomain. Here, the higher-order vector basis functions defined on curvilinear triangular patches are used in each subdomain with the flexibility of order selection, which significantly reduces the number of unknowns. Then a novel hybrid solver is introduced where the adaptive cross approximation (ACA) and the half-space multilevel fast multipole algorithm (HS-MLFMA) are integrated seamlessly in the framework of IE-DDM. The hybrid solver enhances the capability of IE-DDM and realizes efficient solution for objects above, below, or even straddling the interface of a half-space. Numerical results are presented to validate the efficiency and accuracy of this method.
This article describes the operational principle of the satellite-based Chinese Area Positioning System (CAPS) and proposes a monopole antenna for a large anchored buoy platform in harsh marine environment. The proposed antenna is highly omnidirectional with sufficiently wide half-power beamwidth (HPBW) greater than 40˚ (i.e., not less than ±20° swing) by using a conical ground plane, taking into account the geostationary satellite position, link budget, sea conditions, volume and cost. The impedance bandwidth defined by 10 dB return loss is 750 MHz (5.60-6.35 GHz), and the main lobe direction and the half-power beamwidth are about 46° and 43° at the operating frequency 5.885 GHz, respectively. The antenna prototype has been installed on-site to test its performance in sea. The results confirm that the proposed antenna is a suitable candidate for a variety of CAPS applications in China.
An effective design of a novel, compact, single feed, dual patch frequency reconfigurable Microstrip Patch Antenna (MPA) for wireless communication systems is proposed and studied in this paper. Fundamental structure of the antenna consists of a rectangular patch and a U-shaped patch. This antenna occupies a compact volume of 86.3 mm × 50 mm × 1.5875 mm (6850.6 mm3) including ground plane. Switching among four different frequencies is obtained by varying effective length of antenna. Effective length is changed by placing three PIN diodes at different positions in the slot present between two patches of the antenna. Variations in effective length perturb the surface current paths and hence change current density on the conducting patches. By changing states of PIN diodes, the proposed antenna could be switched to 1.87 GHz, 3.55 GHz, 3.67 GHz and 5.6 GHz frequencies. Antenna is simulated in High Frequency Structure Simulator (HFSS) Version 13.0, and a prototype of the simulated antenna with DC biasing circuit is fabricated on a flame retardant (FR-4) Epoxy substrate. The antenna is fed by an inset microstrip line which provides impedance matching. The prototype is tested for its performance analysis. A good agreement is obtained between measured and simulated results. Simulated and measured results show that the antenna provides return loss less than -10 dB assuring good match in absence of any matching network at all frequencies. Effect of changing the position of PIN diodes on resonance frequencies is also studied. The proposed antenna provides benefits such as multifunction operation and symmetry of radiation pattern upon switching between different frequencies.
In this study, new closed-form solutions are presented for deriving inductance and capacitance elements of the extended-composite right/left-handed transmission line (E-CRLH TL) unit cell from the cutoff frequencies of right-handed (RH) and left-handed (LH) bands. The characteristics of the E-CRLH TL are investigated. The dispersion diagram, Bloch impedance, S-parameters are analyzed by the TL, circuit theories and the Bloch-Floquet theorem. Lastly, the usefulness of our method has been shown in detail by designing the desired characteristics for various cases.
A novel low radar cross section (RCS) microstrip patch antenna array (1×4) (MSPAA) is reported in this paper. A thin and wideband radar absorber (RA) based on a single octagonal loop (SOL) resistive frequency selective surface (FSS) is designed for realizing out-of-band RCS reduction of the MSPAA from 6.2 GHz to 18 GHz. The RA is designed for -15 dB reflectivity from 6.2 GHz to 18 GHz. Embedded Passives (EP) resistors are used for implementing the resistors as integral to the substrate with no soldering at all which results in a quantum improvement in reliability. Full wave analysis of the low RCS MSPAA with the RA is carried out using HFSS. RCS measurements are performed, and an RCS reduction of 6 to 18 dB is attained compared to the reference antenna array over a wide band from 6 GHz to 18 GHz, with no degradation in VSWR and gain of the antenna array. The thin and wideband RA with its low weight and flight worthy constituent materials can be applied independently as skins of a stealthy UAV configured primarily for low RCS with external shaping, and the proposed antenna array can be used without modifications, as a low RCS conformal antenna structure.
A new design of non-planar magneto-electric monopole antenna is proposed and presented. This antenna consists of a novel design of electric monopole with dual Ί shaped feed line design and possesses 61.5% impedance bandwidth, from 4.5 GHz-8.5 GHz. The antenna exhibits stable omnidirectional radiation pattern with almost identical E-plane and H-plane radiation patterns and also provides a peak gain of 7.4 dBi. Due to its good electrical characteristics and radiation parameters, the antenna has great capability to operate in C band, to overcome the challenges of multi-frequency applications.
This work investigates on the performance improvements in terms of sidelobe reduction provided by arrays organized into randomly overlapped subarrays (ROSAs) in comparison to other subarray arrangements such as contiguous and uniformly-overlapped modules. This configuration can be advantageous for applications that need to scan over a limited angular sector. The performance of the ROSA design is thoroughly analyzed for different degrees of overlapping in terms of scan losses, minimization of peak side lobe level, number of components and array size.
In this paper, a CPW feed ultrawideband (UWB) slot antenna with a single reconfigurable notched band is proposed for overlay cognitive radio (CR) systems. The proposed antenna utilizes two symmetrical short circuited quarter wavelength resonators at the top layer and close to the ground to create a single notch. The switching reconfiguration is achieved by changing the length of resonators to prevent the interference to the primary users that are operating in the wireless local area network (WLAN) band at 5.725-5.825 GHz and the international telecommunication union (ITU) band at 8.05-8.4 GHz. The center frequency of the notched band can be tuned by selecting the length of the resonators, which is achieved by employing two ideal switches. Moreover, the proposed antenna has been fabricated and tested. The experimental data confirmed that the proposed design can selectively have a band notch over the two existent desired bands.
A novel high-gain directional lens antenna is numerically designed and experimentally tested in terahertz atmospheric transmission I window. The lens antenna consists of two components: a diagonal horn is adopted as the primary feed antenna, and a multilayer stacked lens consisting of the concentric hatch-crosses is used to focus the electromagnetic waves. The far-field characteristics of the horn antenna and the lens antenna are both studied. Furthermore, the effects of the number of periods of the lens and the focus diameter ratio on radiation characteristics are studied by using variable-controlling approach. The experimental results show that both the diagonal horn antenna and the lens antenna have axisymmetric radiation patterns. The gain of the horn antenna ranges from 23.8 dB to 24.9 dB, and the 3 dB main lobe beamwidth varies from 10.8° to 12.4°. The gain of the lens antenna is higher than 26.4 dB, and the 3 dB main lobe beamwidth is lower than 4.8° across the operation bandwidth. The good focusing characteristics and great directionality indicate that the designed lens antenna is qualified for applications in THz wireless communication systems.
This paper presents the design of a compact printed multi-band antenna for satellite communications within vehicular applications. The designed antenna is characterized by its compact size of 24mm18mm and multiple resonances over WiMAX, WLAN, 5 GHz U-NII, C-band, X-band, Ku-band, Kband and Ka-band. The performance of the multi-band antenna is investigated, and its equivalent circuit model is presented. Good performance is achieved over all the operating bands, with a relatively high gain and efficiency. Furthermore, as the interference with coexisting wireless systems can have a severe impact on the performance of the antenna, four variants of the antenna are proposed incorporating band rejection features within the antenna design. Embedded quarter-wavelength spur-lines, slots, and parasitic elements were used.
A circularly polarized substrate integrated waveguide (SIW) cavity-backed antenna with the feasibility of obtaining a wide bandwidth is proposed and demonstrated. Fed by a modified inverted-T stripline, the proposed double-layered stacked antenna, consisting of an improved circular SIW cavity and a conventional perturbed circular patch radiator, is designed, analyzed and fabricated. Good agreement between simulated and measured results is observed. Simulation and measurement results reveal that the proposed antenna can provide an impedance bandwidth of 22.1% (4.94-6.17 GHz) and a 3-dB axial ratio (AR) bandwidth of 18.7% (5-6.03 GHz). Additionally, within the effective circular polarization (CP) bandwidth of 18.7% (5-6.03 GHz), the proposed antenna has gains from 4.3 dBic to 7.1 dBic with an average gain of 5.9 dBic. The measured CP bandwidth of 18.7% (5-6.03 GHz) not only meets the need for certain Wi-Fi (5.2/5.8 GHz) or WiMAX (5.5 GHz) band communication application, but also provides the potential to implement multiservice transmission.
This paper proposes an ultrawideband (UWB) Vivaldi antenna with switchable and tunable band-notch characteristics. One stepped-impedance resonator (SIR), which has high quality factor Q and small size, is introduced to create band-notched characteristic with narrow notch band and high notch band edge selectivity. By loading two varactor diodes, a wide tunable notched band is achieved. The center frequency of notch band can tune from 3.1 GHz-6.8 GHz. In order to make the full use of UWB spectrum when there is on coexisting narrow-band applications, switchable band-notch characteristic is desired. Through rational parameters design, the center frequency of notched band is out of UWB range when the DC bias voltage of the varactor diode is 0 V. In this way, switchable band-notch characteristic is achieved.
In this paper, we discuss the impedance and radiation properties of planar UWB (any ultra wide frequency band) dual-polarized antennas. While their performance is usually defined using the impedance bandwidth, some applications require pattern stability over broad frequency bands. An analysis of the behaviour of three UWB dual-polarized antennas (Bowtie Antenna, Toothed Log-Periodic Antenna and Sinuous Antenna) showed interesting conclusions in terms of impedance matching bandwidth and radiation pattern steadiness. Starting from there, we then developed a method that consists in meandering the original structure. This method allows for miniaturization as well as radiation bandwidth enhancement. As a final result, an electrically small antenna with an impedance bandwidth of more than a decade and a steady radiation pattern over it has been developed.
Transformation of space coordinates is a tool to synthesize material properties in view of obtaining a controlled electromagnetic field pattern. Also, substrate-integrated waveguide (SIW) technology can well be exploited to develop microwave and millimeter-wave components. In this paper, by combining these features, high-gain SIW planar lens antennas are proposed. Using the embedded transformation-optics lenses, both narrow beamwidth of 12˚ and low sidelobe levels of -23 dB are achieved for the H-plane radiation patterns by a single antenna. The designed transformation-optics lenses can be realized by drilling spatially varying cylindrical holes in an ordinary dielectric substrate. The E-plane radiation patterns can also be improved through the dielectric slabs in front of the antenna aperture integrated in the same substrate. Therefore, using SIW technology, the lens antennas can be fabricated on a single substrate. An H-plane sectoral horn and a Maxwell-fisheye-based lens antenna are designed using the proposed method. Simulation results confirm the validity of the proposed idea and the advantages of these lens antennas.
This paper presents a systematic design process to design Bandstop Filters from Single-Band (SB-BSF) to Hexa-Band (HB-BSF). The presented BSFs are useful to suppressing the unwanted signal frequencies from 1.98 GHz to 7.75 GHz. Single-Band BSF suppress the frequency 1.98 GHz; Dual-Band BSF suppress 2 GHz and 3.4 GHz (WiMax Band); Triple-Band BSF suppress 2.0 GHz, 3.4 GHz, and 4.75 GHz; Quad-Band BSF suppress 2.0 GHz, 3.4 GHz, 4.75 GHz, and 6.4 GHz; Penta-Band suppress 2.0 GHz, 3.4 GHz, 4.0 GHz, 4.85 GHz, and 6.75 GHz; however Hexa-Band suppress 2.0 GHz, 3.4 GHz, 4.2 GHz, 4.75 GHz, 6.5 GHz, and 7.75 GHz. The attenuation level for the suppressed frequencies varies from 19 dB to 62 dB, and the quality factor varies from 17 to 384.5. The simulated and measured results are presented to validate the design process. Such compact BSFs could be useful in modern communication systems to stop the potential interference of the unwanted signal frequencies in WLAN and UWB bands.
A novel rectangle tree fractal antenna (RTFA) for ultra-wideband(UWB) application with dual band notch characteristics is proposed. The radiating path is the tree fractal structure which is formed by the superposition of a number of rectangular patches, and multi-frequency resonance characteristics are obtained by only increasing the tree fractal iterations. UWB operation(3.1-10.6GHz) is achieved by using defected ground structure(DGS) on the ground plane to improve the impedance characteristics between adjacent resonant frequencies. The dual notch bands characteristics are realized by three U-slot on the tree fractal path and effectively suppress the interferences of WiMAX and WLAN. The measurement and simulation results have an acceptable agreement, and indicate that the antenna is suitable for UWB applications.
In this paper, a simple approach for efficiency enhancement of a wireless power transfer system by using mu near zero (MNZ) type of metamaterial is proposed. A single slab containing one-sided periodic structures of 3×3 array of meander-line unit cell has been placed between transmitting and receiving coils in the wireless power transfer system. The presented metamaterial structure is less complex than other reported metamaterial structures in the area of wireless power transfer system. The simulation and measurement have been performed with and without metamaterial slab. Using metamaterial slab, the maximum efficiency has been obtained about 55.3%, i.e. an improvement of efficiency around 15.7% is obtained compared to a wireless power transfer system without metamaterials. Interestingly, the proposed wireless power transfer system shows a steady improvement of efficiency even if the distance between the transmitting and receiving coil is increased.
We discuss in this paper the stability of the time marching (TM) method. We identify one cause of instability in the method associated with the calculation of variables involved in the convolution operation. We provide a solution to this problem, preventing the appearance of unstable poles in the Z-domain. This solution is fundamentally different from other previously presented approaches in the sense that it is not based on filtering or predictive techniques. Instead, it consists of preprocessing the known variable in the convolution equations.
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