A novel wideband dual-polarized antenna is presented for 2G/3G/LTE base-station applications. The proposed antenna consists of two orthogonal modified bowtie dipoles, parasitic elements and a cavity. By using parasitic elements and compact cavity, the antenna achieves a wide impedance bandwidth about 77.3% (VSWR<1.5) for both ports. Both simulated and measured results show that the proposed antenna has a port isolation higher than 31 dB and high gain (>8.5 dBi) over the entire operating band. Moreover, good cross-polarization (>25 dB) performance and a front-to-back ratio better than 20 dB are also verified by measured results.
A novel 60 GHz end-fire antenna for point-to-multipoint applications is presented. The prototype of this antenna is a dipole structure with a wide beamwidth. Then, the radiators are tilted with the ground is also modified to improve its directive gain while maintaining wide signal coverage. The antenna has a compact size of 10 mm × 7 mm × 0.254 mm. Measured results show that the antenna has favorable properties of 3-dB beamwidth up to 150° at 60 GHz, S11 less than -10 dB and stable gain of 5.9 to 6.8 dBi over 57 to 64 GHz, where these characteristics denote it fitting for 60 GHz wireless communication systems.
The most general electromagnetic boundary, defined by linear and local boundary conditions, is defined in terms of conditions which can be called generalized impedance boundary conditions. Requiring that the boundary be equivalent to PEC and PMC boundaries for its two eigenplane waves, which property is known to exist for many of its special cases, it is shown that the recently introduced Generalized Soft-and-Hard/DB (GSHDB) boundary is the most general boundary satisfying this property.
A wideband circularly polarized (CP) slot array with high radiation efficiency is proposed. The cavity-backed square slots are designed to achieve wideband CP radiation with a unidirectional pattern. The slotted waveguide is adopted to feed the array with high efficiency. The square slot, cavity and feeding slot in the waveguide can be viewed as a radiating element. A CP slot array can be conveniently designed as traditional waveguide slot arrays, once the element admittance characteristic is determined. A 1-by-8 CP array operating at 12.5 GHz has been developed. Measured impedance bandwidth of 6.9%, axial-ratio (AR) bandwidth of 8.8% and a gain of 15.4 dBi have been achieved. This array can be conveniently expanded to a larger wideband CP array with a higher gain, which is preferred for the specific satellite communication applications.
This paper proposes sensors based on the time-domain reflectometry (TDR) technique for qualifying ethanol fuel. Four different probe geometries were proposed: bifilar, microstrip, coaxial, and helical. All probes allowed qualification of ethanol adulterated with water. Helical probe showed the best response. Thus, this proposal contributes to the development of electronic tongues.
A W-band dual-polarized Cassegrain antenna for cloud radar is proposed. The aperture diameter of the main reflector of the antenna is 50 cm. By using a modified Magic-T structure in the feed horn, the antenna is dual-polarized with high port isolation. The measured results show that the port isolation is 44.7 dB. The gains are 47.3 dB and 49.5 dB for the two ports at 94 GHz, respectively, and the efficiency of the antenna is better than 87%.
A method for extracting a desired network from the composite measurement of a desired and undesired networks combination is proposed. The desired network is required to be a reciprocal and passive network. Time-domain responses are chosen by time-domain gates according to the signal flow diagram of the measured networks. This method can be used to characterize fixtures and de-embed of fixtures effects from the composite measurement of a device under test (DUT) and fixtures combination. This method can also compensate for masking errors. Extraction for the S-parameters of the desired network are described in detail, and the extraction result is validated with two simulations.
ƒA novel compact circularly polarized microstrip antenna (CPMA) with bandwidth enhancement is proposed and studied. By employing capacitive loading and inductive loading, the size miniaturization is achieved. The cross-shaped aperture in the ground plane is able to excite two orthogonal modes. The near-equal amplitudes and 90° phase difference between these two modes are realized by properly designing the feed network, i.e., a 0°-90° hybrid comprising a 3-dB Wilkinson power divider cascaded with a 90° phase shifter. The proposed antenna exhibits a global bandwidth of 11.5% ranging from 1.88 GHz to 2.11 GHz with an overall size 50 mm × 50 mm × 6.8 mm (0.33λ0 × 0.33λ0 × 0.045λ0). The global bandwidth is defined where return loss is larger than 10 dB, broadside axial ratio (AR) smaller than 3 dB, and gain above 0 dBic.
In this paper, a coplanar waveguide (CPW)-fed dual-band slot antenna with circular polarization (CP) is presented. In order to achieve CP characteristic, an asymmetric slot and F-shaped end patch are introduced to a conventional rectangular slot antenna. Moreover, by cutting a T-shaped notch on the ground plane, the axial ratio (AR) bandwidth (ARBW) can be extended. The antenna shows left-hand CP (LHCP) radiation in the boresight direction (i.e. +Z direction) at both ARBWs. The proposed antenna is fabricated and measured. The measured results have a good agreement with the simulated ones. The measured impedance bandwidths (|S11| < -10 dB) are 1.08 GHz (2.02 to 3.10 GHz, 40% at 2.70 GHz) and 2.31 GHz (4.57 to 6.88 GHz, 39.8% at 5.8 GHz). The two measured ARBWs are 600 MHz (2.60 to 3.20 GHz, 22.2% at 2.70 GHz) and at least 1.15 GHz (4.85 to 6.0 GHz, 19.8% at 5.8 GHz) at the lower and upper bands, respectively.
Polarization converters based on metamaterial have broad application in imaging, sensing and communication from microwave to optical frequency. However, its performance is limited by single function and narrowband. In this paper, a new type of polarization converter based on square loop shaped metamaterial has been presented. It works in the reflection mode to achieve broadband polarization conversion for both circular and x/y linear polarization waves. The incident linearly polarized wave will be converted to its cross-polarized state with a polarization conversion ratio (PCR) lager than 0.9 in two distinct broad frequency ranges; on the other hand, circularly polarized wave will be reflected to its co-polarized state efficiently in the same spectrum regimes. Good agreements have been observed for both simulation and measurement results. This work offers a further step in developing high performance multi-function microwave or optical devices.
An unequal power divider which features quasi-arbitrary output phase difference is proposed in this paper. The circuit consists of four microstrip lines and a resister. By the even- and odd-mode analysis technique, the closed-form design equations of this structure are derived. The characteristic impedances, electrical length and bandwidth variations with power division ratio and phase difference are analyzed. For proving its validity, a prototype with this proposed structure is designed and implemented at 1 GHz. The results of simulation and measurement show that the pro-posed power divider can effectively produce two outputs with controllable power division and phase difference.
In this paper, a compact filtering power divider (PD) based on half mode substrate integrated waveguide (HMSIW) is presented. The proposed structure is realized by etching slots on the top layer of the HMSIW PD. Accordingly, two resonators are embedded in each patch, as a second order filter. The slots dimensions are obtained by the relationship between them and the extracted external quality factor and coupling coefficient. A good agreement between the simulated and measured results is reported. The measured 3 dB fractional bandwidth is 25% (6.3-8.1 GHz). The maximum insertion loss is 0.9 dB, and the return loss is above 20 dB in the passband. This design has the advantages of low insertion loss, improved out-of-band rejection, compact size, controllable bandwidth, and high selectivity.
A novel probe-fed single-layer circularly polarized (CP) truncated microstrip antenna with enhanced CP bandwidth and gain is presented in this paper. The axial ratio (AR) bandwidth is broadened by loading with a circle of truncated square parasitical patches. Parameter analysis is made to investigate the effect of the loading structures on the AR property. For comparisons, both the unloaded and loaded truncated patch antennas with the same size are designed, fabricated and measured. The measurement results show that by adding the parasitical patches, the -10 dB impedance bandwidth was increased from 0.98 GHz (15.9%) to 1.42 GHz (21.5%), among which the 3-dB RHCP AR bandwidth has been increased from 200 MHz (3.3% at the center frequency of 6.04 GHz) to 780 MHz (12.6% at the center frequency of 6.19 GHz). The gain enhancement is about 0.5 dB~1.5 dB around the operating frequency range, and the maximum gain of the proposed antenna is about 9.1 dB. With the advantages of simple structure, wide CP bandwidth and considerable gain property, this antenna has potential application in wireless communications.
This paper presents a compact shorted stub-loaded quad-band bandpass filter. The proposed filter simultaneously operates at GSM (0.83-0.97 GHz), LTE2300 (2300-2400 MHz), WiMAX (3.3-3.7 GHz), and WLAN (5.725-5.825 GHz) bands. The filter has been designed using the technique of stub-loaded resonator (SLR). By changing the length of the center-loaded stub, the resonant frequency of the even-mode can be varied without affecting that of the odd-mode. This simplifies the design and tuning of the quad-band filter. Eight transmission zeros (TZs) around the three passband make the pass bands highly isolated. In order to validate its practicability, a quad-band bandpass filter (BPF) has been designed, fabricated and measured. Good agreement between simulated and measured results is observed.
In this paper, a novel quad-band combination of circularly-polarized microstrip antenna is proposed. This antenna has multi-frequency and quad-polarization with multiple coaxial probes, which cover four bands of the BeiDou navigation system (BDS), meeting different application requirements. By using a stacked structure to achieve feed and using symmetrical slotted method to place the coaxial probes, the multi-frequency antenna is connected together through the middle co-aperture. Meanwhile, the feed position and size are constantly optimized until get the most suitable one, and the necessary perturbation is obtained. We also introduce a broadband stripline 90° bridge. Ultimately, the circularly-polarized and multi-frequency operation is achieved. Furthermore, the novel design enables easy implementation, miniaturization, wide band, which can meet the application requirements and promote the development of the BDS, which can be combined with the Internet of Things technology, applied to life and production.
A low-profile wideband bowtie antenna backed by artificial magnetic conductor (AMC) ground is presented for gain enhancement.The proposed bowtie antenna, loaded with an open stub in the upper layer, has broadband property. By using an AMC reflector,consisting of 6×9 metallic patches, the bidirectional radiation of the bowtie antenna is changed to unidirectional radiation. The distance between the bowtie antenna and the AMC surface is onlyλ/10 at 3.75 GHz. Both the bowtie antenna and the AMC surface are fabricated and measured. The measured results demonstrate good and stable performances, including maximum gain of 8.27 dBi, and flat gain response with variation of 0.6 dB in the wide impedance matching (S11 < -10 dB) band from 3.05 GHz to 4.35 GHz(35.1%). Furthermore, the maximum cross-polarization level is -17 dB for both E and H planes, and the measured front-to-back ratios are more than 18 dB.Good agreement between the simulated and measured results validates the proposed design approach.
In this paper, a combination of the Jerusalem cross (JC) as a fractal load and fractal Minkowski slot antenna for dual-band application is investigated. The prototype slot antenna has a Minkowski fractal formation with four Jerusalem cross (JC) loads to achieve dual-band application with compact size to improve the bandwidth. A T-shaped feed line is implemented in the final modeled antenna. The fabricated antenna has a bi-directional pattern with sufficient bandwidth at 2.4-3.1 GHz and 5.1-5.9 GHz with VSWR<2 for Wi-Fi, WiMAX, Bluetooth application as well as an IEEE WLAN protocol with a gain of 5-6 dBi, respectively. The size of the prototype patch antenna is 40×40 mm2, and the antenna is designed and fabricated on an FR-4 low cost substrate with εr=4.4 and thickness of 1.6 mm. It is simulated by HFSS full wave software. In addition, the VSWR, pattern and axial ratio of experimental results are presented and compared with simulation models. As a result, improvements of the Jerusalem cross compared with conventional cross have been achieved with some parameter tuning to improve the band width.
Orbital angular momentum (OAM) with a huge potential application in multiplexing and coding has become the subject of intense research in recent years. This paper presents a method to generate radio beams carrying OAM based on a circular patch antenna. A 3 dB quadrature hybrid is employed in the design to enable the circular patch to reconfigure opposite OAM states of a radiated field. The results of numerical simulations are presented to show that the circular patch radiates two OAM modes with opposite rotation directions simultaneously. The proposed circular patch is believed to be significant to the wireless communication applications due to its simple geometry, low cost, and OAM mode reconfiguration.
This paper presents the design and implementation of a novel fully planar modified, extended composite right/left-handed transmission lines (E-CRLH-TLs) utilizing a complementary split ring resonator (CSRR) loaded on the ground plane. The multiband behavior of the proposed layout is demonstrated by an equivalent circuit which in this case is distinct from the standard form of the equivalent circuits presented for an E-CTLH-TL; therefore, in order to design a quad band E-CRLH unit-cell, the design procedure is investigated. The main advantages of the proposed layout over other topologies are size reduction and fabrication simplicity which are proved by the design and fabrication of a quad-band Y power divider.
A dual band printed inverted-F antenna with a nested structure is proposed. In this antenna, matching can be controlled for both frequency bands by changing element lengths. The measured and calculated frequency characteristics of the antenna's reflection coefficient match very well, if the measurement cable connector is considered in the simulation. The measured -10 dB relative bandwidths of the reflection coefficient are 4.7% at 2.45 GHz (2.5 GHz to 2.62 GHz), and 9% at 5.5 GHz (5.28 GHz to 5.78 GHz). The calculated radiation efficiencies are 92% and 88%, at 2.45 GHz and 5.5 GHz, respectively, with calculated peak realized gains of 1.07 dBi and 3.36 dBi, respectively.
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