This paper describes a printed wideband low profile omnidirectional dual-polarized antenna, which is a combination of vertical polarization (VP) and horizontal polarization (HP) elements. The VP element printed on a double-layered disk-shaped substrate is a modified monopole with loadings. The introduction of the material of the dielectric substrate can reduce the profile height in the polarized direction to 0.08λL (the wavelength at the lowest frequency). And loading metallic cylindrical block and shorting-posts in the dielectric substrate to improve the bandwidth are realized by using metal-vias. The HP element consists of a printed 8-element circular connected Vivaldi antenna array, and each element contains a director in the slot for the improvement of radiation pattern's out-of-roundness. Both the simulated and measured results indicate that operating bands of 2.2-4.52 GHz for VP and 2.4-3.8 GHz for HP. This proposed antenna has good isolation and omnidirectional patterns with the out-of-roundness less than 2.5 dB in the azimuth plane for both VP and HP, and it can be applied in mobile communication systems.
This paper proposes an unequal power divider with different terminated impedances and different electrical lengths for four uniform transmission lines. The proposed power divider consists of four transmission lines with different electrical lengths and an isolation resistor. Under different port impedances, the splitting ratio of the proposed divider can be adjusted to desired values by varying the electrical lengths of the divider transmission lines with uniform impedances. To verify the feasibility of the proposed divider, two circuits were designed with dividing ratios of 2:1 and 4:1 at an operating frequency of 2 GHz. The circuits used a uniform impedance of 40 Ω at terminated impedances of 50, 70, and 60 Ω. The performance showed excellent agreement between the simulated and experimental results.
A fifth-order bandpass filter with high selectivity and wide-stopband by using quarter- and half-wavelength uniform impedance resonators (UIRs) is presented in this letter. The use of a terminated coupled line provides controllable transmission zeros that can suppress the parasitic passbands. A pair of transmission zeros is generated on both sides of the passband by introducing cross-coupling. As a result, high selectivity and wide stopband can be achieved simultaneously. The method of controlling transmission zeros using a coupled line and an open/short-circuited stub is analyzed, and the method of improving passband selectivity using cross-coupling is given in detais. The concept is experimentally tested in a microstrip bandpass filter with center frequency 1 GHz. The measured attenuation is better than 24 dB up to 18 GHz.
This paper proposes a new compact quad-channel diplexer (2.45/4.2 GHz and 3.5/5.2 GHz) using defected stepped impedance resonators (DSIRs). The proposed quad-channel diplexer is composed of one common input feeding line, sixteen folded DSIRs, and two output feeding lines. Every four DSIRs are designed to determine passband characteristics of one individual channel, and two passbands are filtered out eventually at each output port. The distributed coupling technique featured by small loading effect is introduced to eliminate the necessity of extra impedance matching networks, which consequently results in a reduced circuit size. A diplexer prototype operated at 2.45/4.2 GHz and 3.5/5.2 GHz bands with measured 3-dB fractional bandwidths of 12.5%, 7.2%, 6.4%, and 5.0% has been implemented, showing a high isolation of larger than 33 dB between the two output ports. Experimental results coincide well with the theoretical predictions and simulation results.
A hybrid Minkowskized fractal-like antenna structure for wireless application is presented in this paper. The Minkowskized radiating structure and feed line have been designed at the top layer of FR-4 substrate (tan(δ) = 0.02, εr = 4.3, h = 1.6). A modified ground plane with a parasitic patch is etched at bottom side of the dielectric substrate. The fabricated antenna exhibits the resonance at frequencies 0.83, 1.05, 1.6, 2.12, 3.25, 3.75 and 5.2 GHz. It covers six bands of frequencies band-1 (0.825-0.835 GHz), band-2 (0.913-1.22 GHz), band-3 (1.33-1.79 GHz) band-4 (2.04-2.18 GHz) band-5 (2.9-3.91 GHz) and band-6 (4.9-5.64 GHz) for |S11| ≤ -10 dB which are suitable for several wireless communication bands (i.e. GSM 900 MHz, 1800 MHz, Wi-MAX, Wi-Fi 802.11y and WLAN 802.11b/g/a). The surface current distribution and radiation pattern have been studied at resonating frequencies.
An SRR based compact wideband metamaterial inspired antenna for WiMAX (2.5-2.7)/WLAN (2.4-2.48)/Bluetooth (2.4-2.48)/LTE (2.3-2.4) applications has been fabricated and investigated in this paper. The proposed antenna structure has been designed with the concept of epsilon negative transmission line. It comprises a patch on the top of the substrate and SRR and ground connected through strip on the bottom of the substrate. The proposed antenna offers overall electrical dimensions of 0.29λ0×0.19λ0×0.015λ0 where λ0 represents the free space wavelength at the frequency of 2.88 GHz. Additionally, the designed antenna also provides simulated and measured -10 dB fractional bandwidths of 40.13% and 40.55% around the center frequencies of 2.89 and 2.88 GHz, respectively. The average simulated and measured total gains of the proposed antenna throughout the working band are 1.92 dB and 1.75 dB. Further the average simulated radiation efficiency throughout the entire -10 dB bandwidth of the deigned antenna is 96.2%.
In this paper, an experimental demonstration employing the decomposition of the time-reversal operator (known as DORT) in combination with pulse inversion is reported, allowing one to detect and selectively focus on nonlinear targets. DORT is a technique based on a multistatic configuration that separates the detected targets by means of eigendecomposition of the time reversal operator allowing for selective transmission of waves towards a target of interest. Pulse inversion is a technique that enhances harmonic responses while suppressing fundamental responses. By applying DORT with pulse inversion (PIDORT), harmonic detection and selective transmission to detected nonlinear targets can be enhanced. The results from our experiment show that PI-DORT can effectively detect and separate nonlinear targets for selective transmission.
In this paper, a dual band high gain miniaturized cross shaped patch antenna is proposed for IEEE 802.11ax applications. The radiating patch size is 0.330λ0x0.417λ0 on a low cost Flame Retardant 4 substrate. A cross shaped radiating element is designed to cover the upper band of IEEE 802.11ax, and a four ring circular Complementary Split Ring Resonator (CSRR) is etched on the cross shaped radiating element to cover the lower band of IEEE802.11ax. Thus the dual bands of 802.11ax are achieved. In order to enhance the gain, 2x2 array hexagonal metamaterial unit cell is positioned behind the substrate. To extract the constitutive parameters of the circular CSRR, NRW (Nicolson-Ross-Wier) retrieval method is used. The measured maximum gain is approximately 6 dBi, 10 dBi for 2.4 GHz, 5 GHz, respectively. Parametric study on the geometrical dimensions is investigated using HFSS 15.0.
A wideband composite right/left handed transmission line (CRLH-TL) antenna with cavity-backed substrate integrated waveguide (SIW) is proposed in this letter. This proposed antenna consists of a 2×2 array of mushroom unit cells, feeding line and cavity-backed SIW. By introducing SIW structure both impedance and gain of the antenna are improved. The proposed antenna has average gain of 7 dBi (peak measured gain 9.5 dBi), wide -10 dB impedance matching bandwidth of 55% from 5.2 GHz to 8.3 GHz, small size of 40 mm×50×4 mm, high integration ability, and reduced back radiation.
In this paper, a grade nested array constituted by a uniform linear array and a grade linear array with uniformly increasing inter-element is presented. The closed-form expression of the proposed array geometries and corresponding direction-of-arrival (DOA) estimation algorithm are derived. Theory analysis certifies that the proposed grade nested array can provide higher degrees of freedom (DOF) than some existing nested arrays. Some simulations are also presented to demonstrate the improved performance of the proposed nested array for DOA estimation of quasi-stationary signals.
A low computational complexity direction of departure (DOD) and direction of arrival (DOA) estimation method is derived for bistatic multiple-input multiple-output (MIMO) radar. In this method, we propose a novel bistatic MIMO radar geometry with one transmit array and two subarrays at the receive array, based on which the cross-correlation matrix is constructed. The DODs and DOAs can be estimated without eigendecomposition, thereby signicantly reduce computational burden. Moreover, the DODs and DOAs can be paired automatically. Simulation results verify that the proposed method holds better performance than the unitary estimation of signal parameters via rotational invariance technique and joint diagonalization direction matrix method.
This paper presents a novel dual-band bandpass filter by utilizing a new dual-mode resonator and a pair of single-mode split-ring resonators. The center frequencies and bandwidths of both passbands can be independently adjusted without affecting each other. Meanwhile, a capacitive source-load coupling is introduced to create transmission zeros near the passband edges, and the filter can obtain high skirt-selectivity. Such a dual-band bandpass filter operating at 3.5 GHz and 5.85 GHz with compact size is designed and fabricated.
In this paper, a novel dual-band scheme is proposed and analyzed for dual-band magnetic resonant wireless power transfer. The scheme consists of a novel resonant coil structure for dual-band resonance and a coupling loop for dual-band impedance matching. Circuit-based analysis and experiments verify that our scheme can achieve dual-band power transfer easily and effectively, with its dual-band reflection coefficient lower than -18 dB and transmission efficiency over 37.21% at a distance of 20 cm at 6.78 MHz and 13.56 MHz.
In this letter, a tuning fork shaped, differential dipole antenna, with two floating reflectors, is presented. The dipole antenna resonates at 1.22 GHz and has a fractional bandwidth (FBW) of 16.39% and a differential impedance of 100 Ω. The proposed antenna is composed of quarter wavelength tuning fork shaped dipole arms in the top layer. To improve robustness, while connecting to the differential circuits, two floating reflectors are used on the bottom layer, beneath the dipole arm. This method helps improving the gain by 7%. A microstrip-to-coplanar strip line (CPS) transition is designed to measure the stand-alone differential antenna. The measured gain and efficiency of the antenna are 2.14 dBi and 84%, respectively, at the resonant frequency. The possible targeted applications are circuits with differential inputs/outputs, like energy harvesting circuits, radio frequency tags, wireless communications and any other wireless sensor network nodes. Details of the design along with simulated and experimental results are presented and discussed.
This paper proposes a compact microstrip bandpass filter (BPF) with high selectivity. A folded stepped-impedance resonator (SIR) of which the high impedance part is realized by a coplanar waveguide on the ground layer is introduced to the filter design for miniaturization. Furthermore, source-load coupling is implemented by extended tapped lines (ETLs). High selectivity with four transmission zeros (TZs) can be achieved. The analysis of the filter is presented based on atransmission line circuit model and even- and odd-mode analysis method. An experimental filter with the size of 0.15λg*0.13λg (where λg is the guide wave-length at the center frequency) is designed to validate our methods.
This paper presents a hybrid method consisting of thin wire FDTD method and transmission line (TL) equations to be used for the coupling analysis of multiconductor transmission lines (MTLs) excited by a dipole antenna. In this method, the thin wire FDTD method is used to build the structure of the dipole antenna and obtain the radiation electromagnetic fields surrounding the MTLs, which are introduced into the TL equations as the distribution sources. The TL equations are utilized to model the coupling of the radiation electromagnetic fields to the MTLs, which are discrete by the scheme of the FDTD method to obtain the transient voltage and current responses on the lines and terminal loads. The accuracy and efficiency of this method have been verified by comparing with the commercial simulation software CST via one case. Moreover, the influences of the frequencies and polarization of the dipole antenna and the heights of the MTLs on the coupling of MTLs are analyzed.
This article was removed from the website on January 3, 2013, because it has been found to violate plagiarism rule of our journal.
Reflective filters are characterized by a frequency response with good matching at the band of interest and usually reactive impedance out of those frequencies which may adversely affect the system performance. On the other hand, reflectionless filters are characterized by good matching characteristic not only at the interest frequencies, but in the whole frequency spectrum which improves the overall linearity, efficiency, and reduces instability scenarios at the system level. Although several reflectionless structures can be found in the literature, the concatenation of different reflectionless sections, combined with the use of acoustic resonators has not been exploited yet. The particular electrical behavior of acoustic wave resonators, where two different resonant frequencies are found, allow to obtain a frequency response with high selectivity due to the presence of transmission zeros below and above the passband. A bandpass filter has been designed following the described procedure with a fractional bandwidth FBW = 2%, a pair of transmission zeros below and above the bandpass, and an improved out-of-band rejection with respect conventional topologies.
Electromagnetic wave propagation suffers attenuation and phase rotation by suspended dust particles especially in arid and semi-arid regions where occurrence of sand and dust storms (SDS) is predominant. The SDS phenomenon has received considerable interest in recent times with emphasis on signal attenuation and phase rotation effects. To this end, mathematical models of dust induced complex scattering are developed and proposed in this paper using Rayleigh method to compute attenuation and phase rotation of electromagnetic waves by considering dust particle shapes and best fit ellipsoids. This work also presents a new expression for the relation between visibility and dust concentration. The expression was included in the proposed models whose simulated results, compared with some published results, show close agreement. Attenuation and phase rotation in dry dust are found to be significant only when visibility becomes severe or at increased microwave bands.
A conformal wideband antenna is investigated and compared with its planar counterpart. First, a planar U-slot patch with about 43% fractional impedance bandwidth is designed. Then, it is mounted on a conformal cylindrical structure. It is observed that the fractional impedance bandwidth of the resulting conformal antenna increases to 50%, when it is bent along the H-plane. It is also found that the cross polarization discrimination of the antenna is improved. The effects of the arc angle and radius of the cylinder on the impedance bandwidth and radiation characteristics of the antenna are extensively studied. The conformal antenna was fabricated on a thin film of Kapton and tested. The measured and simulated results closely resembled each other.