This paper presents a novel design method to the absorber screen based on the receiving antenna technique. When the electromagnetic waves is incident upon the surface of absorbing structure, part of the electromagnetic energy transforms into current absorbed at the port, and the remaining energy is reflected. The former mechanism is similar to the receiving antenna. Hence, a dual-polarized magneto-electric dipole antenna is selected and optimized to obtain a broadband absorber screen unit after comparing the similarities between the antenna and absorber. The measurement results show that the finite 6×6 array absorber has a 73% bandwidth for 10 dB RCS reduction, while its thickness of substrate is below 1/9 wavelength of the center frequency in free space. The novel absorber screen can also be used in dual polarization because of its symmetrical property. The simulation and measurement are performed at the normal incidence in this paper.
Travelling wave antennas such as Vivaldi antennas, have conventionally been used for obtaining wideband and directional radiation pattern. This paper presents a novel way to obtain first of its kind, omnidirectional travelling wave antenna inspired by Vivaldi. Traditional omnidirectional antennas such as monopole and dipole rely on resonance condition which is usually satisfied on narrow band while the proposed antenna is relatively broadband owing to its travelling wave phenomenon. Moreover, typical Vivaldi antennas are double layered while our design requires only one layer. Antenna has been simulated and optimized in HFSS to operate in dual bands of UWB spectrum. The antenna has been measured and characterized using Keysight handheld VNA and Satimo Anechoic chamber. Good agreement between simulations and measurements have been obtained despite the fabrication tolerance of LPKF PCB manufacturing machine.
An SRR loaded compact RFID tag for broadband operation over the UHF RFID band is presented. The antenna structure is composed of a dipole whose arms are symmetrically loaded with square split ring resonators (SRRs) with a short circuited strip between the SRRs. The SRR sections made the antenna inductive and reduced the overall size. The measured read range characteristics of the proposed RFID tag are presented. The proposed tag operates in the entire UHF RFID bands with a maximum read range of 7 meters in the entire elevation angular ranges and over wide azimuthal angular ranges.
A new method to rapidly design 2D metamaterials for rectangular waveguides by rebuilding their dispersion properties is proposed. The Modal Expansion Theory (MET) is revisited for theoretical surfaces with fixed surface impedances ZS. Then, it is pursued for real dispersive anisotropic surfaces, which have surface impedances that are dependent on the frequency and the incidence angle. An algorithm which calculates the correct incidence angle of the guided electromagnetic mode at each frequency is presented. By including this algorithm in the MET and by combining it with a code based on the Finite Element Method (FEM) to calculate the surfaces impedances, dispersion diagrams of waveguides with real 2D anisotropic walls are correctly rebuilt. This is validated by comparing the results for two different metamaterials, corrugation- and T-structure, corrugations and metamaterials, with those obtained using a commercial software.
In this paper, a slot array with a new technique of metamaterial on Electromagnetic Band Gap (EBG) structure is used to demonstrate the possibility of building high gain top-mounted antenna for mobile base station. We describe the method for gain improvement by transferring the electromagnetic fields from a 1×4 slot array with a PEC reflector radiated through the cavity of curved woodpile EBG. The proposed technique not only has the advantages of reducing the total length of the slot array, but also provides higher gain and easier installation. In addition, to provide the azimuth patterns covering 360° around the base station, a triangular array configuration consisting of three panels of such an antenna array has also been presented, while the fabricated cavity of the curved woodpile EBG structure exhibits band gap characteristics at 2.1 GHz for realizing a resonant cavity of the slot array. This idea is verified by comparing between the results from Computer Simulation Technology (CST) software and the experimental results. Finally, it is found that the measured and simulated results are in a good qualitative agreement, and the antenna prototype yields directive gain of each panel around 17.1-17.2 dBi.
This paper presents an active resonant conductance method (ARCM) for the design of large traveling-wave-fed SIW linear slot arrays. Two key slot parameters, slot offsets and lengths, are derived from excitation coefficients with intermediary active resonant conductance. In this method, both dominant mode mutual coupling which includes external & internal and higher order modes mutual coupling are considered. An efficient way to derive active resonant conductance of slots in large slot arrays is proposed, which makes ARCM feasible for the design of large traveling-wave-fed linear slot arrays with high performance, e.g. low sidelobe level (SLL). Finally, a 16-slot and a 32-slot traveling-wave-fed SIW slot array antennas are designed. The processing of the 32-slot array design shows the efficiency of the proposed method for large arrays. The 16-slot array is fabricated and measured. Results from simulation and measurement verify the proposed method.
A conductor backed coplanar waveguide (CPW) fed multiband antenna is presented. The shorting of ground in CPW feed and conductor backed arrangement extend the area of ground plane. The proposed antenna consists of rectangular monopole with Complementary Split Ring Resonator (CSRR) engraved in the extended ground plane. The prototype antenna is designed, fabricated and measured. CSRR characteristics are also analyzed. Simulated and measured results of the antenna are in good agreement with each other and are discussed. The proposed antenna can be used for WiMAX, WLAN and RADAR applications at 3.4 GHz, 5.16 GHz and 9.5 GHz, respectively.
We propose an all circular-air-hole short-length polarization beam splitter (PBS) with high extinction ratio based on dual-core highly birefringent photonic crystal fiber (PCF). The impacts of geometrical parameters on the coupling polarization dependence, coupling length ratio (CLR), and propagation property are numerically investigated by the full-vector finite element method (FEM) and the semi-vector beam propagation method (BPM). From simulation results, it is seen that CLRs at the excitation wavelength of 1.55 μm can be optimized to be closed to the desired values of 3/2 and 4/3 to satisfy the sufficient condition of splitting polarized modes by appropriately tailoring the air-hole sizes. For the two optimal structures, the separation of x- and y-polarized modes can be achieved in short lengths of 1.41 mm and 2.89 mm at the operating wavelength of 1.55 μm, respectively. Furthermore, the extinction ratios at λ = 1.55 μm are estimated to be 97.7 dB and 88.1 dB, and the wavelength bandwidths of extinction ratio better than 15 dB are about 107 and 82 nm, respectively.
The advantages of integrating beamforming Butler matrix in 4×4 Multiple-Input Multiple-Output (MIMO) systems for underground mine wireless communications in the 2.4 GHz band are investigated. To satisfy both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions, two separate measurement campaigns are performed in a real L-shaped underground mine gallery; the first uses 4-elements beamforming conformal microstrip patch arrays (CMPA), while the second uses 4-elements beamforming Butler Network (BN-MIMO) by means of connecting a planar microstrip patch array to a Butler matrix. Due to its high radiation efficiency, the latter shows further performance for enhancing the channel propagation characteristics, and thus, for reducing the average path loss by about (2.2 dB, 5.1 dB) under (LOS, NLOS) conditions, respectively. Similarly, a reduction of (0.67 ns, 3.7 ns) in the RMS delay spread has been achieved to result in an additional gain of (4.6 MHz, 0.82 MHz) in the channel's coherence bandwidth. Furthermore, the orthogonal property of BN array radiation beams has led to a suppression of about (6%, 11%) in inter-subchannels correlations to boost (1.1 bit/s/Hz, 4.35 bit/s/Hz) in the channel capacity.
Wideband circularly polarized antenna is required for many satellite applications. Circularly polarized (CP) Equilateral Triangular-Ring Slot (ETRS) antenna has narrow 3-dB axial ratio bandwidth (ARBW) compared to its impedance bandwidth. Two diagonal line slots were introduced to ETRS for enhancing its 3-dB ARBW. The diagonal line slots were inserted on the left and right side of ETRS. Lengths of the left and right line slots correspond to the lowest and highest frequencies of ETRS antenna 3-dB ARBW, respectively. Both diagonal line slots have successfully improved 3-dB ARBW of ETRS antenna by achieving 680 MHz or 37% fractional bandwidth. Measured results of x-z and y-z planes of radiation patterns also confirm that the antenna has bidirectional radiation and presents good CP performance within its 3-dB ARBW. ETRS antenna RHCP gain is also improved thanks to the diagonal line slots insertion.
A wideband printed quadrifilar helical antenna (PQHA) using a novel single-layer compact feeding circuit is proposed in this paper. A low-cost single-layer feeding circuit which consists of a 180° compact rat race coupler and two 3 dB hybrid commercial couplers is incorporated at the bottom of the quadrifilar antenna. The antenna arms are tapered at the feeding point to improve impedance matching between the antenna and feeding circuit. The operating frequency band ranges from 1.9 to 2.3 GHz which shows that the proposed antenna is a good candidate for various applications such as satellite communication and broadcasting satellite systems. Therefore, the array of the proposed antenna on the simple cube satellite mock-up is investigated. By this antenna array configuration, a fully spherical radiation coverage is obtained around the structure. The bandwidth of the axial ratio (AR) with a wide beamwidth (160º) is 20% in operating frequency band. The measured peak gain of the proposed antenna varies between 2.6 and 3.2 dBic in the frequency band of interest. The measured 3 dB AR half-power beamwidth is 160º.
A wireless cyber secure zone has been created by controlling RF propagation using directive antennas and noise generation to establish a functional boundary for a wireless network. Directive microstrip patch antennas were constructed in the 2.4-GHz ISM band, and a commercial router was used to generate a wireless network on a specified channel. The FM transmitters for noise generation were set to the same channel in the 2.4-GHz ISM band, and the directive microstrip patch antennas were arranged facing outward creating an inner cyber secure zone for the wireless network. Outside the cyber secure zone, the wireless network was undetectable.
Recent technological achievements have made it low cost to realize indoor localization using the received signal strength (RSS) information from Wi-Fi signals. However, the current RSS-based indoor localization techniques have two major challenges: one is that the RSS signal is quite sensitive to channel conditions, and the other is that sufficient number of access points (APs) is needed to provide enough RSS measurements for guaranteeing good performance. To solve these problems, this paper proposes an adaptive compressive sensing (CS) based indoor localization method based on the IEEE 802.11 Wi-Fi standard. The novel feature of this method is to dynamically adjust both the dictionary and the sparse solution using an online dictionary learning (DL) technology so that the location solution can better match the real-time RSS scenario. Meanwhile, an improved approximate l0 norm minimization algorithm is presented to enhance sparse recovery speed and reduce the number of APs required by indoor localization systems. The effectiveness of the proposed scheme is demonstrated by experimental results where the proposed algorithm yields substantial improvement for localization performance and reduces computation complexity.
A microstrip filtering balun with a wide stopband is presented. Its filtering function is realized by four meandering stepped impedance resonators (SIRs). Except for an identical fundamental-mode resonant frequency, the SIRs have different high-order resonant frequencies. Thus, the parasitic passbands are suppressed, and a wide stopband is achieved. The unbalance-to-balance transition is accomplished by introducing two coupling output ports at two symmetry positions of the output SIR. The voltages at symmetrical positions have equal magnitudes and opposite phases, thus, signals coupled from the symmetry positions also have equal magnitude and opposite phase, i.e., balanced output signals are achieved. A more general design approach is discussed in detail, and the proposed approach is similar to the design method of the conventional filter except that a small modification is made. Additionally, two kinds of external coupling structures, microstrip coupling lines and tapped line, are compared in terms of stopband performance. The comparison shows that better stopband performance is observed when utilizing the microstrip coupling lines as the external coupling structure. A filtering balun with central frequency of 2.4 GHz and Chebyshev frequency response is designed, fabricated and measured. The measured results give a reasonable agreement with the simulated ones, which verifies the effectiveness of the filtering balun.
This paper presents an improved structure of a Gysel combiner/divider suitable for high-power applications. The proposed structure makes use of stepped-impedance load line features to implement a simple, compact, low loss and sufficiently wideband Gysel configuration. It also improves isolation and facilitates design flexibility for the load location. Measurements agree with expected simulated results thus, demonstrating the proposed structure with a 10% fractional bandwidth while maintaining 20 dB of return loss and 0.25 dB of insertion loss.
A compact quad-band slot antenna is presented in this paper. The proposed antenna consists of ground plane, dielectric material and top radiation patch. Firstly, symmetrical L-shaped slots are inserted in a radiation patch. Then to achieve multiband performances, symmetrical square spiral slots and a snakelike area with two symmetrical arms enclosed by a long slot in the ground plane are adopted. The process of design and parametric studies are illustrated in detail. The final quad-band antenna has a small size of 0.22λg×0.28λg = 17×22 mm2 (where λg is the guide wavelength) and covers the frequency bands from 2.39 to 2.48 GHz for lower WLAN, 3.64-3.73 GHz for downlink and 5.98-6.30 GHz for uplink standard satellite communications, and 6.97-7.18 GHz mainly used by the Indian National Satellite System (INSAT). The measured results of the proposed quad-band antenna are in accordance with simulated analysis and show good performance of return loss characteristics, radiation patterns, bandwidths and gains. Especially, with a very small size, the proposed antenna is suitable to be integrated with a portable device for varieties of wireless communication applications.
A low-profile wideband multiple-input-multiple-output (MIMO) antenna is presented. The proposed antenna is suitable for mobile terminals applications, as its measured -10 dB bandwidth ranges from 1.56 GHz to 2.77 GHz. The overall antenna efficiency ranges from 68% to 83% over the operating bandwidth. The overall size of the proposed antenna is 60×97×0.8 mm3. A novel isolation structure is employed to achieve isolation range of -26 dB to -16 dB. The radiation patterns are measured, and envelope correlation coefficient is evaluated. The simulated and measured results are in good agreement.
In this paper, we propose a systematic simulation-based approach to estimate the reading distance of an RKE system. In our electromagnetic (EM) simulation, a receiving RKE antenna and a vehicle structure, including both exterior and interior, are modeled as piece-wise mesh triangles to obtain accurate radiation characteristics of the antenna mounted inside the vehicle. The reading distance is then estimated by a two-ray propagation model that includes effects of space loss, ground properties, and antenna polarizations for various orientations and heights of handheld devices. The estimated distances are compared to the measurement, and results show that the proposed approach is suitable to replace the measurement-based approach with an average error of less than 2 m.
The main section of this paper comprehensively analyzes electrical shielding effectiveness (ESE) of enclosures with rectangular apertures for producing valuable information used in electromagnetic interference and compatibility guiding enclosure designers of electronic devices. Firstly, results of conventional analytical equivalent circuit model, measurement and simulation with computer simulating technology (CSTTM) of ESE for an enclosure with a single aperture size are compared to improve closeness in different models at 0-1 GHz. After getting a suitable simulation model, all possible parameters with detailed cases are examined to approach beneficial conclusions. Especially, size of enclosure, aperture size, aperture shape, configuration and number of apertures, probe position parameters that affect ESE are investigated. Also, some double parameters are analyzed together to achieve detailed review as two enclosure dimensions, two aperture dimensions and probe position with enclosure depth. Therefore, three-dimensional graphical investigations are performed. Obtained results of these parametric approaches are explained with acceptable reasons. Finally, detailed and itemized comments are given about simulated results of ESE parameters, which are collected from previous sections.
We present a method to improve the resolution of available hyperlenses in the literature. In this method, we combine the operation of hyperlens with the recently proposed plasmon injection scheme for loss compensation in metamaterials. Image of an object, which is otherwise not resolvable by the hyperlens alone, was reconstructed up to the minimum feature size of one seventh of the free-space wavelength.