In this paper a generalized concept to generate two band notches by adding parasitic elements having predictable positions to a wide slot ultra-wide band (UWB) antenna is proposed. The elimination of the wireless local area network (5.15-5.825 GHz) is achieved by a pair of radiating parasitic elements. Each element operates as a quarter wavelength resonator. A pair of half wavelength resonators in a form of a pair of parasitic strips is engraved in the ground plane side of the substrate directly behind the antenna tuning stub to break the coupling between the feed line and the slot, which represents the basic operation concept of the wide slot antenna, at the X-band satellite communications down link (7.25-7.745 GHz). Analysis shows that the proposed mechanisms are suitable for all wide slot antennas. The simulation and measured parameters are in good agreement, and results also show that the antenna has high voltage standing wave ratio and low gain inside the eliminated bands, while outside the notched bands it has a bandwidth that covers the entire UWB band and has very stable radiation characteristics.
Ultra Wideband (UWB) has been deliberated as a promising technology for short-range wireless communication with large unlicensed frequency band for commercial, enterprise private and public uses. Designing an antenna of compact size for portable wireless devices is one of the challenges especially for UWB based wireless communication technologies. In this paper, a novel smiley fractal antenna, employed with N-notch feed and modified ground plane, is designed and developed to achieve the desired characteristics. The proposed antenna is of compact size with dimensions of 34×32×1.6 mm3, fabricated on an FR-4 substrate with εr=4.4. The radiation pattern of the proposed antenna is omni-directional with a maximum gain of 4.83 dB and efficiency of 93.55% obtained through 3D electromagnetic simulation software tools. The simulated results are compared with measured ones using RF equipment. The results obtained show that the proposed Smiley Fractal Antenna (SFA) is a suitable candidate for UWB wireless communication application.
A near-field resonant parasitic (NFRP) antenna is presented. Unlike the conventional NFRP antenna, which is fed by coaxial cables, the topology is driven by a planar ``monopole''. In this way, the antenna and the front end circuit can be designed in a single plane, which is crucial for system integration. The radiator is electrically small (λ0/19.3 × λ0/10.47 × λ0/76.4) while reaching a high efficiency (94%) and a good bandwidth (85 MHz). The operating frequency and input impedance are easily tailored. Measured results verify the working mechanism.
A novel multi-layer third-order substrate integrated waveguide (SIW) bandpass filter with improved lower stopband performance is proposed. TE201-mode in folded-SIW cavity is utilized to implement negative cross coupling, and the TE101-mode is taken as a non-resonating node (NRN) for implementing bypass coupling. A circular aperture etched on the middle metal layer is used to realize coupling between source and the second SIW cavity. Then, three transmission zeros located below the passband can be obtained to improve stopband attenuation. Meanwhile, better spurious suppression performance above passband is achieved. A filter sample is designed and fabricated with multi-layer low-temperature co-fired ceramic (LTCC) technology. The measured S-parameters agree well with the simulated ones, with its predicted good performance.
To remotely detect corona discharge from High-Voltage Direct Current (HVDC) transmission lines, a detecting system combining detecting platform and data progressing system is designed. Detecting platform is developed resorting to the principle of differential noise reduction, which can fulfill narrow-band detection breaking away interference from broadcasting and easily catch the electrostatic discharge signal. To get rid of interference from spark discharge, a data progressing system containing feature extractions, clustering and recognition technologies is developed. Clustering is realized by extracting five discharge features, including peak factor, form factor, skewness, kurtosis and mean square error. The unsupervised clustering Fuzzy C-Means (FCM) method is used to achieve fast separation for electrostatic discharges and provide training set for pattern recognition. Pattern recognition resorts to Support Vector Machine (SVM) method. For comparison, Back Propagation (BP) and Learning Vector Quantization (LVQ) approaches are taken to test the recognition ability. The results show that SVM recognizer with a recognition rate of 97.5% achieves higher performance than BP and LVQ methods. It can be concluded that the detecting system can be an interesting alternative for electrostatic discharge detection.
In this paper, an efficient spectral signature based chipless RFID tag is presented, where 4N number of words can be coded using only N number of resonators. As data bit encoding element, the proposed tag utilizes a number of modified complementary split ring resonators (MCSRR). A novel resonance detuning mechanism proposed here allows the use of an MCSRR to independently encode two data bits instead of one bit. Compared with two separate rings based CSRR, the proposed MCSRR occupies 56% less area and also reduces the resonance bandwidth requirement by more than 60%. The multiresonator circuit and the UWB antennas are implemented on a thin (0.127 mm) substrate with only single sided metallization. The proposed tag has great prospect to yield an ultra-low cost chipless RFID tag that may replace barcode in the long run.
Fresnel Zone Plate Lenses (FZPLs) are transparent-opaque lenses that filter the desirable phase. The centred Fresnel lenses have a strong back radiation towards the feed. In order to solve this drawback, offset feeding or offset pointing lenses are used. In this work, both offset FZPLs are studied using an optical physics method and experimentally characterized in the millimeter band. Two prototypes have been manufactured and measured, presenting a narrow beamwidth. The characteristics of pointing of this beam are studied depending on the feed gain. This work shows the pointing characteristics of the lenses, simply moving the lens in a plane.
A novel dual-band circularly polarized monopole antenna fed by coplanar waveguide (CPW) is proposed. Deformed monopole and asymmetrical ground are utilized to achieve dual-band characteristic, by adjusting the tuning stub close to the deformed monopole, the antenna can be further improved to a good performance. Measured results show that the proposed antenna impedance bandwidth is 1.44 GHz centered at 3.42 GHz for the lower band and 400 MHz centered at 5.2 GHz for the upper band, the 3-dB axial ratio bandwidth is 900 MHz centered at 3.25 GHz and 400 MHz centered at 5.1 GHz respectively. The measured results agree well with the simulated results.
In this paper, two miniaturized (20 x 20 mm2) coplanar waveguide fed slot antennas are proposed. Both the antennas are characterized by ultra wide impedance bandwidth while one of them has an additional narrow band near 2.5 GHz. The radiating element of the proposed antennas is a modified rectangular geometry which is excited by a 50 ohm line. The radiating element of the proposed antennas is a modified rectangular geometry which is excited by a 50 ohm line. The slot in the ground plane is stair case shape for UWB antenna and octagonal shape for the dual-band antenna. By modifying the slot and adding a λ/4 length metallic stub, an extra resonance is created for the dual-band antenna. The measured impedance bandwidth of the UWB antenna is 7.8 GHz (3.4-11.2 GHz). The impedance bandwidths of the dual-band antenna are 150 MHz (2.45-2.6 GHz) and 8.4 GHz (3.2-11.6 GHz). The radiation patterns of the proposed antenna are found to be bi-directional in E-plane and omnidirectional in H-plane. All the measured and simulated results are in good agreement.
A high gain wideband antenna array with an omnidirectional radiation pattern is presented for base station. The antenna array is composed of four elements and a circular four-way power divider. The proposed planar antenna element consists of four pairs of arc dipoles and a balun, which can achieve a better impedance match and a wider frequency range. Furthermore, the conductor ground of the power divider with a larger size than the element is placed under the four antennas, which can also enhance the peak gain. The antenna array is simulated, fabricated and measured. The measurement results show that the proposed antenna array can achieve a bandwidth from 1.62 GHz to 2.43 GHz or a relative bandwidth of 39.4%. The antenna array has a peak gain of 6.4-7.2 dBi in the work band and obtains a radiation efficiency of 88%. The simulated and measured results show that the proposed antenna array is a good candidate as a base station antenna for GSM, PCS, and UMTS applications.
A coupled oscillator array using push-push oscillators and resonator type coupling circuits is presented. In the proposed oscillator array, the coupling circuit operates at the fundamental frequency and the output signal is the 2nd harmonics. The adjacent oscillators are connected via the coupling circuits. The coupling circuit is used to synchronize the oscillators and control the phase difference of the output signals. In this study, a three elements push-push oscillator array has been designed in Ku band. The measured phase shift between the output signals of the adjacent oscillators is 511 degrees at the maximum.
This paper reports design of a new dual-band T-type impedance transformer also exhibiting DC-blocking feature. The design aims at achieving matching for frequency-dependent complex loads having distinct values at two arbitrary frequencies to Zs (here, 50 Ω). A step-wise analysis on the developed dual-band impedance transformer provides simple closed-form design equations. The design is verified by extensive simulation in Agilent ADS. For experimental verification a PCB prototype is fabricated using FR-4 material, operating at 1.45 GHz and 2.61 GHz. A good result is obtained confirming the theory and simulation.
In this paper, a co-prime symmetric sparse cross array is employed to estimate two-dimensional (2-D) direction-of-arrival (DOA). Some special forth-order-cumulants (FOCs) of array received data are used to construct a high-order matrix that is equivalent to a cross-covariance matrix based on two uniform linear arrays. After some modifications, an existing 2-D DOA estimation algorithm becomes more effective, and it shows further improved performance when the co-prime symmetric cross array is utilized. Numerical simulations demonstrate the effectiveness of our methods.
A new dual-polarized antenna loading frequency-selective surface (FSS) is proposed for 5G wireless local networks (WLANs) application. The antenna consists of two orthogonal bow-tie dipoles and a ground plane. A new wideband FSS is designed comprising ring-slot connecting rectangular slots. The reflection coefficient of wideband FSS is less than 0.9 from 4-6.5 GHz. The phase of reflection coefficient is -163°at 5.5 GHz. The novel cell analyzed by the equivalent circuit is given and simulated. The wideband FSS is employed as a superstrate layer for bandwidth enhancement and radiation gain improvement of the antenna. After loading wideband FSS, the measured bandwidth is 5.3-6.3 GHz (17.2%) with S11 and S22 both less than -10 dB, which cover various 5G WLAN bandwidths. The gain of the antenna is 12.1 dBi at 5.5 GHz. The bandwidth of antenna with FSS increases 40%, and gain improves 5.6 dBi. The simulated and measured results agree well.
This paper presents the simulation and fabrication of a new power divider/combiner based on a new waveguide H-plane folded magic-T structure. Measurements of the fabricated magic-T confirm the accuracy of the optimization algorithms existing in the CST software (Genetic algorithm, Particle Swarm Optimization algorithm PSO, etc.). The magic-T structure exhibits moderate bandwidth response in the frequency range of 8-10 GHz. Also, it shows that the return loss is better than -15 dB, the insertion loss about -3.4 dB, and the isolation between the two output ports better than -25 dB in the frequency range of 8.4-10 GHz, with good transmission phase characteristics. Based on this magic-T structure, a 1:4 power divider/combiner is simulated and tested. The measured results show that the insertion loss is about -6.5±0.25 dB, the return loss less than -15 dB, the isolation among the output ports less than -25 dB, the combining efficiency about 89%, and the transmission phase differences are about ±2° in the frequency range of 8-10 GHz.
The 2 × 2 multiple-input-multiple-output (MIMO) capacities of three types of colocated dual-polarized loop (DPL) antennas with different current distributions and isolations are investigated in the free space (FS) channel, the corridor with perfect electric conductor walls (PEC corridor) and the corridor with concrete walls (CON corridor), separately. Capacity results show strong dependences on both the structure and the position of the DPL antenna, in addition to the propagation conditions. For all the three propagation scenarios, the largest capacity can be reached is in the PEC corridor, employing the DPL antenna with a uniform current distribution and a high isolation. Specifically, for a 20 dB signal-to-noise ratio (SNR), the maximum dual-polarized MIMO capacity is 13.1 bps/Hz, which is 1.97 time of that obtained by the one-polarized loop. It is also noted that, the rich-multipath environment can increase the robustness of the DPL MIMO system and the difference of the MIMO capacity obtained by different antenna structures will get smaller with respect to that in the FS channel.
One of the most important aspects for body centric communication is the development of the textile antenna for on-body communication. Antennas for on-body environment usually suffer performance degradation caused by the human body. Apart from that, textile antenna gets easily bent, flexed, wrinkled or wet. This paper presents an investigation on three different designs and types of planar antennas, which are single band textile dipole antenna, fractal Koch multiband dipole antenna and monopole ultra wide band antennas. The performance of the antennas has been evaluated in terms of bending, wetness condition and on-body simulation. The results show that the bending effect is not critical in free space for the planar antennas, but the performance is notably degraded under wet condition while the antenna reflection coefficient is shifted when placed on the human body.
A coupled-line circuit structure is proposed in this paper to design a modified Schiffman phase shifter with short reference line. Based on the traditional transmission line theory and ABCD parameters, closed-form mathematical equations for electrical and scattering parameters are obtained. Obviously, this proposed coupled-line phase shifter has several advantages such as arbitrary phase difference, easy implementation, and analytical design method. Finally, two examples of microstrip coupled-line phase shifter, which have fractional bandwidth over 45%, are fabricated and measured. Good agreements between the simulated and measured results verify our design.
A compact ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna with a small size of 22×36 mm2 is proposed for portable devices. The MIMO antenna consists of two symmetric slot antenna elements with back-to-back separation of 7 mm. Adjusting the open-ended stepped radiator and position of the microstrip line can realize UWB impedance matching. In order to achieve wideband and high isolation, a cross-shaped decoupling slot and connecting metal line are etched on the ground plane. The cross-shaped slot between the antenna elements is used to decrease the mutual coupling caused by near-field at middle and high bands. The connecting line can be interpreted as a neutralized line, which produces an additional current path for the coupling ground currents. Measured S-parameters show that the isolation is better than -16 dB across the UWB of 3.1-10.6 GHz. The radiation pattern, gain, and envelope correlation coefficient are also measured. The proposed antenna with a simple structure and compact size achieves good impedance matching and excellent port isolation simultaneously, and is a good candidate for UWB MIMO systems.
A miniaturized annular ring slot antenna is presented. The antenna consists of an annular ring slot structure and a novel folded matching structure. The annular ring slot structure is printed on a substrate and shorted concentrically with a set of conductive vias. The additional matching structure is a ring cavity attached to the back of the annular ring slot structure. Firstly, the diameter of the proposed antenna is reduced by using the folded matching structure comparing with traditional annular ring slot antennas. Secondly, the impedance matching of the proposed antenna is achieved by optimizing the size of the matching structure. A prototype of the proposed antenna with a height of 3.048 mm (0.03λ) and a radius of 47.2 mm (0.4λ) is designed, fabricated and measured. The antenna resonates at 2.67 GHz and has a monopole-like radiation pattern, which shows that the antenna is suitable for the applications of taking off, landing, and long distance communications for a small or mini UAV.