In this paper, hyperbolic metamaterials slot waveguides based on graphene have been proposed to explore the optical characteristics. The hyperbolic metamaterials are composed of graphene-dielectric alternating multilayer. It has been verified in our proposed structure that the optical field is enhanced efficiently in the slot region, which results in the optical gradient force becoming larger as the distance of slot region becomes smaller. Both numerical simulation and theoretical analysis systematically reveal that the stronger gradient force can be achieved through smaller slot gap or lower chemical potential. Furthermore, the optical properties of two coupled waveguides have been studied under the relation of incident wavelength, chemical potential of graphene, composition of graphene-dielectric multilayer (eg., number of periods, filling factor of graphene) of the waveguides in this work. We find that a larger gradient force can be obtained by adjusting the height of waveguides, either decreasing the thickness of dielectric with constant number of periods or compressing the number of periods with fixed graphene filling factor. Our results will be helpful to the study of the optical field in the infrared region and also has great potentials in nanoscale manipulation and plasmonic devices.
A 400 GHz monolithic leaky wave antenna (LWA) is presented in this paper. The proposed LWA, constructed by the unit cell with multiple structural parameters, is regarded as the on-chip microstrip with perforation on the signal trace and the ground plane. A hybrid full-wave eigenvalue method theoretically extracts the complex propagation constants of first higher-order mode (EH1) of the perforated microstrip to improve the unit cell design. The extracted results also assist in realizing the differential feeding network to excite the leaky mode of the proposed antenna in high efficiency. A 400 GHz LWA prototype is designed and fabricated in CMOS 0.13 μm 1P8M process. The on-chip experiments show the measured input return loss including the effects of the contact pad lower than 10 dB from 380 GHz to 420 GHz. The measured antenna gain is higher than 0.8 dBi and has a maximum value of 1.3 dBi at 400 GHz. From 390 GHz to 405 GHz, the measured main beam is at 33° to 43° from broadside, indicating good agreement with the calculated results.
In this work, the dosimetry for two resonant modes of a highly resonant wireless power transfer (HR-WPT) system is investigated, and the results are compared. The physical mechanism of the two resonant modes, which occur when the two transmitting and receiving resonators are extremely close to one another, is presented with the simulated results and the equivalent circuit models for the HR-WPT system. The difference between the two resonant modes for the specific absorption rate induced in the head model is discussed by comparing the electromagnetic fields for each mode. Furthermore, the dosimetry for the four-coil HR-WPT system is also investigated under the conditions of a single resonant mode and two resonant modes. The specific absorption rates (SARs) are calculated with head-size and body-size simplified human models at various distances from the WPT system and in each mode. The electric and magnetic fields of the odd mode show stronger distribution than those of the even mode in the area near to the WPT system, while the opposite results are found in the area farther away.
Long-range wireless power transmission (WPT) is implemented with the phased array transmitter technology, which has been extensively applied in the field of the radar systems. The cost of a conventional phased array transmitter module scales up in proportion to the number of antenna elements, as the massive number of transmit channels results in the increasing complexity of hardware and feeding antenna elements. Besides, the conventional phase-shifting transmitter architecture has lower DC to RF power conversion efficiency due to the insertion loss of power combining network at microwave frequency. In this paper, the concept of spatial power combining transmitter is utilized, and the upconversion circuit is greatly simplified to an injection locked oscillator. Our WPT system is implemented with the technology of oscillator array antenna at 2.4 GHz, which converts DC power to RF power and radiates into the air directly. The feedback voltage controlled oscillator (VCO) is implemented as the microwave source using a off-the-shelf bandpass filter, and the external signal is injected to the oscillator via a microstrip coupler. {The oscillator core shows the DC-to-RF conversion efficiency of 45.87% with the injected power of 0 dBm at 2.4 GHz. Then the digital phase shifter is used to phase shifting the injected signal to extend the beam coverage. From the link budget analysis, the overall DC-to-DC efficiency of our highly-integrated system shows 1.5 times (0.22%) of the conventional phased array (0.15%) when the separation between the transmit array and the receive horn antenna is 1.2 meter. Therefore, as an modularized array, the proposed system demonstrates the promising capability of upscaling to an efficient massive array with greatly reduced bill-of-materials (BOM).
A beam-reconfigurable printed antenna on an Artificial Magnetic Conductor (AMC) is proposed for navigation and radiolocation applications at a frequency of 9.41 GHz. The AMC is formed based on a periodic Jerusalem cross shaped slot structure and is located in between two substrate layers, close to the radiator. The AMC plane has a bandwidth of 1.95 GHz around the targeted frequency of 9.41 GHz. By integrating micro-electro-mechanical system (MEMS) switches on the folded patches in combination with parasitic elements, a beam steering capability of up to ±58° is achieved with a rear full ground plane. This eliminates the need for a mechanical steering system, which is traditional in the applications targeted. The antenna achieves a high gain of 8.08 dB and 90% efficiency. A good agreement between simulated and measured results is obtained.
A topology, equations and design methodology for complex impedance-transforming branch-line hybrid couplers are presented. This method also allows the realization of real impedance-transforming to higher impedances. Limitations for real, imaginary and complex impedances are discussed. Test results are shown for a 3 dB 50 to 450 Ω hybrid coupler, at a 2 GHz center frequency, with a 21% bandwidth, an amplitude balance of 4.35±1 dB and a phase balance of 92.16°±8.8°. To showcase the complex impedance scenario, two 3 dB 50 Ω to 70-200j Ω are measured at a 2 GHz center frequency. One of these couplers uses a technique for reducing the chip size, yielding a 22.5% bandwith, 4-0.9 dB amplitude balance and 93.22°-6.74° phase balance, while acomplishing a 25% size reduction.
In this paper, a compact circularly polarized antenna based on a resonant quadrifilar spiral structure for the application of UHF RFID handheld reader is proposed and demonstrated experimentally. To reduce antenna size and improve impedance matching, the original resonant arms are revised by bending inverted-F structures and printing them on dielectric substrate, and the four arms are fed by a four-way phase shift network. Such an antenna indicates stable circular polarization performance and wide beam-width. The gain bandwidth (>2 dBi) can cover the frequency band from 902 MHz to 928 MHz, which is suitable for most of the popular UHF RFID system in the world. Moreover, the 1×4 array and 2×2 array based on previously demonstrated antenna unit are numerically investigated. The array performances, including the gain, beam scanning and low side-lobe are discussed.
A modified Koch fractal shape is used to decrease the dimensions of an antenna and resonates at more than one band for agricultural application. A new feeding technique of aperture coupled method called a non-uniform annular Photonic Band Gap is applied in order to integrate the designed antenna to the active elements. Subsequently, a transmission line transformer is designed using Genetic algorithm to achieve a perfect matching between the active element (amplifier) and the load (antenna). The proposed antenna is designed and fabricated. The results show that the proposed antenna has a high gain of 20.5 dB, 21 dB, and 22 dB at 0.915 GHz, 1.8 GHz and 2.45 GHz respectively with a compact size and low cost. The results predict its prospect as a promising alternative to the conventional one, which is compatibly applicable to agriculture applications especially when multiband function is required.
A novel 1.8 GHz compact microstrip low-pass filter (LPF) based on quasi-yagi defected ground structure (DGS) and compensated capacitors is proposed in this paper. The filter has a very sharp cut-off frequency response with low insertion loss and achieves a wide reject band with overall 20 dB attenuation from 2.8 GHz up to 10 GHz. The equivalent circuit model of Yagi-DGS-unit is derived using AWR software, and the circuit parameters are extracted by using a simple circuit analysis method. The advantage of this structure is that the reject band can be controlled by tuning the dimension of Yagi-arms at higher frequency rang. The proposed 1.8 low-pass filter is designed using microwave office electromagnetic software and fabricated on the RO4003 ceramic structure with dielectric constant of 3.38. The compact filter occupies an area of (0.45λg × 0.35λg) with λg = 44 mm. A comparison between simulation and measurement results confirms the validity of the LPF configuration and design procedure. In order to improve the compactness of the proposed LPF, a new multi-layer method has been employed. Finally, a new minimized LPF-topology 50% more compact than the conventional is realized.
As important fundamental equipment, high voltage switchgears are widely used in electric power systems and directly relative to the power reliability and quality. Partial discharge (PD) online monitoring is one of the most effective methods used for insulation testing and diagnosis in high voltage switchgears and power systems. This paper proposes a unique ultra-wide-band (UWB) antenna with high performance for PD ultra-high-frequency (UHF) detection in high voltage switchgears. Actual PD experiments were carried out, and the designed antenna was used for PD measurements. The measured results demonstrate that the proposed antenna has wide work frequency band, good omnidirectional radiation patterns and appreciable gain, which indicate that the proposed antenna is suitable for UHF online monitoring of PDs in high voltage switchgears.
In this paper, a novel quasi-periodic structure for rectangular waveguide technology is proposed. The constituent unit cells of the structure feature a resonant behavior, providing high attenuation levels in the stopband with a compact (small period) size. By applying a smooth taper-like variation to the height of the periodic structure, very good matching is achieved in the passband while the bandwidth of the stopband is strongly increased. Moreover, by smoothly tapering the width of the structure, a band-pass frequency behavior is obtained. In order to demonstrate the capabilities of the novel quasi-periodic structure proposed, a band-pass structure with good matching, wide rejected band, and high-power handling capability has been designed, fabricated, and measured obtaining very good results.
In this study, a Six-port Reflectometer (SPR) with dielectric probe sensor is used to predict relative dielectric, εrof normal and tumorous breast tissue in frequency range from 2.34\,GHz to 3.0 GHz. Other than that, a superstrate with an exterior copper layer is overlaid on the surface of a primitive Five-port Ring Circuit (FPRC), which is also a denominated, enhanced superstrate FPRC. It is the main component of the SPR and is presented in this paper as well. The enhanced superstrate FPRC is capable of improving its operating bandwidth by 26{\%} and shifting the operating centre frequency to a lower value without increasing circuit physical size. The detailed design and characteristics of the FPRC are described here. In addition, the enhanced superstrate FPRC is integrated into the SPR for one-port reflection coefficient measurement. The measurement using the SPR is benchmarked with Agilent's E5071C Vector Network Analyzer (VNA) for one-port reflection coefficient. Maximum absolute mean error of the linear magnitude and phase measurements are recorded to be 0.03 and 5.50°, respectively. In addition, maximum absolute error of the predicted dielectric and loss factor are 1.77 and 0.61, respectively.
A wideband diplexer for the extended C-band feed antenna system is proposed in this paper. The diplexer operates in the receiving band (Rx) 3.625-4.8 GHz and transmitting band (Tx) 5.85-7.025 GHz, which give 28% and 19% bandwidths at Rx and Tx bands, respectively. In order to cover such a broadband, a side coupling T-shaped junction and a corrugated low-pass filter scheme are adopted. The T-shaped junction and the filter are designed separately, and then combined for optimization. A prototype is fabricated and measured. Measured results show a good agreement with the calculated ones. The return loss is less than -21 dB, transmission loss less than 0.21 dB, Rx/Tx isolation better than 45 dB, and Tx/Rx isolation better than 70 dB.
This paper proposes a horn antenna with limiting plates inside to produce symmetrical pattern in E-plane and H-plane. Sidelobes of the antenna are reduced using the limiting plates, and therefore, the beam efficiency of the antenna is improved up to 90 % without changing the antenna dimensions. The antenna dimensions are adjusted to achieve the best beam efficiency. Simultaneously, the reflection coefficient is maintained lower than -15 dB. In addition, it is indicated that this antenna has wide bandwidths without reducing the efficiency and performance of the antenna. Finally, the reflection coefficient is improved to -20 dB without degradation of the antenna performance.
In this paper, four novel wide-band dual tapered slot (DTS) microstrip antennas (MSAs) are proposed for X-Band Satellite Communications (SATCOM) applications. Three of them have stripline feeds between SMA connector and tapering profile, whereas the fourth one omits the stripline feed. Each antenna consists of two microstrip lines on each side of an FR-4 substrate, fed with a coaxial connector from one face. Towards the edges, the distance between conductors is increasing gradually. The aim of this study is to design receiver antennas capable of operating in X-Band Satellite Communications (7250-7750 MHz) range and investigate the effects of tapering profiles on the performance. For this purpose, each antenna is defined in terms of parameters, and the optimum values for all parameters are calculated using High Frequency Structure Simulator (HFSS) software. The antennas are simulated and practically fabricated. Results show good agreement between simulations and measurements. The antennas have impedance bandwidth of 380 MHz centered at 7448 MHz for dual linearly tapering, 540 MHz centered at 7434 MHz for dual circularly tapering, 900 MHz centered at 7555 MHz for dual exponentially tapering, within the aimed Super High Frequency (SHF) range. Also, the designed fourth antenna having dual circularly tapering without the stripline feed has a bandwidth of 1150 MHz centered at 7676 MHz. It is proposed that taper profile affects bandwidth, gain, radiation efficiency, radiation pattern and antenna dimensions.
This article focuses on the development of a high gain, broadband, circularly polarized Electromagnetic Band Gap (EBG) antenna operating at 60 GHz. The designed antenna is configured with a superstrate based on a frequency selective surface (FSS) placed in front of a cross dielectric resonator antenna (XDRA), installed into a ground plane, which acts as an excitation source. A fast Leaky-Wave approach based on transverse equivalent network (TEN) is used to deduce analytical radiation patterns formulas of the proposed antenna. The proposed analytical model was implemented and verified by a comparison with both numerical and experimental results. The reported results showed very satisfactory performances with an achievable impedance bandwidth (S11< -10 dB) of 11.7% from 56 to 63 GHz, an axial-ratio bandwidth (AR<3 dB) of 5.4% from 58.9 to 62.1 GHz and a stable gain of 16.7 dBi within the passband. A good agreement among analytical, numerical and measured results is successfully achieved and falls well within initially set specifications.
A compact monopole antenna with broadband circular polarization for global navigation satellite system (GNSS) applications is presented in this paper. The proposed antenna comprises a simple tilted radiator fed by 50-Ohm microstrip line and an improved ground plane. By embedding two isosceles right triangular slits and introducing an isosceles right triangular perturbation in the ground plane, the circularly polarized (CP) performance can be improved significantly. The impedance and circular polarization characteristics are studied by simulation and measurement. With a compact size of 79×79×1.5 mm3 for the fabricated antenna, a measured 10-dB return loss bandwidth of 35.6% (1.13-1.62 GHz) and a 3-dB AR bandwidth of 35.4% (1.14-1.63 GHz) can be achieved.
This paper presents a novel, dual, three-stepped-trident, planar, monopole antenna for ultra-wideband applications. The planar trident type antenna is designed, simulated, and fabricated. Its impedance bandwidth, radiation pattern and gain performances were measured. This antenna operates in the ultra-wideband from 3.0 GHz to 12.15 GHz. The maximum gain of this antenna design is 5.5 dBi. Measurements confirm the simulated results over the frequency of operation.
A novel miniaturized design of UWB monopole antenna is presented and investigated for oil pipeline imaging. In the proposed antenna, an annular-ring shaped radiating patch, slotted ground plane and a feed-line embedded with a semicircular stub are used to enhance the bandwidth. The slotted ground-plane has two extended rectangular strips on its two sides to excite the lower frequency resonance. The proposed antenna design exhibits an enhanced bandwidth of 22 GHz from 3 to 25 GHz (for return loss <10 dB) which provides a wide usable fractional bandwidth of more than 157% with a compact size of 15 mm×12 mm. Simulated and measured results are discussed to validate the proposed antenna design with enhanced wide bandwidth performance.
This paper presents a comprehensive analysis of the roadway powering system for electric vehicles (EVs) and proposes a design from the perspective of power track design, integration, and powering control strategy, aiming to ensure the charging power and persistence, enhance the control flexibility, and reduce the construction cost. 1) A novel design scheme is first proposed to determine the length and number of turns for power tracks by investigating the power supply-and-demand and the loss. 2) A novel evaluation index, namely the magnetic distribution variance, is proposed to determine the gap between adjacent tracks, which can effectively produce evenly-distributed energy field, thus improving the dynamic charging performance for EVs. 3) A sectional powering control strategy is proposed to implement a cost-saving and flexible roadway powering system. Lastly, the simulated and experimental results show that the exemplified prototype can achieve the transmission power 50W over the distance of 200 mm, which verifies the proposed EV dynamic charging system with the salient advantages of the constant energization, flexible power control, and cost saving.
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