A novel super compact electromagnetic metamaterial transmission line (EM-MTM TL) is proposed in this paper by using the structure of symmetric double spiral lines (SDSLs). The investigation results indicate that the proposed EM-MTM TL not only has controllable resonant frequency, but also has very compact size, and the circuit area is only 8.8 mm×7.2 mm (equal to λ0/32.16×λ0/39.31, where λ0 is the free space wavelength at the resonant frequency) without the feed lines. Using the proposed structure, a 3-dB branch-line coupler and a 0-dB crossover operated at 0.86 GHz have been designed, fabricated and measured; the measured and simulated results are in good agreement. The two microwave devices realize 84.8% and 85.7% size reduction, respectively. Then, a compact Butler matrix is obtained by optimizing the combination of the branch-line couplers, 0 dB crossovers and 45-degree phase shifters. The measured and simulated results of the proposed Butler matrix agree well, showing that the proposed device operates at 0.86 GHz with very good electromagnetic performances. Moreover, the circuit area of the proposed Butler matrix is 109.0 mm×89.3 mm, which realizes at least 80.9% size reduction in comparison with the conventional one (whose circuit area is at least 226.2 mm×226.2 mm), and the miniaturization is considerable. Besides, these designed microwave devices, without any lumped elements, bonding wires, defected ground structure (DGS), and via-holes, are more suitable for modern wireless communication systems.
A one-dimensional, dual frequency, active retrodirective array is proposed for wireless power transfer applications. Microstrip circular patch antennas with four shorting pins are used as array elements to suppress surface waves. The proposed design eliminates undesired coupling between array elements due to surface waves present in conventional microstrip antenna arrays in order to improve array performance. The antenna array uses circularly polarized microstrip elements with higher gain than conventional microstrip antennas. The proposed retrodirective array operates at 2.4GHz for the interrogating signal and 5.8GHz for the retransmitted signal, using up-converting mixers. The beam scanning inherent in retrodirective arrays ensures a constant power level available to the charging devices, regardless of their location within an angular sector over which retrodirectivity is achieved. A two-element experimental prototype provided uniform power density within a 60° angular sector. The Design procedure, simulation results and experimental measurements are presented.
A novel dual-band unidirectional circularly polarized (CP) antenna fed by coplanar waveguide (CPW) for wireless applications is proposed. The antenna configuration consists of a ring-shaped ground, an F-shaped central strip, and a spherical cap reflector. The longer and shorter branches of the F-shaped central strip help to produce radiant waves at lower and higher frequencies. The CP characteristics are achieved through adding two solid arcs and a grounded tuning stub. Both simulated and measured results are given and analyzed. Measurement results show a 10 dB return loss with a bandwidth of 56% (2.15 GHz-3.83 GHz) at 2.45 GHz (ISM), and a bandwidth of 42.6% (4.67 GHz-7.2 GHz) at 5.8 GHz (HiperLAN), a 3 dB axial ratio bandwidth of 15.1% (2.25 GHz-2.62 GHz), 4.1% (5.67 GHz-5.91 GHz). The maximum gain within the two CP bands are 8.7 dBic and 10.2 dBic, respectively.
In this paper, properties of three types of Circular Polarization Selective Surface (CPSS) cells including Pierrot, Morin, and Tilston, for using in dual circular polarization reflectarray antenna design are investigated. First they are designed for a center frequency about 10 GHz, and circular polarization properties including Reflection Loss, Transmission Loss, Reflected Axial Ratio, and Transmitted Axial Ratio are calculated and presented. Finally, reflection phase curves are presented, and the comparison between simulated properties is accomplished. Simulations show that Tilston cell is more optimum in dual circular polarization reflectarray antennasr
In this paper, we propose novel omnidirectional UWB printed monopole antenna for in-body microwave imaging applications. The proposed antenna consists of a square radiating patch, a microstrip feed line and a ground plane with pair of rotated T-shaped slots and another T-shaped slot that placed in between of two slots. The designed antenna provides a wide usable fractional bandwidth of more than 136.5% (2.96-15.8 GHz). This antenna has the advantages of wide bandwidth, compact size, low cost, good omnidirectional radiation patterns, and acceptable time domain behavior for using in In-Body microwave applications. The maximum measured gain for the fabricated antenna is around 6.1 dBi with an average efficiency above 89% throughout the bandwidth.
A low-power on-off-keying impulse-radio (IR) ultra-wideband (UWB) pulse generator (PG) intended for wireless-powered IR-UWB radio applications is presented. The proposed PG has high flexibility, the center frequency, output power and pulse-width (PW) are controllable depending on channel conditions and data rates. Qualitative frequency-domain and transient analyses are presented. A new figure-of-merit (FoM) is proposed such that a more precise comparison between different PGs can be made. The PG is successfully implemented in a TSMC 90 nm CMOS process, measurements show the energy consumption and FoM to be 2.8-7.5 pJ/pulse and 1.6-2.6% respectively. The output swing and PW are 277-329 mVp-p and 509-1088 ps respectively. The core area is 0.092 mm2.
The Radio Frequency IDentification (RFID) Low Frequency (LF) serial loops structure is proposed to improve TAGs detection when a TAG coil-antenna rotates by any angle, due to the tagged pebble moving. The detection zones of two types of TAGs (the token and glass TAG) and two types of reader coils, in function of the TAG size, TAG orientation and shape of the reader coils are tested. The effect of the proposed multi-coil inductively coupled is confirmed by measurement using a commercial LF RFID system.
High-Altitude Platform (HAP) is a promising technique for providing wireless communications services with improved performance compared to terrestrial and satellite systems. A critical issue in this emerging system is the difficulty of providing user location information through two-dimensional direction-of-arrival (2D-DOA) estimation due to the high computational complexity and the large covered area. Therefore, in this paper, an efficient technique has been proposed to determine user location through 2D-DOA with a reduced processing time. The proposed technique estimates the 2D-DOA in two stages. In the first stage, a low-resolution 2D-DOA estimation technique will be utilized, such as Bartlett algorithm performed on a low-resolution distance grid, then a suitable threshold is applied on the normalized Bartlett 2D-DOA spectrum to define ground windows for the next high-resolution 2D-DOA stage. The second stage is carried out by a high-resolution technique such as MUSIC algorithm and will be performed on a high-resolution distance grid. Two scenarios are examined for the proposed technique to investigate the reduction in processing time compared with the conventional 2D-DOA MUSIC algorithm without windowing. Simulation results show that at 40 meters resolution, the required processing time is only 20% of the conventional MUSIC algorithm and can be further reduced to 4% at resolution of 100 meters at the same array size. In addition, the proposed technique can be applied to any other efficient low-complexity 2D-DOA algorithms.
This paper presents a novel design of dual polarized space-fed antenna arrays with broad bandwidth and high isolation between two orthogonal ports. The dual polarized space-fed antenna arrays are designed with bottom radiating element electromagnetically coupled to two orthogonal open microstrip lines and top parasitic elements excited by the radiation from bottom radiating element, without any feed network for array elements excitation. Two space-fed antenna arrays with 7 and 19 parasitic elements, respectively, have been designed for 5.8 GHz frequency band and their performances are analyzed. The dual polarized space-fed array with 19 parasitic elements has been fabricated, and its performance is measured. The measured impedance bandwidth is 10.7%, isolation ≥32 dB between two orthogonal ports over entire bandwidth, maximum gain of 17.8 dBi and cross-polar levels ≤-29 dB.
This paper presents a dual-band impedance transformer for real source and load impedances that is capable of providing matching at two arbitrary frequencies. There are two possible configurations of the proposed technique, and both the configurations are simple and possess flexibility to cater to wide range of impedance environments. A very useful feature of the design is its inherent ability to provide DC isolation. A prototype, which works at 1 GHz and 2 GHz, fabricated using Roger's RO4350B laminate validates the proposed design with a good match between theoretical and experimental results. In addition, a dual-band T-junction power divider is reported to demonstrate the usefulness of the proposed impedance transformer.
The substrate integrated non-radiative dielectric (SINRD) guide presents a rather complicated process of design and implementation because of multiple interrelated design parameters involved in the definition of structures. In this work, the size of SINRD guide is halved by using a perfect electrical conductor (PEC) image plane. Consequently, the number of modes in the resulting image SINRD (iSINRD) guide is equally reduced since all even modes including the LSE10 mode are suppressed. Furthermore, a simple yet accurate design method is proposed that takes into account many parameters involved in the design of an SINRD guide, especially dimensions of perforation and dispersion effects. Three iSINRD prototypes are fabricated to test the proposed method over the W-band frequency range. Two of the prototypes are based on Alumina substrate with different perforation profiles, and both exhibit insertion loss around 1 dB while the return loss is around 16 dB. The third is based on RO6002 substrate and exhibits an insertion loss of around 3 dB and a return loss of around 14 dB. To test the leakage loss caused by periodic gaps in the PEC wall, two iSINRD lines with one and three gaps were fabricated. The insertion and return losses of the former case are respectively 1.2 dB and 17 dB compared to 2.5 dB and 18 dB of the latter case.
In this paper, a novel microstrip antenna array with reduced radar cross-section (RCS) in grazing angle is proposed and studied. We define that the grazing angle θ of radar incident wave ranges from 80° to 90°. Under the condition that the incident wave is in grazing angle, a microstrip antenna designed by the techniques of miniaturization and ground-cut slots is given firstly. Compared with a traditional rectangle microstrip antenna, the RCS peaks of the proposed antenna are efficiently controlled over the frequency range of 4~16 GHz. Based on the design above, the proposed antenna is chosen as an element to design a 2×2 antenna array. Analysis and optimization of the arrangement of the array is made to achieve more RCS reduction. The measured results of radiation performance accord with the simulated ones, which indicate that the proposed method is feasible.
In this paper, a compact asymmetric coplanar strip (ACS)-fed printed monopole dual-band antenna for 2.4 GHz bluetooth, 5.2/5.8 GHz wireless local area network (WLAN) and 3.5/5.5 GHz worldwide interoperability for microwave access (WiMAX) applications is presented and investigated experimentally. The proposed antenna is composed of a ACS-fed monopole, an arc-shaped strip and an omega-shaped strip, which occupies a compact size of 18 x 22 mm2 including the ground plane. By properly selecting the positions and lengths of these strips, dual frequency operation with wide impedance bandwidth characterstics can be achieved. The proposed antenna has been validated experimentally and found to have nearly onmidirectional raiation patterns in the H-plane, nearly bi-directional behaviour in the E-plane and accepatable peak gain across operating bands.
A hybrid optimization method that synthesizes coupling matrices for cross-coupled microwave filters is presented. This method consists of a general solvopt algorithm and fmincon algorithm, respectively. To avoid divergence from the coupling matrix, two cost functions are built, where the first one is constructed from the eigenvalues of the coupling matrix and its principal sub-matrices, while another one is dependent on the determinant of the coupling matrix and one of its cofactors. The values of non-zero elements of the coupling matrix serve as the independent variables to minimize the cost functions by using solvopt and fmincon. Although the stochastic initial values are not sufficiently close to the global optimum, the hybrid optimization procedure is still robust to find multiple coupling matrices to overcome the initial problem. It is significant that the suitable coupling matrix can be chosen from the multiple solutions to meet the given requirements in practice. For demonstrating the proposed hybrid optimization algorithm, some extraordinary prototype topologies are provided which validate the efficiency of the proposed synthesis procedure.
This paper introduces a new method for the design and realization of two monopulse antennas with circular polarization and unique phase center for two different frequency bands. The design uses compact sequential-rotation serially fed 2×2 patch array for each section of the monopulse antenna for X band at 8.2 GHz and a patch for S band at 2.25 GHz. The patches are placed on one layer, and the monopulse network and feeds are placed on different layers. The antennas use sequential rotation serial feeds with four and three probes for X band and S band, respectively. Also, the packaging and coupling effects are considered and compensated for this design. Finally, the antenna with a compact multi-layer structure is fabricated, and the simulation results are validated. The bandwidth of X band monopulse antenna system is at least 12.7% in simulation and 10% in fabrication, and it is about 10.2% and 10.3% for S band in simulation and fabrication, respectively. While the phase centers of both frequency bands are approximately at one point, the antenna system can be employed as a feed for reflectors.
This paper describes a monopole antenna with dual-band switchable circular polarization (CP) sense in WLAN and WiMAX bands. The proposed antenna consists of a rectangular patch fed by a microstrip line and a ground plane embedded with a T-shaped slot integrated with PIN diodes. The slotted ground is capable of exciting CP sense around 2.45 GHz for WLAN and around 3.4 GHz for WiMAX, respectively. Two triangular strips are added to improve impedance matching. The CP sense of the proposed antenna can be reconfigured between the right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) by switching the states of PIN diodes in the slot. The lower band 3-dB axial ratio (AR) bandwidth is 8.6%, and the upper band 3-dB AR bandwidth is 20.8%, in which the return loss is less than -10-dB. Simulated analysis and measured results are carried out and good agreement is achieved.
The aim of this work is to miniaturize a microstrip patch antenna resonating at 3 GHz. For this purpose, defected ground structure (DGS) has been employed to shift the resonance frequency of an initial microstrip antenna from 5.7 GHz to 3 GHz by disturbing the antenna's current distribution. The proposed DGS is incorporated in the ground plane under the patch antenna to improve its performances. Finally, a miniaturization up to 50%, with respect to the conventional microstrip antenna, is successfully accomplished. A prototype of the antenna was fabricated with the FR4 substrate and tested. The measurements results were in good agreement with simulation results.
A 12-element triangular-grid rectangular radial line helical array antenna is proposed and investigated. The major characteristic of this antenna is that its radiation elements are arranged in triangular-grid, which is helpful to reducing the number of elements demanded for a certain antenna aperture and grating lobe suppression capacity. The radiation element is optimized to facilitate the manufacture. The feed system with six different groups of output ports is designed to obtain equal-amplitude output using three kinds of probes. An antenna prototype with the center frequency of 2.856 GHz is simulated and measured. In the range of 2.75-2.95 GHz, the experimental result shows an antenna VSWR below 1.2, an antenna gain over 16.3 dB, and an aperture efficiency more than 80%. The field distributions of this antenna are analyzed through simulation, which prove its advantage of high power-handling capacity. Its ability to be used as a sub-array is also demonstrated by forming a 48-element array antenna.
A dual circularly polarized (CP) antenna is proposed in this paper. By employing suspended strip line to feed the patch at the two diagonal positions with 90º phase difference, single circular polarization is firstly obtained. Then dual circular polarization is excited by an L-shaped strip. The two feeding ports near the edges of the L-shaped strip arms provide the conversion between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). Measured results show that the proposed antenna has 10-dB return loss bandwidth of 30.5% (2.08-2.83 GHz), 10-dB isolation bandwidth of 15.7% (2.29-2.68 GHz), 3-dB axial ratio (AR) bandwidth of 25.1% (2.16-2.78 GHz).
Fire-resistant turbine oil is widely used in thermal power plant. As the service time increases, its lubrication and electrical characteristic degrade. This work proposes a mini NMR (nuclear magnetic resonance) sensor for assessing the degradation of the turbine oils used in real time and in vivo. Two magnetic discs with poles opposed were separated in a distance to generate a relative homogeneous static magnetic field between them. A solenoid coil was placed between the magnets as the RF coil. The dimensions of the sensor are 30 mm×30 mm×36 mm and the mass is 107 g. The T1 and T2eff of the turbine oils from two different power plants were measured. The results demonstrated that an increase of the service time of turbine oils clearly results in a decrease of T1 and T2eff. This method of monitoring degradation of turbine oils could lead to the use of NMR to assess the degradation level of turbine oils in service.