In this paper, a bandstop to allpass reconfigurable filter technique is proposed in Single Pole Double Throw (SPDT) switch design. Proof of concept of the bandstop to allpass reconfigurable filter is presented. It is physically realized using transmission line and radial stub in 3.5 GHz band (3.4 to 3.6 GHz). The isolation, insertion loss and return loss of the SPDT switches are analyzed and to validate this technique the prototypes are fabricated using FR4 substrate with a thickness of 16 mm. A very good agreement is shown between the simulated and measured results. Using this technique, it is able to produce more than 30 dB isolation with minimum number of PIN diodes, thus reducing 42.7% of the total circuit size compared with conventional design. Besides, additional 22.9% of isolation bandwidth can be obtained with the use of radial stub compared with transmission line stub. The potential application of this SPDT switch is Time Division Duplex (TDD) switching for WiMAX and LTE communication system in the 3.5 GHz band.
This paper proposes a novel corner-fed Circular Polarization (CP) reader antenna for handheld Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) application. The CP mechanism is accomplished by a multi-bending feeding strip located at corner of a high dielectric constant (K = 60) ceramic substrate. By using the high dielectric substrate, the dimension of the proposed antenna can be effectively reduced to 27 × 27 × 4 mm3, which consists of a top radiating patch, an antenna ground plane, a coupling multi-bending feeding strip, and a SMA connector for RF input. The top radiating patch is printed on the top surface of the ceramic substrate and the antenna ground plane is formed on the opposite side. The central frequency of resonant band can be easily controlled by adjusting the size of the top radiating patch. By optimizing the coupling feeding mechanism, not only impedance matching can be achieved for bandwidth operation in Taiwan's UHF RFID band, but also two orthogonal field components with 90° phase difference for circular polarization are obtained. In addition, the proposed antenna is placed on an 80 × 80 × 0.8 mm3 FR4 system ground plane for reducing hand holding effect.
In this paper, a new Frequency-Reconfigurable Stacked Patch Microstrip Antenna (FRSPMA) with a new coupling method applied in an aperture-coupled technique controlled by the switching circuit is presented. This antenna uses a combination of aperture-coupled technique and stacked patch in order for the radiating elements to increase the bandwidth. Two shapes (Ishape and H-shape) and sizes of aperture slots are etched onto the ground with a purpose to couple the energy between feedline and stacked patch. One PIN diode switch is integrated in the feed network to control the length of the feedline. A variation of the feedline length controls the selected aperture slots to be active. The waves from the selected activated aperture slots will radiate to particular radiating patch (top or bottom patch) and achieve the frequency reconfigurability. When the switch is in ON mode, the antenna has a capability to configure its operating frequency at 2.6 GHz and at 3.5 GHz during the OFF mode. Besides that, the air gap is used to improve and avoid any coupling problem between the aperture slots and both of the two patches. Improper alignment between the aperture slots and patches will interfere waves radiating from aperture slots to the particular patch. In addition, the proposed antenna produces a high gain of more than 5 dB during ON or OFF modes respectively. The simulated results are compared with measured results.
An improved double ridged horn antenna (DRHA) is proposed in this paper. By adding the dielectric lens at the aperture of the horn, radiation pattern distortion arising in the high frequency band of conventional DRHA is improved, which leads to higher radiation gain. Meanwhile, ridge slot loading contributes to better impedance matching characteristic, broadening the impedance bandwidth efficiently. The improved antenna is fabricated and measured, with the measured results consist with the simulation perfectly, which proved the viability of the improvement.
In this paper a printed regular hexagonal slot antenna with a hexagonal stub fed by a coplanar waveguide line has been considered for ultra wide bandwidth. This antenna is then modified to obtain dual band rejection. The Wireless Local Area Network (WLAN) and Wireless Microwave Access (WiMAX) band rejections are realized by incorporating a C-shape slot within the exciting stub as well as a couple of Z-shape open circuit stubs symmetrically inserted at the edge of the slot. The length and width of the C-shape slot and Z-shape stub offer sufficient freedom for selecting and shifting the notch bands. Magnitude of S11, impedance, gain and radiation characteristics of them are studied and discussed here. From the measured results, it has been observed that the impedance bandwidth, defined by magnitude of S11 ≤ -10 dB, reaches a value of 8.18 GHz (2.96~11.14 GHz) except dual frequency stop bands of 3.28-3.7 GHz and 5.1-5.90 GHz. From the experimental results, it is observed that the radiation patterns are omnidirectional in the H-plane and dipole in nature in the E-plane. The antenna gain varies from 4.8 dB to 5.3 dB over the whole operating band excluding the notch bands. Surface current distributions are used to analyze the effects of the C-slot and Z-shape stub. Measured group delay has very small variation within the operating band except notch bands and hence the proposed antenna may be suitable for UWB applications.
Directional and switched-beam antennas in wireless sensor networks are becoming increasingly appealing due to the possibility to reduce transmission power and consequently extend sensor node lifetime. In this work a reconfigurable beam-steering antenna is proposed for Wireless Sensor Network applications in the ISM band (f=2.4-2.4835 GHz). The proposed radiating structure consists of a vertical half-wave dipole antenna and eight microstrip antennas composed of a rectangular two-element patch antenna array. These microstrip antennas have a directional radiation pattern in the azimuth plane with a HPBW of nearly 60 degrees. A control circuit consisting of a transmission line, RF-switches and a 4:16 multiplexer has been designed in order to dynamically switch among nine radiation patterns, eight directional and one omnidirectional. Simulations and experimental results, referred to a low-cost realization on a FR4 substrate with a thickness of 1.6 mm, demonstrate appreciable performance.
In this paper, a miniaturized wideband bandpass filter utilizing a square ring resonator and loaded open-stubs is proposed. One pair of bent open-stubs characterized as perturbations is installed outside the diagonal corners of the ring, and another pair of loaded open-stubs is added inside the ring resonator. By stretching the perturbation stubs more than half-wavelength of the ring, three pairs of degenerated modes in a ring are split for wideband operation. The first two split modes form the dominant passband. Meanwhile, the loading effect introduced by the loaded open-stubs could move the third split mode into the dominant passband, at the same time, an additional transmission zero is generated by the loaded open-stub, which improves the skirt selectivity. Due to the applying of the perturbation stubs as long as more than half-wavelength, this kind of wideband microstrip ring resonator filter occupies a smaller size than those conventional ones that based on ring resonator. To verify the mechanism above, a wideband bandpass filter centered at 3.5 GHz is designed, implemented, and fabricated. Measured results of experimental circuit show good agreement with simulated responses.
For the coaxial outer corrugated resonator, dispersion equations of TE and TM modes are derived by the surface impedance theory, and the first order transmission line equations with mode coupling coefficients are deduced by means of the transmission line and coupling wave theory. According to them, resonant frequency, diffractive quality factor and field profile of geometry of the eigen-mode about the coaxial outer corrugated resonator can be calculated. The effect of outer slot depth, tooth width as well as asymptotic angle of outer conductor and slope angle of inner conductor on resonant frequency and quality factor can be researched. Results show that changes of the outer slot depth and tooth width slightly affect the field frequency and quality factor and that the changes of the asymptotic angle of outer conductor and slope angle of inner conductor almost do not affect field frequency, but greatly affect quality factor.
An ultra-wideband (UWB) bandpass filter (BPF) with application oriented triple notches and simultaneously suppressed stopband is proposed. Implementing complementary split ring resonator (CSRR) and novel complementary meandered folded split ring resonators (CMFSRR) shaped defected ground structures (DGS) in the ground of proposed structure generates the triple notch in the UWB passband. The notch positions are functions of CSRR/CMFSRR profile dimensions. Stopband is suppressed using the dual attenuation poles generated by the double equilateral-U (DEU) shaped DGS. An approximate lumped equivalent circuit model of the proposed filter is presented. Measured results obtained are in good agreement with the equivalent circuit model and full wave electromagnetic (EM) simulation. The filter is small in size with an overall area of 26.06 mm × 11 mm.
A compact multiple band-notch ultra-wide band (UWB) band-pass filter (BPF) with surface area of 18 x 12 mm2 is introduced in this article. The proposed filter is a combination of novel symmetrically tapered elliptic rings (STER) and contiguous split ring resonators (SRR), with stepped impedance resonator (SIR) structure to realize the multi-band notch UWB pass band characteristics. In the proposed structure, band-notches are generated for interfering microwave bands such as, WiMAX, WLAN and X-band applications. These notches are achieved by optimizing structural parameters of SRR sections. The proposed filter is fabricated on RT/Duroid 5880 substrate with εr = 2.2 and thickness of 0.787 mm. The fabricated prototype is measured and a good agreement between simulated and measured results ensures suitability of the proposed filter for UWB applications.
In this paper, design and analysis of omnidirectional single feed circularly polarized, wide axial ratio beamwidth resonant sidefed bifilar helix antennas that do not require a ground plane is presented. The simulation and measurement results show that side-fed helix antennas of various radii gives near perfect circular polarization (CP) almost over the whole sphere except at and around nulls, at a certain turn angle by properly proportioning the area of loop (A) with the product of pitch (p) and radianlength (l) of helix. Helix antennas with smaller radii give axial ratio (AR) close to one at higher values of turn angle with lower value of resonant input impedances but CP is less sensitive to inaccuracy in turn angle. However helix antennas with larger radii results in AR close to one at lower values of turn angle and provides better values of input resistance but its AR is more sensitive to variations in turn angle. The simulated results show that the polarization solid angle beamwidth (for AR ≤ -3 dB) varies from 3.96π to 4π steradian. The gain and 3dB beamwidth of the antennas are 2dBi and 90° respectively. The polarization bandwidth varies from 34% to 65%. The simulated results are verified by experimental measurements.
This work presents results for the path loss due to foliage at 2.4 GHz using RF equipment and XBee-PRO ZB S2B transceiver modules in Agricultural fields (Corn, Paddy and Groundnut) and Gardens (Coconut garden with green grass, open lawn with dry green grass and wet green grass) targeting short-range, near ground RF propagation measurements for planning and deployment of Wireless Sensor Communications for precise agriculture and plantation management applications. Path Loss (PL), Path Loss Exponent (PLE) and corresponding Root Mean Square Error (RMSE) values were deduced from the measured RSS from various positions in these environments. Empirical foliage loss prediction models such as COST 235, Early ITU Vegetation and Weissberger models were compared with the experimental results.
A novel dual-broadband circularly polarized folded slot antenna with single-feed is presented. The proposed antenna consists of two folded annular slots. By adjusting the asymmetric widths of the two slots, circularly polarized radiation can be achieved in two different bands. By optimizing the parameters of the proposed antenna, two wide impedance bandwidths of 35.0% (1.91-2.72 GHz) and 46.5% (4.36-7.00 GHz) can be obtained, and two axial ratio bandwidths are 2.36-2.56 GHz and 5.68-6.04 GHz, respectively. The antenna with simple structure is fabricated and measured. Good agreement between the simulated and measured results is also achieved.
A novel cascade microstrip filter with mixed electric and magnetic coupling is proposed and examined. For the first time, we designed a novel multilayer configuration resonator with a compact size. Compared with conventional open-loop filter, the size decreased 75%. First, using novel multilayer configuration resonator instead of monolayer configuration resonator, the size decrease about 45%. Meanwhile, two microstrip patches can be served as inner coupling capacitor, which create and strengthen electric field. Owing to this inner coupling, the size of filter can be further reduced. What's more, with a section of high characteristic impedance transmission line connected to the ground though a via-hole, it can be served as coupling inductor and create main magnetic filed, base on this structure mixed EM coupling is realized, and can generate additional transmission zero. That's means adopt low-order filter can achieve same characteristic as high-order filter. Based on the above solutions, the filter size can be sharply decreased to 12.5 mm×7.7 mm (i.e.,0.05λg×0.033λg). Furthermore, advantages of using this type filter are not only low insert loss, but also increased attenuation out-of-band with controllable transmission zeros.
Recent advances in satellite communication technologies in the tropical regions have led to significant increase in the demand for services and applications that require high channel quality for fixed and mobile satellite terminals. Due to lack of reliable investigations regarding accurate performance evaluation, experiments, and analysis on the satellite communication link in tropical regions under atmospheric impairments for both scenarios, accurate signal quality performance analysis is necessary. This paper presents the link characteristics observations and performance analysis with propagation measurements done in tropical region to provide an accurate database regarding rain attenuation in the tropics for fixed and mobile scenarios. The paper also presents a newly developed extension attached to the measurements setup for improved packet error rate (PER) performance evaluation related to the degradations occur in channel quality for different types of impairments (rain, mobility, and physical obstacles) for 4 modulation schemes, namely QPSK, 8-PSK, 16-QAM and 32-QAM. The results show that the rain impairments at Ku band cause up to 12.5 dB and 23 dB at 77.5° and 40.1° elevation angles respectively in two tropical regions inside Malaysia for fixed scenario with a significant increase in PER at higher M-ary modulation schemes. For mobile scenario, the PER appeared at higher M-ary scheme due to the lower signal power degradation in which, in turn, exceeded 1 dB when the vehicle speed exceed 100 km/hr at clear sky. The obstacles at the satellite communication link are shown to have significant effect on the power and PER received by satellite terminal especially at higher M-ary modulation schemes.
In this paper, two staggered array configurations are presented for enhancing size and radiation properties of wideband phased array systems. The proposed arrays are obtained either by rotating each element 45° or by inserting additional rows in the middle which are shifted by half the distance between elements. These two configurations allow for a smaller distance between array elements (29% less), while the actual distance between elements in the diagonal direction is kept the same. Reducing the distance between elements results in eliminating/reducing the grating lobes in a wider frequency range, which improves the array usable bandwidth. In addition, this proposed array produces better gain and maximum steering angle.
In this paper, the design of an array of wideband combined antenna elements is presented. A TEM horn antenna is combined with magnetic dipoles to obtain a wideband element with a bandwidth from 180 MHz to 30 GHz. The element is then miniaturized in order to be placed in a two by two array, and then the optimized values of the horizontal and vertical spacings are calculated. To enhance the array bandwidth, a lens is placed in front of each element. This leads to an increase in the bandwidth from 0.2 to 10 GHz while no grating lobes appear over the bandwidth. The combined element is fabricated and the simulation results are verified by the measured data. Furthermore, simulation results for the return loss, radiation patterns and antenna gain for the 2 × 2 array are presented.
This paper proposes miniature radio frequency identification (RFID) tag antenna designed to operate on metallic objects, in the UHF frequency range (915 MHz), without significantly degrading its read range. The antenna structure is composed of two parts: Part 1 comprises two square patches electrically connected to the ground plane through vias while Part 2 is an unconnected inter-layer consisting of two square complementary split ring resonators to allow for capacitive reactance increase. Consequently, its self-resonant frequency will shift towards low frequency, which theoretically allows shrinking RFID tag antenna into smaller size. The antenna was simulated and measured to verify its conjugate matching with chip impedance. The results of experimental tests show that the proposed RFID tag offers a maximum read range of 0.82 m when placed on a metallic object. The tag's overall size is 36.7×18.1×3.2 mm3. Both simulation and measurement results are provided to validate the design.
Two improved circularly polarized microstrip planar antennas operating in 5 GHz-6 GHz are proposed in this paper. The Swastika slot and a circular feeding line are introduced into Ant.2 which exhibits wide impedance bandwidth and AR bandwidth during simulation and measurement than a basic truncated edge CP microstrip antenna. In further studies, a center circular slot is introduced into Ant.3, and the experimental results show a wider impedance bandwidth and AR bandwidth with high gain.
A miniaturized triple-band branch-line coupler based on the simplified dual-composite right/left-handed transmission line (S-D-CRLH-TL) is proposed in this paper. The electromagnetic characteristics of S-D-CRLH-TL are analyzed by the simulator and equivalent circuit model, and the results prove that there are three frequencies with phase of -90° in the passbands; this characteristic can be applied in designing triple-band quadrature microwave components. The proposed branch-line coupler is fabricated and measured, the measured and simulated results are in good agreement with each other, showing that the triple-band operating at 3.06 GHz, 4.00 GHz and 5.54 GHz, the useful bandwidths are 2.97 GHz-3.16 GHz, 3.82 GHz-4.12 GHz and 5.48 GHz-5.67 GHz. In addition, compared with the conventional branch-line coupler, the whole size of the proposed one is 17 mm × 14.4 mm (0.173λ × 0.147λ) (λ is the wavelength in low frequency), it realizes a 73% size reduction. Moreover, compared with the triple-band branch-line coupler based on the double-Lorentz transmission line metamaterial, the proposed branch-line coupler is more effective in the situation, which is sensitive to phase-changing, as the sign of phase difference in the two outputs at the three frequency points keeps the same.
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