Integrating antennas into a load-bearing airframe structure has the potential for profound improvements in the capability of military and commercial airplanes, by allowing for substantially increased radiator and array size with reduced weight or drag penalties. Reducing the size of array elements can significantly improve the mechanical performance of the loadbearing antenna. The novel single element spiral slot cut in the broad-wall of a WR-90 rectangular waveguide proposed in this paper is smaller than a quarter of the operating wavelength (half of the size of a conventional rectangular slot). The small antenna element enables a slotted waveguide array to be realized without significantly degrading the mechanical performance in load bearing applications. The proposed spiral slot is compared with conventional rectangular slots and exhibits comparable performance in terms of total efficiency (representing coupling from waveguide mode to the slot) and peak realized gain. Total efficiency and peak realized gain of the spiral slot in travelling wave mode are significantly higher than those of a quarter wavelength rectangular slot element which has near zero radiation. The simulated results were validated by manufacturing the spiral slot placed on the broad-wall of a rectangular waveguide. Realized gain patterns of the spiral slot measured at the design frequency corroborate reasonably with the simulations.
A dual-polarized small base station antenna with a dielectric feeding structure is presented. The proposed antenna is composed of a micro-strip feed line board, eight metallic shorting plates, four dielectric feed substrates, four metallic radiators, a metallic cube, and a radome. A wide impedance bandwidth of 20% (2.45 to 3.0 GHz) is achieved. The proposed antenna has an isolation of greater than 50 dB over the operating bandwidth. Details of the proposed antenna design, and the simulated and measured results are presented and discussed.
In this paper, a numerical study of a new ultra wideband (UWB) dielectric resonator antenna (DRA) is presented. The proposed structure consists of two stacked dielectric resonators excited by rectangular patch and operated from 3 GHz to 11 GHz (an impedance bandwidth of 115%), covering the full UWB spectrum. The analysis is carried out using the Finite Difference Time Domain (FDTD) method and two commercial electromagnetic simulators. The numerical results are given and compared in terms of reflection coefficients, radiation pattern and gain. The computed FDTD results are in good agreement with those of simulations.
In this paper, the design, realization, and experimental validation of a battery-assisted radio frequency identification (RFID) tag featuring sensing and computation capabilities are presented. The sensor-augmented RFID tag comprises an ultra-low-power microcon-troller, temperature sensors, 3-axis accelerometer, non-volatile storage, and a new-generation I2C-RFID chip for communication with standard UHF EPCglobal Class-1 Generation-2 readers. A preliminary printed-circuit-board prototype, connected to a 3-V/225-mAh lithium battery, provides a lifetime up to approximately 3 years when sensing and RFID-based communication tasks are performed every 10 seconds. Moreover, the device exhibits indoor transmission ranges up to 22 m, 6 m, and 5 m when attached to foam, concrete, and wood respectively. The encouraging results achieved for an emulated application scenario demonstrate the suitability of the device to be adopted in contexts where temperature and acceleration sensing are required.
In this paper, we present an experimental verification of a novel QR-TLS algorithm. Two other algorithms for direction of arrival (DOA) estimation of multiple incident source signals called multiple signal classification (MUSIC) and estimation of signal parameters via rotational invariance techniques (ESPRIT) are implemented on a National Instruments (NI) PXI platform. The proposed method is based on subspace decomposition of a received data into a signal and a noise space using QR decomposition. The angle of the signal arrival information is extracted from the signal subspace by using the method of total least squares (TLS). The algorithms are implemented in LabView NI hardware. The experimental procedures are discussed in details which includes interfacing of the uniform linear array (ULA) of antennas with the NI-PXI platform, calibrating phase differences between the RF receivers, and selecting transmitter and receiver parameters, for determining the DOAs of the multiple incident source signals. The experimental results are shown for a single and two sources lying at arbitrary angles from the array reference to verify the successful real time implementation of the proposed and other DOA estimation algorithms.
A 132 GHz gyrotron, operating at fundamental harmonic, is designed for the 200 MHz DNP-NMR experiment. In this article, the design of high quality electron beam source is presented. 2.5 dimensional code EGUN and 3 dimensional code CST-Particle Studio are used in the design and optimization of electron gun. The design of electron beam source is performed for a band of magnetic field values at the emitter surface and cavity center which is necessary for the frequency tunabilty of 2-3 GHz needed in DNP/NMR experiments. The results confirm the axial and transverse velocity spreads around 1% and 2.2% and a pitch factor of 1.5. The parametric analyses are also performed for the various electrical parameters such as emitter voltage, anode voltage, emitter magnetic field, etc.
A novel loop-like monopole antenna with dual-band circular polarization (CP) for the reception of WiMAX and WLAN is designed and implemented in this paper. The antenna consists of a radiating patch which is composed of an annular-ring linked by a square ring over the corner and a ground plane with embedded rectangular slit. The broad impedance bandwidth is achieved based on a novel monopole structure which is the combination of two perturbed loops and the perturbation causes the generation of right-hand circular polarization (RHCP) at 3.52 GHz and left-hand circular polarization (LHCP) at 5.75 GHz. In addition, by embedding a rectangular slit on the ground, the impedance bandwidth can be greatly enhanced. The measured results show that the proposed monopole antenna has an impedance bandwidth of 3.65 GHz from 2.65 to 6.3 GHz, reaching the particularly broad bandwidth of 81.6%. Furthermore, the measured 3-dB axial ratio (AR) bandwidths are about 440 MHz at the lower band (3.52 GHz) and 220 MHz at the upper band (5.75 GHz). The radiation characteristics of the implemented antenna are also presented.
In this paper, we present a wideband planar Eshape textile antenna and study its performance numerically and experimentally. The textile material and radiation patch shape provide the antenna a wide working band (2.25 GHz-2.75 GHz). A digital human model is established to numerically analyze the affect of human body on antenna. Experiments are carried out to study the performance changes of antenna at different states which may be experienced in the potential applications. These states are antenna on human body, antenna getting bent, and antenna after getting wet. The simulated and measured results in free space and on human chest show good agreement with each other. From the study, it is also found that the textile antenna's performance does not get deteriorated at these states. Therefore, the wideband planar E-shaped textile antenna is suitable for body-centric wireless communications with high quality.
This paper presents a novel method to suppress the higher order harmonics in the microstrip patch antennas. A practical 0.75 GHz microstrip patch antenna is fed with a quarter-wave feedline designed by exploiting the dispersion properties of shunt-capacitor-loaded transmission-line metamaterials. It is shown that two higher order harmonic modes at 1.25 and 1.5 GHz are completely eliminated. In addition, there is about a one-fourth reduction in the length of the impedance matching quarter-wave feedline.
A novel shaped of printed monopole antenna with a koch fractal technique is presented in this paper. The ultra-wide bandwidth (UWB) antenna is composed of a modified ground plane with two independently elements as cross and Egyptian arc shapes to improve the antenna bandwidth. PIN diode is used to connect or disconnect the circular arc between two bands to switch frequencies from 500 to 2500 MHz and from 4 to 10 GHz. This implemented antenna effectively support personal communication system (PCS 1.85-1.99) GHz, universal mobile telecommunication system (UMTS 1.92-2.17) GHz, wireless local area network (WLAN), which usually operate in the 2.4 GHz (2.4-2.484 GHz) and 5.2/5.8 GHz (5.15-5.35 GHz/5.725-5.825 GHz) bands, mobile worldwide interoperability for microwave access and WiMAX, which operate in the range from 2.305 to 2.360 GHz, from 2.5 to 2.69 GHz and from 5.25 to 5.85 GHz bands. The properties of the antenna as reflection coefficient, efficiency, radiation patterns and gain are simulated and approved by the experimental results.
A super-wideband antenna based on a propeller shaped printed monopole with CPW feed is presented in this paper. The enhanced bandwidth is obtained by modifying the disk of a conventional circular disk monopole to resemble a propeller. This design produces an extremely wide impedance bandwidth from 3 to 35 GHz with an impedance bandwidth ratio of 11.6:1. The gain of the proposed antenna varies from 4 dBi to 5.2 dBi. The antenna has fairly stable radiation characteristics throughout its operating band. The developed prototype is fabricated and measured. Simulation and experimental results are in good agreement.
This paper presents a new directional coupler design, which can increase power capacity working with S band. The design concept is based on multi-stage coupled structure. Aim is to increase the size of coupling aperture by reducing the coupling degree of each stage structure. In view of this, multi-stage coupled structure theory is utilized to improve the directivity of directional coupler, coupling flatness and power capacity. According to the derivation of theory, it can be deduced that the sum of the coupling degree of single stage coupling structure is equal to the coupling degree of two-stage coupling directional coupler (TSCDC), and the directivity of TSCDC depends on the directivity of the first stage coupling structure. Then, rectangular waveguide two-stage coupled directional coupler is designed and fabricated. The measured results demonstrate full-band from 1.72 to 2.61 GHz with coupling flatness < 0.65 dB and the directivity > 26 dB.
The objective of the work is to design a dual frequency microstrip antenna for small frequency ratio applications. The proposed geometry comprised of suspended truncated circular microstrip antenna, with double U slot etched on the radiating element. The design parameters are radius of circular patch, width and length of slot, height of air gap. The proposed design of the antenna has enough freedom to control the dual design frequencies/frequency ratio by varying the above design parameters. FR4 substrate with dielectric constant 4.4 is chosen for design and fabrication. The dual design frequencies are 1.93 GHz and 2.17 GHz, covering the applications such as WCDMA, 3G mobile data terminals, and 4G LTE applications. The antenna is fed by a 50 Ω coaxial probe. The simulation of the antenna is performed using ANSOFT HFSS and analyzed for return loss, VSWR and radiation pattern. The antenna is fabricated and tested for impedance matching and radiation characteristics. The simulation and experimental results show that the antenna worked well at desired dual frequencies. The impedance matching is well at both frequencies (VSWR <2). Though, the measured radiation pattern is unidirectional in co-polarisation, nearly omnidirectional (butterfly) pattern is obtained in cross-polarisation and gain is about 5.54 dB at 1.93 GHz and 8.23 dB at 2.17 GHz. Also, the design is well suited for small frequency ratio dual frequency applications.
In this paper, a three-pole bandpass filter (BPF) using a new defected ground structure (DGS) is discussed. The proposed DGS is incorporated in the ground plane under the feed lines and the coupled lines of a bandpass filter to improve the performance of the filter in both passband and stopband. The banpass filter is designed with a center frequency of 1.8 GHz and a bandwidth of 270 MHz. The suppression of better than 20 dB was achieved for frequencies between 2.2 and 5 GHz. A prototype of BPF was fabricated and tested. Prototype measured data was in good agreement with simulation results.
A polarization reconfigurable spiral slot antenna with polarization states switched among left-hand circular polarization (LHCP), right-hand circular polarization (RHCP) and linear polarization (LP) is proposed in this paper. The antenna consists of a coplanar waveguide (CPW) input, a pair of reconfigurable CPW-to-slotline transitions, two separated same size single-arm spiral slot radiators, and four PIN diodes for reconfigurability. A good impedance match (VSWR≤2) for both linear and circular polarization is achieved from 2.1 to 2.9 GHz. The bandwidth for axial ratio AR≤3 dB for both RHCP and LHCP states ranges from 2.27 to 2.66 GHz (15%). The simulation and measurement results agree well and hence sustain the reconfigurability of the proposed design.
A passive millimeter-wave imager BHU-2D-U based on synthetic aperture interferometric radiometer (SAIR) technique has been developed by Beihang University. The imager is designed for detecting concealed weapons on human body and operated under the near-field condition of the antenna array, thus the conventional Fourier imaging theory does not apply. In this paper, an accurate numerical image reconstruction algorithm using regularization theory is proposed. By means of adding a prior information of desired brightness temperature image, the influences of measurement noise and focusing error on the reconstructed image have been reduced. Numerical simulations and experiments on BHU-2D-U have been performed to verify the superiorities of the proposed algorithm over the corrected Fourier method and the Moore-Penrose pseudo inverse method. The results demonstrate that the proposed method is an advantageous imaging algorithm for near-field millimeter-wave SAIR.
A broad-band transmission line spatial power combiner (SPC) is proposed in this paper, which uses a square coaxial (Squarax) transmission line (TL). This structure has some advantages over the traditional circular coaxial spatial power combiner, which have been described in this paper. Fin-Line to microstrip transitions are inserted into the Squarax TL, in order to allow an easy integration of Monolithic Microwave Integrated Circuit (MMIC) Solid State Power Amplifier (SSPA). The Squarax SPC geometry allows the feeding of a higher number of MMIC than in a Waveguide SPC, so that this structure ensures high power outputs and small sizes, together with theoretical DC frequency cut-off. In this work, the design and simulation of a passive 4-18 GHz Squarax SPC are reported.
In this paper, an ultra-wideband (UWB) patch antenna integrated with a dielectric resonator is proposed for cognitive radio applications. The patch antenna is fed by a coplanar waveguide (CPW) line, and it consists of a rectangular monopole having an elliptical base, and operates from 2.44 to 12 GHz, this UWB antenna is intended to collect the information. Moreover, the proposed structure integrates a narrow-band rectangular dielectric resonator antenna (RDRA) for operation, with very good isolation between the two ports (transmission coefficient S21 less than -20 dB). The RDRA provides a bandwidth from 5.23 GHz to 6.11 GHz. The electromagnetic analysis is carried out using tow commercial software tools. Furthermore, to validate the proposed concept, experimental measurements are also performed.
This paper presents an electrical model of aperture and mutually coupled three-elements cylindrical dielectric resonator antenna (CDRA) array designed for 802.11a system applications. In electrical model, each antenna component is represented by its equivalent RLC circuit. The advanced design system (ADS) software is used to build the electrical model and predict the behavior of return loss, while the antenna structure is simulated using CST microwave studio before fabrication. The first and last radiating elements of the proposed array are excited through the aperture slots while the middle element is excited through the mutual coupling of its neighboring elements. The slot length and inter-slot distance effects on bandwidth are comprehensively analyzed and presented. The maximum gain of the proposed array for 5.0 GHz band is about 10.8 dBi, and the achieved simulated (CST, ADS) and measured impedance bandwidths are 1.076 GHz, 1.0 GHz, and 1.2 GHz respectively. The proposed CDRA array antenna exhibits an enhancement of the gain (7.4%) and bandwidth (93.3%) as compared to a literature work with aperture slots. In this study, it is also observed that by using the mutual coupling instead of third slot to excite the middle CDRA, side lobe levels are also reduced significantly over the entire 5.0 GHz band.
A method to increase the bandwidth of a series-fed dipole pair (SDP) antenna by using a parasitic strip pair director is presented. A conventional SDP antenna consists of two dipole elements having different lengths and a ground reflector, which are serially connected with a transmission line. In the proposed antenna, a parasitic strip pair director is appended to the conventional SDP antenna. Initially, a conventional SDP antenna that operates in a frequency range of 1.7-2.7 GHz is designed by optimizing the lengths of the elements (two dipoles and ground reflector) and the distances between these elements. Subsequently, a parasitic director containing a pair of strips is placed near the top dipole element to improve the bandwidth and gain of the conventional SDP antenna. Then, the effects of the location and size of the director on the impedance bandwidth and realized gain are investigated. A prototype of the proposed antenna is fabricated on an FR4 substrate, and its performance is compared with that of the conventional SDP antenna. The experimental results show that the proposed antenna has an enhanced bandwidth of 1.63-2.97 GHz (58.26%) and an increased gain of 5.6-6.8 dBi.