In this paper, a cross-slot-coupled dual-band circularly polarized (CP) hybrid dielectric resonator antenna (DRA) is presented. The design concept is based on using a cross-slot as both a feeding structure of the DRA and an effective radiator. Full wave simulation is used to verify the proposed design concept in this paper. A prototype antenna is designed, fabricated, and measured. Good agreement is obtained between the simulated and measured results.
This paper presents the development of an Ultra Wide Band (UWB) monopole antenna with dual band notch characteristics. Modified crown-square shaped fractal slots in the ground-plane are implemented to enhance the impedance bandwidth to around 58% as compared to conventional square monopole antenna without slots. Impedance bandwidth of the proposed antenna is approximately 114% with Voltage standing wave ratio (VSWR)<2. In addition to this, two omega-shaped (Ω) slots have been incorporated in the radiating patch to render band-notch characteristics centered at 5.5-GHz band assigned to IEEE802.11a and HIPERLAN/2 as well as X-band for satellite communication centered at 7.5-GHz band. Measured antenna gain is stable over the entire UWB region except at the notch bands. Radiation pattern of the antenna show that the proposed antenna exhibits nearly monopole like E plane radiation patterns and omni-directional H plane radiation patterns throughout the band. A fabricated prototype is developed with close agreement between simulated and measured results.
Target recognition through the processing of high-resolution radar images has been an active research area in past decades. In this paper, dictionary sets parameterized by the two-dimensional (2-D) location parameters of main high-energy scatterers are considered to recognize the candidate targets. For this purpose, the scatterer extraction and orientation estimation of radar image are firstly provided in this paper. Furthermore, the recognition method based on the parameterized dictionary sets is subsequently proposed. Different from the existed recognition methods, only the sampled images at the 2-D location parameters of main high-energy scatterers are used in the proposed method. Consequently, the noise or clutter outside the sampling locations can be filtered, which results in more robust performance. Moreover, the 2-D location parameters are proportional to the geometrical structure, and the proposed method is adaptive to the scale variation of the target images. Simulated results are provided to demonstrate the proposed method.
A novel and simple dual-band dual-sense circularly polarized (CP) metal-strip antenna is proposed. The antenna fed by a coplanar waveguide (CPW) with the advantages of uniplanar geometry and easier fabrication consists of a square slot and two split-ring elements. By appropriately introducing dual split-ring elements, the proposed dual-band CP design can easily be achieved. The two resonant frequencies are controlled by the size of the two split-ring elements. The proposed antenna prototype is fabricated and measured. Experimental results show that good CP radiation performances are obtained at both resonant frequencies. The proposed antenna has an impedance bandwidth (|S11|≤-10 dB) of 63.3% (2.0~3.9 GHz), and the dual band circular polarization with left hand circular polarization (LHCP) at 2.2 GHz and the right hand circular polarization (RHCP) at 3.8 GHz are obtained. Also, the 3-dB axial ratio bandwidths are about 220 and 190 MHz at the lower and upper band, respectively.
Electromagnetic band gap (EBG) structures are usually realized by periodic arrangement of dielectric materials. These periodic structures can help in the reduction of mutual coupling in array antennas. In this paper a new arrangement of EBG structures is presented for reducing mutual coupling between patch antenna MIMO arrays. The patch antennas operate at 5.35 GHz which is defined for wireless application. Here 2×5 EBG structures are used to reduce mutual coupling more than 20 dB. The total size of the antenna is 36 mm×68 mm×1.6 mm. So it is more compact in than pervious research. Experimental results of return loss and antenna pattern have been presented for 5.4 GHz and compared with HFSS simulation results. Also the EBG structures have been designed with numerical modeling and dispersion diagram. New EBG model is compared with conventional EBG model, and equivalent circuit model is given for new structure.
For the measurement of microwave device in high-power, traditional methods are inefficient, inaccurate and not on-line real-time measurement. A new type of high-power microwave impedance tuner (26.5 GHz~40 GHz) based on load-pull technique and a corresponding rapid calibration method based on curve fitting are proposed. A new structure using increased width rectangular waveguide slotted in the center is adopted as the main transmission line. In order to prevent the leak of electromagnetic waves transferring in rectangular waveguide, two choke grooves are added in upper cover plate of the waveguide cavity. The results (standing wave ratio range of 1.02~10.98, insertion loss of 0.063 dB at minimum standing wave ratio) show by practical measurement that this structure and method are feasible. The device can meet the requirement of design, and the new method has less time for calibration.
This paper presents a novel power divider with filtering responses. By using quarter-wavelength resonators with a novel feeding structure, both power division and bandpass responses are obtained, and compact size is realized. Discriminating coupling is utilized to suppress the third harmonic to obtain wide stopband. The isolation resistor is connected at two ends of the input feed line, and good isolation is obtained. Two transmission zeros are generated at two edges of the passband, resulting in high selectivity. For demonstration, a filtering power divider is implemented. Comparisons of the measured and simulated results are presented to verify the theoretical predications.
A multimode collocated microstrip patch antenna with reduced mutual coupling is proposed in this paper. The antenna is designed to achieve polarization and pattern diversity for use in multiple-input-multiple-output (MIMO) terminals. The four-port antenna resonates at 2.45 GHz and have total dimension of 1.03λ with reduced mutual coupling (< -20 dB) between its ports. It consists of a simple square patch and a square ring antenna, with a novel square ring slot defected ground structure (DGS). Square ring slot on ground improves isolation by 7 dB by reducing surface waves in both E and H planes. With defected ground structure (DGS), coupling between patch and ring antennas is about -25 dB and correlation factor is less than 0.1. Pattern diversity, mutual coupling and correlation coefficient between signals for a four-port antenna fabricated using FR4 substrate is discussed in this paper.
In this paper, a novel folded metal-plate monopole antenna is presented for indoor digital television (DTV) signal coverage in the 454-1300 MHz band. The proposed antenna consists of a folded metal-plate with two asymmetrical bevels and a shorted pin connecting the metal-plate with a ground plane. The folded structure extends the lower frequency band and reduces the height of the antenna for better application to DTV. Experiment results show that the antenna achieves a bandwidth for |S11| < -10 dB ranging from 454 MHz to 1300 MHz and shows stable radiation patterns in three coordinate planes.
A novel compact and multiband dipole antenna with a planar fractal-inspired configuration is presented. Several series capacitances and a parasitic element are employed as loading. Results show that the loading improves the impedance matching and enables the proposed antenna to radiate at multiple frequency bands. In addition, the proposed loaded dipole antenna offers a high degree of miniaturization in comparing with the unloaded host dipole antenna. The simulated |S11| response of the proposed loaded dipole antenna shows five distinct resonant bands with the center resonant frequencies of 1.52 GHz, 3.62 GHz, 4.6 GHz, 6.9 GHz, and 9.43 GHz. A fabricated prototype has compact dimensions of the 37 mm × 14 mm × 1.6 mm, and exhibits good agreement between the measured and simulated S-parameters.
A novel Quasi-Yagi antenna with low radar cross section (RCS) is proposed in this paper. By using arrow-shaped Koch dipoles as the driver and director and cutting the ground of the antenna, the RCS can be reduced in the operating band of 5 GHz-8 GHz when the incident wave is perpendicular to the antenna plane. Wideband radar absorbing material (WRAM) with frequency selective surface (FSS) is devised to replace the metallic reflect plate of the antenna to reduce the RCS in the maximum radiation direction. The average RCS reduction of the antenna in the frequency band of 3 GHz-12 GHz is 8.0 dB. The simulated and measured results show that there is a considerable RCS reduction of the Quasi-Yagi antenna with WRAM, and the radiation performance is preserved at the same time.
In this paper, a vehicular antenna design scheme considering the vehicular body effects is proposed. A wire antenna for GPS and LTE is implemented on the plastic plate, then it is mounted on the front glass. The outputs are commonly used to share the feed. It is necessary for GPS to increase the right hand circularly polarization (RHCP) gain near the zenith and to reduce the axis ratio while for LTE to increase the horizontal and vertical polarization (HP and VP) gain in the horizontal plane. Also for LTE, multiband characteristics are required. In order to achieve the specified performance, the antenna shape is optimized by Parato genetic algorithm (PGA). When the antenna is mounted on the body, the performance is seriously changed. To evaluate performance of the antenna mounted on the body with a complex shape, a commercial electromagnetic simulator (Ansoft HFSS) is used. To apply electromagnetic results output by HFSS to PGA algorithm operating on the MATLAB, MATLAB to HFSS linking program via Visual BASIC (VB) script was used. It is difficult to carry out the electromagnetic analysis with the whole body because of limitations of the calculating load and memory size. To overcome the limitation, we consider only a predominant part where it has an influence on the performance. It is presented that degradations caused by the body are improved through a series of optimization stages. The simulation results obtained clearly show that it is well optimized at 1.575 for GPS and 766.5 MHz and 2.135 GHz for LTE, respectively.
A novel compact wideband differential bandpass filter with wideband common mode suppression using a Marchand balun is presented in this paper. Open/shorted coupled lines and stubs are used to improve the selectivity for the differential mode and common mode suppression. The demonstrated filter with a compact size of 50 mm × 30 mm exhibits a fractional bandwidth of 53% centered at 3.0 GHz and 13 dB common-mode suppression from 0 to 9 GHz. The theoretical and measured results agree well with each other and show good in-band performances.
In this paper, a compact band-stop filter with a wideband and high-selectivity performance is proposed and analyzed. This band-stop filter includes two parallel-coupled lines of different electrical lengths and two open-circuit stubs. A lossless transmission line model is used to obtain the filter design parameters. In order to verify this new filter circuit structure and its corresponding design theory, five groups of numerical examples are demonstrated. Finally, a practical band-stop filter with a 3-dB cutoff frequency bandwidth of 58.2% centered at 0.94 GHz has been designed, simulated and measured. The measured results show a good agreement with the simulated responses.
The method of a T-shaped antenna loading T-shaped slots for multiple band operation is presented in this paper. Inspired by the fractal antenna, the proposed method is intended to be used for designing multiple band antennas. Through loading T-shaped slots in the terminals of a T-shaped antenna, dual or triple operating bands can be achieved. In order to validate the feasibility of this method, this type of antenna is designed and simulated. The antennas are respectively fed by two different feeding transmission lines (microstrip transmission line and coplanar waveguide (CPW) transmission line) for the purpose of identifying the method that can be commonly used. The parametric analysis in detail has been given to explain the effects of the key parameter variations. For WLAN and WiMAX applications, the antennas are fabricated and measured. Both simulated and measured results are presented to demonstrate the feasibility of these designs.
This paper presents a general method to isolate the compact dual-element antenna for mobile radio communications. The basic concept to cancel the coupling current is proposed, and two individual implemental solutions, connecting the transmission lines and the antenna elements, are illustrated respectively. Two examples targeted at 2.4 GHz ISM band have been implemented for the practical cellular phone environment. The antennas are well designed followed by the proposed principle. The result shows that the magnitude of S21 between two ports can be no higher than -10 dB in the interested bandwidth after applying the proposed methods. Good agreements are observed between measurements and simulations. It is suitable for application to mobile terminals due to its relatively low profile and good MIMO performance.
Maintaining mutual coupling suppressing structure as simple as possible is becoming attractive in the electromagnetic and antenna community. A novel parasitic patch structure that can reduce mutual coupling between cavity-backed slot antenna elements is proposed and studied. The structure consists of only a simple rectangular patch inserted between the antenna elements and it is therefore low cost and straightforward to fabricate. The proposed structure can not only suppress the surface-mode propagation and reduce mutual coupling between slot antennas, but also improve radiation patterns. The features include small occupied area and very simple structure.
An orthogonal beam-forming network (BFN) is proposed for 4G pattern-diversity applications. Different from the traditional Butler beam-forming networks with 2N orthogonal beams, the orthogonal BFN, composed of three 180° hybrids and a 90° phase shifter, provides three orthogonal beams. Design procedure of the orthogonal BFN based on the factorization of its transmission matrix is derived. Moreover, in order to implement the proposed orthogonal BFN with low insertion loss, a rat-race has been used to realize unequal power distribution between its two output ports. The measured scattering parameters of the orthogonal BFN are compared with the analytical and the simulated scattering parameters, validating the expected behavior. In addition, by varying the output power ratio of the non-equi-amplitude 180° hybrid, the performance of the orthogonal BFN is improved when the proposed orthogonal BFN is used in an antenna array.
A compact microstrip-fed antenna with dual band-notched characteristics for ultrawideband (UWB) applications is presented. By introducing two open-ended inverted L-shaped slots, two sharp notches are achieved at frequencies of 3.16-3.70 GHz and 5.10-5.95 GHz for VSWR < 2. A rectangular slot in the ground plane can improve the impedance bandwidth of the proposed antenna. The prototype occupies a compact area of 22 × 26 mm2. The measurement results indicate that the proposed antenna can reject the interference with coexisting worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) systems. The proposed antenna shows relatively omnidirectional radiation patterns in the pass band.
This study proposes a differential-fed microstrip antenna, which is characterized with an ultra-wideband of 120% (3-12 GHz), improved radiation patterns, stable gains, and compact size. Two symmetrical trapezoid shaped slots and four triangle-cut corners on the ground are used to improve the impedance matching over the UWB frequency band. To clarify the improved radiation characteristics, the simulated radiation patterns of the proposed antenna are compared with the conventional single-ended feed UWB antennas. The measured results show that, in the entire frequency band, the designed antenna exhibits a stable radiation patterns and the gain variation is less than 2 dB. Furthermore, the polarization purity are increased compared with the conventional ones, especially in the high frequency band.