A wideband planar printed quasi-Yagi antenna with band-notched characteristic is presented. The proposed antenna consists of a microstrip-to-slotline transition structure, a gradient driver dipole, and two parasitic strips as directors. Meanwhile, the arms of the driver and two directors are rotated in a certain angle to improve gain. Employing a microstrip-to-slotline transition, a driver dipole and two parasitic strips, the proposed antenna achieves a wide bandwidth for ultra-wideband applications. The driver dipole is connected to the slotline with a coplanar stripline. To avoid the frequency interference from WLAN operating in the frequency band from 5.15 GHz to 5.825 GHz, an L-shape slot etched on the driver dipole element is adopted to achieve notched band ranging from 4.8 GHz to 6.1 GHz. The ground plane is symmetrically added two stubs to implement the lateral size reduction. The measured bandwidth, determined by the reflection coefficient less than -10 dB, covers from 3 GHz to 10.8 GHz. Better than 8.1 dB F/B ratio and the measured antenna gain varying between 4.7 and 8.3 dBi are also achieved in the operating bandwidth excepting in the notched band.
A new compact printed tri-band antenna for WLAN/WiMAX applications is presented. The proposed antenna consists of three inverted L-shaped strips whose geometry looks like a ``bent fork''. These strips are attached to the feed line through a horizontal strip. By optimizing the geometries of the inverted L-shaped strips, distinct resonant points can be effectively created for different frequency bands. The overall size of the proposed antenna is 18 x 33 mm2. Simulated and measured results show that the presented antenna can cover 2.5/3.5/5.5 WLAN and WIMAX bands with fairly stable radiation patterns. The antenna structure is simple, small, easily configurable and tuneable, and therefore suitable for practical applications.
An asymmetrical coupled-line circuit is proposed to design planar microstrip balun, which has the advantages of compact structure and complex source to complex load impedance transformation. This balun consists of three pairs of coupled lines and two tapped transmission-line stubs. Based on the traditional even-odd mode technique and ABCD parameters, closed-form mathematical equations for circuit electrical parameters are obtained. To demonstrate our design theory, a practical microstrip balun is designed, simulated and measured. The results show that the return loss is larger than 25 dB, the insertion loss S21 (S31) 3.15 dB (3.129 dB), and the output phase difference -180.22˚ at the operating frequency. Good agreements between the simulated and measured results verify our design theory.
In this letter, we present a diplexer implemented on a substrate integrated waveguide (SIW) with stepped impedance complementary S-shaped resonators (CSSRs). The variable frequency response of the stepped impedance concept adjoining SIW technology leads to improved device performance in terms of matching and isolation. Simulated and measured results show input matching, |S11|, better than -15 dB and output isolation, |S32|, below -30 dB for the frequency range 1-4 GHz. Furthermore, CSSRs offer a degree of freedom to design fundamental and higher order frequencies by selectively tuning the geometrical parameters. This simple yet effective approach eliminates the complexity to design diplexers based on complementary split ring resonator (CSRRs).
This paper presents a compact tri-band bandpass filter (BPF) with high selectivity. The proposed filter utilizes novel stub-loaded quarter-wavelength resonators and conventional uniform quarter-wavelength resonators. The latter is embedded in the former, and they are separated by a feed line. Due to these quarter-wavelength resonators, the total size is greatly reduced. Moreover, the passband frequencies can be controlled individually. To enhance its selectivity, source-load coupling is employed. For demonstration, an experimental filter is implemented. High skirt selectivity and suppression levels are observed in the measured results. The circuit area of the filter is 0.17λg×0.19λg, featuring compact size.
A Fabry-Perot interferometer sensor based on a fiber-tip bubble-structure micro-cavity is proposed, fabricated, and demonstrated for transverse load sensing. The micro-cavity is fabricated by using arc discharge at the end of a multimode fiber which has been processed with chemical etching. A transverse load sensitivity of 3.64 nm/N and a relative low temperature sensitivity of about 2 pm/°C are experimentally demonstrated for the proposed fiber-tip bubble-structure micro-cavity sensor. The sensor has the advantages of low-cost, ease of fabrication and compact size, which make it a promising candidate for transverse load sensing in harsh environments.
A new out-of-phase power divider (PD) without phase shifter at the output ports is proposed. Based on admittance matrix, a new topology of uniplanar power divider with symmetrical outputs is designed. Under conditions of good matching, perfect isolation, and 180° phase difference between two output ports, the corresponding design equations and synthesis procedures are derived and given with admittance matrix. To verify the design approach, an out-of-phase power divider operating at 2 GHz with equal power division ratio is designed, fabricated, and measured. Experimental results demonstrate that the input return loss is better than 32 dB, the insertion loss is less than 0.29 dB and the isolation is better than 33 dB. The amplitude imbalance between the output ports is 0.03 dB and the phase difference between the two output ports is 181.6 °at the operation frequency. Further more, 49.9% relative bandwidth of 15 dB return loss and 39.4% relative bandwidth of 20 dB port isolation are achieved.
The traditional coplanar electromagnetic bandgap (EBG) structure is analyzed. The method is studied to lower the center frequency and broaden the bandwidth in this paper. A novel structure of U-bridged EBG power plane is proposed. The simulation and test results show that the bandwidth of the new structure is 4.32 GHz, and the lower side cutoff frequency is at 380 MHz with stopband depth at -40 dB. The elimination of simultaneous switching noise (SSN) as this kind of U-bridged coplanar EBG structure is more effective below 1 GHz. In addition, the eye diagram of the structure is analyzed. The degradation of the maximum eye open and the maximum eye width on the structure is about 1.2% and 5.7% respectively. Finally, the IR-drop and dc resistance is accurately investigated through 3-D simulations.
Electromagnetic Interference (EMI) test is an important part for the manufacture of power electronic equipment, which helps us not only analyze the noise characteristics of the Equipment Under Test (EUT) but also design EMI filters. The previous separation method for the Common Mode (CM) and Differential Mode (DM) noise was time consuming or costly. In this paper, a novel measurement system for CM and DM conducted EMI is described showing a good performance. The system consists of two parts, part 1: getting CM noise or DM noise through a current probe; part 2: obtaining another mode noise from a software-based method. A 150w switch mode power supply is measured to verify the proposed measurement system. The noise spectra of CM and DM signal is shown, and the results obtained by software program are compared with those obtained from a current probe measurement showing a good concordance in terms of peak value.
A compact reconfigurable four-feeding microstrip antenna with polarization diversity is presented in this paper. With four triangle-shaped elements as the radiation patch, the proposed antenna can achieve good impedance match for linear polarization (LP), left hand circular polarization (LHCP) and right hand circular polarization (RHCP). A four-way power divider made by three Wilkinson power dividers and interconnected with PIN diodes is designed to feed the four elements. By controlling the states of the diodes, the antenna can produce LP, LHCP and RHCP. By using T-shaped slots on the patch and back to back geometry, a compact size of 0.6λ0× 0.6λ0×0.02λ0 is achieved. The impedance bandwidth of LP is about 80 MHz (3.3%), while the usable bandwidths (overlap of impedance bandwidth and AR bandwidth) of LHCP and RHCP are about 370 MHz (15%) and 250 MHz (10%). The average gain for LP is -2.1 dBi, and that for CP is -3.3 dBi. This reconfigurable patch antenna with switchable polarization has good performance and simple structure, which can be used for 2.4 GHz wireless communication systems.
A distinctive connection method in cascaded RF/MW active device system achieving both stability and low gain loss is presented. Unlike traditional methods (isolator and attenuator), the proposed solution introduces an appropriate length of transmission line to change the input impedance at the out-band instable frequency point and uses a narrow-band termination to absorb the instable power without deteriorating in-band signal. Moreover, the reason that instability often occurs in the cascaded system is analysed with S-parameters， and it turns out to be a kind of out-band instability. And then the solution is verified by an adjustable circuit example whose insertion loss is below 0.3 dB.
A new dual-band dual-sense circularly polarized (CP) slot antenna is designed in this paper. The proposed antenna is composed of a rectangle patch and a modified ground plane. By opening a U-shaped open-slot and loading a vertical stub to the ground plane, a dual-sense CP performance is achieved for two frequency bands. A bevel is cut on the patch to improve the impedance matching. The antenna is fabricated on a low-cost FR4 substrate and fed by a coplanar waveguide (CPW) structure. The antenna has been investigated numerically, and a prototype was experimentally measured. Experimental results show that the measured 10-dB return loss impedance bandwidths are 18.3% (2.72-3.27 GHz) for the lower band and 23.7% (4.65-5.90 GHz) for the upper band, and the measured 3-dB axial ratio (AR) bandwidths for the lower and upper bands can be up to 28.4% (2.48-3.30 GHz) and 26.3% (4.63-6.03 GHz), respectively.
In this paper, a wideband differential phase shifter has been analyzed and designed using Genetic Algorithm (GA). The differential phase shifter consists of two fixed main lines of length λ/2, and parallel open and short stubs of length λ/8, which are shunted at the edge points of the main lines, respectively. With the application of GA, an impedance match and minimum phase deviation for the desired phase shift over a wide frequency band are obtained. In order to verify the optimum results, simulation experiments are made and a 45° phase shifter is fabricated and measured. The phase shifter exhibits an impedance bandwidth (|S11|<-10 dB) and a consistent 45° (±2°) phase difference bandwidth around 66%.
A simple method for designing a triple-mode bandpass filter is presented in this paper. Triple-mode is achieved by using half-mode substrate integrated waveguide (HMSIW) cavity.Three perturbation metal vias were introduced for shifting resonant modes.The resonant frequencies of these modes can be adjusted by the location and the diameter of perturbation vias properly. In order to improve the out-of-band rejection, the CPW-to-SIW transition was added. A triple-mode HMSIW filter with the center frequency of 13 GHz was designed and fabricated. The measured fractional bandwidth is 35% with a transmission zero located at 20.4 GHz. Good agreement is observed between simulation and measurement.
A novel compact ultra-wideband (UWB) in-phase multilayer slotline power divider with high isolation is presented as a complement in slotline power divider field. The new structure proposed in this paper overcomes the shortcoming that power divider based on slotline almost cannot obtain high isolation between output ports. Based on the equivalent-circuit of microstrip-to-slotline transition and the method of odd-mode and even-mode analysis, the designing expressions of the proposed compact power divider have been obtained. The simulated and measured results have shown good agreement, and both of which have also shown that all the ports of the novel compact in-phase power divider have good impedance matching, and shown high isolation between the output ports over the band 3.4 GHz-12 GHz.
A novel compact two-element MIMO (Multiple Input Multiple Output) antenna system operating from 6.1-7.8 GHz is proposed for wireless applications. The developed antenna system resonates at 6.8 GHz frequency, giving an impedance bandwidth of 25% (based on S11<-10 dB). An efficient technique is proposed to reduce the mutual coupling developed in the antenna system by employing a simple microstrip patch element in between the antennas. Using the proposed method, the mutual coupling is reduced to around -33 dB at the resonant frequency and maintaining the overall mutual coupling less than -20 dB in the operating band. The experimental models are developed for both the MIMO systems i.e. without and with patch element between the antennas and the results are compared with simulated results. Also, Enveloped Correlation Coefficient (ECC) between the two antennas is calculated and compared.
A low-profile wideband circularly polarized aperture stacked patch (ASP) antenna without air dielectric layers is presented. The new circular ASP antenna, which is fed by two orthogonal dual-offset lines through an asymmetric crossed slot, delivers a wide bandwidth of 80% for the 10-dB return loss and similar input impedance characteristics for the two ports. Then, a novel broadband 90° hybrid feed network is employed to achieve good impedance matching, balanced power splitting and consistent 90° (±9°) phase shifting across the wide operating band. The two unbalanced feed lines are connected to the respective ports of the feed network comprising a three-section Wilkinson power divider and a broadband 90° phase shifter. It is found that the proposed antenna can achieve a measured impedance bandwidth of 91.3% (2.44-6.54 GHz), a measured 3-dB axial ratio (AR) bandwidth of 86.4% (2.5-6.3 GHz), and a measured gain bandwidth of 60.9% from 3.2 to 6.0 GHz for the gain >4 dBic. In addition, a comparison between the proposed wideband CP antenna and related wideband CP and ASP antennas in the literature is made.
In this letter, a dual-band Multiple Input Multiple Output (MIMO) antenna system with high isolation is presented. This design consists of two dual-band monopole antennas and neutralizing transmission line. For each antenna element, the operating frequency band covers from 2.4 GHz to 2.6 GHz and 5.2 GHz to 6 GHz. To improve the isolation between these two antenna elements spacing only 0.1225 λ0 at 2.45 GHz, a neutralization decoupling transmission line is introduced. The measured return loss results of these two antennas are better than 10-dB in operating frequency band. The measured isolation between the two antennas is better than 15 dB. The envelope correlation coefficient (ECC) is smaller than 0.01 of whole operating frequency band. The peak gain of this design is better than 2 dBi in operating bands. This configuration can be applied for Wireless local area network (WLAN) and Bluetooth (BT) communication system.
Some microobjects can concentrate an incoming incident plane wave and create the socalled photonic nanojets. These highly focused emerging beams have a high intensity and can be used in applications such as microscopy, beam manipulation and imaging. In this article, it is shown that an adequate choice of geometric shape and material can lead to an improvement of the electric field enhancement capability of nanojets by a factor of 40%.
By the transfer matrix approach we numerically study the electromagnetic properties (narrow peak positions) of the transmission spectra for microspheres coated by a multilayered stack with the generalized Cantor structure (fractal). As opposed to the standard Cantor system with removed γ/3 [γ=1] section we consider here the solid stack with Si/SiO2 layers at general γ value. In such a solid composition the SiO2 layers replace the empty Cantor sections and the parameter γ acquires meaning of a specific control parameter. At successive generations the central layers (in blocks of the spherical stack) acquire a progressive decreased width that leads to generation of the radially inhomogeneous defects. We show that the wave phase interference in such a fractal pattern leads to formation of very narrow electromagnetic transmittance resonances that can be used in modern optoelectronics.