A compact two-element multiple-input-multiple-output (MIMO) antenna with high isolation is proposed in this paper. It is based on a half-mode substrate-integrated-waveguide (SIW) cavity where three edges are shorted by metallic vias, and one edge is opened to radiate cavity energy into free space. Fed by coaxial ports, two antenna elements are constructed in the SIW cavity, and a narrow T-shaped slot is introduced to enhance the isolation between them. High port isolation can be achieved by adjusting the slot length although these antenna elements are connected with each other. A prototype has been fabricated and measured. With the compact cavity size of 0.22λ0 × 0.44λ0, the fabricated antenna achieves the operating frequency of 3.51 GHz, enhanced isolation of 18.0 dB, low envelope correlation coefficient of 0.006, peak gain of 5.2 dBi, and high efficiency of 82.6%. Therefore, the proposed MIMO antenna has potential applications for wireless communication.
In this paper, a new dual-band bandpass filter (BPF) using a cross ring resonator is designed. The cross ring resonator is modified from a typical dual-mode ring resonator and has four parallel coupling gaps (g). The resonant modes of the proposed cross ring resonator is investigated first. It is found that the first mode and the second mode can be tuned individually. The filter performances are simulated by using full-wave simulator IE3D. A filter example having two passbands operated at 2.4/5.2 GHz of wireless local area network (WLAN) applications is described to verify the design concept. The fabricated filter has measured characteristics including average insertion losses of 2.0 dB and 1.8 dB and return losses larger than 22 dB and 10 dB for 2.4/5.2 GHz, respectively. Two transmission zeros with high frequency selectivity of 40 dB and 42 dB are obtained near the first passband at 2.2 GHz and 2.7 GHz, respectively. This design is very simple as compared to other design methods, and the measured results prove the design concept of the proposed structure.
Performance of optical add-drop multiplexer (OADM) for 400 channels with data rate of 20 Gbps for super dense wavelength division (SD-WDM) multiplexing system has been investigated in terms of varying transmission distance from 50 km to 250 km and 80 km to 240 km for enhancing optical communication. Long haul amplification is maintained by RAMAN-EDFA hybrid optical amplifier (HOA). Evaluation is carried out in terms of bit error rate (BER) and dispersion.
This paper proposes a prototype of a flexible antenna which utilizes a star patch design. The work seeks feasibility of the star patch antenna to maintain its characteristic when it is bending on a curvy structure. The patch antenna is fabricated on a 0.8 mm thickness, h of polyimide film with a dielectric permittivity, εr of 3.4. The simulation result in Computer Simulation Technology Microwave Studio (CST MWS®) software shows that the antenna provides a -10 dB bandwidth of 24.9% at 2.45 GHz with a minimum reflection coefficient, S11 of -27.67 dB in the flat condition. The stability in its performance has been noticed in which the shift in the resonant frequency is less than 2% when the structure is bending on a curvy surface with a radius of 90 mm. The measured results in terms of reflection coefficient, bandwidth, radiation pattern and gain demonstrate a good agreement with the simulated results.
In this paper, we propose a transmissive quarter wave plate (QWP) which can provide linear-to-circular polarization conversion in terahertz (THz). The structure is composed of one dielectric layer with staggered split ring resonators (SSRRs) on both sides. The simulation results show that the proposed structure can offer a nearly pure left circularly polarized wave with 3 dB axial ratio bandwidth of 0.337 THz; meanwhile, the bandwidth of polarization conversion efficiency beyond 80% reaches 0.170 THz. Additionally, the distributions of surface currents and electric field are discussed to explain the physical mechanism of the proposed structure. The linear-to-circular polarization conversion can be attributed to the inductance effect and capacitance effect between SSRRs. Finally, we validate the performance of the proposed THz-QWP. Such a device could potentially be used in THz communications, THz imaging, and THz sensing.
High-altitude electromagnetic pulse (HEMP) field tests are often conducted in the working volume of HEMP simulators to verify the hardness or HEMP survivability of the systems under test. For HEMP field tests, enough confidence should be provided through certain specific test designs. In this paper, the confidence probability of HEMP field tests is defined through a statistical analysis. Based on this definition, the confidence level of the tests is proposed to address the problem that the probability of a failure or significant upset is unknown. The relation between the number of repeated illuminations in one test status and confidence level is provided after analysis. By balancing cost and confidence level, an appropriate number of the repeated illuminations for each test status can be obtained. The comparison with the definition in another article is also made.
In fusion reaction, plasma parameters such as the density and temperature of electrons should be diagnosed continuously. There are various methods to diagnose plasma parameters. In these, reflectometry systems are widely used to measure the electron density and plasma physics study. In reflectometry systems, antenna plays an important role as a transmitter/receiver element. This paper presents the design of a D-band (110-170 GHz) corrugated horn antenna suitable for reflectometry system. The simulated results for antenna are compared with that of the measurements. Further, different structures are proposed to ease fabrication complexities and reduce cost.
The design of conventional stepped-impedance microstrip line low pass filter (LPF) is based on high (ZH) to low impedance (ZL) ratio. The width of ZH line, for ZH > 100 Ω, becomes critical and challenging, especially on high dielectric constant substrates. A concept of air-filled recessed ground plane below a microstrip line is introduced in this paper. The effect of dimensions of recessed ground on characteristic impedance, attenuation and propagation constant of a microstrip line are first studied. This simple approach is utilized to design the ZH line of stepped-impedance microstrip line LPFs. Prototypes of recessed ground stepped-impedance microstrip line LPFs with ZH/ZL (keeping ZL constant as 20 Ω)ratio in the range 6 to 10 are designed and developed on Rogers 4350B of height 0.508 mm with εr = 3.66 at 3 GHz. For LPF with ZH/ZL = 10, the measured 3-dB cutoff frequency (fc) is achieved at 3.12 GHz with return loss (RL) > 12 dB and insertion loss (IL) < 0.28 dB in its passband whereas the stopband attenuation (SBA) is better than 38 dB. In comparison to recessed ground LPF, the simulated results of conventional LPF with ZH/ZL = 10 (critical width of ZH line =) are as follows RL > 10 dB and IL < 1.07 dB in passband at fc = 3 GHz. The size of recessed ground LPF is reduced by 25%, when ZH/ZL is increased to 10 from 6. The approach of recessed ground microstrip line avoids the fabrication issues, reduces size, and improves the performance of LPF, which in turns confirms the advantages of recessed ground over conventional microstrip line.
In this paper, design of a novel broadband Canonical Tetra Sleeve Cage Antenna is presented. This antenna is designed using distributed antenna matching techniques. It has canonical shaped antenna elements and coaxial sleeves. The designed antenna operates over a wide frequency range in UHF band with omnidirectional characteristics. The proposed antenna is simulated in CST Microwave Studio, fabricated, evaluated, and the results are presented. The simulated and measurement results are in agreement. It has VSWR < 1.9:1 in frequency bands 270-330 MHz and 930-1670 MHz. The maximum value of VSWR in 250-1850 MHz is 3.3:1. The measured gain of the antenna varies from 0.6 to 5.5 dBi in the frequency range of 250 MHz to 1850 MHz. The implementation of distributed matching techniques by using canonical shaped antenna elements and tetra sleeves results in reduction of the length of the antenna by 59.86% compared to the length of a half wave dipole antenna designed at the lowest frequency. The proposed antenna finds applications in defence and wireless communication systems as a transceiver antenna.
This paper presents a stacked rectangular dielectric resonator antenna design. In this structure, two sapphires having the same dielectric constant and different dimensions piled over each other have been used for designing the proposed antenna. The designed antenna exhibits two frequency bands from 7.41 GHz to 8.21 GHz and 9.11 GHz to 12.65 GHz and impedance matching of 50 ohms. The proposed antenna design is a fine choice for subterranean and rugged communication, in addition, owing to sapphires unique features viz. durability, endurance, and aversion to physical change. The antenna structure is aperture coupled. Due to the advantage of aperture coupled feed mechanism such as good isolation between antennas and feed networks it has been employed. The antenna prototype has been fabricated, measured, and tested using Vector Network Analyzer and Anechoic Chamber to validate the proposed antenna design. The simulation results obtained indicate close proximity of tested result.
This paper presents a single layer, dual polarized 2.4 GHz microstrip patch antenna based on monostatic radiator. Microstrip-T (MS-T) feeds have been used for DC isolated Tx-Rx ports. It deploys differential feeding for receive mode operation to achieve high interport RF isolation. The differential feeding acts as a signal inversion technique to suppress the in-band self interference (SI) for simultaneous transmit and receive (STAR) operation at same frequency. The implemented single layer, dual polarized, compact patch antenna provides better than 78 dB isolation between DC isolated Tx- Rx ports at centre frequency of 2.393 GHz. Moreover, the implemented antenna achieves better than 64 dB interport isolation for 10 sdB-return loss bandwidth of 50 MHz (2.37 GHz to 2.42 GHz). The measured interport RF isolation is around 70 dB for 25 MHz bandwidth (2.385 GHz to 2.41 GHz). To the best of our knowledge, these are the highest levels of RF isolation reported for single layer, dual polarized microstrip patch antenna with DC isolated ports.
Due to the high power conversion efficiency, high efficiency and energy saving, wide voltage regulation range and light weight, switching converters are widely used in many fields such as industry, military, and medicine. However, strong electromagnetic interference can affect the normal operation of switching power supply and also has a negative impact on the external environment. Based on this phenomenon, we focus on the electromagnetic compatibility of switching power supply, and a high-frequency model for PSFB circuit is proposed. At last, a set of verification tests are conducted to verify the validity of the proposed model in this paper.
A novel wideband circularly polarized (CP) cross-dipole with wide 3 dB axial-ratio (AR) beamwidth is presented. To generate CP radiation, the cross-dipole is fed by a Wilkinson power divider which can provide 90° phase difference. The gain beamwidth and 3 dB AR beamwidth can be widened by the bent arm structures of cross-dipole and four vertical parasitic elements. As a result, the 3 dB AR beamwidth and gain beamwidth of the proposed antenna can achieve over 210° and 105°, respectively. It is observed that the impedance bandwidth (|S11| ≤ -10 dB) of the proposed antenna is 1.2~2.0 GHz, and the AR bandwidth (AR ≤ 3 dB) is 1.28~1.76 GHz. The simulated and measured results are in good agreement, which shows that the proposed antenna is a good candidate for the application of satellite communications.
Aiming at the problem of crosstalk in high-speed interconnects, a non-crosstalk scheme based on coupled transmission lines-channel transmission matrix (CTL-CTM) is proposed. In this scheme, the transmitted signals are linear combination transformed at the transmitting end of the interconnect lines where the transmission signals among the interconnect lines constitute an orthogonal mode. After the signals have synchronously transmitted to the receiving end, second linear combination transformation is performed to restore the transmitted signals. Simulation results show that this low cost circuit proposed is capable of improving the quality of eye diagram and eliminating the crosstalk obviously.
The analytical propagation equation of a four-petal Lorentz-Gauss (FPLG) beam propagating through atmospheric turbulence is derived, and the spreading of average intensity is analyzed by using numerical examples. It is found that the FPLG beam propagating through atmospheric turbulence will evolve into Gaussian beam due to the influences of atmospheric turbulence, and the atmospheric turbulence will accelerate the spreading of FPLG beam as the propagation distance increases. It is also found that the FPLG beam with different N or Lorentz widths propagating through atmospheric turbulence will have the same beam spot when the FPLG beam evolves into the Gaussian beam at the same propagation distance.
In the applications such as induction motor efficiency optimization and electric vehicle speed control, the influence of the iron loss cannot be ignored in order to improve the running efficiency of induction motor, the ordinary differential equations (ODE) and difference equations (DE) of induction motors considering iron loss have been established. The results show that the proposed refined ordinary differential equations and difference equations of induction motors considering iron loss and its simulation models are believable, and simulated and experiment results have demonstrated that the models perform well.
In this letter, a space time synthesizer for the generation of monthly cloud free line of sight (CFLOS) statistics is presented. The proposed monthly time series generator is based on the synthesis of 3D cloud fields using Stochastic Differential Equations. Monthly Integrated Liquid Water Content (ILWC) statistics are used as inputs, and the temporal and spatial correlation of clouds is considered. The monthly variability of the cloud coverage is predicted, and the CFLOS is estimated taking into account the elevation angle of the slant path and the altitude of the station for high altitude optical ground stations. Finally, CFLOS numerical results are reported, and some significant conclusions are drawn.
Solar hydrogen line emission has been observed at the frequency of 1.42 GHz (21 cm wavelength) with 3 m radio telescope installed inside the University of Baghdad campus. Several measurements related to the sun have been conducted and computed from the radio telescope spectrometer. These measurements cover the solar brightness temperature, antenna temperature, solar radio flux, and the antenna gain of the radio telescope. The results demonstrate that the maximum antenna temperature, solar brightness temperature, and solar flux density are found to be 970 K, 49600 K, and 70 SFU respectively. These results show perfect correlation with recent published studies.
An ultra-wideband multilayer-stacked Yagi antenna is presented in this article. The proposed design is based on a capped bow-tie antenna, on which a Yagi antenna is formed simply by capping several pieces of parasitic patches with equal lengths but unequal widths. Thus, the multilayer-stacked antenna attains a small footprint, compact size, customizable gain and simple geometry, which make it promising for various applications. The prototype of this antenna is simulated, fabricated, and measured. Good agreement between simulation and measurement has been observed.
There are three mathematical conditions that must be solved simultaneously for the analysis of a fully-symmetric radio-frequency (RF) crossover. When additional reciprocal two-port networks - which might be of an arbitrarily high complexity - are appended at each port of a crossover, analysis of the modified crossover becomes very tedious. Therefore, this paper examines the requirement of the three conditions in such scenario. We show that two of the three conditions can be invoked without considering the additional two-port networks altogether. This is a remarkable simplification considering that the additional two-port networks, in general, would necessitate dealing with more involved algebraic calculations. To demonstrate the usefulness of the presented theory, for the first time, analysis and design of a dual-frequency port-extended crossover is included. A prototype of the dual-frequency crossover operating concurrently at 1 GHz and 2 GHz is manufactured on a Rogers RO4350B laminate having 30 mil substrate height and 3.66 dielectric constant. The close resemblance between the EM simulated and measured results validates the analytical equations.