This paper presents an accurate analytical explicit expression for the self-inductance of a flat pancake round coil made up of concentric turns. The expression is obtained by converting the semi-infinite integral representation for the mutual inductance between two arbitrary turns of the coil into a finite integral, and then by expanding the integrand into a series of Legendre polynomials. As a result, a sum of simpler integrals is obtained, whose analytical evaluation is straightforward. The self inductance is finally expressed as the sum of logarithmic functions, describing the contributions from the self-inductances of the single turns, plus the mutual-inductance terms originating from all the possible pairs of turns of the coil, each one given by a power series of the ratio between the radii of the turns. Numerical simulations are performed to illustrate the advantages of the proposed solution.
In this paper, design of a novel dual-band microstrip bandstop filter is presented. The designed filter is constructed by loading two stepped impedance hairpin resonators to a simple straight transmission line, which also connects to the input and output ports. By virtue of the proposed resonator, the ratio of the first and second resonance frequencies can be obtained as approximately 4.4. Two stopbands centered at 2.34 GHz and 7.81 GHz with the fractional bandwidths of 33.2% and 7.9% can be obtained, respectively. Rejection levels inside the stopbands are obtained as better than 20 dB. Total electrical length of the proposed filter is 0.317λgx0.136λg, where λg is the guided wavelength at the lowest resonance frequency. The designed filter was also fabricated and tested for experimental verifications. The measured results are in an excellent agreement with the simulated ones.
In this paper, design and measurements of a highly selective π-CRLH dual-band bandpass filter, with transmission zeros optimized to serve Wi-Max applications, is presented. The dual-bands are designed at 5.2 and 5.7 GHz with a sharp rejection level between them and transmission zeros before and after the passbands. The filter is designed using coupled gap zerothorder composite right/left-handed (CRLH) resonators, which results in significant filter size reduction. Furthermore, two different coupled π-CRLH filters are discussed through the work development of this paper. The filter design concepts are verified and confirmed using electromagnetic simulations and experimental measurements. Presented results reveal that the proposed filter exhibits a rejection level greater than -20 dB, while maintaining 2 dB insertion loss and better than -25 dB for the transmission zeros with compact size (12×16 mm2) which is 70% smaller than similar conventional filters.
This paper presents a direct synthesis approach for UWB BPFs. The modified Chebyshev filtering function is used to characterize the frequency response over the whole frequency range of the BPF. As for the filter's circuit, open circuited MMR capacitively coupled with I\O ports is used, and two shunt short-circuited stubs are placed at the two ends of the connecting line to sharpen the rejecting skirt of the passband. The equivalent circuit's transfer function is derived. By equating the filtering function to the transfer function of the circuit, the design parameters are obtained. The uniform connecting line is then replaced by nonuniform line to suppress spurious harmonics and achieve very wide stopband. In order to avoid critical precision requirement in the fabrication of the filter, we design the filter using suspended stripline (SSL) technology to replace the parallel-coupled microstrip lines (PCML) with very small coupling gaps. Finally, a filter prototype is designed and fabricated to experimentally validate the presented method. Experimental results show good agreement with EM-simulated and theoretical ones.
A novel miniaturized bandpass half-mode substrate integrated waveguide (HMSIW) filter which uses dual-iris coupling method to load complementary split-ring resonators (CSRRs) into HMSIW is proposed in this paper. By modifying traditional CSRRs through nesting method combined with step impedance structure, a nested stepped-impedance complementary split-ring resonator (NSICSRR) structure with higher equivalent capacitance and inductance of CSRR is obtained. Based on the traditional single-iris coupling method, a dual-iris coupling method is developed. And NSICSRR is loaded into HMSIW by using the dual-iris coupling method, which can reduce the resonant frequency of the structure. In order to verify the effectiveness of the technology above in realizing the miniaturization of HMSIW filter, a second-order HMSIW filter is designed and measured. It can be found in the measured results that the filter has the center frequency of 6.35 GHz, the 3 dB bandwidth of 690 MHz, the return loss of better than 14 dB within the passband, and the size of 0.0396λg2. The experimental results are basically consistent with the simulation ones.
In order to design a robust passive temperature sensing tag that can operate over a wide temperature range, temperature-sensitive characteristic of UHF radio frequency identification temperature sensing chip and corresponding tags are studied. The devices under test include dipole tags with different antenna impedances. Simulation data, experiment design, system setup, measurement procedures, and test results are given. The results show that as temperature increases, the real part of chip impedance increases, and the absolute value of the imaginary part decreases, which are consistent with simulation data. In the full temperature range, the overall performance of sensing tags designed for high-temperature conditions is better than tags designed only for room temperature conditions.
A dielectric resonator (DR) based MIMO (Multiple Input Multiple Output) antenna with enhanced isolation is proposed in this letter. The proposed MIMO antenna consists of four hemispherical shaped dielectric resonator (HDR) radiating at 4.9 GHz. The isolation between two consecutive radiators is enhanced by rotating feeding line of one element at an angle of 180˚. The antenna is studied in terms of S-parameters, gain, envelope correlation coefficient (ECC), channel capacity loss (CCL) and diversity gain (DG). All the parameters are found to be within acceptable range. The proposed design is fabricated, and it is found that measured results are in good agreement with simulation.
A patch antenna system operating in the 2.4-2.5 GHz ISM band is proposed for in-band full duplex applications. The proposed antenna consists of a patch antenna, a modified 180˚ hybrid, and a defected ground structure. Fabricated prototype results show a measured bandwidth of 100 MHz and an isolation of -75 dB at the center frequency with an isolation of at least -50 dB covering the ISM band 2.4 GHz-2.5 GHz. The design also has a spherical directional radiation pattern, low cross polarization, and reasonable gain values.
The propagation equation of a Lorentz-Gauss (LG) vortex beam in biological tissues is derived. The influences of the beam parameters and the biological tissues on the spreading properties of a LG vortex beam are investigated. The obtained results are interpreted numerically and shown that the LG vortex beam propagating through biological tissues with the stronger turbulence strength will lose the dark hollow center and evolve into the Gaussian-like beam more rapidly.
Radar sliding window detection processes are often used in signal processing as alternatives to Neyman-Pearson based decision rules, due to the fact that they have a simpler receiver implementation and can often be designed to maintain a constant false alarm rate in homogeneous clutter. These detection processes produce a measurement of the clutter level from a series of observations, and compare a normalised version of this to a cell under test. The latter is an amplitude squared measurement of the signal plus clutter in the complex domain. It has been suggested by some authors that that there is sufficient merit in the approximation of the cell under test by a distributional model similar to that assumed for the clutter distribution. This is certainly the case when a Gaussian target is combined with Gaussian clutter, or equivalently a Swerling 1 target and exponentially distributed intensity clutter. The purpose of the current paper is to demonstrate, in a modern maritime surveillance radar context where the clutter is modelled by Pareto statistics, that such an approximation is only valid under certain limiting conditions.
This paper presents the enhancement of bandwidth in circular and annular ring sectoral patch antennas. The cavity model approach has been used in identifying the higher order mode resonances that are close to each other in the sectoral patches. Bandwidth enhancement centered around these higher order mode resonances is achieved through the use of either a shorting pin or a parasitic patch. The sectoral patches have been simulated using ANSYS HFSS. The optimum position of the shorting pin and the dimension and position of the parasitic patch were determined through parametric simulations on HFSS. Measurements showed that the annular ring sectoral patch with optimally positioned shorting pin achieved 6.3 percent bandwidth with a return loss performance greater than 10 dB while the circular sector patch with a parasitic patch achieved 5.6 percent.
A compact multiband multiple-input-multiple-output (MIMO) antenna for WLAN applications is presented in this paper. The proposed MIMO antenna consists of two symmetric monopole radiating elements designed to operate over 2.45, 5.2, and 5.8 GHz bands. The isolation is enhanced by using several techniques such as parasitic elements and defected ground structure. The measured S11 < -10 dB is obtained over 2.36-2.68 GHz and 4.81-5.95 GHz, which can cover IEEE 802.11 a/b/g/n frequency bands (2.4-2.4835 GHz, 5.15-5.35 GHz, and 5.725-5.875 GHz). The measured isolation values S21 are less than -24 dB and -27 dB over the lower and higher frequency bands, respectively. The envelope correlation coefficient (ECC) of the proposed antenna is less than 0.027 and 0.005 over the lower and higher operating bands, respectively. The overall size of the proposed antenna is 50×30×1.59 mm3. The proposed antenna is a good candidate for IEEE 802.11 a/b/g/n applications.
Solid state plasma antenna based on surface PiN diodes is characterized by its wide radiation range, good stealth characteristics, compatibility with traditional microelectronic technology, and dynamic reconfiguration, which has very broad application prospects in the fields of wireless communication, radar, and remote sensing. To improve carrier concentration and uniformity within theintrinsic region, a novel SPiN diode with a double-layer structure is described in this paper. This structure can compensate the concentration attenuation at the midpoint of the `i' region, which makes carriers have a more uniform distribution with high concentration, and carrier concentration within the `i' region twice of the traditional SPiN diode. A Si/Ge/Si heterojunction diode is also researched in this paper. These results indicate that a fully reconfigurable semiconductor plasma antenna based on this novel surface PiN diode is achieved to meet the currently-growing communication requirements.
Based on Huygens-Fresnel principle, a general expression for the average image intensity of a heterodyne and a direct-detection imaging system in turbulent media is derived under the assumption of a Gaussian rough-surface model. From the formulation, we find that the object size, turbulence strength, wavelength, and object roughness affect image intensity dramatically in the image plane.
A compact, triple-band (WiMAX, WLAN and X-Band uplink satellite communication) monopole antenna is reported in this paper. The geometry of the proposed antenna consists of a pentagon-shaped patch along with symmetrical hook-shaped resonators and one vertical slot. The reported antenna works at three unique frequencies centered at 3.5 GHz, 5.4 GHz, and 8 GHz, covering absolute bandwidth of 900 MHz (3.2-4.1 GHz), 800 MHz (5.1-5.9 GHz), and 1.6 GHz (7.3-8.9 GHz), respectively. This antenna possesses good gain and high efficiency at all operating bands. The presented antenna has simulated gain (efficiency) of 4 dBi (78%), 4.2 dBi (79.95%), and 4.2 dBi (85.8%) at 3.5, 5.4, and 8 GHz, respectively. The operating bands of the presented antenna can be tuned independently by varying certain correlated parameters. All the simulations are carried out using High Frequency Structure Simulator (HFSS 13.0). The hardware of the simulated antenna is successfully constructed and tested for validation of simulation results. A reasonable match between the simulated and measured results is observed at the operating bands.
In this paper, a new method of improving cross-polarization (XP) performance on a wideband microstrip antenna is proposed, by adopting a defected ground structure (DGS). This F-slot shaped defected ground structure (F-DGS) exhibits considerable improvement in terms of XP properties, broad boresight angular suppression, and impedance bandwidth (S11 < -10 dB). Lower than -26 dB XP level is achieved over 206˚ angular range, while the impedance bandwidth is broadened to 15.5%. Both wideband rectangular patches with and without F-DGS have been fabricated and experimented.
This paper presents a compact Wilkinson power divider (WPD) operating at 0.7 GHz (LTE band) with higher order harmonics suppression based on step impedance shunt stubs (SISSs) and defected ground structure (DGS). The quarter wavelength lines of conventional WPD are replaced by a host line loaded with a DGS and a pair of SISSs. The DGS and SISS of the proposed line serve as a high series inductance and shunt capacitance, respectively. Therefore, a compact quarter wavelength line is designed compared to conventional one. A prototype of the proposed power divider is designed based on the proposed line, which provides a size reduction of 71% as compared to conventional WPD (CWPD) at 0.7 GHz. In addition, upper edge selectivity is found to be 40 dB/GHz along with higher order harmonics suppression up to the 10th order (7GHz) by a level better than 20 dB. The proposed power divider is experimentally verified with the simulated one and found to be same.
In this paper, the Runge-Kutta exponential time differencing (RK-ETD) scheme is used for incorporating Graphene dispersion in the finite difference time domain (FDTD) simulations. The Graphene dispersion is described in the gigahertz and terahertz frequency regimes by Drude model, and the stability of the implementation is studied by means of the von Neumann method combined with the Routh-Hurwitz criterion. It is shown that the presented implementation retains the standard non- dispersive FDTD time step stability constraint. In addition, the RK-ETD scheme is used for the FDTD implementation of the complex-frequency shifted perfectly matched layer (CFS-PML) to truncated open region simulation domains. A numerical example is included to validate both the stability and accuracy of the given implementation.
This paper presents a wideband gate mixer using 0.15 μm GaAs enhancement-mode pseudomorphic high electron mobility transistor (E-mode PHEMT) process. The proposed mixer is based on a single-ended gate mixer topology. Proper input matching networks are used to ensure good conversion gain as well as a wide frequency band. A λ/4 open stub at local oscillator (LO) frequency and a low-pass filter at the drain terminal do great help to enhance LO-IF and RF-IF isolation performance. A Lange coupler is used to maintain LO-RF isolation in a wide frequency band. The measured results show that the mixer operates in wide RF frequency of 17-26 GHz and IF frequency of 0.8-1.7 GHz with a conversion gain of 5-8 dB. The 1 dB compression point (P1 dB) is -1~1 dBm, and the needed LO power is only 1 dBm. The LO-IF, RF-IF, and LO-RF isolations are about 45, 45, and 20 dB, respectively. This represents excellent performance for GaAs PHEMT mixer in terms of frequency bandwidth, conversion gain, isolation, and P1 dB performance.
In this paper, a co-planar waveguide fed circular slot antenna with an operational impedance bandwidth of 20-28 GHz is proposed. In order to reduce the effective occupied volume when the antenna is integrated onto a typical mmWave 5G smartphone, a conformal topology is investigated. Since the radiating aperture is not backed by an electrically large ground plane, it leads to a bidirectional beam resulting in an inherently low forward gain of 4 dBi with a front to back ratio of 1 dB. Hence, a compact exponentially tapered copper film reflector is integrated electrically close (0.046λ at 28 GHz) to the radiating aperture to achieve a forward gain of 8-9 dBi with an effective radiating volume of 0.24λ03. The impedance bandwidth is from 25 to 30 GHz (18.2%) with a 1-dB gain bandwidth of 34.7% indicating high pattern integrity across the band. Since the proposed antenna element offers wideband with high gain, it is a potential candidate for mmWave 5G smartphones.