A novel single-layer band-pass frequency selective surface (FSS) is proposed in this letter. The unit cell is composed of a series of rotationally symmetrical fishbone-shaped structures surrounded by a modified octagonal loop. This fishbone-shaped FSS exhibits stable resonant frequency while the incident angle ranges from 0˚ to 60˚ for both TE and TM polarizations, which means that polarization insensitivity and angular stability are well demonstrated on the proposed FSS. A prototype is fabricated and measured in an anechoic chamber, and good agreements are obtained between measured and simulated results.
A wideband dual-mode band-pass filter (BPF) is proposed and implemented using a vertically stacked double-ring resonator (VSDR) and a pair of broadside-coupled input/output (I/O) feeding lines based on a 4-layer low temperature cofired ceramic (LTCC) substrate. The proposed BPF is required to cover the fifth generation (5G) N77/N78/N79 band (3.3-5 GHz), thus achieves a fractional bandwidth (FBW) of 40%. Furthermore, the proposed structure not only possesses a non-orthogonal I/O feeding style for convenient interconnection with neighboring devices, but also removes disturbing element for simpler layout. Comparison and discussion are implemented as well.
Non-parallel microstrip lines are a layout often used in high-speed interconnections. This study initiates crosstalk reduction by interdigital capacitor for the non-parallel microstrip lines. This method reduces the far-end crosstalk by adding capacitive coupling to cancel inductive coupling after an interdigital capacitor is added at the near end of the non-parallel microstrip lines. Software simulation and actual measurement results show that the proposed method can effectively reduce the far-end crosstalk in non-parallel microstrip lines. The method is also easy to implement and in low cost.
The sensitivities of an aluminum gallium arsenide Al0.7Ga0.3As based surface plasmon resonance (SPR) sensor with gold (Au) and silver (Ag) layers are numerically analyzed and compared at 633 nm wavelength for different thicknesses of the Al0.7Ga0.3As. As the thickness of Al0.7Ga0.3As increases, the sensitivity of aluminum gallium arsenide Al0.7Ga0.3As with a specific metal (Au or Ag) layer increases. Our calculations show that the sensitivities of the proposed sensors are 80.55% (Au film) and 34.74% (Ag film) higher than the conventional Au and Ag sensors successively. The aluminum gallium arsenide Al0.7Ga0.3As based SPR sensor has the advantages of high angular sensitivity, narrow resonance widths, and low minimum reflectance, making it a much better choice for biosensing applications.
A novel balanced bandpass reconfigurable microstrip filter is presented, where in differential mode, the filter operates in seven different bands, and each inductor LM represents a state of frequency. The common mode rejection ration (CMRR) is better than 30 dB for all the states. The central frequency of the filter is changed by liquid metal droplets flowing along a microfluidic channel placed at the middle of the inductors LM. For demonstration, a third-order filter is designed, simulated, and fabricated, operating in the S-band. Good agreement between simulation and measurement is presented.
This paper presents a 90° broadband compact phase shifter which employs loade λ/2 transmission line. By adding an H shaped open stub loaded transmission line, the bandwidth of the phase shifter is broadened. Detailed theoretical analysis and circuit configuration are presented to explain the mechanism. The proposed phase shifter is fabricated and measured to validate the design principle. The simulated and measured results show that the proposed phase shifter achieves 6.6 to 19.4 GHz bandwidth with low phase instability ±5°, very low insertion loss (0.3 dB in 7.5-15.2GHz), high return loss (10 dB), and a compact size (5.8cm*6.1cm). Good agreements are observed between the measured and simulated results with small phase deviation. Moreover, the configuration of the proposed phase shifter is simple in both design and fabrication which makes the design suitable for actual applications.
The study of the electromagnetic field, taking into account eddy currents in the conductive half-space, is based on the exact analytical solution of the general three-dimensional quasi-stationary problem. The mathematical model includes an approximate solution using asymptotic expansion in the case of strong skin effect. Analytical expressions are obtained for the electric and magnetic fields at a flat interface in the form of limited asymptotic series, each term of which is expressed through a known field of external sources. The expressions take into account the nonuniformity of the field near the surface, since they contain its derivatives with respect to the coordinate. The series expansion was carried out according to a small parameter, which is proportional to the ratio of the field penetration depth to the distance between the interface and the sources of the external field. The found expressions generalize the approximate boundary impedance condition for the case of the penetration of nonuniform electromagnetic field into conductive medium.
In this paper, a joint two dimensional (2D) direction of departure (DOD) and 2D direction of arrival (DOA) strictly noncircular (NC) unitary estimation of signal parameters via rotational invariance techniques (ESPRIT) method is proposed for an L-shaped bistatic multiple input multiple output (MIMO) radar. In the case that the incident signals are NC signals, we first utilize the received data vector and its conjugate counterparts to construct a new data vector, and then the unitary ESPRIT method is adopted to estimate the 2D-DODs and 2D-DOAs, which can automatically pair the four dimensional (4D) angle parameters. Simulation results are included to verify the effectiveness of the proposed algorithm.
Frequency selective surface is a key component in applications such as communication antenna and remote sensing radiometer. One of the core parameters is selectivity, which is usually realized using a multi-layer structure or through a complicated 3D structure. These methods, however, would impose much challenge on alignment or fabrication. This paper proposes a single-substrate and combined-united array to realize a high selectivity frequency selective surface. The unit cell is a combined pattern of cross dipole and square loop to generate double transmission zeroes out of the passband. Both sides of the substrate are printed with the same pattern to enhance the selectivity. Such a structure enables easy fabrication and assembly by avoiding using multi-substrates. A prototype in the Ku-band demonstrates that both sides of the passband show high selectivity.
A novel and compact CPW fed triband antenna suitable to support WLAN and WiMAX communications in 2.4/3.5/5.5 GHz bands is reported. The 5.5 GHz band extends from 4.9 to 5.94 GHz. So the proposed antenna can support the use of 4.94-4.99 GHz band allotted for fixed and mobile service (except aeronautical mobile service) for use in support of public safety and 5.85-5.925 GHz band for Dedicated Short-Range Communications (DSRC) services in the Intelligent Transportation System (ITS) radio service. Metallic radiating stub extending from the feed is used to excite the resonance at 2.4 GHz. An open slot in the stub and a pair of open slots in ground plane are used to excite the other resonances. An arc shaped parasitic element is also included in the design for improved radiation performance. The proposed antenna geometry is developed on FR4 glass epoxy substrate with relative permittivity 3.8 and loss tangent 0.02. The geometry is developed and optimized using High Frequency Structure Simulator and experimentally validated the results. Performance comparison of the proposed antenna with similar antennas in literature is presented. Measured radiation patterns and gain are also included in this paper.
In this paper, a dual-band bandpass filter using sixteenth-mode substrate integrated circular cavity (SM-SICC) and a novel ultra-wideband (UWB) bandpass filter (BPF) using eighth-mode SICC (EM-SICC) cavity are presented. The TM101, TM102, and TM201 resonant modes of the substrate integrated waveguide (SIW) circular cavity are used to design the dual-band filter, where the resonant frequencies can be shifted to the desired frequency through adjusting the position and size of complementary split-ring resonator (CSRR). In addition, the TM101, TM102, TM103, and TM104 resonant modes are employed to realize the UWB filter. A transmission zero appears by introducing the complementary split-ring resonator (CSRR) in the middle of the SICC, so the dual-band BPF and UWB BPF with high selectivity are realized. The proposed filters possess compact size, because of the EMSIW and SMSIW cavity. The dual-band filter operating at 7.79 and 12.83 GHz is fabricated in SM-SICC with 3-dB fractional bandwidths (FBWs) of 7.8% and 31.25%, respectively. The UWB filter with FBW of 97% is simulated in EM-SICC. Compact circuit sizes and excellent measured performances have been achieved for the two filters.
An S-band bandpass filter based on quarter wavelength stepped-impedance resonator (SIR) is presented in this paper. Two SIRs are loaded to the BPF to obtain wide stopband suppression. The center frequency f0 of the bandpass filter is located at 2.105 GHz with 3-dB fraction bandwidth (FBW) of 11.9%. It shows that the spurs free upper stopband with 15 dB rejection level can extend to 40 GHz (19f0). The circuit size of this filter is extremely compact, which occupies only 7.35 mm × 7.5 mm.
The aim of this letter is to provide a novel method connecting statistical optimization and information geometry for ship detection in synthetic aperture radar (SAR) imagery. The method consists of two steps: initial detection and iterative optimization. For the first stage, the Weibull clutter model is used for initial detection. For the second step, the metric tensor of the Weibull distribution manifold is constructed for iterative optimization. Experiments show that the proposed method is effective in reducing false alarms and obtains a satisfactory detection performance.
The available polarizers either cannot afford gigawatt-class high-power microwave applications or are large in length. In this letter, a novel grooved polarizer is proposed. The grooves are proposed to be created in an over-mode circular waveguide to improve the power capacity and bandwidth. Moreover, the symmetric elliptical grooves are adopted to suppress high-order modes and realize the desired phase difference. An X-band polarizer prototype is designed and manufactured with length of 91 mm. Simulated results show that the power capacity of the polarizer is more than 1.5 GW. Measured results in accordance with simulations show that the axial ratio is less than 3 dB from 8.6 to 12.2 GHz, with relative bandwidth of 34.6%. The measured return losses are better than -12.7 dB in the same frequency range.
This paper presents a practical scheme for threefold stubs etched on the ground plane (GP) to reduce mutual coupling between adjacent patching elements. The multiple input multiple output (MIMO) antenna array consists of two concentric polyhedron annulus patches, a conventional dielectric substrate, threefold fork-shaped stubs (TFSS) and a microstrip line feeder. The equivalent band-stop filtering function of the TFSS suppressing surface wave propagation has been demonstrated in commercial Advanced Design System (ADS) software. The results of previous case studies indicate that the mutual coupling about 5 dB to 47 dB was reduced from 8 GHz to 9.3 GHz (S11 < -10 dB) for antenna arrays. The capabilities of the antenna (in envelope correlation coefficient = 0.018, voltage standing wave ratio = 1.2892, and diversity gain = 20 dB) have been confirmed in a center frequency of 8.97 GHz. An examination of TFSS antennas shows that the side lobes in both the E-plane and the H-plane descends alongside an increasingly broad radiation pattern. The above results demonstrate that the proposed design is highly efficient in MIMO antenna applications.
In this paper, we experimentally demonstrate the performance of a multi-beam antenna based on inductor-capacitor (L-C) transmission line networks. The lumped element parameters of the antenna are derived according to the mapping relations between the Maxwell's equations and L-C network equations. The simulation results are in good agreement with the measurement ones, and the antenna performs well at a wide bandwidth with high directivity. The antenna has potential applications in future communication systems.
In this study, the physical relationship between the shape parameter v of the K-distribution and the spatial correlation of a sea clutter signal received with a radar is demonstrated through simulation results. The spikiness of the sea clutter is well modeled by the shape parameter v of the K-distribution. According to a well-known empirical formula, the shape parameter v changes with the radar resolution based on a constant power-law relation. However, as with most empirical findings, this finding is valid only for the environmental conditions under which the formula was developed. In other words, the existing power-law models for the shape parameter of the K-distribution for sea clutter do not consider the relative ratio of the cross-range resolution Rc to the spatial decorrelation length Rdec of the sea surface. Our study investigates this relation using statistical simulations based on the principle of superposition for backscattered signals that represent sea clutter within a resolved area on the sea surface. This study shows that the constant factor α in the power-law relation must be modified to a function of the ratio Rc/Rdec. The findings of this study will be useful for the evaluation of detection performance in designing radar systems operating in the maritime environment.
A dual-mode band-pass filter (BPF) for the fifth generation (5G) N78 band applications is proposed based on a 2-layer low temperature cofired ceramic (LTCC) substrate. The proposed BPF is built with a square resonator and two pairs of open-stubs, which suppressed the 2nd-order and 3rd-order 27 and 21 dB, respectively. The proposed BPF not only achieved a size reduction of 50% compared with a single-mode implementation, but also possessed a non-orthogonal input/output (I/O) feeding style, which presents convenient interconnection and integration with neighboring devices. Moreover, the dual-mode BPF does not need a conventional disturbing element to excite two degenerate modes. Comparison and discussion are carried out as well.
In this paper, a three-dimensional (3-D) tunable band-stop frequency selective surface (FSS) with wide tuning range is presented. The proposed tunable 3-D FSS consists of a periodic array of an annular resonator loaded with two varactor diodes. By controlling the reverse voltage of the varactor diodes, the resonance frequency could be tuned in a wide frequency range. Full-wave simulation shows 100% tuning range from 3.0 GHz to 6.0 GHz with respect to lower resonance frequency. The simulated results exhibit stable band-stop performance under different incident angles (up to 45˚). By cascaded two 3-D tunable FSSs, the bandwidth and selectivity performance could be further enhanced. The proposed 3-D FSS with its stable stop-band performance can be a potential candidate to shield the RF signals which is the major source of problem leading to RF device malfunctions.
In this research work, a planar crossed exponentially tapered slot antenna with a multi-resonance function is introduced. The presented antenna design is ascertained on a low-cost Rogers 5870 dielectric with a circular schematic. The antenna is designed to support several frequency spectrums of the current and future wireless communications. The configuration of the design contains a pair of crossed exponentially tapered slots intersected by a star-shaped slot in the back layer and a bowtie-shaped radiation stub with a discrete feeding point extended among the stub parts. The crossed exponential slots exhibit a wide impedance, and the star slot generates an extra resonance at the upper frequencies. For S11 ≤ -6, the antenna provides a wide operation band of 1.7 to 5.9 GHz supporting several frequency bands of 3G, 4G, and 5G communication. The fundamental characteristics of the proposed slot radiator are studied, and good performances have been achieved.