We present the design of an infrared metasurface harvester based on the full absorption concept. The metasurface unit cells consist of an H-shaped resonator with the load placed across the gap of the resonator. Different from infrared metamaterial absorber designs, the resonator is capable of not only full absorption but also maximum energy channeling across the load resistance. Numerical simulation demonstrates that 96% of the absorbed energy is dissipated across the load resistance. In addition, cross-polarized H-resonators design is presented, which is capable of harvesting infrared energy using dual polarizations within three frequency bands.

This paper describes a parallel implementation of the Inverse Fast Multipole Method (IFMM) for multi-bistatic imaging configurations. NVIDIAs Compute Unified Device Architecture (CUDA) is used to parallelize and accelerate the imaging algorithm in a Graphics Processing Unit (GPU). The algorithm is validated with synthetic data generated by the Modified Equivalent Current Approximation (MECA) method and experimental data collected by a Frequency-Modulated Continuous Wave (FMCW) radar system operating in the 70-77 GHz frequency band. The presented results show that the IFMM implementation using the CUDA platform is effective at significantly reducing the algorithm computational time, providing a 300X speedup when compared to the single core OpenMP version of the algorithm.

Range alignment plays an important role in the inverse synthetic aperture radar (ISAR) imaging. The performance of the traditional range alignment algorithms decreases when the migration through resolution cells (MTRC) is much severe. In this paper, a measure of MTRC is defined, and the effect of MTRC on range alignment is analyzed. Taking MTRC into account, a robust sub-integer range alignment algorithm is proposed. Firstly, each range profile is interpolated to remove the precision limitation of integer range resolution cell. Subsequently, the matrix formed by all the range profiles is partitioned into several matrix blocks on the slow-time domain. For each matrix block, the range profiles are aligned by minimizing the entropy of the average range profile (ARP). Finally, the matrix blocks are coarsely aligned using the maximum correlation method, followed by a fine alignment based on the minimization of the ISAR image entropy. The effectiveness of the proposed algorithm is validated by simulations and real-world data. Results demonstrate that the proposed method is robust against MTRC and can reduce the alignment error. The resultant ISAR image is much better focused.

A novel compact wideband dual-polarized printed dipole antenna for base station application is presented. The proposed antenna is composed of four assembled substrates. Two pairs of identical arrow-shaped conductive lines on the tophat substrate form two orthogonal polarized dipoles. Two baluns connected with 50 Ω coaxial cables are integrated on another two vertical substrates to excite the dipoles. The other horizontal board at bottom provides grounding. A rectangular box-shaped reflector is also used to enhance its stability in radiation patterns over the operating frequencies. It achieves 22% size reduction from the conventional printed half-wavelength cross-dipole, and 43.2% impedance bandwidth (VSWR<2), while maintaining a stable radiation pattern with measured Cross-Polarization Degradation (XPD) better than -22dB at boresight and an average peak gain of 8.4 dBi for a 65° Azimuth Beamwidth base station application at 700/800/900 MHz bands. With the scalable miniature structure, it may also find itself suitable for side-by-side multiband Multi-Input Multi-Output (MIMO) or Large-Scale Antenna (LSA) 5G base station applications. A 4x4 array prototype of the LSA is also designed and fabricated, and it achieves 27.8% impedance bandwidth (VSWR<1.5) with well decorrelated element performance and array XPD better than -20 dB across as large as 30° tilting range.

A novel microstrip triplexer with a common crossed resonator and some uniform impedance resonators (UIR) is proposed in this paper. The crossed resonator is theoretically analyzed and proved to be able to resonate at three different frequencies. By using the crossed resonator as the common resonator, a compact structure can be gained as no extra matching network is needed, and the number of the resonator can be reduced effectively. Moreover, a wide stopband is obtained by setting the crossed resonator and UIRs working at the same fundamental frequencies but different higher order resonant frequencies. To demonstrate the design procedure, a triplexer with a third order Chebyshev response in each channel is fabricated and measured. The measured result is in good agreement with the simulated one, showing an attenuation of 20 dB up to 8 times the first channel frequency.

The design and measurement of a novel seamless scanning leaky wave antenna in ridge gap waveguide technology are presented. The impedance matching technique is employed to eliminate the open-stopband (OSB) effect which produces a discontinuity for a seamless scanning leaky wave antenna. Ridge gap waveguide proposed recently is used as the feed structure. The antenna radiates from longitudinal slots of which the leakage constant is designed small to ensure a high directivity. Subsequently, for simplicity, a transition from Ku-band standard waveguide port (WR62) to ridge gap waveguide is designed, which operates within Ku-band with S11 below -15dB. A prototype has been fabricated, and measurements support the simulations obtained by full-wave analysis. The proposed antenna bandwidth is from 12.5GHz to 17.4GHz while seamless scanning is achieved from backward to forward, particularly including broadside radiation. The scanning range is from -9° to 19° with an average gain of 18.3dB.

This paper presents the comprehensive design and analysis of a tri-band bandpass filter (BPF) based on a novel quad-mode defected ground structure resonator (QMDGSR) fed by two 50 Ω microstrip lines under the source-load coupling condition. Four transmission zeros (TZs) are produced in the proposed tri-band bandpass structure with two TZs beside each passband. All the four TZs are thoroughly analysed using equivalent circuit models based on the even-/odd-mode theory, and the corresponding equation for extracting the frequency of each TZ is developed and verified. The bandwidths (BWs) of the 1st and 3rd operating bands are broadened by incorporating the proposed triband bandpass structure with a traditional microstrip stepped impedance resonator (MSIR). Also, two additional TZs are generated due to the coupling between the feeding lines and the newly incorporated MSIR, which significantly result in the passband selectivity improvement. The lower and upper stopband rejections of the fabricated prototype are as high as 83.3 and 43.9 dB, respectively.

A low-radar cross section (RCS) coding metasurface (MS) with properties of absorption and diffusion for both normal and oblique incidences is proposed in this paper. The coding MS is composed of a miniaturized perfect metamaterial absorber (PMA) and a wideband artificial magnetic conductor (AMC) in a shared aperture. In addition, to avoid strong scattering energy appearing at specific directions, genetic algorithm (GA) is adopted to search the optimal layout of the two MS elements. Simulated and experimental results confirm the properties of coding MS and indicate the 6-dB RCS reduction bands under TE- and TM-polarized normal incident that waves are 6.28GHz-9.16GHz and 6.33GHz-9.41GHz, respectively.

By attention to price of microwave components and need to use of them in many applications, the creation of an integrated component which can incorporate the performances of several components in one structure is a necessity. Therefore, in this paper a novel symmetric six-ports multi-functional microwave component is designed and realized. The proposed component consists of two modified half mode substrates integrated waveguide couplers which are joined and a slot which is attained from joined two mentioned couplers. Despite the slot prevents the exciting of higher order modes in proposed component, it divides signal in two parts by exciting middle SIW ports. By exciting each of the ports as input, the component can act as an equal and an unequal 90-degree couplers or power dividers. The proposed component with mentioned conditions covers 23.5% frequency bandwidth with maximum magnitude and phase error of ±0.7 dB and ±0.63 degree, respectively.

Human breast is a heterogeneous medium for microwave signal. Breast cancer detection using microwave imaging is done based on signal scattered by breast tissues at different frequencies. Wave propagation direction is extremely important in heterogeneous medium like human breast. In this paper, the effect of wave propagation direction on the dielectric profile reconstruction is simulated in the presence of noise. X and Y directed transverse electric (TE) waves are considered for numerical breast phantom heterogeneity exploitation. Wave propagating in Y direction results into better dielectric profile reconstruction than X directed wave. Signal to noise ratio is very crucial for microwave imaging because information resides in low power scattered electric signal. Results show that SNR of at least 30 dB is required to detect cancer by solving extremely under-determined system of scattering equations.

An X/Ku-band flat lens antenna based on dual-frequency anisotropic metasurface is proposed in this paper. The function of the anisotropic metasurface is to focus the incident plane waves around 10 GHz and 14 GHz on different spots. Then we place a Vivaldi antenna with its phase centers at 10 GHz and 14 GHz well matching the focal spot of the metasurface at each frequency to build a flat lens antenna. The lens antenna has a peak gain of 18.5 dB and cross-polarization levels of lower than -20 dB at 10 GHz with -1 dB gain bandwidth of 9.8-10.4 GHz, while it has a peak gain of 18.8 dB and cross-polarization levels of lower than -30 dB at 14 GHz with the bandwidth of 13.8-14.2 GHz. Besides single working band, the antenna can simultaneously operate at 10 GHz and 14 GHz with gains of 16.2 dB and 16.5 dB, respectively. Measured results have a good agreement with the simulated ones.

In this work, we present a three-component hierarchical structure to simultaneously improve the red, green, and blue (RGB) light-extraction efficiency (LEE) of white light-emitting diodes (LEDs) based on color mixing method. With the help of 3D finite-difference time-domain (FDTD) simulations, the effects of the embedded photonic crystals (PhCs), the normal surface PhCs, and the nano-rods on the enhancement of RGB light extraction were investigated. The results were compared with those of the conventional planar LEDs and the normal surface PhCs LEDs over the whole visible spectrum. Results from the simulations demonstrated that the maximum LEE for the hierarchical structures LEDs gave 112%, 327%, and 284% RGB LEE enhancement, respectively, compared to that of the conventional planar LEDs, and achieved 104%, 191%, and 187% RGB LEE enhancement compared to that of LEDs with normal surface PhCs. The emission characteristics of the hierarchical structures LEDs were also revealed in detail by FDTD simulations. The results shown in this paper would do a favor for the design and fabrication of high efficiency LEDs.

A novel substrate integrated waveguide (SIW) planar diplexer with very extremely high isolation is presented. It is formed by two quarter mode substrate integrated waveguide (QMSIW) cavity resonators which are designed individually and combined through a T-juction. The diplexer channels are 13% and 15% relative bandwidths at 2.35 GHz and 3.5 GHz, respectively. Inband return losses are better than 22 dB and 25 dB, and the insertion losses are 0.8 dB and 0.5 dB, in the lower and higher channels. The isolation between the two channels is lower than -42 dB, indicating enough isolation between the two channels. The measured results of the fabricated diplexer agree well with the simulated ones.

The high-speed moving of space targets introduces distortion and migration to range profile, which will have a negative effect on three-dimensional (3-D) imaging of targets. In this paper, based on joint parametric sparse representation, a 3-D imaging method for high-speed moving space target is proposed. First, the impact of high speed on range profile of target is analyzed. Then, based on an L-shaped three-antenna interferometric system, a dynamic joint parametric sparse representation model of echoes from three antennas is established. The dictionary matrix is refined by iterative estimation of velocity. Moreover, an improved orthogonal matching pursuit (OMP) algorithm is proposed to recover interferometric phase information. Finally, with the phase information, interferometric processing is conducted to obtain the 3-D image of target scatterers. The simulation results verify the effectiveness of the proposed method.

A self-contained electromagnetic theory is developed on a simplicial lattice. Instead of dealing with vectorial field, discrete exterior calculus (DEC) studies the discrete differential forms of electric and magnetic fields, and circumcenter dual is adopted to achieve diagonal Hodge star operators. In this paper, Gauss' theorem and Stokes' theorem are shown to be satisfied inherently within DEC. Many other electromagnetic theorems, such as Huygens' principle, reciprocity theorem, and Poynting's theorem, can also be derived on this simplicial lattice consistently with an appropriate definition of wedge product between cochains. The preservation of these theorems guarantees that this treatment of Maxwell's equations will not lead to spurious solutions.

In magnetic induction communication systems, channel capacity is often a major bottleneck that limits the system performance. This paper proposes a method to increase the channel capacity in such systems by means of an antenna array. A central challenge in the design of magnetic antenna arrays is to achieve low intra-array coupling along with high gain. These two properties are essential for increasing the channel capacity in comparison to single antenna communication systems of comparable volume. The method proposed in this paper utilizes circular loop antennas to reduce the intra-array coupling using magnetic flux cancellation. The mathematic approach employed in this paper considers each coil as a system of coupled inductors, where each inductor is a single turn loop, and the total coil self and mutual inductances are computed by summing the appropriate single turn loop inductances. Volume efficient coil topologies are identified, and an optimization method is proposed to minimize the intra-array coupling, subject to a required inductance. The proposed method allows to design volume efficient, up to 3×3, array, or pyramidal shaped 4×4 arrays. The results are verified experimentally using the multiple-frequency communication mode.

In this work, different configurations of electrically reconfigurable radial waveguides are presented: a configuration with pass/stop regions, a configuration with tunable narrowband filters and a configuration with integrated phase shifters. Potential applications for the different configurations are also proposed. First, the design and experimental results for a reconfigurable radial waveguide using PIN diodes and operating in the band 5.2-5.8 GHz (11%) are presented and discussed. Then, the principle of radial waveguide with tunable narrowband filters using varactors is described and an application for Frequency Modulated Continuous Wave (FMCW) radars is proposed. Finally, a new radial-line slot array antenna with electrically beam-steering ability is proposed.

This paper presents a novel, Genetic Algorithm (GA) optimized X-band absorber using metamaterials. The unit cell of this structure consists of several square patches, each having a dimension of 2.5 mm x 2.5 mm. Their positions are optimized using the GA such that the X-band absorption is maximized. Simulation results and the subsequent experimental validation affirm that the structure offers absorption of 97% from 10.42 GHz to 11.98 GHz and absorption of 90% over the entire X-band from 8 GHz to 9 GHz and also from 9.35 GHz to 12 GHz, with peak absorption of 99.95% at 10.52 GHz. The results are compared with the existing ones, to demonstrate the superiority of the proposed design.

A filtering antenna based on a dumbbell-shaped resonator is proposed, fabricated and measured. A Γ-shaped antenna and the proposed dumbbell-shaped resonator are used and integrated to be a filtering antenna. The Γ-shaped antenna which acts as a radiator is excited by a coupled line. Measured results show that the filtering antenna achieves an impedance bandwidth of 6.7% at a reflection coefficient |S₁₁| < -10dB and has a gain of 1.35 dBi. Moreover, a radiation zero occurs at 3.1GHz. Compared with the characteristics of fundamental Γ-shaped antenna, the design of the dumbbell resonator has little impact on antenna's radiation patterns. In addition, to explain the mechanism of filtering antenna, the analysis of surface current distribution on patch is given. The size of filtering antenna is 0.33λ0×0.17λ₀ (λ₀ is the free-space wavelength at 2.45 GHz). Compared to other recent works, a simpler structure and more compact size are the key features. Owing to the operating bandwidth and the characteristic of filtering, the proposed antenna can be used in modern wireless communications systems.

Fragment-type structure has been used to design antennas and microwave circuits. Special optimization technique, including optimization algorithm and EM software (electromagnetic) simulator, is necessary for the design of this kind of structure. In this paper, a novel optimization technique, MOEA/D-GO+FDTD, is proposed, where MOEA/D-GO (multiobjective evolutionary algorithm combined with enhanced genetic operators) serves as the optimization algorithm and Finite-Difference Time-Domain (FDTD) method serves as the electromagnetic simulator. As an example, a compact bandpass microstrip filter is designed by using MOEA/D-GO+FDTD. Firstly, numerical simulation of the fragment-type microstrip filter by using FDTD method is investigated. Secondly, a microstrip filter operating at 3.8GHz-6.5GHz is designed through optimizing return loss, insertion loss, and out-of-band rejection. Finally, comparison of the computational costs between different electromagnetic simulators verifies high efficiency of the proposed MOEA/D-GO+FDTD.