Using impulse response with a 3D algorithm is a novel free-space radiation pattern reconstruction technique with accuracy greater than 1 dB in all antenna under test (AUT) azimuth and elevation angle orientations inside a non-anechoic environment. A quantitative comparison between impulse response with a 3D algorithm and impulse response with 2D, a previous technique, is performed using quantifiers. Benefits of the proposed 3D free-space radiation pattern reconstruction algorithm are single-frequency characterization and reuse of the 3D impulse response of the environment.

This paper presents a hybrid design of Sierpinski Carpet and Minkowski antenna for wireless applications. The hybrid antenna is designed, simulated and fabricated on an FR4 substrate with thickness 1.6 mm and dielectric constant 4.4. The dimensions of antenna are 45 x 38.92 x 1.6 mm³ which operates at various frequencies 3.43 GHz, 4.78 GHz, 6.32 GHz, 8.34 GHz and 9.64 GHz, and can be used for WiMax, C-band applications, Point-to-point Hi speed wireless communication and X-band (satellite Communication) applications. The measured results are also compared with the simulated ones which are in agreement with each other. Ansoft High Frequency Structure Simulator (HFSS) is used to design and simulate the antenna.

A backscattering model of the average signal power function (SPF) for laser radar 3D range imagery obtained using detector arrays for a complex target with rough surfaces is presented. The model relates the average power at the receiver to the laser pulse, target shape, optical scattering properties of the surface materials, angle of incidence, and other factors. The optical scattering properties of the material are characterized using the bidirectional reflectivity distribution function (BRDF). The effects of the pulse width on the resolution of the 3D range imagery are analyzed. The proposed model can be used to demonstrate 3D laser radar systems and can also be used to generate a library of model data sets for automatic target recognition (ATR) applications.

The study of electromagnetic field coupling to an electrically large structure is essential, in order to assess the degree of protection to be provided to harden the electronic or electrical system of interest, against electromagnetic fields. The electromagnetic field coupling study can be done by computational and experimental techniques. In this paper, we have studied the high altitude electromagnetic pulse (HEMP)electromagnetic field coupling to a large antenna structure using electromagnetic dimensional scale modeling approach, in the frequency range of 1 kHz to 100 MHz. This frequency range has been chosen because most of the energy of the HEMP lies in this frequency band [1].

Hybrid analog/digital precoding is a promising technology that reduces the hardware complexity and power consumption of large-scale millimeter wave (mmWave) multiple-input multipleoutput (MIMO) communication systems. Most prior work has focused on hybrid precoding for narrowband mmWave systems. MmWave systems, however, will likely act on wideband channels with frequency selectivity. Therefore, this paper presents an effective OFDM-based hybrid precoding algorithm (named as W-LS-IR algorithm) for wideband mmWave systems. Firstly, the initial phases of the analog precoding matrix are randomly generated, and the digital precoding matrix is initialized via the least squares (LS) method. Then, the column of the analog precoding matrix is derived from the dominant left singular vector of a residual matrix, and the corresponding row of the digital precoding matrix is updated using the LS method. Through the iterations of the aforementioned stage, the hybrid precoding matrix will approach a stable solution finally. Compared with related works, the proposed algorithm can improve the spectral efficiency of wideband mmWave MIMO communication systems. Simulation results are presented to confirm the efficiency of the proposed algorithm.

High frequency electromagnetic (EM) scattering analysis from the electrically large scatterers is important to the computational electromagnetics community. Meanwhile, the high frequency diffraction technique, like the uniform geometrical theory of diffraction (UTD), is very important when the observation point lies in the transition, shadow and deep shadow regions of the considered scatterer. Furthermore, the diffracted fields arising from the electrically large scatterers via the UTD technique are usually highly oscillatory in nature, which is named as the Fock type integrals with the Airy function and its derivative involved. In this work, we propose a Fourier quadrature method to calculate the Pekeris integrals. Moreover, we first adopt the Fourier quadrature technique to calculate the diffracted fields from the dielectric convex cylinder with impedance boundary conditions, like the creeping wave fields and NU-diffracted wave fields. On invoking the Fourier quadrature method, the results of total scattered fields at the fixed observation points could achieve 1 dB relative errors. Moreover, numerical results demonstrate that the computational efforts for the oscillatory Pekeris-integrals are independent of wave frequency with the fixed sampling density and integration limit.

In this letter a four-port multi-input-multi-output (MIMO) antenna for 5G applications is proposed. This antenna is compact with a size of 11.3 mm×31 mm excluding feed lines. The radiation patterns of the antenna show pattern diversity in the azimuthal plane, and each antenna element has an end-fire gain about 10 dBi by employing an array of metamaterial unit cells. The isolation between the antenna elements with edge to edge separation <λ₀/5.5 at 28 GHz is enhanced by trimming the corners of the rectangular high refractive index metamaterial region along with a ground stub between antennas. The proposed antenna is fabricated, and each antenna element has return loss, S_nn<-10 dB with isolation, S_nm>21 dB in the frequency range 26 GHz to 31 GHz, which makes this antenna potential candidate for MIMO application at 28 GHz band enabling 5G cellular communications.

This paper presents a compact high-isolation dual-polarized dipole antenna with an artificial magnetic conductor (AMC) reflector. The proposed antenna is composed of a radiating element, two short pins and a 7×7 AMC array. By introducing two short pins, the port isolation is lower than -33 dB in the whole band on two ports. With the ring and AMC reflector, the dimension of the proposed antenna is only 0.36λ₀×0.36λ₀×0.16λ₀ at 2.2 GHz. The antenna also achieves a 10-dB return loss bandwidth from 1.6 to 2.78 GHz (54%) for both ports. The gain of the proposed antenna is around 8 dBi, and the cross-polarization is about 30 dB. Due to these properties, the proposed antenna can be applied to 2G/3G/long term evolution (LTE) base station and WLAN/WiMAX applications.

This piece of work replicates on the antenna array thinning exploring the benefits of known Fourier Analysis. In this communication Fourier transform is applied to the synthesis of periodic arrays for minimizing the Peak Side Lobe (PSL) level and thereby enhancing the directivity. Furthermore, the concept of Fill Factor(degree of thinning) i.e, reduction in the number of active elements is experimented for the above said objective. The proposed methodology is workedout on periodic linear and planar arrays. Numerical study and simulation results are composed with array thinning designs from literature. The analysis demonstrates the superiority of the illustrated Fourier technique.

In this paper, an ultrathin egg-shaped microbubble was proposed and analyzed for pressure sensing firstly, which was fabricated by utilizing an improved pressure-assisted arc discharge technique. By tailoring the arc parameters and the position of glass tube during the fabrication process, the thinnest wall of the fabricated microbubble could reach 873 nm. Such an ultrathin film structure is very suitable for pressure sensing. Especially, as only a commercial fusion splitter and pressure pump were utilized to achieve such functions, the fabrication cost was very cheap. The fiber Fabry-Perot (FP) interference technique was used to analyze its pressure sensitivity by filling the inner wall of the microbubble with different air pressures. The experiment results depicted that the end face of microbubble expands with the increase of the filling pressure. The pressure sensitivity of such an egg-shaped microbubble could reach up to 14.3 pm/kPa in terms of interference spectrum shift, while the maximum cavity deformation sensitivity of the microbubble vs. pressure could reach up to 0.334 nm/kPa in terms of cavity length change. Besides, the maximum sensitivity vs. temperature was only 27.83 pm/˚C. Results of this study could be good reference for developing new pressure sensors with low cost, high sensitivity and good anti-temperature interference abilities.

In this letter, a new wideband circularly polarized antenna for Radio Frequency Identification (RFID) readers is proposed. A prototype operating in the Ultra-High Frequency (UHF) band is successfully realized and tested using a defected Ground Structure (DGS). This antenna consists of an L-shaped metal strip and a DGS with four tuning stubs. The overall size covers 90*90*1.6 mm³. The measured -10 dB reflection coefficient S₁₁ bandwidth is 27% (800-1020 MHz) and a good radiation pattern and suitable gain coefficient about 3.7 dB have been achieved. Also, an excellent agreement was noticed between simulation and measurement results demonstrating the good performance of the proposed antenna.

In this paper, a simple and compact tri-band multiple-input-multiple-output (MIMO) antenna for wireless applications is proposed. The antenna is composed of two symmetric monopoles placed a distance of 0.106λ₀ and occupies 0.26λ₀×0.25λ₀ board area. The tri-arm monopole offers operation over 2.1-2.7 GHz, 3.3-3.7 GHz and 4.9-5.35 GHz with percentage impedance bandwidth of 25%, 11.4% and 8.7%, respectively. An isolation greater than 20 dB is achieved by integrating a stub in the ground plane and adding a stub in the feed line. The structure exhibits stable gain and radiation patterns. Various performance metrics including envelope correlation coefficient (ECC), diversity gain (DG) and mean effective gain (MEG) are measured.

A new miniaturized microstrip lowpass filter with compact size and a wide spurious-free stopband is investigated. To achieve compact design and ultra-wide band rejection, both triangular patch resonators and trapezoid patch resonators are introduced in the filter. To further reduce the circuit size of the filter, the meander transmission line is also adopted in the design. A demonstration filter with 3 dB cutoff frequency at 0.76 GHz has been designed, fabricated and measured. Results indicate that the proposed filter is able to suppress the 16th harmonic response referred to a suppression degree of 15 dB. Furthermore, the proposed filter exhibits a small size of 0.080λ_g×0.072λ_g, where λ_g is the guided wavelength at 0.76 GHz.

Space-time adaptive processing (STAP) for airborne radar employs training samples to estimate clutter covariance matrix (CCM). However, the target-like signals contained in the training samples severely corrupt the accuracy of the CCM. This paper proposes a novel non-homogeneous STAP algorithm for target-like signal elimination based on reduced-dimension sparse reconstruction (RDSR) to overcome this issue. The proposed algorithm exploits the high-resolution angle-Doppler spectrum obtained by RDSR to estimate and eliminate target-like signals. Theoretical analysis and simulation results show that the proposed algorithm effectively suppresses clutter and improves the performance of STAP in non-homogeneous environments.

A main defect of far-field (FF) measurement techniques is long measurement time, which often leads to the problem of inefficient use of measurement facilities that is a strong limiting factor in many measurements. To solve this problem, in this study, we propose a technique to accelerate the antenna measurement that is achieved by sparse test results in the FF measurement system. In the data processing part of the measurement, the concept of the quadrature analog-to-information conversion (QAIC), which make the approach both efficient and easy to implement in existing FF measurement facilities, is discussed. Simulations are provided to show this low-speed uniform sampling approach. The proposed strategy is then applied to measure the pattern of a standard rectangular horn antenna in an anechoic chamber. The experimental results demonstrate that our technique can reduce the measuring time by at least 34.4% while guaranteeing the measurement accuracy. These results demonstrate the potentials of the method.

In this paper, a stub-loaded penta-mode resonator (PMR) with its analysis, characterization and applications for bandpass filter (BPF) is presented. Even-/odd-mode analysis method is employed to analyze the PMR which exhibits five transmission poles (TPs) and three inherent transmission zeros (TZs). By changing the dimension parameters of the resonator, TPs and TZs can be flexibly controlled, and wideband/dual-wideband/tri-band BPF has been designed successfully utilizing the same configuration. For validation, all these three filters are fabricated and measured, and the measured results are in good agreement with the simulated ones.

Minimum variance distortionless response (MVDR) beamformer is an adaptive beamforming technique that provides a method for separating the desired signal from interfering signals. Unfortunately, the MVDR beamformer may have unacceptably low nulling level and high sidelobes, which may lead to significant performance degradation in the case of unexpected interfering signals such as the rapidly moving jammer environments. Via support vector machine regression (SVR), a novel beamforming algorithm (named as SVR-CMT algorithm) is presented for controlling the sidelobes and the nullling level. In the proposed method, firstly, the covariance matrix is tapered based on Mailloux covariance matrix taper (CMT) procedure to broaden the width of nulls for interference signals. Secondly, the equality constraints are modified into inequality constraints to control the sidelobe level. By the ε-insensitive loss function for the sidelobe controller, the modified beamforming optimization problem is formulated as a standard SVR problem so that the weight vector can be obtained effectively. Compared with the previous works, the proposed SVR-CMT method provides better beamforming performance. For instance, (1) it can effectively control the sidelobe and nullling level. (2) it can improve the output signal-to-interference-and-noise ratio (SINR) performance even if the direction-of-arrival (DOA) errors exist. Simulation results demonstrate the efficiency of the presented approach.

This paper presents two novel substrate integrated waveguide (SIW) diplexers with transmission zeros placed below and above the passband. Diplexer I is based on two bandpass filters (BPFs) using eighth mode SIW (EMSIW) cavities with Rx and Tx frequencies at 3.68 GHz and 6.09 GHz. The second one is operated at 2.37 GHz and 6.04 GHz using EMSIW and thirty-second SIW (TMSIW) cavity. The diplexers are all combined through a T-junction by carefully choosing the length and width of two branches to allow each filter to match the antenna, while maintaining an open circuit at the middle band of the other. The proposed diplexers possess compact size, because of the EMSIW and TMSIW cavity. The diplexers are fabricated in SIW technology. The minimum insertion losses including SMA connectors are measured to be 1.39/1.61 dB and 0.38/0.85 dB. Meanwhile, the diplexers exhibit 37 dB and 42 dB isolations between the channels, respectively. Good agreement is achieved between simulated and measured results.

This paper presents a direct matrix synthesis for in-line diplexers constructed by general Chebyshev channel filters. The finite transmission zeros of the channel filters are generated and independently controlled by a set of frequency-variant couplings (FVC) sections. The network only involves resonators cascaded one by one without any auxiliary elements (such as cross-coupled or extracted-pole structures), and this paper provides the best synthesis solution in configuration simplicity for narrowband contiguous diplexers. For the channel filters, considering both the couplings and capacitances matrices of a traditional low-pass prototype, a generalized transformation on the admittance matrix is introduced as the basis of the synthesis, which allows more than one cross-coupling to be annihilated in a single step, while generating an FVC section simultaneously. Two examples of diplexer are synthesized to show the validation of the method presented in this paper.

In a recently published report, Sen and Das [5] proposed a frequency tunable low-cost microwave absorber to obtain tunable absorption spectra. In this paper, we justify that the proposed device is not an absorber. It is observed that the total absorption rates merely reach 2% and 14.85% for the air gaps of 3.5 mm and 7.5 mm, respectively, when the co- and cross-polarization reflections are taken into account in the reported device. Obviously, The original authors erroneously consider a polarization converter as an absorber, and the obvious errors can be found in their paper.