This article proposes a very compact planer openloop bandpass filter (BPF) with asymmetric frequency response and covering the 2.5 to 2.6 GHz and 3.6 to 3.7 GHz spectrum for 4G and 5G applications, respectively. The microstrip BPF employs four open-loop ring resonators with 50 Ω tapped lines for input and output ports. To achieve sharper cut-off frequencies, one infinite and three finite transmission zeros are successfully generated on the upper and lower edges of the 4G and 5G passbands. The utilization of the planer four-section resonators not only reduces the size of the structure, but also provides either positive or negative cross-coupling. The crosscoupling coefficients between the resonators are optimized to resonate at the required frequency with proper bandwidth. The reported BPF is designed and optimized using CST software, and is implemented on a Rogers RO3010 substrate with a relative dielectric constant of 10.2 and a very compact size of 11×9×1.27 mm 3 . Good agreement is achieved between the simulated and measured results.

This paper proposes a new low complexity angle of arrival (AOA) method for signal direction estimation in multi-element smart wireless communication systems. The new method estimates the AOAs of the received signals directly from the received signals with significantly reduced complexity since it does not need to construct the correlation matrix, invert the matrix or apply eigen-decomposition, which are computationally expensive. A mathematical model of the proposed method is illustrated and then verified using extensive computer simulations. Both linear and circular sensors arrays are studied using various numerical examples. The method is systematically compared with other common and recently introduced AOA methods over a wide range of scenarios. The simulated results show that the new method has several advantages in terms of reduced complexity and improved accuracy under the assumptions of correlated signals and limited numbers of snapshots.

A new differential-fed wideband dual-polarized microstrip filtering antenna exhibiting high gain, and high common-mode rejection is presented in this paper. The presented antenna is composed of a square patch radiator mounted on a substrate integrated waveguide (SIW) cavity. The structure is excited by two differential pairs of feeding probes providing differentially exciting signals. The filtering response is achieved by introducing symmetrical defected ground structures (DGS) in the ground layer surrounding the four excitation ports for dual-polarized antenna. The DGS is optimized to introduce nulls at the high and low edges of the passband transmission maintaining high gain and wide bandwidth. Because of the symmetric geometry of the proposed antenna, the design is studied and analyzed in one polarization mode, while the performance for the second mode will be identical. The filtering antenna is simulated and optimized using finite element solver software (CST & HFSS). Good performance is obtained with wide bandwidth of 11%, realized gain of 8 dBi at the resonant frequency (3.5 GHz) and low crosspolarization level due to the differentially driven ports, and complete symmetry using SIW technology. Also, the antenna has a single layer substrate with a height of 0.035 of the free space wavelength and operating at the sub-6 GHz 5G spectrum.

Several works show that the linear Angle of Arrival (AoA) methods such as Projection Matrix (PM) have low computational complexity compared to the subspace methods. Although the PM method is classified as a subspace method, it does not need decomposition of the measured matrix. This work investigates the effect of the sampled columns within the covariance matrix on the projection matrix construction. To the authors' knowledge, this investigation has not been addressed in the literature. Unlike the subspace methods such as Multiple Signal Classification (MUSIC), Estimation of Signal Parameters via Rotational Invariance Technique (ESPRIT), Minimum Norm, Propagator, etc., which have to use a specific number of columns, we demonstrate this aspect is not applicable in the PM method. To this end, the projection matrix is formed based on a various number of sampled columns to estimate the arrival angles. A theoretical analysis is accomplished to illustrate the relationship between the number of the sampled columns and the degrees of freedom (DOFs). The analysis shows that with the same aperture size, the DOFs can be increased by increasing only the number of sampled columns in the projection matrix calculation step. An intensive Monte Carlo simulation for different scenarios is presented to validate the theoretical claims. The estimation accuracy of the PM method, based on the proposed selected sampling methodology outperforms all the other techniques with less complexity compared to the Capon and MUSIC methods. The estimation accuracy is evaluated in terms of Root Mean Square Error (RMSE) and the Probability of Successful Detection (PSD). The results are presented and discussed.

A modified indoor path loss prediction model is presented, namely, effective wall loss model. The modified model is compared to other indoor path loss prediction models using simulation data and real‐time measurements. Different operating frequencies and antenna polarizations are considered to verify the observations. In the simulation part, effective wall loss model shows the best performance among other models as it outperforms 2 times the dual‐slope model, which is the second best performance. Similar observations were recorded from the experimental results. Linear attenuation and one‐slope models have similar behavior, the two models parameters show dependency on operating frequency and antenna polarization.