In this paper, we study the optimization of two tilt angles corresponding to two antenna arrays in each base station (BS) of a massive multiple-input multiple-output system. We consider two scenarios with perfect channel state information (CSI) and imperfect CSI. In the limit of the number of the BS antennas, the channel orthogonality is employed to derive the limit and the lower bound of the throughputs. By maximizing the lower bound or the limit throughput, the two antenna tilt angles are optimized. Simulation results show that the throughput performance can be improved with the designed tilt angles.
In this paper, parallel coupled meander lines (PCML) composite right/left-handed transmission line (CRLH-TL) based symmetrical quasi-0 dB coupled-line coupler is presented. Proposed coupler shows measured backward wave coupling level of 0.81 dB at frequency of 6.17 GHz with 3 dB fractional bandwidth (FBW) of 12.64%. Throughout the 3 dB frequency range (5.78–6.56 GHz), isolation and insertion loss of the coupler is better than 24 dB. Overall size of the proposed coupler is 19.6 × 12.1 mm. An equivalent lumped LC circuit model of the coupler is demonstrated. Measured results of the coupler show good agreement with the electromagnetic (EM) simulated and lumped LC circuit model simulated results, which validates proposed coupler design and its performance.
Miniaturizing the microwave circuits for micro-satellite platform has been one of the development trends in microwave remote sensing. A novel 89/118/166/183 GHz frequency dividing network is proposed in this paper which includes two stages: the first stage is an F-G band diplexer that separate 89/118 GHz signals from 166/183 GHz signals. The measured typical transmission loss is 1.5 dB from 83.75 to 124 GHz at one output port as well as 1dB from 141 to 190 GHz at another output port. The second stage contains two diplexers based on waveguide circuit to separate the signals further. The measured typical transmission loss is 0.5 dB for the 89/118 GHz diplexer and 1 dB for the 166/183 GHz diplexer. The above-mentioned frequency dividing network has a vast application prospect due to compact structure and good performance.
The all-optical logic gates have become an important key enabling in optical integrated circuits and find applications in optical networks. In this paper, we introduce new complete series of optical logic gates using photonic crystals. These designs formed by compilation with interference based defect and resonance phenomenon. The proposed work based on two dimensional square lattices by putting gallium arsenide (GaAs) rods immersed on air background. The maximum contrast ratio and the maximum working bit rates is obtained for the NOT/XOR and OR logic gates equal to 50.81 dB and 12.5 Tb/s, respectively. The simulation and optimization of structure is approved out using Finite-Difference-Time-Domain (FDTD) method and Plane Wave’s Method (PWEM).
A low profile Circular Microstrip Patch Antenna (CMPA) with radius 5 mm has been designed to generate two resonant frequency bands that can be used for WLAN 5.2 (5.15–5.25) GHz, Wi-Fi (5.725–5.850) GHz and Dedicated Short-Range Communications (DSRC) (5.85–5.925) GHz application bands. The designed antenna has been slitted with two slits and a stub has also been attached resulting in an additional resonant band alongside the primary resonant band. Also, primary resonant frequency shifted from 7.22 GHz to 5.87 GHz yielding about 18.7% antenna miniaturization. Frequency bands generated by the designed antenna are (5.15–5.25) GHz and (5.71–6.01) GHz having peak gain 2.3 and 4.9 dB with broadside radiation pattern. A square shape FR4 substrate having dimension 32 × 32 × 3.2 mm3 and very thin copper sheet for radiating patch and ground has been used in the proposed antenna, which can fulfill the requirement of smaller antenna with dual band application. Simulation software HFSS ver.13 has been used to design and analyze the proposed antenna. Very good matching has been obtained between simulated and measured results.
In this paper a wideband, flexible, and novel structured double negative (DNG) metamaterial is designed for S, C, X, and Ku microwave applications. The 12 mm × 12 mm sized metamaterial is fabricated on a flexible FR4 substrate with thickness 0.25 mm. The metamaterial shows a total wide DNG region of 8.2 GHz (3.8–4.3 GHz and 6.8–14.5 GHz). The transmission coefficient of the unit cell has a total band gap bandwidth of 8.3 GHz from frequency range 2 to 16 GHz. The designed metamaterial also exhibits an extra-large and continuous negative refractive index (NRI) bandwidth of 13 GHz (2–15 GHz). The stop band regions along with DNG and NRI regions individually cover S, C, X, and Ku microwave regions. The complete analysis is done using CST microwave studio. The simulated and measured transmission coefficient curves of the proposed metamaterial are in good agreement. The structure is simple, cost effective, flexible, light weight, and wideband covering S, C, X, and Ku microwave spectra.
In this paper a Quad-band diversity antenna with a small size of 48 × 28 × 0.8 mm3 printed on FR4 substrate is presented that consists of two same pentagonal-shaped patch elements. Four arc-shaped slots in the radiating elements are introduced to obtain the quad-band operation with good return loss. The antenna is designed for covering 5.91 GHz in IEEE 802.11 b/g/n standards, 7.40 GHz in C-Band, 9.18 and 10.72 GHz in X-Band. To achieve the lowest coupling between two elements, three structures for embedding elements are investigated. The prototype is fabricated, and measured results are in good agreement with simulated results. The final antenna accomplishes a weak mutual coupling below −29.2 dB in the all operational bands. Radiation characteristics, radiation efficiency and diversity performance such as diversity gain and envelope correlation coefficient of the final structure, are presented.