Average Transmission Coefficient Research Articles

Transmission Coefficient-Based Monitoring of Microwave Ablation: Development and Experimental Evaluation in Ex Vivo Tissue.

To assess the feasibility of monitoring transient evolution of thermal ablation zones with a microwave transmission coefficient-based technique. Microwave ablation was performed in ex vivo bovine liver with two 2.45 GHz directional antennas. A custom apparatus was developed to enable periodic switching between "heating mode" when power from the generator was coupled to the antennas, and "monitoring mode", when antennas were coupled to a network analyzer for broadband transmission coefficient ( s21) measurements. Experiments were performed with applied powers ranging between 30-50 W per antenna for 53-1219 s. Transient s21 spectra over the course of ablations were analyzed to determine feasibility of predicting extent of ablation zones and compared against ground truth assessment from images of sectioned tissue. A linear regression-based mapping between the two datasets was derived to predict ablation extent. Normalized average transmission coefficient initially rapidly decreased and then increased before asymptotically approaching steady state, with the transition time ranging between 53 s (45 W) and 109 s (30 W). Analysis of ground truth ablation zone images indicated time to complete ablation of 230-350 s. The relative prediction error for time to complete ablation derived from the s21 data was in the range of 1.6%-2.3% compared to ground truth. We have demonstrated the feasibility of monitoring transient evolution of thermal ablation zones using microwave transmission coefficient measurements in ex vivo tissue. The presented technique has potential to contribute towards addressing the clinical need for a method of monitoring evolution of thermal ablation zones.

Investigation of Gliding Walled Multilayer Waveguides

This article suggests a new waveguide design that utilizes a “walled” architecture. Instead of relying on conventional gap waveguide structures to create electronic bandgaps and prevent field leakage, the proposed design introduces a “walled” guiding mechanism. This technique preserves transmission while maintaining the multilayer approach and eliminates the need for nails or chemical bonds to attach the layers. Simulations were carried out in the W-band (75–110 GHz) and D-band (110–170 GHz) using several metals, and measurements were performed in the W-band using aluminum. The simulation results show that the reflection coefficient was less than −40 dB over the entire D-band. At the same time, the average insertion loss was around 0.0054 dB/mm and around 0.0065 dB/mm for silver and gold, respectively. Similarly, the reflection coefficient was less than −45 dB over the 75–110 GHz range, with an average insertion loss of 0.0018 dB/mm for silver and 0.003 dB/mm for gold, respectively. The aluminum model’s reflection coefficient was less than −35 dB, and the average insertion loss was 0.0035 dB/mm. The experimental results achieved a reflection coefficient of less than –30 dB and the average transmission coefficient was −0.2 dB, with an insertion loss of 0.002 dB/mm. The simple stacking ability of the weightless walled metal plates and easy fabrication makes the proposed transmission line a promising technology in mmWave and Terahertz applications.

Simulation of a Wave Hydrodynamic Numerical Model on a Single Vertical Porous Breakwater

One of the problems in the coastal area is a change in the coastline in the form of a coastline retreat which results in the loss or damage of infrastructure and settlement facilities caused by extreme sea wave activity. One way to anticipate this problem is to build a breakwater. This research is focused on the effect of porosity and freeboard on the transmission and reflection of waves in a single vertical porous breakwater. Numerical modeling was done using a 3D Numerical Wave Tank (NWT) based on Smoothed Particle Hydrodynamic (SPH). The numerical model results show that the average transmission and reflection coefficients are 0.58 and 0.42. In addition, it can be seen that the freeboard and porosity influence the value of the transmission and reflection coefficients. Generally, the smaller the freeboard, the greater the transmission coefficient and the smaller the reflection coefficient. Meanwhile, the greater the porosity, the greater the transmission coefficient, and vice versa, the smaller the reflection.

Performance Analysis of STAR-IRS Aided NOMA Short-Packet Communications With Statistical CSI

We analyze the benefits of simultaneous transmitting and reflecting intelligent reflecting surfaces (STAR-IRSs) for short-packet communications (SPC) with non-orthogonal multiple access (NOMA) and statistical channel state information towards ultra-reliable and low-latency communications. Considering Rician fading and energy splitting protocol, we analyze the performance of STAR-IRS aided NOMA SPC systems with continuous and discrete phase shifts. We first derive new closed-form expressions for the average block error rate (BLER) and diversity order in the finite signal-to-noise ratio (SNR) regime. We then determine the relationship among the average BLER, power allocation, blocklength, and transmission and reflection coefficients. Finally, Monte Carlo simulations are used to verify our theoretical analysis and examine the optimal transmission and reflection coefficients that minimize the common blocklength in the considered system under reliability constraints.

Two-dimensional collisional particle model of the divertor sheath with electron emissive walls

A novel two-dimensional particle-in-cell (PIC) code, named Divertor Edge Simulator of Plasma-wall Interaction with Consistent COllisions (DESPICCO) and developed at CNR-ISTP, is capable of simulating the thin plasma layer of several millimeters, adjacent to the divertor tiles of a Tokamak fusion reactor. Here, kinetic effects and non-neutral plasma physics in the Debye sheath can be self-consistently captured by the PIC approach. The code is firstly benchmarked against literature one-dimensional codes and additional theoretical predictions for a magnetized sheath. Then, it is applied to a realistic divertor scenario featuring an attached plasma with monoblocks (MBs) radial misalignment and gaps, to compute the energy flux amplification factor at the exposed MB edge. A non-ambipolar local current density close to the leading edge and an average sheath heat transmission coefficient larger than the one predicted by classical sheath theory, are found. The effects of electron wall emission and plasma-gas collisions on the ion Mach number and on particle and energy fluxes to the walls are finally estimated to determine future guidelines for simulations. Ion collisions with recycled neutrals and both secondary and thermionic electron emission from the wall are found to have a relevant impact, with the overall effect of reducing by 25% the average ion impact energy, and by 15%–20% the total heavy particles energy flux to the walls, with relevant implications on the divertor wall erosion.

Numeričko modeliranje hidrodinamičke izvedbe na poroznom kosom tipu plutajućeg lukobrana

A breakwater is a coastal building that aims to break up or withstand wave energy that enters the beach so that the characteristics of the incoming waves are by calculations and can reduce abrasion on the shoreline. Designing a floating breakwater is very complicated because it depends on many aspects. These fundamental aspects depend on each other, so if one of these aspects changes, the integrity of the floating breakwater structure will also change. One of these aspects is the magnitude of the transmission and reflection coefficients generated by the floating breakwater. This research will study the hydrodynamic performance of floating breakwater due to variations in slope and porosity in reducing and reflecting waves with computational fluid dynamics (CFD). The slope-porous floating breakwater dimension is based on previous experimental data, including a constant water depth of 0.75 m, a wave height of 0.05 - 0.125 m, and a wave period of 1.1 - 2 sec on regular waves. The results of the numerical model validation and experiments on all variations of the floating breakwater model are quite good, which is less than 10% for both wave transmission and reflection. Analysis of the influence of changes in the mooring line angle, the simulation is carried out at an angle of 30 deg to 90 deg and produces an average transmission coefficient of 0.79 and a reflection of 0.21. While the effect of changes in water level elevation (0.85 m, 0.75 m, and 0.65 m) gives a reasonably significant average transmission coefficient of 0.85 and a reflection of 0.13. The mooring line angle will be gentler at high tide, and the transmission and reflection coefficients will be higher. However, the mooring line will loosen at low tide, causing the structure to move more freely and eliminating the function of the floating breakwater itself so that the tidal phenomenon becomes a challenge for coastal experts in designing structures to produce effective and efficient hydrodynamic performance.

Miniaturized 4 × 4 switched-beam Butler Matrix with bandwidth enhancement for 5G communication system

A 4 × 4 Butler Matrix (BM) without phase shifter is proposed to provide bandwidth enhancement and size reduction by removing a conventional 0 dB/90° crossover, two 0° phase shifters and two 45° phase shifters. Two proposed 3 dB/45° patch couplers replace the combination of two conventional 3 dB/90° branch-line couplers and two 45° phase shifters, whilst a modified 0 dB/0° crossover removes two 0° phase shifters from the conventional BM. The −10 dB fractional bandwidths of reflection coefficients and isolations for the proposed BM are 18.46% in simulation and measurement. The −6 dB ± 1.5 dB average transmission coefficient and +45°, −135°, +135° and −45° of output phase differences with 1.8° average phase imbalance are accomplished at 6.5 GHz. The simulated and measured scattering parameters (S-parameters) and phase differences are in close compliance with each other. Four switched-beams pointed at +15°, −50°, +50° and −15° are developed by integrating the proposed BM with inset feeding patch antennas. The proposed BM is miniaturized by 51.56%, whilst the bandwidth performance is enhanced by 9.7% compared to the conventional BM. Hence, this compact BM is a promising candidate for the fifth generation (5G) communication system.

Machine-learning reinforcement for optimizing multilayered thin films: applications in designing broadband antireflection coatings.

The design and fabrication of nanoscale multilayered thin films play an essential role in regulating the operation efficiency of sensitive optical sensors and filters. In this paper, we introduce a packaged tool that employs flexible electromagnetic calculation software with machine learning in order to find the optimized double-band antireflection coatings in intervals of wavelength from 3 to 5 µm and 8 to 12 µm. Instead of computing or modeling an extremely enormous set of thin film structures, this tool enhanced with machine learning can swiftly predict the optical properties of a given structure with >99.7% accuracy and a substantial reduction in computation costs. Furthermore, the tool includes two learning methods that can infer a global optimal structure or suitable local optimal ones. Specifically, these well-trained models provide the highest accurate double-band average transmission coefficient combined with the lowest number of layers or the thinnest total thickness starting from a reference multilayered structure. Finally, the more sophisticated enhancement method, called the double deep Q-learning network, exhibited the best performance in finding optimal antireflective multilayered structures with the highest double-band average transmission coefficient of about 98.95%.

Applicability Analysis of Strain Transfer Between Surface-Mounted Optical Fiber Sensing Component and Materials

In order to explore the coupling transfer mechanism, a multi-layer mechanical model of sensor components is constructed. The surface-mounted strain transmission coefficient formula is derived by analysing the influence between structural parameters and strain transfer coefficient. The strain transmission coefficient of the sensor structure has a positive exponential relationship with the elastic modulus of the tested material through modelling, and the growth trend is gradually reducing. The gypsum material curve is in a parabola, and the top point is 87%. The curved form of concrete and low-carbon steel materials is the same, the top point is 100%, and the concrete curve of the three strengths is close to coinciding. Through integral calculation, the average strain transmission coefficient of gypsum material is 73.5%, C20 concrete is 94.7%, C30 concrete is 95.1%, C50 concrete is 95.3%, and low-carbon steel is 97.1%. The matrix diameter negatively correlates with the strain transmission coefficient, but the influence is small. Integrating the strain transfer coefficient curve, the average strain transfer coefficient of 1.0 mm matrix diameter is 97.45%, 1.5 mm matrix diameter is 97.38%, 2.0 mm matrix diameter is 97.30%, and 2.5 mm matrix diameter is 97.25%. The 3.0 mm matrix diameter is 97.21%. Experiments have verified the rationality of the theoretical formula and the correctness of the influence relationship, which provides a reference for the application of fiber grating sensing technology in tunnel structure monitoring.

Experimental Investigation of the Performance of Porous-Slope Floating Breakwater

Floating breakwater is an alternate solution to traditional breakwaters that can be applied effectively in coastal zones with a moderate wave. In this study, five physical models of the porous-slope floating breakwater have been tested on regular waves in a wave flume. The variations have been applied in wave height, wave period, and mooring angle. The performance of floating breakwater has been evaluated on transmission and reflection coefficient. Under conditions of low wave parameters, the transmission coefficient is higher compared to the high wave parameter. Moreover, the best transmission coefficient value has been found at 60o slope and 5% porosity combination, since the porous-shaped structure has caused large wave dissipation. The slope has caused an increasing value of the average transmission and reflection coefficient at 3.85% and 21.67%, respectively for floating breakwater without porosity. At 5% of porosity, the same improving behavior of transmission and reflection coefficient has been investigated at 2,95% and 27,22% for slope changing as 15° (from 45° to 60°). The result shows that the larger the slope is, the larger the value of the hydrodynamic coefficients is. On the other hand, the porosity has put an effect on transmission and reflection coefficient as well. Floating breakwater with 5% porosity causes an increasing value on the transmission coefficient as 5% and decreases the reflection coefficient value at 8-10% for 45° and 60° slopes respectively.

Structural, optical, and electrical properties via two simple routes for the synthesis of multi-phase potassium antimony oxide thin films

Multi-phase ternary oxide glass thin films of potassium antimony oxide were synthesized via dip coating (DC) and spray pyrolysis (SP) methods. The growth of thin film was conducted on a non-conductive borosilicate glass substrate. Surface morphology was investigated and showed different characteristics. X-ray diffraction (XRD) analysis revealed the peaks corresponded to the monoclinic KSb3O5 and K2Sb4O11 phases. The structural parameter analysis shows that the lower values of micro strain (ε), dislocation density (δ), and stacking fault probability (SF) with higher number (N) of particle in the multi-phase thin film for the spray pyrolysis method confirm slightly larger crystallite size, less crystal imperfection, and less structural disorder. The lower average transmission, absorption, and extinction coefficients resulted to higher refractive index, permittivity, and electrical susceptibility for the sample synthesized by a spray pyrolysis method. In addition, the average energy band gap values (Eg) of 3.57 and 3.60 eV were obtained for the dip coating and spray pyrolysis methods, respectively. However, the lower Rs (14.69 × 107 Ω/sq.) with higher σh (85.09 S/cm) and the FOM(H-HR) (0.183 Ω-1) of the multi-phase K–Sb–O thin film for the dip coating method were obtained may be due to more interconnections generated at the interface and there are less residual on the surface of thin film.

Coupled Wave Energy Converter and Nearshore Wave Propagation Models for Coastal Impact Assessments

Future nearshore wave energy converter (WEC) arrays will influence coastal wave and sediment dynamics, yet there are limited numerical methodologies to quantify their possible impacts. A novel coupled WEC-Wave numerical method was developed to quantify these possible influences on the nearshore coastal wave climate. The power performance of an Oscillating Surge Wave Energy Converter (OSWEC) array was simulated to quantify the wave energy dissipation due to the array. The OSWEC’s effect on the local wave climate was quantified by a novel coupling of two numerical models, WEC–Sim and XBeach. WEC–Sim characterizes the power extraction and wave energy transmission across the OSWEC, while XBeach captures the change in wave dynamics due to the WEC and propagates the waves to shore. This novel methodology provides the ability to directly quantify the impact of the effect of a WEC array on the local wave climate. Three case studies were analyzed to quantify the impact of a single WEC on breaking conditions and to quantify the impact of number of WECs and the array spacing on the local nearshore wave climate. Results indicate that when the WEC is placed 1100 m offshore, one WEC will cause a 1% reduction in wave height at the break point (Hsbp). As the WEC is placed further offshore, the change in Hsbp will become even smaller. Although the change in wave height from one WEC is small, WEC arrays magnify the cross–shore extent, area of influence and the magnitude of influence based on the spacing and number of WECs. For arrays with 10 or 15 WECs, the cross–shore extent was on average 200–300 m longer when the WECs were placed one to two WEC widths apart, compared with being spaced three or four widths apart. When the spacing was one WEC width apart (18 m), there was a 30% greater spatial impact on the nearshore region than arrays spaced three or four widths apart. The trend for the average transmission coefficient is within 5% for a 5, 10 or 15 WEC array, with a cumulative average of 78% transmission across all conditions.

Design development of porous collar barrier for offshore floating fish cage against wave action, debris and predators

This paper presents a design concept of a porous collar barrier for a novel floating open-net fish cage that is integrated with a floating spar wind turbine (referred to as COSPAR fish cage). The COSPAR fish cage has an octagonal shape with each side length of 30m. The collar barrier, having an array of rectangular cut-outs with round corners, is installed at the top portion of the cage to attenuate wave transmission inside the cage as well as to protect fish from external predators and debris. Single and double collar barrier designs corresponding to single net and double net cages are studied. The wave transmission, reflection and energy-loss coefficients of barriers are determined from numerical analysis based on the linear potential wave theory and the eigenfunction expansion method. Various underwater heights (2m ≤ h ≤ 8m) and porosity (0.25≤ ε ≤ 0.75) of the collar barriers are examined with the view to obtaining the barrier design for minimal transmission coefficient and energy-loss coefficient. Without a collar barrier, the single net and double net cage can only provide average wave transmission coefficients of 0.9 and 0.8, respectively. This study finds that the transmission coefficient could be reduced below 0.4 by having a single collar barrier with h = 4m and ε = 0.25. On the other hand, the transmission coefficient could be further reduced below 0.3 by a double collar barrier with the same h and ε. In addition, the double collar barrier gives lower energy-loss coefficient and better proofing against fish escape, biosecurity and predator intrusion than the single collar barrier. A double collar barrier design with porosity combination of ε1 = 0.25, ε2 = 0.5 is recommended for the COSPAR fish cage as it yields competitive wave scattering performances and saves collar material by 25 % when compared with the best performing porosity combination of ε1 = ε2 = 0.25.

Theoretic analysis and experimental evaluation of the spectrum transmission coefficient of a multilayer photovoltaic vacuum glazing

Abstract This paper introduces an innovative thin film PV vacuum glazing (PV-VG) technology. In addition to electricity generation, the PV-VG glazing can also reduce heat loss from the building in winter and reduce heat gain in summer. In building integrated photovoltaics application, optical characterization of the PV glazing is important in determining the solar ray transmission and thermal transfer process of the glazing. This paper discusses the optical properties of the PV-VG glazing by considering the different layers of the glazing unit that includes a self-cleaning glass, a thin film PV glass and a low-e vacuum glazing. Based on the optical transfer matrix, the transmission coefficients of different film layers were deduced. The theoretical calculations were then validated against the transmission coefficient experiment of the PV-VG using an EDTM SS2450 Solar Spectrum Meter. The calculation error of the transmission coefficient of the single-layer glazing is generally within 5%, the calculation error of the transmission coefficient of the integrated PV-VG glazing is about 6%. The results show that the average visible light transmission coefficient, the average infrared light transmission coefficient and the overall transmission coefficient of PV-VG glazing are 19%, 16% and 12%, respectively. The study is important to optimize the visible light transmission of the PV-VG glazing; the optical model obtained above lays a solid foundation for further study of transmission coefficient analysis of different functional coating of PV-VG glazing.

Methodology for Evaluation of District Heating Network Efficiency

The definition of overall district heating network performance indicators is under-investigated in the literature. This study reviews existing methods of performance estimation and develops a convenient methodology for an array of district heating networks applied to a Danish case study. Performances of the networks with state-of-art pipe transmission coefficients are compared to older traditional pipes using an effective average approach. The reported efficiencies and analysis of contributing factors show, that a single parameter is not sufficient to compare large-scale district heating systems and a multiparametric analysis must be employed. The effective average total heat transmission coefficient is evaluated based on the Technical Evaluation Factor and a multivariate regression is performed on typical sets of network parameters: pipe type, pipe series, pipe age, and operational temperature. The developed methodology is applied to testing an array of geographically independent district heating networks, pointing to possible performance bottlenecks, and discussing potential remedies.

Wave Control Performance of Tide-Adapting Low-Crested Structure

Hur, D.S.; Jung, K.H.; Park, J.R., and Lee, W.D., 2019. Wave control performance of tide-adapting low-crested structure. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 116-120. Coconut Creek (Florida), ISSN 0749-0208.Low-Crested Structures (LCSs) are aesthetically apt coastal structures with wave and sand drift control functions. However, they are inappropriate in waters where the tidal range is large because the crest width and height must be above certain levels to allow the breakwater to carry out these functions. Forced wave breaking cannot be induced during high tide because the crest depth increases. Therefore, a Tide-Adapting Low-Crested Structure (TA-LCS) is proposed to overcome the problems caused by large tidal ranges. The hydraulic performance of the proposed LCS was evaluated and compared with that of a typical LCS via hydraulic model experiments. The typical LCS showed an excellent wave screening effect with an average transmission coefficient of 0.4 under the conditions of Fb/Hi=0.29–0.67 and B/Li=0.09–0.15. The wave screening performance of the new type of LCS was 9.5–28.8 % lower than that of the typical LCS. However, the wave screening performance of the new type of LCS decreased only by 9.1–10.4 % under the condition of Fb/Hi≤1 and only by 24.3 % under the condition of Fb/Hi=4. Therefore, the new type of LCS proposed in this study is expected to exhibit its wave control functions during high tide even when installed in a coastal area with a large tidal range.

Experimental investigation of the elastic enhancement factor in a microwave cavity emulating a chaotic scattering system with varying openness.

A characteristic of chaotic scattering is the excess of elastic over inelastic scattering processes quantified by the elastic enhancement factor F_{M}(T,γ), which depends on the number of open channels M, the average transmission coefficient T, and internal absorption γ. Using a microwave cavity with the shape of a chaotic quarter-bow-tie billiard, we study the elastic enhancement factor experimentally as a function of the openness, which is defined as the ratio of the Heisenberg time and the Weisskopf (dwell) time and is directly related to M and the size of internal absorption. In the experiments 2≤M≤9 open channels with an average transmission coefficient 0.34<T<0.98 and moderate internal absorption strength in the range of γ=0.9-2.8 are achieved. The experimental results for the enhancement factor are shown to agree well with random matrix theory predictions. Furthermore, in order to corroborate the wave-chaotic features of the microwave system, the spectral fluctuation properties are studied for M=2 channels. Agreement with those exhibited by typical, fully chaotic systems is illustrated, which is exemplary for the nearest-neighbor spacing distribution and the average power spectrum. Here we take into account the incompleteness of the sequence of resonance frequencies ascribed to the small yet nonvanishing internal absorption.

Multi-Way Quasi-Optical Waveguide Power Divider with 2D Diffraction Approximation and Experimental Verification at Millimeter Wave

In this paper, multi-way quasi-optical parallel-plate waveguide power dividers/combiners are designed and fabricated using the 2D diffraction approximation. Shape optimization technology is applied to shape the cylindrical reflector surface to reconstruct the diffraction field to improve the magnitude and phase balance of the parallel-plate waveguide power dividers. Both a 1-to-6 way quasi-optical waveguide power divider with H-plane horn antenna array and a 1-to-10 way power divider with gap waveguide transition are analyzed and designed, respectively. We fabricated the two designed power devices at millimeter wave for verifying the validity of the design method. The measured average transmission coefficient of the 1-to-6 way power divider is − 10.8 dB from 81 to 110 GHz, corresponding to 50% power combining efficiency, while the measured back-to-back structure of the 1-to-10 way power divider/combiner features an average transmission coefficient to − 2.83 dB corresponding to 72.2% power combining efficiency over the entire W-band. The proposed power dividers/combiners and the efficient optimization method used in their design are believed to be of importance for future power device applications in millimeter wave and terahertz range.

Tuning the interfacial thermal conductance via the anisotropic elastic properties of graphite

The effects of interatomic bonding strengths of graphite itself, in the in-plane (IP) and cross-plane (CP) direction, on the interfacial thermal conductance between graphite and substrate copper (Cu), are investigated by molecular dynamics simulations. It is found that the interfacial thermal conductance at the graphite/Cu interface monotonically decreases with respect to the increase of the IP bonding strength of graphite. However, the interfacial thermal conductance has a maximum with respect to the increase of the CP bonding strength of graphite. By extracting the acoustic iso-energy surfaces and phonon density of states of graphite under various bonding strength parameters, it is found that increasing the IP bonding strength decreases both the incident phonon group velocity component and average interfacial transmission coefficient. Increasing the CP bonding strength also decreases the incident phonon transmission coefficient. However, increasing the CP bonding strength increases the phonon group velocity component. To provide a practical method to enhance the interfacial thermal conductance, we compared the interfacial thermal conductance of porous graphite/Cu interface, which is higher than the graphite/Cu interface mainly due to the large reduction of the in-plane elasticity. This study provides important guidance in the active regulation of the interfacial thermal conductance between anisotropic materials and substrate.

A new design of optical add/drop filters and multi-channel filters based on hexagonal PhCRR for WDM systems

In this research, using photonic crystal dielectric rods with a triangular lattice constant, a photonic crystal ring resonator (PhCRR) has been designed in order to be used in optical add/drop filters (ADF).Query Using the proposed hexagonal PhCRR with four different dropping waveguides, new ADFs have been designed and simulated. At a central wavelength of 1550.5 nm, the four proposed ADFs have an average transmission coefficient, a bandwidth, and a quality factor of 100%, 1.2 nm and 1330, respectively. The results obtained from these structures indicate the high flexibility of the proposed PhCRR and ADFs and their applicability in optical communication systems. Using the ADFs, two multi-channel drop filters have been designed in order to be used as optical MUX/DeMUX with a channel spacing of 4 nm which are suitable for wavelength division multiplexing systems. In this study, the plane wave expansion and finite difference time domain methods are, respectively, used, to characterize the photonic band gap and to investigate the optical behavior of the structures.