Search

High-power DC–DC converters are integrated into multi-terminal high-voltage DC (MTDC) networks, typically for voltage matching or flexible DC transmission. This study addresses droop-controlled radial and mesh MTDC networks with transmission loss minimisation considering the impact of integrating a high-power DC–DC converter. DC voltage droop control can achieve minimum power loss in radial MTDC transmission network by controlling the power-sharing among the receiving nodes inversely proportional to their transmission line resistances. Updating the droop characteristics by an optimisation algorithm guarantees optimal power flow (OPF) during renewable source power generation fluctuation. Meanwhile, the mesh network DC voltage references can be updated by the OPF for transmission loss minimisation. This study presents the impact of incorporating a high-power DC–DC converter at different system access lines of a radial MTDC network while targeting efficient power transfer and DC transmission loss minimisation. The effect of introducing a high-power DC–DC converter on the droop characteristic settings during steady-state operation in a radial MTDC network is investigated. Moreover, the impact of a high-power DC–DC converter in mesh MTDC network with OPF operation is explored. To validate the presented concepts, the CIGRE B4 MTDC network is used as a benchmark system with a metaheuristic optimisation technique.

During recent years, allocating the network losses to loads and generation units based on network transactions is an important issue in the power industry. This study presents an appropriate method to allocate the network losses to loads and generation units according to their network transactions. This method is appropriate and faster than other loss allocation techniques and does not consider unreasonable assumptions in the loss allocation process. This method explicitly assigns the network losses according to individual transactions, and this leads to allocate the network losses among all network transactions. This approach is based on the share of the loads and generation units on active and reactive power flows passing through the lines according to transactions. The implementation of the method on large networks is simple and fast. To approve the performance of the presented method, the proposed loss allocation technique has been applied to a three-bus case study system and the IEEE 14-bus test system. Also, several different transaction modes are used to show the performance of the presented method for transmission loss allocation based on transactions.

The proposed study contains the design and analysis of TM 11 to HE 11 (hybrid) mode converter at 42±0.2 GHz which is an integral component of the transmission line that transmits 200 kW power from gyrotron to the plasma in SST-1 Aditya tokamak. HE 11 mode is preferred, as the transmission loss in corrugated waveguide is less in comparison with other modes. For generating HE 11 mode from TM 11 mode, the depth of the annular slots in the mode converter is varied gradually from zero to one-quarter wavelength. The conversion efficiency and radiation pattern of the proposed mode converter depends on the corrugation profile and the length of the mode converter. Both the parameters are optimised numerically to achieve the highest conversion efficiency. Keeping in mind mechanical fabrication of mode converters optimisation has been carried out. It converts 95.6% power of TM 11 mode into HE 11 (82.2% TE 11 +13.4% TM 11) mode respectively. The 1 dB compression bandwidth of 19.04% (8 GHz) at 42 GHz is obtained. The length of mode converter is 40.83 λ mm. The reflection coefficient and VSWR are -25 dB and 1.1 respectively. The power in side lobes and isolation from cross polar component is less than -20 dB and -25 dB respectively.

This study proposes an improved normalised normal constraint (NNC) method for solving optimal power flow (OPF), which is formulated as a multi-objective problem. While NNC is an efficient solution method to solve multi-objective problems, it may not cover the entire Pareto frontier in the objective space when three or more objectives are present in the problem, i.e. when the Pareto frontier becomes a hyper-surface. This research work aims to solve this limitation of NNC and propose a more effective solution method, named improved NNC (INNC), for multi-objective optimisation problems with three or more objective functions. The proposed INNC is applied for solving multi-objective OPF problem with three objectives of generation cost, transmission loss and voltage regulation. The effectiveness of the proposed INNC method for solving the multi-objective OPF problem is extensively illustrated on the IEEE 30-bus and IEEE 118-bus test systems in comparison with several recently published multi-objective solution approaches.

During recent years, the shift from monopoly integrated power systems to restructured power systems caused an increased competition among the electricity market. In restructured power systems, providing a fair and impartially service pricing is still in discussion on ‘who should be reprimand’ for the losses contribution. The loss allocation (LA) causes appropriate economic penalties or rewards to generators and consumers. This study presents a reasonable method for LA in power systems. This method is based on the injected active and reactive power into network lines. At first, the contribution of the loads in the loss of each line is obtained regardless of the generators. Then, the loss of lines is allocated to source buses and the contribution of each generator in the loss of each line is calculated. At the final step, a normalisation factor is introduced and the final contribution of each load and each generator in the loss of each line is calculated separately. The proposed algorithm is simple and easy to implement on the large-scale power systems.‏ This proposed method has been applied to the IEEE 14-bus and IEEE 30-bus test systems, and the obtained results are compared with other existing LA methods.

With the development of active distribution networks, new challenges such as overvoltage and power loss become critical. The reactive power optimisation serves as a voltage control measure to minimise the total transmission loss by coordinating the continuous and discrete reactive power compensators while guaranteeing the specific physical and operating constraints. To address the daily operating times of discrete control variables, the dynamic reactive power optimisation (DRPO) is set up to minimise total energy loss over several time periods when considering the inter-temporal constraints. However, DRPO is in fact a large-scale mixed integer non-linear non-convex programming that is difficult to solve. Therefore, second-order cones are employed to relax the non-convex power flow equations to obtain a mixed integer second order cone programming model. Furthermore, a sensitivity-based relaxation and decomposition method is proposed to further improve the computational performance. Solution quality and computational performance are compared with traditional methods on IEEE-33, 123 and 615-bus systems as well as two real-world distribution networks in China. The Results demonstrate that the fast performance and effectiveness of the proposed technique.

A radome has to be carefully designed to ensure it has minimum impact on the performance of the antenna. Traditional approaches involve equation approximations, complex ray tracing, iterative manufacturing process and or electrically large and lengthy electromagnetic (EM) simulations. The novel approach described in this study involves a two-dimensional ray tracing method simulation in MATLAB and an electrically small unit cell simulation in high-frequency structure simulator. This new approach gives an optimal thickness result that is only 0.004 mm different to that of a full EM simulation. The radome is manufactured and radio-frequency tested in an anechoic chamber, the calculated thickness is shown to be the optimal thickness.

Supplying transmission losses economically under bilateral contract is a challenge for power engineers. In this study, penalised quoted cost (PQC) based approach is proposed where generators will participate for supplying the transmission losses which may be incurred from their customers through their bilateral contracts in a deregulated electricity market. The loss supplying generators will quote the cost and the quantum of real power that can be supplied by them to independent system operator (ISO) in a day-ahead market. This study presents a lucid approach for loss allocation economically by ranking the loss supplying generators based on their PQC. Penalty factor for each loss supplying generator is calculated using the loss coefficients. ISO will meet the losses due to bilateral contracts in an economical way by selecting the generators with minimum PQC and the associated cost is allocated to the individual transactions based on loss contribution fraction. The proposed algorithm is tested using a sample four-bus system and IEEE 30 bus system using MATLAB R2014a. This method is based on the participation of generators and their given quotation in transmission loss allocation process. The study gives both the real power loss/cost allocation to the generators and for individual transactions.

Major load centres of India are located at northern part and western–southern part of country, whereas most of the generating units are concentrated at eastern and North-eastern parts. Economic transmission of bulk power over a long distance is a basic requirement for which ultra-high voltage AC (UHVAC) transmission system is identified as a feasible solution resulting in reduced transmission loss and reduced corridor width (right of way), protection of precious flora and fauna. For this, Powergrid Corporation of India along with Central Power Research Institute had made a call for indigenous development of UHVAC technology. As a result, 1200 kV UHVAC National Test Station is developed in India at Bina. One 400/1200 kV bay is successfully charged, along with one 1200 kV single circuit and one 1200 kV double-circuit test transmission line. This study deals with the study of on-site acceptance test such as sweep frequency response analysis, frequency-domain spectroscopy (FDS), along with inrush current measurement, voltage withstand test, corona measurement, thermo-vision scanning conducted on-site at no load, to ensure the performance of transmission system. A brief review of technical studies related to UHVAC technology developed throughout the World is also presented. The power transmission at 1200 kV is a feasible and viable option but further research is required in this area to make UHV transmission a global success.

Interconnected voltage-source converter based multi-terminal high-voltage DC (HVDC) systems provide better system redundancy, higher flexibility and capability of exchanging power between multiple areas. Recent developments in modular multi-level converter technology makes multi-terminal HVDC (MTDC) transmission more promising than before. This study provides an in-depth analysis of the power flow and transmission loss for MTDC systems with different grid topologies. A voltage–power droop control based algorithm is applied to solve the power flow problems. The main contribution of this study is the novel way of determining and calculating the transmission line losses for different MTDC network topology configurations. Three MTDC system topologies are investigated. Simulated case studies are used to observe the system power flow and transmission losses for all three topologies.

Time synchronisation is one of the key issues to realise remote detection for multi-static radar. With the condition that the receivers are commonly located at different distances from the transmitter, a high-precision time synchronisation scheme for multi-static radar with mixed microwave and troposcatter channels is proposed. In order to prove the feasibility of transmitting pulse signals in microwave channel, the jitter of the signals has been tested, and the transmission loss of the troposcatter channel has been calculated. Finally, the accuracy of the proposed model is analysed, which shows that the proposed scheme is feasible and can be a backup for time synchronisation for multi-static radar.

Crete is the largest autonomous power system in Greece. Thera is a small island in the Aegean Sea, widely known as Santorini. This study tackles with the potential impact in case of interconnection of these two island systems. The impact on the economic operation of both power systems, the expected flow between these two power systems and the fuel savings resulting from their interconnection are presented as a part of a preliminary techno-economic study that can be also used for investigation of further interconnections in the area. In addition, some insight on the transmission losses and the level of interconnection voltage is provided.

Numerical analysis of a bilayer graphene nanoribbon (BLGNR) using the reproducing kernel particle method (RKPM) – a true meshless approach – is reported. Electrostatic analysis of the BLGNR is performed using the RKPM approach. Validation of the structure is executed by comparing the result with an equivalent single conductor model and shows better accordance. Radio frequency (RF) analysis of the BLGNR as the interconnect is studied using advanced design systems with the quasi-static analysis derived through the RKPM method. The simulation results in a return loss of −89.69 dB and transmission loss of −0.00028 dB at 1 THz which is suitable for RF interconnect applications.

This study presents an efficient and reliable evolutionary-based approach, termed as chaotic krill herd algorithm (CKHA), to solve the optimal reactive power dispatch (ORPD) problem of power system. In the proposed CKHA, various chaotic maps are considered to improve the performance of the basic KHA. The performance of the proposed CKHA is examined and tested, successfully, on standard IEEE-30 and IEEE-57 bus test power systems for the solution of ORPD problem in which control of bus voltages, tap position of transformers and reactive power sources are involved. The objective function considered is either minimisation of active power transmission loss or that of total voltage deviation or enhancement of voltage stability index. The results offered by the proposed CKHA are compared with those offered by other evolutionary optimisation techniques surfaced in the recent state-of-the-art literature. Simulation results indicate that the proposed CKHA yields superior solution over the other recently surfaced popular techniques in terms of effectiveness and convergence speed.

A method to fabricate continuously tapered antireflective (AR) coatings using fused deposition modelling (FDM) is presented. The method leverages FDM's ability to fabricate spatially varying 3D structures with variable polymer fill volumes, thus producing a spatially varying effective permittivity profile. The method is validated experimentally within the Ka-band. Experimental results closely match predictions, and AR treated samples demonstrate much less transmission loss than non-AR treated samples.

This study proposes a hybrid optimisation method for optimal power flow using a flexible AC transmission system (FACTS). The FACTS plays an important role in the dynamic stability and steady-state control of power systems. This study achieves steady-state control by determining the types and the optimal locations of the FACTS devices and their associated values in the transmission lines. To determine the optimal solutions to the FACTS allocation problem, a hybrid optimisation method that combines a harmony search algorithm and an ant system is proposed. The objective functions of power flow considered are the active power transmission loss, the performance index of the active power flow in the transmission lines and the performance index of the voltage difference between buses. The proposed method was verified on the IEEE 30-bus and Taiwan Power Company 345 kV simplified systems. The results demonstrate that the proposed method improves the total transfer capability and provides better steady-state control of power systems than existing methods do.

In this study, a miniaturised wideband rat-race coupler using glass integrated passive device (GIPD) technology is studied. The circuit miniaturisation is achieved using slow-wave synthesised coplanar waveguides (CPWs). For wideband operation, a compact CPW phase inverter is developed and integrated. At the centre frequency, 12 GHz, the proposed rat-race coupler is only 6.5% the size of a conventional 1.5-λg ring coupler with the same GIPD technology; the fractional bandwidths, on the other hand, reach 65 and 32%, respectively, at the sum and difference ports. The coupler shows good amplitude and phase balances, with the transmission loss around 0.7–1.1 dB at the centre frequency.

This study presents a real coded chemical reaction algorithm to solve economic load dispatch (ELD) problems involving different constraints such as power balance, ramp rate limits and prohibited operating zone constraints. Effects of valve-point loading and multi-fuel options of large-scale thermal plants are also studied. System transmission loss has also been considered in a few cases. Chemical reaction optimisation mimics the interactions of molecules in a chemical reaction to reach from a higher energy unstable state to a low energy stable state. A real coded version, known as real-coded chemical reaction optimisation is implemented here to solve ELD problems. The simulation results establish that the proposed approach outperforms several other existing optimisation techniques in terms of quality of solution obtained and computational efficiency. The results also prove the robustness of the proposed methodology to solve ELD problems.

In this study, a novel on-chip low-loss slow-wave slot (SWS) microstrip transmission line is proposed. Unlike conventional slow-wave structures such as photonic bandgap and ladder microstrip transmission line, which usually deal with either the substrate, ground plane or the signal line separately, the periodic patterns of SWS structures are etched along both the conductive metal strip and the ground plane of the microstrip line. The proposed structure, unlike other slow-wave structures does not require extra drilling through the substrate or complex three-dimensional multi-layer structures, only requires coplanar slot etching. The proposed SWS microstrip demonstrates excellent size reduction with minimal increase in loss. To show the utility of the proposed method, two second-order rectangular open-loop filters with and without implementing the proposed SWS microstrip have been designed with similar bandwidths and fabricated in the millimetre-wave (mm-wave) range on 65-nm bulk complementary metal oxide semiconductor (CMOS). Both simulations and measurements demonstrate that the on-chip filter implemented using the proposed SWS has a 52.7% reduction in size while suffering only an additional 0.5%dB in transmission loss penalty. To the best of authors% knowledge, this compact filter is the first reported mm-wave filter using slow-wave structure on bulk CMOS.

For AC railway power supply systems with a different frequency than the public grid, high-voltage AC transmission lines are common, connected to the catenary by transformers. This study suggests an alternative design based on an high-voltage DC (HVDC)-feeder, which is connected to the catenary by converters. Such an HVDC line would also be appropriate for DC-fed railways and AC-fed railways working at a public-grid frequency. The converter stations between the public grid and the HVDCfeeder can be sparsely distributed, not denser than on 100 km distances, whereas the converters connecting the HVDC-feeder to the catenary are distributed denser. Their ratings can be lower than present-day substation transformers or converters, since the power flows can be fully controlled. Despite a relatively low-power rating, the proposed converters can be highly efficient because of the use of medium frequency technology. The proposed feeding system results in lower material usage, lower losses and higher controllability compared with the present solutions. Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared with conventional systems, especially for cases with weak feeding, and when there are substantial amounts of regeneration from the trains. QC 20130813

A new kind of power system marginal loss (or loss sensitivity) for nodal MW/Mvar is developed. First the electricity transmission loss is expressed in terms of source currents. It is thus an analytical function. Then the marginal loss with respect to source current is derived based on calculus and vector algebra. Using each source/load power represents its nodal injection current, the marginal loss with respect to source current is then transformed into the marginal loss with respect to source/load power. The new kind of marginal loss is based on load flow solution. It is exact in algorithm and independent of reference bus, thus called independent marginal loss (IML). The IML exactly leads to double collection of actual system loss. It makes loss components of locational marginal price small in spatial fluctuation compared to the existing marginal losses. Numerical examples including the IEEE 118-bus and PJM [Note 1] 5-bus systems are presented to demonstrate the calculation and effectiveness of the IML.

Sensing in urban environments is of growing interest to the surveillance community, as is observation of targets with micro-Doppler features - elements of the target structure with independent range-Doppler behaviour about some target centroid. Multipath effects unique in character to urban sensing can conceal important features in the range-Doppler response of a target with micro-Doppler behaviour. The range-Doppler smearing because of multipath is analysed, and this analysis serves as the basis for a prominent point multipath mitigation algorithm. The effectiveness of this technique is evaluated with simulated micro-Doppler data with artificial multipath effects.

A predictive control-based approach is proposed to networked control systems. In this approach, an improved predictive controller is designed using delayed sensing data and a compensation scheme is proposed to overcome the negative effects of the network-induced delays and data packet dropouts in both the forward and backward channels. The proposed approach is easy to be implemented in practice compared with previous results in that only delayed data of the control inputs are used to derive the forward control predictions. The stability of the closed-loop system is obtained by modelling the system as a time delay system with structural uncertainties. Simulations show that the proposed approach is superior to the previous results in the situation where only delayed data are used.

Available beyond line-of-sight time synchronisation means are mainly through satellite and optical fibres. When considering that satellite links have insurmountable bandwidth and security problems, and cable links are not feasible for mobile stations, a backup two-way time synchronisation means via troposcatter is proposed. The feasibility of the proposed method based on coherence bandwidth and transmission loss is analysed, and references for the time pulse signal design are provided. Then, two different signal time sequences schemes aiming at co-channel interference are presented and evaluated, and the clock errors due to the incomplete symmetrical two-way link are analysed. Finally, it is concluded that the proposed means is a promising candidate for beyond line-of-sight time synchronisation in emergency communication.

A method for analysing distributed feedback waveguides with arbitrary refractive index profiles is reported. The method considers a waveguide as a number of segments within which the reflection is weak, and thus the relevant transmission loss and multiple reflections can be neglected. By introducing a concept of reflective density formulas are derived for calculating the reflection and transmission coefficients and therefore the transfer matrix of an individual waveguide segment. The global reflection and transmission characteristics of the waveguide are then obtained by multiplying transfer matrices of all the waveguide segments together. The proposed method shows better accuracy than the coupled-mode method and requires less computation time than the effective-index method. The limitation of the coupled-mode method is shown both numerically and analytically for the first time and it is demonstrated that the coupled-mode method is only valid for analysing long Bragg gratings with particular initial phases.

A novel substrate integrated waveguide to rectangular waveguide (RWG) transition for effective power transfer is proposed. The substrate taper is inserted into a conventional height-stepped impedance transformer of the RWG region to improve transmission loss and bandwidth. The transition is designed to cover the entire K-band (18–26 GHz), showing a return loss of 20 dB. A back-to-back transition has been fabricated to verify the proposed transition. The experimental results show good agreement with the analysis. The transmission loss of the stand-alone transition is 0.22 dB at 21.7 GHz with a usable bandwidth of 36%.

Low loss channel waveguides have been formed in silica-on-silicon by implantation with 5 MeV Si and Ge ions. In these experiments, the substrate was comprised of an undoped layer of silica (30 /spl mu/m thick) which was grown by plasma enhanced chemical vapour deposition (PECVD). The optical loss characteristics of the waveguides, as measured at both /spl lambda/=1300 and 1550 nm, were independent of the implanted ion species, A minimum in the attenuation loss (/spl alpha/) of /spl sim/0.10-0.20 dB/cm was obtained following both a pre-implant (1050/spl deg/C) and a post-implant (400-500/spl deg/C) anneal of the waveguides. The ability to produce a minimum in a by pre-implant annealing has been attributed to the thermally induced relaxation of the densified structure in the as-grown layer. Only a comparatively small degree of compaction was measured for Si-implanted samples which did not receive a pre-implant anneal. In contrast, the much larger degree of compaction in the pre-implant annealed samples was similar in magnitude to that observed in fused silica. These are the first reported examples of ion-implanted waveguides using a substrate of silica grown by PECVD.

Silica-based integrated optical waveguide technology is reviewed. Low loss and manufacturable waveguides are made by chemical vapour, flame hydrolysis and electron beam deposition. Fibre to fibre insertion loss is as low as 0.3 dB for a 6 cm long waveguide. Bragg reflective add-drop filters are made with gratings formed by ultraviolet irradiation. The waveguide grating router has found important application as a multiplexer in dense wavelength multiplexed communications systems. Multiplexers with wide pass bands and stop bands are made with Fourier filters: these filters consist of a chain of alternating couplers and delaying arms. The good performance of waveguide grating routers and Fourier filters is due to the high degree of path delay and coupler control achievable by and processing in this technology.

An atomic force microscope is employed to measure the edge roughness of masks used in the fabrication of rectangular-core buried channel waveguides (BCWs) and to compare this with the corresponding roughness of the etched BCWs. Light attenuation due to scattering loss from the sides of the core can then be estimated using a simple statistical model to process the measured data.

Introduces the basic technologies that are associated with measurements of monolithic microwave integrated circuits. The use of test fixtures and wafer probe stations at ambient room temperature is reviewed and their role at thermal and cryogenic temperatures is discussed. With the increasing need for performing non-invasive measurements, advances in experimental field probing techniques are explored. >

Berenger's perfectly matched layer (PML) absorbing boundary condition is implemented for the first time in a TLM mesh. This is achieved through a special interface between the FDTD-PMLs and the TLM lattice. Application to rectangular waveguides yields reflections less than -50dB at frequencies up to six times the cutoff frequency. These absorbing boundary conditions are compared with one-way equation absorbing boundary conditions and with matched layers having only electric losses. >

A novel, simple fabrication method of vertically tapered spot size transformers is demonstrated by screening the sample partially with a shadow mask during reactive ion etching. The authors measured a transmission loss of 2.3 dB for a single taper structure from the chip waveguide without an antireflection coating on the fibre.

Optical rib waveguides with widths from 2.73 to 7.73 microns have been formed in SIMOX-based silicon-on-insulator (SOI) structures consisting of a 4.32 micron thick surface-silicon layer and a 0.398 micron buried-oxide layer. The effect of waveguide width, bend radius, y-junction splitting and interface roughness on loss and mode characteristics have been studied at wavelengths of 1.15 and 1.523 microns. The experimental results support the hypothesis that certain rib dimensions can lead to single-mode waveguides even though planar SOI waveguides of similar multimicron dimension are multimode. The propagation losses of waveguides 3.72 microns wide were found to be nominally 0.0 dB/cm and 0.4 dB/cm for the TE and TM modes, respectively, when measured at 1.523 microns, where the measurement error was +or-0.5 dB/cm. This means that the loss is experimentally indistinguishable from pure bulk silicon. These results are thought to be the lowest loss measurements for silicon integrated optical waveguides reported to date.

Silica waveguide circuits for 1*N and 2*N splitters have been fabricated on silica (quartz glass) substrates. They show very low polarisation dependence and have insertion loss comparable to silica-on-silicon devices.

The results are described of experiments carried out to determine the effects of transient losses caused by working party operations on British Telecom's current and future optical networks. Results show that even systems operating with 19 dB of optical margin above the nominal 10-9 bit error rate operating point can still be affected by transient attenuation losses.

The long-term behaviour of erbium-doped fibres under gamma -ray irradiation at a low dose rate of 0.5R/year was predicted for the purpose of applying the fibres to transoceanic transmission systems, based on the experimental result that permanent defects in fibres were dominantly generated at low dose rates. The estimated degradation of transmission loss and amplification gain after 25 years in undersea were 0.04 dB/km and 0.3 dB, respectively.

Pulse recompression and dispersion compensation are demonstrated using 8 mm long all fibre photoinduced chirped reflection gratings at 1560 nm. Optical pulses of 400 fs at 100 Gbits/s are almost fully recompressed after undergoing broadening of approximately 30 ps in an optical fibre; a compression ratio of 67 is achieved.

A novel method for fabricating all fibre photoinduced chiped gratings is presented for the first time. 8 mm long gratings with reproducible chirped bandwidths between 3 and 15 nm and reflectivities up to 95% are demonstrated. Near ideal response is achieved for linear and quadratic wavelength chirped gratings.

The authors report low threshold current large spot size MQW BH lasers. Coupling losses to 10 mu m core cleaved singlemode fibre down to 4.1 dB have been obtained for devices with threshold currents of 4.9 and 15 mA at 20 and 80 degrees C, respectively.

Refractive index profiles of dispersion compensating fibres (DCFs) with fluorine-doped cladding were explored to realise a high figure of merit. By optimising the refractive indexes of the core and cladding materials, a DCF with a figure of merit of 250 ps/nm/dB was successfully fabricated.

Two new coplanar waveguide to rectangular waveguide couplers with coupling through a post and a slot are experimentally demonstrated. The couplers operate over the Ku-band transmission and X-band reception frequencies that are designated for satellite communications. The measured insertion loss and return loss are about 1 dB, respectively, for both couplers.

The potential of employing textile materials to realise a switchable on- and off-body communication system at 2.45 GHz is demonstrated. It is based on an aperture-coupled rectangular textile microstrip patch antenna mounted on textile stripline with a pin diode switching network. Simulations and measurements are presented which show good agreement. On-body communication through a 600 mm-long stripline shows a transmission loss of around 5 dB. Off-body communication via the patch antenna shows a bandwidth from 2.4-2.48 GHz with a boresight gain of 1.48 dBi.

Proposed is a novel technique for high resolution spectral characterisation of polarisation dependent loss of optical components, based on an optical single sideband with suppressed carrier modulation. Experimental measurements are performed to demonstrate the technique.

Periodic structuring of the ground plane is presented as a method of adjusting the properties of thin-film microstrip cables. Such cables may be useful as interconnects when flexibility is required and space is at a premium. Simple analytic models are presented and verified by numerical simulation. Prototype cables are fabricated in 2 m lengths of copper-clad polyimide. The effect of dimensions on characteristic impedance, cut-off frequency and propagation loss is investigated, and it is shown that impedance close to 50 may be combined with low loss, using feature sizes compatible with flexible printed circuit board (PCB) fabrication.

A hybrid plasmonic waveguide based on a silicon-on-insulator substrate with an air trench is proposed and investigated. Theoretical analysis demonstrates that the nano-scale air trench could result in strong local field enhancement and tight mode confinement. Besides, the transmission loss of the fundamental hybrid plasmonic mode could also be reduced despite the existence of the high-index silicon rib. The proposed structure is compatible with standard nanofabrication process based on the silicon wafers and could enable various nanophotonic integrated components.

This study presents a performance comparison of metaheuristics to solve transmission expansion planning (TEP) problems in power systems. The proposed methodology includes the search for the least cost solution, bearing in mind investments and operational costs related to ohmic transmission losses. The multi-stage nature of the TEP is also taken into consideration. Case studies on a small system and on a real sub-transmission network are presented and discussed.

This study presents a usage-based methodology of transmission loss allocation in deregulated power systems under open access. This new approach calculates the portion of real power transmission loss contributions from the generators and simultaneously the portion of real power transmission loss allocated to the loads using their contract obligations with the generators in the open access environment. A power flow procedure is used to calculate power loss in the system. It is desirable to take network loss effect of injection power at each node for calculating contribution of transmission loss by each generator and loss allocated to loads based on its contractual obligations with consumer. In this study, a methodology is proposed to calculate the total real power loss in transmission network into components to be allocated to the generators and loads. This study focuses on development and application of the equivalent loss compensation concept for open access environment. Effectiveness of the proposed algorithms has been demonstrated on sample 5-bus and IEEE-118 bus power networks.

Wideband 3D transitions from 60 to 110 GHz using 50 μm via technology on liquid crystal polymer (LCP) are presented. A conductor backed coplanar waveguide (CBCPW) transition on a homogeneous LCP sample shows less than 0.8 dB loss from 60 to 110 GHz. In addition, a CBCPW-to-CBCPW and a CBCPW-to-CPW transition on LCP bonded to silicon substrate are presented also in the range 60-110 GHz. The CBCPW-to-CBCPW transition shows less than 0.5 dB loss up to 100 GHz. The CBCPW-to-CPW transition yields less than 1 dB loss up to 110 GHz. These transitions are the first characterisation of vias in organic substrate packaged silicon in the 60-110 GHz frequency range.

Allocating means of transmission losses and costs are presented taking into account pool and bilateral contract hybrid deregulated power market. The transmission loss is allocated according to a mathematical relationship between the node power and the line power flow for a DC power network. By the proposed method, the authors not only can allocate total loss to either generator or load node, respectively, but also can distribute it to both generator and load nodes conveniently. To ascertain the effectiveness of the proposed techniques, the authors show various simulation results based on IEEE 14-bus and Hokkaido 44-bus power systems.

Two circuit modelling and parameterisation techniques for optimisation of a left-handed microstrip transmission line for antenna applications are presented. Such a transmission line is characterised by high transmission loss ripples in the required frequency band, which hinders its use as a wideband feeding network in antenna array applications. The first circuit modelling technique is based on numerical parameterisation, whereas the second is based on analytical parameterisation. The goal of the parameterisation is to obtain multivariable functions to represent the components of the circuit model with the geometrical dimensions as parameters. A novel and improved circuit model taking into consideration the external mutual coupling between the elements of the left handed transmission line was used to optimise its performance in terms of absolute transmission loss and minimum ripple over a wide frequency band. The performance of the improved equivalent circuit model is compared with the electromagnetic simulations, and a good agreement is obtained. A prototype of the optimised left-handed transmission line was built and tested. Satisfactory agreement was obtained between the simulated and measurement results.