Lossless Networks Research Articles

Breaking the Efficiency Barrier for Ambient Microwave Power Harvesting With Heterojunction Backward Tunnel Diodes

Harvesting low-density ambient microwave power as an alternative power source for small ubiquitous wireless nodes has been proposed in recent papers discussing emerging technologies like the Internet of Things and Smart Cities. However, a literature review of the state-of-the-art Schottky diode based microwave rectifiers shows that a maximum efficiency has been reached for such devices operating in the low-power regime, as is the case for ambient microwave power-harvesters. This work examines the underlying physical mechanisms responsible for this RF-to-dc power conversion efficiency limitation, and explores a high I-V curvature backward tunnel diode to overcome this efficiency limitation. Measurements of the 2.4 GHz RF-to-dc power conversion efficiency at $-$ 40 dBm input power demonstrates that the backward tunnel diode outperforms the HSMS-285B Schottky diode by a factor of 10.5 and the Skyworks SMS7630 by a factor of 5.5 in a lossless matching network scenario. A prototype built using a new GSG probe embedded with a matching circuit showed a total power conversion efficiency of 3.8% for $-$ 40 dBm input power and 18.2% for $-$ 30 dBm input power at 2.35 GHz.

How to Enhance the Efficiency of Loss-Less Optical Burst Switching Networks with the Streamline Effect

With the ongoing steady traffic increase in the Internet, the wavelength usage of the supporting optical networks is a critical network efficiency parameter. Therefore, this paper suggests a way how to efficiently and economically achieve this goal in the context of optical burst switching, a very promising technology that has been proposed to overcome the shortcomings of conventional WDM deployment, such as lack of fine bandwidth granularity in wavelength routing and electronic speed bottlenecks in the presence of bursty traffic. In order to mitigate the burst loss and achieve high network efficiency we adapt the loss-less paradigm defined by Coutelen et al. (2010), i.e., the CAROBS framework. In classical OBS networks, the streamline effect ensures a very low level of contention, i.e., efficient transmission, hence we define a routing guided only by the streamline effect. The resulting routing problem is formulated as an optimization model which is solved using a decomposition technique to increase the scalability of the solution process.

Energy-Event-Triggered Hybrid Supervisory Control for Cyber-Physical Network Systems

This technical note develops energy-event-triggered hybrid supervisory control techniques to address robust and fast energy equipartition for cyber-physical network systems, and discusses the application of the proposed approach to power systems. First, we present a hybrid controller with a distributed feedback and supervisory energy-event-triggered resetting law to achieve the robust disturbance rejection performance of physical networks by mimicking thermodynamic systems. The proposed controller architectures are constructed in such a way that each controller has a one-directional energy transfer from a plant to itself, and exchanges energy with its neighboring controllers. Specifically, if the cyber-physical system is lossless, this controller can prevent cascading behaviors. Second, we propose a consensus hybrid controller that mitigates the disturbance effect by decentralizing the disturbance on one plant to all the other plants when stabilizing it. In addition, a new combined hybrid controller based on the two precedent hybrid controllers is proposed to achieve cascade prevention and fast energy equipartition for lossless cyber-physical network systems. Finally, we apply our hybrid control technique to power systems, and simulation studies are carried out to show the efficacy of the proposed approach.

Complex Reflection Coefficient Synthesis Applied to Dual-Polarized Reflectarrays With Cross-Polar Requirements

An extended formulation of the intersection approach (IA) algorithm is presented to synthesize matrices of complex reflection coefficients for dual-polarized reflectarrays. The synthesis of complex reflection coefficients allows to impose copolar as well as cross-polar specifications, since these coefficients fully characterize the behavior of the unit cell. The implementation of the algorithm is based on the use of the fast Fourier transform (FFT) in both the forward and backward projectors of the IA, allowing for a highly efficient and fast synthesis process of dual-polarized reflectarrays. Although arbitrary restrictions can be enforced in the reflection coefficients, they might not be feasible for passive antennas. Hence, the unit cell is analyzed as a lossless and lossy passive two-port network and the restriction equations are derived for both cases involving amplitudes and phases of the reflection coefficients. The lossless constraints proved to be too restrictive so lossy restrictions should be applied to achieve feasible reflection coefficients for passive array design. Test cases are provided, which confirm that the algorithm is able to synthesize with success radiation patterns with copolar and cross-polar requirements with restrictions applied to the reflection coefficients.

Applications of Generalized Cascade Scattering Matrix on the Microwave Circuits and Antenna Arrays

The ideal lossless symmetrical reciprocal network (ILSRN) is constructed and introduced to resolve the complex interconnections of two arbitrary microwave networks. By inserting the ILSRNs, the complex interconnections can be converted into the standard one-by-one case without changing the characteristics of the previous microwave networks. Based on the algorithm of the generalized cascade scattering matrix, a useful derivation on the excitation coefficients of antenna arrays is firstly proposed with consideration of the coupling effects. And then, the proposed techniques are applied on the microwave circuits and antenna arrays. Firstly, an improved magic-T is optimized, fabricated, and measured. Compared with the existing results, the prototype has a wider bandwidth, lower insertion loss, better return loss, isolation, and imbalances. Secondly, two typical linear waveguide slotted arrays are designed. Both the radiation patterns and scattering parameters at the input ports agree well with the desired goals. Finally, the feeding network of a two-element microstrip antenna array is optimized to decrease the mismatch at the input port, and a good impedance matching is successfully achieved.

Impedance Control Network Resonant dc-dc Converter for Wide-Range High-Efficiency Operation

This paper introduces a new resonant converter architecture that utilizes multiple inverters and a lossless impedance control network (ICN) to maintain zero-voltage switching and near zero-current switching across wide operating ranges. Hence, the ICN converter is able to operate at fixed frequency and maintain high efficiency across wide ranges in input and output voltages and output power. The ICN converter architecture enables increase in switching frequency (hence reducing size and mass), while achieving very high efficiency. Three prototype 200-W 500-kHz ICN resonant converters, one with low-Q, one with medium-Q, and one with high-Q resonant tanks, designed to operate over an input voltage range of 25 to 40 V and an output voltage range of 250 to 400 V are built and tested. The low-Q prototype ICN converter achieves a peak efficiency of 97.1%, maintains greater than 96.4% full power efficiency at 250 V output voltage across the nearly 2:1 input voltage range, and maintains full power efficiency above 95% across its full input and output voltage range. It also maintains efficiency above 94.6% over a 10:1 output power range across its full input and output voltage range owing to the use of burst-mode control.

SYNTHESIS OF GENERALIZED CHEBYSHEV LOSSY BANDSTOP FILTERS WITH NON-PARACONJUGATE TRANSMISSION ZEROS

A systematic procedure is presented for synthesis of generalized Chebyshev lossy bandstop filters with non-paraconjugate transmission zeros. From a lossy scattering parameters with the prescribed reflection zeros, the transformation formulas from the scattering matrix to the admittance matrix are obtained by reconstructing the non-paraconjugate transmission zeros as paraconjugate ones. The canonical transversal array is modeled by partial fraction expansion of the normalized admittance functions, resulting in an increased order of the final network provided there are nonparaconjugate transmission zeros. The methods are simpler and more general than the ones in the literature. So it shows great versatility, and can also accommodate lossless network or a transfer function with symmetrical transmission zeros. To illustrate the proposed synthesis procedure, three typical examples have been carried out to validate the synthesis method.

Least Upper Bounds of the Powers Extracted and Scattered by Bi-anisotropic Particles

The least upper bounds of the powers extracted and scattered by bi-anisotropic particles are investigated analytically. A rigorous derivation for particles having invertible polarizability tensors is presented, and the particles with singular polarizability tensors that have been reported in the literature are treated explicitly. The analysis concludes that previous upper bounds presented for isotropic particles can be extrapolated to bi-anisotropic particles. In particular, it is shown that neither nonreciprocal nor magnetoelectric coupling phenomena can further increase those upper bounds on the extracted and scattered powers. The outcomes are illustrated further with approximate circuit model examples of two dipole antennas connected via a generic lossless network.

Coupling Matrix Synthesis of Nonreciprocal Lossless Two-Port Networks Using Gyrators and Inverters

A coupling matrix technique is presented for the synthesis of nonreciprocal lossless two-port networks. This technique introduces complex inverters to build the nonreciprocal transversal network corresponding to the nonreciprocal coupling matrix. It subsequently transforms this matrix into canonical topologies through complex similarity transformations. The complex inverters in the final topology are transformed into real inverters and gyrators for implementation simplicity. A second-order network example and a fourth-order network example, as well as an experimental validation, are then provided to illustrate the proposed technique. Finally, other possible implementations of the nonreciprocal gyrators are discussed.

Systematic Design of Large-Scale Multiport Decoupling Networks

In radio-frequency systems that drive coupled dissipative loads, the matching network between the amplifiers and their loads needs to account for the coupling. With N amplifiers driving N loads, a favorite choice is a “decoupling” network, which is a lossless reciprocal network that has N input ports connected to the sources and N output ports connected to the loads. The decoupling network transforms the coupled impedance of the loads into the uncoupled characteristic impedance of the sources. Any incident signal at the input ports of the network is transferred, without reflection, to the loads. Decoupling networks can be realized by generalized Π-networks of lumped and distributed impedances, depending on the design frequency. Although the impedance requirements of the network are unique, its realization is not, and networks that involve many impedances can be difficult to lay out on circuit boards. In this paper, we establish that a decoupling network requires a minimum of N 2 +N impedances for N arbitrarily coupled loads, and provide a systematic method for realizing this lower bound. We also provide methods for selectively eliminating impedances. We give an example where only 4N impedances are needed for loads that have coupling symmetry. Applications of the methods are presented.

Multiple Beams From Planar Arrays

The paper describes a general theory of Multiple Beams from Planar Arrays establishing necessary and sufficient conditions for admitting a realizable lossless beamforming network. The developed theory applies concepts deriving from the Whittaker-Kotelnikov-Shannon (WKS) sampling theory, and from its multidimensional extension due to Miyakawa- Petersen- Middleton (MPM), to the problem of generating simultaneous multiple beams from planar phased arrays with generic periodicity and layout. It is proven that the multiple beams positions must satisfy certain reciprocal lattice conditions and that the phase steering vectors of the lossless beamforming network must correspond to the multi-dimensional discrete Fourier transform (MD-DFT). The nontrivial Hermitian orthogonality of the steering vectors, as well as of the multiple beams, is also proven.

A Lossless Beam-Forming Network for Linear Arrays Based on Overlapped Sub-Arrays

A novel lossless beam-forming network (BFN) architecture for limited field of view and multi-beam linear arrays is introduced. The BFN, which is based on the overlapped sub-array technique, presents a number of advantages if compared to previous architectures. The most attractive feature consists in a substantial reduction of the number of control elements and associated active devices (i.e., amplifiers, variable phase shifters, etc.). This advantage is achieved adopting a lossless topology with reduced implementation complexity together with a rigorous and analytical design methodology which allows to fully define the BFN at architectural level and to optimize the sub-array radiation pattern in a least mean square error sense.

Multimode beamforming networks for space applications

Increased demand for narrow multi-linguistic beams, and a reduction in the number of antennas for multi-spot systems, are revitalizing the need for lossless multimode networks at various frequencies. This paper reviews basic concepts, techniques, and technologies of multimode beamforming networks for satellite multiple beams and reconfigurable antennas.

Power Balance Theorem of Frequency Domain and Its Application

This paper proves a power balance theorem of frequency domain. It becomes another circuit law concerning power conservation after Tellegen’s theorem. Moreover the universality and importance worth of application of the theorem are introduced in this paper. Various calculation of frequency domain in nonlinear circuit possess fixed intrinsic rule. There exists the mutual influence of nonlinear coupling among various harmonics. But every harmonic component must observe individually KCL, KVL and conservation of complex power in nonlinear circuit. It is a lossless network that the nonlinear conservative system with excited source has not dissipative element. The theorem proved by this paper can directly be used to find the main harmonic solutions of the lossless circuit. The results of solution are consistent with the balancing condition of reactive power, and accord with the traditional harmonic analysis method. This paper demonstrates that the lossless network can universally produce chaos. The phase portrait is related closely to the initial conditions, thus it is not an attractor. Furthermore it also reveals the difference between the attractiveness and boundedness for chaos.

Design, optimization, and realization of a wire antenna with a 25:1 bandwidth ratio for terrestrial communications

Wire antennas can be made wideband if the antenna is loaded with passive elements and connected to a lossless matching network. However, realization of the load component values and matching network can easily become impractical. In this study, using only a surface mount and standard component values, antenna loads and a matching network are optimized using genetic algorithms. The optimized design achieves a 25:1 bandwidth ratio, from 20 MHz to 500 MHz, with a maximum voltage standing wave ratio (VSWR) of 3.5 and minimum system gain of --5 dBi. The antenna system gain at azimuth is taken as the objective function and an exact penalty function is formulated to take into account the VSWR over the design frequency band. A loaded antenna is built and measured to corroborate the simulations results. The realized antenna is only 0.14 lambda long at 20 MHz.

A Structure-Preserving Model and Sufficient Condition for Frequency Synchronization of Lossless Droop Inverter-Based AC Networks

This paper presents a new method for analysis of frequency synchronization of lossless power networks whose sources are frequency-droop controlled inverters. Unlike most existing approaches, our method focuses on the interaction between inverters and the network to provide new physical insight into how those interactions create frequency synchronization. We introduce two structure-preserving models of such a network (one bus-oriented and one line-oriented), and show that frequency synchronization corresponds to convergence to an equilibrium of these models. We derive a necessary condition for existence of such equilibria, and determine a simple test for their local stability. Finally, we introduce a sufficient condition for frequency synchronization of such networks, and show that it consists of a set of local criteria which can each be determined from local measurements.

Design automation of a lossless multiport network and its application to image filtering

The paper presents expert tools which are elaborated on the basis of synthesis method of lossless nonreciprocal multiport circuits, composed of gyrators and capacitors. The algorithms are written in C++ and the tools compose a user friendly environment for design automation of filters, filter pairs and filter banks. It is possible to design in this environment not only classical structures like Butterworth, Chebyshev, and Cauer (elliptic) filters. The lossless nonreciprocal prototype circuit allows to design more complex filters, including allpass sections necessary to improve filter phase characteristics. However, the most important possibility is to design multiport circuits, especially in the case of not fully determined filter specifications. On each stage of the design process VHDL-AMS is used to describe the circuits. The obtained prototype gyrator-capacitor circuit can be implemented in OTA-C, SC (switched-capacitor) or SI (switched-current) techniques to realize the filter in CMOS technology. In the paper SI technique is used for layout generation of an image filter in order to illustrate the elaborated synthesis algorithms and tools.

Don't drop, detour!

Today's data centers must support a range of workloads with different demands. While existing approaches handle routine traffic smoothly, ephemeral but intense hotspots cause excessive packet loss and severely degrade performance. This loss occurs even though the congestion is typically highly localized, with spare buffer capacity available at nearby switches. We argue that switches should share buffer capacity to effectively handle this spot congestion without the latency or monetary hit of deploying large buffers at individual switches. We present detour-induced buffer sharing (DIBS), a mechanism that achieves a near lossless network without requiring additional buffers. Using DIBS, a congested switch detours packets randomly to neighboring switches to avoid dropping the packets. We implement DIBS in hardware, on software routers in a testbed, and in simulation, and we demonstrate that it reduces the 99th percentile of query completion time by 85%, with very little impact on background traffic.

Improving Delay-Based Data Dissemination Protocol in VANETs with Network Coding

In vehicular ad hoc networks (VANETs), for a large number of applications, the destination of relevant information such as alerts, is the whole set of vehicles located inside a given area. Therefore dissemination with efficient broadcast is an essential communication primitive. One of the families of broadcast protocols suitable for such networks, is the family of delay-based broadcast protocols, where farthest receivers retransmit first and where transmissions also act as implicit acknowledgements. For lossless networks, such protocols may approach the optimum efficiency. However with realistic loss models of VANET wireless communication, their performance is noticeably degraded. This is because packet losses have a double effect: directly on the amount of successfully received packets and indirectly with implicit acknowledgement misses. In this article, in order to combat the effects of packet losses, we combine delay-based broadcast with network coding, through a new protocol: Delay-based Opportunistic Network Coding protocol (DONC). By design, DONC aims at cancelling the twofold effects of packet and implicit acknowledgement losses. We describe the details of the DONC protocol, and we study its behavior, with realistic models and simulations. Results illustrate the excellent performance of the protocol.

THEORY AND REALIZATION OF SIMPLE BANDPASS FILTERS WITH ANTIPARALLEL CONFIGURATION

This paper introduces a theoretical analysis as well as a design example for bandpass fllters (BPF) with a distinctive topology. Based on the analysis of simple two-port symmetrical lossless networks with a parallel structure, a method for obtaining normalized BPF prototypes with desired bandwidths was developed. These prototypes can be scaled to any central frequency and symmetrical real termination in the same way as conventional fllters. It is also demonstrated that with a slight modiflcation of the basic BPF prototypes, transmission zeros with controllable frequencies can be introduced in both the lower and the upper stopband region. Such modifled prototypes are more convenient for the realization of printed fllters than the basic BPF prototypes. The proposed fllters have almost identical characteristics in the broad vicinity of the passband region either when composed of ideal lumped elements or of transmission lines (TLs). Due to its simplicity, the proposed concept could be applied for the realization of a printed BPF at a large variety of PCB types, substrates and practical design conflgurations. A microstrip BPF model is realized for the experimental veriflcation of the presented theory. The measured and theoretical results show excellent agreement, conflrming the proposed concept and the exactness of the methodology.