Yuze Liu

A New Dual-Frequency Wilkinson Power Divider

In this article, a novel and simple dual-frequency Wilkinson power divider is proposed. Considering that there is only one section of transmission line linking the input port and the output port directly as a part of the transformer, this power divider is very compact. To satisfy the dual-frequency characteristic, the traditional quarter-wavelength transformer is replaced by the structure which consists of a section of transmission line and a parallel stub at the input port. Besides, in order to obtain the ideal isolation with keeping the ideal matching at the output ports, a resistorr R and series LC components are added. Furthermore, closed-form design equations of this proposed power divider are obtained to simplify the design procedure. The simulation results of four examples indicate that all the features of the power divider can be fulfilled at dual-frequency simultaneously. Furthermore, measurement results of a fabricated power divider operating at 1 GHz and 4 GHz verify the design concept of this proposed power divider.

A Compact Open Slot Antenna for UWB Applications with Band-Notched Characteristic

A compact open slot antenna for ultra-wideband (UWB) applications with band-notched function is presented and investigated. To achieve partial band cutoff, two symmetrical slits are used. Ultra wideband performance is obtained by introducing a stepped strip. A prototype of the proposed antenna is fabricated and its performance is simulated and measured. The measured results show that the antenna of 26.5 mm× 12 mm × 1.5 mm dimensions sufficiently covers the band of UWB from 2.95 GHz to more than 12 GHz excluding the rejection band from 5.1 GHz to 6.0 GHz. The antenna also shows stable gain and constant group delay across the UWB band.

A novel wide-band hybrid coupler using coupled-line power divider and improved coupled-line phase shifter

A novel hybrid coupler aiming for wide-band applications is proposed in this paper. This hybrid coupler consists of a broadband Wilkinson coupled-line power divider and an improved wide-band coupled-line phase shifter. Taking advantage of the coupled-line section, the power divider achieves both compact circuit configuration and wide-band performance. In lieu of patterned ground plane and lumped capacitors, the coupled-line phase shifter can be constructed on a single-layer printed circuit board for wide-band operation. For this proposed phase shifter, the scattering parameters (S-parameters) expressions are derived and the optimal structural design parameters for achieving zero reflection coefficients are highlighted. After carefully choosing the circuit parameters, a new wide-band hybrid is constructed by combining a power divider and the proposed phase shifter. To verify against the theoretical calculation in terms of S parameters and phase information, a hybrid operating at 3 GHz is designed, simulated, and fabricated through microstrip technology. Close agreement is obtained between simulation and measurement results.

A novel 180° rat-race hybrid with arbitrary power division for complex impedances

A generalized compact rat-race 180° hybrid with arbitrary power division ratio for matching complex impedance loads is presented in this paper. The proposed structure consists of four-section transmission lines, which is similar to the shape of the traditional hybrid. Compared with the conventional hybrid coupler, this design can be terminated with arbitrary complex impedances and realize high power-split ratio. Because of the symmetry of the proposed structure, it can be calculated by even–odd mode analysis and matrix. The explicit closed-form equations are derived analytically. The bandwidth variations are mainly discussed and simulated. For verifying the validity of this design, a microstrip prototype for 13.98 dB power-split ratio is simulated, fabricated, and measured. The measured performance shows a good agreement with the simulated results.

A novel wideband coupled-line Gysel power divider with function of impedance matching

A new coupled-line circuit structure is proposed to design compact wideband Gysel power dividers with function of impedance matching between source and load. Based on traditional even- and odd-mode technique, closed-form equations are obtained for direct and accurate synthesis. By applying coupled lines and reducing their electrical lengths, this novel Gysel power divider has four main advantages: high power-handling capability, small size, enhanced bandwidth, and source-to-load impedance matching. The measured bandwidth ( & dB) of the fabricated Gysel power divider operating at 2 GHz is 62.6%, while the traditional one is 40.8%. Meanwhile, the size of this novel Gysel power divider is only 25.5% of the traditional one when the same substrate is used and the same operating band is considered.

A New Symmetric Modified Wilkinson Power Divider Using L-Type Dual-Band Impedance Matching Structure

Based on L-type dual-band impedance matching structure, this paper presents a new symmetric modified Wilkinson power divider for dual-band applications. In the matching structure, two transmission line stubs can be used to implement impedance matching and space isolation for two transmission ways, simultaneously. In the isolation structure, a single resistor is applied, and the design values are adjusted according to the center frequency ratio. In this proposed power divider, the ideal matching of all ports, equal power splitting and isolation between the output ports can be achieved. Theoretically, the nonlinear design equations for normalized parameters are directly derived based on the conventional even- and odd-mode analysis. In microstrip experiments, simulated and measured results of two fabricated power dividers with different frequency ratios are given. It can be clearly seen that there are good agreements between the theoretical and experimental results.

An Asymmetric Arbitrary Branch-Line Coupler Terminated By One Group Of Complex Impedances

Abstract A novel arbitrary asymmetric branch-line coupler structure terminated by one group of complex impedances is proposed. Two left ports of the proposed branch-line coupler are terminated by equal arbitrary complex impedances, and the other two right ports are terminated by equal real impedances. Arbitrary power division ratios are feasible for the proposed structure. Using rigorous even- and odd-mode analysis and scattering parameters theory based on complex impedances, the closed-form design formulas for designing the proposed branch-line coupler is obtained. To validate the proposed structure and the given design equations, a microstrip branch-line coupler operating at the center frequency of 2.5GHz and terminated by 20 and 30 − 6j Ohm impedances is designed, simulated and measured. There is a good agreement between the simulated and measured results.

OpenFlow-based adaptive adjustment of optical path resources in dynamic optical networks

The development of broadband services gives the existing networks a tremendous pressure. It forces us to think about what measures to take, in addition to increasing the capacity, to improve the service capabilities of the networks and reduce the costs. The virtual programmable features of OpenFlow bring a lot of flexibility and convenience to the operation of networks. For the purpose of applying the programmable feature of software to future optical networks, this paper proposes a novel OpenFlow-based adaptive adjustment scheme for optical path resources. In addition, to control the underlying devices, the current standard OpenFlow protocol is extended, and four new message types are developed to communicate between OpenFlow controller and OpenFlow virtual switch (OVS). An experiment of OpenFlow-based adaptive spectrum adjustment is carried out on the experimental test-bed that we proposed to verify the feasibility of the above scheme. The experimental results demonstrate that the software control on optical connections is an effective solution to the adaptive adjustment of optical path resources in dynamic optical networks. An OpenFlow-based adaptive adjustment scheme of optical path resources is proposed.Diff-Serv and QoT-aware adjustment can be realized by the optical path adjustment.The spectrum adjustment is to solve wavelength conflict or spectrum overlap.Four new message types are developed by extending OFP.The feasibility of our scheme is verified by experiments carried out on a test-bed.

The routing, modulation level, and spectrum allocation algorithm in the virtual optical network mapping

With the development of large video services and cloud computing, the network is increasingly in the form of services. In SDON, the SDN controller holds the underlying physical resource information, thus allocating the appropriate resources and bandwidth to the VON service. However, for some services that require extremely strict QoT (quality of transmission), the shortest distance path algorithm is often unable to meet the requirements because it does not take the link spectrum resources into account. And in accordance with the choice of the most unoccupied links, there may be more spectrum fragments. So here we propose a new RMLSA (the routing, modulation Level, and spectrum allocation) algorithm to reduce the blocking probability. The results show about 40% less blocking probability than the shortest-distance algorithm and the minimum usage of the spectrum priority algorithm. This algorithm is used to satisfy strict request of QoT for demands.

Holding-time-aware asymmetric spectrum allocation in virtual optical networks

Virtual optical networks (VONs) have been considered as a promising solution to support current high-capacity dynamic traffic and achieve rapid applications deployment. Since most of the network services (e.g., high-definition video service, cloud computing, distributed storage) in VONs are provisioned by dedicated data centers, needing different amount of bandwidth resources in both directions, the network traffic is mostly asymmetric. The common strategy, symmetric provisioning of traffic in optical networks, leads to a waste of spectrum resources in such traffic patterns. In this paper, we design a holding-time-aware asymmetric spectrum allocation module based on SDON architecture and an asymmetric spectrum allocation algorithm based on the module is proposed. For the purpose of reducing spectrum resources’ waste, the algorithm attempts to reallocate the idle unidirectional spectrum slots in VONs, which are generated due to the asymmetry of services’ bidirectional bandwidth. This part of resources can be exploited by other requests, such as short-time non-VON requests. We also introduce a two-dimensional asymmetric resource model for maintaining idle spectrum resources information of VON in spectrum and time domains. Moreover, a simulation is designed to evaluate the performance of the proposed algorithm, and results show that our proposed asymmetric spectrum allocation algorithm can improve the resource waste and reduce blocking probability.