A main distinguishing feature of a wireless network compared with a wired network is its broadcast nature, in which the signal transmitted by a node may reach several other nodes, and a node may receive signals from several other nodes simultaneously. Rather than a blessing, this feature is treated more as an interference-inducing nuisance in most wireless networks today (e.g., IEEE 802.11). The goal of this paper is to show how the concept of network coding can be applied at the physical layer to turn the broadcast property into a capacity-boosting advantage in wireless ad hoc networks. Specifically, we propose a physical-layer network coding (PNC) scheme to coordinate transmissions among nodes. In contrast to "straightforward" network coding which performs coding arithmetic on digital bit streams after they have been received, PNC makes use of the additive nature of simultaneously arriving electromagnetic (EM) waves for equivalent coding operation. PNC can yield higher capacity than straight-forward network coding when applied to wireless networks. We believe this is a first paper that ventures into EM-wave-based network coding at the physical layer and demonstrates its potential for boosting network capacity. PNC opens up a whole new research area because of its implications and new design requirements for the physical, MAC, and network layers of ad hoc wireless stations. The resolution of the many outstanding but interesting issues in PNC may lead to a revolutionary new paradigm for wireless ad hoc networking.

Hot topic: physical-layer network coding

The progress in the field of wireless power transfer in the last few years is remarkable. With recent research, transferring power across large air gaps has been achieved. Both small and large electric equipment have been proposed, e.g., wireless power transfer for small equipment (mobile phones and laptops) and for large equipment (electric vehicles). Furthermore, replacing every cord with wireless power transfer is proposed. The coupled mode theory was proposed in 2006 and proven in 2007. Magnetic and electric resonant couplings allow power to traverse large air gaps with high efficiency. This technology is closely related to electromagnetic induction and has been applied to antennas and resonators used for filters in communication technology. We have studied these phenomena and technologies using equivalent circuits, which is a more familiar format for electrical engineers than the coupled mode theory. In this paper, we analyzed the relationship between maximum efficiency air gap using equivalent circuits and the Neumann formula and proposed equations for the conditions required to achieve maximum efficiency for a given air gap. The results of these equations match well with the results of electromagnetic field analysis and experiments.

Maximizing Air Gap and Efficiency of Magnetic Resonant Coupling for Wireless Power Transfer Using Equivalent Circuit and Neumann Formula

Planar circuits for microwaves and lightwaves

This paper presents a low-profile dual-band filtering antenna element and its application to long-term evolution (LTE) multiple-input multiple-output (MIMO) system for wireless customer premise equipments (CPEs). The proposed element consists of two separate U-shaped patches operating at different frequencies and a multistub microstrip feed line. For size miniaturization, the smaller U-shaped patch is embedded in the larger one. In addition, the multistub feed line can generate two controllable resonant modes as well as two nulls in realized gain at the boresight direction. Since the modes of the patches and multistub feed line can be controlled individually, the two operating bands can be tuned to desired frequencies. Also, the radiation nulls in boresight gain can be controlled, high roll-off rate and out-of-band radiation rejection levels are thus obtained. For demonstration, a low profile ( $0.009\lambda _{0})$ dual-band filtering antenna element operating at 1.9 and 2.6 GHz for TD-LTE applications (B39- and B38-bands) is implemented. Dual-band bandpass responses and four radiation nulls are observed in the experiment. Measured in-band gains are 6.7 and 7.3 dBi, whereas out-of-band gains are less than −10 dBi. Based on this element, a four-element MIMO antenna is further designed for LTE CPEs, where low profile and high integration of multiple components are required. A low mutual coupling of less than −19.2 dB and the low envelope correlation coefficients of better than 0.2 are obtained with a small edge-to-edge spacing of $0.15\lambda _{0}$ .

Low-Profile Dual-Band Filtering Patch Antenna and Its Application to LTE MIMO System

We review progress in the development and applications of superconducting metamaterials. The review is organized in terms of several distinct advantages and unique properties brought to the metamaterials field by superconductivity. These include the low-loss nature of the meta-atoms, their compact structure, their extraordinary degree of nonlinearity and tunability, magnetic flux quantization and the Josephson effect, quantum effects in which photons interact with quantized energy levels in the meta-atom, as well as strong diamagnetism.

Progress in Superconducting Metamaterials

A circular cavity resonance method is improved to measure the frequency dependence of complex permittivity of a dielectric plate by using multimode TE 0m1 with integer m of the higher order. The measurement principle is based on a rigorous analysis by the Ritz-Galerkin method. A new circular cavity with lowered height is designed to decrease the number of unwanted modes near the TE 0m1 modes from a mode chart of a cavity. Then the frequency dependence of a glass cloth PTFE dielectric plate is measured over the frequency range 15∼35GHz by using TE 0m1 (m=1, 2, 3, 4) modes in a circular cavity designed at 20GHz for the TE 011 mode. The measured results are compared with ones measured by using the conventional four different size cavities with TE 011 mode. It is verified that the designed cavity structure is useful to measure the frequency dependence of a dielectric plate.

Frequency dependence measurements of complex permittivity of a dielectric plate by using TE 0m1 modes in a circular cavity

Relative conductivity measurements of a copper-clad dielectric substrate using a sapphire rod resonator

A novel compact quasi-millimeter-wave UWB bandpass filter (BPF) with a midband frequency of 26 GHz and a fractional bandwidth of 20% is developed for automotive radar systems. Based on the even- and odd-mode method, analytical closed-form formulas are derived first for accurate design of two microstrip stubs-loaded multi-mode ring resonators with pre-designated bandwidths and multiple transmission zeros in their stopbands. Then a UWB BPF is configured by cascading these two ring resonators and a parallel-coupled step-impedance resonator. The filter exhibits desired wide passband with a minimum measured insertion loss of 1.8dB, sharp attenuations near the passband, and very wide stopband with measured attenuations larger than 30dB over 10–40GHz. The Federal Communications Commission's UWB indoor limit is satisfied quite well.

A novel compact high-performance microstrip 26GHz ultra-wideband (UWB) bandpass filter for vehicle radar systems

In this paper, a millimeter-wave wideband bandpass filter is proposed and designed by using novel slotted substrate integrated waveguide (SIW) units. The unit consists of two pairs of same size dumbbell slots etched on both the top and bottom metal planes of the SIW. The slots act as shunt resonators, which reduce the filter size and produce transmission zeros simultaneously. A five-order bandpass with a center frequency of 32.5 GHz and a 3dB fractional bandwidth of 34.6% is developed, and it is small in size, and low loss with a measured insertion loss of 1.54 dB at the center frequency.

Millimeter-wave wideband bandpass filter using novel slotted substrate integrated waveguide

A parallel version of Method of Moments (MoM) with Higher-Order Basis functions (HOB-MoM) with the Out-of-Core technique (OOC) is proposed to compute the Radar Cross Section (RCS) of an aircraft with engine inlets in this paper. The block-partitioned parallel scheme for the large dense MoM matrix is designed to achieve excellent load balancing and high parallel efficiency. The OOC technology is employed to break through the random access memory (RAM) limitation. Some numerical results demonstrate that the higher-order basis used in this paper is superior to the conventional RWG basis and is suitable to solve various electrically large problems such as the computation of RCS.

http://ap-s.ei.tuat.ac.jp/isapx/2013/pdf/158_2_0.pdf

Accurate evaluation of RCS on the structure of aircraft inlets

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