In order to test the influence of the drop channel to its adjacent channels, we input three adjacent channels which satisfy the specification of the 100 GHz DWDM system. Figure 7 shows three channels in the tunable range (1543-1546 nm) without drop any one. Then we drop the middle of the three channels, and the Figure 8 shows the measured spectrum.From the Figure 8 we can see that the drop channel has not any damnification to the adjacent channels, and the adjacent channel isolation degree N is more than 35-dB. CONCLUSIONSIn this article, we have developed a novel stack of 100 GHz DWDM four cavities interference narrowband thin film angletuned filter and a novel three-port tunable filter. It has a simple structure, stable transmission characteristics, simple light path and it is easy to be fabricated. As the novel stack is optimized, the tunable filter has eliminated the phenomenon of polarization light central wavelength separation and its polarization dependent loss is very low (Ͻ0.1-dB). The experiments demonstrate that its insertion loss is very low (Ͻ2-dB), its adjacent channel isolation degree is very high (Ͼ35-dB), and its effective tunable range of 26 nm. This device has a bright application opportunity for its flexibility, low cost, and wide tunable range. INTRODUCTIONThe electromagnetic band-gap (EBG) structures are periodical cells composed of metallic or dielectric elements. One of the most important properties of EBG structure is to prohibit the propagation of surface wave [1, 2]. Practical applications of EBG structure usually have difficulty in accommodating its physical size, because the period of EBG lattices has to be a half-wavelength at the band-gap frequency. This problem had not been solved until the mushroom-like EBG was proposed by Sievenpiper et al. [3]. Later on, several other novel EBG structures were presented such as uniplanar compact EBG (UC-EBG) [4] and fork-like EBG [5]. These structures have several advantages, such as compact size, low loss, and so on. They can be integrated with antenna to enhance the gain and reduce the backward radiation by suppressing surface wave and improving efficiency [6]. Alternatively, radiating element can be mounted above the EBG structure to form high impedance ground plane (HIP) [7]. However, because of their resonant nature, all of those structures are narrow band, which restricts them to be used in broadband application. The challenge is to produce an EBG structure with wide bandwidth.In this article, two kinds of mushroom-like EBG unit with different radius of via are cascaded to form a novel broadband structure. The effects of the radius of via and unit number on the band-gap are considered using direct transmission method [8]. The simulation and experimental results show that the band-gap of the broadband structure covers the stop-band of the two different uniform configurations with the radius of via changed. The bandgap is enlarged greatly which achieves almost 70%. MUSHROOM-LIKE EBG THEORY AND DIRECT TRANSMISSION METHODThe mushroom-like E...

Abstract-A novel compact dual-band electromagnetic band-gap (EBG) structure is proposed in this paper. The major contribution to this dual-band design is using cascaded mushroom-like units which operate at different frequencies. The position of via is moved off the center of the metal patch to get a lower resonant frequency and the effects of the radius of via are considered at the same time. The method of suspended microstrip is utilized to measure the band-gap characteristics of the EBG structures. Several dual-band EBG structures are designed and compared. Results show that this novel cascaded structure offers additional flexibility in controlling the frequencies of the stopband over a wide range. The cascaded dualband EBG structure has potential application to dual-band antenna and circuit.

Abstract-Radiation characteristics of shipborne antennas above lossy half-space are studied using the multilevel fast multipole algorithm (MLFMA). The near terms in the MLFMA are evaluated by using the rigorous half-space dyadic Green's function, computed via the method of complex images. The far MLFMA interactions employ an approximate dyadic Green's function via a direct-radiation term plus a single real image, with the image amplitude characterized by the polarization-dependent Fresnel reflection coefficient. Finally, radiation patterns of an ultra-shortwave antenna mounted on a realistic 3-D ship over seawater are presented and compared with a rigorous method-ofmoments (MoM) solution.

Abstract-In this paper we propose a new method to enhance the gain of rectangular waveguide antenna arrays using the double negative medium (DNG) structure composed of strip wires (SW) and split ring resonators (SRR). The electromagnetic parameters of the DNG structure are retrieved and the rectangular waveguide antennas with and without the DNG structure are studied using numerical simulation method. The simulation results show that the DNG structure can congregate the radiation energy when the index of refraction approximates zero, since that the gain of the antenna arrays is enhanced and the radiation performance of the antenna arrays is effectively improved. Far-field radiation patterns are measured, which indicate that this method is effective to enhance the gain.

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