This paper presents a detailed study of N-channels Wavelength Division Multiplexing (WDM) Optical transmission system using Radio over Fiber (RoF) technology. The study was applied to optical long-haul networks to overcome the nonlinearity effects, chromatic dispersion, and signal loss. For this purpose, Fiber Bragg Grating (FBG) has been implemented in 4-channels, 8-channels, and 16 channels WDM transmission system network at 10 Gb/s to compensate the dispersion and the nonlinear distortion. The use of erbium-doped fiber amplifiers (EDFA) has been also investigated to improve the quality of the transmission system. In Digital RoF, the impact analysis of modulation types such as Differential Phase-Shift Keying (DPSK) and Quadrature Amplitude Modulation (QAM) is also introduced. Constellation diagrams, received optical power, types of modulation, fiber dispersion, channel spacing variation, and laser power were considered to validate the study with the existing studies. All results achieve good reliability performance and prove the efficiency of the presented model.

In this paper we propose a technique to design compact multi‐band and UWB bandpass filters based on coupled half wave resonators. The proposed design consists of the modification of a conventional parallel coupled Chebyshev bandpass filter structure by setting a very small or null coupling gap between the resonators of the center sections jointly with a very small spacing between resonators of the extremity sections. This spacing determines the performances of selected frequency bands. An ultrawideband response is accomplished by applying null spacing between all the adjacent resonators. We analysed the effect of the separation distance between the coupled lines on both the fractional bandwidth and group velocity of the filter response. The effect of the order assumed for the initial Chebyshev filter was also discussed. As an illustration of the proposed technique, we designed and measured a dual band and a tri‐band filter for the frequencies covering the WiMAX/WLAN/X system bands demonstrating an excellent performance, with a fractional bandwidth covering the 40% and 100% of the FCC bandwidth respectively. The proposed technique alleviates the fabrication accuracy requirements. The designs show an optimal improvement in terms of group velocity flatness.

In this paper, a low-cost compact microstrip ultra wideband antenna for satellite and radar communication systems with filtering properties resulting multiband characteristics is presented. The ultra wideband antenna consists of a modified rectangular radiating element with deformed ground plane which provides a wide bandwidth from 5 to 16 GHz. The U-shaped slots are introduced in the radiating patch to obtain the tri-band frequency response covering C, X and Ku bands separately. The frequency bands achieving are 4.9-7 GHz, 7.92-11.08 GHz and 11.85-15.94 GHz. The proposed antennas are successfully simulated and performed using CST MWs and experimental validation are presented to demonstrate the performance of these antennas.

Ultra-wide band (UWB) technology has become more popular due to various applications such as ground penetrating radar, medical imaging and sensor networks. The antenna is one of the key components of UWB systems and has drawn much attention in recent years. In this paper we propose the design of UWB monopole antenna, providing single notched-band for WLAN (5–6) GHz to avoid interference signals, using complementary split ring resonators CSRR and spiral resonator CSR. It consists of a microstrip patch with modified radiating element and ground plane, while the desired notch-band characteristic is achieved by etching separately CSRR and SCR in the radiating patch, in Fig.1. Investigations on the parameters of the CSRR were performed to obtain the same performance of CSR in high frequency keeping away it second resonance. Fig.2 shows simulated and measured return loss of proposed single notched-band UWB monopole antennas, compared to the antenna without filtering property. It can be seen that the monopole antenna covers the whole UWB band (3–11 GHz) with a good rejection of WLAN band for notched-band antennas. Also a good response is observed in high frequency of UWB band. for the antennas gain, it varies between 3dBi and 5 dBi. From it performances, The proposed antennas are a good candidate for UWB applications where notch-band for WLAN is required. All results indicate that the investigated CSSR works effectively to introduce a single notch-band characteristic for the UWB antenna, like CSR performances.