In this paper, a D-shaped defected patch antenna printed on a microwave substrate for increasing the bandwidth of a microstrip antenna is proposed. A second resonant frequency is introduced to achieve a wider impedance bandwidth with D-shaped defected structure. The effects of the proposed antenna structure parameters are studied in details. By simulation software, we obtained the size of an antenna operating around at 2.4GHz. The measured parameters and simulation results show that the proposed antenna can attain the impedance bandwidth that is much broader than the traditional rectangular patch antenna.

In the paper, we propose and design a ring-topology wavelength-division-multiplexing (WDM) access network for long-reach signal transmission. Here, the new central office (CO) and optical network unit (ONU) modules are designed to construct the ring-based architecture for symmetric data connection. Thus, the Rayleigh backscattering (RB) beat noise can be prevented due to the unidirectional downstream and upstream signal connections. In the demonstration, eight WDM wavelengths with 10 Gbit/s on-off keying (OOK) modulation are applied to serve as the symmetric downstream and upstream traffic through 105 km fiber connection without dispersion compensation. In addition, the minimum power budgets of 33.8, 36.1 and 35.4 dB among the eight WDM wavelengths can be obtained at the back-to-back (BtB), 51 and 105 km fiber links, respectively, under the forward error correction (FEC) target. INDEX TERMS Rayleigh backscattering (RB), WDM-PON, OOK modulation, Ring-topology.

No abstract

No abstract

With the rapid development of wireless communication techniques, the main limitations of wireless communications lie in spectrum resource constraints and nonlinearity of high amplifier power (HPA). Albeit exploring high-order modulation improves the spectrum efficiency significantly, however, the nonlinear distortion seriously degrades the performance especially when nonlinearity sensitive high-order non-constant envelop modulation signal pass through the saturate regime of HPA. Due to the good performance in linearization, adaptive baseband digital pre-distortion has been widely developed and applied. Particularly, the optimization of the parameters for adaptive pre-distortion algorithm has a positive impact on linearization. In this paper, an improved algorithm is proposed to determine the optimum step by taking maximum error vector magnitude EVM improvement as the objective function. And thus the nonlinearity of power amplifier is compensated with indirect learning architecture and optimum step adaptive algorithm. Simulation results demonstrate that the constellations are well compensated and out-band power spectrum regenerations are significantly suppressed, which yields a satisfactory system performance linearization.