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Helical gratings (HGs) have an achievement of flexible mode conversion for fibre‐guided orbital angular momentum (OAM) modes. Sampled reflection HGs can realise the generation and conversion of OAM mode with comb spectra. They can be used to simultaneously filter wavelengths and convert modes, and thus may be applied to the hybrid multiplexing technology with wavelength division multiplexing and mode‐division multiplexing. [ABSTRACT FROM AUTHOR]

A novel miniaturised dual‐band bandpass filter (BPF) using improved split ring λ/4 resonator and stepped impedance resonator (SIR) is proposed. A simple analysis is given for each resonator. By tuning the geometric parameters of the resonators, the two passbands of the BPF can be adjusted separately. Source‐load coupling is adopted to achieve more transmission zeros in the stopband. The new dual‐band BPF, which has a miniature circuit size of 0.18 × 0.18λg, presents narrow and sharp passband characteristics. Good agreement is found between simulated and measured results, which verify the high‐frequency selectivity. [ABSTRACT FROM AUTHOR]

A novel dual‐band Wilkinson power divider (WPD) is designed for the purpose of operating at two arbitrary frequencies. The theory and design procedure of the novel component are presented in detail. For demonstration, a dual‐band WPD with operating frequencies of 1.0 and 2.6 GHz is proposed, fabricated and tested. The good agreement between the measured and simulated results confirmed the design concept. Measurements show that insert losses both at the two central frequencies are less than 3.3 dB. Both return loss and port isolation have good performances, which are more than 21 and 28 dB separately. [ABSTRACT FROM AUTHOR]

A multi‐stage least mean square (MLMS) algorithm based on polynomial fitting in time‐varying systems is proposed. As the name implies, the MLMS algorithm is divided into different stages in sequence. In non‐stationary environments, the optimal weight coefficients of the adaptive filter are variable with time and they are assumed to be approximated by a polynomial. According to the conditions above, the convergence of the MLMS algorithm is verified through theoretical analysis and formula derivation. Similar to the least mean square (LMS) algorithm, the step size μ must be chosen in the specific range to guarantee the feasibility and effectiveness of the MLMS algorithm. Compared with the LMS, LMF and NLMS algorithms, the MLMS algorithm provides the best convergence performance in the simulation experiments. [ABSTRACT FROM AUTHOR]