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Том 62, № 9 (2019)
- Год: 2019
- Статей: 4
- URL: https://journals.rcsi.science/0735-2727/issue/view/10950
Article
Two Resonances of Parametric Time Varying Circuit (Review)
Аннотация
The theory of parametric time varying circuit is of interest as an introduction to the theory of nonlinear circuit. As follows from the principle of linear representation, which is little known in radio electronics, it is advisable to select for analysis the parametric time varying circuit in the most general form. The significance of ordinary circuit for practice is stipulated by the phenomenon of resonance that is also intrinsic) to the parametric time varying circuit. The resonance theory of the latter is not easy due to the need of sophisticated mathematical apparatus. In addition, two resonances, similar by their names, but quite different in essence manifest themselves in a parametric time varying circuit, namely, parametric resonance and the resonance of parametric time varying circuit. The parametric resonance is the characteristic of free processes in the circuit. This resonance is identified with an unstable circuit when its free process tends to rise to infinity with time. The resonance of parametric time varying circuit is a direst generalization of the resonance of ordinary circuit and represents the characteristic of forced oscillations. These two fundamentally different phenomena have similar names that is inconvenient for practice. Therefore, we propose to name the last of two resonances as “classical resonance”. Below we present an analysis of both resonances in a more general form than can be found in available literature.
431-448
Distributed Reed Muller Code with Multiple Relays for Cooperative Broadband Wireless Networks
Аннотация
The authors have investigated the bit-error rate (BER) performance of Reed-Muller coded cooperative single-carrier frequency domain equalization (RMCC-SC-FDE) scheme and Reed-Muller coded cooperativeOFDM(RMCC-OFDM) scheme incorporating multiple relays and multiple antennas. The maximum ratio combining (MRC) technique is utilized for OFDM/SC-FDE signal detection at the destination terminal. The joint soft maximum likelihood decoding (JSMLD) and the joint majority logic decoding (JMLD) are employed at the destination terminal. The deployment of multiple relays have invigorated the BER performance of RMCC-OFDM and RMCC-SC-FDE schemes. Numerical results demonstrate that the RMCC-SC-FDE scheme exhibits a betterBERperformance over theRMCC-OFDM scheme in identical conditions. Furthermore, the simulated results reveal that the RMCC-SC-FDE and RMCC-OFDM schemes not only yield a better BER performance gain over their corresponding non-cooperative coded counterpart schemes but also outperform the turbo coded cooperative SC-FDE and turbo coded cooperative OFDM schemes, respectively, under identical conditions.
449-461
Mode Mixing Suppression Algorithm for Empirical Mode Decomposition Based on Self-Filtering Method
Аннотация
The Hilbert-Huang transform (HHT) is a classic method in time-frequency analysis field which was proposed in 1998. Since it is not limited by signal type, it is generally applied in medicine, target detection and so on. Empirical mode decomposition (EMD) is a pre-processing part of HHT. However, EMD still has many imperfect aspects, such as envelope fitting, the endpoint effect, mode mixing and other issues, of which the most important issue is the mode mixing. This paper proposes a mode mixing suppression algorithm based on self-filtering method using frequency conversion. The proposed algorithm focuses on the instantaneous frequency estimation and the false components removing procedures, which help the proposed algorithm to update or purify the designated intrinsic mode function (IMF). According the simulation results, the proposed algorithm can effectively suppress the mode mixing. Comparing with ensemble empirical mode decomposition (EEMD) and mask method, the suppression performance is increased by 26%.
462-473
Dual Band Reconfigurable Compact Circular Slot Antenna for WiMAX and X-Band Applications
Аннотация
A circular slotted reconfigurable antenna for WIMAX and X-band wireless communication applications is presented. The aim of this article is to design an antenna, which can operate at dual band with high gain. The designed antenna is compact in size with dimensions 32–24 mm.CPWfeeding is used in the design of frequency reconfigurable antenna, and BAR-64-20V PIN diodes are installed for frequency tuning operation. By employing a T-shaped resonator inside the circular slot and a parallel resonator in transmission line, the dual band operation is realized. The antenna covers WiMAX (3.1–4.5 GHz) and X-band (10.3–11.7 GHz) for such applications as space research and mobile radio astronomy. Frequency switching is attained by the proper positioning of PIN diodes at the circular slot. The proposed compact antenna shows good radiation characteristics and good impedance bandwidth.
474-485