Biorthogonal Fourier transform (BFT), consistent with the matched signal transform (MST), has been introduced to demodulate the M-ray chirp-rate signal which possesses good orthogonality in the BFT domain. Here, we analyze the characteristics of BFT detection in a further step, including the resolution capability of the multichirp-rate signal, the property of pulse compression, the closed-form bit-error rate in the additive white Gaussian noise (AWGN) channel, and the interference in the time-frequency dispersive channel. Even in the high Doppler environment, the shift in BFT detection is proven to be slight. In addition, we deduce that the orthogonality among received chirp rates in the BFT domain would be affected in the multipath dispersive environment. This causes the mutual interference among different chirp rates in a symbol and over symbols concurrently. The theoretical result shows that the chirp modulation parameter can be adjusted to obtain the trade-off between time and frequency dispersion. By the multipath model of chirp-rate signal, an auxiliary parallel interference cancellation (PIC) method is further introduced in multipath environment. Simulations verify our analyzed performance of BFT detection in the AWGN, Doppler, and multipath channels. The proposed interference cancellation algorithms are also proven to be effective.

This paper proposes an approach for calculating the transmission ratio of nutation drive based on the working principle of the nutation movements. Then, the analysis of the influences for the nutation angle on the transmission ratio is carried out. The controllable tooth profile modelling for external and internal spiral bevel gears with double circular-arc is proposed. Based on the proposed tooth profile modeling, the three dimensional modeling and virtual assembly of the nutation drive have been further completed. Finally, the kinematical simulation is preceded in the simulating system and the comparative results have been accomplished between the simulation results and the theoretical ones of the transmission ratio.

In fast-fading scattering environments such as high-speed rail and low-altitude communications, mobile communication systems need to quickly and robustly estimate and equalize fast-fading, time-varying channels. Under these circumstances, noncoherent multiple-input multiple-output (MIMO) has received attention in recent years, since it is less influenced by factors such as phase fluctuations and has fewer requirements for channel estimation and synchronization. Spatial multiplexing MIMO-MFSK based on energy detection is different from conventional noncoherent MIMO in that it can achieve higher spatial multiplexing gain in the independent distribution of channel fading statistics. At the receiver, partial real channel state information (CSI) is available, which can improve the capacity while ensuring the reliability of the link. With partial real CSI replacing instantaneous CSI, the system performance is inferior to conventional coherent MIMO under the influence of noise. As a result, it is necessary to analyze its theoretical detection performance. By energy detection, the noise of the MIMO-MFSK system conforms to the generalized gamma distribution. On the basis of this distribution, the optimal decision rule of the system and the symbol error rate (SER) formula are derived. Additionally, we investigate the signal-dependent noise problem of minimum Euclidean distance detection. Numerical results show that the SER formula fits well with the simulation results under the condition of a high signal-to-noise ratio.

The noncoherent multiple-input multiple-output (MIMO) system is inevitably subject to cross-product interference among different spatial channels, arising the problem on solution of nonlinear model. In this letter, we propose a common difference processing framework based on dual-frequency complementary (DFC) waveform, aiming to generate an opposite cross-product term to eliminate interference. Thus, it can turn the nonlinear MIMO model into a linear one to facilitate the use of linear detectors. In our framework, two linear models are derived for MIMO with energy detection (ED) and differential detection (DD). Finally, through the complexity analysis of detectors and performance simulation results, the proposed framework is demonstrated to be a proper candidate for low-complexity implementation of noncoherent spatial multiplexing.