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The use of antenna arrays is indispensable in radar and multiple-input multiple-output (MIMO) wireless communications areas, as it permits the treatment of wavefronts in the spatial domain, enabling important applications such as beamforming and target detection. Spatial information is commonly given in terms of spatial correlation functions (SCFs), but its representation in terms of angular domain, such as the power azimuth spectrums (PASs), is sometimes more convenient. Therefore, transforming from SCF to PAS, and vice versa, is often required. This is commonly done by employing so-called beamformers, where the Bartlett beamformer (BB) is the most commonly utilized. However, the use of beamformers alone is not enough for retrieving PAS information from a given SCF. Particularly, this paper shows that a non-linear operation is missing in relating SCFs to PASs as provided by current beamformers. The paper also shows the mathematical expressions that correctly relate SCFs to PASs and wavenumber spectrums (WNSs) for the general case of systems with antenna arrays. The developed theory results in two new beamformers, which, corroborated by simulation results, solve any previous inconsistency in estimating PASs from SCFs. [ABSTRACT FROM AUTHOR]

An inherent impedance mismatch in a controller area network with flexible data rate (CAN-FD) network gives rise to signal distortion called ringing. Ringing is one of the main causes of communication errors and performance degradation. In this paper, a ringing suppression system is proposed, which alleviates the impedance mismatch at two mismatch locations: the unterminated CAN nodes and the divergence points of bus lines. At the unterminated CAN nodes, a temporal impedance switching circuit, including a matching resistor and a limiting diode, is added. The circuit is controlled to only engage right after a dominant-to-recessive transition when ringing likely occurs. At the divergence points, a frequency-selective impedance matching circuit is inserted. The circuit consists of a resistor, a capacitor, and an inductor connected in parallel, which is also designed to activate only during state transitions with the dependency of their impedance on frequency. Thus, the side effects on CAN-FD operations can be prevented. The performance of the ringing suppression system is verified by experiments. The experimental results demonstrate that the proposed system reduces ringing to a level lower than the input threshold for recessive bit detection in diverse bus configurations and supports more reliable CAN-FD communication. [ABSTRACT FROM AUTHOR]