Environmental issues and the global need to extend sustainable access to electricity have fostered a huge amount of research in distributed generation by renewables. The challenges posed by the widespread deployment of distributed generation by renewables, such as intermittent power generation, low inertia, the need for energy storage, etc., call for the development of smart grids serving specific local areas or buildings, referred to as microgrids and nanogrids, respectively. This has led in the last decades to the proposal and actual implementation of a wide variety of system architectures and solutions, and along with that the issue of the power converters needed for interfacing the AC grid with DC micro- or nanogrids, and for DC regulation within the latter. This work offers an overview of the state of the art of research and application of nanogrid architectures, control strategies, and power converter topologies.

Advanced automotive applications like Active Noise Cancellation (ANC) and Individual Listening Zones (ILZ) require a high number of transducers (i.e., microphones, accelerometers, and loudspeakers) usually employed as arrays. Also outside the automotive field, transducer arrays are widely employed in several applications as teleconferencing systems, industrial and civil noise and vibration monitoring. Automotive Audio Bus (A 2 B) is an audio transport protocol that solves the latest requirements of the automotive and industrial field. A 2 B allows transporting up to 32 channels in a multi-node daisy chain network and guarantees synchronization and low deterministic latency. This paper aims to develop a clock propagation model of an A 2 B network composed by transducer arrays. This model will be useful to evaluate the impact of the bus on the array performances. Firstly, a theoretical description of the A 2 B protocol and jitter analysis is provided. Then jitter measures were carried out on the clocks distributed along the A 2 B network. Lastly, latency introduced by nodes of the network is investigated.

Despite the increasing demand for multichannel audio systems, existing solutions are still mainly analog or audio-over-IP based, leading to well-known limitations: bulky wiring, high latency (0.5-2 ms), and expensive devices for protocol stack management. This paper presents a costeffective, low latency, full-digital solution that overcomes all the previously mentioned problems. The proposed architecture is based on the new Automotive Audio Bus (A 2 B) protocol. It guarantees deterministic latency of 2 samples, 32 downstream/upstream channels over a single Unshielded Twisted Pair (UTP) cable and phase-aligned signals. A single A 2 B chip is required for each node, reducing dramatically the system cost. The developed architecture is composed by a main board and an A 2 B network. The main board handles up to 64 channels, and it converts standard protocols usually employed for audio signal delivery, such as AES10, AVB and AES67, into A 2 B streams and vice versa. The A 2 B network can include a series of devices, for instance power amplifiers, codecs, DSPs, and transducers. There are many application examples including, but not limited to, transducer arrays (e.g., microphone, loudspeaker, accelerometer arrays), audio distribution in meeting rooms, Wave Field Synthesis (WFS), Ambisonics immersive audio systems and Active Noise Control (ANC). A modular and portable WFS system was developed employing the above-described architecture. It is based on eight channels soundbars, which can be daisy-chained in reconfigurable geometries and featuring up to 192 channels.

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Microphone arrays of various sizes and shapes are currently employed in consumer electronics devices such as speakerphones, smart TVs, smartphones, and headphones. In this paper, a full-digital, planar microphone array is presented. It makes use of digital Micro Electro-Mechanical Systems (MEMS) microphones, connected through the Automotive Audio Bus (A 2 B). A clock propagation model for A 2 B networks, developed in a previous work, was employed to estimate the effects of jitter and delay on microphone arrays. It will be shown that A 2 B allows for a robust data transmission, while ensuring deterministic latency and channels synchronization, thus overcoming the signal integrity issues which usually affect MEMS capsules. The microphone positioning is also discussed since it greatly affects the spatial accuracy of beamforming. Numerical simulations were performed on four regular geometries to identify the optimal layout in terms of number of capsules and beamforming directivity. An A 2 B planar array with equilateral triangle geometry and four microphones, three in the vertices and one in the center, was built. Experimental measurements were performed, obtaining an excellent matching with numerical simulations. Finally, the concept of an array of arrays (meta-array) is presented, designed by combining several triangular units and analyzed through numerical simulations.Index Terms-Automotive Audio Bus (A 2 B), automotive applications, beamforming, consumer products, digital MEMS microphones, meta-arrays, microphone arrays, planar arrays, spatial audio, triangular arrays.