COVER STORY


AD2429W, AD2427W, AD2426W and AD2420W - comprise ADI’s latest family of pin-compatible, enhanced A2


B transceivers. The AD242x series supports daisy chaining of a single main plus up


to 10 sub-nodes over a total bus distance of 40m with up to 15m supported between individual nodes. A2


B’s main/sub-node line


topology is inherently efficient when compared to existing digital bus architectures. After a simple bus discovery process, zero additional processor intervention is required to manage normal bus operation. As an added benefit of A2


B’s unique architecture, system latency is


completely deterministic (a 2-bus cycle delay, which is less than 50µs) irrespective of the audio node’s position on the A2


B bus.


This feature is extremely important for speech and audio applications such as ANC/RNC and ICC, where audio samples from multiple remote sensors must be processed in a time-aligned fashion.


together with the digital MEMS microphone provide a well-suited solution for interconnecting and/or sharing multiple microphone signals demanded by audio, voice, noise cancelling and other acoustic applications that are rapidly expanding in vehicles. Consider an imaginary while exemplary case where a car application calls for a HF microphone module, an ANC microphone module, and a simple array microphone module consisting of two microphone elements for BF and all three modules are integrated around the overhead console area. Figures 3(a) and 3(b) show how such a design may be realised with the traditional analogue and the digital A2


B systems, respectively. Since the analogue system cannot easily accommodate


microphone sharing, each application block (HF, ANC and BF) requires dedicated microphone(s) and separate harnesses for connecting to the corresponding functional circuit(s). This leads to four separate microphone elements and three sets of harnesses (a total of seven wires plus shielding). In contrast, because sharing signals is easily supported by the digital A2


B system, the number of


Figure 3: A2 All A2


B transceiver feature comparison B transceivers deliver audio, control, clock and power over a


single, 2-wire, UTP cable, which significantly reduces overall system cost. System-level diagnostics are also an essential component of the A2


B technology. All A2 B nodes have the capability to identify a


variety of fault conditions including opens, wires shorted together, reversed wires, or wires shorted to power or ground. This capability is important from a system integrity standpoint because, in the case of opens, wire shorts, or reversed wire faults, A2


B nodes are still fully


functional upstream of the fault. The diagnostic capability also provides for the efficient isolation of system-level failures, which is critically important from the dealer/installer standpoint.


Applications of A2 B microphones and sensors


in the automotive industry From a single voice microphone to a multi-element BF mic-array for HF communication, from ANC to RNC, from ICC to siren sound detection, microphones have found more and more applications in the automotive industry. In accordance with the technology and market trend, almost every single new vehicle that hits the road today is equipped with at least one microphone module for HF communication. Premium and luxury cars may come with six or more microphone modules that are necessary for realising the full potential of BF, AEC, ANC, RNC, ICC, and so on, where digital MEMS microphones present clear advantages. The growing microphone count presents one significant challenge


to vehicle infotainment engineers – how to simplify the connecting harnesses and minimise their weight. This is not a trivial task for traditional analogue systems. At a minimum, an analogue microphone requires a pair of two shielded wires (ground and signal/power), pins and connector cavities for interconnection. The amount of wires is always twice the number of microphone modules in the system. Meanwhile, the total weight of the harness could increase even more rapidly depending on the wire length that is needed for connecting each microphone module. One simple thought to mitigate this problem is to reduce the number of microphones used in the system by sharing a microphone signal among multiple applications. For example, the same microphone signal could be used in HF communication and as an error signal in the ANC system. However, the shared microphone signal may need to be fed into different circuits for proper frequency filtering. In this case, one or multiple ground loops may form, which can cause significant noise issues. As a digital bus with daisy-chaining capability, the A2


B technology 14 OCTOBER 2021 | ELECTRONICS TODAY


microphone elements can be potentially reduced from four to two. In this specific example, a single microphone module consisting of two wide-bandwidth omnidirectional microphone elements can be used to provide two channels of acoustic signals that cover the needs of all application blocks. Once these two channels of signals reach the center processing unit (e.g., head unit or amplifier) through a simple UTP wire, they can then be shared and digitally processed to support applications of HF, ANC and BF. This example clearly demonstrates the benefits of the A2


B technology over the traditional


analogue approach. Indeed, many applications that are either new to the automotive


market or previously difficult to implement have been made possible by the commercialisation of the A2


B technology. For example


Harman International has developed a family of digital microphone and sensor modules that takes advantage of the A2


B bus system to


enable various automotive applications. Figure 4 shows some common automotive A2


can be used on a vehicle. These sensors include single A2


B accelerometers for RNC, externally B microphones and rooftop arrays for


B microphones and sensors and how they B


microphones and multi-element microphone arrays for ANC and voice communication, A2 mounted bumper A2


emergency siren detection and acoustic environment monitoring. Enabled by these A2


B microphones and accelerometers, more and


more application solutions requiring multiple sensor inputs are currently under development to further enhance the user experience. Vehicle architectures of the future will become increasingly more


dependent on high performance acoustic sensing technology such as microphones and accelerometers. A completely digital approach including sensor, interconnect, and processor provides significant performance and system cost benefits. Analog Devices and Harman International are partnering to deliver cost effective solutions that create value and differentiation for end customers.


Figure 4: Common automotive A2


Analog Devices www.analog.com


B microphones and sensors


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50