Antennae Systems Innovation Offers the Possibility of New Infotainment Architectures

Increasing networking of vehicle functions and off-board functionalities is causing a dilemma in terms of complexity. With its new system architecture, Hirschmann Car Communication wants to contribute to streamlining and efficiency gains. As an alternative concept to previous system architectures, the so-called smart antenna centrally processes the signals in the immediate vicinity of the antenna. This allows automotive manufacturers to integrate new, future standards in the field of radio, telephony or car-to-X services quickly without having to modify the head unit drastically – as the supplier explains. © Hirschmann Car Communication


DRIVERS OF NEW TECHNOLOGIES
In the early 2000s, to integrate their customers' mobile phones and MP3 players in the infotainment system, automotive manufactures were constantly having to create new interfaces. This was the first time that the constant pressure of the game of catch-up emerged -and this pressure is still felt today.
The rules of the game mean that the industry has to integrate fast-moving consumer electronic technologies in vehicles within a short space of time to appeal to what remains younger buyer groups. This also involves a huge increase in complexity as a result of driver assistance systems and car-to-X technologies. In vehicle electronics, this increases architecture and networking complexity, particularly where electronic control units (ECU) are used. The control units are distributed across different points in the vehicle -for example, the control unit is in the head unit (HU) for radio reception, in the centre console for telephone functions and is in the rear for TV services. This means that in a medium-sized car there are approximately 50 different control units and, in luxury vehicles that have a large number of assistance systems, 80 to 100 devices are not unusual.
Their central control element, from where the functions are coordinated, is the head unit. Enhancing a head unit is particularly risky because of the amount of complex functions highly integrated in a very small area. Even years of experience in hardware/software development cannot guarantee the capability to integrate new IT developments or customer requirements in the shortest possible time. This is why, today, these development projects still come up against schedules that cannot be met and discontinued functionalities.
However, beyond the head unit too, the level of electronics in vehicles is constantly growing and the entire electronic system architecture is becoming increasingly complex and complicated. Nevertheless, this must not lead to poor usability for customers. Passengers expect intuitive operating concepts, which make the numerous functionalities easy to control and allow additional smart devices to be integrated seamlessly. A constantly growing "flood of data" and an increasing number of antennae are the consequence of this -these constitute further drivers of complexity for the infotainment architecture.
One solution for this complexity-related dilemma is a new system architecture based on a modified partitioning of the control devices and their services in the vehicle, which aims to keep the in-car transmission channels as short as possible and bundle the radio services at a central point. Therefore, the main components of this architecture are the antennae and the signal processing that takes place immediately downstream. The transceiver, tuner and antenna are combined in one new unit. This creates several advantages in terms of reliability, transmission and reception quality and the optimisation of the installation space. Central processing of signals in the immediate vicinity of the antenna allows automotive manufacturers to integrate new, future standards in the field of radio, telephony or car-to-X services quickly without having to modify the head unit drastically. As a result automotive manufacturers can reduce their development costs when integrating new technologies and flexibly adjust them to customer requirements.

THE SMART ANTENNA AS A GATEWAY TO RADIO SERVICES
This is precisely what the new smart antenna from Hirschmann Car Communication offers. As an alternative concept to previous infotainment system architectures, it combines two functional groups: Transmission and receiver technology, i.e. the antenna and amplifier (where applicable) and subsequent electronic processing of the signals. This combination reduces complexity and materials costs at three points. Essentially, the smart antenna is based on a typical roof antenna in a shark fin

AU T H O R
Steffen Lang works in Product Management at the Hirschmann Car Communication GmbH in Neckartenzlingen (Germany). design. This has been enhanced with an electronic control device (ECU), which is located directly underneath the roof antenna. The control device directly processes the signals received from services such as AM/FM/DAB radio, mobile communication, GPS, Bluetooth or digital TV. This includes tuning, demodula-tion, decoding of data and managing lower level communication protocols.
With this structure, the smart antenna constitutes a new "unit" containing a tuner, transceiver and antenna, FIGURE 1. Firstly, this reduces the level of complexity when integrating various radio services. Mobile communication standards (GSM, UMTS, LTE) and navigation services (GPS, GLONASS, Galileo, BeiDou) are combined with radio (AM/FM, DAB, SiriusXM), keyless entry (Bluetooth LE) and car-to-X (802.11p) at one point and centrally processed. Now, all these radio services -for example, from a head unitcan be conveniently used in a standard- ised manner via one well-defined interface. Of course, not all the services mentioned above are always required in every vehicle. A small car equipped with only AM/FM radio and eCall, which will be compulsory throughout the European Union as of 2018, is quite conceivable. The design of the smart antenna was therefore based on scalability, to ensure that as many types of configuration as possible can be implemented using the same platform. The lead Figure of this article illustrates the maximum range of functions possible. Secondly, the smart antenna reduces the in-car distances covered by the analogue HF signals between the antenna and the receiver. The overall significantly reduced transmission channels benefit passengers when making telephone calls, listening to the radio, using the navigation function or watching television. Smaller losses along shorter cables and, if applicable, fewer HF connections ensure a better signal-to-noise ratio (S/N), which provides better reception overall.
The transmission frequencies of the various mobile communication standards, WLAN and Bluetooth are predominantly in the range of 1 GHz or higher. The in-car transmission of these signals along cables requires shielded cables to ensure that electromagnetic emissions from other control devices, for example, do not interfere with the useful signal. Use of a coaxial cable with an inner conductor for signal routing and an outer conductor that acts as a shield is the method of choice here. However the attenuation of coaxial cables increases significantly in the GHz range. Depending on the quality of the cable and the frequency of the signal, 1 to 2 dB per metre is expected. Even if you want to cover only short distances to a control device without amplification (approximately 2 m), the signal is attenuated by around 3 dB, FIGURE 2. This means that only 50 % of the signal will arrive at the control device. Attenuation losses at the connectors must also be taken into consideration. The installation space of a typical shark fin antenna can only accommodate small antennae that are a few centimetres in length and, therefore, receive only certain frequency ranges. This means that a shark fin antenna does ensure the reception of GNSS, telephone, Bluetooth and satellite radio. However, due to their size, the antennae for receiving terrestrial radio and television are placed at other points in the vehicle -depending on the installation space available. The radio antenna, for example, can often be found nearby on the rear window. The allocation of these antennae to the smart antenna ultimately results in the smart antenna system.
Thirdly, bundling the functions and directly processing the signals means that savings can be made with regard to cabling. This is due to the fact that fewer metres of coaxial cable are used in the car, or it is replaced with more cost-effective and loss-free Ethernet cable. Altogether, the number of cables and unnecessary interfaces in the car is reduced, which can reduce the installation time during production, FIGURE 3 and FIGURE 4. This system architecture corresponds to the current trend of reducing the immense complexity of head units and particularly adapting new technologies for head units, which accordingly involves a great deal of development work. The "transfer of services" from sections of the head unit to the smart antenna system also means that the head unit can operate independently of the radio standard. This ensures increased flexibility of the modular systems as the head unit is no longer affected by changes to standards or country-specific differ- ences. In addition, as soon as identical head units can be used, the total number of variations decreases for a range of different models. The connection between the smart antenna and the head unit -in other words the transfer of all data -can only be achieved using a high-performance digital bus system that supports both of the established standards, Most150 and Ethernet. The points mentioned provide greater flexibility when current infotainment and communication services are integrated. This applies in particular for the following three trends, each of which operate in the GHz range and should have as high a range as possible. The smart antenna architecture already correlates with these trends thanks to the placement of the antenna on the roof (ideal for range and transmission) and the direct signal processing (ideal for GHz signals).

TREND 1: WLAN ACCESS TO THE WIDER WORLD (2.4 AND 5 GHZ)
The expectations of customers regarding in-car software updates will con-tinue to increase and converge on the standards customarily used for smart phone updates. The times when only one garage could install new software will soon belong to the past. On possible scenario is that cars will be able to log in to the home network overnight and download relevant software packages or update the music library. In this case, a WLAN connection to the wider world is essential.

TREND 2: BLUETOOTH LOW ENERGY (2.4 GHZ)
In the medium term, radio remote control will be replaced by smart phones. In the future, it will be possible to open a car via a Bluetooth connection and a corresponding encryption function. This external Bluetooth interface should not be confused with the classic Bluetooth HFP for hands-free capability in the vehicle. There are a range of other functions possible. For instance, the new Mercedes E-Class already uses a Bluetooth connection between the vehicle and a smart phone for its Remote Parking Pilot. This app allows drivers to park their car without having to be inside the vehicle.
TREND 3: CAR-TO-X COMMUNICATION (5.9 GHZ) WLAN routers for home use based on the 802.11 radio standard family. The 802.11p standard has been specified for the direct communication between cars in terms of car-to-X communication and also with their environment. In the USA, legislators are debating a mandatory implementation of the standard, which significantly increases the likelihood of vehicles being equipped with 802.11p as standard. Furthermore, car-to-X communi cation provides important information, which enables autonomous driving. Range is a crucial characteristic for car-to-X in particular to ensure maximum safety for the driver. The optimal position of the smart antenna at the highest point on the vehicle is therefore an essential prerequisite.