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<p>Using the Commstack driver from DECOMSYS can further reduce software complexity. This driver allows the designer to use high-level function calls to set up the FlexRay registers rather than being concerned about low level registers.</p>

The handset WiMAX transmitter in this example operates in the 2.5-2.7GHz band. The output power of the WiMAX Power Amplifier (PA) may be as high as +25dBm. The WiMAX and Bluetooth transmit antennas are in close proximity to each other, with the user's hand, or the surface on which the handset is placed, typically causing 10dB path-loss between them. This yields a +15dBm signal at the Bluetooth Band Pass Filter (BPF) input. The BPF must pass frequencies of up to 2.48GHz (the highest Bluetooth hopping frequency), hence it is unable to reject more than 3dB of the undesired WiMAX signal and so passes at least +12dBm of interference signal to the Bluetooth Low Noise Amplifier (LNA).

This article is part of a three part series that examines networking structures in the automobile. Part 1 discusses how consumer technologies, such as USB and Ethernet, are integrated into the vehicle and connected with the vehicle backbone, using a technology called Media Oriented Systems Transport (MOST®). Part 2 describes why a network is needed for the vehicle backbone, why MOST was developed, and what its advantages are over other networking choices. This series conclusion offers a detailed explanation of MOST and examines the new Intelligent Network Interface Controller (INIC) architecture that simplifies how MOST systems are integrated.

The Media Oriented Systems Transport (MOST) architecture provides the physical interconnection and the software layers to ensure that automotive electronics devices interoperate. The International Standards Organization (ISO) has developed a model called the Open Systems Interconnect (OSI) Reference Model for creating the MOST architecture. The model defines seven layers of interoperability where each layer in one device communicates with the corresponding layer in another device. The figure below shows the various layers and the corresponding MOST concepts.

CMF5095K300FKEK_Vishay Dale_Through Hole Resistors

In MOST, NetServices is the software component that implements the Application Programming Interfaces (APIs) needed to establish communication between devices. In the first MOST implementations, NetServices was managed by an External Host Controller (EHC). The EHC had to ensure that all real-time requirements of the communication link were met. It typically ran whatever application was implemented on a device (e.g. user interface, amplifier, AM/FM tuner, CD changer, etc.) along with the network management tasks. The EHC was connected to a Network Interface Controller (NIC) that then connected to the physical link, which was typically Plastic Optical Fiber (POF).

The new INIC (Intelligent NIC) generation of MOST not only reduces software overhead, but it allows the use of Unshielded Twisted Pair (UTP) wiring. UTP copper wiring is an attractive solution to some carmakers because they want to continue using their existing manufacturing processes for wire harnesses and don't want to introduce new technologies like optical fiber.

CMF5095K300FKEK_Vishay Dale_Through Hole Resistors

There are now tens of millions of devices on the road using the NIC architecture. When implementing it, the network is dependent on each EHC controller to properly implement network management functions. Thus each EHC has to respond within the very specific timeframes to ensure proper network operations, which makes the real-time nature of these low level functions taxing on the EHC.

With the new INIC architecture, some of the burden is taken off the EHC by bringing the real-time functions needed for the MOST network into the INIC IC. The figure below shows the migration from the NIC to the INIC architecture.

CMF5095K300FKEK_Vishay Dale_Through Hole Resistors

This new INIC architecture results in the network becoming its own entity even though it is distributed among various devices connected to it. The individual INIC chips connect with each other and start the network without any intervention from an EHC. The network then exists as a standalone unit and does not rely on functions running on the various devices connected to it.

As seen from the waveform in Figure 3 , the current in each phase is discontinuous for a large portion of the time, even though the voltage is substantially above zero volts (see voltage waveforms of Figure 1). By definition, a PFC circuit is required to make the input current to the PFC look like it is going into a resistor connected between line and neutral. So the current waveforms should be the same as the voltage in Figure 1, with scaling to allow for the power consumption.

The needed solution is one that will provide the PFC function for each of the lines and, at the same time, make certain that the load on each of the lines is balanced. This requires three main building blocks plus some ancillary circuits.

The first circuit that each of the lines will see coming into the system is the PFC converter section which consists of three separate PFC converters isolated from each other. The design of these should allow for about 50 percent more power instantaneously, but about 15 percent more power thermally. The design of the PFC section is described in Reference 1 .

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Dual-mode devices will undoubtedly attract a lot of interest because they will be capable of operating in either standard Bluetooth mode or ULP mode. Interestingly, however, the power consumption of a dual mode chip is expected to be about 80% of that of standard Bluetooth.

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