Verification of Gigabit Ethernet-based Bus Systems in Vehicles

Verification of Gigabit Ethernet-based Bus Systems in Vehicles

In this article, the complete analog front-end (AFE) of the high-speed Ethernet transmission systems (100BASE-T1 and 1000BASE-T1) are characterized. These bus systems consist of transceiver chip, low pass filter (LPF), common mode choke (CMC), DC block capacitor, common mode termination (CMT) and the transmission channel (unshielded- or shielded twisted pair, UTP/STP). The high-frequency models of the mentioned components are essential for design and simulation of high-speed bus systems. For this purpose, new simulation models are proposed in this article. In order to measure the appropriate CMC for 100BASE-T1 FR4 substrate was used as test-fixture. Due to the frequency range of 1000BASE-T1, high-frequency substrate, i.e. RO4350B was selected. The common-mode (CM) and differential-mode (DM) impedance of the choke are measured. Furthermore, to describe the general characteristics of the choke, the measurements of mixed mode S-parameters are made. The LPFs are fabricated using mentioned substrates. The filter attenuation is measuredconsidering the signal frequency. In the next step, the impedance and mixed-mode S parameters of CMC and LPF were simulated using the suggested equivalent circuit models. The agreement between measurement and simulation results confirmed the validity of the proposed models. On this basis, the suggested models could be adapted and used for further research in the field of Multi-Gig data transmission. As the last step, a comparison between UTP and STP cable based on laboratory-level measurements is performed in two steps. First, the mixed-mode S-parameters of the mentioned cables are determined. Bus Pass System Second, the shielding attenuation is examined according to the wire injection method. From the author’s’ point of view, this paper is the first detailed investigation of the analog front-end of the automotive Ethernet communication system.

In the last sections, individual components of the Front-End circuit were examined in detail. The equivalent circuit has been developed and simulated. A comparison between the simulation results and the results of the measurements showed good agreement.

As already described, the data transmission for 100 Mbit/s is establishedvia UTP lines. By means of the characterization of the transmission channel, methods such as forward error correction and equalization can be implemented at the chip level [8]. In the next generation of Ethernet communication, the goal is to increase data rates to 1 Gbit/s. With increasingfrequencies, the data lines become more susceptible to interference [9]. Therefore, the use of UTP lines for Gigabit communication is doubted and alternative transmission media such as STP, shielded parallel pair (SPP) or coaxial lines are examined for their suitability. These cables have better noise immunity and noise emission than UTP cables. In this section, a comparison between a UTP and an STP cable based on laboratory-level measurements is performed in two steps. First, the mixed-mode S-parameters of the STP and UTP line with a length of 6m are determined with the test set-up described in [10] and shown in Fig. 17(a). https://codeshoppy.com/ . In the second step, the shielding attenuation is examined according to the “wire injection” method for three different lines under the same measuring conditions.

The following results are obtained by comparing the measurements: • The measured coupling between STP and UTP lines of equal length is less than -65 dB. • The coupling between an STP line and an RG58 cable is less than -50 dB. • The coupling of two STP lines has a value of less than -90 dB. These measurements show the effectiveness of the twisting and especially the shielding of the tested lines.

The bandwidth requirements of future automotive network technologies pose new challenges to vehicle manufacturers worldwide. The increase in the data rate is to be realized by increasing the baud rate. The existing standards for 100 Mbit/sand 1000 Mbit/s each use PAM-3. The use of modulation formats such as PAM-5 to PAM-16 is planned. However, higher modulation formats increase sensitivity to electrical interferences. Therefore, the investigation of the robustness of the latest Ethernet bus systems and their components regarding electromagnetic compatibility plays an important role. In this article, the existing standards for mentioned data in automotive, i.e. 100BASE-T1 and 1000BASE-T1 are described and investigated. The requirements of the physical layer and the transmission channel are discussed. To design and simulate the Ethernet bus systems the models of their analog front-end are required. The model of the transceiver, low pass filter, common mode choke and common mode termination are presented. The proposed models are simulated using SPICE equivalent circuits and verified by measurements. The CM and DM impedance of the choke are measured. Furthermore, the measurements of mixed mode S-parameters of CMC and LPF are made. As the last step, the UTP and STP cables were compared by measurements of shielding attenuation and mixed-mode S-parameters. Download Now