Adrian Posselt

Design and Evaluation of Frequency-Agile Multi-Standard Direct RF Digitizing Receivers for Automotive Use

This paper presents the design and evaluation of a ΣΔ-modulator based analog-to-digital converter (ADC) for direct RF digitization within a multi-standard vehicular connectivity architecture. Upcoming trends and changes which will require new architecture concepts for connectivity in the automotive domain are discussed. Hardware requirements are derived. Based on these goals, a reconfigurable ADC is designed with capabilities of digitizing all relevant wireless services for vehicular use within the frequency range of 600 MHz to 6GHz. A performance assessment is done based on evaluation of the signal to noise ratio within a realistic use case where multiple services at different frequencies are successfully digitized.

System Level Assessment of Vehicular MIMO Antennas in 4G LTE Live Networks

In this contribution, we present the results of a measurement campaign targeting at system level evaluation of vehicular multiple-input-multiple-out (MIMO) antennas. Our measurements are performed on a test track served by a Long Term Evolution (LTE) base station operating in the 800 MHz band. We show system level evaluation results obtained by using two reference monopole antennas and two automotive qualified, integrated prototype antenna systems. The presented results are gathered in line-of-sight (LOS) as well as non-LOS conditions. As vehicular antenna systems are limited by the available integration space, we analyze the specific impact of antenna decoupling on system level performance. System level performance metrics include parameters such as ergodic capacity and condition number of the MIMO channel matrix. We achieve antenna decoupling for the reference monopoles by increasing their separation. In case of the integrated antenna system we use a decoupling branch to decrease antenna coupling and correlation at the measurement frequency. We discuss a system level evaluation process for ranking antenna systems based on channel specific parameters. The applicability of the process for MIMO system performance evaluation is shown with a comparison of an integrated antenna system with the described reference antenna system.

System-level assessment of volumetric 3D vehicular MIMO antenna based on measurement

This paper presents the evaluation of a volumetric 3D multi-element antenna for vehicular connectivity based on a system-level approach. First, the antenna design to be used in Long Term Evolution (LTE) networks and its realization based on molded interconnect device (MID) technology are shown. During the antenna evaluation, system-level key performance indicators (KPI) like condition number and channel capacity are investigated and are compared to indicators like return loss, inter-element coupling and radiation characteristics. System-level KPI include effects due to vehicular antenna integration or channel conditions, which have an impact on the overall performance. A suitable 2D reference antenna arrangement is developed to evaluate the performance gain of the volumetric antenna design approach by performing test drives in a live LTE network.

Evaluation of a frequency agile direct RF ADC based on mixed-signal OFDM simulation

Rapid developments and emergence of diverse wireless systems call for radio frontends with agile and multistandard properties. Within this publication the performance of a direct RF digitizing ΣΔ-modulator based analog-to-digital converter (ADC) is evaluated based on orthogonal frequency division multiplex (OFDM) system simulation on the bitstream layer. The necessary transmit and receive building blocks are introduced as well as the previously developed reconfigurable ADC under test. The proposed approach allows flexible testing of different ADCs by analyzing the influence of the ADCs noise shaping on performance indicators like error vector magnitude (EVM) and symbol error rate (SER). The necessary steps for the combination of the OFDM signal generation and the system level simulation of the ΣΔ-modulator-ADC into a multi-domain simulation are introduced and discussed.

Evaluation and optimization of active signal canceling for coexistence management in vehicular multistandard transceivers

In this paper the suitability of active signal canceling architectures for interference reduction and coexistence management within multistandard transceivers for automotive use is evaluated. After description of the key concepts of reconfigurable vehicular connectivity architectures, we discuss active signal cancellation as an approach to suppress interference from transmitted signals. The realized architecture yields attenuations of up to 60 dB for sine signals and sufficient suppression for typical signals with a non-zero bandwidth. Based on the analysis the system is evaluated for a typical coexistence scenario in which a terrestrial Digital Video Broadcast (DVB-T) signal is successfully received within a multistandard transceiver, which transmits an interfering and potentially blocking adjacent signal at the same time.

Assessment of design methodologies for vehicular 802.11p antenna systems

In this contribution, we propose and analyze performance metrics for vehicular antenna systems. Considered metrics are the following: δD, RSS giving the difference in received signal strength (RSS) of the antennas, thus illustrating their supported diversity efficiency. The antenna gain outage rate ρG and the probability of antenna gain differences ρD. Further, the proposed performance metrics are evaluated for three prototypical vehicular antenna systems to assess their suitability for supporting IEEE 802.11p. The considered vehicular antenna prototypes employ different design methodologies to limit the interaction between their 802.11p and cellular antennas. By comparing the prototype systems based on mismatch, antenna isolation and metrics for the antenna radiation pattern, we assess their performance. We apply our benchmark results to measurements performed in a 802.11p testbed. Each prototype antenna system is evaluated according to the offered diversity efficiency, which we assess according to the RSS measured with both 802.11p antennas.