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A new cooperative transponder system for traffic safety applications is presented. The prototype system uses three different channels in a frequency range of 5.773 to 5.925 GHz to detect and localize vulnerable road users, infrastructure and other cars equipped with transponders in order to improve traffic safety, even under non-line of sight conditions. Two 10 MHz channels are used for ad-hoc network management, communication and angle of arrival estimation, while one 54 MHz channel is used for round-trip time of flight measurements, combining precise relative localization with data communication between equipped cars and multiple road users or infrastructure transponders. In the current implementation, data communication is carried out by an orthogonal frequency division multiplex link, while the distance measurement utilizes the idea of a secondary radar with pulse compression, using amplitude modulated pseudo noise codes and time division multiple access for multiuser support. This paper describes the system setup as well as an implementation of the prototype hardware and shows the current performance of the system in laboratory and real world measurements.

The basic foundation to enable safety-of-life applications in vehicular environments is the precise localization and path prediction of other road users in range. Currently available technologies like radar, camera or global positioning systems cannot meet most of the stringent requirements in terms of accuracy, reliability, update rate, and low outage probability imposed by this kind of applications. Radio based ranging methods using active transponders have already demonstrated their appealing capabilities like a low probability of outage and a very high range accuracy, even in multipath and non-line of sight conditions in urban areas. In order to allow full integration of such a system into IEEE 802.11p transceiver hardware and compatibility with existing Vehicle-to-Vehicle/Infrastructure applications, a method for range estimation based on orthogonal frequency modulated data symbols is described in this paper and a computationally simple implementation is presented.

A 10kHz bandwidth 50Amax current sensor using a Hall effect gradiometer without magnetic core provides 80kHz update rate with a digital interface. Very low un-calibrated offset of 30mA (1σ) and after calibration typical 10mA over temperature is accomplished by a chopped multi-bit feedback continuous-time 3rd order ΔΣ-ADC. This also realizes low noise of 13mA rms in 1kHz signal bandwidth. The ADC uses enhanced chopping techniques and additional digital feedback loops to avoid chopper ripple. New analog and digital stress-compensation circuits with lateral and vertical n-doped resistors achieve lifetime gain drifts below 1% and temperature compensation. Auto-zeroing ping-pong comparators offer a fast over-current detection of 1…2μs on a dedicated output pin. The monolithic integrated sensor chip and the 4kV galvanic isolated current rail fit into a very small 7×7×1mm3 package.

Tire pressure monitoring systems (TPMS) are gaining importance due to improved security standards in the automotive industry. In active systems, the power consumption of the system is of utmost importance for a required lifetime of more than 10 years. The presented integrated circuit comprises high resolution pressure, temperature and voltage monitoring, low-power oscillators, a specialized DSP with RAM/ROM and an EEPROM to store calibration data. The continuously running low-power oscillator for internal wake-up timing is operated with 30 nA. Due to the extremely low-power consumption of all circuit blocks, pressure measurements can be carried out in short intervals (0.5 s). This enables the implementation of a new intelligent dynamic wake-up algorithm to optimize the power-intensive HF-transmission intervals under different driving situations. Thus additional rotation detectors are not needed any more. The charge consumption without HF-transmission results in 48 mAh in 10 years.

An integrated GMR (giant-magnetic-resistance) sensor is presented for 360deg angular measurements of rotating magnetic fields in automotive applications. The spin-valve GMR-layers are directly applied to a standard semiconductor 0.22 mum CMOS process by vertical integration of the sensor-bridges atop of active circuitry. The entire integrated angle-sensor comprises 2 orthogonal magnetized GMR-bridges for sine and cosine signal measurements, and the subsequent signal conditioning circuitry. The entire angular sensor is designed to work in harsh automotive environment in a temperature range of -40degC to 150degC. The strength for best precision covers a wide range from 20 to 50 mT. The resulting angular information itself can be obtained by SPI-readout and calculating the arc-trigonometric function of the bridge signals with a resolution of >13 bit in an auxiliary microcontroller. After individual calibration to compensate for production spread an accuracy of typical 0.5deg is achieved.

A linear 4kHz Hall sensor in 0.6mum BiCMOS has digital 3rd-order temperature compensation, a DR of 90dB and an offset of 50muT. It uses a chopped 3rd-order multibit CT-DeltaSigma ADC including an up/down counter loop and bandgap-based compensation for stability and accuracy. Digital compensation of sensitivity drift caused by package-induced stress is provided