Andreas Haderer

A 77-GHz FMCW front-end with FPGA and DSP support

Recent advances in the development of semiconductors allow the realization of low cost 77-GHz radar front-ends suitable for automotive applications. The requirements on the angular resolution often force designers to implement antenna arrays. In the last decade the trend moves towards digital array processing instead of analog beamforming because of the availability of cheap digital signal processors (DSP). In the case of an n-element receive array, the system must be capable of processing n receive channels in parallel resulting in a big amount of data. Field programmable gate arrays (FPGA) deliver the processing power and flexibility to handle the collected data and allow, in conjunction with a DSP, the implementation of sophisticated signal processing algorithms. This paper deals with the implementation of a 77-GHz frequency modulated continuous wave (FMCW) prototype radar system. The system is designed for use in array processing applications, with a maximum of eight parallel receive channels. The functionality of the prototype system is demonstrated in an imaging application. With the help of a portal axis the radar is moved along a synthetic aperture in order to reconstruct the reflectivity map of the imaging area.

A four channel 24-GHz FMCW radar sensor with two-dimensional target localization capabilities

The measurement of different target parameters using radar systems has been an active research area for the last decades. Particularly target angle measurement is a very demanding topic, because obtaining good measurement results often goes hand in hand with extensive hardware effort. Especially for sensors used in the mass market, e.g. in automotive applications like adaptive cruise control this may be prohibitive. Therefore we address target localization using a compact frequency-modulated continuous-wave (FMCW) radar sensor. The angular measurement results are improved compared to standard beamforming methods using an adaptive beamforming approach. This approach will be applied to the FMCW principle in a way that allows the use of well known methods for the determination of other target parameters like range or velocity. The applicability of the developed theory will be shown on different measurement scenarios using a 24-GHz prototype radar system.

Position estimation of thin, conducting plates at mm-Wave frequencies utilizing polarimetric effects

In this contribution, we address the position estimation of thin, conducting plates by means of a frequency-stepped continuous wave (FSCW) radar system. In particular, we focus on polarimetric scattering properties, introduced by an edge at the border of a conducting plate. To account for the edges contribution to the overall FSCW radar signal, the method of equivalent currents is applied and finally the implemented scattering model is verified by measurements. Based on the scattering properties, a simplified signal model is deduced by the method of stationary phase. The proposed signal model can be used to precisely estimate the position of the edge if multiple measurements from spatially distributed positions are available.

A Highly Modular 77-GHz FMCW Radar Sensor Prototype for Multi Target Tracking Applications

77-GHz radars are becoming more and more important for automotive applications. In this contribution a 77-GHz frequency modulated continuous wave (FMCW) radar prototype is presented. The prototype is based on highly modular building blocks for both, the hardware as well as the software. This modular design offers an incredible flexibility for testing different components. The resolvability of multi target scenarios by a Kalman tracking filter is supported by using ramp sequences where each chirp has a different ramp slope. Measurements with the FMCW radar sensor are carried out in an automotive environment.

A 77-GHz FMCW radar using a digital phase-locked synthesizer

A digital phase-locked synthesizer for application in a 77-GHz frequency modulated continuous wave (FMCW) radar is presented. It consists of a digital phase discriminator, a digital loop filter, highpass modulation, and predistortion of the VCO tuning characteristic. An additional feature is the ability to store the previous phase errors for iterative adaptation of the loop filter coefficients and the highpass modulation parameter. A radar system has been built to compare the proposed digital synthesizer to an offset-loop based one in actual radar measurements.

Simultaneous localization and data-interrogation using a 24-GHz modulated-reflector FMCW radar system

In this paper, the integration of a communication link for a modulated-reflector radar is presented. This kind of radar system is intended to determine the position of multiple semi-passive backscatter reflector nodes, designed to be mounted on different objects of interest. A method to transport information from these objects back to the radar-basestation is sketched, using the available hardware-resources of the nodes. In addition a technique minimizing the influence of this communication link on the localization capability of the system is presented and validated by measurements.

Experimental verification of a 77-GHz synthetic aperture radar system for automotive applications

We present measurement results collected with an experimental 77-GHz synthetic aperture radar, which is suitable for automotive applications. The presented approach relies on a simplified signal processing algorithm, which is derived by exploiting several approximations valid for typical automotive measurement settings. This leads to an image generation approach which requires only limited computational power. The presented results show that, despite the simplified approach, meaningful radar images can be generated. The experimental data was collected during various test drives without requiring highly precise position information.

In-chirp FSK communication between cooperative 77-GHz radar stations integrating variable power distribution between ranging and communication system

We present the realization of a cooperative radar system for ranging applications with integrated data-transmission capability. The simultaneous transmission is performed by the radar-hardware without the necessity of additional components or an auxiliary data-link. Therefore, the data are directly embedded in the transmitted chirp of a frequency-modulated continuous-wave radar sensor. A second station, acting as receiver, uses an identical, but unmodulated chirp for down-conversion. The resulting signal then is processed by a non-coherent demodulator setup, extracting the communication data. Measurement results from transmission of messages with different bit-rates are shown. By utilizing existing radar-hardware a transmission rate of up to 256 kbps is possible, without the need of a dedicated transceiver. Additionally, a method to optimize the ranging results by variable distribution of the available signal power between distance-measurement and communication system is presented.

GTD-based 2D scattering model for polarimetric position estimation of lap joints

Recent studies have shown that position estimation of metal plate edges by means of polarimetric effects is a promising technique in harsh industrial environments. Potential practical applications in industry include position estimation of two metal plates in a lap joint arrangement. However, applying the commonly used point target model to determine the position of a lap joint results in large estimation errors caused by model inaccuracies. We propose a new two-dimensional model of a perfectly electrically conducting lap joint building upon the geometrical theory of diffraction (GTD). For verification, we present a comparison of the estimation results using a computationally intensive method-of-moment-based model as reference.

Polarimetric measurements with integrated sensors at mm-wave frequencies

We present a fully polarimetric frequency-modulated continuous-wave (FMCW) radar prototype and show its performance by polarimetric measurements of a dihedral corner reflector. The radar prototype operates at a frequency of 77 GHz and is built up by an FMCW frontend (FE) and a multichannel baseband board. The FE consists of horizontally and vertically polarized transceiver channels to conduct co-polarized and cross-polarized measurements. To demonstrate the capability of the system, we placed a dihedral corner reflector on a turntable facing the radar system. Then measurements of the corners scattering parameter, depending on its rotation angle, were taken. To confirm the measurement results, we ran simulations using a self-developed numerical field simulation tool and compared the results to the measurements.