This paper describes a novel frequency-modulated continuous-wave radar concept, where methods like nonuniform sparse antenna arrays and multiple-input multiple-output techniques are used to improve the angular resolution of the proposed system. To demonstrate the practical feasibility using standard production techniques, a prototype sensor using a novel four-channel single-chip radar transceiver in combination with differential patch antenna arrays was realized on off-the-shelf RF substrate. Furthermore, to demonstrate its practical applicability, the assembled system was tested in real world measurement scenarios in conjunction with the presented efficient signal processing algorithms.

The beam pattern of an antenna array is one of the most important characteristics of classical phased arrays and of more modern smart antenna, digital beamforming and multiple-input multiple-output array systems. Most approaches to designing such systems are based on an ideal mathematical model, which leads to an ideal beam pattern. However calibration errors and mutual coupling are real-world effects that often deteriorate the beam pattern and thus the array performance. In this paper we present worst-case boundaries and a statistical analysis of the beam pattern deviation for linear, angle-independent calibration error and mutual coupling models. We provide general results as well as specialized results for calibration errors and coupling between adjacent channels of linear arrays. The results provide an understanding of the influence of different array design parameters. They are also meant as tools for specifying tolerance and channel coupling requirements as well as for the analysis of the probabilities to achieve a beam pattern within certain boundaries.

In this paper, a prototype automotive radar sensor is presented that is capable of generating simultaneously multiple transmit (TX) beams. The system is based on a four-channel 77-GHz frequency-modulated continuous-wave (FMCW) radar system. The number of beams, their radiated power, steering angle, and beam pattern can be changed adaptively. This is achieved by the utilization of orthogonal waveforms applied to different beams in combination with digital beamforming on the receive side. Key components are vector modulators in the TX path controlled by digital-to-analog converters. The performance of the system is shown in measurements focused on beam pattern, signal-to-noise ratio, and susceptibility in case of interfering targets at cross-range. Measurement results are discussed and compared to theory and simulations. Furthermore, crest factor minimization of the vector modulator's control signals is introduced and used to increase the achievable TX power, which will be also shown in measurements.

In this paper we present methods for the design of planar frequency-modulated continuous-wave (FMCW) multiple-input multiple-output (MIMO) arrays with an emphasis on the problem of moving targets in time-division multiple-access (TDMA) systems. We discuss the influence of target motion and boundaries of operation and present a method to compensate for its effects, which requires special attention in the array design and in signal processing. Array design techniques, examples including an implementation, and measurement results are also covered in this article.

This paper describes a fully-integrated 77-GHz ultra-wideband pseudo-random noise (PRN) radar transceiver in a Silicon-Germanium technology. The transceiver is equipped with a programmable pseudo-random binary sequence (PRBS) generator, which is realized in a current-mode logic topology and can be operated with a clock rate of up to 4.25 GHz to enable a range resolution of 3.5 cm. The signal generation unit is simplified by including a frequency multiplier to create a 76.5-GHz carrier signal from a single 4.25-GHz input, that is also used as a clock for the PRBS generator. The transceiver achieves a phase noise of -105.3 dBc/Hz at 1-MHz offset frequency, a transmit output power of 6.2 dBm, a receive gain of 24 dB and an input-referred 1-dB compression point of -14 dBm. Track&hold circuits included in the receive path allow the use of a sub-sampling technique to reduce the IF data rate down to 1 MHz. Radar measurements with two PRN transceivers with different primitive polynomials were done concurrently to show a fundamental function of the programmable PRBS generator. Radar measurements with the PRN and the frequency-modulated continuous-wave (FMCW) principles show comparable results and the PRN radar proves to be a real alternative to the FMCW radar.

In this paper, we present a radar sensor system for real-time blast furnace burden surface imaging inside a fully operative blast furnace, called BLASTDAR, the blast furnace radar. The designed frequency-modulated continuous-wave (FMCW) radar sensor array operates in the frequency band around 77 GHz and consists of several nonuniformly spaced receive and transmit antennas, making it a multiple-input multiple-output radar system with large aperture. Mechanical steering is replaced by digital array processing techniques. Off-the-shelf automotive-qualified multichannel monolithic microwave integrated circuits are used. By means of this configuration, a virtual antenna array with 256 elements was developed that guarantees the desired angular resolution of better than 3°, and a range resolution of about 15 cm. Based on the single-channel FMCW signal model, this paper will derive a multichannel signal model in combination with a digital beamforming approach and further advanced signal processing algorithms. The implementation of a simulation tool covering the whole design process is shown. Based on these simulation results, a system configuration is chosen and the obtained setup is defined and presented. A description of the manufactured cost-efficient radio frequency and baseband boards together with the housing design shows the practical implementation of the sensor. For the system calibration, two different methods are listed and compared regarding their performance. Verification measurements confirm the predicted performance of the developed sensor. Several measurements inside a fully operational blast furnace demonstrate the proper long-term functionality of the system, to the best of our knowledge, for the first time worldwide. It is in continuous operation since about two years in blast furnace #5 of voestalpine Stahl GmbH, Linz.