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A tremendous number of landmines has been buried during the last decade. In recent years, various autonomous platforms equipped with ground-penetrating radars (GPRs) have been proposed for the detection of landmines. These systems have already demonstrated their performance in controlled environments with known ground truth. However, it has been observed that the influence of surface conditions in the form of vegetation and roughness as well as soil moisture content significantly reduce the detection probability. The influence of these individual factors on a ground-offset GPR is presented and discussed in this work. Each of these factors significantly degrades the backscattered signal. With increasing soil moisture, the signal gets attenuated more strongly; however, the signature is maintained in the phase of the C-Scans. An increase in surface roughness deteriorates the target pattern making it difficult to detect buried objects unambiguously. Vegetation, especially with irregular leaf structures, can appear as a ghost target and scatter the electromagnetic waves. In most cases, the target is easier to detect in the phase of the B- or C-Scan. [ABSTRACT FROM AUTHOR]

This paper presents a new frequency-modulated continuous-wave front-end module intended to serve next-generation automotive radar sensors. Providing one transmit and eight receive channels, the module is designed to operate between a multibeam antenna and an advanced signal-processing unit. All receive channels are equipped with low-noise amplifiers, mixers for downconversion, and IF amplifiers. Cascaded buffer amplifiers for the local-oscillator signal enable parallel operation of all receive channels. A high-performance synthesizer provides generation and transmission of arbitrarily programmable frequency ramped waveforms with high stability and linearity. Slope and frequency deviation of the waveforms can be adjusted for the respective radar application. Short settling times of the synthesizer allow very fast slopes and, thus, short distance measurements. An overview of the overall front-end module design and realization approach is given, including a more detailed description of the synthesizer concept. All active millimeter-wave functions are realized with GaAs monolithic microwave integrated circuits assembled in a hermetically sealed multichip module (MCM). The MCM itself is incorporated into a three-layer printed-circuit-board stack onto which IF amplification, frequency control, waveform generation as well as dc and bias control is realized. A summary of the measured performance data obtained from correspondingly built-up prototypes is given. [ABSTRACT FROM AUTHOR]

On-chip antennas are frequently used as radiating elements for monolithic microwave integrated circuits (MMICs) operating above 100 GHz. Their radiation pattern is wide since the radiator extension is typically about half wavelength. In a package, the wide radiation pattern is easily disturbed by interference from parasitic radiation of the package. In this paper, an approach to minimize and adjust the interference of the package is proposed and applied to a quad flat no leads (QFN) package housing. A structured metal sheet positioned between chip and exposed pad is used to generate enough degrees of freedom for the optimization of the 3-D-radiation pattern in open-cavity and molded QFN packages. For the open-cavity QFN package, a U-shaped slot is introduced, which reduces the propagation of surface waves to the sides and creates a uniform radiation pattern. For the molded QFN package with opening around the on-chip antenna, a corrugated metal sheet is introduced. This leads to a robust packaged radar MMIC with an on-chip antenna at 160 GHz, which provides a directed radiation pattern to boresight. Both optimized radiation patterns are well suited for the illumination of dielectric lenses, which results in a higher lens gain and a lower sidelobe level of the lens pattern compared to the standard QFN packaging. The proposed concepts are verified by measurements for the open-cavity and molded QFN packages at 160 GHz. [ABSTRACT FROM AUTHOR]

The increasing number of radar sensors in commercial and industrial products leads to a growing demand for system functionality tests. Conventional test procedures require expensive anechoic chambers to provide a defined test environment for radar sensors. In this paper, a compact and low cost dielectric waveguide radar target generator for level probing radars is presented. The radar target generator principle is based on a long dielectric waveguide as a one-target scenery. By manipulating the field distribution of the waveguide, a specific reflection of a radar target is generated. Two realistic scenarios for a tank level probing radar are investigated and suitable targets are designed with full wave simulations. Target distances from 13 cm to at least 9 m are realized with an extruded dielectric waveguide with dielectric losses of 2 dB/m at 160 GHz. Low loss (0.5 dB) and low reflection holders are used to fix the waveguide. Due to the dispersion of the dielectric waveguide, a detailed analysis of its impact on frequency-modulated continuous wave (FMCW) radars is given and compared to free-space propagation. The functionality of the radar target generator is verified with a 160-GHz FMCW radar prototype. [ABSTRACT FROM AUTHOR]

A number of millimeter-wave (mm-wave) integrated radar sensors above 100 GHz were proposed in the past five years. The comparability between these radar systems is limited due to different semiconductor processes, synthesizer topologies, and external periphery. Especially, the issue of using a monostatic or bistatic radar monolithic microwave integrated circuit (MMIC) for single-chip sensors is not discussed in detail. This paper provides a comparison between the different properties of bistatic and monostatic MMICs based on two realized almost identical silicon germanium (SiGe)-MMICs at 154 GHz. In the monostatic case, the influence of the transmit–receive coupler on the performance of the system is explained. In the bistatic case, the illumination of a focusing lens and the leakage from transmitter to receiver are investigated. All properties are verified by measurements. The system performance of the monostatic and bistatic MMIC are compared by the calculated link and noise budget. The detection performance and the signal-to-noise ratio performance are evaluated in two radar measurements. Limitations and suggestions for improvement are given for monostatic and bistatic mm-wave frequency-modulated continuous-wave radar MMICs. [ABSTRACT FROM AUTHOR]

The dynamic range of frequency modulated continuous wave (FMCW) radar sensors is often limited by the phase noise of the ramp signal. Especially at millimeter wave (mm-wave) frequencies, a low phase noise signal is very difficult to obtain. In this paper, a new system architecture, which is implemented in a low-cost, ultracompact FMCW radar monolithic microwave integrated circuit (MMIC) at 160 GHz, is proposed to address this topic. The approach is based on a frequency offset synthesizer, whose upconverting mixer is driven by a stabilized low phase noise local oscillator (LO) signal. This LO is generated by a fixed-frequency phase locked loop with a 2^N divider. The upconversion of the ramp signal with the stabilized LO signal leads to an excellent mm-wave phase noise of −89 dBc/Hz at a frequency offset of 1 MHz. By integrating the antennas on the MMIC, interconnects at mm-wave frequencies to package or printed circuit board are avoided and a simple assembly and interconnection technology is feasible. The ultracompact MMIC is realized on an area of only 2 mm2, including the integrated antennas. A precision below 5 \mu \textm for range measurements is demonstrated with the radar sensor. Additionally, the radar performance is evaluated with two different voltage-controlled oscillators for the generation of the ramp signal. [ABSTRACT FROM AUTHOR]