This paper proposes a backprojection approach for detecting people with two non-coherent radars mounted underneath a UAV. The reconstruction of a limited area above the ground using backprojection allows the effortless combination of the data from both radars and the detection of a person despite the UAV’s ego-motion as well as the strong reflection from the ground. The measured results show that the respiration rate of a detected person can be estimated with a relative error of less than 2.5 %.

The article presents a monostatic $D$ -band frequency-modulated continuous-wave (FMCW) radar based on a fully integrated monostatic single-channel silicon-germanium (SiGe) transceiver (TRX) chip. The chip is fabricated in Infineon’s bipolar-complementary metal–oxide–semiconductor (BiCMOS) production technology B11HFC which offers heterojunction bipolar transistors (HBTs) with an $f_{\mathrm {T}}/f_{\mathrm {max}}$ of 250 GHz/370 GHz. The monolithic microwave integrated circuits (MMICs) output signal is coupled by a fully differential substrate integrated waveguide (SIW) based coupling network. The output power at the WR-6.5 antenna flange is more than −10 dBm over a bandwidth of 37.5 GHz. For a sweep within a single-loop phase-locked loop (PLL) circuit from 174.5 to 121.5 GHz, a spatial resolution of almost 3 mm with a metallic plate as the target is achieved. The radar provides a small form factor of $2 \times 4 \times 5$ cm 3 and low power consumption of 2.2 W at 5 V. Finally, the capabilities of the sensor for non-destructive testing (NDT) are demonstrated using a millimeter scanner. With radar imaging, it was possible to measure the orientation of the fiber layers up to a depth of 7.03 mm.

This article presents a frequency-modulated continuous wave (FMCW) harmonic radar in the 61-/122-GHz industrial, scientific, and medical (ISM) frequency bands. The radar is based on two self-designed monolithic microwave wave integrated circuits (MMICs) for the transceiver (TRX) and tag which are fabricated in a 130-nm SiGe BiCMOS technology. The presented TRX-MMIC consists of a fundamental voltage-controlled oscillator (VCO), a power amplifier (PA), Wilkinson power dividers, and a static divide-by-16 chain for stabilization within a phase-locked loop (PLL) in the transmitter (TX) part. The receiver (RX) part has two channels with a low noise amplifier (LNA), a Gilbert cell mixer, and an intermediate frequency (IF)-amplifier each. The fundamental of the VCO is converted by a frequency doubler and distributed to the local oscillator (LO) input of the RX-mixers. With such a TRX architecture the active nonlinear tag which consists of antennas, pre-amplifiers, and a frequency doubler can be detected. For a sweep from 60 to 64 GHz, a spatial resolution of 4 cm at 1-m distance and a range of 23.3 m is achieved. With these characteristics, the tag enables harmonic radar applications in the millimeter-wave (mm-wave) range for medium range with high accuracy and resolution with a small form factor.

The paper presents a monostatic D-Band FMCW radar based on a fully integrated mono-static single-channel SiGe transceiver chip. The chip is fabricated in Infineon's BiCMOS production technology B11HFC which offers HBTs with an $f$T/ $f$max of 250/370 GHz. The MMIC's output signal is coupled by a fully-differential SIW based coupling network with a bandwidth of more than 70 GHz. The output power at the WR-6.5 antenna flange is more than −10 dBm over a bandwidth of 37.5 GHz. For a sweep within a single-loop PLL circuit from 174.5 GHz to 121.5 GHz with a ramp duration of 6 ms, a spatial resolution of 4.6 mm with a metallic plate as the target at a distance of 0.6 m is achieved. The in-loop phase noise at 10 kHz offset is better than −70 dBc/Hz in this frequency range. The radar provides a small form factor of 2×4×5 cm3and low power consumption of 2.2 W at 5 V at a USB supply.

In this paper a fully integrated monostatic single-channel SiGe transceiver chip is presented for applications in the whole E-Band. The architecture consists of a fundamental E-Band VCO, a direct down-conversion mixer, a static divider chain, and coupling/matching networks at the output for a good chip-to-PCB interface via bond wires. The chip is fabricated in Infineon's BiCMOS production technology B11HFC which offers HBTs with an f T of 250GHz and f max of 370GHz. The peak output power of the chip is -1 dBm while the receive mixer offers a -0.2 dBm input referred compression point to keep it from being saturated. The chip has a power consumption of 254mW and uses an area of 1.35mm2, A complete FMCW radar system prototype is also presented with a power consumption below 2.1 W and an effective chirp bandwidth of 31.1 GHz in the E-Band. The output power at the antenna flange is around -5 dBm. The in-loop phase noise at 10 kHz offset is better than -78 dBc/Hz in a wide frequency range of 32.1 GHz.

Airborne applications demand exceptional overall radar system performance and eminently high output power for high range target detection. The frequency modulated continuous wave (FMCW) radar system presented in this article is capable of achieving this task due to its high output power at 94-GHz center frequency with over 26-GHz tuning range. Nevertheless, the radar still provides a small form factor and low power consumption of 4.25 W at 5 V single Universal Serial Bus (USB) supply. The key system component is a Silicon Germanium (SiGe) bipolar complementary metal-oxide-semiconductor (BiCMOS) monolithic microwave integrated circuit (MMIC) that contains a 94-GHz voltage-controlled oscillator (VCO), and a 27-GHz VCO for dual-loop phase-locked loop (PLL) stabilization, a power amplifier (PA), and two receive mixers. It generates frequency ramps between 83- and 109-GHz with a maximum output power of 19.7 dBm at its output after the bond wires on the printed circuit board (PCB) and 14.8-dBm output power at the radar’s transmit (TX)-waveguide WR-10-flange. The sensor was also tested in a temperature range from −40 °C to +70 °C with menial deviation. Thus, the system offers high system dynamic range and far distance target detection range. Following a detailed system description, we finally present the FMCW range and Doppler measurements performed with the presented radar sensor as well as the application on unmanned aerial vehicles (UAVs) for flight altitude control and as airborne collision avoidance system (ACAS).

The trend towards smaller form factor MIMO radar systems is enabled by modern SiGe BiCMOS technologies in which more functionality can be integrated into MMICs, including digital control logic beside analog low- and high-frequency circuits for signal generation, transmitting, receiving and also modulating waveforms, like in this work. Industrial measurement, automotive or security applications demand small imaging radar systems. For this purpose, a compact K-Band MIMO radar system with code-division multiplex (CDMA)-modulation for TX-separation was developed. It is based on an ultra-wideband (UWB) SiGe chipset suitable for MIMO operation which provides MMICs for signal generation of over 40 GHz bandwidth below 60 GHz, a 4-channel phase-shifting transmitter that operates between 1–30 GHz and a 4-channel receiver that operates between 1–65 GHz. Following the description of the system architecture, the SiGe MIMO chipset is explained, before 3D MIMO measurement results are presented at the end.

Fields of application like industrial measurement, security, and material characterization with harsh demands for high spatial resolution require FMCW radar systems with high absolute bandwidth. Hereby, close adjacent targets can be distinguished from each other. Usually those systems are designed at very high frequencies around 100 GHz and above because here, sensors with high bandwidth can be designed with less effort but signal handling, antenna design and high output power is more difficult and harder to achieve at those frequencies. In this work, a modern SiGe BiCMOS process was used to develop an ultra-wideband (UWB) bistatic FMCW radar MMIC with over 40 GHz continuous bandwidth below 60 GHz. This MMIC is the key component of the presented ultra-wideband FMCW radar system. The high bandwidth is generated by down-converting two high-frequency VCOs at around 100 GHz but merely the down-converted signal below 60 GHz of both VCOs which is easier to handle leaves the MMIC. The output signal provides a frequency range which corresponds to the sum of the bandwidths of both VCOs. This leads to a radar system that achieves ultra-wide continuous bandwidth at moderate frequencies for high spatial resolution.

This paper presents a 3D millimeter wave system for robotic mapping and localization as well as for security scan applications. The system at 80 GHz uses a mechanically rotating radar system in azimuth and elevation to generate the 3D image. With this configuration a 3dB spread of an single reflector results in an azimuth and elevation resolution of 3.8°. An FMCW-Radar bandwidth can be variable adjusted up to 25 GHz, which results in an maximum range resolution of 6 mm. The principle of the system is presented including the functional structure and the hardware design.

LiDAR sensors are very popular for mapping and localisation with mobile robots, yet they cannot handle harsh environments, containing smoke, fog, dust, etc. On the other hand, radar sensors can overcome these situations, but they are not able to represent an environment in the same quality as a LiDAR due to their limited range and angular resolution. In the following article, we present further results regarding SLAM involving the mechanical pivoting radar (MPR), which is a 2D high bandwidth radar scanner that was introduced in Fritsche et al. (Radar and LiDAR sensor fusion in low visibility environments, 2016, [8]). We present two strategies for fusing MPR and LiDAR data to achieve SLAM in an environment with low visibility. The first approach is based on features and requires the presence of landmarks, which can be extracted with LiDAR and MPR. The second SLAM approach is based on scan registration and requires a scan fusion between the two sensors. In the end, we show our experiments, involving real fog, in order to demonstrate, how our approaches make SLAM possible in harsh environments.

LiDAR sensors are unable to detect objects that are inside or behind dense smoke, fog or dust. These aerosols lead to problems for environmental modeling with mobile robotic platforms. For example, if a robot equipped with a LiDAR is surrounded by dense smoke, it can neither localize itself nor can it create a map. Radar sensors, on the other hand, are immune to these conditions, but are unable to represent the structure of an environment in the same quality as a LiDAR due to limited range and angular resolution. In this paper, we introduce the mechanically pivoting radar (MPR), which is a 2D high bandwidth radar scanner. We present first results for robotic mapping and a fusion strategy in order to reduce the negative influence of the aforementioned harsh conditions on LiDAR scans. In addition to the metric representation of an environment with low visibility, we introduce the LRR (LiDAR-Radar-Ratio), which correlates with the amount of aerosols around the robot discussing its meaning and possible application.

In this paper an ultrawideband near range 3D-SAR imaging system using a 80 GHz radar is presented and the effects of radar position errors on the 3D image quality are investigated in detail. Position errors of the radar during the measurement are caused by vibration or oscillation of the moving platform, on which the radar is mounted. In the ideal case, a regular 2D-grid of measurement points is required to synthesize a two dimensional aperture for 3D-SAR reconstruction. Simulated quadratic, sinusoidal and statistic errors have been added to the ideal measurement to analyze the effects on the 3D-SAR image.

A novel concept for standoff detection and classification of hidden weapons and explosives is proposed, based on a multi-channel millimetre wave FMCW radar system operated in a bistatic SAR geometry. Therefore, a linear positioner combined with a flexible waveguide is applied. In order to compensate target motion during the measurement time, a second receiving channel with a fixed monostatic geometry is used. This paper describes measurement setup, system configuration and some steps of signal processing. Preliminary results from a simulation based on ideal point scatterers are also presented.

Helicopters are essential for any mission of humanitarian or assisting nature in disaster areas. Very often they have to cope with missing infrastructure and extreme environmental conditions. Besides darkness and adverse weather, dust and snow are two of the most dangerous conditions for helicopter landing. At the time being, helicopter pilots have no adequate sensors to get information on height and drift with the necessary precision under dust and snow conditions. Only radar sensors in the microwave or millimetre wave region offer the capability of sufficient transmission through fog, dust and snow. Employing an appropriate signal processing, also the necessary drift information can be extracted from the Doppler shift of the transmitted radar signal. A demonstrator is under development, based upon distributed and netted millimetre wave radar modules, to extract precise height and drift information to be fed into the avionic system of the helicopter and to be used as an aid for landing and take-off during adverse environmental conditions. The paper discusses the design of the broad band miniature millimetre wave radar modules, the design of the broadband high gain antennas and the implementation into the system demonstrator.

A light weight, transportable measurement system for the inspection of suspicious luggage in a threat situation has been developed, based upon miniaturized millimetre wave radar modules operating at W-band. To allow for a sufficient detection capability of objects hidden within a piece of ownerless luggage within a passenger terminal at a sufficiently short scanning time, a radar approach rather than a passive radiometer technique was chosen. It is generally recognized, that only synthetic aperture is able to supply a sufficient geometrical resolution at high imaging speed. Moreover a radar can also deliver a three dimensional description for the position and the shape of a concealed object using high range resolution techniques. The paper describes the measurement set-up and the evaluation algorithm. Typical examples for different set-ups are presented.

The paper describes different technological efforts to demonstrate the usefulness of millimeter wave sensors for security applications. The scope of the work covers a miniature radar in a portal geometry using a near field SAR approach for passenger control and the same radar hardware with a slightly modified scanning approach for luggage inspection employing a three dimensional SAR algorithm. Another approach to detect concealed weapons and explosives is by using radiometric systems. In principle, a scanner using this technique measures the thermal noise of the radiation reflected by the body. This is equivalent to the temperature on the surface of the body. The main difficulty with this technique is the realization of a fast scanning algorithm. The status of both approaches is surveyed and typical results are discussed.

A light weight, transportable measurement system for the inspection of suspicious humans and of luggage in a threat situation has been developed, based upon miniaturized millimetre wave radar modules operating at W-band. To allow a sufficient detection capability of objects hidden under the clothing or within a piece of luggage within buildings at a sufficiently short scanning time, a radar approach rather than a passive radiometer technique was chosen. It is generally recognized, that only synthetic aperture is able to supply a sufficient geometrical resolution at high imaging speed. Moreover a radar can also deliver a three dimensional description for the position and the shape of a concealed object using high range resolution techniques. The paper describes the measurement set-up and the evaluation algorithm. Typical examples for different set-ups are presented.

Sensors used for Security purposes have to cover the non-invasive inspection of persons, baggage and letters with the aim to detect weapons, explosives and chemical or biological threat material. Currently, emphasis is placed on system concepts and technologies for this type of applications, employing millimeterwave-, submillimeterwave- and terahertz sensors. This is based on the capability of these frequency bands to look through textiles and the possibility to achieve a geometric resolution which is sufficient to resolve critical items within the necessary range. Using multiple frequencies promises to give more detailed information about the structure of the observed objects. Furthermore, to overcome the limitations of passive millimeter- and submillimeterwave sensors which depend on indirect illumination, systems using miniaturized mmw-radar modules are applied as well.