This article presents the development and validation of a retroreflective structure designed to improve the radar detection of amateur rockets. The work was carried out as part of the Student Design Competition (SDC) at the International Microwave Symposium (IMS) 2025 in San Francisco. The goal was to increase the radar visibility of rockets with cylindrical fuselages, as these are difficult to detect at high angles of incidence due to their low monostatic radar cross section (RCS). The proposed solution employs passive, air-filled slotted waveguide (SWG) antennas realized through additive manufacturing and metallic coating. The structure meets the stringent requirements for weight, size, and mechanical stability. Experimental validation shows that the developed structure significantly improves radar detection compared to a simple cylindrical body.

We present a novel system that performs three-dimensional scans of the environment using a monostatic frequency modulated continuous wave (FMCW) radar sensor with a center frequency of 80 GHz and a bandwidth of 20 GHz. The system uses a flat metal surface to deflect the electromagnetic waves emitted by the radar sensor like a mirror. The orientation is adjusted in two axes to scan the surrounding space and objects. Signal processing is used to generate a three-dimensional representation of the measured radar data.

Optimized rehabilitation after joint replacement surgery or other medical procedures affecting the musculoskeletal system requires practical movement analysis systems that enable the continuous and precise gait monitoring of patients in everyday life. To address this need, we present a system consisting of a frequency-modulated continuous-wave (FMCW) radar sensor and active frequency-doubling tags designed for accurate long-term monitoring. By using a harmonic measurement concept in which the tags double the frequency of the transceiver signal, a high signal-to-interference-and-noise ratio (SINR) is achieved, ensuring that the tags stand out clearly from the clutter produced by the leg. With our system, we particularly focus on a phase-based angle determination within the sagittal plane, enabled by two closely spaced receive antennas, allowing for more accurate and reliable gait monitoring compared to our previous system based on a bilateration method. By utilizing millimeter waves in the frequency range 56-63 GHz for transmission and 112-126 GHz for reception, we achieve a compact sensor size sufficient for the application. Based on measurements taken in a gait laboratory, we demonstrate that our system is capable of measuring the distance and angle between the sensor and tags during gait with an accuracy of up to 1.73 mm and 0.93 degrees, respectively, using a stationary camera-based motion capture (MoCap) system as a reference.

In this paper, we introduce a compact 6 x 8 channel multiple-input multiple-output frequency-modulated continuous-wave radar system capable of determining the three-dimensional positions of targets despite utilizing a linear virtual array. The compact system, containing two cascaded radar transceiver ICs, has 48 virtual channels. We conduct a direction of arrival estimation with these virtual channels to determine the azimuth angle. To overcome the spatial limitation of the linear array, we use frequency-steered transmit antennas, which vary their main lobe direction during the frequency chirp, allowing the elevation angle to be determined by using a sliding window fast Fourier transform algorithm. In this study, we present the system's concept along with the associated signal processing. By taking measurements in different scenarios, each with differently placed corner reflectors, we investigate the capability of the system to separate adjacent targets concerning range, azimuth, and elevation. These measurements are additionally employed to point out the design trade-offs inherent to the system.

Although traffic safety continues to improve overall, fatalities of vulnerable traffic participants and pedal cyclists specifically have reached 30-year highs. While automotive radar sensors continue to advance and are integrated in more and more vehicles, they are not ideally suited to detect pedal cyclists, especially in complicated traffic scenarios. To mitigate the problem of the lower radar-cross section (RCS) of the cyclist, equipping them with harmonic radio frequency identification (RFID) tags is proposed. The presented system showcases the benefits of this approach by being able to conduct conventional automotive radar measurements and detect tags simultaneously. In this work, we present the printed-circuit boards (PCBs) and the necessary chipset, while especially focusing on the design of a power-efficient harmonic RFID tag. By improving the gain per current of an amplifier chain, the tag enables a range sufficient for urban scenarios while consuming little enough current to be powered by battery-operated lights. This enables the detection of pedal cyclists even in complicated scenarios at a distance of up to 80 m.

In this paper, an FMCW MIMO radar is presented which is capable of determining the three-dimensional location of targets even though it has a linear virtual array. The compact system is based on two cascaded radar transceiver ICs, which provide a total of 48 virtual channels. With these channels, a direction of arrival estimation is performed to determine the azimuth angle. To overcome the spatial limitation of the linear array, frequency-steered TX antennas are used which vary their main beam direction during the frequency chirp, allowing the elevation angle to be determined. In this paper, the system’s concept and the corresponding signal processing is presented. The ability to separate adjacent targets in both the azimuth and elevation planes is investigated by various measurements.

This paper presents a wearable harmonic radar system for biomechanical joint angle estimation to be used in medical rehab applications. Active frequency doubling reflector tags are placed on a patient's limbs and get detected by a dual receive channel harmonic radar front end. Target-tracking is realized by use of a motion-model based estimator with minimal quadratic error association. Range and angle estimation is performed by bilateration of individual channel target tracks. The resulting positional data is to be used as input for a model-based physiological joint angle estimation, which is not part of this paper. The system is tested on a healthy subject performing gait with multiple strides at a comfortable pace. The positional tracking is compared to equivalent data captured by a marker-based optical motion capturing system, which is the gold standard for gait analysis.

In this paper, a wearable hand-held guidance aid for visually impaired people is presented. The system is based on radar technology to feature robustness and reliability as is needed by the use case. Measured distances get translated into an intuitively interpretable sound that gets rendered in a three-dimensional virtual audio space by use of two inertial measurement units and a custom head-related impulse response database. The functionality of the system is shown by the measurement in an everyday scenario.

In this paper, a novel simulation model for the design of frequency steered slotted waveguide antennas is presented. The model is based on field simulations of the single slot element and the connecting waveguide curves. The model yields the lengths and the widths of all slot elements according to given amplitude weights in order to realize a certain far field pattern.

In this paper, a new approach for a MIMO FMCW radar system with direction of arrival estimation capabilities in azimuth and elevation direction is presented. This is achieved using an equally spaced linear virtual antenna array with frequency steered transmit antennas and frequency selective signal processing. The system and antenna concepts together with the necessary signal processing are presented and then evaluated based on a simulated scenario.

Sound is extremely important to our daily navigation, while sometimes slightly underestimated relative to the simultaneous presence of the visual sense. Indeed, the spatial sense of sound can immediately identify the direction of danger far beyond the restricted sense of vision. The sound is then rapidly and unconsciously interpreted by assigning a meaning to it. In this paper, we therefore propose an assisted-living device that deliberately stimulates the sense of hearing in order to assist vision-impaired people in navigation and orientation tasks. The sense of vision in this framework is replaced with a sensing capability based on radar, and a comprehensive radar profile of the environment is translated into a dedicated sound representation, for instance, to indicate the distances and directions of obstacles. The concept thus resembles a bionic adaptation of the echolocation system of bats, which can provide successful navigation entirely in the dark. The process of translating radar data into sound in this context is termed “sonification”. An advantage of radar sensing over optical cameras is the independence from environmental lighting conditions. Thus, the envisioned system can operate as a range extender of the conventional white cane. The paper technically reports the radar and binaural sound engine of our system and, specifically, describes the link between otherwise asynchronous radar circuitry and the binaural audio output to headphones.

One of the main challenges in everyday life of visually impaired people is the orientation in unknown environments. Especially the avoidance of collision with obstacles when walking in public places is a major problem. In this paper a concept for a radar based navigation device for visually impaired people is investigated. The device scans the environment around the user and translates the distance information into a 3D audio signal, which is fed to a hearing device. The main sensor is a highly integrated FMCW radar with a center frequency of 80 GHz and a bandwidth of 24 GHz. One of the main challenges in the development of the device is the design of an antenna that can be worn on the head and allows to scan a sufficient angle around the user.