Silent Speech Interfaces (SSIs) are systems developed to reconstruct speech based on non-acoustic bio-signals generated by brain, muscular or articulatory activity. A broad variety of sensing methods have been employed in SSIs, but determining a single optimal sensor configuration is generally a challenge. This work focuses on investigating sensing configurations for an on-body radar-based SSI and evaluating them based on their phoneme recognition performance. Audio and radar data were recorded synchronously by 8 native German speakers. One emitting and two receiving antennas were placed on the cheeks of each speaker in three different configurations, which were evaluated by nested cross-validated Support Vector Machines (SVMs). With these sensing configurations, higher accuracies than in previous works with on-body radar-based SSIs were achieved for individual speakers and for a multi-speaker evaluation. This work succeeds to produce an antenna placement guideline for future recordings with similar SSIs.

Silent speech interfaces (SSIs) are systems that can enable speech communication in the partial or total absence of the acoustic speech signal. The research on SSIs includes command word recognition, speech synthesis and continuous phoneme/word recognition. The focus of this work is to perform continuous phoneme recognition with a radar-based SSI. Audio and radar data were recorded synchronously during continuous speech of one speaker. Six feature sets based on combinations of the magnitude spectrum, the phase spectrum, and the impulse response of the radar data were used as input to the recognition task and compared to each other and to a benchmark acoustic feature set based on the audio data. With a CNN-MLP followed by a Viterbi-based biphone phoneme decoder, the lowest mean phoneme error rate (PER) obtained by any radar-based feature set was 45.62%, which is 15% higher than the mean PER achieved by the benchmark acoustic feature set. The most common sources of errors were minimal pairs of consonants. The results of this work are promising and point towards future possible improvements for radar-based continuous phoneme recognition.

Distinctive propagation characteristics of millimeter wave (mmWave) bands require channel sounding for link management. Reported mmWave channel-sounder setups support only simplex operation while depending on bulky and expensive lab equipment; especially for frequency domain channel sounding (FCS), which can be performed with simple hardware. This work presents a solution in the form of a 60 GHz modular front-end designed using off-the-shelf components with tailor-made passive circuits and high-frequency interconnections, all compatible with printed circuit technology. An FCS setup is developed using two units of the designed transceiver front-ends, which can sweep 6 GHz bandwidth with 1 MHz resolution. An antenna duplexing circuitry is also presented, which enables each front-end unit to use a single transmit-receive antenna ensuring a high correlation between the round-trip channels. To the best of the authors’ knowledge, this work reports the first FCS setup, which preserves channel reciprocity in round-trip sounding. The application of the designed system is showcased through a channel reciprocity key generation (CRKG) algorithm, which exploits the high correlation between the forward and receive channels to demonstrate a physical layer security system functional at 60 GHz.

With the explosion of the number of compute nodes, the bottleneck of future computing systems lies in the network architecture connecting the nodes. Addressing the bottleneck requires replacing current backplane-based network topologies. We propose to revolutionize computing electronics by realizing embedded optical waveguides for onboard networking and wireless chip-to-chip links at 200-GHz carrier frequency connecting neighboring boards in a rack. The control of novel rate-adaptive optical and mm-wave transceivers needs tight interlinking with the system software for runtime resource management.

Besides the recognition of audible speech, there is currently an increasing interest in the recognition of silent speech, which has a range of novel applications. A major obstacle for a wide spread of silent-speech technology is the lack of measurement methods for speech movements that are convenient, non-invasive, portable, and robust at the same time. Therefore, as an alternative to established methods, we examined to what extent different phonemes can be discriminated from the electromagnetic transmission and reflection properties of the vocal tract. To this end, we attached two Vivaldi antennas on the cheek and below the chin of two subjects. While the subjects produced 25 phonemes in multiple phonetic contexts each, we measured the electromagnetic transmission spectra from one antenna to the other, and the reflection spectra for each antenna (radar), in a frequency band from 2-12 GHz. Two classification methods (k-nearest neighbors and linear discriminant analysis) were trained to predict the phoneme identity from the spectral data. With linear discriminant analysis, cross-validated phoneme recognition rates of 93% and 85% were achieved for the two subjects. Although these results are speaker- and session-dependent, they suggest that electromagnetic transmission and reflection measurements of the vocal tract have great potential for future silent-speech interfaces.

This paper presents the Radar for Icy Moon Exploration (RIME) that is a fundamental payload in the Jupiter Icy Moon Explorer (JUICE) mission of the European Space Agency (ESA). RIME is a radar sounder aimed to study the subsurface of Jupiter's icy moons Ganymede, Europa and Callisto. The paper illustrates the main goals of RIME, its architecture and parameters and some recent advances in its design.

Ultrawideband (UWB) radio technology for wireless implants has gained significant attention. UWB enables the fabrication of faster and smaller transceivers with ultralow power consumption, which may be integrated into more sophisticated implantable biomedical sensors and actuators. Nevertheless, the large path loss suffered by UWB signals propagating through inhomogeneous layers of biological tissues is a major hindering factor. For the optimal design of implantable transceivers, the accurate characterization of the UWB radio propagation in living biological tissues is indispensable. Channel measurements in phantoms and numerical simulations with digital anatomical models provide good initial insight into the expected path loss in complex propagation media like the human body, but they often fail to capture the effects of blood circulation, respiration, and temperature gradients of a living subject. Therefore, we performed UWB channel measurements within 1-6 GHz on two living porcine subjects because of the anatomical resemblance with an average human torso. We present for the first time, a path loss model derived from these in vivo measurements, which includes the frequency-dependent attenuation. The use of multiple on-body receiving antennas to combat the high propagation losses in implant radio channels was also investigated.

This paper presents the Radar for Icy Moons Exploration (RIME) instrument, which has been selected as payload for the JUpiter Icy moons Explorer (JUICE) mission. JUICE is the first Large-class mission chosen as part of the ESA's Cosmic Vision 2015-2025 programme, and is aimed to study Jupiter and to investigate the potentially habitable zones in the Galilean icy satellites. RIME is a radar sounder optimized for the penetration of Ganymede, Europa and Callisto up to a depth of 9 km in order to allow the study of the subsurface geology and geophysics of the icy moons and detect possible subsurface water. In this paper we present the main science goals of RIME, the main technical challenges for its development and for its operations, as well as the expected scientific returns.

We describe a prototype ultrawideband radar. We show how the system was designed and how the hardware was developed for the radar prototype. Waveform generation, radar parameters, and signal processing for the stepped frequency waveform are discussed. The radar operates from 500 MHz to 3 GHz with a nominal resolution of 6 cm in air. The advantage of the stepped frequency approach over an impulse radar is better matching between the transmitted waveform and the receiver. We use range gating to improve the system dynamic range. The advantages are illustrated with laboratory measurements and field measurements from glacial ice and permafrost in Svalbard, showing penetration depths of 11 m. Antennas which do not require contact with the ground were developed and used in the experiments.

The Water Ice Subsurface Deposit Observation on Mars (WISDOM) Ground Penetrating Radar (GPR) is one of the instruments that have been selected as part of the Pasteur payload of the European Space Agency's (ESA's) 2018 ExoMars Rover mission. The main scientific objectives of the mission are to search for evidence of past and present life and to characterize the nature of the shallow subsurface. The Rover is equipped with a drill that can sample the subsurface down to a depth of approximately 2 m. The WISDOM GPR is the only instrumentation capable of obtaining information about the nature of the subsurface along the Rover path before drilling. WISDOM has been designed to explore the first ~3 m of the subsurface with a vertical resolution of a few centimeters. The paper presents a description of the WISDOM instrument with a particular emphasis on the electronic architecture and antenna design that have been chosen to meet the challenging technical objectives. Some preliminary measurements obtained with the prototype are given to illustrate the instrument's potential performance.

This work presents results for wireless outdoor MIMO transmission experiments at 2.68 GHz, which were conducted in an urban residential area, using realistic handset and base station antennas. Characteristic parameters of MIMO systems, obtained from measurements, were compared to theoretical results. From the comparison it could be concluded that the transmission of two spatial streams was well supported in the investigated 2 × 2 MIMO system, even with receive antenna element spacings as small as a quarter of the wave length. Comparing different receive antennas, the MIMO performance was found to be dominated by the received signal power rather than the spatial correlation.

Transmitter Leakage has a significant impact on zero-IF transceivers for mobile FDD terminals and therefore must be compensated. When Tx Leakage compensation approaches are designed, their capability to adapt to changing leakage conditions must be specified. Therefore, in this contribution we analyse the time variance of Tx Leakage considering the UMTS SAW duplexer B7632 of EPCOS as an example and derive a worst case estimate of Tx Leakage coherence time.