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Distance resolution of cooperative sensors is limited by the signal bandwidth. For the transmission mainly lower frequency bands are used which are more narrowband than classical radar frequencies. To compensate this resolution problem the combination of a pseudo-noise coded pulse compression system with superresolution time of arrival estimation is proposed. Coded pulsecompression allows secure and fast distance measurement in multi-user scenarios which can easily be adapted for data transmission purposes (Morhart and Biebl, 2009). Due to the lack of available signal bandwidth the measurement accuracy degrades especially in multipath scenarios. Superresolution time of arrival algorithms can improve this behaviour by estimating the channel impulse response out of a band-limited channel view. For the given test system the implementation of a MUSIC algorithm permitted a two times better distance resolution as the standard pulse compression. [ABSTRACT FROM AUTHOR]

We present an improved approach for a Round Trip Time of Flight distance measurement system. The system is intended for the usage in a cooperative localisation system for automotive applications. Therefore, it is designed to address a large number of communication partners per measurement cycle. By using coded signals in a time division multiple access order, we can detect a large number of pedestrian sensors with just one car sensor. We achieve this by using very short transmit bursts in combination with a real time correlation algorithm. Furthermore, the correlation approach offers real time data, concerning the time of arrival, that can serve as a trigger impulse for other communication systems. The distance accuracy of the correlation result was further increased by adding a fourier interpolation filter. The system performance was checked with a prototype at 2.4 GHz. We reached a distance measurement accuracy of 12 cm at a range up to 450 m. [ABSTRACT FROM AUTHOR]

More than 400 000 wild animals are killed or severely injured every year during spring time pasture mowing. Conventional methods for detection and removal or expulsion of animals before mowing are either inefficient or very time-consuming. The first really working method is based on a pyro-detector which senses the temperature contrast between the animals body and the surrounding pasture. Unfortunately, the detection reliability of this sensor decreases with increasing ambient temperature and strong sunlight, i.e. for typical weather conditions, when pasture is mowed, especially around noon. In this paper, a detector is presented that exhibits complementary behaviour. It works best during dry conditions (i.e. around noon), but has a tendency to false alarms when dew is present (i.e. morning and evening). The sensor is based on a commercial, low-cost Doppler module at 24 GHz. It senses the difference of radar cross section between the animals body (high water content, specular reflection) and the pasture (low water content, diffuse reflection). The signal is analysed by means of a non-linear Wigner time-frequency transformation. Experimental results are presented for a laboratory setup as well as for measurement in actual springtime pasture. The results prove that a microwave sensor is capable of reliably detecting animals of the size of a fawn even if it is covered by a layer of pasture. [ABSTRACT FROM AUTHOR]

We present a low-cost 24 GHz VCO that is based on a microstrip design combined with discrete packaged devices. The output frequency is generated by a harmonic oscillator. The tunabilty was reached using a varactor diode. Two versions of the VCO were built, one has a wide tuning range of 1.1GHz and the other one has a high output power of 3.7 dBm. [ABSTRACT FROM AUTHOR]

Numerous standard RF circuits like directional couplers, hybrids, amplitude modulators, oscillators, etc. require a 50Ω termination. Additionally, in several measurement scenarios, ports have to be terminated. Such terminations are preferable of the same waveguide type as the circuits to avoid degradation of their performance. In general, standard fabrication steps are desired as they are cost-effective. The straightforward solution is a 50Ω resistor shunted to ground by means of a via. Partial wraparound SMD resistors in a 0402 size have low parasitics making them applicable up to K-band. However, for RF, this combination suffers from the considerable inductive parasitics of the via. Different approaches to avoid the vias, with varying disadvantages exist. We analyzed the approach of broadband matching the non ideal viaresistor combination to 50Ω by means of a filter structure. The realization uses only standard design and fabrication methods. The design procedure can easily be adapted to arbitrary substrates and fabrication technologies. The assembled 50Ω termination was measured using TRL calibration with a VNA. Therefore its characteristics are determined in the intended plane and it can be directly included into a planar 50Ω circuit. The measured terminations showed a VSWR better than 1.34 within the whole band from DC to K-band, and within 57% of the band (including the 24 GHz ISM band) the VSWR is better than 1.22. [ABSTRACT FROM AUTHOR]

A novel gain/bandwidth enhanced leaky‐wave microstrip line antenna with circular polarisation (CP) is proposed. Different from common leaky‐wave antennas with an open, short or resistive termination, this antenna consists of a leaky‐wave rampart‐line antenna terminated with a CP patch radiator. The energy from the feeding point is first radiated by the rampart‐line antenna, while the remaining part is radiated through the CP patch element. As a result, the size of the leaky‐wave part can be reduced. The resulting size of this antenna is only 1.6 × 1.6 λ2.4G (λ2.4G is free space wavelength at 2.4 GHz). Energy loss caused by the resistive termination is avoided, so that high efficiency is achieved – higher than 85% within the whole band. By introducing slight CP centre frequency difference between the patch and rampart antenna, two CP resonances were generated and the 3 dB axial ratio (AR) bandwidth is substantially broadened. Measured AR bandwidth is 9.9% (2.30–2.54 GHz). Its − 10 dB impedance bandwidth is 2.25 GHz to higher than 3 GHz, and peak gain is 13.2 dBic. The proposed antenna has a fully used radiation aperture, achieving a favourable performance, such as wide bandwidth, high gain, and a relatively stable (less tilted) boresight radiation. [ABSTRACT FROM AUTHOR]

In this work a new method for the evaluation of UHF RFID Direction of Arrival (DoA) estimation systems is developed and demonstrated. Instead of simulating the system performance or manually measuring it in realistic or ideal environments, a method for the evaluation of DoA systems using received signals produced by a target simulator is proposed. The simulator generates the signals for each channel of the DoA estimator by attenuating and phase shifting the signals of an UHF RFID chip to replicate the signal propagation conditions for a chosen tag distance and arrival angle. This combines the advantages of the simulative approach and real world evaluation: it is fast, reproducible and doesn't require special measurement environments. To facilitate this method, plane and spherical wave signal models for the simulation of RFID targets are derived, multichannel phase-shifting and attenuation hardware for the simulation of such signals is presented and a demonstrative evaluation of a RFID DoA estimation system is performed, replicating evaluation scenarios in non reflective and multipath environments. [ABSTRACT FROM AUTHOR]

This study presents the first continuously tuneable, interference-based W-band single-pole double-throw (SPDT), fully implemented in subwavelength (sWL) dielectric fibre topology. Key components are the phase shifters in the two branches of the SPDT, which are realised as line sections filled with liquid crystal. They allow not only to adjust the signal ratios at the two output ports but also to tune the operating frequency between 93 and 110 GHz with isolation >25 dB. The first proof-of-concept SPDT demonstrator is realised and characterised at W-band. However, concept and technology are scalable to higher frequencies. The complete SPDT with the WR10-to-sWL fibre transitions exhibits an insertion loss (IL) at the thru-port between 5 and 7 dB in the frequency range from 85 to 110 GHz, where back-to-back measurements of the transitions itself already indicate an IL of up to 1.6 dB. The measurements at the isolated port of the SPDT exhibit transmission coefficients of less than -25 dB between 93 and 110 GHz with a minimum of -40 dB. [ABSTRACT FROM AUTHOR]

As technology is moving towards miniature structures, demand for designing efficient compact antennas is increasing simultaneously. So it would be valuable to improve the features of small antennas, such as bandwidth and gain. A compact chip-resistor loaded microstrip antenna at 2.48 GHz frequency for industrial scientific and medical (ISM) band, with dimensions of 10 × 10 mm is presented in this paper. With a novel geometry design, antenna is promoted to an active integrated antenna (AIA) on a two-layer printed circuit board (PCB), which contains passive antenna and active circuitry with a common ground plane. A monolithic amplifier is used to have an improvement around 10 dB in antenna gain. The impedance bandwidth has been increased during chip-resistor loading and adding active circuitry processes. For chip-resistor loaded antenna, that is 5.7 and 9.48% in simulation and measurement respectively. Moreover, the active integrated antenna has the measured impedance bandwidth of 58.7%. Since the low gain and narrow bandwidth of compact microstrip antennas might be a challenge for their operation, by compensating these drawbacks, proposed antenna would become more practical for special medical diagnostic applications, where doctors need stronger signals for monitoring. [ABSTRACT FROM AUTHOR]

Future driver assistance systems will rely on accurate, reliable and continuous knowledge on the position of other road participants, including pedestrians, bicycles and other vehicles. The usual approach to tackle this requirement is to use on-board ranging sensors inside the vehicle. Radar, laser scanners or vision-based systems are able to detect objects in their line-of-sight. In contrast to these non-cooperative ranging sensors, cooperative approaches follow a strategy in which other road participants actively support the estimation of the relative position. The limitations of on-board ranging sensors regarding their detection range and angle of view and the facility of blockage can be approached by using a cooperative approach based on vehicle-to-vehicle communication. The fusion of both, cooperative and non-cooperative strategies, seems to offer the largest benefits regarding accuracy, availability and robustness. This survey offers the reader a comprehensive review on different techniques for vehicle relative positioning. The reader will learn the important performance indicators when it comes to relative positioning of vehicles, the different technologies that are both commercially available and currently under research, their expected performance and their intrinsic limitations. Moreover, the latest research in the area of vision-based systems for vehicle detection, as well as the latest work on GNSS-based vehicle localization and vehicular communication for relative positioning of vehicles, are reviewed. The survey also includes the research work on the fusion of cooperative and non-cooperative approaches to increase the reliability and the availability. [ABSTRACT FROM AUTHOR]

Direction-of-arrival (DOA) estimation algorithms deliver very precise results based on good and extensive antenna array calibration. The better the array manifold including all disturbances is known, the better the DOA estimation result. A simplification or ideally an omission of the calibration procedure has been a long pursued goal in the history of array signal processing. This paper investigates the practicability of some well known calibration algorithms and gives a deeper insight into existing obstacles. Further analysis on the validity of the common used data model is presented. A new effect in modeling errors is revealed and simulation results substantiate this theory. [ABSTRACT FROM AUTHOR]

Active UHF RFID systems are often used for identifying, tracking and locating objects. In the present publication a GPS- based localization system for saving fawns during pasture mowing was introduced and tested. Fawns were first found by a UAV before mowing began. They were then tagged with small active RFID transponders, and an appropriate reader was installed on a mowing machine. Conventional direction-of-arrival approaches require a large antenna array with multiple elements and a corresponding coherent receiver, which introduces a large degree of complexity on the reader-side. Instead, our transponders were equipped with a small GPS module, allowing a transponder to determine its own position on request from the reader. A UHF link was used to transmit the location to a machine- mounted reader, where a second GPS receiver was installed. Using information from this second position and a machine- mounted magnetometer for determining the relative north direction of a vehicle, relative distance, and angle between GPS receivers can be calculated. The accuracy and reliability of this novel method were tested under realistic operating conditions, considering critical factors such as the height of grass, the lying position of a fawn, humidity and geographical area. [ABSTRACT FROM AUTHOR]

This study provides a simple broadband method for determining the dielectric properties of laminate substrate materials used in integration and packaging solutions for commercial millimetre-wave applications. Relative permittivity and loss tangent are extracted from coplanar lines using closed-form equations that account for as-fabricated transmission line dimensions. The method is applied to a low loss substrate alumina and further tested on glass impregnated epoxy resin materials with metals that have an appreciable metal surface roughness. The work expands existing material characterisation methods that are typically based on thin films. The dielectric substrates are thin, similar to integrated circuits, but the metal thicknesses remain on the order of packaging substrates. This study considers the critical parameters and manufacturing features for designs and millimetre-wave material measurements on these types of materials. The method has an accuracy of within 10% of known values, utilises off-the-shelf software solutions when available, and requires no fixturing beyond the sample material. Error analysis is provided with material information on Isola FR408 up to 110 GHz. [ABSTRACT FROM AUTHOR]

The concept of connected vehicles is with great potentials for enhancing the road transportation systems in the future. To support the functions and applications under the connected vehicles frame, the estimation of dynamic states of the vehicles under the cooperative environments is a fundamental issue. By integrating multiple sensors, localization modules in OBUs (on-board units) require effective estimation solutions to cope with various operation conditions. Based on the filtering estimation framework for sensor fusion, an ensemble Kalman filter (EnKF) is introduced to estimate the vehicle's state with observations from navigation satellites and neighborhood vehicles, and the original EnKF solution is improved by using the cubature transformation to fulfill the requirements of the nonlinearity approximation capability, where the conventional ensemble analysis operation in EnKF is modified to enhance the estimation performance without increasing the computational burden significantly. Simulation results from a nonlinear case and the cooperative vehicle localization scenario illustrate the capability of the proposed filter, which is crucial to realize the active safety of connected vehicles in future intelligent transportation. [ABSTRACT FROM AUTHOR]

The monitoring of human breathing activity during a long period has multiple fundamental applications in medicine. In breathing sleep disorders such as apnea, the diagnosis is based on events during which the person stops breathing for several periods during sleep. In polysomnography, the standard for sleep disordered breathing analysis, chest movement and airflow are used to monitor the respiratory activity. However, this method has serious drawbacks. Indeed, as the subject should sleep overnight in a laboratory and because of sensors being in direct contact with him, artifacts modifying sleep quality are often observed. This work investigates an analysis of the viability of an ultrasonic device to quantify the breathing activity, without contact and without any perception by the subject. Based on a low power ultrasonic active source and transducer, the device measures the frequency shift produced by the velocity difference between the exhaled air flow and the ambient environment, i.e., the Doppler effect. After acquisition and digitization, a specific signal processing is applied to separate the effects of breath from those due to subject movements from the Doppler signal. The distance between the source and the sensor, about 50 cm, and the use of ultrasound frequency well above audible frequencies, 40 kHz, allow monitoring the breathing activity without any perception by the subject, and therefore without any modification of the sleep quality which is very important for sleep disorders diagnostic applications. This work is patented (patent pending 2013-7-31 number FR.13/57569). [ABSTRACT FROM AUTHOR]

This paper presents the design and the implementation of a fully monolithic coupled-oscillator array, operating at 6 GHz with close to zero coupling phase, in 0.25 μm BICMOS silicon germanium process. This array is made of four LC-NMOS differential VCOs coupled through a resistor. The single LC-NMOS VCO structure is designed and optimized in terms of phase noise with a graphical optimization approach while satisfying design constraints. At 2.5 V power supply voltage, and a power dissipation of only 125 mW, the coupled oscillators array features a simulated phase noise of −127.3 dBc/Hz at 1 MHz frequency offset from a 6 GHz carrier, giving a simulated phase progression that was continuously variable over the range −64° < Δϕ < 64° and −116° < Δϕ < 116°. This constant phase progression can be established by slightly detuning the peripheral array elements, while maintaining mutual synchronization. [ABSTRACT FROM AUTHOR]

Up to now, SAR systems are a well known possibility for long-range detection. Applying them for shortrange applications with wide-beam antennas, of course, does not increase the resolution but the probability to detect hidden targets with an anisotropic radar cross section signifi-cantly in comparison to other detection systems. Working with an appropriate wavelength even improves the possiblity to look through natural cover like grass. An application is detecting fawn while pasture mowing. The main issue in such applications is the antenna's motion in range direction as it is carried by cars or traction engines. If motion is not compensated, the phase cannot be reconstructed correctly, the resolution gets poorer and, in worst case, the target even disappears. Conventional methods for motion compensation either fail for wide beam antennas, since for contributions of wide angles the phase reconstruction is incorrect, or is not applicable for realtime data processing, because the processing time due to interpolation or similar steps is very high. We present a method of image reconstruction regarding motion of the antenna as well as wide beamwidth. This method is analyzed concerning processing time in comparison to the conventional image reconstruction. In our system we use a combination of algorithms. There is shown a comparison for different algorithms dependent of the antenna's motion and aperture angle. [ABSTRACT FROM AUTHOR]