Anastasia Lavrenko

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Verified

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• Dr. -Ing.
• Professor (Assistant) at University of Twente

Harmonic radars that use passive nonlinear tags as targets are disadvantaged by the low power of the return signal, which significantly reduces their maximum operating range. To address this limitation, a novel dual-mode X-band FMCW harmonic radar capable of receiving both harmonic and intermodulation signal returns was developed. This paper verifi...

Conventional passive harmonic tags lack built-in capabilities for unique tag identification. Using frequency-selective tags can solve this problem. This paper presents a compact narrowband harmonic tag design based on a spiral loop topology that is easily frequency tunable. The presented measurement results confirm the frequency selectivity of the...

Passive harmonic tags are used to detect and track targets in highly cluttered environments or when the object of interest is too small to fit an active transmitter. This paper presents an approach to analytically model tag performance based on its equivalent circuit model. Tested on wire-based tags, it shows good correspondence with measurement re...

This paper presents a novel single layer compact harmonic transponder tag operating at 2.9 GHz in the forward link (harmonic exciter to harmonic tag) and 5.8 GHz in the return link (harmonic tag to harmonic reader). The proposed tag consists of an asymmetric folded meander-line dipole antenna that is directly matched to the low-voltage Schottky dio...

The emergence of miniaturized medical robots capable of performing targeted therapeutic procedures in deep-seated anatomical regions presents an alternative to conventional medical treatments. However, it remains a significant challenge to accurately locate the miniaturized robots in the complex environments of living organisms. Taking advantage of...

In this paper, we propose a dual-mode FMCW harmonic radar capable of both harmonic and intermodulation operation. The presented system prototype operates in the X-band in the uplink (radar to the target) and the K-band in the downlink (target to the radar). For intermodulation operation, an additional external X-band tone transmitter is utilized to...

In distributed radio localisation systems based on time-of-flight measurements accuracy of time synchronisation between radio nodes places limits on the achievable performance. In this work, we evaluate feasibility of using pulse-per-second reference signals provided by off-the-shelf timing GNSS modules as a means for wireless synchronisation of di...

This work presents a novel single layer dual-band meander-line harmonic tag antenna implemented on a thin flexible substrate. The proposed prototype consists of folded asymmetric meander-line dipoles that are matched to a low-voltage Schottky diode to generate second harmonic frequency of 5.8 GHz when illuminated by a fundamental frequency of 2.9 G...

Harmonic radar systems are used to interrogate, or track a location of, passive nonlinear targets in highly cluttered environments, and they are notorious for their poor power efficiency and low detection ranges. Due to harmonic operation, the received signal power close to maximum range becomes inversely proportional to the fourth power of the for...

In harmonic radar (HR), the transmitter illuminates a nonlinear target (the tag), causing the return signal to consist of harmonics at multiples of the transmitted carrier frequency. Of them, the second harmonic is usually the strongest and the one to which the receiver is tuned. This frequency difference distinguishes the tag reflection from envir...

In harmonic radar (HR), the radio frequency transmitter illuminates a nonlinear target (the tag), causing the return signal to consist of harmonics at multiples of the transmitted carrier frequency. Of them, the second harmonic is usually the strongest and the one to which the receiver is tuned. This frequency difference distinguishes the tag refle...

In this paper, we present a design and first proof-of-concept test results of a distributed radio-localization system for tracking of moving targets with a swarm of drones. In particular, we develop and test a software framework that uses bistatic ranges to follow a target in-flight. We conduct full-system flight test with up to two drones in the a...

Harmonic radar transponders are passive RF tags that produce a harmonic response when illuminated with an RF signal. With a Schottky diode as the main component, the tag current is usually modelled as an exponential function of antenna voltage, resulting in an approximate polynomial function for small signals. We introduce the Lambert function that...

We present two frequency modulated continuous wave (FMCW) harmonic radar prototypes for application in insect tracking. They respectively operate in the maritime radar allocations of the S-band and X-band. Short-range operation ensures that the modules are compact enough to be used as portable instruments or even mounted onto an unmanned aerial veh...

Passive harmonic transponders are used in applications where weight and size restrictions are prohibitive to the use of active radio transmitters, e.g., for insect tracking. A typical harmonic transponder tag consists of a wire dipole antenna and a Schottky diode with a parallel inductance. Despite the simplicity in tag circuit, designing lightweig...

Harmonic tags are passive radio transponders that create a harmonic return when illuminated with an RF signal. They are used to reduce the effect of clutter for otherwise indistinguishable targets. A classic harmonic tag consists of a dipole antenna, a Schottky diode and an inductive loop. In this work, we evaluate the performance of an off-centre...

Harmonic radar is commonly used in localisation and tracking applications where weight and size restrictions do not allow the use of active radio transmitters. It relies on the operation of a passive transponder tag attached to the target that creates a harmonic response when illuminated with a radio signal. The main bottleneck of harmonic radar sy...

In this paper, we address the problem of harmonic radar tag detection in the presence of non-ideal linearisation of radar sensors. Due to extremely low signal levels that are expected from passive harmonic tags, inherent non-linearities of radar sensors coupled with parasitic signal leakage from the transmitter to the receiver constitute major prob...

In compressed sensing, the choice of the sensing matrix plays a crucial role: it defines the required hardware effort and determines the achievable recovery performance. Recent studies indicate that by optimizing a sensing matrix, one can potentially improve system performance compared to random ensembles. In this work, we analyze the sensitivity o...

In this paper, we develop an approach for a combining matrix design for 2D DoA estimation with compressive arrays. In compressive arrays, a (larger) number of antenna outputs is linearly combined to a lower number of receiver channels with the aim to reduce hardware complexity while not compromising the estimation performance. To achieve this goal,...

In this paper, we consider the problem of localizing multiple non-collaborative transmitters by a network of distributed sensor nodes. The nodes are equipped with versatile sensing capabilities allowing them to estimate the time differences of arrival (TDoAs) and/or the directions of arrival (DoAs) of the incoming waves. We formulate the localizati...

In this work, we estimate relative autocorrelation functions of multiple unknown transmissions that occupy distinct narrowband frequency bands from their sub-Nyquist samples. To be able to do so, we employ a network of distributed sensing nodes that are equipped with a sub-Nyquist receiver system and have access to a common clock. Utilizing low-rat...

Spectrum sensing is a crucial component of opportunistic spectrum access schemes, which aim at improving spectrum utilization by allowing for the reuse of idle licensed spectrum. Sensing a spectral band before using it makes sure the legitimate users are not disturbed. Since information about these users' signals is not necessarily available, the s...

Compressed sensing (CS) is a sampling paradigm that allows to simultaneously measure and compress signals that are sparse or compressible in some domain. The choice of a sensing matrix that carries out the measurement has a defining impact on the system performance and it is often advocated to draw its elements randomly. It has been noted that in...

Compressed sensing (CS) is a sampling paradigm that allows to simultaneously measure and compress signals that are sparse or compressible in some domain. The choice of a sensing matrix that carries out the measurement has a defining impact on the system performance and it is often advocated to draw its elements randomly. It has been noted that in t...

Compressed Sensing (CS) is a recently emerged framework for simultaneous sampling and compression of signals that are sparse or compressible in some representation. Besides signal reconstruction, the CS framework is often adopted for compressive parameter estimation. Performance metrics commonly used in CS are well suited for performance evaluation...

In this paper we investigate the design of compressive antenna arrays for direction of arrival (DOA) estimation that aim to provide a larger aperture with a reduced hardware complexity by a linear combination of the antenna outputs to a lower number of receiver channels. We present a basic receiver architecture of such a compressive array and intro...

In this paper we investigate the design of compressive antenna arrays for direction of arrival (DOA) estimation that aim to provide a larger aperture with a reduced hardware complexity by a linear combination of the antenna outputs to a lower number of receiver channels. We present a basic receiver architecture of such a compressive array and intro...

Spectrum sensing is a crucial component of opportunistic spectrum access schemes, which aim at improving spectrum utilization by allowing for the reuse of idle licensed spectrum. Sensing a spectral band before using it makes sure the legitimate users are not disturbed. Since information about these users' signals is not necessarily available, the s...

Wideband spectrum sensing plays a crucial role in a number of applications among which the cognitive radio (CR) is one of the most prominent. In this work we consider a scenario where the wide band of interest is comprised of multiple communication channels occupied by several independent transmissions. Due to the propagation conditions, some of th...

In recent years it has been shown that wideband analog signals can be sampled significantly below the Nyquist rate without loss of information, provided that the unknown frequency support occupies only a small fraction of the overall bandwidth. The modulated wideband converter (MWC) is a particular architecture that implements this idea. In this pa...

Efficient recovery of sparse signals from few linear projections is a primary goal in a number of applications, most notably in a recently-emerged area of compressed sensing. The multiple measurement vector (MMV) joint sparse recovery is an extension of the single vector sparse recovery problem to the case when a set of consequent measurements shar...

Wideband signal acquisition and spectrum sensing play a crucial role in a number of applications. In this work we discuss the task of blind spectrum sensing of frequency-sparse wideband signals sampled at sub-Nyquist rates. We show how in a generic sub-Nyquist sampling framework the results of the support recovery can be directly used for coarse mu...

The application of the Compressed Sensing (CS) paradigm to the sampling of sparse wireless signals allows a significant reduction of the sampling rate compared to the one dictated by the Nyquist sampling theorem. The majority of the theoretical results derived within CS are expressed in terms of the known sparsity order of the signal. In this work...

Recovery of sparse signals from few linear measure-ments is a central task of the recently emerged area of compressed sensing. Evidently, the design of the measurement plays a key role in the signal recoverability. In this contribution we analyze the explicit dependence between a deterministic sensing matrix and the support recovery performance. We...

In this paper we discuss the estimation of the spar-sity order for a Compressed Sensing scenario where only a single snapshot is available. We demonstrate that a specific design of the sensing matrix based on Khatri-Rao products enables us to transform this problem into the estimation of a matrix rank in the presence of additive noise. Thereby, we...

Compressed sensing allows for a significant reduction of the number of measurements when the signal of interest is of a sparse nature. Most computationally efficient algorithms for signal recovery rely on some knowledge of the sparsity level, i.e., the number of non-zero elements. However, the sparsity level is often not known a priori and can even...

Cognitive Radio Ad Hoc Network (CRAHN) is an emergent paradigm in wireless communications that brings the promise of mitigating the well-known scalability problems of classical Mobile Ad Hoc Networks (MANETs). By integrating in its architecture novel dynamic spectrum access algorithms, the CRAHN is expected to increase usage efficiency of available...

This paper investigates the performance of energy detection (ED) for random signals having sufficient autocorrelation. As opposed to the uncorrelated noise, practical communication signals have autocorrelation, which can be exploited for optimal detection if the correlation is known a priori. Otherwise ED can be employed as a generalized sensing me...

The cognitive radio (CR) concept has appeared as a promising technology to cope with the spectrum scarcity caused by increased spectrum demand due to the emergence of new applications. CR can be an appropriate mean to establish self-organization and situation awareness at the radio interface, which is highly desired to manage unexpected situations...