New wireless wearable monitoring systems integrated in professional garments require a high degree of reliability and autonomy. Active textile antenna systems may serve as platforms for body-centric sensing, localisation, and wireless communication systems, in the meanwhile being comfortable and invisible to the wearer. We present a new dedicated comprehensive design paradigm and combine this with adapted signal-processing techniques that greatly enhance the robustness and the autonomy of these systems. On the one hand, the large amount of real estate available in professional rescue worker garments may be exploited to deploy multiple textile antennas. On the other hand, the size of each radiator may be designed large enough to ensure high radiation efficiency when deployed on the body. This antenna area is then reused by placing active electronics directly underneath and energy harvesters directly on top of the antenna patch. We illustrate this design paradigm by means of recent textile antenna prototypes integrated in professional garments, providing sensing, positioning, and communication capabilities. In particular, a novel wearable active Galileo E1-band antenna is presented and fully characterized, including noise figure, and linearity performance.

TanDEM-X (TDX; TerraSAR-X add-on for digital elevation measurement) is an innovative spaceborne X-band earth observation mission that will be launched in June 2010. This paper gives an overview of the TDX mission concept, summarizes the basic products and illustrates the achievable performance. In more detail the effect of quantization on the interferometric performance is discussed. Finally, new imaging techniques are outlined.

Phase unwrapping (PU) is one of the key processing steps in reconstructing the digital elevation model (DEM) of a scene from interferometric synthetic aperture radar (InSAR) data. The PU problem entails the estimation of an absolute phase from observation of its noisy principal (wrapped) values. Recently, PU approaches based on Kalman filtering have proved their efficacy in tackling the PU problem even when strong discontinuities of the height profile and noisy data are involved. This paper presents a novel multichannel InSAR PU algorithm using several interferometric SAR images based on the extended Kalman filter. The proposed technique exploits the capability of the Kalman algorithm to simultaneously perform noise filtering, PU, and multi-sensor data fusion. The proposed method, even being a Bayesian estimator, optimally fuses height information coming from an additional maximum likelihood estimator (MLE) combining the benefits of both the Bayesian and the non-Bayesian approaches. The performance of the proposed algorithm has been tested on simulated interferometric images proving the effectiveness of the proposed method.

A simple electromagnetic model of wind-turbine's main structural elements as the linear wired structures is developed to simulate the temporal patterns of observed radar return Doppler spectra (micro-Doppler). Using the model, the micro-Doppler for different combinations of the turbines rotation frequency, radar pulse repetition frequency, and duration of the Doppler measurement interval are analyzed. The model is validated using the PARSAX radar experimental data. The model ability to reproduce the observed Doppler spectra main features can be used for development of signal-processing algorithms to suppress the wind-turbines clutter in modern Doppler radars.

A novel idea for generating directional electromagnetic beam using a metamaterial absorber for enhancing radiation from a microwave antenna in the S-band is presented herewith. The metamaterial structure constitutes the well-known stacked dogbone doublet working in the absorption mode. The reflection property of the dogbone metamaterial absorber, for the non-propagating reactive near-field, is utilized for achieving highly enhanced and directional radiation characteristics. The metamaterial absorber converts the high-spatial reactive spectrum in the near-field into propagating low-spatial spectrum resulting in enhanced radiation efficiency and gain. The gain of a printed standard half-wave dipole is enhanced to 10 dBi from 2.3 dBi with highly directional radiation characteristics at resonance.

An efficient analysis of time-modulated array (TMA) toward realizing less-attenuating radiation patterns with simultaneously suppressed sidelobe and sidebands is presented in this paper. In this framework, an optimal outer element-controlled time sequence is derived. The proposed time scheme, along with optimized array excitations, is profitably applied for the desired solution. TMAs are considered unconventional alternatives to the phased arrays. The desired array radiation features can be attained by periodically enabling and disabling the array elements through high-speed switches. Despite the advantages of architectural simplicity and real-time reconfigurability of periodic time sequences, time-domain antenna arrays inherently generate unavoidable sideband radiations (SRs). The undesired SRs obtained at multiple harmonics around the carrier frequency of the array resembles power loss in unintended directions. This paper aims to minimize the SRs as well as the sidelobe level (SLL) for an efficient analysis of time-modulated linear array (TMLA) with high-directive radiation patterns. The starting instants and the period of on-times are optimized to generate a unique shifted time scheme for the edge elements of the TMLA to reduce the sideband levels (SBLs). The array excitations and the uniform spacing between the elements are also optimized together with the shifted time scheme for the coveted solution. Other methods of suppressing SLLs and SBLs with shifted pulse schemes and sub-sectioned pulse schemes are also presented for a fair comparison. Modified versions of the particle swarm optimization algorithm (PSO) are applied for the desired solutions. The optimal results attained by wavelet mutation-based novel PSO is compared with the conventional PSO and the modified novel PSO-based results. The representative results are reported, and the superior performance abilities of the proposed method compared to other published studies are assessed.

In this paper, a 1.8–2.6 GHz wideband rectenna is designed for radio frequency (RF) energy harvesting in the context of wireless sensor nodes (WSN). To assess the feasibility of ambient RF energy harvesting, the power density from RF base stations is analyzed through statistical measurements. Power density measurements are also performed close to Wi-Fi routers. Using these results, a methodology based on impedance matching network adaptation and maximum power transfer is proposed to design the wideband RF harvester. Using this method, three RF bands, i.e. GSM1800, UMTS and WLAN, are covered. The theoretical analysis is confirmed by simulations and measurements. From measurements results, the prototype RF-to-DC conversion efficiency is 15% at −20 dBm from 1.8 to 2.6 GHz. It is shown that with three RF sources in the chosen bands, each emitting at 10 dBm, the RF-to-DC conversion efficiency is 15% better compared to that measured with a single RF source. Finally, 7 µW is harvested at 50 m from a GSM1800 and UMTS base station. This value confirms the RF harvester workability to supply small sensors.

In this paper, we present a continuously tunable phase shifter realized in MEMS technology. Varactors with liquid crystal as a tunable dielectric layer underneath gold bridges are used to build a loaded line phase shifter. Measurements show that the phase shifter has a differential phase shift of 92°, a figure of merit (FoM) of 42°/dB and an input matching of −19 dB at 76 GHz.The tuning speed of the phase shifter is measured at different temperatures between 10 and 50°C. The realized phase shifter can be used in combination with MEMS switches in order to build a 360° tunable reflection phase shifter.

In this paper, an orthogonal frequency-division multiplexing (OFDM) waveform radar sensing approach is demonstrated based on field measurements at C-band. We demonstrate a concept that is based on the exploitation of typical wireless communication transmissions to perform passive, distributed radar sensing. Our concept is based on an OFDM radar that operates in the modulation symbol domain and can be well integrated into existing OFDM receivers. The measurement setup and the signal processing steps for the OFDM radar are described. The results show that the passive, distributed radar sensing approach can be used to detect and localize moving cars and even pedestrians in automotive intersection scenarios.

In this work, we propose a broadband, polarization-insensitive and wide incident angle stable metamaterial absorber (MA) based on the resistive film. The absorber consists of a three-layer structure with each layer of dielectric substrate printed with different shapes of resistive film. The multilayer structure not only extends the absorption bandwidth but also maintains high absorption under large wave incident angles. Numerical simulation shows that the absorptivity of a normal incident wave is above 90% in the frequency range 2.34–18.95 GHz, corresponding to a relative absorption bandwidth of 156%. Moreover, the whole MA structure has a total thickness of 11.3 mm, corresponding to 0.09 λ0 at its lowest absorption frequency. Due to the high symmetry of the structure, the absorber has good polarization insensitivity. In addition, for both transverse electric and transverse magnetic incidence, the proposed absorber achieves an absorptivity of more than 80% at incident angles of up to 45° and thus has good stability for wide incident angles. The absorption principle of the absorber is analyzed by the surface current and power loss density distribution. Parameter analysis is also performed for bandwidth optimization. Due to its advantages of wideband absorption with high efficiency, the proposed absorber has the potential to be applied to the energy-harvesting and electromagnetic stealth fields.

An alternative approach is based on statistically computed signal analysis technique for the design of antenna array exhibiting lower side lobes in their radiation pattern. New and generalized expressions for the array factor of all physically realizable linear antenna arrays are introduced. An algorithm based on the statistically computed signal analysis is designed. By considering the random elements, distance between the sensors, their mean, variance, average amplitude pattern and correlation of the amplitude between the two angles, some mathematical formulations have been done and shown with the help of MATLAB. Based on these generalized expressions, a new way of synthesizing arrays with reduced side lobes is available. It applies to end fire antenna array, which may have either even or odd numbers of sensors with restricted elements spacing. Final expressions shown are a clear relationship between elements excitation and null location in the radiation patterns.

The implementation of advanced multi-level modulation schemes such as quadrature phase-shift keying (QPSK) in contrast to the conventional on–off keying is crucial to further boost the terahertz (THz) communications speed. Thereby, carrier phase noise reduction in the THz range is one of the key goals that need to be urgently achieved. In this paper, the photonic-based THz sources and the phase noise problem are briefly summarized. Then, a low phase-noise photonic source based on the stimulated Brillouin scattering (SBS) optical fiber cavity is first applied for a 300-GHz-band QPSK wireless communication link. The highest data rate at forward-error-correction limited condition was 15 Gbaud utilizing the SBS-based photonic source with a small transmit power of ~ −36 dBm. Its transmission characteristics are evaluated and compared with the conventional optical frequency comb generator (OFCG)-based source at 5 Gbaud. The proposed SBS-based photonic source has been proven to offer better performances than the OFCG-based source with respect to the phase noise, optical carrier to noise ratio, and bit error rate in communications.

Two compact H-band (220–325 GHz) low-noise millimeter-wave monolithic integrated circuit (MMIC) amplifiers have been developed, based on a grounded coplanar waveguide (GCPW) technology utilizing 50 and 35 nm metamorphic high electron mobility transistors (mHEMTs). For low-loss packaging of the circuits, a set of waveguide-to-microstrip transitions has been realized on 50-μm-thick GaAs substrates demonstrating an insertion loss of <0.5 dB at 243 GHz. By applying the 50 nm gate-length process, a four-stage cascode amplifier module achieved a small-signal gain of 30.6 dB at 243 GHz and more than 28 dB in the bandwidth from 218 to 280 GHz. A second amplifier module, based on the 35-nm mHEMT technology, demonstrated a considerably improved gain of 34.6 dB at 243 GHz and more than 32 dB between 210 and 280 GHz. At the operating frequency, the two broadband low-noise amplifier modules achieved a room temperature noise figure of 5.6 dB (50 nm) and 5.0 dB (35 nm), respectively.

In this work, a voltage tunable interdigital capacitor loaded with liquid crystal (LC) is investigated and its application for a composite right/left-handed leaky-wave antenna (LWA) is demonstrated. The tuning capability of the varactor is confirmed by simulation and measurement. A material tunability of 25% of the used LC yields a measured varactor tunability of 9%. Based on this, a tunable LWA with a beam scanning of 14 degrees at 26.7 GHz is implemented and measured.

In this paper, a three layered stacked circularly polarized rectangular dual band microstrip antenna with a defected ground structure (DGS) and a feed network with stub (showing dual wideband characteristic) is designed, fabricated, and tested for WLAN, Zig bee, Wi-Max, and IMT band applications. The proposed antenna is fabricated on an FR4 substrate with dielectric constant (εr) of 4.4; tanδ of 0.0024 and a height of 1.57 mm.The antenna has a surface area of 4.8 × 4.1 cm2 and a total height of 5.1 mm. The designed antenna covers two wireless bands from 2.39 to 2.64GHz and 3.39–3.76 GHZ with impedance bandwidths (VSWR < 2) of 250 MHz (9% bandwidth centered at 2.515 GHz) and 370 MHz (10% bandwidth centered at 3.57 GHz), respectively. This antenna is capable of covering IEEE 802.11b/g/n standards of WLAN from 2.4 to 2.485 GHz, bluetooth applications from 2.4 to 2.483 GHz, ZigBee applications from 2.4 to 2.485 GHz, IEEE 802.16/ Wi-MaX applications from 3.4 to 3.69 GHz and international mobile telecommunications (IMT) band from 3.4 to 3.6 GHz. As the antenna is circularly polarized, the misalignment of the receiver with transmitter does not affect the performance of the system. The antenna designing was done using CST MWS V'10 and the prototype of the designed antenna was tested for the validation of S11 (dB) and gain results against the simulated ones experimentally. The proposed antenna shows a gain of 4.08 dBi at 2.5 GHz and a gain of 5.024 dBi at 3.51 GHz.

This paper presents a substrate-integrated waveguide (SIW) mixed electric and magnetic coupling structure implemented on a single-layer substrate to create finite transmission zeros (TZs), which can be used to design microwave filters with higher frequency selectivity. Mixed coupling is realized by three slot-lines on the top metal plane combined with an iris-window between two adjacent SIW cavities. The electric and magnetic coupling can be separately controlled by adjusting the dimensions of the slot-lines and the width of the iris-window, and a controllable TZ below or above the passband can be produced. Furthermore, a detailed analysis of the mixed coupling structure is presented. To demonstrate the validity of the proposed structure, third- and fourth-order cross-coupled generalized Chebyshev bandpass filters are designed and fabricated using the standard printed circuit board process. The experimental results are in good agreement with the simulation results. The filters exhibit simple structure and good frequency selectivity.

This paper presents three iterations of a coplanar waveguide-fed H-tree fractal antenna. Increasing the number of iterations allows us obtaining a multi-band and broad-band behavior. The proposed antennas are a good solution for wireless local area networks IEEE802.11 a/h/j/n/ac/y, worldwide interoperability for microwave access system IEEE802.16, radio frequency identification, C-band, high performance radio LAN, and ultra wideband applications. The simulations were performed in FEKO 6.3. The measurements were performed by the network analyzer HP 8719C.

In this contribution a dual-band, dual-polarized microstrip antenna element for array applications is presented. The patch antenna is designed to operate simultaneously at around 30 and 20 GHz, the up- and downlink frequencies of modern Ka-band satellite communication systems. The antenna is smaller than half the freespace wavelength at 30 GHz to enable its utilization as array element of dual-band ground terminals. Integrating transmitter and receiver circuits allows, in turn, for a very compact active terminal solution. To minimize production cost, the design is carried out in standard multilayer printed circuit board technology. The antenna features two distinct polarization ports suitable for either dual linear or dual circular polarization if both ports are excited in quadrature. The single antenna design process is described in detail and simulation and measurement results are presented. Finally, different arrays based on this patch antenna are evaluated by simulation and measurements.

A novel compact directional antenna with improved gain is proposed for microwave breast imaging (MBI) applications. The radiating fins are modified by etching several slots to make the antenna compact and enhance antenna performance in terms of bandwidth, gain, efficiency, and directivity. Several parameters are studied and optimized to frequency from 3.1 to 6.5 GHz, which is typically used in the breast imaging system. The electrical length of the antenna is 0.39λ × 0.46λ × 0.01λ at the lower frequency band. The result shows that the antenna exhibits −10 dB impedance bandwidth of 4.3 GHz (2.7–7 GHz) with directional radiation pattern. The peak gain of the proposed prototype is 7.8 dBi and fractional bandwidth is 92%. The time domain results show that the fidelity factor for face to face is 0.92 and for side by side is 0.62, which prove the directivity and lower distortion of the signal. The proposed prototype is successfully simulated, fabricated, and measured.

Use of frequency-selective surfaces (FSSs) is proposed to shield rooms against electromagnetic fields in order to achieve secure indoor communications and reduce human exposure to external fields. The secure room is designed using two-layer FSSs with an FR4 substrate to cover 10–12 GHz frequency band. Different elements in each layer and shift in the position of elements are the reasons for more than 3 GHz bandwidths in X band. The performance of the structure is also stable versus the misaligned position of layers. An equivalent circuit model is proposed for the structure and results show −20 dB isolation between inside and outside of the room in the desired frequency band. Bio tissue is located inside the cubic structure with FSS walls and the results of the specific absorption rate are demonstrated and compared in two rooms with FSS cover on concrete walls and a room with concrete walls. The 17 × 17 cm2 two-layer FSS is fabricated for the measurement and the results are presented. The designed FSS can be used in the construction of wave-isolated room for any application.