Here we consider a disordered system of interacting quantum dots—nanostructures with applicability in systems ranging from quantum computing to next-generation displays. Quantum dots facilitate absorptive and emissive processes at frequencies over timescales independent of those in the incident radiation; by treating the system semiclassically we maintain the discrete dynamics inherent to quantum objects without resorting to second quantization to describe electromagnetic fields. Our solution proceeds via determination of source wavefunctions through evolution of the differential Liouville equations and evaluation of radiation patterns through integral equation techniques. We employ a highly-tuned predictor-corrector integration scheme to advance the source wavefunctions in time; the polarizations that arise then serve as sources within the integral equations that we use to propagate the field. This coupled solution produces a description of both the quantum and electromagnetic dynamics at each timestep giving rise to lasing effects, non-linear propagation, coupled Rabi oscillations, and other optical phenomena.

We discuss a new electromagnetic particle-in-cell algorithm for the simulation of Maxwell-Vlasov equations on unstructured grids. The use of discrete exterior calculus and differential forms of various degrees enables numerical charge conservation from first principles, down to the numerical precision floor. In addition, energy conservation is obtained via a symplectic field update. The algorithm is illustrated for the modeling of high-power microwave devices based on Cerenkov radiation driven by relativistic plasma beams.

Wireless communications are expected to take place in increasingly complicated scenarios, such as dense urban, forest, tunnel and other significant cluttered environments. A key challenge emerging is to understand the physics and characteristics of wireless channels in complex environments, which are critical for the analysis, design, and application of future mobile and wireless communication systems. The objective of this work is to investigate high-resolution, high-performance computational algorithms for extreme-scale channel modeling in real-world environments. The system-level large scene analysis is enabled by the novel, ultra-parallel algorithms on the emerging exascale high-performance computing (HPC) platforms. The results lead to much greater channel model resolution than existing deterministic channel modeling technologies. All relevant propagation mechanisms are accounted for in first-principles. Such a modeling framework will be critical to gaining fundamental physics of wireless propagation channels in real-world scenarios.

A rigorous yet computationally efficient three-dimensional nu-merical method has been proposed based on modified alternat-ing-direction-implicit (ADI) finite difference time domain meth-ods (FDTD) and it has the capability of modeling the eccentric property of magnetic material being anisotropic, dispersive or nonlinear. The proposed algorithm solves Maxwell’s equations and LLG equations simultaneously, requiring only tridiagonal matrix inversion as in ADI FDTD. The accuracy of the modeling has been validated by the simulated dispersive permeability of a continuous ferrite film with a 1.5 um-thickness, using a time-step size 104 times larger than the Courant limit. The permeability agrees with the theoretical prediction and magneto-static spin wave modes are observed. Moreover, electric current sheet radia-tors close to perfect electrical conductors loaded with 2 um-thick ferrite films are simulated, which exhibit a radiation efficiency 20dB higher than conventional dipole antennas on the same scale.

Recently, keen interest has been shown in using microwaves as the heat source for materials manufacturing processes that rely on sintering. We present here a two-dimensional model of microwave sintering that accounts for the chain of physical phenomena that influence the process (i.e., electromagnetics, heat transfer and mechanical deformation), including the dependence of dielectric and thermal properties on the temperature and relative density of the sample. The model relies on finite difference methods for the electromagnetic and thermal models, and a Master Sintering Curve to construct the inverse function for density evolution, and is presented together with its computer implementation as a series of Python scripts, which runs quickly and whose accuracy is demonstrated via comparison to experimental results from literature.

The design and characterization of a 0.3–3 GHz SiGe cryogenic low noise amplifier is presented. The integrated-circuit amplifier was implemented in the ST BiCMOS 9MW technology platform. At 15 K physical temperature, it achieves a gain greater than 22 dB, input and output return losses better than 10 dB, and an average noise temperature of 2.8 K over the 0.3–3 GHz frequency range. To the best of the authors’ knowledge, this amplifier achieves the best noise performance reported to date for an integrated SiGe low noise amplifier.

A 4-8 GHz Silicon-Germanium (SiGe) cryogenic low-noise amplifier (LNA) was designed and implemented using GF BiCMOS8HP process. The amplifier provides 30-dB and 26-dB of gain while dissipating 760 μW and 580 μW DC power, respectively. The noise temperature is approximately 8K across the frequency band. To the best of the authors’ knowledge, this is the lowest reported power to date for a wide-band cryogenic integrated circuit LNA in this frequency range.

Four ultra-low noise cryogenic MMIC LNAs suitable for the Square Kilometer Array (SKA) band 2 to 5 (0.95 – 13.8 GHz) have been designed, fabricated, packaged and tested. The LNAs are based on 4x50, 8x50 and 16x50 µm HEMTs, designed for stable cryogenic operation, allowing the combination of good noise performance and return loss. The lowest noise temperatures measured in the four bands were 1.0 K, 1.2 K, 1.6 K and 2.6 K, respectively.

We have investigated the cryogenic stability of two-finger InP HEMTs aimed for Ka-band ultra-low noise amplifiers (LNAs). Unlike two-finger transistors with a large gate-width above 2 x 50 µm, the transistors with a small gate-width exhibit unstable cryogenic behavior. The instability is suppressed by adding a source air-bridge. The stabilizing effect of the air-bridge is demonstrated both on device and circuit level. A three-stage 24–40 GHz monolithic microwave integrated circuit (MMIC) LNA using a stabilized 100-nm HEMT technology is presented. The amplifier achieves a record noise temperature of 7 K at 25.6 GHz with an average noise of 10.6 K across the whole band at an ambient temperature of 5.5 K. The amplifier gain is 29 dB ± 0.6 dB exhibiting very stable and repeatable operation. To our knowledge, this amplifier presents the lowest noise temperature reported so far for InP cryogenic LNAs covering the Ka-band.

In this paper we report ultra-low-noise amplifier modules and amplifier module chains for V-band (50-75 GHz). The amplifier chips were fabricated in a 35-nm InP HEMT technology and packaged in WR15 waveguide housings utilizing alumina E-plane waveguide probes. The amplifier modules achieve 18 to 27 K noise temperatures from 50 to 75 GHz when cryogenically cooled to 21 K. When measured through a mylar vacuum window, a cascade of two amplifier modules achieves a receiver noise temperature of 18.5 K at 58 GHz. A second chain has a measured receiver noise temperature between 20 to 28 K for the whole V-band. To the best of authors’ knowledge these are the lowest LNA noise temperatures for V-Band reported to date.

A cryogenic low noise amplifier that operates across the E and W-bands, from 65 GHz to 116 GHz, has been developed using 0.1-μm InP HEMT technology. Such wideband performance makes this work suitable for the ALMA telescope where two of its bands, 67-90 GHz of Band 2 and 85-116 GHz of Band 3, can be combined into one. At an ambient temperature of 5.5 K, this Wband LNA demonstrates an average noise temperature of 24.7 K with more than 21 dB gain and +/- 3.0 dB gain flatness from 65 GHz to 116 GHz. To the best knowledge of the authors, this combination of bandwidth, gain flatness and noise temperature has not been demonstrated before.

Key factors in the utility of small satellites are the responsiveness of orbiting space assets, the cost savings over larger, more durable satellites, and the potential benefit to the tactical user. As electronics and RF technologies become increas-ingly compact and more capable, small satellites offer many ad-vantages over their larger counterparts from technology refresh rate and timely access for the tactical user to significantly reduced launch costs. This paper reviews several small satellite-related development efforts for tactical military applications with an emphasis on the communications technologies being matured.

Recent advances in low-power millimeterwave low-noise amplifier technologies have enabled the hosting of high-performance atmospheric sounding instruments on very small satellites.The Microsized Microwave Atmospheric Satellite, second generation (MicroMAS-2), will demonstrate temperature sounding near 118 GHz and moisture sounding near 183 GHz. MicroMAS-2a and MicroMAS-2b are scheduled to launch in 2017. The Microwave Radiometer Technology Acceleration (MiRaTA) cubesat will launch in 2017, and will fly a tri-band sounder (60, 183, and 206 GHz) and a GPS radio occultation (GPS-RO) sensor. Both MicroMAS and MiRaTA are 3U CubeSats. The Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission utilizes these technology advancements in a complete mission with approximately 12 CubeSats similar in capability to MicroMAS-2. TROPICS is expected to launch in 2020. The Earth Observing Nanosatellite-Microwave (EON) concept is a 12U CubeSat designed to provide most of the capabilities of current operational microwave sounders.

Historically, satellites have been built with large budgets and expensive, bespoke, "rad-hard" technology. For typical low Earth orbit missions, however, designers can now leverage commercial components to reduce cost and development time. Commercial processors provide these satellites with computational horsepower comparable to terrestrial desktop systems ... which leads to the temptation of terrestrial desktop software and all of the cyber security headaches and mistakes made in that realm over the years. We highlight key differences in processing environments, identify common tools for security design and application, and provide design guidelines that can lead to more secure on-orbit processing while remaining mindful of the overarching drumbeat of "smaller, faster, cheaper."

Microsatellites, commonly defined as having a mass of less than 100kg, are being developed and launched with increasing frequency over the past decade. While this interest has led to rapid development of miniaturized electronics, communications and sensing components, microsatellites still lack significant maneuvering capability. Maneuverable microsatellites have the potential to allow for cost-effective satellite constellations, and disaggregated systems needing long-duration formation flying. This paper surveys and provides a performance comparison for some promising microsatellite propulsion technologies. Two recently developed propulsion technologies, green monopropellants and electrosprays, show great promise for increasing the maneuverability of severely volume and power constrained microsatellites.

Emerging small satellite systems technologies will be presented. Discussed application areas include remote sensing and U.S. Army applications. In addition, small satellite design for security and enabling technologies for small satellite maneuverability will be highlighted.

RF interference mitigation for communication systems in spectrally congested and contested environments is a key to meeting the ever increasing need for reliable and resilient communication and data networks. Interference may come from known sources of interference as well as from unknown sources. The power level of interference experienced by a victim radio receiver may vary over a very wide range. Multiple interfering RF systems on the platforms of interest can be located very near radio systems on those platforms causing co-site interference.

Current U.S.Navy ships employ multiple federated Radio Frequency (RF) apertures to perform Radar, Electronic Warfare (EW),Communication(Comms),Signals collection, and Information Operations(I/O)functions. Historically, each function (and hence system) has its own aperture, electronics, operators, and logistics/maintenance infrastructure. This approach results in systems competing for limited space and optimum placement and results in an inefficient use of resources and Electro Magnetic Interference/Compatibility (EMI/EMC) problems.

Cognitive radar is an emergent technique in modern radar system development. Cognitive radar achieves new levels of radar performance by leveraging mechanisms present in biologi-cal systems and incorporating them into the function and opera-tion of the radar system. Here recent developments and future directions of cognitive radar are presented with a focus on the de-tection of radar targets. These studies require a deeper examina-tion into both the nature of the operating environment and the characteristics of targets themselves. Additionally, sources of in-terference which serve to impact radar performance are examined under the framework of cognitive radar and promising interfer-ence mitigation techniques are reviewed. Index Terms—cognitive radar, adaptive waveform, target de-tection, waveform design, anti-interference

This session celebrates the technical impact of women in the microwave engineering field, with special emphasis on their contributions to leading edge defense technologies in the United States.

University defense funding has over the years produced a number of innovations in components for communications and sensing related to national defense needs. This paper presents an overview of research centered around improvements of microwave and millimeter-wave transceivers and the potential impact of fundamental research on future military systems. For example, development of low-loss broadband passives implemented in new technologies such as micro-fabricated air coaxial transmission lines, results in improvements in power combining, filtering, noise and efficiency.

A stability analysis of a non-Foster matching network is presented. The investigation is carried out at two levels: considering an ideal implementation of the negative impedance inverter (NIC) and using detailed circuit-level descritions of all its active and passive components. The ideal NIC model will enable an analytical derivation of the characteristic system and the system poles, which will provide insight into the main instability mechanisms in these configurations. A good qualitative agreement is obtained with the circuit-level analyses, based on pole-zero identification and bifurcation detection methods. The impact of significant parameters, such as the biasing resistors or the value of the reactive component to be negated, is investigated in detail. A circuit-level methodology is proposed to obtain the stability boundaries and margins in an efficient and rigorous manner. For illustration, a non-Foster circuit based on a NIC has been manufactured and measured, obtaining very good agreement with the results.

Non-Foster networks are those whose reactance has a negative slope with frequency, and can thus overcome bandwidth limitations of many passive systems. The design parameters of a negative impedance convertor circuit (circuit configuration, transistor bias) used to generate non-Foster impedances will depend on the load impedance at the output of the non-Foster circuit, the frequencies of operation and requirements pertaining to a specific application (such as low noise or high linearity). Insights into the design, simulation, implementation and stability analysis of non-Foster circuits will be presented through measured results of a non-Foster matched cylindrical slot antenna. Simulation techniques that can accurately predict measurements will also be detailed. Further, noise and linearity measurements that match simulations will be shown for the same non-Foster matched antenna. A discussion of the trade-offs between bandwidth, loss, stability, noise and linearity of a non-Foster circuit will be helpful in optimizing non-Foster circuits for specific applications.

The paper presents results of a comparative study of a loop electrically-small antenna (ESA) matching with non-Foster negative inductances. Two matching networks which differ in connection of the non-Foster element to the antenna are considered. In one case the negative inductance is connected to the antenna input whereas another case correspond to the antenna with the negative inductance connected in the middle of the loop symmetrically with respect to the antenna arms. Influence of the matching network architecture on the loop ESA performance is investigated. The second approach is shown beneficial with regard to providing of proper feeding of the loop antenna which results in a symmetrical radiation pattern.

This paper adopts normalized determined function (NDF) to analyze the stability of a non-Foster matched antenna. A -40 pF negative capacitor is achieved at high frequency (HF). The neg-ative capacitor is connected to the input of a 2-meter height helical antenna for wideband cancellation of the large input reactance of the antenna at HF. Nyquist plots of NDFs are used to evaluate the stability of the non-Foster system with and with-out the stabilization resistor. The performance of input match-ing and efficiency improvement by non-Foster matching circuit is measured. The received signal power level can be increased by 20-30 dB from 3 to 13 MHz compared to without matching case, and about 15 dB improvement compared to a commercial well-matched HF antenna.

(submitted for the "Advances in Microwave Systems for Deep-Space Missions" focus/special session) This paper reports on an internal study carried out at the European Space Agency (ESA) for assessing the reference performance of Payload Data Transmitters achieved in the mid-term. This assessment is meant to provide input to the ESA roadmaps for the 2023 time frame. The assessment is carried out for various space missions, from low Earth to deep space orbits. Taking advantage of technology evolution combined with innovative architectures and advanced digital signal processing, the paper shows how the data return in several space missions can be dramatically increased by reasonably extrapolating existing RF technology.

(Submitted for "Advances in Microwave Systems for Deep-Space Missions" Focus Session) Deep-space missions present unique demands on spacecraft components. These include typically stringent size, weight, and power specifications, and designs must also often adhere to strict requirements for radiation, long mission life, and reliability. For flight RF/microwave systems, this translates in particular to design constraints on antennas, radios, and power amplifiers and how these systems are operated. This paper re- views recent accomplishments in RF/microwave system design on United States deep-space missions, and looks ahead to systems in development for upcoming missions.

(Submitted for the "Advances in Microwaves Systems for Deep-Space Missions" focus/special session) The telecommunications systems for two NASA deep-space missions to Europa are presented. One mission, Europa Clipper, is a Jovian orbiter with multiple Europa flybys. The Europa Lander mission includes a carrier spacecraft and landed element. Both missions are designed to communicate to Earth via the NASA Deep Space Network and other ground stations. For lander communications, both the carrier spacecraft and Europa Clipper spacecraft are equipped with store-and-forward relay communication capability. The heart of each spacecraft’s telecommunications system is the high-TRL JHU/APL Frontier Radio, based on the Solar Probe Plus design. Other key hardware developments across the different spacecraft include a 3-m dual-band (X/Ka) high gain antenna (HGA), a GaN-based solid state power amplifier and a slot-array HGA to enable the lander communication system. All components must operate in a high-radiation environment and meet planetary protection requirements.

In meeting the needs of a number of different missions, [redacted] has produced a family of high-reliability, extremely low size, weight, and power (SWaP) software-defined radio (SDR) products for near and deep space applications called Frontier Radio (FR). With flight heritage on multiple successful missions, the latest flight version includes a Ka-band downlink. Frontier Radio has also branched to include Frontier Radio Lite (FR Lite), a single-board radio with significant SWaP savings, and the Frontier Radio Virtual Radio (VR) with the capability to replace the processing functionality of an entire spacecraft bus for smallsat, microsat, and cubesat applications. All FR products are designed for agile adaptability through the use of modular architecture in hardware, firmware, and software to meet the varying needs across many missions.

This paper describes a unique, multi-channel synthetic aperture radar (MCSAR) designed for maritime remote sensing and surveillance. The X-band system supports two simultaneous transmit channels, excited by arbitrary waveforms, and four simultaneous receive channels, thereby allowing full multiple-input-multiple-output (MIMO) modes. The system antennas are readily reconfigurable to support both along-track and cross-track phase center displacements as well as polarimetric operation. In addition, receive switching is available to provide as many as 32 along-track phase centers. This paper describes the hardware and presents results that illustrate how the along-track phase centers can be used to provide detailed motion measurements across dynamic maritime scenes, using either the Velocity SAR algorithm or a new multi-channel interferometric approach. Imagery recently collected using a combined along-track/cross-track MIMO mode is also presented. The simultaneous velocity and height information provided by this configuration offers new approaches to ocean remote sensing.

Developments in communications and networking have enabled separate microwave wireless systems to coordinate at increasingly detailed levels, creating a path towards distributed wireless systems. Coherent distributed arrays, where the individual wireless systems synchronize at the level of the RF carrier phase, achieve transmit power gains on the order of the number of platforms squared, and receive gains proportional to the number of platforms. For radar applications, an array with N elements yields an overall system gain of N^3, providing a significant improvement in radar sensitivity. This paper analyzes improved detection capabilities for surface maritime radars operating coherently, and discusses technologies for achieving coherent gain. Recently developed microwave wireless technologies for inter-node coordination in coherent distributed arrays are presented, and future challenges for coherent arrays of maritime radars are discussed.

All sensors including Synthetic Aperture Radar (SAR) capture vast amounts of critical knowledge that is often contained within raw and processed sensor data, yet is undetectable, obscured or never presented. Through the application of emergence algorithms, patterns, relationships and events that are hidden or hard to find within the data are revealed in rapid to near-real time speeds. Emergence algorithms originally developed to reveal hidden diseases, are extending the capability of SAR sensors to see in effect “below” the ocean surface, revealing hidden signatures of boats, submersibles, aircraft and missiles, and often revealing things no-one expected to discover. After a brief review of SAR theory and representative image products, examples of signatures “hidden” within these SAR images will be presented.

This paper presents a summary of operational ship detection using RADARSAT-2 imagery, but focuses on the investigation of several approaches to the challenging problem of ship detection in the presence of sea ice using knowledge-based target discrimination methods. Ship detection performance was evaluated using Automatic Identification Systems (AIS) data.

Offshore wind turbines (WT) can cause wrong estimation of radial speed of nautical traffic by marine radar. The error in measured radial speed due to rotor forward scattering is investigated for S band radar using Fresnel-Kirchhoff diffraction approach. Based on the insight into Fresnel zone shading a scenario with high impact of rotor forward scattering on the Doppler error is selected. Deviation of instantaneous Doppler frequency as well as time-frequency spectrum of the modulation signal within the interval of time on target is investigated.

VNA measurement of scattering parameters in the frequency domain is common practice, and time domain analysis can find the impulse and/or step responses of the DUT. A problem with this is the introduction of unwanted side lobes that are caused when applying band-limited Fourier Transform. One technique to reduce side lobes is windowing, but this has a broadening effect on the main-lobe. The Spatially Variant Apodization and superimposition (SI) techniques have been seen to address these issues in the past. In this paper an enhancement to the SI technique through a normalisation process is investigated. The NSI technique is seen to preserve the position, amplitude and phase of the main lobe responses from a DUT in both simulated and measured data, reducing side lobes and confusion in the time domain representation of the DUT. Hence a better approximation to the ideal impulse response is achieved.

This paper presents a single-chip 0.01–26 GHz reflectometer for two-port VNAs. The reflectometer consists of a bridge coupler integrated with two heterodyne receivers. For wideband operation, a resistive bridge coupler is used with a directivity of 33 dB. Also, a high-linearity receiver is designed so as to accommodate 10 dBm RF input power to the reflectometer. The SiGe chip is 1.8 mm2 and consumes 640 mW. The dynamic range of the chip is 127+-±2dB with an IF RBW of 10 Hz. Measurements of several DUTs with a 0.01-26GHz VNA shows excellent agreement with a commercial VNA. Two-port measurements also show an S21 dynamic range of 80 dB, limited by the measurement setup. To our best knowledge, this is the first demonstration of a VNA operating from 10 MHz to mm-wave frequencies with the capability of measuring -80 dB of S21 as well as minimal magnitude and phase difference.

Current waveguide flanges do not allow for accurate fitting of Silicon microchips, due to the mechanical tolerances of the flange alignment pins and the brittle nature of Silicon, requiring oversized chip alignment holes to fit the worst-case tolerances, resulting in significant misalignment error for sub-THz frequencies. This paper presents, for the first time, a new method for aligning micromachined chips to standard flanges with accuracy better than the flange tolerances, by combining a circular and an elliptical alignment hole on the chip. Monte Carlo analysis predicts the reduction of the mechanical assembly margin by a factor of 7, reducing the potential misalignment from 46 to 8.5 µm for a probability of fitting of 99.5%. Micromachined chips using either circular or elliptical alignment holes were fabricated and measured. A reduction in the standard deviation of the reflection coefficient by a factor of up to 20 was observed from 200 random measurements.

The calibration of a microfluidic microwave sensor is a challenging field of research. While most of the existing strategies still rely on information out of full wave simulations, this work demonstrates an exact method to calibrate such a sensor with only three transmission measurements of known liquids. In this way, a closed formulation that directly maps S-parameters to the complex permittivity value of the material under test was found. Because this calibration scheme is based only on transmission measurements it has potentially lower requirements concerning the hardware implementation of a sensor. The theory is validated with measurements of different aqueous NaCl solutions as well as albumin solutions up to a frequency of 10 GHz. It is demonstrated, that due to the accurate data extraction small differences of 0,05 mol/l can be discriminated very well. This corresponds to a change in permittivity of 0.6% while the error is in average 0.15%.

This paper proposes a non-contact PIM-measurement method for dielectric wave absorbers. It is shown experimentally that the PIM characteristics of a dielectric wave absorber can be measured in an open-ended coaxial tube by mounting a metallic resonator on the tested sample. An experimental result using a small piece of absorber is also presented to show that the PIM produced by dielectric absorbers is based on the electric-mode.

Nathan O. Sokal is best known for introducing the class-E high-efficiency power amplifier to our RF/microwave community. This presentation recalls a bit of his history, as well as my recollections of interactions with him in developing power amplifiers. At the end of the presentation, the audience will be invited to add their own recollections.

Memorial session for Nat Sokal: This paper covers the early history of Class-E techniques up to the mid-1970s, beginning from some experimental results with detuned resonant circuits obtained in the late 1940s and early 1950s and illustrates some examples of theoretical design approaches and different circuit implementations of the high-efficiency vacuum-tube and transistor power amplifiers operating in Class-E mode using load networks with lumped elements

Class E amplifiers have been used in a very broad frequency range. This paper expose a general review of the basic application of class E amplifiers for lower frequencies (MF, HF, VHF), including typical components, applications, and results. The paper is oriented to the special session in memory of Nathan O. Sokal.

This paper reviews circuit architectures and demonstrated class-E power amplifiers in the UHF and microwave frequency range. Scaling class-E soft-switching operation to high frequencies presents a number of challenges, particularly in the control of parasitic reactances of the device and the circuit. Different approaches have been taken, from using parasitics of lumped elements to provide the correct fundamental and harmonic impedances in the UHF range, to transmission-line implementations at frequencies above 10GHz.

This paper reviews the use of the Class-E topology for RF-to-DC and DC-to-DC power conversion. After covering its early history, the Class-E rectifier is introduced in the context of the time-reversal duality principle, to be then integrated with an inverter in the Class-E2 DC/DC converter. Recent examples of rectifier and power converter implementations at UHF and microwave bands are finally presented.

This paper presents a novel and efficient system for tracking of passive ultra high frequency (UHF) radio frequency identification (RFID) tags based on the phase difference of arrival technique. All required information for a tag position update is captured within only one communication cycle between a UHF RFID reader and a tag. The system provides two dimensional position updates that allows the tracking of a tag on arbitrary tracks. The current tag position is calculated analytically based on a specific bistatic reader antenna arrangement. Initial verification measurements in a realistic application environment show mean absolute errors of 8.4 cm and 1.3 cm for the x-coordinate and the y-coordinate, respectively.

A novel zero-power wireless crack sensor based on the harmonic radar principle is presented. The tag, fabricated on a paper substrate by means of the copper tape technology, is targeted for a fundamental frequency f0=2.45 GHz (ISM band) and consists of a system of two nested annular slots, a frequency doubler and a stub behaving as a band-stop filter. In presence of a crack the stub, placed a the input of the doubler, is torn off and an alarm is sent to the receiver. Such a system is suitable for scenarios involving a massively distributed population of cracked wall sensors, where it is of interest to detect any crack increase. A wireless experiment demonstrates an operating range of the sensor from 1 to 5 m for a transmitted power EIRP of 25 dBm.

Nowadays the measurement of moisture level in plants is critical for agriculture. One way to detect this is to measure the temperature difference between the leaf and the air. This paper introduces a novel wireless leaf temperature sensor that utilizes ambient FM backscattering for smart agricultural applications. The sensor is based on an ultra low power micro-controller, a sensor board and a RF front-end for wireless communication. The sensor communicates using backscatter radio principles on ambient FM station signals using FM0 modulation. The prototype featured an effective operation up to ranges of 0.5 m by backscattering sensor information at 50 bps and 500 bps using an ambient FM radio signal inside a laboratory setup. A high percentage of bits was clearly visible up to 2 m at 50 bps.

This work describes the design of an energy efficient transmitter for wireless power transfer applications. The main objective is to power up, efficiently, an IoT sensor moving on a multipath environment. In this scenario a flexible transmitter will be operated in order to maintain a constant power delivery to the sensor, while maximizing both transmitter and receiver energy efficiency conversions. The mechanism operates on the basis of a backscatter circuit attached to the IoT sensor, creating a feedback link that feeds the transmitter with its Received Signal Strength (RSSI). Experimental results will be reported on a system working at 5.83 GHz for wireless power transfer and 3.45 GHz for the backscattering link.

A UHF energy harvesting unit, also comprising UWB communication function, is integrated in a low-profile, compact, unique device. The optimized collocation of two couples of dual linearly-polarized dipoles provides all-polarization receiving capability and a quasi-isotropic radiation, momentous features for RF energy harvesting applications. Activation distance of a commercial ultra-low power management unit is enhanced with respect to a corresponding single-rectenna case. The EM-based non-linear simulation of the entire system has shown its ability to rectify RF power incident from any direction, with activation distances always higher than 14.7 meters for any direction of arrival and up to 26 meters in the best-case condition. Implementation of the presented RF harvester is currently under development to verify real outdoor and indoor performance.