High efficiency microwave rectenna circuit: modelling and design

An equivalent circuit approach used for the modelling of a system consisting of an antenna and an RF/DC rectifying circuit (rectenna) is presented. It is shown that using this approach, no electromagnetic simulation tool is required for the simulation and optimisation of the overall circuit. The realised rectenna operates at 2.45 GHz, and shows very good agreement between the predicted efficiency using the presented model (about 75%) and the measured one.     

Thermosonic Wire Bonding Process Simulation and Bond Pad Over Active Stress Analysis

In this paper, a transient nonlinear dynamic finite element framework is developed, which integrates the wire bonding process and the silicon devices under bond pad. Two major areas are addressed: one is the impact of assembly 1st wire bonding process and another one is the impact of device layout below the bond pad. Simulation includes the ultrasonic transient dynamic bonding process and the stress wave transferred to bond pad device and silicon in the 1st bond. The Pierce strain rate dependent model is introduced to model the impact stain hardening effect. Ultrasonic amplitude and frequency are studied and discussed for the bonding process. In addition, different layouts of device metallization under bond pad are analyzed and discussed for the efforts to reduce the dynamic impact response of the bond pad over active design. Modeling discloses the stress and deformation impacts to both wire bonding and pad below device with strain rate, different ultrasonic amplitudes and frequencies, different friction coefficients, as well as different bond pad thickness and device layout under pad. The residual stress, after cooling down to a lower temperature, is discussed for the impact of substrate temperature.     

Measurement and analysis of miniature multilayer patch antenna

Although the microstrip patch antenna has a number of advantages such as low-cost and light weight, its physical size is quite large at low microwave frequencies. The designs of multilayer miniature patch antennas with coaxial feed are presented. The first design is a rectangular two-layer patch antenna. Measured results and the results of a preliminary analysis are presented. The projection area of the two-layer patch antenna is kept the same as the single-layer rectangular patch antenna. The resonant frequency of the two-layer antenna is reduced by 50% and has bandwidth of 5%, which is wider than the single-layer rectangular patch antenna. In the second design, the upper patch is cut into a bow-tie shape. This results in a 60% reduction in resonant frequency and a 12% bandwidth. Both the two-layer rectangular and the two-layer bow-tie antennas have good radiation patterns, with cross-polarization level lower than the copolarization level by more than 20 dB     

Development and investigation of real-time robust algorithms for estimating the parameters of geometric transformations of video-sequence frames

The problem of estimating the parameters of geometric transformations of the frames in a video sequence is considered. The solution to this problem is found through a combination of three basic approaches: the optical-flow feature-point methods and the direct correlation methods. A procedure for the detailed analysis of the behavior of the correlation function is used to ensure stable real-time operation of the proposed algorithms on modern (even unspecialized) computing systems for a wide range of shooting conditions.     

SAKE: Software attestation for key establishment in sensor networks

This paper presents a protocol called Software Attestation for Key Establishment (SAKE), for establishing a shared key between any two neighboring nodes of a sensor network. SAKE guarantees the secrecy and authenticity of the key that is established, without requiring any prior authentic or secret cryptographic information in either node. In other words, the attacker can read and modify the entire memory contents of both nodes before SAKE executes. Further, to the best of our knowledge, SAKE is the only protocol that can perform key re-establishment after sensor nodes are compromised, because the presence of the attacker’s code in the memory of either protocol participant does not compromise the security of SAKE. Also, the attacker can perform any active or passive attack using an arbitrary number of malicious, colluding nodes. SAKE does not require any hardware modification to the sensor nodes, human mediation, or secure side channels. However, we do assume the setting of a computationally-limited attacker that does not introduce its own computationally-powerful nodes into the sensor network.SAKE is based on Indisputable Code Execution (ICE), a primitive we introduce in previous work to dynamically establish a trusted execution environment on a remote, untrusted sensor node.     

Dual-polarized dielectric resonator antennas

Two high input-isolation dual-polarized dielectric resonator (DR) antennas are presented in this communication. First, a slot-coupled feed technique with two narrow slots forming a "T" configuration is employed to design a dual-polarized DR antenna. Input isolation exceeding 35 dB has been obtained in the band for this design. Secondly, a hybrid feed mechanism with a coplanar waveguide (CPW) feed and a slot feed is used to achieve a dual-polarized DR antenna. A vertical strip is added at the center strip of the CPW feed to improve the coupling to the DR antenna. Also, input isolation exceeding 35 dB has been obtained in the band. Good cross-polarization levels less than -20 dB in the broadside direction are attained. The measured far-field radiation patterns are stable in the passband and the measured gains are around 5.5 dBi for the two feed ports of both cases.     

Minimum-value distribution of random electromagnetic fields for modeling deep fading in wireless communications

In this work, we presented a theoretical investigation of the minimum-value distribution inside complex electromagnetic environments. In particular, a statistical model for characterizing the minimum value of the complex-value field or power inside a dynamic mode-tuned or mode-stirred reverberation chamber is presented and discussed. Such an EM environment serves as an emulator of multipath radiowave propagation for indoor/outdoor wireless communication channels. It is found that, for both overmoded and undermoded regimes, the generalized extreme value distribution leads to the reverse Fréchet and Weibull types for complex-value (Cartesian and total) fields and for the total energy (or intensity). These distributions are stable and follow from the convergent behavior of the lower tail for their corresponding parent distribution of the Cartesian field magnitude, namely a χ ². On the other hand, received power exhibits a Pareto-type distribution because of the unbounded left tail of the negative exponential parent distribution.     

A wideband low noise amplifiers design incorporating the CMRC circuitry

An impedance bandwidth enhancement technique for tuning a low noise amplifier (LNA) is presented. With the use of the compact microstrip resonant cell (CMRC) at the emitter pins of a bipolar junction transistor (BJT), the impedance bandwidth achieved is about 95%, for a simple single stage amplifier design. The LNA attains a gain of about 15 dB; also a low noise figure of 1.16 dB at 2.1GHz and an average noise figure of about 1.5 dB across the operation bands have been achieved.     

Broadband,High‐Speed,and Large‐Amplitude Dynamic Optical Switching with Yttrium‐Doped Cadmium Oxide

Transparent conducting oxides, such as doped indium oxide, zinc oxide, and cadmium oxide (CdO), have recently attracted attention as tailorable materials for applications in nanophotonic and plasmonic devices such as low‐loss modulators and all‐optical switches due to their tunable optical properties, fast optical response, and low losses. In this work, optically induced extraordinarily large reflection changes (up to 135%) are demonstrated in bulk CdO films in the mid‐infrared wavelength range close to the epsilon near zero (ENZ) point. To develop a better understanding of how doping level affects the static and dynamic optical properties of CdO, the evolution of the optical properties with yttrium (Y) doping is investigated. An increase in the metallicity and a blueshift of the ENZ point with increasing Y‐concentrations is observed. Broadband all‐optical switching from near‐infrared to mid‐infrared wavelengths is demonstrated. The major photoexcited carrier relaxation mechanisms in CdO are identified and it is shown that the relaxation times can be significantly reduced by increasing the dopant concentration in the film. This work could pave the way to practical dynamic and passive optical and plasmonic devices with doped CdO spanning wavelengths from the ultraviolet to the mid‐infrared region.     

Algorithm of Robust Frequency Estimation in a Channel with White Gaussian Noise and Pulse Interferences

An algorithm for robust frequency estimation in a channel with additive white Gaussian noise and pulse interference is proposed. The algorithm involves iterative elimination of pulse interferences and subsequent calculation of the maximum likelihood estimate. It is demonstrated that the proposed filter-cleaner differs from the well-known Martin–Thomson filter in the functional dependence of adaptive coefficients on the estimates of parameters of distributions of the linear prediction error and the amplitude envelope of the signal. The results of mathematical modeling and numerical estimation of the threshold point of the method (0.49) are presented.